Thursday, 31 December 2009

Butterflies of Bristol 12: How does it work?

Butterfly houses are becoming increasingly popular all over the world, and can have a significant economic effect in the source countries for those involved on the butterfly farms, so I thought it would be a good idea to end this series, and the year, with some facts and opinions of my own about them.

The reason for their popularity is not hard to find – butterflies are beautiful, harmless (although I have seen a few people jump when a Morpho or Owl butterfly lands on them!) and comparatively easy to maintain. Basically any enclosed space can be used to house butterflies (our Butterfly House is basically a poly tunnel), provided that the internal environment is kept within the correct parameters. For tropical butterflies, this is an air temperature with a minimum of 25 degrees Celsius during the day, preferably higher, and a night temperature of at least 15. Humidity is the other important variable – for butterflies from rainforest areas it should be a minimum of 70%. Low humidity results in poor emergence, damaged wings, and shortened lifespans. Some butterflies will still fly in low light levels, especially Glasswings and Owl butterflies, but most need maximum illumination. Our butterfly house has supplementary lighting which extends the photoperiod in the winter months.

Monday, 28 December 2009

Butterflies of Bristol 11: Some new arrivals

For all those readers who are busy recovering from Christmas (you know the score – disposing of the wrapping paper, finishing up leftovers, hiding the bodies…) there are some new species just arrived from our Costa Rica supplier that can be found in the Butterfly House. Here are some brief notes on what to look for:

Tithorea tarricina. The Tigerwing

Tithorea is a nymphalid butterfly belonging to the Ithomiini, the same group as the clearwing butterflies that breed in the house. Unlike them, it is warningly coloured, from which the common name Tiger Wing butterfly is derived. Like many of their relatives, the larva feeds on members of the milkweed family Apocynaceae, with Echites and Mandevilla being reported as larval hosts, although over its vast range in Central America it probably uses several others. One odd feature is that the males are strongly attracted to bird droppings, sometimes visiting the same one several days in a row. It is believed they derived compounds from them which they use to produce pheromones used in courtship, and possibly transfer to the females to help produce healthy and viable eggs.

Wednesday, 23 December 2009

Butterflies of Bristol 10: Also showing

Look under the leaves of the plants as you enter the Bristol Zoo butterfly house and you may see a small, whitish snail clinging to them. These are not just any snail – they are some of the last of their kind. In fact, they come from Moorea in the Pacific, and rejoice (?) in the name Partula tohiveana.

The last fifty years or so have been a disaster for a huge number of the endemic snails of the Pacific islands. As is usual in these circumstances, human beings are to blame, in this case initially by at first deliberately, and then accidentally, spreading the Giant African snail Achatina Fulica (these will be found in many pet shops in the UK these days – and even more jam jars at school).

Saturday, 19 December 2009

Butterflies of Bristol 9: Not exactly a butterfly

Not butterflies of course, but among the most spectacular of the Lepidoptera, two silkmoths (family Saturniidae) are regularly on show here at Bristol. The most spectacular, and one of the largest of all insects, is the Giant Atlas Moth, Attacus atlas. We currently have some adults on show, but unfortunately the adult phase of the life cycle does not last long – 7 to 10 days at the most. This is because, unlike butterflies, silkmoths do not feed as adults – their mouthparts are non-functional and they instead rely on the fat reserves they built up as larvae.

Silkmoths get their name because they are related, although not as closely as once thought, to the true silkworm Bombyx mori. Now split into a separate family Bombycidae, the silkworm is probably the most economically (and in history politically) important insect in the world. The silkmoths produce a coarser grade of silk than the silkworm, but many species have been used for commercial silk production nonetheless, especially in India.

Saturday, 12 December 2009

Butterflies of Bristol 8: The Swallowtails

One of the most popular groups of butterflies to be seen in butterfly houses worldwide is the swallowtails (Papilionidae). Mostly medium sized to large butterflies (the Queen Alexandra’s Birdwing, Ornithoptera alexandrae is the largest of all butterflies, with a 30cm wingspan), they are also strong fliers and so make a good display. They are not usually true migrants, but they can stray long distances sometimes.

Swallowtails are grouped together by a distinctive feature of the larva, called the osmaterium. This is a forked structure that can be extended from the thorax of the larva and has a deterrent scent. The larva when disturbed will produce this and flail about to deter potential insect predators – although the frequency with which they are parasitized suggests this is not a very effective technique.

Monday, 7 December 2009

Butterflies of Bristol 7: The Whites and Yellows

Most of the butterflies with a mainly white or yellow background colour to the wings that you will see in Europe belong to the vast and widespread family of butterflies called the Pieridae. Examples that British people will be familiar with are the Large and Small Cabbage Whites, the Brimstone, and the several species of Clouded Yellows. Note that the Marbled White however is a nymphalid, and is related to the various Brown butterflies.

Pierid butterflies feed on a wide variety of food plants, but a large proportion of the European species feed as caterpillars on members of the Cruciferae (the mustard or cabbage family). The Clouded Yellows however are associated with members of the Leguminosae, especially Lucerne(alfalfa in the US).

Saturday, 28 November 2009

Butterflies of Bristol 6: The Egg Fly butterflies

The egg fly butterflies of the genus Hypolimnas are a diverse group of nympalids with a worldwide distribution. We have at various times four species at Bristol, of which the two you are most likely to see are the Variable Eggfly H.anthedon, and the Red-Spot Diadem, H.usambara. You may also see the Great eggfly H.bolina and the Mimic Eggfly H.misippus.

Saturday, 21 November 2009

Butterflies of Bristol 5: The Charaxes

Moving on from South American butterflies to those from Africa, one of the more obvious nymphalids on show are the various species of Charaxes. This is a huge group of species, with a collective range extending across the Old World tropics. A single species, C.jasius, breeds around the Mediterranean, and I have seen these on several occasions. The best time is probably late summer, and the best location is a fig grove – the Charaxes butterflies are feeders on fruit and dung rather than flowers. Charaxes butterflies often have intricately marked or cryptic undersides to their wings. Upper sides may be marked in shades of orange or brown for the most part. At the zoo we usually have three species:

Monday, 16 November 2009

Butterflies of Bristol 4: The Morphos

The most spectacular and instantly recognizable butterflies we have at Bristol are the Common Morpho butterflies, Morpho peleides. Like the owl butterflies, to which they are fairly closely related, they belong to the Satyrinae, the same nymphalid subfamily that includes the familiar brown butterflies of Europe. Currently the Morpho tribe is divided into three genera:

Antirrhea – 11 species
Caerois – 2 species (leaf mimics)
Morpho – 29 species in several subgenera

Sunday, 8 November 2009

Butterflies of Bristol 3: The Glasswings

At this time of year the most prominent butterflies to be seen in the butterfly house are the clearwing butterflies. These butterflies (we have the Frosted Glasswing Greta oto) belong to the Ithomiini, a subdivision of the milkweed butterflies Danainae, which in turn belongs to the gigantic family Nymphalidae. Butterflies of this group are often distasteful to predators as they sequester toxic alkaloids from the larval foodplants, which mainly in the case of the Ithomiines are members of the nightshade family Solanaceae. Some however do not depend on the larvae as a source of toxins; instead the adults obtain alkaloids from flowers or rotting leaves. This is especially the case with the males, which also use the toxins as pheromones in their courtship of females.

Tuesday, 3 November 2009

Butterflies of Bristol 2: The Heliconiines

One of the most obvious groups of butterflies to be seen in butterfly houses around the world are the various species of the Nymphalid tribe Heliconiini. This is an almost entirely Central and South American group of 69 species and innumerable local colour forms, characterised by a strong preference for members of the Passifloraceae as larval food plants. Passiflora contains some potent toxins, which are taken up by the larvae and render the adults distasteful to predators, especially birds. As a result, they tend to be confident and vigorous flyers, usually with warning colours of red, black and yellow in a variety of patterns, which makes them very obvious when in a butterfly house.

