Goo Goo G'joob

"Pinnipeds" is the technical term for flipper-footed aquatic mammals that are able (although often with difficulty) to move about on land. Although there had previously been some speculation on the point, we now know that they are a natural group of animals, all descending from a single distant ancestor. They are carnivorans, more closely related to dogs than to cats and probably represent the third major branching within the living dog-like carnivores, after the dogs and bears, but before (for example) the raccoons, skunks, and weasels.

The living species of pinniped are placed within three families, although one or two extinct ones are also recognised. Most pinnipeds belong to the Phocidae, or "seal family". While the term "seal" is often used in modern English to refer to pinnipeds in general, the seal family proper consists of animals especially well-adapted to living in the water. They lack visible ears, and their hind limbs are arranged so to be efficient for propulsion underwater, but almost useless on land, forcing them to haul themselves about using their front flippers only.

The Patagonian Homunculus

In 1891, Argentinian naturalist Florentino Ameghino, the founding father of South American palaeontology, described a new species of fossil primate. Naming it Homunculus ("little man"), he recognised that it resembled a lemur almost as much as a monkey and must therefore be very primitive, but he was unable to categorise it further.

To be fair, all he had at the time was a section of the lower jaw. Over the next seven years, working with his brother Carlos, he uncovered a few further specimens. These included part of a skull and some limb bones, but the exact details of what they had discovered remained obscure, beyond the fact that it was a primate of some sort.

It didn't help that, after 1898, the next discovery of a fossil belonging to the genus didn't happen until the 1980s. And that was only a few isolated teeth. Since then, nothing until the current century.

Viverrids: Half-Weasel Palm Civets

Banded palm civet

The word "civet", as currently used in English, is a rather broad term, referring to a wide range of vaguely similar-looking animals. Not all of these are even members of the "civet family" as we currently understand it, and even those that are don't form a natural biological group within that family. 

The word was originally Arabic (pronounced something like "zabad") and would have referred to the animals that medieval Arabs were familiar with, which, given how far they traded, would have included both African and South Asian species. These are still regarded as "true civets" today, but the word now also appears in the name of the "palm civets", long thought to be merely a variant of the true sort.

Just Cold Enough

Northern meadow jumping mouse

Hibernation is one of the most effective means that mammals can employ to withstand harsh winter temperatures. Many mammals, especially larger ones, use other means, such as growing a winter coat, caching food, or simply moving somewhere warmer, but, if the goal is to reduce energy requirements when you can't get out to feed, hibernation is the most effective means of doing so.

During hibernation, bodily metabolism slows right down, so that an animal may need as little as 1% of its usual calorie supply to stay healthy. This has negative consequences, so that the animal does need to wake at intervals to stave them off, and how often this happens varies from species to species. In this respect, true hibernation can be distinguished from shorter, often daily, bouts of torpor by the fact that each "sleep" can last for weeks or even months. 

The Air Conditioning in Your Nose

The nasal cavities are not mere holes running through the head. Anatomically, at least, that's broadly true at either end - in the vestibule immediately behind the nostrils, and in the nasopharynx above the throat. But in between, in the area above the mouth and separated from it by the palate, the air instead must pass through defined channels. 

These channels are formed by the "conchae", projections from the outer side of each nasal cavity stretching almost to the inner surface, so that most of the air is forced through the narrow slots between them. These conchae are, in turn, formed by the turbinate bones, delicate, paper-thin, sheet-like structures rolled up like a scroll, and covered in the same sort of fleshy lining that we find in, say, the trachea (windpipe). 

Bats in the Belfry

Mammals, like other animals, need a safe place to sleep. For large animals living in herds on the open plains, safety in numbers may be the best they can do, with some keeping guard while the others perhaps try to hide in long grass. Hiding in trees or sleeping on rocks out in the ocean are valid options for those in the right habitat. For many others, however, especially the smaller ones, some kind of den, nest, or burrow provides just the ticket. In the case of bats, we have roosts.

When it comes to bat roosts, it's likely that most people initially think of caves. Caves can hold communities of thousands of bats, often with many different species sharing the same one. Caves are ideal roosts for bats, because they provide a stable environment safe from the weather, few predators will enter them, and, when you're nocturnal anyway, you don't care that it's dark. 

