weasel family were the first group of mammals that I decided to spend a year describing in detail on this blog, back in 2011-12. I concluded the series with a look at their fossil history, stating, among other things, that the fossil genus Enhydrodion "may" have been the largest member of the family to have lived. This, however, relies on guesswork relating the size of the body of the animal to its skull, which is all we have in any completeness. But there are, in fact a number of other fossil members of the family with even larger skulls, so a lot rests on their exact bodily proportions, which are often a mystery.
Such examples include the giant wolverine Plesiogulo (for which we have not only the skull, but, just possibly, the penis bone), the giant hypercarnivorous honey badger Eomellivora, and the relatively long-legged Ekorus, whose relationship to other mustelids is unclear. But, according to a new analysis, the largest mustelid skull known belongs to an animal called Megalictis ferox.
Of course, calling Megalictis a "weasel" is a bit of a stretch. The weasel family is very diverse, including such animals as otters, badgers, and wolverines, as well as more obvious examples such as polecats and stoats. So, yes, it's really only a weasel in the same sense that a badger is... and that's assuming it's a member of the weasel family at all. So, let's start with that - what is this animal, and is it really a mustelid?
Sunday, 1 May 2016
Sunday, 24 April 2016
This, in fact, is the plains bison, which was once found across pretty much the whole of what is now the contiguous United States, leaving aside only the Pacific and Atlantic coasts and the arid deserts of the Southwest; they also lived in far northern Mexico and up as far as central Alberta. The other subspecies, commonly known as the wood bison (Bison bison athabascae) is native to north-western Canada and to Alaska. Physically, it's slightly larger than its southern relative, which means that, in the absence of American rhinos, elephants, and so on, it is, in fact, the largest living, land-dwelling animal of any kind native to the Americas.
Because bison are, indeed, pretty big. A fully grown male can be anything up to 195 cm (6' 6") tall at the shoulder, and can weigh as much as a tonne (2,200 lbs). Females are, admittedly, quite a bit smaller, although at a maximum of about 180 cm (6') and 550 kg (1,200 lbs) they're still pretty big - and closer in size to the males than, say, those of yak. The horns are also about the same size in both sexes, although (relative to the rest of the animal) fairly small in comparison to those of most other bovines.
Sunday, 17 April 2016
The biggest difference was likely in the north, where the even the very heart of what is now the Sahara Desert was likely covered in arid scrubland - hardly hospitable, but a significant improvement over baking hot dune-fields. By one estimate, moist savannah and open woodland stretched as far north as 21°, covering what are now countries like Chad, Sudan, and Mauritania. Further east, Somalia would also have been covered by woodland, rather than its current dry grasslands, and, at the opposite end of the continent, there may have been small forests in what are now the Namib Desert and the Kalahari.
It didn't last, of course. Around 3 million years ago, as the world fell irrevocably into the long autumn of the late Pliocene, Africa became not only cooler, but drier. And, if the generally cooler climate did not make too much difference to a continent sitting on the equator, the loss of rain certainly did. It's at this time that the Sahara, and the other deserts we are familiar with today, began to form, and the wildlife had to either adapt to that fact, or die. What was good news for voles in Europe, promoting the tougher grasses on which they thrive, was bad news further south, where the grass gave way to open sand.
Sunday, 10 April 2016
One of the endangered seal species is the Caspian seal, found only in the isolated and land-locked sea of the same name. The other two are monk seals, with one species each in the Mediterranean and off the coast of Hawaii. Quite how two such closely related species ended up on opposite sides of the globe is something I've discussed in an earlier post, but for today, the key point is that there used to be three species of monk seal, and that the other one went extinct around 1952.
Given this, the threat to the two remaining species is surely far from hypothetical. There are thought to be a little over a thousand Hawaiian monk seals alive today, but, as confirmed in a recent species review, the most endangered seal species of all is the Mediterranean monk seal (Monachus monachus) - the only seal species to live in the sea for which it is named.
Sunday, 3 April 2016
One of the more familiar of these "other" domesticated bovines is the yak (Bos grunniens), which is descended from... well, the wild yak (Bos mutus). Today, wild yak are found only on the Tibetan Plateau, although in medieval times they may have lived much further north and west. One small population is known to cross the border into Ladakh in far northern India at certain times of the year, but they are otherwise extinct outside of China, having vanished from Nepal as recently as the 1990s.
Saturday, 26 March 2016
When we think of 'birds' the ability to fly is surely one of the first things that come to mind. Indeed, the development of flight was surely one of - if not the - defining moments in early bird evolution. But, whereas bats have never given up that particular evolutionary innovation, flightless birds have evolved more than once. And, because we know that the very first birds could already fly, it follows that all flightless birds have ancestors that were perfectly capable of flight, but, for whatever reason, lost the ability.
Many, such as ostriches, did so to develop a fully land-based lifestyle, often becoming much larger in the process. But others swapped flight for diving ability. Of course, there are a great many diving birds that are still able to fly, but sometimes there is an advantage in really specialising in diving to the point that flight is no longer an option. This has, in fact, happened more than once in the course of avian evolution, but the only flightless diving birds we have now are the penguins, propelling themselves through the water with wings shaped like flippers.
Sunday, 20 March 2016
|Lungworm in a Guiana dolphin (H&E)|
These sort of strandings are fortunately as rare as they are dramatic - part of the newsworthiness in this case was so many happened in such a short time. Fortunately, the great majority of cetacean "strandings" aren't like this at all. In most cases, the cetaceans are already dead, or nearly so, by the time they wash up. Furthermore, most of them are dolphins, simply because there are more dolphins than whales in the world, and they are also more likely to be swimming in coastal waters in the first place.
After all, every dolphin dies eventually, and the body has to go somewhere. Often, they sink, leading to the spectacular scavenger feeding frenzy of "whale fall" when a vast and blubbery carcass sinks into the depths of the deep ocean. But, especially if they happen to die close to the coast, there's every chance that the body will float for long enough to eventually wash up somewhere. It happens every now and then to humans washed overboard from ships, so, when you think about it, it's unsurprising that it happens to at least some dolphins, too.