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

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)

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.

Conclusion

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?

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

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

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.