Sunday, 30 October 2022

Horns v. Geography - Relationships Among Rhino Species

White rhino
Rhinoceroses are amongst the largest land animals alive today, exceeded in size only by the elephants. As one might imagine, given their distinctive appearance, the group has a long evolutionary history. What is perhaps less obvious is that the family was once much larger than it is today, with many species living side-by-side. In total, we have so far named something like 100 species of fossil rhinoceros and, while some of those will probably not survive more detailed analysis, it's also true that there must be several we haven't found yet. Either way, it's quite a lot.

Most of these lived during the Miocene epoch (although the family is older than this) with the number of species thinning out during the following, Pliocene, epoch between around 5 and 2 million years ago. Even so, we know of nine species that lived during the later Ice Ages. Four of these, however, did not survive their end, leaving us with the five that - in some cases only just - survive today.

Sunday, 23 October 2022

The Lion Stalks Tonight

In the jungle, the mighty jungle, the lion probably does not sleep tonight.

The main reason for this is that lions don't really live in the jungle. Their primary habitat is savannah and open grasslands and while they can be found found in dry woodland (especially in India) they aren't found in the tropical rainforests that we typically associate with the word "jungle". Indeed, a map of Africa showing where you can find lions would have a very noticeable gap in the middle where the Congo jungle is - along, of course, with blank spaces over the harsher deserts. The idea of lions living in dense jungle probably owes more to Tarzan than reality.

Sunday, 16 October 2022

Decline of the Woodrats

The wild mice and rats of the Americas are not members of the true "mouse family", the Muridae, but instead belong to the Cricetidae, a name which translates as "hamster family". The vast majority of species in the family are not, however, hamsters, since the group includes both the voles (of which there are many) and the aforementioned New World mice and rats. Many of these latter are found in South America, with plenty more in Mexico and Central America. Most of them are mouse-sized, an example of the great success of the mouse body-plan where, despite having diverged from the true mice over 30 million years ago, such creatures as the American deer-mice differ from the house mouse by, at best, having a different colour pattern.

Just as some members of the mouse family developed larger size, evolving into such things as the familiar sewer rat (which, of course, has been introduced to America, even though it's not native there) so to did some of their New World counterparts. In the southern US, three different lineages of such creatures can be found: the muskrat (which is actually a giant vole), the cotton rats (which are related to the vast collection of South American rats and mice), and a third group variously called pack rats or woodrats.

Sunday, 9 October 2022

Leaf-Eating Monkeys: The Colourful Doucs of Vietnam

Red-shanked douc

Modern genetic analysis has shown that the leaf-eating monkeys of the Old World consist of three, related, evolutionary branches. Two of these, the colobus monkeys of Africa, and the langurs of Asia, had long been recognised as distinct, but the third was not always so. The monkeys belonging to this branch had, for the most part, previously been considered to be langurs, or at least part of the langur line, but it turns out that they split off from the others early on. Because of the comparative recency of this discovery, this third group doesn't have any distinctive common name and nobody seems to have come up with a scientific one, either. ("Rhinopithecinini" would seem the obvious choice to me, but one can see why nobody bothered).

So, instead, this group, when scientists need to refer to it, ends up being called the "odd-nosed monkeys". Even then, not all of them have noses that look (at least to me) especially odd, and this is most clearly true of the doucs. 

Saturday, 1 October 2022

Miocene (Pt 35): Crash Bandicoot and the Giant Platypus

When we think of marsupials, the animal that's probably most likely to come to mind first is the kangaroo, likely followed by the koala. Both of these animals, along with wombats and possums, belong to the largest order of marsupials, technically referred to as the diprotodonts - a term that literally means "two front teeth" on account of the enlarged, vaguely rodent-like incisors that characterise the family. These are used to clip at vegetation, since the group is overwhelmingly herbivorous.

This was less true in the Miocene, and that's because of the existence of marsupial lions. Or, more accurately, of thylacoleonids, members of the "marsupial lion" family, since the truly lion-sized animal best known by that name didn't live until much later. The group originated towards the end of the previous epoch, when some herbivorous, probably wombat-like, animal switched to a more meaty diet, its front teeth becoming blade-like in order to cut into flesh. They seem to have prospered during the Miocene, with three different genera currently recognised.