All the World's Antelopes: Gemsbok and Oryx

Gemsbok

As I have discussed previously, there is no such thing as an antelope, in the strict scientific sense. That is to say, they do not form a natural group of organisms, being defined only as those members of the cattle family that aren't sheep, goats, or obviously cow-like. This covers a wide range of animals, some closely related, but others much less so.

I've previously looked at the various species of gazelle, and at the spiral-horned antelopes (which are actually "bovines"). Now it's time to look at the others.

Linnaeus' original catalogue of scientific names, published in 1758, included five species that we would now call antelopes. In that catalogue, they are listed as goats, based primarily on the shape of their horns, and therefore sit alongside the chamois and ibex. Two of these, the dorcas gazelle and the blackbuck, are now placed within the gazelle subfamily, while two others are relatively small "dwarf antelopes", which I will cover later.

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.

Euplerids: Madagascar's Top Mammalian Carnivore

The native mammalian carnivores of Madagascar are mostly obscure to those of us in the West. The one possible exception, thanks to the Madagascar animated film franchise, is the fossa (Cryptoprocta ferox). Often spelt with a single 's', especially in more modern sources, and typically pronounced "foosa", this is the largest and most potentially dangerous of all the island's native mammalian predators.

Having said which, it's not especially big compared with predators elsewhere. There is little need to be a large carnivore when the island does not have, for example, any native antelopes. On average, they are about 75 cm (30 inches) in body length, not counting a cat-like tail that adds about the same length again. Adult females weigh around 6 kg (13 lbs), while the largest males can reach 8.5 kg (19 lbs), about the same as a West Highland terrier. 

Exactly where they fit within the mammalian family tree was long a source of confusion, given a mix of features resembling a range of other animals. When English zoologist Edward Turner Bennett first described the animal in 1833, he considered it to be a type of unusually large civet. So it remained for a hundred until it was moved to the cats in the 1930s, back to the civets in the 1940s, and then to the mongooses in the 1990s. Over the next ten years or so, arguments continued back and forth between all three of these options until genetic studies finally settled the matter in 2003. 

The First Cows In Europe?

When we look at scientific lists of animals, we usually see them placed into neat groups based on their relationships: families, subfamilies, and so on. These are, however, entirely human constructions, and nature is rarely so tidy in reality. Even for mammals, which have been more thoroughly studied than, say, fish or invertebrates, disagreements can arise, and details can change.

At least in the case of mammal groups above the species level, the relationships are faily well understood by this point, thanks to the advance in molecular and genetic studies over the last couple of decades. Disputes are more likely to arise when we question how broadly we should define a particular group, and what taxonomic level it might have. (The latter, of course, are entirely artificial; the cat family is provably a 'real' thing, but the fact that we call it a 'family' rather than giving it some other rank is essentially arbitrary).

This becomes a much bigger issue when we look at animals we know only from fossils. For one thing, we will have fewer, and generally less complete, specimens to examine. Furthermore, unless they are really recent, genetic analysis is out of the question. But, on top of all of that, when we travel back in time, lines become inherently blurred. There's always going to be the question of where exactly the 'not yet X' becomes 'X', even if we had perfect information about them. Which we don't.

Two Million Years of Llamas

The camel family is one of the smaller mammal families in the present day, containing just seven species, four of which are domesticated. Thus, if you don't consider, say, dogs to be distinct from wolves at the species level, one could reasonably argue that there are only four. Although these are all considered to belong to the same subfamily (with all the other subfamilies being extinct), they still fall into two branches: the 'true' camels in the Old World, and their counterparts in the Americas.

It should come as no surprise that members of the family are noted for their ability to survive in arid environments with minimal water. They are, for example, more efficient at absorbing water from their stomach than ruminants such as cattle and deer, and genetically resistant to heat stress and ultraviolet radiation. Nonetheless, while the word "camel" doubtless conjures up an image of one or more of the three Old World species (that is, the dromedary and the wild and domesticated versions of the Bactrian camel), the family also includes those four American species.

The Genomics of Yellow Bats

In terms of species, bats are the second-largest order of mammals, after the rodents. New species are identified all the time, due in part to the relative difficulty of closely examining night-flying mammals, many of which sleep in hard-to-access caves. The current total stands at over a thousand, representing over 20% of all known mammal species. 

Within this huge group, there is, perhaps, rather more diversity than many people realise. While bats have probably not received the same level of attention as some other mammal groups, scientists have nonetheless long attempted to disentangle the relationships between all these subgroups. (Also, when I say they have received less attention, there's a mammal-centric bias here; it's probably still a lot better than, say lizards, let alone millipedes or the like). 

