We're Up All Day to Get Lucky

One of the key characteristics that's often listed for the behaviour of a mammal species is what time of day it tends to be active. There are four basic options here, of which the most obvious are diurnality and nocturnality. The others are crepuscularity if it's most active around dawn and dusk but not in between, and cathemerality if it really doesn't care - often because it lives underground. But, either way, it's natural to assume that this behaviour is relatively fixed in an animal; either it's nocturnal or it isn't.

In reality, however, it turns out that this can have a lot to do with the circumstances. And, in the modern world, those circumstances are most likely to be shaped by... what else, but humans? 

The issue, of course, is that humans are for the most part diurnal. Which isn't much of a problem for animals that are naturally nocturnal, but can be if they, too, would prefer to be active during the daylight hours. What we see time and time again across the world, and across different mammal species, is that where humans are most likely to encounter wild animals, those animals shift their behaviour towards nocturnality to avoid the stress of meeting us too often.

Skunks of the World: Spotted Skunks

Eastern spotted skunk

At least outside of the Americas, the most familiar species of skunk is the striped sort and, as I mentioned last time, even scientifically speaking, this is the animal that defines the skunk family. It's perhaps surprising then, to note that, despite it also being very widespread and highly visible, it wasn't the first species of skunk to be named.

That honour goes to the spotted skunk, which appeared in the earliest recognised list of scientific animal names in 1758. This isn't to say that nobody knew at the time what a striped skunk was, merely that the naturalists of the day had yet to identify them as something distinct from the spotted sort, and it was the latter that happened to be described first - the striped skunk followed less than twenty years later, in 1776. Before they were given their own genus, both species were originally placed in Viverra, which comes from the Latin word for "ferret" but seems to have been used for any small, slender mammalian carnivore that didn't fit elsewhere (not including, ironically, the ferrets). 

Oligocene (Pt 4): Time of the Giants

Paraceratherium

The Grande Coupure saw many new animals pouring across from Asia into Europe. Whether or not the tapirs were among them is not immediately obvious. The oldest tapir that we know of is a fossil discovered in Germany and dated to the early Oligocene, not long after the Coupure. Named Protapirus, we know that it, or its very close relatives were found not only in Asia, but also North America, by the second half of the epoch and managed to survive, with relatively little change, into the Early Miocene that followed, dying out about 20 million years ago. 

At first glance, since the oldest fossil is German, it appears that tapirs originated in Europe and then spread east, and it's purely a coincidence that they happened to do so after the Coupure - which, after all, was a time of climatic change. The problem is, there wasn't anything remotely tapir-like living in Europe before the Coupure, but there were plenty of potential ancestors elsewhere. So it's perhaps more likely that the first true tapirs were Asian, and we simply haven't found their fossils yet. Even so, we can at least say that Protapirus, and its later relative Paratapirus (which never seems to have left Europe) really were tapirs, rather than some close relative. A key feature here is that, unlike their earlier relatives, they already had the modifications to the nasal bones that suggest the presence of the short trunk that modern tapirs have, although it was probably less prominent than in current species.

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". 

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.

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. 

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.