Monday, 26 October 2009

Butterflies of Bristol 1: The Pale Owl Butterfly

The Owl butterflies are a group of about twenty very large South American butterflies, often seen in butterfly houses as they are spectacular and easy to raise on butterfly farms. Here at Bristol we have the Pale Owl butterfly, Caligo memnon.
The various species of Caligo belong to the gigantic and diverse family the Nymphalidae, and in particular to the very large subfamily (previously a full family) Satyrinae. As such they are most closely related to the multitude of “Brown” butterflies found in every grassland on earth, but among their closest relatives are the vivid iridescent blue (and just as large) Morpho butterflies, which we also have at Bristol. Also closely related are the somewhat smaller Opsiphanes species of North America.

Saturday, 17 October 2009

Colourful, endangered - and in Bristol

The Gouldian, or Lady Gould’s, finch Erythrura gouldiae is one of the most beautiful small finches in the world. Sadly, the species is highly threatened in the wild, and the wild population is estimated at only a few thousand birds in the Northern Territories of Australia.

Until as recently as the 1980’s, Gouldian finches were still found in large numbers, but the impact of increased grazing, and probably even more important a shift in the fire management system, has resulted in a collapse of the population. Hot, late season fires over large areas deprive the birds of their favourite grass seeds, which is the staple diet. There are habitat restoration projects underway, but time is short for these birds. Small birds tend to have short lifespans, and numbers even at the remaining sites can vary considerably from year to year. An experimental release of birds in Queensland has appeared to have at least some success, with released birds breeding in the wild.

Gouldian finches are unusual birds in that they have three colour morph’s, the Red-, Yellow- and Black-headed forms. These are correlated with different behaviour patterns and feeding and breeding strategies as follows:

Red-headed: These birds dominate at feeders in captivity, and appear to displace other morph’s at nest sites. They are often polygamous, which together suggests they should form the majority, but in fact they are much less common than the black-headed morph. It appears they are more susceptible to stress, and have higher mortality as a result.

Black-headed: These are subordinate to Red-headed birds but dominate Yellow-heads. They have a monogamous breeding strategy, and form the bulk of the wild population

Yellow-headed: These are at the bottom of the pecking order, and are very rare in the wild. In captivity they appear the most curious, and are usually the first to locate new food sources.

Gouldian finches nest in holes, laying a small clutch of eggs and raising young on unripe seeds and insects. Another cause of their decline is a lack of nesting sites –they avoid burnt trees even if they have suitable holes in them.

As with many Australian finches, the Gouldian finch has been domesticated, and is now kept all over the world. Members of Severn Counties Foreign & British Bird Society, to which I belong, breed well into double figures every year, and they are now not especially hard to breed. If you wish to seem them therefore, you do not need to visit Australia. SCF&BBS has our Open Show this Saturday 24th October (open to the public from 2.30), so if you are interested in these birds or aviculture in general please drop by. The show is at the Methodist church hall, Down road, Winterbourne, Bristol BS36 1BN. See our website for more details.

Finally, here are some other birds that members keep and will be exhibiting at the show:

Friday, 9 October 2009

October Research Colloqium - the importance of lighting

Wednesdays colloquium was a very interesting presentation from Rowena Killick BVM&S MSc (Wild Animal Health) MRCVS, who is the RCVS Trust senior clinical training scholar in zoo and exotic medicine and surgery here at Bristol Zoo Gardens, on a research project she carried out on the Vitamin D levels of some of the new world primates and lemurs here at Bristol.

Vitamin D is synthesised in the skin when it is exposed to UV light of the correct wavelengths from precursors in the diet, and then circulates in the blood to the kidneys where it is converted into the hormone 1,25-dihydroxyvitamin D3, which is a hormone that is involved in the regulation of calcium metabolism. There is a chemically related form called Vitamin D2, which does not have such a potent effect.

The primates of Central and South America (platyrrhines) have an odd biochemical quirk compared to those of the Old World. Their internal organs are resistant to the effects of Vitamin D3, and they cannot use Vitamin D2 at all. In order to maintain proper calcium metabolism, they have circulating blood levels of D3 which are ten to one hundred times higher than similar monkeys in Africa or Asia. Living as they do close to the equator, producing sufficient active D3 is of course no problem in their home range.

The potential problem we have is that Bristol is at mid latitudes in the northern hemisphere, whereas the two groups of primates mentioned earlier all live close to the equator. In humans, lack of exposure to sufficient ultraviolet light causes serious health problems such as rickets, and even sub-clinical levels of vitamin D deficiency can result in problems with fertility, disease resistance, or even potentially cancer. Our primates all have access to outside enclosures year round, so the question is, is this sufficient?

This past year as part of routine health checks the blood vitamin D3 levels of lemurs and new world primates were measured. Although levels of Vitamin D3 were within normal ranges for published data (in fact the lemurs were at the high end), the NWP’s were at the low end, especially in winter, and there was some indication of lower bone density than would be ideal.

So, what does this mean for the husbandry of New World Primates? At present, most zoo primates are given a primate pellet which has supplementary D3 added, as well as a variety of fruit and vegetables. At Jersey metabolic bone disease in Pied Tamarins was cured by providing UVB lighting, and indications are that this kind of lighting should become standard for New World Primates without access to tropical, or at least sub-tropical, sunlight in outdoor enclosures. This would be better than providing additional dietary supplements, as the risk of overdosing would be much lower – like most vitamins, excess Vitamin D is potentially seriously toxic.

The other requirement is of course more research. The various primates of the Americas are enormously diverse, and may have requirements for more or less D3 depending on the species. For example, the nocturnal Owl Monkeys or Dourocoulis, Aotus, have apparently no higher D3 levels than Old World primates. On the other hand, some South American species like the Uakaris are notoriously difficult to breed in zoos – could a higher Vitamin D/UVB requirement be the cause?

(Image from Wikipedia)

Monday, 5 October 2009

Land of the Dodo 16: Latest news

I will draw this series on the wildlife of Mauritius with some news from the Mauritian Wildlife Foundation, taken from their annual report and latest newsletter. Check out their website – and make a donation!

The MWF Solitude Endemic Nursery in Rodrigues produced 70,000 seedlings of 50 endemic species in 2008. These included 8 seedlings of Ramosmania rodriguesii, which was down to only a single remaining wild plant until cuttings were successfully propagated.

The Mauritius Fody has been downgraded from Critically Endangered to Endangered, as a result of the successful establishment of a population on Isle Aux Aigrettes. The mainland population now stands at 130 pairs, plus another 80 on isle Aux Aigrettes. Reintroduction to Round Island is planned for the near future.

Pink Pigeons exceeded 400 wild birds for the first time in February this year. Once the population reaches 600 the population can be downgraded from Endangered to Vulnerable status.

The recent nesting season for Echo Parakeets was very successful, with 112 young fledging; the population is estimated to exceed 400 birds.

There has appeared to be a decline in the population of Mauritius Kestrel, with a reduction in the smaller population on the east coast. The total population is around 600 birds.

Rodrigues Fody was reduced to only 6 pairs in 1968, but by 2007 had increased to 3,000 individuals,

Rodrigues Warbler was reduced to 17 individuals by 1982, but had increased to 1,000 by 2007.

After numerous nesting attempts, the first Mauritius Olive White-Eye from the introduced population on isle Aux Aigrettes fledged in October 2008.

The translocation of Telfair’s skinks to Isle Aux Aigrettes has proved a success. Not only has the skink bred outside of Round Island for the first time in 150 years, but several introduced pests such as House Shrews, Indian Wolf Snakes and FRICAN Land Snails have declined or died out altogether.

Aldabra Giant Tortoises and Radiated Tortoises were released on Round Island in 2007 as part of a PhD project to determine whether they can replace the extinct native tortoises.

Having recovered from a low of 100 individuals in the 1970’s, the population of Rodrigues Fruit bat now stands at over 5,000.

