An unprecedented study on bats

At about 1000 m above sea-level, the temperature drops at night and by 7 pm most of the research team, comprised of Dahari ecologists and students from the University of Comoros, are already wearing warm pullovers. To be honest, the cool is quite a relief from the temperatures we experience during the day in the city – the rainy season here on Anjouan is hot and humid!

This night we have pitched our tents on a plateau north of the village Adda, close to a very important roost and feeding site of Livingstone’s fruit bats, one of the rarest and biggest bats in the world. They are also the reason why we are here in the first place: Dahari and the University of Comoros have initiated a research project to find out where the bats go and how they use their habitat with the ultimate goal of finding better ways to protect them from extinction.

The bats are threatened with one major human-caused crisis – the destruction of the natural forest habitat. They rely on large trees in forest areas to roost during the day. A roost site can be comprised of multiple trees and are important for social contacts and undisturbed rest. We know where all the main roost sites are on the island of Anjouan and Dahari is working hard together with local landowners to protect these trees. However, roost site protection, while crucial, is not the only way to help this species recover: feeding sites are also key sites for protection! But as only very little knowledge exists on where, when and what Livingstone’s fruit bats eat, so, with support from CEPF and the Rufford Foundation, we launched the world’s first GPS tracking study of these bats!

In addition to finding out about   feeding sites we are planning to understand better how the bats cope with the fragmented landscape. In Anjouan only very little natural forest is left and the forest fragments are often located on steep slopes and are far apart. Luckily for them, big bats can fly long distances. The fields and plantations also still offer some trees for a tired bat to rest in, but previous research has actually shown that fruit bats do not like staying in open spaces – we will see what Livingstone’s fruit bats do here on Comoros!

In January and February 2019, we attached GPS tag collars on two individuals: one female and one male. The GPS tags record their movements in great detail and also give us information on how fast the animal is moving when the points are taken. One slight difficulty: we have to find the bats again to download the data from the tags! So, for the first two weeks after we attached the tags, the Dahari ecology team was busy searching in the terrain around Adda, Outsa, Ouzini and even Moya for the bats. Luckily, we found them after a few days and the first data we have already shows us where they like to spend their days which has helped a lot. Now we simply go to their preferred sleeping trees during the day and download the data!

The GPS collars are lightweight and the big bats can carry them easily. Each collar weighs 20g and with an average weight of 630 g per bat, they don’t pose any problems for the animals. In addition, we devised them in such a way that they will fall off after about six to eight weeks. That will leave the bats undisturbed and we can then hopefully recover the GPS tag and re-use them in the future!

Both bats are very active individuals and from the first week onwards Dahari was able to include places they visited frequently into the participatory monitoring project: the people monitoring the state of the habitat will focus on areas that the bats use often. The next step is to identify the feeding sites (the ecology team will need to go into the field again to find out the tree species!) and then open a dialogue with landowners to discuss possibilities of protecting them.

Meanwhile the bats will fly about and as long as the battery lasts on the GPS tags, they will continue to give us more information on their lives! We are looking forward to seeing where the bats go next!

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