Delphinids: Pilot Whales

Long-finned pilot whale

The term "dolphin" is not, strictly speaking, a scientific one. It refers, in common parlance, to any small cetacean, often even including porpoises. Even ignoring the porpoises, however, not all dolphins are members of the dolphin family, technically referred to as "delphinids". This is because some freshwater animals are not closely related to the dolphins proper (or, indeed, to the porpoises). We call them "dolphins" because they're about the right size, a similar shape, and... well, we don't have a better word, at least for them all collectively.

But it works the other way, too. Not all members of the dolphin family are commonly called "dolphins". With the exception of the melon-headed whale, which it's hard to think of as anything other than a dolphin, this is because they're too big. We call them "whales" - another term that doesn't map to anything scientifically - since that's what we call any large cetacean.

Delphinids: Newest and Largest Dolphins

Fraser's dolphin

One of the largest features at the British Natural History Museum is a full-scale model of a blue whale, occupying a large chunk of one of the mammal halls. This was installed in 1938 by Francis Fraser, a Scottish zoologist with a lifelong interest in cetaceans. Eighteen years later, still working at the museum, he was put in charge of reorganising their collection of cetacean skeletons and came across one that hadn't been closely examined since it had arrived in 1895.

It had been donated by Charles Hose, a colonial administrator and amateur naturalist who had found the skeleton on a beach near a river mouth in Sarawak (then a British Protectorate). Hose hadn't been quite sure what it was, and simply labelled it "white porpoise ? Lagenorhynchus sp." before sending it on. When Fraser examined it, however, he soon realised that it couldn't possibly be what Hose had guessed and that it was, instead, an animal previously unknown to science.

How to Drink Nectar

Orange nectar bat

When most people think of what bats eat, the first thing that likely comes to mind is insects. It probably doesn't make much further thought to remember that fruit bats also exist. And these are the two most common sources of food for bats, although 'fruit' in particular can cover quite a wide range of specific food types. But bats are the second largest order of mammals, after the rodents, and there is considerable variety amongst them.

This is particularly true of the leaf-nosed bats, or phyllostomids. While most formally recognised families of mammals have names almost everyone is familiar with - cats, bears, dolphins, horses, gibbons, etc. - and most of those that don't at least sound like they're actual names - binturongs, tuco-tucos, tenrecs, colugos - bat families tend to lack anything we could reasonably describe as a common name. Instead, we have bulldog-bats, and sucker-footed bats, and disc-winged bats, and so on. 

So it is with the leaf-nosed bats, which are the second-largest family of bats in terms of number of species, beaten only by the vesper bats. The family is usually divided into no fewer than eleven subfamilies, all of which have equally obscure-sounding names, and, in some cases, not even that much. It may not be obvious that, say, the spear-nosed bats are a subgroup of the leaf-nosed bats, but they are. And it's even less obvious that stenodermatines are phyllostomid, but kerivoulines are not.

Sea Lions v. The Blob

The waters off the coast of Alaska are supposed to be cold, especially in winter. Yet, in the autumn of 2013, they cooled far less than they normally would. A great mass of warm water, 2,000 km (1,250 miles) across and around 100 metres (330 feet) deep, remained trapped in the North Pacific. Nicknamed 'The Blob', this was caused by the weather patterns over the region remaining stuck in a high-pressure mode, preventing the warm water from dissipating with the winds as it should do. With temperatures stuck at up to 4°C (7°F) warmer than normal, the high pressure did not dissipate for eight months.

When it did, tropical winds pushed the warm water up against the American coast, from southern Alaska to southern Mexico, where it basically sat until El Niño kicked off in 2015... and that kept things unusually warm for another year. Inland, this disrupted weather systems leading, among other things, to frequent thunderstorms that sparked what was (at the time) the worst wildfire season in California's history.

The Diets of Parallel Pigs

Peccaries from South America

The word "ungulate" refers to a broad category of mammals that are generally large and herbivorous. They form a natural evolutionary group, although only if you include the cetaceans, which are descended from vaguely hippo-like ancestors. The word comes from the Latin word for "hoof", and the great majority of living ungulates have hooves of one kind or another. Even ignoring the cetaceans there are exceptions, but it doesn't take a great stretch of the imagination to see that camels, for instance, are at least the same general kind of animal as deer or cows.

All living ungulates can be placed into one of two mammalian orders: the artiodactyls, which includes the cloven-footed kinds, and the perissodactyls, which includes, among others, the horses. If you start looking at fossils, however, it becomes clear that other ungulate orders once existed. Most were very early, dying out in the first half of the Age of Mammals, representing early branches in the great ungulate family tree that ultimately proved unsuccessful.

