|The largest known Oligocene whale was|
moved into the new genus Ankylorhiza
Sunday, 20 December 2020
Sunday, 13 December 2020
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.
Sunday, 6 December 2020
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.
Saturday, 28 November 2020
|Palaeotragus, a short-necked giraffe|
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.
Sunday, 22 November 2020
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.
Sunday, 15 November 2020
|Asian golden cat|
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.
Sunday, 8 November 2020
|Today, true seals only live much further south|
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.
Sunday, 1 November 2020
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.
Sunday, 25 October 2020
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.
Sunday, 18 October 2020
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).
Sunday, 11 October 2020
|The largest predator in Africa today|
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.
Sunday, 4 October 2020
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?
Saturday, 26 September 2020
|Jaguarundi (grey morph)|
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).
Sunday, 20 September 2020
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.
Sunday, 13 September 2020
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.
Sunday, 6 September 2020
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.
Sunday, 30 August 2020
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.
Saturday, 22 August 2020
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.
Saturday, 15 August 2020
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.
Sunday, 9 August 2020
|A modern mongoose|
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.
Sunday, 2 August 2020
Sunday, 26 July 2020
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.
Sunday, 19 July 2020
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.
Sunday, 12 July 2020
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.
Sunday, 5 July 2020
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.
Sunday, 28 June 2020
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
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
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
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
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
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
Saturday, 9 May 2020
Sunday, 3 May 2020
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
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
(a northern subspecies)
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
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
|Male Indian elephant, probably practising his social distancing|
rule of "stay at least 1.2 km apart."
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
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
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
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
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
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
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
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
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
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
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
Sunday, 12 January 2020
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.