Prehistoric Mammal Discoveries of 2020

The largest known Oligocene whale was
moved into the new genus Ankylorhiza
this year

Well, that year was... different. Fortunately, it didn't stop me posting and, indeed, a cancelled summer break meant that you got one more post than anticipated you lucky people, you. But as 2020 finally passes into the history books where it can bloody well stay, it's time for the end-of-year roundup of paleontological discoveries that didn't make the regular blog. As always, no theme, just a random assortment of journal papers that may, for all I know, be thoroughly contradicted by this time next year. But this is a collection of things that some scientist, somewhere, thinks that they demonstrated in 2020:

Fossil Cats (That Aren't Sabretooths)

Acinonyx pardinensis

The cat family is traditionally divided into two subfamilies: the "purring cats", which are mostly small, and the "roaring cats" which are all medium to large in size. When most people think of fossil species, however, the first ones to pop into their minds are almost certainly the sabretooths, such as Smilodon. These belonged to a third subfamily (and whether they could roar or not depends on fragile bones and soft tissues that haven't survived) that left no modern descendants, dying out towards the end of the Ice Ages.

The sabretooth cats represent an early branch in cat evolution, perhaps splitting off at some point during the Early Miocene, over 20 million years ago. But this means that the cats we are familiar with must have existed - in some form - for equally long, leaving their own fossil history. If you wound back the evolutionary clock on a domestic cat, or even a tiger, you wouldn't find a sabretooth or anything that looked much like one. Exactly what you would find isn't something we can know with certainty, but we do know of a number of fossil species of non-sabretooth cat that at least give us some idea.

The Mammal That Lived Like a Woodpecker

Plesiadapis

The time since the extinction of the non-avian dinosaurs is traditionally divided into seven "epochs". Unsurprisingly, the more recent the epoch, the more familiar the animals that inhabited the Earth at the time. In my current long-running series on the animals of the Miocene (the fourth of these epochs, and also the second-longest) I have been able to talk about a number of mammals that can at least be placed into groups we understand. Horses may have had three toes, elephants may have had four tusks, and so forth, but at least we can tell, without any great difficulty, that they are, in fact, horses and elephants.

As you'd probably expect, this gets harder the further back you go. Firstly, even animals belonging to familiar groups are getting further away from their present-day forms. There comes a point where whales still walked on land, for instance. Secondly, the further we go back, the more animals we find that didn't leave any modern descendants, and, indeed, weren't even closely related to anything that did (Smilodon, for instance, has no living descendants, but it's still pretty obviously a cat). That can sometimes make it harder to say where such animals fit into the mammalian family tree or, perhaps more importantly, how they lived and behaved.

Miocene (Pt 23): Giraffes Become Tall, Hippos Stay Dry, and Antelopes... Get Eaten

Palaeotragus, a short-necked giraffe

About half-way through the Late Miocene, around 8 million years ago, worldwide temperatures began to drop significantly, and even tropical Africa did not escape the effects. In its case, this didn't lead to cold and barren steppelands, and, indeed, the world may still have been slightly warmer than it is today, but there is evidence of the expansion of grasses across many parts of the continent. Perhaps enhanced by the closure of the Mediterranean Sea during the Messinian Salinity Crisis and disruption of the monsoons, North Africa also became much drier than before, although whether the Sahara as we know it today dates back quite that far remains controversial; there is some evidence of sand dunes that far back, but also of numerous rivers crossing the region.

These changes in climate also affected the animal life on the continent, to the benefit of some and the detriment of others. Pigs are omnivorous animals, and one might expect them to have survived such changes relatively unscathed. In a sense, this is true, since they remained common on the continent, but the nature of particular species living there did change.

The Best Place to Den

Winter is a difficult time for many animals at high latitudes. Food is scarce, and the cold climate itself is a problem. Although many mammals do manage to keep going through the winter, others migrate to warmer climes, while many of those that don't hibernate instead. While this is by no means easy, for animals that can manage it, it allows them to preserve their energy, surviving off body fat without the need to search for food.

There has, historically, been some dispute as to whether bears truly hibernate or not. This is because the sort of undoubted hibernation practised by, say, bats, involves an almost total shutting down of normal metabolic functions with the animal effectively becoming cold-blooded for the duration. Bears do not do this; while they are asleep through the winter, their body temperature drops from a normal level of 37°C (99°F) to a low of 33°C (91°F). Now, this is not insignificant, since a human with a body temperature that low would be suffering from clinical hypothermia and in fairly urgent need of medical treatment. But still, you're not going to be so cold that dew literally starts forming on you, as happens with bats.