Wolves, Foxes, and Food

Large scary predators are, by their nature, rare. There simply can't be too many of them, or they would run out of food to eat, something typified by the trophic pyramid often seen in biology textbooks: plants are eaten by herbivores are eaten by carnivores are eaten by bigger carnivores, with each step necessarily having a smaller total mass. The reality is, of course, somewhat more complex than this simple chain would suggest, most obviously because it ignores omnivores and decomposition.

But the basic idea holds, and apex predators - those that are large enough that nothing else normally eats them - exist in much smaller numbers than herbivores or smaller carnivores. This means that, relative to their numbers, they have a disproportionate effect on the ecosystem within which they live. Take away the apex predators and, even though there weren't very many of them to begin with, you will radically change the local ecology.

And, because they are relatively few in number, apex predators tend to be especially vulnerable to being wiped out. That's even assuming that humans don't focus on them deliberately out of fear, whether for their own lives or for the good of their livestock. Globally, apex predators are declining. (On this blog, we're mostly interested in mammals, but consider, for example, that at least eight of the 23 species of crocodile/alligator are currently thought to be endangered).

The Struggles of a Pollinating Bat

Note the dusting of pollen...

When we think of flowers being pollinated, for most people, the first things that are likely to come to mind are insects, especially bees. But other creatures, including mammals, can also be a part of the pollination process, and this is particularly true of bats. Nor are we talking about some occasional event that merely gives the flower some sort of backup - for some the presence of pollinating bats is crucial to their survival.

Even aside from the obvious importance that this gives bats to the wider ecosystem, this can also have direct economic importance to we humans. For example, sour pitayas are an important cash crop in parts of Mexico. Similar to the much sweeter dragonfruit (although not closely related), they grow on a particular type of cactus that is native to the country but is also commonly cultivated. As it turns out, this cactus relies on bats for pollination. While they are not essential, crop yields drop by over a third when the bats are prevented from reaching them, which would clearly be devastating for a Mexican farmer who may be living on the edge of profitability to start with.

From Dragon to Cave Bear

In 1675, German physician Johann Paterson Hain published a detailed description of the bones of what he believed to have been a dragon. Such bones had been unearthed from German caves for centuries and identified as belonging to various mythical creatures, with unicorns perhaps the most popular - likely since one could sell supposed unicorn horns for their magical healing properties. Fortunately for us, his illustrations were highly accurate and we can identify them for what they really are.

Indeed, while naturalists continued describing such bones as belonging to fantastical animals into the 18th century, physician and rationalist Gregor Horst had beaten them to the punch, pointing out as early as 1656 that bones recovered from Unicorn Cave (yes, that is its actual name) looked remarkably like those of "bears, lions, and humans". Today, we can look at Paterson Hain's original illustrations and confirm that he had produced the first known published drawings of the bones of a cave bear.

Mice at the Oak Tree Cafe

Forests, it should come as no surprise, rely on a complex set of interdependencies among the native species. The animals that live in the forests rely on the existence of the trees for shelter or food, or feed on other animals that rely on the trees for food. But the trees also need the animals, or at least some of them.

Obvious examples include the reliance of many plants on insects and other animals for pollination. Another is the fact that plants have edible fruit specifically so that animals will eat them and spread the digestion-resistant seeds in their dung. That doesn't work where the animal obtains nutrition from the seed itself, as is typically the case, for example, of plants that produce nuts. But, even here, the plants may rely on scatter-hoarding.

That is to say, many seed-eating animals in temperate regions store food in caches hidden across the landscape - squirrels being among the better-known examples. Some of those caches won't be found again, or the animal that made them will die from other causes before it has the chance to use them. And then, the seeds can germinate - the great majority won't, but it happens often enough that this simple process is of key importance to the survival and growth of some nut-bearing trees.

Drought and the Mother Rhino

You may be surprised to discover that the white rhinoceros (Ceratotherium simum) is not internationally listed as an endangered species. This is because it is reasonably widespread across southern Africa, poaching of the species has been in decline since 2014, largely due to effective enforcement methods. While it did almost go extinct in the late 19th century, well over 10,000 of the animals are thought to be alive today, with populations in some areas still rising in recent decades. In fact, it meets all the usual criteria for a species of "least concern", one that we wouldn't normally consider even close to being threatened.

This, of course, hides a fair bit of complexity.

A Tiger's Dinner

One of the basic concepts in ecology is that of the food chain; the idea that plants are eaten by herbivores are eaten by small carnivores are eaten by large carnivores. The reality is both more complex - because, for example, omnivores exist - and simpler, because, at least on land, many of the largest carnivores eat large herbivores, not smaller carnivores. Nonetheless, there's still an underlying truth, and it introduces us to concepts such as the apex predator.