Finally, a captive breeding programme has been established on Jersey in the DWCT Herpetology department, with the aim of producing enough Lesser Night Geckos, Nactus coindemerensis, for an introduction to Ile Marianne.

PS - Reminder

The research colloquium at Bristol Zoo Education department is this Wednesday 7th October at 5.30. The subject is an investigation of Vitamin D levels in tropical primates at Bristol, and will hopefully provide useful information on the husbandry of these animals at high latitudes - is their enough sunlight for exposure outside to meet their requirements? The speaker is Rowena Killick (RCVS Trust Senior Clinical Training Scholar in Zoo Animal Medicine).

Monday, 28 September 2009

Land of the Dodo 15:Seabirds

When the Mascarenes were first discovered, the main islands did not have an extensive diversity of breeding seabirds, but offshore islets had some colonies of many species. These were often raided for eggs and young birds for food, and the burrow-nesting petrels are highly vulnerable to rats, which together have resulted in local extinctions of some species. A few of these have re-colonised naturally, but some others have been lost and world populations are now so low that it is unlikely that new colonies will be formed on the islands without outside help.

Currently only visitors to the islands are Greater and Lesser Frigate birds Fregatta sp., of which at least one species was reported as breeding when the islands were first discovered, Great Crested Terns Thallasseus bergii, and various Indian ocean gulls and terns, plus some Palaearctic migrant waders making stopovers, such as Ruddy Turnstones. Pelicans were reported offshore in 1598, probably Pink-backed Pelicans Pelecanus rufescens (which we have here at Bristol), which formerly bred in the Amirantes atolls north of Madagascar.

Three species of boobies formerly bred in the Mascarenes. One species just holds on, the Masked Booby Sula dactylatra, which breeds on Serpent Island. Red-footed Boobies Sula sula bred on Rodrigues until the 1870’s. The most important species however was the tree-nesting Abbott’s Booby, Papasula abottii (shown at top) which was probably both persecuted for food and also lost nesting habitat to deforestation. Abbott’s booby was ever only found on four stations, but today only a single breeding colony on Christmas Island remains, and this is too far away and too small to provide potential recolonists.

Several species of terns are found in the Mascarenes, some of which have recolonised after becoming locally extinct. The commonest are the Brown and Lesser Noddy, with Rodrigues also having colonies of Roseate Tern, Sooty, and Fairy Terns.

Two species of Tropicbird can be found on the islands, the inshore White-tailed Tropicbird and the more oceanic Red-Tailed Tropicbird, with the latter being the more common. They are increasing under protection and also benefiting from the recovery of the vegetation on Round Island and other seabird islets now that goats and rabbits have been removed.

The most important of the seabirds on the islands however are the various species of petrels. Petrels mostly breed in burrows, mostly only coming ashore after dark, so they are very hard to study. The Reunion Black Petrel Pseudobulweria aterrima appears to be a very rare breeder, and the breeding site was only recently located. Only once reported prior to the 19th century, it was probably always rare. It is part of a group of species which are otherwise found in the Pacific except for an extinct species from St Helena in the Atlantic. By contrast, the Wedge-Tailed and Tropical Shearwaters Puffinus sp. are both still fairly common, although Tropical Shearwater is extinct on Mauritius.

With the recovery of the vegetation in recent years, the situation on Round Island has become complex. Originally only a single species, the Round Island Petrel, believed to be a local form of the Trinidade Petrel Pterodroma arminjoniana, was known, but in recent years two other species have colonised, Bulwer’s Petrel Bulweria bulwerii, and Kermadec Petrel Pterodroma neglecta. The Kermadec Petrels sometimes hybridise with the Round Island Petrels, and it appears that a hybrid swarm of mixed parentage is forming. Both the Kermadec and Bulwers’ petrels appear to be new colonists of the western Indian Ocean.

This situation however is not unknown amongst seabirds, and sometimes islands are colonised from considerable distances away. One such colonisation probably resulted in the Reunion nesting Barau’s Petrel Pterodroma baraui. This appears to have been derived, however unlikely this seems, from the Hawaiian Petrel. Even more unlikely, these colonists seem to have brought with them on their feathers the seeds of a specialised shrub, Acacia koa, which itself has evolved into the Reunion endemic species Acacia heterophylla. On both Hawaii and Reunion the petrels and the acacia are closely associated, living at high altitudes on the slopes of the volcano.

Until recently, seabird conservation in the Mascarenes has involved only protection from persecution and habitat restoration, but attempts are just starting on direct reintroduction. One might wonder how this can be done, since seabirds all leave the breeding sites after fledging, usually for several years, but the secret is to take advantage of the tendency of fledglings to imprint on their birthplace, which in the case of petrels is whatever they see when first leaving the darkness of the burrow. In addition, many seabirds do not have post-fledging care – the chick, which at the point of fledging has a large amount of fat stored, makes its own way to the sea and teaches itself to fish. Currently being attempted are translocations of such fledglings to Isle Aux Aigrettes, with the hope that such birds will return to nest in later years. If these prove successful, possibly even Abbott’s Booby may be reintroduced at some time.

Images from Wikipedia from top:

Abotts Booby
Brown Noddy
White-Tailed Tropicbird
Wedge-Tailed Shearwater

Monday, 21 September 2009

Land of the Dodo 14: The other land birds

Aside from the land birds mentioned in previous posts, a further eight species of land birds are known from the Mascarenes, of which one is extinct. This was the Hoopoe Starling Fregilupus various, which became extinct in the mid-19th century. The cause of the extinction is unclear – it was apparently a generalist feeder and suitable habitat still appears to be available. Possibly deforestation and removal of trees with holes for nesting was the cause, but introduced disease must be a prime candidate. Island animals, because of their inevitably small populations, do not have as large a reservoir of disease resistance genes as continental populations, so they are permanently vulnerable to new diseases.

One of the only two surviving land birds on Rodrigues is the Rodrigues Warbler, Acrocephalus rodericanus. This is closely related to the Seychelles warbler, and belongs to a very successful genus of small insectivorous birds which combined have a gigantic range – at least 38 species are known of which two, the Reed and Sedge warblers, are common British birds and several others are know as either scarce breeding birds or regular vagrants to the UK. The Rodrigues warbler has had a good deal of protection and the population is currently at several hundred birds

Found only on Reunion is the Reunion Stonechat Saxicola tectes (shown below). Stonechats are another widespread group of birds, which have been recently split into several species. The Reunion stonechat is a fairly common species at higher elevations, where it frequents the cloud forest and giant heather heath land. It probably evolved from the Madagascar Stonechat S.axillaris, but stonechats are long-distance migrants so the founders could have come from further afield.

Found on Mauritius and Reunion are two species of Cuckoo-Shrikes (Coracina typica and C. newtoni). These feed in the canopy on large insects and lizards. Their origin is uncertain, but they resemble Cuckoo-Shrikes found in Australasia. (shown here, Black-faced Cuckoo-Shrike C.novaehollandiae)

Finally, there are three species shared between Mauritius and Reunion.

The Mascarene Swallow Phedina borbonica is also found on Madagascar, where it is partly migratory, so its presence on Mauritius is not hard to explain. The population on Mauritius at least is small, in the low hundreds at best.

The Mascarene Paradise Flycatcher Terpsiphone borbonnensis feeds low in the under story on small insects. It is very rare, but surprisingly on Mauritius it seems to be breeding successfully in forestry plantations.

Finally, least studied of all the remaining land birds is the Mascarene Cave Swiftlet Aerodramus francisus. Possibly derived from the Indian Cave Swiftlet, it suffers from the tendency of Mauritians to regard lava tunnels it requires for nesting as convenient sites for dumping rubbish. (All images from Wikipedia)

Monday, 14 September 2009

Is that lemur a couch potato?

A major problem for all animals kept in zoos is obesity. Even when recognised as such and correctly treated, animals with a history of obesity often have a poor reproductive record and many health problems, including arthritis, diabetes and coronary heart disease.

