Whats this?

On Monday I had a day out at Kew Gardens up in London, I will do a full post about it next week, but in the meantime how many people reading this blog can identify this flower? (answer next time)

Gorillas part 3 - diet

Ask a member of the public what gorillas eat, and they will say bananas. As with most things you everyone knows however, this is not the whole truth. As two species occupying a vast area and many different habitats, the diet of gorillas is in fact highly varied.

The bulk of a gorillas diet comprises not fruits, but the leaves and stems of herbaceous plants. One might think that these are easy to obtain, but in fact eating leaves is often the riskiest way to make a living. The problem is that plants protect themselves with a variety of defences, both physical (thorns, stinging hairs and so on) and also chemical defenses in the form of poisons or highly distasteful compounds such as resins or tannin. Investigators who have tried tasting the leaves and plant parts eaten by gorillas usually report that they are extremely bitter or resinous to the taste.

As a result, gorillas (and other forest leaf eaters) often have to travel long distances to locate plants they can eat. Many of these may taste best only at certain times of the year, and as a result gorillas eat a huge variety of plant species – up to 180 species have been reported as being eaten by one population of Western Lowland Gorillas. Popular food items are bedstraw (Galium), wild celery, nettles and bark.

Mountain Gorillas in Virunga live at altitudes where the variety of plants is much reduced, and as a result the list of plant species is shorter. The bulk of their diet in fact consists of bamboo shoots, which they are strong enough to break of the plant even though the stems are as thick as my wrist.

Fruit is eaten by gorillas when they can get it, especially by Western gorillas which live in more productive forests, but the percentage is always less than for chimps. The large size of gorillas, especially the silverbacks, limits their ability to reach the outer branches where most of the fruit is.

As with chimps, gorillas are fond of insects, especially some species of ants. The preferred species appear to be rich in iron, and it has been suggested that this may help in the detoxifying of plant poisons in their livers. Mountain gorillas do not have access to these, but instead eat iron-rich mud at various traditional sites. Earth eating is common among many vegetarian rainforest animals, and even birds such as macaws will eat earth to help them with toxins in their diet. The microscopic structure of the clay also absorbs plant toxins before they are taken up by the gorillas’ digestive system.

As well as food, plants also provide gorillas with medicine. Both chimpanzees and gorillas specifically seek out certain plants they otherwise avoid when feeling unwell, and have a highly standardised way of selecting and consuming the pharmacologically active part of the plant. Gorillas in the wild often carry a high load of intestinal parasites, and certain leaves may be carefully prepared and then swallowed whole – the hairs on the leaves tarp the worms and take them out of the body.

All of this has implications for the diet of captive gorillas. Most gorillas are fed a variety of commercially grown fruit and other produce, in many cases supplemented by a commercially produced biscuit. The problem is that commercial fruit is nothing like the wild fruits eaten by gorillas. Just compare a bite from a crab apple with an apple from a supermarket, and you can see what domestication can do to a plant. Humans have a sweet tooth, and we have bred our fruit over thousands of years to be high in sugar and water, and low in protein and fibre – the exact reverse of a wild fruit. Feeding commercial fruits to fruit eating rainforest animals is probably a main reason why captive primates of all sizes are prone to obesity and tooth decay.

As a result, most zoos are re-thinking their diets for gorillas, reducing the amount of fruit and increasing the amount of leafy vegetables and browse. Here at Bristol for example, gorillas get celery, leeks (of which they are very fond), leafy greens and cut branches among other things. They are also fond of herbal tea!

Land of the Dodo 7:Going Batty

When first colonised, the Mascarenes were home to three species of fruit bat and at least three – possibly more – species of microbat. One of the fruit bats, and at least one of the microbats, is now extinct. The other microbats are doing well, but the two surviving fruit bats are both much reduced in numbers and range.

Traditionally, bats have been divided into two groups, the fruit bats or megabats, confined to the Old World, and the microbats, which have a worldwide distribution. The main reason for this is that the old world fruit bats do not use echolocation in the same way as microbats do, and it was believed that this may even have been because they were not closely related to microbats, possible having developed flight independently. It now appears that this distinction is inaccurate, and the most basic division in the bats is between a group containing the megabats, horseshoe bats and their relatives, and all other bats. Interestingly, horseshoe bats wrap their wings around themselves when at rest as do megabats, whereas in other species the wings usually are held at the sides. In the Americas, many species of microbats also eat fruit.

Fruit bats are important pollinators (despite their name, they are fond of nectar) and also dispersers of seeds. A lack of these is a major cause of delays in regeneration of cleared tropical forests world wide, and it has been shown that encouraging fruit bat population helps considerable in restoration of forest cover.

Unfortunately, fruit bats and people have very similar tastes, and as a result in many parts of their range they are persecuted as crop pests. Recently the Mauritius government authorised a cull of one of the surviving species, the Mauritius Fruit bat, despite the estimated population being only 20,000. This has now been halted pending further investigation of the status of the species.