Delphinids: Right Whale Dolphins

Northern right whale dolphin

Dolphins are familiar animals. We see them at aquaria and boat trips to see them in the wild are relatively common. In recent decades, there has been a rise in 'swimming with dolphins' tourist experiences, which studies have shown to be good in the short term for humans, but less so in the long term for the dolphins. Either way, we know a fair amount about them, both culturally and scientifically and, depending on the part of the world you live in, there may be many different species that you can see.

Some dolphin species, however, are less well-known than others. I've covered some already, but perhaps the most obscure are the right whale dolphins. 

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.

Delphinids: The Freshwater Dolphins of Brazil

Tucuxi

In this series so far, I have generally been referring to the Delphinidae as the "dolphin family". That's a literal translation of the name and serves to distinguish it from, say, the porpoise family. However, as I mentioned in the first post, not all animals commonly referred to as "dolphins" belong in the family. Thus, when zoologists want to distinguish the family from those other animals, but want to avoid saying "delphinids", the more common term is "Oceanic dolphins". Oceans are, after all, where they are found.

With, it turns out, one exception.

The tucuxi (Sotalia fluviatilis) is unique among Oceanic dolphins is being an exclusively freshwater animal. It lives in the Amazon River and its major tributaries, mostly in Brazil, but also further upstream into Colombia, Peru, and Ecuador. Indeed, it was first formally described, by Paul Gervais in 1853, from an animal sighted in Peru, about 2,500 km (1,500 miles) from the mouth of the Amazon... and they are known to get further upriver than that, until they are stopped by features such as waterfalls.

Delphinids: Dolphins of the Deep Seas

Rough-toothed dolphin

To our human eyes, it's easy to distinguish the major habitat types on land. There are pine forests, tropical jungles, open prairies, deserts, mountains, and so on. When it comes to the sea, however, it's less obvious. Most maps show the sea as a solid mass of blue which is, of course, what most of it looks like from the surface. But there are different environments and habitats within it, even if they aren't necessarily arranged in quite the same way.

While for some dolphin species the only real limitation is pack ice preventing them from surfacing to breathe, most have more specific requirements. Temperature is the most obvious, with some species preferring tropical or subarctic seas, but the depth of the underlying water is also significant. Species such as common and bottlenose dolphins are most comfortable over the continental shelves, where nutrients well up from the sea bed to feed the fish and squid on which they prey. Rather more species prefer shallow waters, close to the coast. Here, the water is shallow enough for light to reach the bottom, allowing seaweed or coral to grow, which benefits a different kind of fish than those further out.

Delphinids: Small Dolphins of Shallow Southern Seas

Commerson's dolphin

While related, dolphins and porpoises are regarded as distinct types of animals. Each is placed in its own family, with the two separating at least 15 million years ago. However, telling the two apart is not always easy, at least on a superficial look at their external anatomy. Porpoises are, generally speaking, smaller than dolphins and they have a blunt nose rather than a 'beak'. The problem is that we can say exactly the same about some species that really are dolphins.

In 1766, naturalist Philibert Commerson accompanied explorer Louis-Antoine de Bougainville on what would become the first successful French circumnavigation of the globe. While passing through the Straits of Magellan the following year, he spotted an unusual-looking dolphin close to the ship and sent a description of it back to France. (As a side note, later on in the voyage, it was discovered, much to the crew's shock, that Commerson's assistant was secretly a woman; she is now remembered as the first woman to circumnavigate the globe).

Delphinids: White-sided Dolphins

Atlantic white-sided dolphin

The taxonomy of dolphins is far from settled, with exactly how we should classify some species having been an open question for years. There is a good chance that the scientific names I am using for some species in this series will not still be in use in a decade, as old genera are split and the family tree re-arranged. Such is the case, for example, with the dolphins of the genus Lagenorhynchus.

The genus was named by John Edward Gray in 1846 for a specimen of a previously unknown species sent to him for analysis at the British Museum, after having been caught somewhere off the coast of Norfolk. It translates as "bottle-nose", for the shape of the beak... which is, perhaps, unfortunate, given that the animal we refer to in English as the "bottlenose dolphin" is something else entirely. Over the centuries since, five new species have been added to the genus, giving us the six we recognise today.

