Oligocene (Pt 12): Reign of the Hyena-Cats

Apterodon

In most parts of the world today, all large, carnivorous, land-dwelling mammals are members of the order called, appropriately enough, the Carnivora. This is the group to which cats, dogs, and bears belong, along with many other animals from weasels to seals. If we go back far enough in time, we find that this group originated on the northern continents and was unable to reach the then-isolated southern ones until much later. During the Oligocene, therefore, there were no carnivorans in Africa.

Which isn't to say that there were no carnivorous mammals at all; absent some non-mammalian predator to out-compete them, it's just too useful a niche for nothing to evolve to make use of it. But those mammals were not close relatives of the lions and hyenas that live there today, belonging to different branches of the mammalian family tree.

The Spikiness of Tenrecs

Being a small mammal (or, indeed, any other kind of animal) can be tough; there's always something out there that wants to try and eat you. There are a whole host of adaptations that animals use to try and avoid this fate. Running fast and being good at hiding or camouflage are, perhaps, the most obvious and widespread defensive methods. Another approach is to live somewhere that it's really difficult for most predators to find you, such as spending your entire life in an underground burrow.

Fighting back, as larger horned animals might do, generally isn't so effective, although skunks (for example) have certainly found a way of doing that. But there is also the option of body armour. It's something we see quite a lot in reptiles and, in living mammals, it's perhaps best developed in armadillos. But body armour doesn't have to be a bony or keratinous shell, for something that wants to avoid being eaten, spines can also be an effective deterrent.