A Brief History of Zokors

The rodents are the largest group of mammals, in terms of number of species, and they are divided into several families. Some of these are familiar, such as the mice, voles, squirrels, and gophers, but others are much less so, at least to the majority of people in the West. This includes, for example, the zokors.

There are a couple of reasons why zokors are not as well-known as some other rodent groups. For one thing, they only live in northeast Asia, an area that it's fair to say doesn't receive much attention in the Western world. For another, even if you did live there, you wouldn't see them very often, because they are burrowing animals that don't like coming to the surface if they can help it. Rather like moles, you might see the mounds of earth they leave, but not often the animal itself.

Out of Your Hole

Many animals dig burrows. They can be used for shelter when sleeping, or as a safe place to raise young and, while they may take more effort to construct than finding a natural rock crevice or hiding beneath a log, it's often worth it. Especially if you happen to live in an environment - open grassy plains, for example, where such alternatives are hard to come by. Although, admittedly, this does tend to apply only if the animal in question is small; not only would it take more effort for a large animal to dig a burrow, there's less that's likely to eat it, and it would be harder to hide the entrance anyway.

But some small mammals go further than merely digging burrows to sleep in. They spend almost their entire lives underground, being able to feed off earthworms, roots, and the like. It's a peculiar environment to live in, entirely lacking in light, and requiring constant work to maintain, as well as often being low in oxygen. But it is undeniably safe, not just from most predators, but also from inclement weather (so long as you're not somewhere that's prone to flooding). 

A History of the Bamboo Rats

In terms of number of species, the mouse-like rodents are the most successful group of mammals alive today. The group is typically considered to consist of six families, with the vast majority of species crammed into just two - the mouse family itself, and the cricetids, which includes the voles and hamsters. These, however, are relatively late arrivals, and there are two families that split from the main line of mouse-like rodents long before the ancestors of the mice and voles diverged from one another.

One of these consists of a grand total of three species (maybe), living in the forests of southern Asia. The other goes by the technical name of the Spalacidae, and it consists of animals that have the rather unusual trait of spending almost their entire lives underground. There are at least 35 species of these animals, found in various places across Europe, Asia, and Africa. This is a fairly wide distribution, which raises the interesting question of how they managed to spread that far when they seem to have fairly narrow habitat preferences. Until recently, the evolutionary history of these oddities has been something of a mystery but now, it seems, we are starting to get enough information to piece together an overview.

Does Colder Mean Bigger?

Amne Machin, Qinghai

In 1847, German biologist Christian Bergmann formulated what has since become known as Bergmann's Rule. Over the following 165 years, the Rule has been somewhat modified and re-interpreted from Bergmann's original statement, but a common modern version is that warm-blooded animals tend to be larger the colder the environment they live in. Bergmann was originally thinking of closely related species; for example, polar bears tend to be larger than most brown bears. However, the rule is now often applied to individuals and populations within species; for instance, Siberian tigers are larger than those that live in the tropics.

The rule has, as I've noted before, been the focus of some controversy. Is it, in other words, actually true? Certainly, there are many counter-examples - snow leopards are the smallest cats in their genus, for example. But are these rare exceptions to a general rule?