In addition, reproductive problems result from obesity such as infertility, overlarge infants resulting in problems giving birth, or larger than natural litter sizes. For example, wild Red Ruffed lemurs produce one offspring every other year, whereas in captivity they can produce triplets or even quads annually. As a result there is a moratorium in European zoos on breeding them, as there are too many closely related offspring about.

The purpose of this post is to explore the causes and possible remedies for this, and hopefully enable any visitors to zoos to think about the deeper issues of the welfare of captive animals beyond the more obvious concerns of the average zoo visitor, who is mostly concerned with the animal’s housing. I should add that these are my own opinions and do not necessarily reflect those of Bristol Zoo itself.

It has been said that almost all slimming advice can be boiled down to four words – “eat less, move more”, and this is also true for captive animals. I will cover the “move more” part on another post, in this one I would like to consider the effects of captive diets compared to wild diet.

1) Large carnivores

Large carnivores such as lions are adapted to a few large meals at unpredictable intervals, interspersed with periods of rest and strenuous hunting activity. Just as importantly, the food they eventually get is usually fairly low in fat and includes the internal organs and gut contents of their prey, which is a major source of their vitamins and other essential nutrients. Captive predators are usually given mostly muscle meat from cattle, horsemeat, or similar, and so they need additional vitamins – usually supplied as powder rubbed into the meat.

The ideal way to feed a lion or a leopard would probably be with a whole carcass, but this would obviously be messy to clear up and probably distress visitors or their children. We used to have leopards at Bristol, and gave them whole rabbits sometimes, but even this caused some adverse comments. Some zoos have constructed an artificial carcass out of fibreglass and put meat in that, but this limits the method of food presentation.

One variable zoos can use for feeding is not to feed at the same time every day. Most large carnivores have at least one “hunger day” per week – not always the same one – and are also fed different size meals at different times. The concept of “feeding time” is not usually followed at most zoos these days. In fact, you could probably get away with feeding a lion or tiger only once or twice per week if the meal was sizable enough, but the animals would then spend most of the week sleeping and be difficult to get to move from their outside to their inside quarters by offering titbits.

2) Large omnivores

The classic examples of these are bears. Here the problem is that a bear’s diet changes throughout the year depending on availability. In captivity by contrast, the diet is constant. This means that the animal’s physiology does not receive the correct cues for behavioural changes and so the activity patterns become unnatural. According to the September 2008 edition of International Zoo News, Ouwehands zoo in the Netherlands has recently implemented a seasonal diet plan for their polar bears, with the summer diet comprising nuts, berries, eggs and vegetables – to replicate the summer diet when polar bears subsist on what they can get on land before the sea ice returns -, and a winter diet of lamb, beef fat, fish and chicken. A similar seasonal regime has been used for some years for their brown bears, and as a result their brown bears now hibernate naturally.

3) Small carnivores and omnivores

Small carnivores are much easier to get to maintain activity levels. Most hunt daily, or even constantly, looking for insects of various sizes, small mammals, birds’ eggs etc. These a re fairly easy to replace in zoos, but the quantities need to be strictly controlled as they are not ranging over as wide an area and are consequently burning up less energy.

4) Large herbivores

Large herbivores are bulk feeders of vegetation, but here the issue is how much of this is supplied as fresh vegetation and how much as artificial diets. Historically, most large herbivores have been fed a diet which is a modified form of that given to domestic livestock. The problem here is that the diets of domestic animals are designed to maximise growth rates and fertility, not necessarily long life. Why should a farmer care that the diet he is feeding his beef cattle cuts their potential lifespan in half? – They will be sent for slaughter before two years of age anyway. This means that zoo herbivores usually need to be fed strictly limited quantities of pony nuts, stock feed and the like, even if they eat it readily.

The other problem is that hay given to zoo herbivores is often grass based. Given to a natural grazer like a zebra or an African elephant this is no problem, but given to an animal which naturally feeds by browsing on broad-leaved plants such as trees or shrubs this can result in unnatural patterns of tooth wear and poor digestion. For such animals alfalfa hay is far better.

Best of all however is fresh plant material. This comprises cut branches of shrubs or trees, fresh cut herbaceous fodder, and the like. Many zoos have “browse gardens” where they grow such food for their animals. Such food has to be carefully checked however - some plants can be toxic to some species but harnless to others.

5) Small herbivores

Most small herbivores select carefully the leaves and fruit they eat, which has resulted in them being termed “concentrate selectors” in ecological studies. The problem is that further research has shown that the plants they select are not that different in composition from those they avoid, and indeed many wild fruits have very little difference in nutrient and sugar content to foliage. What these selective browsers are probably choosing is not high nutrient content but low toxicity. Many plants, especially evergreen ones, protect themselves with a variety of distasteful or downright lethal compounds, and small herbivores have to be very careful in choosing what to eat.

In captivity, this has unfortunately resulted in many animals being fed cultivated fruits as a direct substitute for the wild diet. However, cultivated apples, bananas etc almost invariably have a far higher content of sugar and water, and a far lower content of protein and fibre, than wild fruits. As a result, there are a great many overweight primates (in particular) in the world’s zoos.

We have had here at Bristol several animals which had to be put on a diet. Our oldest female gorilla Salome was rather overweight when she first arrived (she is still portly) and has to be kept on a strict diet. Our male Mongoose lemur in our walk through became very obese by grabbing all the bananas in the daily meal, and has had to be kept on a calorie controlled diet. Lemurs are particularly prone to obesity, as they have a very low metabolic rate compared to other animals of similar size – up to 50% lower in some cases. Although now back to a wild weight, he has kept the “stretch marks” in the form of loose skin around his neck, which can be seen in the picture at top. You can meet him in the Lemur Walk Through, which he shares with a female and a family of Ring Tailed lemurs.

6) Reptiles

Obesity is particularly a problem with animals which spend long periods of time waiting for prey to come to them, and this covers in particular crocodilians and many snakes. People usually see a large python or boa remaining very still when they visit, but this is because their activity period is after dark. In the wild they would be quite wide ranging, and many species would be climbing extensively. The fairly limited space they are supplied with in most collections does not give the giant snakes much room for exercise, and in addition the domestic rodents which are their main food in captivity have a much higher fat content than wild rodents. The effect is that they turn into couch potatoes, and because people are used to thinking of them as fat they do not realise they are much wider bodied than they should be. Snakes store excess fat attached to their intestines, and as a result just about the commonest cause of ill-health in snakes is excessive fat causing damage to the internal organs.


To some up, here are some questions for any zoo visitor to ask themselves:

Is that animal overweight?
Is it being treated for obesity?
Is it being fed at times and in quantities that are similar to what it would get in the wild?
Is it fed a diet which changes seasonally?
What kind of hay is it getting?
How is the food presented? – In one or two meals or scattered so it has to spend the whole day searching for it?

Friday, 11 September 2009

Teenage Mutant enemy Turtles

Living in the lake here at Bristol Zoo we have a sizable number of Red-Eared Sliders, Trachemys scripta. They often sun themselves on the lake islands or can be seen swimming close to shore, where they may even come up and take food being offered to the ducks. These American terrapins are unfortunately found in many water bodies in Britain, especially in the south, although they can survive surprisingly low temperatures.

These are mostly a legacy of the Teenage Mutant Ninja Turtle craze of a few years ago, although I can recall hatchlings being sold in pet shops well before that took off. Ours are the result of rescue donations years ago. They are said not to be able to breed successfully in the UK, although that may not be entirely correct – our females lay eggs most years on the lake islands and we have found hatchlings on at least one occasion. However, in general our summers are not hot enough for long enough for the eggs to successfully incubate.