Small Cats: Rare Cats of Southeast Asia

Asian golden cat

Wild cats are generally quite elusive species, once we ignore the "big cats" such as tigers and leopards. Some of the small to medium species are nonetheless fairly well-known in the west, including such animals as lynxes and ocelots. But many of them are rather more obscure, tending to be stealthy, nocturnal hunters whose success at feeding themselves often relies on them not being seen. If we combine small size with heavy undergrowth - and, perhaps, not being found in Europe or North America - we are likely to find a few species that are rarely seen at all. 

The forests of Southeast Asia are particularly good place for such creatures to be found, and, in fact, I've already described a number of small cat species that inhabit the region. Those all belong to the "leopard cat" and "domestic cat" evolutionary lineages, but there are a further three species that occupy yet another branch on the cat family tree. Given what I've said above, it shouldn't be surprising that we don't know very much about them.

Last Gasp of the Australian Seals

Today, true seals only live much further south

In common English parlance, the word "seal" refers to a range of animals that, scientifically speaking, constitute two different, but related, mammal families. (A third related family, which today includes only the walrus, is distinctive enough that most people probably don't think of them as "seals" in the regular sense). I've previously written a post that goes into detail about what the difference between these two families is, but the technical names are phocids (for "true" or "earless" seals) and otariids (for the sea lions and fur seals, both of which have visible ears).

For simplicity, I'm going to refer to these two groups as "true seals" and "sea lions" in this post, although you should be aware that the so-called fur seals fall into the latter group. We've long known that "fur seals" aren't really a specific type of animal, but are at least two different kinds of sea lion that coincidentally look a little different from their relatives.

Porpoisely Quiet?

Way back in the early 19th century, the naturalist Karl Ernst von Baer, better known for his work on embryology, made an interesting discovery that seems fairly obvious to us in hindsight: the blowhole of a porpoise is, in fact, its nostril. Other anatomists followed up on this, leading to the further discovery that a number of air sacs appear to be connected to the nasal cavity. They can hold a fair amount of air when fully inflated, but nothing like as much as the lungs, so exactly what they were for wasn't clear.

Fast forward to 1956, and scientific research confirmed another interesting fact about such animals: they can echolocate by sending out sonar pings. In 1968, the two facts were put together when it was demonstrated how the unusual structure of the porpoise's head allows it to transmit the necessary sound pulses, which are initially generated somewhere in the nasal passages.

The Social Lives of Ground Squirrels

There are almost 300 recognised living species of squirrel. As one might expect given that large number, there is a fair degree of variety among them. To people living in Britain, for example, the word "squirrel" typically conjures up a small, tree-dwelling animal with a bushy tail. We only have two local species (one of them invasive) and they're very closely related. Take a look further out in the squirrel family tree, however, and we see some significant variations on the general theme of "squirrel-ness".

Perhaps the most obvious of these are the ground squirrels. Most ground-dwelling squirrels belong to a single evolutionary group, which includes something like a quarter of all known squirrel species. Many of these - the animals most commonly known simply as "ground squirrels" - look much like their tree-dwelling kin, but the group also includes such animals as prairie dogs and marmots as well as the semi-arboreal chipmunks.

Small Cats: Servals in the Savannah, Cats in the Congo

Serval

The best-known wild cats living in Africa are, of course, the large ones: lions, leopards, and cheetahs. South of the Sahara, they are joined by two species of small cat: the African wildcat (from which the domestic animal is descended) and the black-footed cat, both of which I have already described in this series. To these, we can add the caracal, a medium-sized cat that closely resembles the lynxes of Eurasia and North America. But, although this was most likely the animal that the word 'lynx' was originally coined to describe, the caracal is not closely related to what we would now regard as the 'true' lynxes. Instead, it is part of a distinctively African lineage of similarly medium-sized cats, containing just two other living species.

The more familiar of the two is surely the serval (Leptailurus serval), an animal that is not only widespread across Africa, but that happens to be relatively easy to breed in zoos. The name apparently derives from an alternative (and now obsolete) Portuguese name for the lynx that has now replaced variants of the older English name of "tiger cat" in most non-African languages. (It's still tierboskat - literally "tiger-forest-cat" - in Afrikaans, and, unsurprisingly, languages such as Swahili had perfectly good words for it already).