An apex predator is essentially a carnivore that has no predators of its own, an animal that sits at the top of its local food chain. Many mammals fit this description, including wolves, big cats, bears, and killer whales. (The last of those, of course, being an example of a large carnivore that does mainly eat smaller carnivores). Outside the world of mammals, one could add eagles, crocodiles, and sharks, among others. Humans could count as another example, given that we obviously don't have regular predators, but this does depend on your exact definition, since we're clearly omnivorous and, in many parts of the world have a nearly or totally herbivorous diet.

The Rarity of Gophers

What exactly does it mean to say that a species is "rare"? The general idea, of course, is that it must have a lower total population than some species that is "common", and we can certainly argue over where to draw the line between the two. But, even then, rarity can manifest in different ways and that may have an effect on our perception of it.

Take the tiger for example. Today, this is undeniably a rare animal, and it's internationally listed as an endangered species. But go back two hundred years, and tigers were found across southern Asia from the easternmost parts of Turkey to the Russian Far East. They stretched from the deserts of Central Asia to the jungles of Java. But even then, if you'd gone to any of these places, the chances of actually meeting a tiger weren't all that high. Tigers are big predators, and they need a wide area to find enough food to eat. So they may have had a high total population (certainly compared with today) but they weren't exactly abundant in any given locality. Does that count as being "rare"?

The Other One: Red Pandas

Over the course of this year, I have looked at all the species of the raccoon and skunk families, two groups of smallish carnivorous mammals that are mostly confined to the Americas. These two families are themselves related, forming part of a larger group called the "musteloids", traditionally ranked as a "superfamily". The group is named for a third family within it, the mustelids or "weasel family", which contains a much wider - and more widespread - group of species, including otters, badgers, and wolverines. 

The musteloid superfamily, however, also contains one other living species that does not fit into any of the three main families: the red panda (Ailurus fulgens). Six years ago, I took a look at the history of Western knowledge of this animal, and of how it relates to other mammal families. The upshot of that, you may recall, is that there is broad agreement that the red panda is the only living species in its family, distinct from raccoons, skunks, and weasels although quite how was unclear. Since I wrote that, a further study has come out supporting the evolutionary tree I described as "the current best bet", but I'd be remiss if I didn't point out that at least one contradictory study has also been published. It's perhaps fair to say that the four families of musteloids all appeared fairly suddenly at around the same time (likely around the Grande Coupure) and the exact sequence of events is difficult to disentangle.

Attack of the Giant Hyenas

Dinocrocuta

I suspect that most non-specialists would assume that hyenas are fairly closely related to dogs. They certainly look more like dogs than they do anything else, so, absent any further information, that seems reasonable enough. But, in reality, hyenas belong to the cat-like, not the dog-like, branch of the carnivoran family tree.

This isn't some new discovery on the basis of molecular evidence, like the splitting off of the skunks from the weasel family; it's been known for a long time. This is because, when you start looking at the structural details of the skull, especially the area around the ear, everything fits with a cat-like ancestry. This much was already obvious when Miklós Kretzoi formally named the two carnivoran branches while he was working at the National Museum of Hungary during World War II. Modern evidence has merely confirmed the view, showing more precisely that the closest living relatives of the hyenas are the mongooses.

Skunks of the World: Hog-nosed Skunks

American hog-nosed skunk

There are, perhaps surprisingly, at least five different species of skunk living in the US. In fairness, two of them - the spotted skunks - are so similar to one another that it took genetic tests in the 1990s to prove they were more than subspecies, while the striped and hooded skunks are at least superficially similar as well. The fifth one is the American hog-nosed skunk (Conepatus leuconotus) and it's neither striped nor spotted.

If it's less familiar than the others, even to many Americans, that may be because it's only found in the southwest. It is common across Mexico, and also lives across Central America as far south as northern Nicaragua, but in the US it's restricted to Arizona, New Mexico, and Texas. Even here, it doesn't inhabit the whole region, being found in only certain parts of those states and avoiding, for example, both the harsher deserts and dense woodland. Although it does live in some tropical habitats at the far southern end of its range, its preference is instead for grassland and mesquite scrub, often with plenty of acacia thorn bushes. 

Hammer-Toothed Snail Eaters

As is true of mammals more generally, the majority of Australian marsupial species are herbivorous, including such familiar animals as kangaroos, wombats, koalas, and possums. (The latter, of course, are not to be confused with the American opossums, which are omnivorous and not very closely related to their Australian namesakes). Most, but not all, of those that are not belong to a single order, the dasyuromorphs, sometimes called the "carnivorous marsupials" for this reason.

