Sunday 30 June 2024

Cubs in the Snow

Both brown and American black bears spend much of the winter asleep. Whether this counts as true 'hibernation' is debatable, although, in recent years, most scientists no longer insist on a strict physiological definition, having given in and accepted the word as it is usually understood in English. They do this because their food is in short supply during the winter, and spending the entire time snoozing is a good way of conserving energy.

Before hibernating, they construct a den, in which they will spend the next several months, depending on the exact weather conditions. Significantly, mothers of both species give birth in the den, often while they are still asleep. All of which works for a large, omnivorous animal living somewhere that inclement weather makes it hard to forage in winter. But that's not something that will be true of all bears.

Sunday 23 June 2024

Bats in the Daytime

One of the things that we can say about almost all species of bat is that they are nocturnal. Regardless of whether they roost in caves or under the branches of trees, bats sleep through the day, wake up around dusk, fly out to get their food, and return home when the sun rises. But, when you stop to think about it, why should that be?

Consider: the great majority of bats eat insects and, sure there are plenty of insects around at night. But there's hardly a shortage during the day, either. Swallows, robins, and thrushes are all flying vertebrates that eat insects, and you see plenty of those around during the day. While for fruit bats and other herbivorous species, it's quite obviously not going to make a difference. If birds are perfectly happy flying around during the day, why not bats? It's not even as if there are only a small number of bat species that happen to occupy some narrow niche; there are well over a thousand of them.

Sunday 16 June 2024

Antelopine Antelopes: Blackbuck and Springbok

The gazelle-like body form has evolved at least three times within the "antilopine" subfamily, and arguably a few more times among antelopes more generally. A fast-running animal, able to outpace many of its predators, is clearly a useful thing to be if you're a herbivore. Only one of these three evolutionary events led to what zoologists would describe as the "true gazelles", although at least one of the others resulted in an animal so strikingly similar to gazelles that it's surprising that molecular evidence tells us it doesn't have an immediate common ancestor.

The blackbuck (Antilope cervicapra), however, does not look much like a gazelle. It is one of the five currently recognised species of antelope whose scientific name dates back to the origins of modern taxonomy in 1758. In 1766, Peter Simon Pallas first distinguished antelopes from goats, creating the genus Antilope to incorporate no fewer than seventeen species - including the Dorcas gazelle, which would later go on to become the defining species of the Gazella genus when that was created in 1816. While every other living species was eventually split off elsewhere, the blackbuck remained, and its genus gives its name to the entire subfamily. (The second part of the name, incidentally, translates as "deer-goat" and remains the name of the animal in French).

Sunday 9 June 2024

Oligocene (Pt 9): Rise of the Dogs

Many of the carnivorous mammals present in North America during the Oligocene were of types also found in Eurasia. However, this far back in time, they did not necessarily belong to any family of animals we would recognise. Cats, for example, first appeared in Europe at the end of the epoch and did not reach the Americas until much later. Other groups, such as raccoons, simply didn't exist yet. 

But we do, for example, have Palaeogale, an animal also known from Europe that looked somewhat like a polecat, but was actually more closely related to cats and mongooses without, so far as we can tell, being either. Corumictis looked similar, but analysis of the skull has shown that it much closer to true mustelids. About the size of a modern weasel, it lived in Oregon at least 29 million years ago, towards the middle of the epoch. It may make it the first mustelid to reach North America from Eurasia, home to the very similar, and slightly older, Plesictis. It's far enough back that it might, however, belong to an early musteloid group rather than to the modern family (that is to say, it may be equally related to mustelids and raccoons, and thus, strictly speaking, neither). Oaxacagale is almost as old, and lived in what is now Mexico; it's probably another close relative but, it too, has so many primitive features that it's hard to place precisely.

Saturday 1 June 2024

Wombats Moving Home

There comes a time in the life of many young mammals when they have to leave home. There are at least two major reasons for this. Firstly, any given place only has so many resources, so unless your parents die as soon as they've finished raising you (unusual among mammals, although not unheard of), at some point, you have to move elsewhere or there won't be enough food for both of you. Secondly, if the whole family stays together in one place, you'll never meet new sexual partners, forcing you to mate with your siblings - and we all know where that leads.

Understanding how and when animals disperse from their place of birth can be important for conservation as well as, on a broader scale, how new species and subspecies evolve and adapt. Nor is it necessarily something that only applies to young approaching maturity, since older animals may also choose to move from one place to another and often for similar reasons - competition or a lack of suitable mates. Whether a given animal chooses to move home, and how far they travel to do so, can be influenced by several different factors.