Miocene (Pt 22): Last of the Creodonts

The largest predator in Africa today

The dominant mammalian carnivores in Africa today are the lions, hyenas, and leopards, with cheetahs and wild dogs also playing their role. The ancestors of all of these creatures first reached the continent from the north, shortly after it collided with Eurasia during the Early Miocene. For the most part, at the time, their ancestors were small, with hyenas, for example, being no larger than mongooses. But this does not mean that Early  Miocene Africa had no large predators at all.

For one thing, the cats, hyenas, and so forth, were not the only carnivorous mammals to have made the crossing from Asia. The animals known as bear-dogs, or more technically, amphicyonids, are far better known from Europe, Asia, and North America, but they did reach Africa, too. 

Like a Hole in the Head: What's the Point of Sinuses?

We're probably all generally familiar with the existence of what are technically termed paranasal sinuses. That's largely because the inflammation of them, known as sinusitis, affects as many as 1 in 8 Americans, and presumably a similar number of people elsewhere, at least in the west. The term 'sinus' just means an empty space in something, and in the case of the paranasal sort, those spaces are inside the bones of our skull, connected by narrow passages to the nasal cavities.

The existence of these passages is important, ensuring that the sinuses are drained of mucus and filled with air... and also allowing any germs that you might have breathed to get into them and make what would otherwise only affect your nose into something worse. But why do we have sinuses at all?

Small Cats: Almost a Puma and Not Quite a Lynx

Jaguarundi (grey morph)

As I mentioned at the start of this series, the cat family can be divided into two living subfamilies. The "roaring cats" are all large animals: lions, tigers, leopards and jaguars. The "purring cats", however, are typically much smaller... but there are exceptions. Marginally the largest member of this subfamily is the animal variously known as a puma, cougar, or mountain lion (Puma concolor). These are all the same animal, although the term "puma" is sometimes reserved for the southern subspecies and "cougar" for the northern one(s). They were once found through essentially the whole of the Americas apart from Alaska and central/northern Canada, but, aside from a population of 200 or so "Florida panthers", are now absent from much of eastern North America.

Despite its unusually large size, however, the puma does not represent some early offshoot of the main feline lineage. Indeed, it is more closely related to the domestic cat than it is to, say, the ocelot. The cheetah (Acinonyx jubatus), the only other "purring cat" that comes close to it in size (the females are roughly similar in weight, but male pumas are larger), turns out to be a fairly close relative, despite the cheetah's remarkable specialisations for speed. The closest relative of the puma, however, is a somewhat less well-known animal: the jaguarundi (Puma yagouaroundi).

The Tale of the Tail

The defining feature of vertebrates is that they possess a vertebral column, or "backbone", a series of interlocking skeletal structures that run down the centre of the back and serve to protect the main nerve cord. Unless you're a shark or something of that sort, these structures are made of bone and, at least once we ignore fish and amphibians, there's a reasonably consistent pattern as to how these individual vertebrae are structured.

One of the distinguishing features of the mammal skeleton, however, is that the backbone can be divided into five distinct regions, based on the function and detailed structure of the vertebrae within it. At the front end (or top, if you're bipedal) are the cervical vertebrae, which together form the neck. The first two of these are further specialised, the frontmost one because it has to connect with the skull, rather than to another vertebra in front of it, and the second because it's the pivot that allows the head to turn. Including those, there are almost always seven cervical vertebrae, even in giraffes... although sloths and manatees are exceptions, because of course they are.

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.

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.

Small Cats: Ocelots and Margays

Ocelot

Of the seven species of cat identified in the 1758 treatise that marks the dawn of biological taxonomy, just three were what could plausibly be described as "small cats": the domestic/wildcat, the lynx, and the ocelot (Leopardus pardalis). Even today, these three (if we include bobcats in with the lynxes) are probably the best-known kinds of small cat, at least to most people in the West. Having already looked at the others, it's about time I turned to the ocelot.

Originally named as Felis pardalis, the ocelot kept this name up until the late 20th century. At that point, the genus Leopardus was resurrected, having first been used for the ocelot by John Edward Gray in 1842. Gray's original description of the genus doesn't fit at all with what we now know (and was almost completely ignored by everyone else at the time, anyway) but, even by the 1960s, it had become clear that there was a striking difference between the Leopardus cats and every other cat species in the world: they have only 36 chromosomes, instead of 38. This presumably reflects an ancient change in their ancestors, although whether it occurred before or after the proto-ocelots entered South America from the North is impossible to know.

