Monday, 19 January 2009

The deadly teddy bears of Asia

Prowling through the forests of West Africa and Asia are a group of nocturnal primates distantly related to bushbabies and lemurs. Varying in size from a half grown guinea pig to a ring-tailed lemur, the lorises are an ancient group, with a fossil record dating back 40 million years or more.

A member of the loris family is easily recognised. The tail is short or absent, the hands are modified to give a good grip on slender vines and branches, and the very large eyes face forwards. They do not jump, but instead move methodically through the forest with something of the gait of a chameleon. In many ways, they behave almost like chameleons, and their hands are modified by the reduction of the second digit which gives their hands a very chameleon-like appearance. As with chameleons, they seldom drink standing water, but have been seen to lick raindrops off leaves.

The number of species of loris is at present uncertain. As with many nocturnal animals, they rely on scent or call to distinguish each other, and as a result different species are hard to tell apart. At present the total is as follows:

1) Loris. The slender lorises, with two species and at least 6 identifiable forms. Found from India and Sri Lanka
2) Nycticebus. The slow lorises, with two species and numerous regional varieties. Found in South East Asia
3) Arctocebus. The Angwantibos. 2 species in West Africa
4) Perodictus. The Potto. At least 3 forms, also in West Africa

Unfortunately many today, especially in Asia, are highly threatened. The main reason, as you might expect, is deforestation. Lorises are specialised for clambering through dense tangles of vines and other undergrowth, mostly within 5 metres of the ground, and are not famed for their speed, although they can move fast when they want. As a result, they are easy to catch, and their undeniably cute appearance means they are captured for a local pet trade. They are also used in local medicines.

Lorises have historically not done well as captive animals, and for most species there is no viable captive population, and why this is so has only recently been understood.

Most importantly, the diet of lorises is unusual for a primate. As is well known, practically all primates are mainly vegetarian. Some prefer leaves, others fruit, some add gum or sap, but animal food is a small part of the diet. Smaller primates often eat a lot of insects, and larger ones like chimpanzees or baboons will even catch monkeys or gazelle fawns, but generally faced with an unfamiliar species a selection of fruit and leaves plus some insects will at least give a start on working out the ideal captive diet.

Lorises however are quite different proposition. The vast proportion of their diet is composed of insects and animal prey, to which they are attracted by movement. Slender lorises, which in some species are lemur sized, frequently catch birds almost their own size (although stories of them catching peacocks are probably mythical). Slow lorises eat slightly more plant material, especially gum and sap, but they too catch many insects. Much of the typical insect prey of a loris is toxic or unpalatable, such as poisonous ants or hairy caterpillars, but they prefer tastier prey like lizards where possible. Although slow moving when travelling, lorises have a very fast grab, and when catching birds will usually bite the head of the prey to kill it.

As a result of these dietary specialisations, lorises are prone when fed on a diet high in sugars from fruits and lacking in insect and animal protein to develop kidney disease, diabetes, and dental disease, with predictable results.

The other main problem with captive lorises is that despite their size they pose a serious risk to people coming in contact with them. A slow moving, easily captured species needs some defence, and lorises have a defense unique among primates, and very rare among mammals – they have a poisonous bite. The loris “arms” itself by licking glands on its arms, and an enzyme in the saliva then transforms the secretion into one capable of causing serious allergic reactions, even death, after biting its attackers. The same poisonous saliva is used by the mother to protect her infants – before “parking” them on a branch before going off to feed she licks them all over, rendering them distasteful to predators at the least. The loris has a stereotyped threat display where they hold their arms over their head, with the brachial glands at the ready, and I personally suspect that the contrasting head patterns many lorises show may actually constitute warning colouration to reinforce the display.

Although as I mentioned earlier lorises are seldom kept in captivity, we are fortunate to have the pygmy slow loris here at Bristol in Twilight World, and have bred them on several occasions. Ranging into southern China, the pygmy slow loris reaches quite high elevations, and in the winter months puts on a considerable amount of weight and goes into a near torpor.

Well, what are the implications of all this for the loris? First of all, it shows the importance of field studies. Animals in captivity can be the source of valuable information, but studies of wild animals are vital to enable us to provide what animals actually need in captivity, instead of what we think they need. The other is what amazing animals they are, and how vital it is that they are conserved in the wild for future generations.

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