Small, brown and jumping. Tarsiers through the eyes of Filip
What is it – small, brown and jumping? For most of us the answer would probably be ‘frog’, although this time it would be a miss, as it is, of course, a tarsier. They were, or rather one of their species, the reason why I came to the Philippines almost 10 years ago to take part in a research project. What, then, are these animals, these tarsiers?
Tarsiers – small primates
The tarsiers are a group of 14 primate species (although their number remains an open question) that inhabit only parts of Southeast Asia. At present, they can only be found in 4 countries (or rather in some of their regions/islands): Indonesia, Malaysia, Brunei and the Philippines. In terms of size, tarsiers are among the smallest primates in the world.
Taxonomy – where do we place tarsiers?
For a biologist, tarsiers are of particular interest for several reasons. The first is their taxonomic position which has been a topic of a hot debate. The question is: should they be included in the prosimians (lori, galago and lemurs) or in the monkeys, including us? Initially, tarsiers were classified with the former as Prosimiae (prosimians), while the rest of the primates were categorised as Simiae, or monkeys. The situation changed at the beginning of the 20th century, when tarsiers were joined with monkeys to form Haplorhini, while the prosimians were left alone as Strepsirhini.
The open debate among taxonomists is still ongoing, as our small primates have features that are partly characteristic of prosimians, such as morphology or behaviour. In contrast, they are closer to monkeys in terms of anatomy, genetics or reproduction. They also possess traits found only in tarsiers – they are the only vertebrates (apart from owls) that can turn their heads 180 degrees, and their eyes are as large or larger than their brain (which does not have convoluted surface). They are, in turn, the only fully carnivorous primates. It means that they only consume live animals (a wide range of insects, arachnids, frogs, snakes and occasionally birds), what makes them unique in this group of animals.
Without a spark in the eye
Tarsiers are very difficult to see, as they are only active at night, while they tend to spend their days in dense vegetation without making any movement. Even at night, it is more difficult to see tarsiers than other nocturnal primates because they do not have, so-called, tapetum lucidum. What is this? It is a layer of guanine crystals, riboflavin (in lemurs) or collagen fibres located behind the retina that reflects light, helping more light to be absorbed.
Interestingly, for primatologists, lack of this layer is quite a nuisance. It is this layer which helps researchers during any study or inventory, because any light that falls on most nocturnal primates makes their eyes almost shining, golden in colour. To summarise – the lack of the layer described above makes any of the methodologies used in other nocturnal primates, inapplicable to tarsiers. In addition, these little primates live solitary lives, or in small groups (depending on the species), which makes locating them even more difficult.
Threatened species
Many tarsiers species cannot be classified in terms of their threat status on the basis of surveys. If we do find such data, these are usually only estimates. This is due to the aforementioned lack of an effective survey methodology. What is undeniable, however, is the fact that the habitat of tarsiers is disappearing at an alarming rate! On the island of Bohol, for example, where I have been involved with for several years, there is not a single square kilometre of original forest left. Sadly, things are not much better on other islands in Southeast Asia.
Poaching is another huge threat to tarsiers, especially the Philippine tarsier. These adorable species is a desirable pet for wealthy westerners and the more affluent residents from their countries of origin. Despite the fact that tarsiers are protected by the governments of the 4 countries where they are found, and the areas where they live are often national parks or some other type of protected area, enforcement of penalties for breaking any paragraphs is extremely rare. Unfortunately, in addition to the above, tourism is a very big problem for the Philippine tarsier. These primates are shown to tourists in so-called sanctuaries on the island of Bohol. Unfortunately, they do not reproduce there and often die much earlier, making it necessary to acquire new individuals from the surrounding forests and, if they are in short supply, from further regions.
Rebuilding the population of tarsiers
The tarsiers reproduction also works against them. Most of the time, they give birth to only one offspring per year. Unfortunately, the mortality rate among the little tarsiers is high, sometimes compared to that of rodents. For these reasons, for example, when as a result of a natural disaster (such as an earthquake or typhoon) the population is decimated, it will take a very long time to rebuild the original population.
Because of all of the above, the project I worked at aimed at creating husbandry guidelines for those centres where Philippine tarsiers can be seen. Of course, this is not a perfect remedy to halt population extinction. A multi-dimensional approach is needed. Firstly, in order to develop a good conservation strategy, we need data on the species and these are scarce. Secondly, the tarsiers are little known even to the local population, which may lead to their unnecessary capture. In addition, we should aim to turn away from mass tourism, all the more so in the desire to see the wild animals at all costs, even in places with questionable conditions for the tarsiers.
Thus, upon my return from the Philippines, I decided to set up the Kahibalo Foundation, which would study Philippine tarsiers, educate both Filipino children and adults on them and also promote a more sustainable approach to tourism.
Author: dr. Filip Wojciechowski (Kahibalo Foundation)