Why Males Are More Muscular

There's a general rule in the animal kingdom that females tend to be larger than males. This is likely because of the extra demands of producing and laying eggs, or of spawning by whatever other method they use. Clearly, it's not a rule that holds among mammals where, while there are some exceptions (especially among bats), it's usually the male that's the larger and more physically imposing sex.

I discussed this a few months ago, in the context of seals, where this size difference is especially noticeable. But it's true in other mammal groups, too, including the primates. In general, the reasons for this are much the same among primates as they are among other mammals; males compete with one another for access to mates, and the most successful ones have more mating opportunities, and hence more children, as a result. Genetic inheritance then carries the trait of "large males" down to future generations, amplifying it until other constraints get in the way.

He Said, She Said

One of the most distinctive behavioural features of the human species is our ability to communicate. So far as we know, no other animal can convey even remotely as much information as we can by speech alone, never mind the advantages that writing brings. But we didn't come out of nowhere, and other mammals can also communicate vocally, something that may have particular relevance to the development of our own species when we look at other primates.

A number of primate species are highly vocal, such as gibbons or the aptly named howler monkeys. Another example, which may be less obvious. is the common marmoset (Callithrix jacchus). This is a species I've talked about before, a small monkey native to South America with a number of unusual biological and anatomical adaptations related to its reproduction and diet. (Unusual for primates in general that is, not compared with other marmosets). But it is behaviourally interesting as well.

Small Cats: Lynxes of North America

Canada lynx

For much of the 20th century, it was thought that there were only two species of lynx, one of which lived right across the high latitudes of the Northern Hemisphere, from Portugal to Newfoundland, by way of Siberia and Alaska. That began to be questioned towards the end of the century, and, since about 2005, it's been pretty much universal to consider this widespread animal to actually comprise three different species. Two of those live in Eurasia, with the other one found only in North America.

This, of course, is the Canada lynx (Lynx canadensis); the alternative form of 'Canadian lynx' is also used in some formal sources, but only seems about half as popular. It lives across virtually the whole of Canada south of the tundra but, despite the name, is also found in part of the US. Alaska is the most obvious example here, but Canada lynx can also be found south of the border in the Cascade and Rocky Mountains, around Lake Superior, and in much of Maine. Between 1999 and 2006, a number of Canada lynx were also re-introduced to Colorado, where they had been locally extinct since at least the 1970s; so far, they seem to be doing well enough.

What's the Closest Living Relative of Whales?

(For the TLDR crowd; just read the last paragraph).

It's been known for a long time that, at the highest level, mammals can be divided into three evolutionary groups based on their method of giving birth: marsupials, the egg-laying monotremes, and the placental mammals. That last group contains around 95% of all living mammal species, including everything from wolves to dolphins and moose to monkeys.

Given that wide variety, it's less obvious how we should divide up the placental mammals into smaller groups that genuinely reflect their evolutionary relationships. It's obvious that, say, cheetahs are members of the cat family and, at a slightly higher level, it's unsurprising that, for example, the dog and bear families are reasonably close relatives of one another. But once you get much higher than that, it becomes less so.

Giant Wolverines of South Africa

Modern wolverine

Africa is the world's second-largest continent, containing about 20% of Earth's total land area. Despite this, it's probably fair to say that its the least palaeontologically explored continent - with the obvious exception of Antarctica. But this is not to say that there aren't several very good fossil sites in Africa, many of which have contributed significantly to our knowledge of animal evolution.

The most famous of these sites are those connected with the evolution of our own species, but there are a number of sites that have yielded, for example, significant dinosaur fossils. When it comes to mammals other than humans (and whatever else was living alongside them), Kenya and South Africa have proved particularly rich sources - although, of course, there are others.

Small Cats: Lynxes of Europe and Asia

Eurasian lynx

Once we get away from the "big cats" as traditionally thought of (lions, tigers, leopards, cheetahs, and so on) the majority of wild cat species are at least broadly in the size range of the domestic animal. However, there are a few cats that are decidedly medium-sized on this particular scale, of which the best known in the Northern Hemisphere are probably the lynxes.