Terrapins are omnivorous animals, taking plant material, especially as adults, but also insect larvae, water snails, and scavenging, but they are also more than capable of catching fish or even sometimes ducklings. As a result they are a potential risk to wildlife wherever they are found. Of course, they have also been introduced in many parts of the world and are a potential threat to many other species of aquatic turtle, both through competition for food and also for basking and nesting sites.
What many people in the UK are unaware of however is that at one time we had our own native terrapin – the European Pond Terrapin Emys orbicularis. In the warm, dry spell after the end of the last ice age this rapidly colonised northern Europe, and subfossil bones from Norfolk show that it reached south east Britain at least., as subfossil remains have been found dating to 3000 BC. The reason for their extinction was probably climatic – the weather began to cool about that time and the British climate became much more like it is today. Even with the long lifespans of chelonians, a sufficiently long stretch of cool summers would have been sufficient to prevent an entire generation from successfully breeding. Today the nearest colonies are in central France and Germany, and even those often fail to breed in cool summers.

Attempts to introduce European Pond Tortoises to Britain were made in the late 19th and early 20th centuries. In 1894-5 a number were released south of Saxmundham in Suffolk, young were seen in 1929 and in spring 1932 a subadult was seen. Numbers were released at near Haslemere in Surrey between 1905and 1910, nine were captured in the same area in 1948, which may have been their descendents.

Despite all the above, it is very unlikely that any self-sustaining populations of either species is currently present in the UK. However, this is not the case in other parts of the world, and Trachemys scripta is one of the most widespread of chelonian species as a result of the pet trade. How much actual effect it has on other species is unclear – the main problem is likely to be as a result of competition with other species of terrapin where it has been introduced. In this connection its presence in China, where native terrapins are under considerable pressure from human activities, is of grave concern. Aside from China, Trachemys has also been introduced to Australia, South East and Far East Asia, Europe (there are reports from Spain, France, Cyprus) the Caribbean, Israel, Bahrain, Mariana Islands, Guam and South Africa.

Top: Trachemys scripta at Bristol
Below: Emys orbicularis at Twycross

Monday, 7 September 2009

Land of the Dodo 13: Bulbuls

Scattered from Asia to Madagascar, the Black Bulbuls of the genus Hypsipetes comprise nine surviving species, of which two survive in the Mascarenes, on reunion and Mauritius. An additional species, not yet formally named, is known from fossil remains on Rodrigues and died out either before or shortly after first contact – there are no surviving accounts of it known.

Bulbuls are medium sized, largely fruit-eating birds, supplementing their diet with insects, especially when breeding. The nest is an open cup, built in a bush or tree, and in general they can be thought of as the Asian equivalent of common European and American thrushes.

The Hypsipetes bulbuls of the Mascarenes seem to have originated from Asia, initially via the Seychelles. From the DNA evidence it appears that the Mascarene birds then went on to colonise Madagascar, which in turn then spread out again to the Comoros, where two species now occur – one originating from the wave that colonised the Mascarenes, and a second derived from the Madagascar Black Bulbul Hypsipetes madagascariensis.

The Reunion Bulbul H.borbonicus (called a Merle there) is still common, but the birds are more easily heard than seen. I was unable to locate any decent photos of either of the Mascarene species, so the picture at the head of this post is the common Indian Black Bulbul Hypsipetes leucocephalus.

Unfortunately the Mauritius Merle H.olivaceus is in a far worse state. The current population is under 300 pairs, which is far too low to be secure, but at least at present the population appears stable. The probable reason for its decline is habitat destruction, and it is hoped that the restoration projects currently under way will help to foster an increase.

Unfortunately, one obstacle to this is an introduced species, the Red-whiskered bulbul Pycnonotus jocosus. This is a fairly common cage bird, and has been introduced to both Mauritius and (more recently), Reunion. This has the potential to compete with the Merles, especially in human-modified habitats, and possibly act as a reservoir of disease. In addition, introduced predators such as rats may predate on nests.

Aside from habitat restoration, there is currently no specific conservation interventions aimed at benefiting the Mauritius bulbul. Some related species are however kept, and sometimes bred, in a few zoos, which provides a baseline of avicultural knowledge if a captive breeding programme for any of the Mascarene species is required, or possibly a re-introduction of a related species to Rodrigues.

Picture at top: Black Bulbul from Wikipedia
Picture at bottom: Red-Whiskered Bulbul from Wikipedia

Thursday, 3 September 2009

Research colloquium

Each month Bristol Zoo invites a speaker to present a talk on various research projects of interest to zoo staff and students. Yesterday the talk was from Dr Vincent Nijman, of Oxford Brookes University, on “Welfare Atrocities: Keeping conditions of captive primates in Indonesia”. As you might guess from the title, it made for a pretty shocking evening.

The basic issue is that the attitude to wildlife in Indonesia can best be described as medieval. Animals are simply commodities, and concern for their welfare, except at one or two places, is basically nonexistent. If an animal dies it is simply replaced, usually by one bought from the local market. The talk focussed on gibbons, but by all accounts other taxa are treated no better. The typical cage is only one or two cubic metres, with no interior furniture or frequently any cover from the sun. Feeding is usually inadequate, and often provided by members of the public buying sweets, sugar cane, or other inadequate foods from stalls in the grounds. Water is often polluted, where it is present at all.

What is particularly distressing is that the vast amount of animal suffering could be avoided by only a few simple measures. Simply cleaning the cages would be a start (many are only cleaned when the animal dies and is thrown out), and provision of ropes, branches, or just better food would be a big start. Both food and labour are cheap, so cost is not really a factor.

The general tenor of the lecture was that some of the best help western zoos could give would be simple information and advice. I have to say that Bristol is ahead of the game hear – via our links to Ape Action Africa and Yaoundé Zoo in Cameroon we are providing training to zoo staff and local education outreach to schoolchildren, but plainly there is far more to be done everywhere.

One of the more overlooked elements in conservation education is the total lack of contact with nature amongst the poor of the developing world, and the inevitable lack of interest. If you are living in a slum – and with the urbanization of the last 50 years that is where vast numbers of people in the developing world live – then even learning what is living in your own country is not going to be at all easy. I would expect that more people in London have seen a lion or giraffe than citizens of Nairobi have for example.

I would be interested if any readers could let me know what their local zoo does about education overseas – do they have any partner zoos abroad for example?

On another note, the colloquia I mentioned above are open to the public. The programme for the rest of the year runs as follows:

7th October: Summer and Winter vitamin D3 levels in platyrrhines and lemurs housed at Bristol Zoo with outdoor access

4th November: Effects of habitat alteration on the ecology and behaviour of Sahamalaza Sportive Lemur (Lepilemur sahamalazensis)

3rd December: Nutrition research at Paignton Zoo: Myth and reality in the kitchen

Finally, there is an important symposium coming up on Thursday 29th October - following our 2008 symposium on evidence-based conservation, the Bristol Conservation and Science Foundation has for this year’s symposium invited primatologists, both from the in situ (field) and ex situ (zoo) sector, to discuss success stories and challenges in primate conservation programmes. We aim to bring together evidence on how well we are doing to date in saving primates from extinction, and to suggest ways forward to ensure the survival of our closest relatives beyond the 21st century. Special emphasis will be given to the role of zoos in primate conservation.Invited speakers include:

· Prof. John F. Oates
· Ian Redmond OBE
· Dr Anthony Rylands
· Dr Anna Nekaris
· Dr Jean-Marc Lernould

The one-day symposium will be held in the Clifton Pavilion at Bristol Zoo Gardens, starting at 10.00 am and finishing at 5.30 pm. Registration fees are £75 per person and include a buffet-style lunch as well as coffee/tea breaks between the sessions and entry to Bristol Zoo Gardens. Registration forms are available from the Bristol Zoo website.

Sunday, 30 August 2009

A spiky problem

On view in Twilight World here at Bristol we have a group of interesting small rodents, the Turkish Spiny Mice Acomys cilicicus. Several UK zoos hold this species – Bristol has 75 (at last count!) and there are over 600 in UK zoos in all. The reason there are so many being kept is that the species is believed to be rare and possibly endangered in its homeland – at present it is only known from the type locality.

