Miniature Marsupial Lions

Thylacoleo carnifex

The largest carnivorous marsupial alive today is the Tasmanian devil (Sarcophilus harisii). Noticeably smaller than a European badger, it's still almost twice the weight of the next nearest contender for that title, or, indeed, of the omnivorous Virginia opossum so well-known to Americans. Most other living predatory marsupials can more accurately be described as "insectivores", due to their small size.

Unsurprisingly, this wasn't always so. Most famously, perhaps, there was the thylacine or Tasmanian wolf, which officially went extinct in 1936. There were also the "marsupial sabretooths" of South America, which died out during the Pliocene about three million years ago. However, these are no longer thought to technically be marsupials in the sense of being descended from the last common ancestor of the living species, even if they were definitely in that branch of the mammalian family tree.

Small Cats: Pampas and Mountain Cats

Pampas cat

With the obvious exception of the cheetah, cats are not generally pursuit predators. Rather than chasing their prey over a long distance, they pounce on them from ambush, dispatching them rapidly. As a result, they require habitats with plenty of opportunity for concealment, somewhere that they can hide themselves from potential prey until it's too late. The majority of small cat species are adapted to living in forests, where the bushes and other heavy undergrowth provide a perfect environment for this activity.

After the small cats of the Leopardus lineage first entered South America, it is just such places that most of their descendants ended up living in. This is where we find ocelots and all the other small spotted cats of the continent today. But, with little effective competition from other native predators (there really wasn't anything cat-like on the continent before they got there) it's perhaps unsurprising that some of them did adapt to different, more open habitats, as some of their more distant relatives had elsewhere.

500th Synapsida

Yes, it's been almost ten years since I started this blog and, while I don't do anniversary posts, since there are typically about 50 posts a year, this does happen to be my 500th post. Which is a fair few when you think about it. And, in general celebration of round numbers, that means it's time for another review of what's appeared in the last couple of years or so, and what might be coming next.

Even allowing for the series on Miocene animals, evolution has been one of the most common topics that I've written about in the last 100 posts, second only to animal behaviour. Which is hardly surprising, I suppose, given the number (and general popularity) of the posts I write about fossil species in general. Also common has been the perennial topic of reproduction, and there have been quite a few posts on animal communication and conservation as well.

In terms of types of animals, bats top the list in terms of the regular posts (although there's been nothing about them in 2020...), although clearly various kinds of rodents and members of the cat family have been particularly common subjects overall. Cetaceans seem to have taken a bit of a back seat recently, which is as likely due to what news I happen to have come across (or not) as anything particularly planned. The number of families of living mammal that received their first headline appearance in the blog is dropping; tenrecs qualify, but I'm not sure that anything else does. Yet, of course, there are still mammal families that haven't featured at all on this blog... most of them obscure kinds of rodent or bat, to be sure, but I've yet to do a post about (say) living tapirs or manatees.

While the top ten most popular posts of all time remain roughly the same ones that they were two years ago, there are some new challengers bubbling under. Among the most-read posts in the last twelve months (ignoring the possibility that spambots might have skewed the real figures) are the ones on babirusas, how baby bats learn to fly, the taxonomic position of whales, and the status of cave lions as a distinct species. The last is particularly notable, having only had a few weeks to leap to the #7 position for the entire year. 

Aside from those last two, posts in the last 100 that have notably more hits than others of the same age include my overview of the peccary family, another post on cave lions, and ones on fish-eating bats, sabre-toothed sea otters, and the origin of ducks. So, hey, well done to the bats and peccaries for beating out some of the fossils!

Of course, there have been posts on many other topics, too. I've also covered the fossil of a whale that had eaten another whale for dinner, the mystery of fluorescent pink squirrels in the forests of Wisconsin, the nature of the bones inside monkey penises, and what may be the smallest mammal ever to have lived. It's in the nature of writing a weekly blog that sometimes I finish a post and think 'well, that didn't work' and find it's far too late to do anything about it, but some posts that I liked and had particular fun writing include the two-part one on the diversity of living and fossil marsupials, and the one on how sewer and ship rats spread across the world. 

That, of course, was part of my 2019 series on British mammals. That was an excuse to write about the details of some particular species of small mammal, without needing to do anything as manifestly unmanageable as, say, try to describe every species in the squirrel family. The posts on rats and voles seemed to be the most popular, but, in general, it's not been up there with the series I've done on more charismatic groups of animal. But I do think it was worth it, covering a number of animals that might otherwise get left out; there are, after all, far more species of small mammal than large ones.