Lynxes are readily identifiable animals, and the word "lynx" itself dates back to at least the Ancient Greeks. They were also one of the original seven species of cat identified by Linnaeus in 1758 when he created the modern system for scientific naming of animals. As early as 1792, they were split off from the other cats into a subgenus of their own, now considered a full genus. This was in Robert Kerr's translation of Linnaeus' original work into English, by which point, at least four different species of lynx had been scientifically named and described (including one by Kerr himself, in the book in question).

Miocene (Pt 20): Unicorn-Pigs and the First Hippos

Prodeinotherium

Pigs seem to have been another example of animals crossing over from Asia when that continent collided with Africa around 17 million years ago. The oldest fossil pigs in Africa date from about that time and are represented by Kenyasus from Kenya and Nguruwe from Namibia and South Africa. These were relatively small, short-snouted pigs with a primitive appearance similar to that seen in their presumed Asian ancestors.

Because of these primitive features, determining exactly where they fit in the pig family tree isn't a simple matter, but they are often placed with a group called the kubanochoerines. Assuming this is correct (and it's far from settled) they must have evolved fairly rapidly into much larger and more distinctive animals. The best-known member of the group is the giant "unicorn-pig" Kubanochoerus, which lived in China during the Late Miocene. This was an exceptionally large, long-legged animal, perhaps standing 120 cm (4 feet) high at the shoulder and - even more dramatically - sporting a long pointed horn that projected from the centre of its forehead.

Chorus of the Dolphins

It's well-known that cetaceans - dolphins, porpoises, and whales - make calls to communicate with one another, in addition to the sonar pings used to navigate. The complexity of these calls varies significantly between species, although even sperm whales, for example, producing little more than a regular pattern of clicks, while humpback whales produce what appear to be sophisticated 'songs'.

Among the most studied of such calls are those of bottlenose dolphins (Tursiops spp.) which are the type most commonly seen in aquaria, making them relatively easy to observe. Having said which, it was only in 1998 that scientists confirmed that there was more than one species of bottlenose, leading to some confusion as to which one lived where and, by extension, which one any given prior study referred to. And, as I blogged about when the announcement was made back in 2011, we now know of a third one as well.

Stopping the Water Vole Killer

I have often referred on this blog to the number of mammal species that are currently faced with extinction, of being wiped totally from the face of the Earth. Depending on how strictly you want to define the threat, this could be anything up to 25% of the total known species, although it's worth noting that a great many other species have declining populations, if not ones that are likely to vanish altogether any time soon.

For many species, even if extinction is not a threat, extirpation can be. This is, essentially, a local extinction, where the species dies off entirely in some particular area, but still survives somewhere else. While it can be any area you like, in conservation terms, we tend to be talking about either countries or reasonably sized islands. Or, as is the case in Britain, both.

Many species of mammal have been extirpated from the British Isles over the course of our history. Wolves are one of the more famous examples here, with the last official record of a dead wolf dating from 1680 in Scotland (it's unlikely to have literally been the last, and rumours continued for another hundred years or so, although it's hard to know how many of them were accurate). In a number of other cases, such as the hazel dormouse, local populations today very much seem to be in decline.

Small Cats: The Manul and the Rusty-Spotted Cat

Manul

The leopard cat and its relatives form one branch in the larger feline family tree, and one that's entirely native to Asia. These live, for the most part, in tropical parts of the continent, often close to plentiful water. But at least one other close relative instead prefers to live in environments that are both much colder and much drier.

Perhaps the most popular name for the animal in English is Pallas's cat (Otocolobus manul), which tends to lead to an argument as to whether there's an 's' after the apostrophe or not. (There usually is, these days, but it's far from universal). For convenience, however, I'm going to use the alternative name of manul, which derives from the original Mongolian name of the animal.

Ancient Argentinian Armadillos

Nine-banded armadillo

Armadillos are, I suspect most people would agree, fairly odd-looking animals. Their unusual appearance is evident to a layman, and more detailed analyses of their biology and internal anatomy only bear this out. As one might expect for creatures with such a distinctive appearance, they have a relatively long fossil history, having split from other mammal groups a long time ago. The fact that their skin literally has bone embedded in it also helps when it comes to finding - and identifying - fossil remains.

Let's Split the Party!

Last week, I described how, over the last few decades, populations of gray seals have recovered from a near-total local extinction in US waters. Clearly, other species facing similar threats, across the world, have not been so lucky. The rapid pace of human expansion simply overwhelms the ability of some species to cope, whether it be through direct effects (expansion of agriculture, cities, transport networks, and so on) or indirect ones (climate change, most obviously).

