Small British Mammals: House Mice

Over the last few years, I have done a roughly annual series covering particular groups of mammals, exploring all the different species, familiar and unfamiliar, that belong to them. (If you haven't read the past ones, the link "Synapsida Series" points to the list of them; note that the individual posts appear in reverse chronological order once you select a series to view). One problem with selecting which groups to cover in a given year is that only some groups will really work, and, even then, some are clearly better than others.

One problem, for example, is that some groups are simply too large, and if you split them down into narrower groups that are more easily handled, there's no longer enough variety for it to be worth it. Such is particularly true of small mammals. There are over 700 species in the mouse family, for instance, with over 500 of those in the "murine" subfamily, which includes all of the familiar ones. Even if it would be practical to describe them all, most of the individual species haven't been studied in any detail, so you'd rapidly get a long list of "looks mouse-like, lives in XX".

Murderous Whales of the Eocene Oceans

The relationships between what animals eat can be thought of as a pyramid. At the bottom are plants, which are eaten by herbivores, which are eaten by carnivores, which are eaten by larger carnivores. The reality is much more complex, and is more accurately thought of as a web (omnivores exist, large carnivores also eat herbivores, etc.), but the general principle is broadly true. In particular, the further up the ladder you go, the fewer animals there are, since the transfer of energy from one level to the next can never be 100% perfect.

At the top of the pyramid are the "apex predators". These are the carnivores that have no predators of their own, that are able to feed without fear of being eaten themselves. Again, the reality is more complex - an adult of one apex predator might occasionally kill and eat the young of a different kind, for instance. And, of course, everything gets eaten by worms (or whatever) once they're dead. Nonetheless, really big scary predators clearly do exist, even if, by their nature, they aren't very common.

Requiem for a Dolphin

Dolphins are social animals, living in pods and engaging in what seems to be fairly sophisticated communication. It's likely that such behaviour is part of the reason for their success, with well over 30 species spread across the world's oceans... and that's excluding porpoises, and some other "dolphin-like" animals outside the dolphin family proper.

Sociability involves a number of different traits and behaviours, but one that's known to exist in cetaceans and relatively little else, other than primates, is what's technically known as epimeletic behaviour. This is, in essence, the act of helping other members of your species when they are in trouble, typically due to an injury of some kind. (For what it's worth, this compares with etepimeletic behaviour, which is acting in such a way as to make it easier for others to care for you).

Gerbil versus Rattlesnake

Sidewinder

Deserts are harsh environments, and living in them poses animals a number of problems, not least of which are daytime heat and an absence of water. In order to survive in such a place, animals need to evolve suitable adaptations - extremely efficient kidneys to reduce water loss are one such example.

But the thing about deserts is that, while there are some geographic differences between them, the challenges of living in one are at least broadly similar regardless of which desert it happens to be. And while, say, the world's seas are all connected, the deserts aren't. So animals, including mammals, have had to evolve means of surviving in them several times over, re-developing the necessary features each time they encounter a new one.