On Rodrigues, there were at least two species, the Mauritius Fruit Bat and the Golden Bat (Photo of Golden Bat at head of this post – image from Lubee Bat Conservancy). Only the Golden Bat survives, although it formerly bred on Mauritius as well. It is seriously endangered, with a world population estimated at 5,500, which is still a great improvement on the case in the 1970’s, when it was down to 150.

Sadly extinct is the smallest and most widespread of the three fruit bats of the Mascarenes, the Rougette. Possibly most closely related to the surviving Seychelles Fruit bat, it lived in large groups in hollow trees. This is unusual for fruit bats – most species roost on open branches of tall trees. It was this habit that may have caused its extinction – they were easy to capture both by people and introduced monkeys, and deforestation would have removed roost sites.

The insectivorous microbats on the islands seem to have survived better, with the exception of one species on Reunion, the Pale House bat. This may have gone extinct for the same reason as the Rougette – it seemed to have had similar habitat preferences. Most of them have close relatives in Madagascar, Africa or India. People tend not to think of bats as migrants, but many can travel long distances over water – there is a record of a Little Red Flying Fox which managed to reach New Zealand from Australia.

There are several institutions which hold Golden Bats. Bristol formerly held a non-breeding group, but these have gone to other collections. They are often quite active by day, especially in the afternoon. Bristol currently holds a breeding group of Livingstone’s Fruit Bat, which I will blog about another time.

Year of the Gorilla 2 - Bristol Zoo efforts

Since 1997, Bristol Zoo has been working with the Cameroon Wildlife Aid Foundation (now renamed Ape Action Africa) which has a base at Mvog-Betsi zoo in Yaounde, and now also administers a sanctuary at Mefou National Park. Working with the Cameroon government, Bristol supports the activities of AAA by advising local members and providing veterinary support and training. Bristol has always majored on education for local children, and we are supporting educational activities out in Cameroon.

AAA currently cares for several chimpanzees and gorillas orphaned by the bush meat trade. This is unfortunately widespread, and contrary to what may be thought it is not a subsistence level trade – gorilla meat is very expensive and poorly paid drivers of logging companies find bushmeat an easy way to earn cash.

As a result of this, AAA received numerous orphan primates. At Mefou and at Yaounde these are cared for and hopefully rehabilitated. The problem however with releasing any of the apes in particular is that they are not afraid of people and so are at grave risk of being killed if released outside a protected area. In addition, they have all been exposed to, and are potentially carriers of, human diseases that could prove very dangerous to wild gorilla or chimpanzee populations. The best strategy therefore for orphans is therefore a semi-natural situation as at Mefou.

AAA has a volunteer scheme as part of its fund raising activities. Volunteers can work out at Mefou or Yaounde provided they fund themselves and are prepared to spend sufficient time there. Details are on the AAA link on this blog.


















(Images from CWAF/AAA website)

Land of the Dodo 6: Lizards by night and day

Before contact, the Mascarenes were home to at least 24 species of lizard in six genera, and they occupied all habitats from rock crevices to the canopy. They can be divided into two groups – the mostly terrestrial and insectivorous skinks and the climbing (on trees or rock surfaces) geckos.

There were seven different species of skink on the various islands, of which four still survive. Extinct before even being described was the largest lizard on Mauritius, the 60cm long “Didosaurus” which is only known from subfossil remains and was probably wiped out by rats.

The most obvious of the lizards were the various species of day gecko, Phelsuma, of which there were at least nine. Four of these survive, and are important to the native plants as they are fond of nectar and are important pollinators. . One of the surviving species, the Blue-Tailed Day Gecko of Mauritius, is at the head of this post (picture from MWF website). At Bristol we have two species, both from Madagascar where the genus probably originated and which has most of the world’s species. Unfortunately, the survivors do not include the most spectacular gecko of them all, the 1 metre long Newton’s Day Gecko of Rodrigues, which was a vivid emerald green

Much less obvious were the night geckos, Nactus, of which at least two species survive. These seem to have had a small radiation of species in the Mascarenes, after managing to colonise the islands from Australasia, where a few other species are still found.

All these lizards were important as food sources for many of the birds, especially the Mauritius Kestrel and the various endemic owls. They also dispersed seeds and pollinated plants as noted above.

Unfortunately, as well as the native wildlife these days the lizards have to cope with introduced competitors. House geckos (Hemidactylus) are widespread and compete with the native Night Geckos, and even introduced honeybees are competitors for nectar with the Phelsuma geckos.

Relocation efforts and reintroduction to offshore islets has been a great success, and for example the Telfairs skink Leiolopisma telfairii, which was restricted to Round Island, can now be found on Isle Aux Aigrettes and Gunners Quoin, where it is breeding well. This is important, since the larger skinks are omnivorous and are probably significant dispersers of the seeds of native plants

For further information (and some great pictures) look at the MWF website in the links section.