Juggling Your Time

Qinghai Lake

It's not just humans who have to juggle their lives. Clearly, it's important for any animal to spend some time looking out to see if there are any other animals coming that might want to eat them. But you can't spend all your life watching, because there are so many other demands on your precious time.

A particular problem for herbivores is that they have to spend so much of their time just eating. It does depend exactly what it is that they eat; if their diet consists largely of something highly nutritious, such as fruit, it may not be much of an issue. At the opposite extreme, browsers have a particularly tough time of it, because grass isn't especially nutritious, and takes a lot of time to digest. And you can't scan the horizon for predators while your head is down on the ground. Furthermore, while many herbivores spend much less time sleeping than carnivores do (consider how much time a cat spends kipping), they do have to rest at some point.

These problems become particularly acute during the winter. The food, such as it is, is even less nutritious than usual, and the carnivores are going to be especially hungry as well, which might lead them to take on prey they wouldn't otherwise. But it's more than that, because, for many large herbivores in the temperate regions of the world, winter is also the time for mating. That ensures that it's spring by the later stages of pregnancy, and when the young are still being suckled, and the mother needs the most food. But it does mean that, just when food is short, and predators are about, both females and males have other things on their mind than keeping watch.