On the other hand, you can't get much more charismatic than cats. My current series, on all the world's small cat species, is surely suffering from the fact that there's quite a bit of coverage of this elsewhere on the internet, but it seems to be doing fairly well nonetheless. There are about another five posts to go in the series, covering species that are (with at least one notable exception) fairly obscure, but it should all be wrapped up by the end of the year.

It's fairly tricky to pick good topics for these series. Many families of mammals have too many species to cover in a year, many more contain too few (horses, say, or bears) and others aren't really varied enough to sustain an interesting series at that level of detail. The fact that it doesn't have to be a family is obviously a help here and, when I do return to carnivores, I'll probably cover a collection of related families rather than a single one. The 2021 series, though, is likely to be on something hoofed and, since it's probably going to be a large group, may require less detail on individual species in order to fit - and not become too repetitive. I'll see how that goes.

Turning to its less regular, but generally more popular, counterpart, I can see that, back in my 400th post, I said that I wasn't sure whether I'd be able to finish my series on Miocene animals by the end of this year. Well, I certainly won't, since I'm currently only halfway through Africa, and there's South America and Australia to deal with after that. So this really is going to be a multi-year project and one that will almost certainly still be ongoing by the time of post #600. Who'd have thought that 18 million years of worldwide history would take so long to describe, eh?

On the bright side, it also turns out that, while they don't give me any more free time, either, global pandemics don't stop me from sitting down in front of a computer and typing. Take that, covid-19! Best wishes for similar good fortune to everyone reading this, and I should be back with another of these posts in 2022...

[Photos by "Mnolf", NOAA, S. Taheri, and the US Fish & Wildlife Service, collage by "Prehistoricplanes".]

The Case of the Missing Sengi

The rediscovery of a species of mammal thought "lost" for almost 50 years was a significant enough story this week to appear (briefly) on the front page of the BBC News website. I'm not sure how much further I can add to the BBC story in terms of detail, but perhaps I can put it into context, as well as providing it for those who may not have seen the original. So here goes.

To start with, what exactly is a sengi?

Sengis used to be (and often still are) called "elephant shrews". The term is falling out of favour because they aren't literally shrews, in the sense of belonging to the actual shrew family, although, as descriptive terms go, it's not a bad one. Since the late '90s most scientists, when they aren't using the more technical term "macroscelidean", instead use the Swahili name for the animal, which is also the one I'll stick with.

Small Cats: Small Spotted Cats of South America

Oncilla

Cats were, like many other groups of modern mammal, relatively late arrivals to South America. When the continent merged with its northern counterpart, at least four kinds of cat were among the animals that headed south into virgin territory. Three were relatively large (jaguars, pumas, and the now-extinct sabretooths) but, in terms of the number of species surviving today, it was the smallest one that left the most descendants. Finding plenty of space, and few other animals already there that were at all similar, this early cat rapidly diversified into multiple different species.

This ancestral immigrant probably looked something like its best-known descendant, the ocelot. We can say this because most of its other descendants, such as the margay, also look quite a lot like ocelots. Compared with other cats - including those others on the same continent - they are all missing a pair of chromosomes, incorporating the relevant genes elsewhere on their genomes. That karyotypic quirk backs up the physical evidence of the cats' appearances to confirm their close evolutionary relationship.

Miocene (Pt 21): Mongooses and More

A modern mongoose

When Africa, moving north, collided with Asia around 19 million years ago, a number of hoofed animals, and other large herbivores, headed south to colonise the continent. Naturally, where herbivores go, predators follow, so an influx of carnivorous animals occurred at around the same time.

Until this time, Africa had been an island continent, separated from the larger northern landmasses and lacked many of the kinds of carnivore we are familiar with today. It had, for example, no cats, dogs, or bears, or even such quintessentially "African" animals as hyenas. All of these, and others besides, belong to the group of mammals known as "carnivorans", which essentially includes all large land-dwelling mammalian carnivores today, apart from the Tasmanian devil. They had evolved in the north, and the new land bridge gave them their first chance to reach the more southerly continent.

Were 'Cave Lions' Really Lions?

A theme that crops up on this blog every now and then is that some animal that many people probably assume is a single species is actually two or more. There are, for example, three species of zebra, three jackals, and seven different kinds of musk deer. The lion (Panthera leo) is not one of these animals; there really is only one species alive today - and it's been around for a long, long time.

I remember a few years ago, at London Zoo, I happened to be passing the lion enclosure when one of the keepers was giving a talk. The lions at the zoo were obtained from the Gir Forest in Gujarat, India, rather than being the African sort. The keeper repeatedly referred to "this species" of lion when, for example, he was indicating how much more endangered the Indian population is than the African one.