Sunday, 21 May 2017

Secret Origins of the First Hippos

Hippos are somewhat strange animals. They are large, amphibious, almost entirely hairless animals that are clearly related to the big hoofed herbivores, but do not themselves have hoofs. Still, it came as something of a surprise to everyone when, in the late '80s, it turned out that their closest living relatives were not pigs, as had previously been thought, but whales and dolphins. Which, granted, are also large hairless animals living in the water, but which (among other things) are anything but herbivorous.

Still, while whales and dolphins may be their closest living relatives, the latter have been around for a very long time, and it follows that the hippo lineage must have been around equally long. So, especially given that they aren't exactly small and easy to overlook, it's reasonable to expect that there should be a number of fossil species that are a good deal closer to living hippos than anything we have today.

And, indeed, there are.

Sunday, 14 May 2017

Pinnipeds: Freshwater Seals

Caspian seal
Seals live, generally speaking, in the world's seas and oceans. But, as I noted last time, there is one species of ocean-going seal with a population found in freshwater. This is the ringed seal of the Arctic and Baltic, one population of which became cut off during the last Ice Age and now has descendants living in Lakes Ladoga and Saimaa in Russia and Finland. Lake Saimaa drains into Lake Ladoga, which in turn drains, via the Neva River, into the Baltic, so while seals do not regularly swim in that river, the geographic isolation is, at least in theory, not absolute.

However, two other populations of ringed seals (or their immediate ancestor), became separated from their kin at a much earlier date. Unlike the Ladoga and Saimaa populations, they had the time and isolation to develop into entirely new species, notably different from their relatives out in the ocean.

Sunday, 7 May 2017

Compare the Mongoose

The mongoose family includes over 30 different species, found across Africa and southern Asia. That's excluding a few species of "mongoose" found on Madagascar, which were discovered, back in the last decade, to be more closely related to some of the other carnivores of the island than they were to the "true" mongooses on the mainland. On the other hand, it does include a small number of species that aren't commonly called "mongooses" in English. Ironically, in fact, it's one of these latter that's probably the most familiar of all mongoose species to westerners: the meerkat (Suricata suricatta).

(As an aside, the word "meerkat" is Afrikaans... which is a bit odd, since it means something completely different in Dutch).

Even when they aren't singing Hakuna Matata or trying to sell you car insurance, meerkats are common features on wildlife documentaries (at least they are in Britain; I can't speak for other countries) and in zoos across the world. In part, this is because they're rather cute, sociable animals, with complex, telegenic, lives that involve a lot of cooperation. But, while meerkats are probably the most social of all mongooses, they are by no means the only ones. Another example, for instance, is the banded mongoose (Mungos mungo), which lives in groups almost as large as those of meerkats.