In the millions of years before humans appeared on the scene the world was changing at a slow enough pace that it was possible for mammal species to evolve their way out of a problem. Many didn't, of course, and went extinct, but others gave rise to newer species that outlived them. Today, it's not just the scale of the changes humans are making that has caused problems for some species, but also their speed.

When it comes to dealing with very rapid changes in the environment - whether human-caused or otherwise - mammals have both advantages and disadvantages compared to some other species. On the negative front, mammals, especially the larger ones, have long generation times, meaning that any effect of evolution, even on a relatively minor scale, is inevitably going to be slow.

Grey Seals on the Rebound

According to the IUCN Red List, which is probably the most widely used catalogue of conservation statuses, roughly a quarter of all mammal species are "threatened with extinction". That's a broader category than "endangered species", but, either way, it's a proportion that's growing. (As it is, of course for non-mammalian species; amphibians, for instance, seem to be doing particularly badly).

Partly that's because we're getting better at evaluating such things, and identifying species as being at risk when we previously knew little about them - or, in many cases, didn't even know they were separate species. But it's also a consequence of mankind's ever-expanding ecological footprint, as some species become threatened that weren't previously.

Small Cats: Leopard Cats and Their Kin

Leopard cat
(a northern subspecies)

The jungles of Southeast Asia are home to a particularly large number of cat species. These include tigers, leopards, and clouded leopards, but also a number of smaller species. Of these, the most common are probably the jungle cat, which is a particularly close relative of the domestic animal, and the leopard cat (Prionailurus bengalensis) which is slightly less so.

Leopard cats were first identified as a separate species back in 1792, on the basis of animals known to live in Bengal, and some variant of the name "Bengal cat" remains common in a number of non-English languages. That "leopard cat" is often preferred is doubtless due to the fact that the Bengal region is just one part of their much larger total range.

Indeed, leopard cats are known from Kashmir in the west right across to Vietnam and Malaysia in the east, and also through most of the non-mountainous parts of China, reaching into the Russian Far East north of Manchuria. They are one of only two species of wild cat native to Korea (the other being the Eurasian lynx) and they are also found on a number of islands, including Taiwan.

Miocene (Pt 19): When Rhinos and Giraffes Went South

Prolibytherium

At the dawn of the Miocene, 23 million years ago, Africa was a very different place than it is today. This was as much due to simple geography as anything else. For one thing, the Sahara Desert didn't exist yet - even the most extreme estimates suggest that it didn't begin to appear until the Late Miocene, and it may well have not have formed until at least the Pliocene around 4-5 million years ago. Before this time, much of the continent was probably covered in warm, damp, forests interspersed with patches of more open woodland and scrub.

More significantly, perhaps, Africa was still an island continent, separated from Eurasia by a body of water called the Tethys Seaway. It had been like this, isolated from the rest of the world, for millions of years, during which time it had developed its own unique animal life, quite different from that elsewhere. At the time, the same was true of South America (and it still is for Australia), but that continent retained its unusual animals for much longer, not contacting the north until as recently as 2.5 million years ago, shortly before the first of the Ice Ages. When that did eventually happen, it led to the Great American Interchange, which set the scene for much of the American fauna we see today.

Musth and the Older Elephant

Male Indian elephant, probably practising his social distancing
rule of "stay at least 1.2 km apart."

As with many other group-living mammals, male and female elephants not only spend much of their lives apart, but also live in quite different sorts of society. Females live in small family groups, dominated by the eldest among them and consisting of her children and other close relatives. These groups, in turn, form larger aggregations known as 'clans', the membership of which can change over time, with individual families joining or leaving as circumstances dictate. The precise details vary between the three different species of living elephant, but these basic rules seem to be universal.

Males, on the other hand, leave the family unit of their birth as soon as they reach puberty. From then on, they spend much of their lives alone, without the benefit of the matriarch guiding their sisters. . From time to time, they may meet up with other males, or even join female groupings, but these are always short-term arrangements. This creates a situation where solitary males regularly travel about, hoping to encounter different female groupings as they do so; similar behaviour is seen among mammals as diverse as giraffes, polar bears, and killer whales.

Giant Ostriches of Europe

This post will be current as of 1st April, and that means it's time once again for... Diapsida!