Spiny mice are an interesting group of rodents, with 20 or more species, mainly in Africa but some extending to the Greek islands, and, of course, Turkey. They are chiefly desert, or savannah woodland animals, and get their name from the bristly coat. It is believed this helps with heat regulation – the bristles would certainly not be an effective defence against predators.

Although long believed to be related to the murine rodents (house mice, brown rats and their allies) it now seems that the spiny mice belong to a separate group more closely related to gerbils, along with a few other African genera of rodents. Their reproductive biology is certainly different – instead of large litters of naked young, spiny mice produce small litters (2 – 3 in the case of A.cilicicus) of young after a fairly long gestation period of 5 – 6 weeks. The young are precocial, being born fully furred and with eyes open, and leave the nest when only a few days old. The life span is fairly long – up to 5 years although 3 – 4 is more usual.

As with most small desert rodents, spiny mice are omnivorous, feeding on seeds, flowers, plus some insects. The natural enemies would be cats, weasels or other small mammalian carnivores, birds of prey, and reptiles, especially snakes, although they are extremely alert and fast moving animals and I suspect from their fairly low reproductive rate that mortality in the wild is less than for similar rodents. They are good climbers, and will frequent bushes and rocky slopes as well as feeding on the ground. They do not seem to make nests – in the hot climates they prefer insulation is not really needed, and their habit of sleeping in groups (they are very sociable) means that even a cold night will pose few threats.

In captivity they need to be kept in groups – given sufficient space even multiple male groups work – with plenty of opportunity to climb. They need to be kept at least at room temperature – lower temperatures (below 15C) can stress them severely. In captivity the diet is a standard rodent mix with some added animal protein in the form of mealworms.

Some species of spiny mice are in the pet trade. The one usually seen is the Egyptian Spiny Mouse A.cahirinus, although the Golden Spiny Mouse A.russatus is also sometimes seen. They do not make especially good children’s pets though – they are a little inclined to nip and they move like lightening, which makes catching one when they get out a bit tricky. They are also good at chewing through plastic hamster cages – a large glass aquarium design is best.

Aside from the Turkish spiny mice most species from the mainland are not considered endangered, but the situation is different on the Greek islands. The Cyprus spiny mouse A.nesiotes has not been seen for many years and is believed extinct, and the Cretan spiny mouse A.minous is considered threatened. The reasons for the decline is probably an increase bin the human population, and even more cats, plus changes in land use reducing suitable habitat. One issue yet to be resolved however is the status of these endemic species – they are very similar to the widespread A.cahirinus and in view of the known tendency for rodents to hitch hike on ships from the earliest times, their must be a possibility that they reached the islands quite recently, possibly as a result of Greek or Roman shipping.

(Picture from Wikipedia)

Sunday, 23 August 2009

Banana scoffers of Africa

Living in African rainforests, and with a few species in more open country, is a group of mostly highly colourful, fairly large, arboreal birds, the turacos. Despite their African origins, several species occur at fairly high altitudes, and they are less susceptible to cold in captivity than one might think. They appear to be alert and curious, and I have seen several used in flying displays.

They are fairly widespread in captivity, both in zoos and private breeders, and a few species, such as the White-Cheeked, are semi-domesticated, with a few colour mutations being bred. However, other species are far more difficult to breed and are rarely if ever seen. Most species are not threatened, although some forms are localised and may be at risk from deforestation.

Turacos are currently classified in over 38 distinct taxa, currently grouped into 22 species in 6 genera, with the majority in the large Green Turaco genus Tauraco. They are a fairly distinct group, but appear to be closest to a group of “near passerine” birds including the cuckoos.

There is a very odd feature of turaco colour – whereas in almost all birds green colour is a structural effect, resulting from the structure of the keratin in the feathers, in turacos the colour is due to a green pigment. This can be extracted from the feather with a weak alkali solution.

Most turacos are week fliers, preferring to run or hop through the branches with only short glides, although they are capable of powered flight. More open country species, such as the Go-Away birds Corythaixoides, are stronger fliers. As such, turacos are an interesting model for early birds, as these are also believed to have been week fliers with similar means of getting around in the trees, although turacos themselves are fairly advanced birds.

Turacos are mainly fruit eaters, although some species also eat surprising amounts of foliage, and a few species take at least some insects, especially when rearing chicks. They will also eat flowers. They seem to have a fondness for banana – in fact one genus, Musphaga, actually means “banana-eater”.

In captivity they are fed chopped fruit, an artificial diet for softbills (“softbill” is an avicultural term for non-seed-eating birds), plus some leafy vegetables such as broccoli and lettuce. Many keepers also provide seasonal wild fruits such as blackberries.

They are fairly territorial, although territory size in the wild is unknown, and in captivity are usually kept either singly or in pairs. Flock behaviour in the wild does not appear to occur.

Turacos make an open, cup-shaped nest with two eggs. In captivity they readily take to nesting baskets, which may mean that in the wild they also re-use other birds’ nests. The chicks hatch after approximately 22 days and grow rapidly, leaving the nest at two weeks, although at this point they cannot fly.

Bristol Zoo currently has one paid of Red-Crested Turacos (picture at top from Wikipedia) on show. Unfortunately the aviary is not a walk-through, as you need to see the birds in good light to appreciate their beauty. They are in the aviary just before you enter our Butterfly House – if a reader is visiting Bristol Zoo please check them out. There has recently been a stud book set up, managed by Cotswold Wildlife Park, which has several species of Turaco on show, including the largest species, the Great Blue Turaco, which is Toucan-sized.

For more information on turacos, see the International Turaco Society website

Sunday, 16 August 2009

Land of the Dodo 12: The White-eyes

Scattered on most of the islands of the Indian Ocean, Australasia, and the pacific, as well as the mainland of Africa, and Asia is a huge group of small passerine birds, the White-Eyes, Zosterops. There are currently over a hundred species, with more being described each year. One would think that such diversity is a sign of a long history, but in fact the genus seems to have originated only a few million years ago. This makes Zosterops one of the fastest evolving vertebrate groups, about as fast as the well known cichlids of the African Rift Valley.

The reason for this rapid expansion is not altogether clear – separate species have evolved even on islands separated by only a few kilometres. This would suggest a species that does not move far, which is contradicted by the rapid spread of the genus as a whole. It appears that part of the reason is the short generation time and the tendency of the species to move around in flocks, which means that either large numbers of colonists arrive at a new location, or none – there is no steady “drip” of genes travelling from the source to the founder population.

White-eyes are fairly generalist small passerines, behaving in many ways like the leaf warblers Phylloscopus found across temperate Asia. The plumage is usually yellow-green, with a distinctive white eye-ring, which is where the name comes from.The main diet is insects, supplemented by fruits and nectar. The nest is an open cup made of grasses and moss, and the clutch is usually 2- 4 eggs.

There are three or four species surviving on the Mascarenes, living on Mauritius and Reunion. None are known from Rodrigues, but this may mean that they died out before being recorded. It appears that they are closest to the Asian White-eyes, although other Indian ocean islands have been colonised from Africa.
The Grey White-Eye is found on both Reunion and Mauritius. Depending on the taxonomist, the two islands are either home to a species each (Zosterops borbonicus and Zosterops mauritianus), or they are united as subspecies of the Reunion Grey White-eye shown here. Both forms are fairly distinctive, having lost the yellow in their plumage and also the white eye-ring, but in their behaviour they are typical white eyes. Both species are still common, probably because they are adapted to disturbed habitats such as man-made clearings.

Far more distinctive, and in more trouble, are the two species of Olive White-Eye. The Reunion species, Z.olivaceus, is allegedly still common, at least at higher elevations, but the Mauritius Olive White Eye Z.chloronothus (shown at top) is critically endangered, and is restricted to only 25 square kilometres on the mainland, with perhaps only 100 pairs. With a species with such a short lifespan this means that only 2 bad breeding seasons could result in its extinction, so strenuous efforts are being made to enable its survival, in the form of regeneration of native forest and captive breeding attempts. Some have been released on isle Aux Aigrettes, but until recently there had been no successful nesting. However, in October 2008 for the first time 2 young were fledged on the island.