Euplerids: Falanoucs and Fanalokas

Fanaloka

The relationships of the native Madagascan carnivores were uncertain before the advent of genetic testing at the end of the 20th century. The majority were assumed to be mongooses, since that is very much what they looked like, but three species didn't quite fit the pattern. 

Two of these were, so far as anyone could tell from their physical appearance and habits, civets. They were often placed in their own subfamily, reflecting their distance from other civets, but nonetheless, they were thought to belong among the viverrids. Following genetic studies in 2003, however, it became clear that they belonged in the same group as (i.e. shared a unique common ancestor with) the Madagascan "mongooses". Since some of them clearly weren't mongooses, and since they had diverged from the real ones so long ago, the subfamily was split off and promoted to full family level, now including both the mongoose-like and civet-like species.

Eocene (Pt 4): Ancient Beasts of the European Archipelago

Propalaeotherium

The story of the evolution of the horse is one of the most commonly cited examples of evolutionary trends, often illustrated by a series of increasingly horse-like animals with an ever-reducing number of toes. The animal typically shown at the start of that series is, depending partly on the age of the picture, either Hyracotherium or Eohippus.

Hyracotherium was long regarded as the earliest known member of the horse family. In recent decades, it has become apparent that it wasn't really a horse, in the sense that modern horses don't descend from it or its relatives, and today we call the family it belonged to the palaeotheres. The North American Eohippus, on the other hand, despite long being thought to be identical to Hyracotherium, probably is a horse. The confusion between the two means that it's often difficult to tell which is being referred to in older sources. 

Looking for Leaves: the Travel Routines of a Koala

Animals inevitably have a preference for the particular habitat in which they live. Factors such as climate and the presence of suitable hiding and sleeping places are important, along with the presence of suitable food. While climate is less of a problem, food and shelter may be patchily distributed, with insufficient food in any one place to support the animal for long. The animal may also wish to avoid sheltering in any one place for too long, less predators find it easy to locate, and it also makes sense to travel between different patches of land if you want to find mates.

Thus, it can be important to know not merely which habitats a particular species of animal prefers, but how it moves about within that habitat to use to its best advantage. Does it tend to revisit particular patches of ground, and if so, how often? A herbivore, after all, wouldn't want to head back to a given place before whatever it had eaten there had had a chance to regrow.

Euplerids: The Not-Mongooses of Madagascar

Ring-tailed vontsira

There are around 35 currently recognised species of mongoose, spread between Asia and continental Africa. For the most part, they look fairly similar, with most being instantly identifiable as such. For most of the 20th century, however, they were also thought to live on Madagascar. In the last couple of decades, genetic studies have revealed that the Madgascan species, while related to the mongoose family proper, belong in a group of their own. That's partly because they diverged so far back in time, but also because that group includes some animals that manifestly aren't mongooses.

Today, in order to distinguish what we used to call "Madagascan mongooses" from the real sort, we tend to use the local Malagasy word and describe them as "vontsiras".

Not Leaving Home: Wolves on the Serengeti

There is a popular belief that wolf packs are led by an "alpha male", a dominant individual who directs the pack and monopolises breeding opportunities through the force of his masculine aggression. It's all-but universal in modern stories about werewolves, and has even crept into the messaging of online influencers, apparently following the reasoning that anything true of wolves must necessarily also be true of humans.

It is, however, simply not true.

Having said which, it used to be a serious scientific theory, derived from behavioural studies on captive wolves conducted in the mid 20th century. Better studies at the end of the century, looking at wolves in their natural habitats and not stressed by close confinement with non-family members in zoo cages, revealed the truth: not only is the dominant female at least as important as the male, but the correct word for that dominant pair isn't "alpha", it's "parents".

A Brief History of Zokors

The rodents are the largest group of mammals, in terms of number of species, and they are divided into several families. Some of these are familiar, such as the mice, voles, squirrels, and gophers, but others are much less so, at least to the majority of people in the West. This includes, for example, the zokors.

There are a couple of reasons why zokors are not as well-known as some other rodent groups. For one thing, they only live in northeast Asia, an area that it's fair to say doesn't receive much attention in the Western world. For another, even if you did live there, you wouldn't see them very often, because they are burrowing animals that don't like coming to the surface if they can help it. Rather like moles, you might see the mounds of earth they leave, but not often the animal itself.

Strange Carnivores of Madagascar

Madagascar is the fourth-largest island in the world, almost three times the size of Great Britain, or half again the size of California. We should not be surprised, therefore, that it has a considerable amount of native wildlife. However, it's also noteworthy that it has been an island for a very long time - certainly for far longer than Britain has been.

In fact, Madagascar became an island around 91 million years ago, over 20 million years before even the likes of Tyrannosaurus appeared on the scene. Moreover, this was when it split away from what was then the island of India, with its break from Africa being almost twice as far back in time. But, even if we take that younger date for the beginning of its isolation from any sort of 'mainland', it's well before any of the sort of mammals we would recognise today had evolved. There's no equivalent here of mammoths nipping across the English Channel.