The largest species of birds alive today are the ostriches. Since 2014, we have recognised two species of ostrich, but, as the fact it took us that long to notice might imply, they're about the same size, so which is actually "the largest" is debatable, although the common ostrich (Struthio camelus) tends to be the one given the honour.

Under the system of classification used throughout the 20th century, ostriches are a kind of ratite, a group of flightless birds, most of which are large, long-legged and long-necked, and all of which lack the keel on their breastbone to which the flight muscles would be anchored in other birds. In 2010, the first evidence surfaced that the ratites were not a natural evolutionary group, when it turned out that the South American tinamous formed a branch within the "ratite" family tree. Since tinamous can fly (albeit not very well) and, more importantly, do have a keel, they aren't ratites themselves, so the old terminology had to be dumped.

Small Cats: The Domestic Cat's Closest Relatives

Sand cat

The range of species included in the genus Felis has changed significantly over the years. Because of the way such things are named, it includes, by definition, the domestic cat and all its closest relatives - but how close is close?

Unsurprisingly, the genus appears in the very first catalogue of scientific names, all the way back in 1758. At the time, it included every one of the seven species of cat known to the author - wild/domestic cats, lions, tigers, leopards, jaguars, lynxes, and ocelots. Over the next few decades, whenever a new cat species was described (as you might imagine, cheetahs and pumas were among the first) it was added to the same genus. At the time, the modern concept of "taxonomic family" didn't exist, and, round about the same time that families became a thing and the Felidae were named, the big cats were hived off into a genus of their own, Panthera.

The Smallest Mammal Ever?

When it comes to fossil mammals, or indeed, any other kind of fossil animal, our attention is inevitably drawn to the giants. We are often fascinated by the mammoths or glyptodonts or the largest of Irish elk or the most muscular of sabretooths. Outside of mammals, it seems there's a never-ending battle to find the "largest dinosaur ever".

Indeed, one might almost get the impression that everything prehistoric was larger than today. In a number of cases, that's because larger animals really did exist in the past, perhaps being wiped out by a combination of the harsh realities of the Ice Ages and the arrival of human hunters. It's also an artefact of larger bones being easier to find in rock layers and being less fragile and likely to fragment when they fossilise. And that's before we add in the fact that most popular books on the subject tend to have a focus on the biggest and most dramatic animals of their kind.

Primate Penis Bones

At a certain level, the skeletons of all mammals follow a broadly similar pattern. Most of the bones that we see in the human skeleton are also found in the majority of mammals, and often in the same numbers. Famously, for example, a giraffe has exactly as many bones in the neck (seven) as humans do - they're just rather longer. Well, there's a reason giraffes can't bend their necks like swans.

Of course, when we get into detail, there are many exceptions to this. For instance, the default pattern for the paws of mammals is that they all have four digits with three bones each, and one with just two bones (the thumb and big toe in humans). But, obviously, this isn't true of all mammals. For instance, dogs have no big toe on their hind feet, and, while they do have a full set of ankle bones, the metatarsal that would normally connect to the big toe isn't there, either. There are rather more dramatic alterations in, say, horses and two-toed sloths, let alone dolphins.

Sharing Your Burrow

One of the key features of animal behaviour is sociality - to what extent the animal associates with others of its kind. Many mammals are solitary, meeting up to breed, but otherwise spending their adult lives alone, except when mothers are raising their young. That so many aren't is probably partly due to that period of long parental care. Mammals are defined by their ability to produce milk, which necessarily implies some degree of mother/child bonding, and it may well not take too many behavioural modifications to get from there to just not leaving home at adulthood.

Social behaviour has both benefits and drawbacks. On the plus side, pack hunting makes it easier to take down larger and otherwise unavailable prey, if you're a predator. If you're not, there's safety in numbers, and the more of you there are, the easier it is to spread out the duties of looking out for threats. On the downside, large numbers do make you rather more obvious, and if you're all after the exact same kind of food, there'd better be a lot of it about or some of you will go hungry.

The Cat Family: Domestic and Wildcats

European wildcat

Perhaps surprisingly, there is some confusion and debate as to the correct scientific name for the familiar domestic moggy. There are, in fact, at least three different possibilities, all of which have their supporters among the people who study such things.

Firstly, there's the option that domestication has had such radical effects on the cat that it can be considered a separate species. In this case, its correct name is Felis catus. That name was first awarded to the animal in 1758, in the oldest listing of scientific animal names still considered valid. At the time, Carl Linnaeus, who wrote the list in question, intended it to apply to both wild and domestic forms, although the domestic version was raised to subspecies status by Johann Erxleben 22 years later.