The problem the Olive White-Eyes have is that they have become specialists. Unlike their adaptable ancestors, they have become specialist nectivores, feeding mainly on the nectar of native plants. With the widespread habitat destruction this has resulted in a loss of their food source, with inevitable results. Experiments are being made with supplemental feeding – as many in America who feed hummingbirds know, nectar feeding birds will often take to artificial feeding stations. The main problem is that nectar feeders tend to be territorial around food sources, so any feeding stations have to be widely scattered, which takes a lot of upkeep in difficult terrain.

Images- Mauritius Olive white-eye from Durrell Wildlife Conservation Trust
Reunion Grey White-eye from Wikipedia

Monday, 10 August 2009

New Arrival!

A major event for me at the zoo yesterday – I finally got to see (briefly) our new Okapi calf. She was born only a few weeks ago and still spends most of her time lying down in her mothers stable, out of the view of the public, but does venture out occasionally.

Okapis are of course the most distinctive living member of the giraffe family (readers who think there is only one species of long-necked giraffe are mistaken – there are several), and was only discovered by western science in the early 20th century. Before a specimen was obtained it was thought to be a surviving Hipparion (an extinct, 3-toed member of the horse family), but once research material was obtained it became clear it was a giraffid.

Live Okapis were first imported to Europe in 1918, but at first the stress of capture and transport by ship resulted in high mortality. Bristol Zoo received the first Okapis in 1961, and was the first zoo in the UK to breed them. Since the first arrival, we have bred over 30 Okapi, and both our current adults - Rubani the male and Lodja the female – are descendents of these first Bristol animals. The worldwide population in captivity outside Africa today is only 143, with 11 births in the last twelve months (including ours), plus some in captivity in the Republic of Congo.

Okapis our secretive and solitary in the wild, so they are hard to study. The diet comprises mainly leaves, with some fruits on occasion, grasses, or even fungi. As browsers, one might think that a tropical forest would provide abundant food, but in fact most rainforest plants protect themselves with powerful toxins, and a large animal has to travel far to get sufficient non-toxic plant food. To compensate to some extent for the poisons they consume, wild Okapis eat charcoal from lightning-struck trees and eat mineral-rich mud. Females are larger than males, and most of the time are dominant to them which means they get the best food. Even so, spare resources for growing a baby to term are in short supply, and Okapi pregnancies are consequently long – just under 15 months.

Newborn okapis spend a lot of time resting up in thickets. To avoid the smell of their faeces attracting predators such as leopards, okapi babies have an odd habit of waiting many days after giving birth before beginning to produce dung – as long as 41 days has been recorded at Bristol, although it has been as little as 8 days with other births.

The calves grow fairly fast, and after are full grown at three years.. The lifespan of an Okapi can be as long as 30 years in captivity, although 15 – 20 is more typical.

The main threat to the wild population is the bushmeat trade and deforestation. The current wild population has been estimated at about 20,000 animals, but the constant war in the Congo means that these figures may be very inaccurate.

(Photo from Bristol Zoo website)

Monday, 3 August 2009

The endangered pest

Recently added to the Wallace aviary birds here at Bristol is a small flock of a very pretty small songbird, the Java Sparrow. They are kept because they pose an interesting example of how species can be at the same time threatened in one area and a potential pest in another.

Originating, it is believed, in Java and Bali in Indonesia, their popularity as cage birds means that they have been taken throughout neighbouring islands and more recently all over the world – there is for example a well established feral population in Hawaii. They are also popular in aviculture – I have a few in my aviary in my back garden right now – as they are extremely easy to care for and always present an incredibly smart appearance (bar a few weeks a year during the moult).

Javas (Also know as Rice Birds), have the scientific name Padda oryzivora. Oryzivora means “Rice Eater”, which will give a clue as to why they were persecuted in their homeland. They are extremely prolific, and as a result were major crop pests.

Javas are an estrildid finch, in fact the largest living species, and as such belong to a group of small, mostly grass-seed eating birds, which include several other popular cage birds such as the Zebra finch, Bengalese, and Gouldian finch. The basic ecology of this group of birds is to subsist as adults mainly on ripe and ripening grass seeds, supplementing with some other vegetable matter, and feeding their young on insects and unripe seeds. They often have large broods of young and in the right circumstances can increase their numbers very quickly. The downside of this is that they tend to be short lived in the wild, so adverse situations can result in equally rapid declines. Their main natural predators are probably snakes and small mammals when nesting, and birds of prey once fledged.

In recent years the Java sparrow has faced such a decline – in fact it is classed as Vulnerable on the IUCN Red List – and a recent survey could only locate 109 individuals at 17 sites. In addition, persecution in those areas where it has been introduced has resulted in declines amongst feral populations. The most probable cause is persecution by farmers, capture for the cage bird trade (although this is completely unnecessary as they breed well in captivity), and possible competition form the Tree Sparrow Passer montanus, which is the common city sparrow in Asia.

Javas were at one time introduced to Mauritius, undoubtedly as cage birds, and were breeding in the wild by the 1750’s. However, later persecution and probably competition with House Sparrows resulted in their extinction in the early 20th century.

Closely related to the Java sparrow is the Timor sparrow Padda fuscata from, as you might guess, the island of Timor. Timor sparrows are much less common in aviculture, although also threatened, but are dark brown where a Java is grey. It is currently more common in the wild than the Java, although it faces the same threats and is consequently classed as Near Threatened by the IUCN.
The conclusion of all this is that even the commonest species can be much more threatened than it looks, especially if it relies on groups for survival. Most people will be aware of the catastrophic collapse and extinction of the Passenger Pigeon – it is important therefore to build up as wide a knowledge of all species, both in the wild and in captivity, as it is possible to arrange.

If you wish to learn more about these beautiful little birds, look at the Java Finch Society website

Tuesday, 21 July 2009

Land of the Dodo 11: Weaving a spell

Scattered through Madagascar and the nearby islands of the Indian Ocean is a group of at least 10 species of weaver birds, the fodies of the genus Foudia. Unlike the colonial weavers of mainland Africa, they behave far more like most passerines, nesting in paid by themselves.

Primarily forest birds, one species, the Madagascar or Cardinal Fody, has adapted to open grassland and is often found around farmhouses. As a result of people liking their colours, the Madagascar fody has been taken to many other islands, including St Helena in the Atlantic.
At first contact, there were three fodies in the Mascarenes, one for each of the islands, but today only the Rodrigues fody F.flavicans (left) and the Mauritius fody F.rubra (top)survive. Even these only barely managed to hang on, with the Rodrigues at one time down to perhaps 6 pairs before conservation measures helped its recovery (it currently stands at 900-1000 birds). The Mauritius fody is in far worse shape, and there are intensive conservation measures being undertaken to help it to survive.

Fodies are most closely related to the Orange Bishop, Euplectes, an African weaver bird that like the fodies nests independently. One might think that the birds on the islands originated from Madagascar, but analysis of their DNA shows that the sequence runs from the Seychelles, then to Rodrigues, then Mauritius, and finally Reunion, Madagascar, and the Comoros islands. Originally a rainforest bird, one of the Madagascan species adapted to grassland, later became a bird of farmland, and has now been introduced to all three islands, which on Mauritius and Rodrigues it shares with its close relatives.

The main cause of the decline of the fodies was probably introduced rats, which readily predate fody nests. It is one of the ironies of conservation that the only reason the Mauritius fody survived was because of aplantation of introduced Cryptomeria trees, which do not provide food for rats or monkeys and consequently enabled at least some nests to escape.