Covid and the Landscape of Fear

Left to their own devices, animals will wander about wherever there is food or other useful resources to be found. They would be limited only by the physical properties of their landscape, such as the inability to cross a wide river or the presence of a barren mountain range. Reality, of course, is never quite this simple.

The earliest use of the term "landscape of fear" that I could find on a quick search referred to a study about how female college students felt while walking particular routes alone after dark. Put in this context, one can well understand why people don't necessarily pick the simplest or most direct route to their objective, and why there are certain places one might simply wish to avoid altogether.

Viverrids: The Odd Ones Out

Binturong

Most viverrids have a similar appearance: slender, long-snouted animals, many of them spotted or brown-coated. One, however, stands out as particularly distinctive. This is the binturong (Arctitis binturong) and it's the largest species of "civet", with a total body length ranging from 61 to 96 cm (24 to 38 inches) and weighing between 9 and 20 kg (20 to 44 lbs), similar to small dog such as a Jack Russell or border terrier. Moreover, they appear somewhat larger than they are because, unlike other civets, they have a thick shaggy coat that obscures their actual body.

They are mostly black in colour but with grizzled fur that makes them look grey, and prominent white whiskers. The tail is long and prehensile, and the feet have large, rough pads, giving them an enhanced grip. In other respects, however, they are civet-like, with the same general pattern of teeth and other detailed anatomical features, including a simple perineal scent gland.

Eocene (Pt 3): Sword Teeth and River Pigs

Anoplotherium

Today, by number of species, the most successful group of large mammalian herbivores are the terrestrial artiodactyls - broadly speaking, the "cloven-footed mammals". Except for Australia, they are a key element of almost any mammalian fauna. Their first great burst of diversity occurred during the Middle Eocene, over 40 million years ago, when many new forms appeared across the Northern Hemisphere, some unique to particular places, others more widespread.

Most, however, were nothing we would recognise today. There were as yet no cattle, antelopes, deer, or pigs, and many of the creatures that did live that far back left, so far as we can tell, no living descendants.

Hedgehogs versus Killer Robots

Hearing is a key sense for just about any mammal species. While humans, and primates in general, place particular importance on vision, this isn't true for many other mammals. Granted, that's usually because of the significance of scent, which we humans are particularly bad at, but hearing can hardly be discounted, even for us. 

The range of hearing, however, varies dramatically between different species. For humans, the typical range is from about 20 to 20,000 Hertz, which covers about 10 octaves (middle C is 261 Hz) although the upper range drops off with age, and there is some leeway under perfect conditions. Many mammals can hear outside this range, with smaller animals, in particular, being able to hear higher notes. This can be of more than academic interest, since it means that the soundscape a particular animal lives in may not be the same as our own, and that can have a bearing on conservation - we might think somewhere is quiet and peaceful, but other species might not agree.

Most research on the effects of human-created noise on animals has been conducted on whales and birds, which are likely to be particularly affected. If we want to extend it to other animals, it could be useful to know just what their hearing range is, and one recent study asked this question specifically of hedgehogs (Erinaceus europaeus).

I have discussed hedgehogs before, but here's a quick summary. There are about 18 species of living hedgehog found across Eurasia and Africa, but here we are talking about the one simply called "the hedgehog" in British English, because it's the only one found in that country - and, indeed, across the rest of western Europe. They are not at all closely related to porcupines, which are rodents, with the spines being a case of parallel evolution. Instead, the hedgehog family (which also includes some spineless species that aren't normally called "hedgehogs") is most closely related to the shrews, partly explaining their similar diet of insects and worms.

The European hedgehog is not an endangered species, but its population has declined dramatically in recent years. In the UK, for example, numbers are thought to have fallen by about 20% between 2010 and 2020, and similar figures apply to other countries. Premature deaths are largely due to road traffic, but poison bait intended for rats can be another factor, as can robotic lawnmowers. 

It was the last of the above that motivated the recent hearing study. The researchers were not interested in the general effect of human-created noise on hedgehogs (that they try to cross roads suggests this may concern them less than it might) but on whether lawnmowers, and similar garden devices such as strimmers, could be made safer for hedgehogs. They reasoned that fitting the devices with ultrasonic emitters creating an annoying sound would warn the animals, allowing them to flee before being killed.

For this to be acceptable, the sound emitted has to be too high-pitched for humans to hear, or nobody would ever use them. Ideally, however, you don't want it to alarm cats or dogs either, and that puts more constraints on the frequency. A cat, for example, can hear sounds up to at least 65,000 Hz, roughly two octaves higher than the highest-pitched sound a human can detect. If hedgehogs can't beat that, ultrasonic screamers won't be of much use to families with pets.

