Our current knowledge of the endemic mammals of the Solomon Islands Archipelago

Dr Tyrone Lavery gives us an insight into the research methods and identification of bat and rat species in the Solomon Islands.

Dr Tyrone Lavery has been studying small mammals in the Solomon Islands for the last 5 years. Tyrone’s initial studies indicate that the biodiversity of mammals, specifically bats and rats, is quite diverse. Many are endemic (they are found only in the Solomon Islands and nowhere else on earth). The further information to be gained from this region in the areas of biodiversity and conservation is the primary purpose of this last week’s Solomon Islands Archipelago Workshop, in which Tyrone is bringing his expertise to the table.

Tyrone details an interesting array of mammals that call the Solomon Islands home. Some of the most fascinating are the endemic bat species, including the Woodford’s Blossom Bat (Melonycteris woodfordi), Fardoulisi’s Blossom Bat (Melonycteris fardoulisi), Giant Leaf-nosed bats (Hipposideros dinops), and various flying fox species like Solomons Flying-fox (Pteropus rayneri) and the Dwarf Flying-fox (Pteropus woodfordi), which is one of the smallest flying-fox species in the world. Many aspects of their ecology makes them highly interesting, like their varied preferences for food, shelter and company. Some bats choose to indulge in nectar and pollen, and during the day rest as individuals, while others prey on insects and roost only in undisturbed forests with many others of their kind.

Morphologically, huge variations exist both within and between genera of bats in the Solomon Islands Archipelago, although some are still difficult to tell apart. Interesting adaptations exist in these bats including the ability to switch their metabolism rate in order to conserve energy, and some have spectacular colouration that helps them to camouflage by resembling a dead leaf.

Rats are the other major mammal grouping that calls the Solomon Islands home, and many of the species found there are also endemic. Tyrone has also done some work on these animals, being able to share his extensive knowledge with other members of our workshop group who will be focussing on assessing the distribution of these mammals at the cessation of the workshop.

Both endemic and introduced species of rats vary morphologically, some being large in size, while others are small and have differing ratios between body size and tail length. Methods in the collection of specimens and data are another area that Tyrone has been able to share his expertise. For bat surveys, Tyrone uses mist nets which are strung between two trees or set up between two long vertical poles. Rat survey methods include setting up camera traps that are triggered by movement in the forest, and bait stations are also used to attract animals to the camera traps, which are set up at knee height with the bait stations set a few metres away. The sensitivity of the cameras is set to high, where it will take 5 pictures in quick succession after being triggered. These special cameras have detection bands, that use a heat differential and movement to trigger the camera.

Cats are commonly photographed by the camera traps, along with wild pigs and flightless birds. Rats can be hard to spot in the undergrowth at night time, however this problem can be remedied by looking out for signs of the animal’s presence in the area. Ngali nuts are often found chewed at the base of trees, however these are most likely not the native rodents but instead the introduced Pacific Rats (Ratus exulans), which is indicated by the width of the incisor marks on the hard surface of the nuts. We can also look at what owls (commonly barn owls) are eating in the bush, their regurgitated pellets indicate whether rodents have been part of their diet as they cough up the entire skeletons after eating the animals whole.

Tyrone’s expertise in this area of research has been highly beneficial for creating innovative and appropriate methods for carrying out distribution and taxonomic surveys in the region. Our workshop attendees are now equipped with a variety of new information and ideas to assist them in conducting their own research back home and engaging with their local communities to educate them on the importance of conserving their native animals and the environment.

Alexandra Nuttall, AMRI

More Information

• Lavery, T. H., Olds, A. D., Seddon, J. M. and Leung, L. K.-P. (2016), The mammals of northern Melanesia: speciation, ecology, and biogeography. Mammal Review, 46: 60–76.