Intensive help for the fody, and indeed the other passerines of Mauritius, only started in 2002. Fodies have proved reasonable straightforward to breed in captivity, and techniques of hand rearing have been devised to enable chicks from wild nests to be reared. This is of course a very labor intensive process, and readers may be interested in the rearing diet. This comprised the following:
Bee larvae (throughout the rearing period)
Crickets (first guts, then abdomens)
Waxworms (older chicks only)
Mice (first internal organs, then cut up as the chicks grew)
In addition, chicks received Nutrobal, Avipro, and Nekton as vitamin and mineral supplements

Initially chicks were fed hourly between 05:00 and 21:00, with the intervals between feeds increasing to 2 hours by the end of the rearing period, with chicks fledging at 18 days. Hand reared chicks were kept in a brooder at 36 degrees at first, gradually reducing as they fledged to the ambient air temperature of 26 degrees.
These hand reared chicks were released on isle aux Aigrettes, and the attempt has proved a great success. Fodies are now breeding on the island, with over 150 birds. One problem is the introduced Madagascar Fody (below), which could potentially hybridise. It appears however that the difference in preferred habitat and song make it unlikely for the two species to interbreed, but the situation is being closely monitored.

Mauritius Fody image from Durrell Wildlife
Rodrigues Fody from ARKive
Madagascar Fody from Wikipedia

Monday, 13 July 2009

Is it a mouse? Is it a deer? No – It’s the Mouse Deer!

Tucked away in Twilight World at Bristol Zoo, and all too often overlooked, is one of the smallest of the world’s hoofed animals, the Lesser Malay Mouse Deer Tragulus javanicus. Only about half a meter long, and weighing about 2kg, it is an inhabitant of south east Asian rainforest and scrub, often close to water – basically anywhere they can find dense cover.

Technically, the common name is something of a misnomer, as it is actually not a true deer, but a chevrotain belonging to the family Tragulidae, which is close to the base of the group of hoofed animals called the artiodactyls or even-toed ungulates, which also contains the pigs, hippopotamuses and giraffes, and which is now thought to be the group that gave rise to the whales. Their fossil record dates back to the Miocene in Europe (c15mya), but they had a long record before then, as the earliest whales are known from Eocene rocks of 47.5 mya, and mouse deer must have branched off the group which gave rise to them much earlier – probably just after the end of the Cretaceous period when non-avian dinosaurs became extinct, if not earlier.

As primitive ruminants, mouse deer lack many of the characteristics of more advanced forms – for example the main form of male display is by enlarged canine tusks rather than antlers or horns. The stomach is fairly simple, with only three chambers compared to the four of deer or cattle, and all in all they bear a surprising resemblance to the agoutis of South America, which are of course rodents. The diet is mainly vegetarian, especially fruits, although they do eat snails and some insects as well, and they probably also take fungi.

They reach maturity quickly – usually within a year but they have been known to breed at six months. They have one or two young at a time as far as is known, but they have four teats, which may indicate they sometimes produce larger numbers of offspring.

There are several other species of mouse deer, of which the commonest is the Greater Malay Mouse Deer Tragulus napu. There are also mouse deer in India, and also a more distantly related form in Africa, Hyemoschus.. It is very likely that more species are to be described – with such a huge range and antiquity of the group, there are probably several cryptic species included in the described forms. This makes things very difficult for zoo conservation, as unless you are careful to breed only animals from a known geographic location there is a strong risk of producing hybrids which have no value for conservation purposes.

As “bite sized” animals, mouse deer are understandably nervous creatures, but they tame quite easily – in Thailand they are often kept as pets in the back garden. They figure prominently in folklore – Mouse Deer is a trickster figure like Brer Rabbit who triumphs by outsmarting anything that wants to eat him – which is everything!

The chief threats they face today are hunting and habitat destruction. Their status in the wild is very little known – as nocturnal, secretive animals they are very hard to study. The only Mouse Deer that are likely to be seen in zoos outside Asia are the Greater and Lesser Mouse deer. European zoos have concentrated on the Lesser Malay, whereas American zoos have concentrated on the Greater Malay - this ensures that there is less duplication of effort. There have been efforts to encourage the expansion of the European zoo population of Lesser Malay mouse deer – Bristol Zoo currently has only one pair but has successfully bred them in the past and distributed them to other collections. According to ISIS the current European zoo population stands at 44 animals, with 9 births in the last year.

(Photo from Wikipedia commons - ignore the eye shine)

Friday, 3 July 2009

A Tale of Two Squirrels

The commonest wild mammal now seen by the average person in the UK is an introduced species, the Eastern Grey Squirrel Sciurus canadensis. Introduced in the late 19th century to England, it spread rapidly from the first. It has widely been blamed for the decline of the Red Squirrel Sciurus vulgaris, and practically no one has a good word to say for it.

However, the true picture is a bit more complex. For one thing, practically all the Red Squirrels in the UK are themselves the result of reintroductions from mainland Europe, which began in Scotland as early as 1772!

Our original Red Squirrels were probably an endemic race of the widespread Eurasian Red Squirrel, which has a huge range in Europe from Norway to Spain, and east as far as Greece. In the Middle East it is replaced by the very similar Persian Squirrel, whose only European station is on the island of Lesvos, which is in sight of the Turkish coast.

The Red squirrel is primarily a conifer specialist, in the south being found in stone pine woods around the Mediterranean and at altitude in the Alps. It can survive in deciduous forest, where it depends heavily on Hazel. In addition to seeds, it will take birds eggs, the buds of trees, and bark. However, in Oak woodland it is at a disadvantage, as it has trouble digesting acorns.

Red Squirrels reached Britain at the end of the last Ice Age, when the tundra that had covered southern Britain was replaced first by Taiga forest of Birch and Pine, then in turn by mixed deciduous woodland. Even after the Channel formed and Britain was isolated, squirrels would have been fine in the oak forests that covered England, especially along rivers where the activities of Beavers would have encouraged Hazel coppice.

The squirrels’ troubles started when Neolithic farmers arrived and began clearing the woods for farmland. The deforestation was quite rapid – by the Roman period the proportion of forest cover in England was about the same as today – but the habitat loss was inexorable. By the 18th century the demands of a growing population and the building of the British Navy had reduced tree cover to perhaps 2% of the country, and even in Scotland few if any remain – the last in Sutherland was reported in 1642 for example.

The needs for the British navy to have a source of timber for shipbuilding then caused a swing in the squirrels favour. As well as new plantations of conifers made by landowners, they introduced Red Squirrels. Some of those were moved from other parts of the country, but there were also imports from Scandinavia.

It is in this context that the Grey squirrels were introduced. As primarily animals of deciduous woodland, and with few predators (Pine Martens, Foxes, and most birds of prey having been wiped out or restricted in numbers by gamekeepers) they had a built in advantage, as they have no problem feeding on acorns or indeed anything else. In addition, they seem to carry a parapox virus which Red Squirrels are susceptible to, and as a result it seems inevitable that, at least outside the Highlands and some offshore islands in the south that they have not reached (The Isle of White and Brownsea island for example), they will continue to be the typical squirrel of Britain.

There may however be a chink in their armour. In areas at the edge of their range in Scotland they appear to be at a disadvantage compared with Red Squirrels when faced with predation by Pine Martens. These were wiped out over most of their range in the UK, but are now starting to make a comeback. Grey Squirrels are more terrestrial than Reds, and are easier for Pine Martens to catch. As a result, in areas with healthy Pine Marten populations, Grey Squirrels seem to decline, if not actually die out.

The status of Pine martens in England is unclear. They certainly seem to be extinct in the south east, but in Wales, possible Cornwall and the Lake District it is possible small populations survive. Reintroduction seems unlikely in the near future, however in the north of England Scottish Pine Martens seem to be re-colonising naturally. If you see a Pine Marten, they are quite unmistakeable –good luck on your search!

Saturday, 27 June 2009

Well done Emma!

There are many things people can do to help gorillas either directly or via gorilla charities. Jumping out of an aircraft at over 10,000 feet wearing a gorilla costume is not one I would choose, but one of the Sunday volunteers I work with has done just that. Emma has just turned 21, and got the skydive as a birthday present from her parents. All I can say is – she has more guts than me by a long shot. One minor problem – the feet came off on the way down, so if anyone finds them could they send them to Bristol Zoo?