Sunday 27 August 2023

Picking the Right Crevice

It's probably fair to say that bats are commonly associated with in the public mind with caves - there's a reason that Batman's base of operations has been described as a cave since just a few years after his debut. There are good reasons for bats to sleep in caves during the day. Especially in temperate regions, bats keep warm at night by actively flying but, just as it's handy for other small mammals to sleep in burrows, when they sleep they need somewhere that's both secure and has a decent temperature. Even so, to help keep down their energy expenditure many bats in temperate regions enter torpor at night - at a state that's deeper than regular sleep, lowering the animal's body temperature significantly so that it's more like a form of short-term hibernation.

The problem with caves as a habitat, however, is that, in the grand scheme of things, they aren't all that common. Clearly, this depends on the type of landscape you're in, but many places just don't have lots of caves. In the tropics, hanging from a tree branch might well be sufficient, but where the weather is cold, especially in winter, that may not be such a good idea. So bats roost in many other places, too, such as hollows in trees and cracks and crevices in the ground that are similar to, but much smaller than, what we'd normally think of as a "cave". 

Sunday 20 August 2023

Love on the Mountain Tops

Caprines - members of the goat subfamily - are amongst the mammals most adapted to harsh environments, with the majority of species adapted to living in the cold, barren, and precipitous slopes of mountains. There are some exceptions; sheep (which are taxonomically a subtype of "goat") originally evolved to live in barren rocky hills rather than on true mountains, while some of the East Asian species inhabit forested slopes. 

There are, as with many animal groups, more species of caprine than one might at first think, and I covered them all individually about ten years ago. Looking through that series, it should be possible to appreciate that the group is also varied, not only inhabiting a range of environments but also living varied lifestyles, from those that are near-solitary to those that prefer large herds. This is also reflected in their mating habits which, are as one might expect, related to the size of the community in which they live. One would also expect that the habitat would have some effect on how the animals choose to live, and, in turn, on that mating behaviour.

Sunday 13 August 2023

Skunks of the World: Striped and Hooded Skunks

Striped skunk
It's probably fair to say that when most people think of "skunks" the first animal to come to mind is a black, cat-sized creature with white stripes down its back and a bushy tail. That certainly seems to have been the case for Charles Bonaparte when he first erected the skunk family in 1845, since that is the animal he named it for. More accurately, the type species of the type genus for the family - in a sense, the defining species against which all other skunks are compared - is the striped skunk (Mephitis mephitis). The fact that it has that doubled ("tautonymous") name suggests that, back in 1795, when they named the genus itself, Geoffroy and Cuvier thought much the same thing.

It's hardly surprising; the striped skunk is the most widespread and common of all the species of skunk and surely the most familiar to most North Americans and hence, indirectly, to most Europeans. (For what it's worth, while all the naturalists named above were French, Bonaparte had at least spent a few years working in the US, and was probably much more familiar with skunks than his predecessors). Indeed, the striped skunk lives across the whole of the contiguous US, save only the Mojave Desert and the Great Basin of southern Nevada. It's also found across most of southern and central Canada, and, being no respecter of the US Immigration Service, also into northern Mexico. 

Sunday 6 August 2023

Not-Quite Placentals of the Gobi Desert

I have sometimes been asked whether marsupials count as mammals. The answer, of course, is "yes" but the question illustrates a possible point of confusion among some people. It's not that they think marsupials are reptiles, or whatever, but more likely that they lack a word for "placental mammals" and blur the concept of those animals with mammals more generally. Given that, sometimes, the scientific definition of a group doesn't match the vernacular one, it's actually not an unreasonable question. After all, the marsupials (and the egg-laying monotremes) are outside the placental mammal group; a different sort of animal, albeit a related one that, due to such features as their production of milk, does, officially, belong to the same class.

The great majority of living mammals species are placental mammals, the marsupials representing what is, today, a comparatively small side-group. They are distinguished by the young gestating in the womb for a comparatively long period of time, taking in nutrients through a fully-formed placenta. There are other features that unite them, too, such as the basic number of teeth, although these are often obscured by the considerable evolution and change of form that has occurred in some placental groups to create animals as diverse as horses and dolphins.