South Africa, 14,000 BC

Paleoecology is the study of how animals and their environments interacted in the distant past. While the basic idea has been around almost since we started the scientific investigation of fossils, it really only became a field in its own right around the 1950s. That's largely because it isn't easy, becoming harder the further back we go.

The basis of the field is to look, not at individual fossils, but at the whole array of fossils at some particular site, correlating them with what we can determine of the climate and environment at the time. Which, among other things, requires a good understanding of exactly what that time was and at least a reasonable confidence that the fossils in question are all around the same age. Often, it relies not just on good and plentiful fossils at a particular site, but on us being able to say what the animals' lifestyles were. Which is a lot harder for those that don't resemble the ones we have today - dinosaurs being an obvious case in point.

Hungry Hippos

The hippopotamus (Hippopotamus amphibius) is an unusually large animal. Among land-dwelling mammals, only the elephants and some species of rhinoceros are larger. It is also, like elephants and rhinos, herbivorous and, since it prefers to eat plants that aren't especially nutritious, this means it needs to eat a lot. 

As in, it eats 35 to 50 kg (77 to 110 lbs) of food each day. 

Which is fine if the hippo happens to be out in the wild, far from human interference. But the reality is that there are fewer and fewer such places around these days. It's not so much the urban sprawl that humans bring, or even the roads and other infrastructure of an expanding African economy, but more the cropland that's required to feed us all. Although hippos are hunted for the ivory in their teeth, the number one threat to their survival is probably the expansion of farmland. Compared with many other animals, this is exacerbated by their reliance on large amounts of fresh water, so even if the farmland isn't near them, they suffer if water is diverted to where it is needed for crops. 

Bats in the Belfry

Mammals, like other animals, need a safe place to sleep. For large animals living in herds on the open plains, safety in numbers may be the best they can do, with some keeping guard while the others perhaps try to hide in long grass. Hiding in trees or sleeping on rocks out in the ocean are valid options for those in the right habitat. For many others, however, especially the smaller ones, some kind of den, nest, or burrow provides just the ticket. In the case of bats, we have roosts.

When it comes to bat roosts, it's likely that most people initially think of caves. Caves can hold communities of thousands of bats, often with many different species sharing the same one. Caves are ideal roosts for bats, because they provide a stable environment safe from the weather, few predators will enter them, and, when you're nocturnal anyway, you don't care that it's dark. 

Delphinids: Pilot Whales

Long-finned pilot whale

The term "dolphin" is not, strictly speaking, a scientific one. It refers, in common parlance, to any small cetacean, often even including porpoises. Even ignoring the porpoises, however, not all dolphins are members of the dolphin family, technically referred to as "delphinids". This is because some freshwater animals are not closely related to the dolphins proper (or, indeed, to the porpoises). We call them "dolphins" because they're about the right size, a similar shape, and... well, we don't have a better word, at least for them all collectively.

But it works the other way, too. Not all members of the dolphin family are commonly called "dolphins". With the exception of the melon-headed whale, which it's hard to think of as anything other than a dolphin, this is because they're too big. We call them "whales" - another term that doesn't map to anything scientifically - since that's what we call any large cetacean.