Sunday, 12 January 2020

Voyage of the Kinkajous

For much of the time since the extinction of the dinosaurs, South America was an island continent. Developing in isolation, the mammals living there developed a number of unusual forms not seen elsewhere. Around 2.8 million years ago, however, South America became joined to its northern counterpart via the Isthmus of Panama. Northern animals flooded south, and relatively few headed in the opposite direction. As a result, unlike Australia, which remains an island continent today, the mammalian fauna of South America includes many animals at least broadly familiar from elsewhere.

Among the first mammal families to make the crossing was that of the raccoons. Although this had first appeared in Asia, living species are now found only in the Americas (ignoring some recent man-made introductions) with most of them found in tropical habitats. In fact, they reached South America almost ridiculously early, something we know because we have a fossil example that's around 7 million years old... at least 4 million years before the land crossing we'd expect them to have used had formed.

Sunday, 5 January 2020

Digging in a Winter Wonderland

Humans have a somewhat ambivalent attitude to snow, greeting it either with joy and wonder or with concern and frustration, in large part depending on how old you happen to be. It decorates Christmas cards, covers the countryside in pristine white, and provides plentiful opportunities for play. On the other hand, it makes travel difficult, and may even interrupt deliveries of food, making our lives awkward. (Plus, if you're in a city, it may not stay white for very long).

If heavy snow makes it difficult for us to get around and obtain sustenance, the same obviously goes for animals that live in the relevant parts of the world. Different species have different strategies for how to cope with its arrival. Some hibernate, while others avoid the problem by migrating somewhere else for the winter, but there are, of course, a number of species that simply have to put up with it. Those that live particularly far north may even have to do so for over half the year, and the difficulty of doing this is probably at least part of the reason why relatively few species do.