Although they represent almost a third of non-American marsupial species, dasyuromorphs are far less diverse than their herbivorous counterparts, with all but one of the living species belonging to a single family, the dasyurids. Although the most famous example of the dasyurids is probably the Tasmanian devil, which eats comparatively large prey, most of the other species are small shrew-like animals feeding on insects. Alongside them, we can place the numbat and the extinct thylacine ("Tasmanian tiger" or "wolf") both of which are odd enough to be placed in families of their own.

Cheetahs and Wild Sheep

The cheetah (Acinonyx jubatus) is surely one of the most familiar of African animals, due in large part to their prominence in wildlife documentaries such as Cheetah Family & Me. They are charismatic, distinctive, and not especially rare or difficult to find. Unlike, say, tigers, they are not internationally listed as an endangered species, although their population has declined rapidly enough over the last few decades that they do qualify for the lesser rating of "threatened" or "vulnerable" species. 

This does, however, disguise some significant regional variation.

How we should divide the cheetah into subspecies is not absolutely clear. From at least the 1970s, five subspecies were recognised, Two of those were merged in 2017, on the grounds that the East African form could not be reliably separated from its southern relative genetically. Even then, cheetahs have so little genetic variation across their range - due to an apparent population bottleneck when they almost died out at the end of the Last Ice Age - that support for the existence of two of the other subspecies remains a little shaky. Still, four subspecies is, for the time being, the general consensus.

The Pandas of Bulgaria

The bear family as it exists today contains relatively few species. All but two of these species are placed in a single subfamily, the ursine bears, which includes the familiar black, brown, and polar varieties along with a couple of species unique to southern Asia. A second subfamily, the short-faced bears, includes the living spectacled bear of South America and several, often exceptionally large, fossil species. They are thought to have split from the ursine bears around 12 million years ago, towards the end of the Middle Miocene. The third living subfamily is both much older and more distinctive.

This, of course, is the subfamily of the pandas, the Ailuropodinae. Pandas are sufficiently odd that it was unclear for a time whether they were really bears, or something else, although their status hasn't really been in doubt since the 1980s when genetic evidence proved what had, even then, been suspected for a couple of decades. Today, only one species of ailuropodine exists, the giant panda (Ailuropoda melanoleuca), and it is found only in China. The same evidence used to estimate the split between the other living subfamilies puts the date of the split between pandas and other bears much further back, to around 20 million years ago, not long after the dawn of the Miocene. 

Dunnarts in the Sandhills

It's a recurring theme of this blog, especially notable in last year's series on Old World leaf monkeys, that a great many mammalian species are threatened in some way. Population numbers of many species are declining, to the point that their continued existence is in doubt, often due to human encroachment on their habitat, but also due to the habitat itself changing as climate change continues. In this context, the quest of zoologists to understand how mammals (and other animals) behave is not just one of intellectual curiosity but can be of direct benefit to the creatures themselves.

For example, it is useful to conservation efforts to understand not only where a given species lives, and the habitat requirements it may have, but how it makes use of that environment. (Obviously, there's more to it than this, for example, how different species in the same area interact with one another but we'll stick with this one point for today). What particular features of the habitat are important to it? How much land does it need? How is its population distributed across the area? 

Prehistoric Mammal Discoveries 2022

New reconstruction of the sabretooth cat
Homotherium, showing that the teeth
would not have been as visible as popularly
supposed

2022 approaches its conclusion and I have to say that, while far from perfect, it was an improvement on the previous two years. There were a couple of weeks without posts this year, one for positive reasons, and one less so, but overall it has been good. Next year, you can look forward to something other than monkeys in my "family" series of posts and also to the conclusion of the long-running Miocene series, which should be as early as February. Until then, here is the now-traditional year-end look back at the paleontological discoveries that didn't quite make it into the blog.

Large Herbivores

Probably the most distinctive thing about deer is that the males have antlers; branching bony head ornaments that are shed and regrown each year. This naturally raises the question of how this evolved, since no other animal has quite the same thing. Acteocemas was an Early Miocene deer, but despite living very early in the group's evolutionary history, it already had antlers that split into two near the tip - which the horns of animals such as cows and true antelopes never do. A Spanish fossil of the antlers described earlier this year showed that it was already shed and regrown, but microscopic analysis indicated that it appeared to have been present for over a year, suggesting longer a more irregular pattern of shedding that must have changed to the seasonal pattern we are familiar with more recently, perhaps in the Middle Miocene.