Being separated from all other land masses since the late Cretaceous, when dinosaurs still dominated many parts of the Earth, Madagascar has long been referred to as a "natural laboratory of evolution". Its long isolation resulted in unique fauna and flora, most of which have evolved in place.
Madagascar only has four groups of endemic land mammals: primates (lemurs), rodents, Afrotheres (formerly insectivores such as tenrecs), and carnivores. Yet there's huge diversity within these four groups.
When it comes to endemic terrestrial carnivores, there's only one group that is recognised: the Eupleridae. Of these, the largest is the fosa. This is neither a felid (cat family) nor a canid (dog family). It is closely related to the mongoose and weighs between 5 and 10 kg. It has long been the primary mammalian predator of lemurs and other Malagasy mammals.
So, the conventional view is that Madagascar has no native cats (i.e. felids). Yet, cats are plentiful on the island.
There are two general types of cats in Madagascar: village cats, and a wild "forest" form. This "forest cat" has long been distinguished by the Malagasy from village or feral domestic cats and is often viewed as a threat to domestic animals such as poultry. Given eye-witness accounts and reports - including our own - this little understood, wild "forest cat" is also an effective predator of Madagascar's famous lemurs.
The "forest cats" are quite distinct in their outward appearance, consistently having a "tabby" or striped fur, longer legs, and a larger size (up to 5kg).
In contrast, "village" cats generally look like domestic cats seen around the world - a solid fur color (often white), shorter legs and a body size of about 2kg.
The external morphology of the forest cats is thus very different from the village ones. It's also quite similar - on the surface - to the African wild cats seen in eastern and southern portions of continental Africa.
Therefore, the origin(s) of Madagascar "forest" or "wild" cats has long been a mystery. Are they descended from the African wild cat (Felis lybica) arriving with East African pastoralists, who culturally dominate Madagascar's southern regions? Are they a product of recently arrived domestic cats (Felis silvestris) from Europe, the Arabian realm or Southeast Asia?
To determine the origin(s) of Madagascar's "forest cats", we and our colleagues, carried out this study.
Our findings reveal that Malagasy "forest cats" are descendants of cats from the Arabian Sea region. They did not originate from continental Africa's wild cats and are instead related to domestic cats.
Our team - a collaboration between scientists from six countries across three continents - collected genetic data from 30 "forest" cats at two locations in Madagascar, three individuals from the Bezà Mahafaly Special Reserve in the southwest, and 27 individuals from Ankarafantsika National Park in the far north of the island.
These data were compared with approximately 1900 samples from various domestic and wild cats across the world, to assess the degree of relatedness of the Malagasy wild forms.
The data produced by our team - combining the expertise, experience and skills of both field and laboratory scientists - revealed that the Malagasy "forest cats" most closely cluster with domestic cats specifically from the Arabian sea region, including the Kenyan islands of Lamu and Pate. The Malagasy cats are thus descendants of domestic cats from the Arabian Sea region and not continental Africa's wild cats.
When and how did this diaspora begin? The Arabian Sea and Kenyan Islands cats likely made it to Madagascar over the past millennium, or slightly earlier, by way of the Arabian sea trade. There were several waves of migration to Madagascar from the Arabian realm over the past 1000 years or so.
These migrations brought architecture, linguistic components, and eventually a written script by the 18th century. And, they brought cats. Thus, Madagascar's "forest cats" are oceanic migrants from elsewhere - as with Madagascar's other terrestrial mammals, albeit via a human source rather than natural "rafting" processes, such as the ancestors of Madagascar's lemurs.
Study or eradicate?
What does this new information mean for these felids? Our results suggest Madagascar's "forest cats" may have been introduced a millennium ago, and if so, studying their behaviour, biology and ecology provides a window into how exotic species adapt to island biogeography, as well as insight regarding cat dispersals.
Importantly, our findings also raise the questions of what these cats' role is in Madagascar's forest ecosystems. Should they be eradicated - at least from protected reserves - as has been done on other islands in terms of introduced species?
The conservation questions surrounding these new data are complex and require thoughtful conversation to understand the whole story of Madagascar's "forest cats".