Madagascar is a biological wonderland, whose long isolation allowed it to host a staggering number of species found nowhere else on Earth. Northeastern Madagascar is particularly rich. The latest addition to this abundance is the Jonah rat lemur, one of the smallest living primates. Although its conservation status is yet to be assessed, the recent classification of almost a third of lemurs as critically endangered bodes poorly for the new discovery.
Lemurs only live on Madagascar, its forests home to 107 lemur species, a remarkable number when you consider there are around 300 species of monkeys, which have the whole world to roam in. Of these, about 20 are mouse lemurs, distinguished from the other lemurs by their small size.
However, defining a species is not always a straightforward matter, and some scientists allege “species inflation”, saying that what should be considered subspecies have been separated out based on unimportant genetic markers.
To address this Dr Lounès Chikhi of the Instituto Gulbenkian de Ciência and colleagues captured 123 mouse lemurs at five locations and assessed them on a broader array of measures. “Instead of a limited number of genetic markers, we resort to genomic, ecological, and morphological data, together with several sophisticated methods of inference,” Chikhi said in a statement.
Tail length, body size, habitat, and the timing of reproduction all proved particularly useful in distinguishing species from varieties. All the animals were released after being measured.
In the American Journal of Primatology Chikhi and colleagues report some of their specimens had features substantially different from all previously described lemurs, confirming a suspected new species based on genetics. They named the new species the Jonah rat lemur (Microcebus jonahi) after lemur research pioneer Professor Jonah Ratsimbazafy, founder of the World Lemur Festival.
Mouse lemurs are nocturnal and, as their names suggests, tiny. M. jonahi is just 26 centimeters (10 inches) long and the adults weigh 60 grams (2.1 ounces), but it is longer than its nearest relative, M. macarthurii. It also has a shorter tail and wider head and ears than M. macarthurii.
Almost every native of Madagascar is endangered from the combination of rampant habitat destruction, invasive species, and climate change. As lowland inhabitants from northeastern Madagascar M. jonahi is particularly threatened by logging, with the few patches in which it can live so fragmented they may not support sustainable breeding populations. "The loss of natural habitats and the constant change in land use in the region lead to the isolation of small populations and this favors their disappearance," Chikhi said.
Two other species proposed on the basis of genetic markers were rejected as insufficiently distinctive based on anatomy and behavior.