Sunday, 28 June 2020

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.

Sunday, 21 June 2020

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.

Sunday, 14 June 2020

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).

Sunday, 7 June 2020

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

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.

Saturday, 30 May 2020

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.

Sunday, 24 May 2020

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.

Sunday, 17 May 2020

Small Cats: The Manul and the Rusty-Spotted Cat

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.

Saturday, 9 May 2020

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.

Sunday, 3 May 2020

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.

Sunday, 26 April 2020

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.

Sunday, 19 April 2020

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.

Sunday, 12 April 2020

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

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.

Sunday, 5 April 2020

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.

Saturday, 28 March 2020

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.

Sunday, 22 March 2020

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.

Sunday, 15 March 2020

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.

Sunday, 8 March 2020

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.

Sunday, 1 March 2020

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.

Sunday, 23 February 2020

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.

Sunday, 16 February 2020

Miocene (Pt 18): Return of the Cats

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.

Sunday, 9 February 2020

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.

Saturday, 1 February 2020

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.

Sunday, 26 January 2020

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.

Sunday, 19 January 2020

Ancient Musk Deer of Barcelona

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.

Sunday, 12 January 2020

Voyage of the Kinkajous

For much of the time since the extinction of the dinosaurs, South America was an island continent. Developing in isolation, the mammals living there developed a number of unusual forms not seen elsewhere. Around 2.8 million years ago, however, South America became joined to its northern counterpart via the Isthmus of Panama. Northern animals flooded south, and relatively few headed in the opposite direction. As a result, unlike Australia, which remains an island continent today, the mammalian fauna of South America includes many animals at least broadly familiar from elsewhere.

Among the first mammal families to make the crossing was that of the raccoons. Although this had first appeared in Asia, living species are now found only in the Americas (ignoring some recent man-made introductions) with most of them found in tropical habitats. In fact, they reached South America almost ridiculously early, something we know because we have a fossil example that's around 7 million years old... at least 4 million years before the land crossing we'd expect them to have used had formed.

Sunday, 5 January 2020

Digging in a Winter Wonderland

Humans have a somewhat ambivalent attitude to snow, greeting it either with joy and wonder or with concern and frustration, in large part depending on how old you happen to be. It decorates Christmas cards, covers the countryside in pristine white, and provides plentiful opportunities for play. On the other hand, it makes travel difficult, and may even interrupt deliveries of food, making our lives awkward. (Plus, if you're in a city, it may not stay white for very long).

If heavy snow makes it difficult for us to get around and obtain sustenance, the same obviously goes for animals that live in the relevant parts of the world. Different species have different strategies for how to cope with its arrival. Some hibernate, while others avoid the problem by migrating somewhere else for the winter, but there are, of course, a number of species that simply have to put up with it. Those that live particularly far north may even have to do so for over half the year, and the difficulty of doing this is probably at least part of the reason why relatively few species do.