Sunday, 13 August 2017

Pinnipeds: The Mighty Elephant Seals

Northern elephant seal (male)
The largest of all seals are, of course, the elephant seals. These were one of the original species of seal to be scientifically named, back in 1758. They were originally given the name Phoca leonina, which literally translates as "seal-lion", suggesting some possible confusion on Linnaeus's part about which exact animal he was describing. For a long time, it was thought there was only one species, but we now know that the populations in the Northern and Southern Hemispheres represent two different, but closely related species.

Northern elephant seals (Mirounga angustirostris) live off the western coast of North America, with breeding colonies on offshore islands and occasional isolated patches of continental coast in California and Baja California. It's probably here that they are more commonly seen, since they not only spend the winter breeding season ashore, but they also visit the same beaches during the summer for their annual moult, when they are unable to enter the water for weeks at a time. Surprisingly, then, they spend the rest of the year somewhere else entirely, travelling hundreds of miles from their colonies to feed in the north-east Pacific, and spending spring and autumn as far north as the Aleutian Islands and, on occasion, as far west as Hawaii. Quite why they'd do something as seemingly daft as to make the same long-distance migration twice a year isn't entirely clear, although it presumably has something to do with the ideal weather for each activity.

Sunday, 6 August 2017

Bed Time for Wild Hamsters

Golden hamster
After the mice, the second largest family of mammals is the hamster family, with somewhere in the region of 600 known species. The vast majority of these species are, however, not hamsters, and I refer to it as the "hamster family" only because that is the literal meaning of its scientific name, the Cricetidae. Over half of the cricetids, for instance, are "New World mice" visibly more or less indistinguishable from the "true" mice of the Old World. Most of the remainder are voles, and a mere couple of dozen or so are actually hamsters.

The species most people think of when they think of hamsters is the golden hamster (Mesocricetus auratus), which is the animal commonly seen in pet shops. While a few other species are sometimes also kept as pets, most of the varieties named on the basis of things such as hair colour and length are just domesticated breeds of the golden hamster. They are found in the wild only in one relatively small area on the Turkish-Syrian border, just north of Aleppo. Which, right at the moment, does make it somewhat difficult to study their behaviour in their natural environment.

But then, given that there are so many of them in captivity, and that they aren't exactly obscure animals, you might think that we know pretty much all there is to know about them. Certainly, compared with many other species, they are well-studied creatures. Indeed, they are common laboratory animals, due to the ease of breeding them in large numbers and their apparent comfort in indoor environments. On the other hand, while there are obvious advantages, such as not being eaten by predators, hamsters do not naturally live in cages... so maybe they behave differently when given the free run of the countryside?