Monday, 4 February 2013

Lemurs 5: Lac Alaotra Gentle Lemur

Lac Alaotra Gentle Lemur
Across the world, many different animal lineages have produced groups specialised in consuming the leaves and culms of the local forms of bamboo. Most famously of course the giant panda is a bamboo specialist, and so to a lesser extent is the red panda, but several primates have specialised in bamboo – in fact some populations of mountain gorilla feed almost exclusively on bamboo. In Madagascar a group of otherwise unremarkable lemurs have become bamboo specialists, and one population of these has gone even further and become the only known primate to specialise in feeding on water reeds. This is the Lac Alaotra Gebtle Lemur, known locally as the bandro, Hapalemur (griseus) alaotrensis.

Lac Alaotra is that tiny red dot in the north east of the island
As currently organised, living bamboo lemurs are placed in four or five species. And up to eight distinct taxa. Most distinct is the Greater Bamboo Lemur, Prolemur simus, which may now be down to less than 100 in the wild and is on the IUCN list as one of the worlds most critically endangered primates. The others are grouped as four or five species, and range in suitable habitat over most of the island.

Greater Bamboo Lemur
Specialising in a diet of bamboo has several problems. The most acute is that many species of bamboo protect themselves against being eaten by concentrating cyanide in their tissues, but the bamboo lemurs have their own defences and can tolerate cyanide levels that would be lethal to other animals their size. They also need to be highly selective in what parts of the plant they eat, as adult bamboo leaves are severely lacking in nutritional value. To avoid dietary deficiencies, they carefully select young leaves and emerging shoots, and to aid them in this they use more dextrous hands than those possessed by most lemurs, which tend to process food by eating directly off the plant rather than picking it and holding it to eat in the way that monkeys or apes do.

The great threat to all the bamboo lemurs is habitat destruction. Deforestation not only destroys their bamboo forest homes directly, but also increases drying out of the forest and increased fire risk. They may also be hunted by local people for food.

The Lac Alaotra Gentle Lemurs that we have at Bristol are perhaps the most dietarily specialised of all primates. Although often classed as a separate species, they seem in fact to be a local subspecies at best of the fairly widespread (until recently anyway) Grey Bamboo Lemur H.griseus. Lac Alaotra is one of Madagascar’s larges water bodies, but here too habitat destruction is radically altering life for the animals of the lake. Already the Alaotra Grebe Tachybaptus rufolavatus has become extinct, and ongoing conversion of reed beds to rice fields is threatening the other local endemic forms. Gone from the lake, but recently rediscovered and now with a small captive population, the Madagascar Pochard may have just survived, but any re-establishment of captive bred birds in the wild is many decades away.

This is all that is left of the Alaotra Grebe
Today, aside from the captive population of only 95 animals, perhaps under 5,000 bandro survive in the wild, possibly much less. In captivity they have been bred in various zoos, including Bristol, and we have just started with a new young pair that we hope will breed in the near future – they seem to get on well together anyway. They can be seen in a secluded corner of the zoo just behind the otter enclosure, out of the way of passing visitors. At the zoo they get a daily ration of bamboo, which is supplemented by special prepared diets designed for folivorous primates and a small amount of fruit. If they breed, we can expect one or two young in a litter, which will stay with the parents for one or two years before moving on to other collections.

Madagascar Pochard
Next week, the grand finale to this series on the lemurs of Madagacar, and probably one of the world’s weirdest mammals – the Aye-Aye

(images from wikipedia, Bristol Zoo)

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