Delphinids: Humpback Dolphins

Indo-Pacific humpback dolphin

The genus Stenella, to which many of the closest relatives of the well-known bottlenose and common dolphins belong is, genetically speaking, a mess. A combination of interbreeding and rapid speciation have made it very difficult to determine how its family tree should be constructed or if, indeed, there is even a clear pattern to find. 

Our best evidence suggests that it probably isn't a "real" group, in the sense of one consisting of a common ancestor and all of its descendants. That's because three other genera of dolphin appear to be descended from that common ancestor, forming part of the same cluster of what we might describe as "typical-looking" dolphins. The common and bottlenose dolphins form two of these interspersed groups, while the third is represented by the humpback dolphins.

As it turns out, their classification has also had to undergo significant revision in recent years, albeit for different reasons.

Oncillas in the Highlands

Around 5 million years ago, as North and South America finally moved close enough together for a land bridge to form, a species of cat took the opportunity to move south. It found the southern continent devoid of any similar mammalian predators and prospered, leaving descendants from the Caribbean coast to the Magellan Straits.

We do not have a name for this lost species, or know much about where it lived prior to its journey south. However, we can tell that it existed because all of the small cats of South America are missing a pair of chromosomes found in every other species across the world - including the jaguars and pumas with which they share their continent. As confirmed by more detailed genetic analysis, this means that they all shared a single common ancestor in which this oddity first arose.

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.

Squirrels, Advance!

The rapid growth of human population over the last century or so has led to a decline in many species. As I talked about last month, however, some animals can live alongside us even in urban environments, and there are many more than can tolerate us in rural - yet not truly wild - habitats, such as cropland or pasture. Any species that can do this clearly has an advantage, in many cases being able to move into new parts of the world previously inhabited by some similar, but less human-tolerant species. Thus, we can see some native species replaced by foreign invaders, as has happened, for example, with mink in continental Europe and jackrabbits in the American southwest.

In Britain, the most familiar example of this is probably the replacement of our native red squirrels (Sciurus vulgaris) by invasive eastern grey squirrels (Sciurus carolinensis). Red squirrels were once common across the British Isles, but have now vanished from most of England and Wales, surviving in the far north of England and a few pockets elsewhere, but otherwise replaced by the greys. In large part this is due to the greys carrying a virus to which they are immune but the reds are not, but simple competition is another factor.

Wild Mammals of London

Arguably the single biggest threat to the continued survival of animal and plant species is loss of habitat. Even if an animal isn't actively hunted, the ever-growing human population means that there are simply fewer suitable places for them to live. Logging and the expansion of agriculture are probably the biggest factors here, at least in terms of the area affected, but it's hard to argue that the recent growth of urban sprawl isn't another.

The urban environment is obviously a difficult or impossible one for most wild mammals to exploit. House mice and rats are an obvious exception, and there are also domesticated pets, but for truly wild creatures it's a different matter. While it may no longer have (say) bison or wolves, upstate New York is still home to seven species of shrew, three moles, four hares or rabbits, 22 different kinds of rodent, ten bats, nine mustelids, two foxes, and three deer, plus coyotes, bobcats, raccoons, striped skunks, and black bears. Manhattan... not so much.

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"?

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. 

Picking the Right Crevice

It's probably fair to say that bats are commonly associated with in the public mind with caves - there's a reason that Batman's base of operations has been described as a cave since just a few years after his debut. There are good reasons for bats to sleep in caves during the day. Especially in temperate regions, bats keep warm at night by actively flying but, just as it's handy for other small mammals to sleep in burrows, when they sleep they need somewhere that's both secure and has a decent temperature. Even so, to help keep down their energy expenditure many bats in temperate regions enter torpor at night - at a state that's deeper than regular sleep, lowering the animal's body temperature significantly so that it's more like a form of short-term hibernation.

The problem with caves as a habitat, however, is that, in the grand scheme of things, they aren't all that common. Clearly, this depends on the type of landscape you're in, but many places just don't have lots of caves. In the tropics, hanging from a tree branch might well be sufficient, but where the weather is cold, especially in winter, that may not be such a good idea. So bats roost in many other places, too, such as hollows in trees and cracks and crevices in the ground that are similar to, but much smaller than, what we'd normally think of as a "cave".