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)

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!

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?

Year of the Gorilla 5: The dark side of gorillas

Gorillas. Peaceful, placid vegetarians, wanting only to be left alone for a photo op with David Attenborough. It is quite impossible that these gentle giants could have a nasty streak.

Yeah. Right.

Actually, all the great apes have a violent streak. Humans of course are the most creative in this respect, but all our close relatives can be killers too. Chimpanzees go in for tribal warfare, orang-utans go for sexual assault and many wild bonobos are missing fingers from fights.

With gorillas, violence takes the form of infanticide. This is not just an occasional accident, but a deliberately pursued policy of attacks on infants, especially by solitary silverbacks, with the goal of persuading females to join new groups.

The rationale behind the attacks seems to go like this:

1. A female with an infant is unlikely to leave the group she is in unless the silverback dies.

2. Silverbacks are hard to kill, especially if they have a group of breeding females to help them.

3. If a female loses an infant, she is likely to abandon the silverback who failed to protect her baby.

4. Even if the male whose group she joins is the one who killed her baby in the first place

Even if a female without a baby joins a new male, if she gives birth soon after joining, there is a good chance that the silverback of the group may kill her baby, despite what are usually vigorous attempts at defence.

This kind of behaviour is widespread in many animals with a reproductive system of a single (or small number) of males and a larger group of females, especially when raising a newborn to independence takes a large part of an adults life. By killing unrelated infants, the male increases the chance of his own offspring being raised before he is replaced in his turn.

So far at least, infanticide has mostly been observed in Mountain gorillas, where infanticide causes about 37% of infant deaths (total deaths in the first year of life run at about 34%). Putting these two numbers together, it suggests that 1 in 10 baby Mountain gorillas are killed by their own kind before they are one year old.

In Western gorillas, infanticide (so far) seems to be less common. This is probably because, as mentioned in a previous post, Western gorillas seem to live in extended clans of related male family groups, and any unattached males are likely to be related to any infants they encounter.

The heavy poaching that Mountain gorillas have experienced has probably made matters worse. Silverbacks are the first to be targeted by poachers, and the result has been a breakdown of gorilla society where unrelated males, fleeing poachers, have moved into areas where they are unknown and any infants are not related to them.

All this has implications for gorilla conservation, especially the release of male orphans into the wild. Release of human-raised or captive bred animals is problematic in any case, because of the risk of exposure of wild animals to human diseases caught in captivity and the difficulty in teaching true independence to an animal which has not had the opportunity to learn how to survive from its mother. Releasing even successfully rehabilitated males into a social environment where they do not know the males in the wild groups they encounter might well do more harm than good, resulting in increased attacks on infants by the new males and a negative impact on the wild numbers.

In future posts, I will discuss how orphaned gorillas are cared for and what can be done to give them at least near-normal lives.

Picture - Salome and Komale, Bristol Zoo gorillas

Bristol Festival of Nature and other news

This morning I went down to the Bristol Festival Of Nature down by the harbour side. This has been going on for several years now and is basically a shop front for a huge variety of societies and conservation organizations, especially those in the Bristol Area. The zoo was represented of course, both by volunteers looking after some invertebrates, and representatives of the Education department – Bristol majors on education and has at the last I heard over 10,000 pupil visits per year. For full details of the programme – which continues tomorrow – see here: www.festivalofnature.org

There are loads of activities for children, and important local groups like the Avon Wildlife Trust and Bristol Naturalists, as well as national groups like the RSPB, The Hawk and Owl Trust, and the Wildfowl and Wetlands Trust.

On other news, as part of the publicity and fund raising for the Year of the Gorilla, one of our Sunday volunteers (the day I work) is doing a sponsored sky dive. All I can say is that she does not look the type to jump out of a plane at 10,000 feet (especially wearing a gorilla costume) If you would like to sponsor her, go here: www.everyclick.com/emmaoneill

I will be posting next week on the Bath & West show, which was a great success - have agood weekend everyone - I have to go paint the hall.