Grumpy Old Voles?

Meadow vole (a related species)

It should go without saying that the behaviour of young mammals changes as they approach, and eventually reach, adulthood. Obviously, there's the development of the mating drive, but there are also social changes, as the animal gains independence, first from suckling, and then more generally from its parent(s), often leaving home, whether to live alone or to find a new pack where its potential mating partners aren't also its own siblings. 

Drawing parallels between these changes and the way that humans develop isn't without risk; the complexity of our society, the existence of culture and so on significantly colour how we behave. But that's not to say that such parallels don't exist, and can't tell us anything, even if it's only how we evolved. We are, after all, still affected by our biology and evolutionary history in at least some respects. For instance, it's notable that exactly how animal pups are raised by their mother can affect how they behave as adults, even if the details are going to be less complex than they are with human child-rearing.

Broken Bones and Missing Toes

Woodland jumping mouse

Life can be hard, especially out in the wild. Injuries can be common, and among the most painful are broken bones. As humans, we can mitigate bone fractures using splints, braces and so on, but wild animals have no such luxury. Nonetheless, bones do heal by themselves, a process that starts with the formation of a tough fibrous scar at the injury site that at least helps to keep things fixed partially in place. Over time, the scar is mineralised to form weak, but functional, bony material, and then eventually rebuilt with as much of the original structural integrity as possible.

Without splints and braces, this is likely to be an imperfect fix, even assuming that the injury doesn't prevent the animal from feeding or otherwise kill it before the process completes. If the animal does survive, the signs of the injury are always going to be there in its skeleton, and are quite likely to cause at least some ongoing problems. But, survive they do, and bone healing wouldn't have evolved in the first place if it never worked in the wild.

How Mothers Stop Their Daughters from Sleeping Around

Northern mole-vole (E. talpinus)

Generally speaking, mammals are equally likely to be born as either males or females. The exact proportion may vary a little, and it doesn't follow that both sexes form 50% of the adult population, because one or the other may be more likely to die young. It's even less the case that all males, or all females, are equally likely to pair up and have offspring of their own.

This disparity is known as reproductive skew, and it varies considerably between species, and sometimes even between populations of the same species. At one extreme, it's essentially zero. This happens if the species is basically monogamous, usually because child rearing is a sufficiently draining exercise that being able to share the duties between two individuals is really helpful. It can also happen for what might be regarded as the exact opposite reason - if the species is highly promiscuous so that the females will mate with absolutely anyone, once again, everyone's chances of reproducing are the same. There's just less of that courtship stuff to worry about, off-set by having a single-parent family once you're done.

What is a Subspecies?

Microtus californicus californicus

I've often mentioned in past posts the difficulty of defining what a "species" is. This, despite the fact that, of all the taxonomic ranks, it's supposed to be the one that comes closest to actually having an existence in the real world. Although there are strict rules about how we name, for example, "families", quite where we draw the lines to separate those families from one another is arbitrary. We could place raccoons in the weasel family, or we could place American badgers outside that family, but, purely for the sake of convenience, we choose to do neither of those things. (For what it's worth, though, the rules would prevent us from doing both).

But a species is meant to be an actual thing, right? Certainly, when the word was coined by Linnaeus (in the biological sense; it has older meanings, too) in the 18th century, that was his intent. A hundred years later, Darwin elaborated on the term, realising, as earlier evolutionary theorists had, but Linnaeus hadn't, that species do slowly change into new forms over time. Today, the most common understanding, outside of scientific circles, is that two animals belong to different species if they can't interbreed to produce fertile offspring.

Do Voles Climb Trees?

A great many species of mammal (and, of course, other creatures) live up trees, spending as much of their lives up in the branches as they can. This is true of the great majority of primates, for instance, which might travel along the ground if they have to get between two trees that aren't very close to one another, but, by and large, would prefer not to descend if they can help it.

The technical term for an animal that climbs regularly is scansorial. Not all scansorial animals are actually arboreal - that is, spending their lives in trees. Many of them live on the ground for much of the time, but will climb trees to, for example, escape from something that's chasing them. So it' perhaps not surprising that scansoriality has evolved many times, and that the physical adaptations associated with climbing are seen in many different, often relatively unrelated, mammals.

Indeed, there are good grounds to suppose that many of the earliest mammals that we know of were at least scansorial, if not fully tree-dwelling. These are the archetypal small shrew-like animals that hid in the trees out of sight the dinosaurs, just waiting for the asteroid to strike so that they could take their turn. (The reality is, of course, more complex than that - but it isn't entirely untrue, either).