Miocene (Pt 18): Return of the Cats

Barbourofelis

For much of the Miocene, bears were represented in North America by the single genus Ursavus. This was relatively primitive, and small by the standards of modern bears, although still easily identifiable as such. It seems to have left no local descendants, but, around 7 or 8 million years ago, it was joined - and eventually replaced - by new arrivals from Asia.

The best known of these were Indarctos and Agriotherium, bears that were widespread across the Northern Hemisphere of the time, and common enough in both Asia and Europe. Indarctos was the smaller of the two, roughly the size of a black bear, and with what was probably a similarly omnivorous diet. It was likely more closely related to pandas than to other modern bears, and died out as the Miocene ended.

Male Chauvinist Seals

There are four basic mating systems that can be seen in mammals, or, indeed, any other creature that possesses two clearly defined sexes. In monogamous systems, a male and female pair mate with one another and then typically remain together to raise their young. This tends to occur wherever raising young is an energy-intensive task that requires the full-time attention of two adults to work.

In polygynous systems, one male mates with multiple females, to maximise the number of offspring he can sire. In the polyandrous system, it's the other way round, with a single female mating with multiple males (some mole rats do this, but it's rare in mammals). The final option is a promiscuous system, where both sexes have multiple partners.

A History of the Bamboo Rats

In terms of number of species, the mouse-like rodents are the most successful group of mammals alive today. The group is typically considered to consist of six families, with the vast majority of species crammed into just two - the mouse family itself, and the cricetids, which includes the voles and hamsters. These, however, are relatively late arrivals, and there are two families that split from the main line of mouse-like rodents long before the ancestors of the mice and voles diverged from one another.

One of these consists of a grand total of three species (maybe), living in the forests of southern Asia. The other goes by the technical name of the Spalacidae, and it consists of animals that have the rather unusual trait of spending almost their entire lives underground. There are at least 35 species of these animals, found in various places across Europe, Asia, and Africa. This is a fairly wide distribution, which raises the interesting question of how they managed to spread that far when they seem to have fairly narrow habitat preferences. Until recently, the evolutionary history of these oddities has been something of a mystery but now, it seems, we are starting to get enough information to piece together an overview.

The Cat Family: Felidae

It is sometimes said, perhaps only half-jokingly, that the growth of the internet has been largely driven by two things: pornography and pictures of cats. I can't do much about the first of those here, but cats are a different matter.

In fact, the reason that I haven't looked at cats so far in my annual surveys of mammal families is precisely because, if there's one group of mammals that has substantial coverage on the internet already, it's cats. Lions, leopards, and so on are also amongst the most popular of subjects for TV wildlife documentaries, and it's hard to see that I have much to add. But, nonetheless, and while I have, of course, covered cats before in individual posts, exploring the family is a gap that I eventually had to fill. So here we go.

Compared with some, more diverse, mammal families, members of the cat family, Felidae, are all readily identifiable as such. Cats have short faces, lacking the long snout of dogs, with large eyes and ears, and prominent whiskers. Their bodies are generally sleek, usually (although not always) with long tails, and they have muscular limbs and sharp claws. Indeed, apart from size and coat colour, most species of cat are remarkably similar in physical appearance. If you removed the skins of a lion and a tiger, only a real expert would have any chance of telling them apart.

Ancient Musk Deer of Barcelona

Micromeryx

The deer constitute the second-largest family of ruminants, in terms of living species, after the huge "cattle family", which includes just about everything with true horns, from bison to goats to impalas. Historically, they have been divided into two main subfamilies: the cervines, which include such things red deer and fallow deer, and the capreolines, which include roe deer, reindeer, and moose, among many others. But there was always one species of deer that just didn't fit, shunted off into a subfamily all by itself because of its many peculiarities.

This was the musk deer (Moschus moschiferus). The most obviously strange thing about, for a deer, is that it doesn't have antlers. Less immediately apparent is the fact that it's the only kind of deer to have a gallbladder, and there are some other anatomical oddities, too. The former could be explained by it having lost them at some point in its evolution - and, indeed, there are other known species of deer where this has quite obviously happened. However, it's a bit trickier to explain why a gallbladder would come back after vanishing, so the assumption was that musk deer were a very primitive form of deer that had never lost it in the first place.