The study was conducted on 20 injured, sick, or orphaned hedgehogs delivered to a wildlife rescue sanctuary in Denmark. After recovering from whatever their original complaint was, and having their ears examined to rule out hearing problems, they were sedated and fitted with electrodes under the skin to monitor the activity in their auditory nerves and brainstems. Afterwards, they got to relax on warmed heat pads (of the sort you might use for your cat) before being fed and eventually released into the wild.

 All of this is designed to minimise the stress and discomfort of the animals being studied. But it does obviously have limitations. Most notably, although it should show what sounds hedgehogs are capable of hearing, it doesn't demonstrate what they respond to. If, for example, a sound is relatively quiet, the animal might ignore it even if it can hear it; in birds, the difference between what they can hear and what they'll respond to is about 20 to 30 dB, which is quite significant. 

To test that, we would need to keep the hedgehogs in captivity for much longer, but they become particularly stressed if that happens. Which, even leaving aside any issue of unintended animal cruelty, could affect the results; a stressed animal will not respond in the way that a comfortable one will. So we have to do what's practical, with the hedgehog's interests in mind.

The result of this was that hedgehogs' peak hearing sensitivity was around 40 kHz. This is definitely ultrasonic - a full octave beyond even the highest pitch that most humans can hear. But it is similar in pitch to a dog whistle and so clearly audible to them (regardless of breed and size, if you're wondering) and even more so to cats. Still, while this demonstrates that hedgehogs can hear ultrasound, which we already knew, it's merely the peak brainstem response. That is to say, it's the pitch at which you can play the sound at the lowest volume and still have the animal able to hear something. Raise or lower the pitch, and you'll have to up the volume before the hedgehog will hear you, but it still might.

There has to be some limit, some highest pitch the hedgehog can hear if you blast out the sound loud enough. The study was not able to find out what that was, but the good news is that the highest tone they could produce still registered in the hedgehog's auditory nerves. This was 85 kHz, roughly three notes on the scale above the highest tone a cat can hear. The sound had to be quite loud at that point, so the ceiling probably doesn't go much higher, but the point is that it should be high enough.

You should, in other words, be able to create a sound at, say, 70-75 kHz that will alarm a hedgehog and save it from a lawnmower, but not frighten a cat.

Furthermore, the researchers were also able to examine the ears of a hedgehog that had arrived at the sanctuary with unsurvivable injuries from a rat trap, and had had to be euthanised. This showed that the malleus bone of the middle ear was connected to the bony ring around the eardrum by a tough, fibrous structure. This would increase the overall stiffness of the chain of bones in the middle ear, and is associated with ultrasonic hearing in other mammals, such as rodents and bats. 

What we can't tell from this sort of study is why hedgehogs would want to hear ultrasound in the first place. They are solitary animals, so communicating with each other, while not impossible, isn't likely to be as important as it is in, say mice. Indeed, so far as we know, they don't make many sounds of any kind, although it's conceivable that we just haven't been listening at the right frequencies. 

Another possibility is that it enables them to hunt for insects that make sounds in this range. This has previously been suggested for four-toed hedgehogs (Atelerix albiventris), a species native to the savannah and open grasslands south of the Sahara. We don't know that it would also be true of the European sort, but it's plausible, and it doesn't rule out other uses for the same sense.

Either way, the research team now plans to see if they can use this information to develop ultrasonic repellents to fit on those killer robot lawnmowers.

[Photo by Michael Gäbler, from Wikimedia Commons.]

The Thrush-beaked Consort Bird

A modern thrush

This post will be the latest as of 1st April, so it's that time again...

About 40% of all living mammal species are rodents. Over a third of those that aren't are bats, leaving just 38% belonging to any other group - primates, cloven-hoofed mammals and all the rest. These are, at least in terms of speciation, clearly very successful body plans.

But the bias is even stronger with birds. A whopping 60% of living bird species belong to just one order: the Passeriformes. The chances are that, if you think of a "typical bird" the image that pops into your head is of a passerine. There are about 140 different families of passerine (the exact number being a matter of taste among ornithologists), of which 123 constitute the songbirds.

Viverrids: Long-tailed Palm Civets (and coffee...)

Common palm civet

While the palm civets do, arguably, form a single group of related animals, they are spread between two subfamilies that diverged at least 23 million years ago, at the dawn of the Miocene epoch. This is only about 5 million years after the split between the true civets and the genets, so it's fair to say that the two subfamilies are distinct. The subfamily that includes the animal originally known in the West as a "palm civet" is that of the paradoxurines.

The animal in question is now known simply as the common palm civet (Paradoxurus hermaphroditus). The alternative name of "Asian palm civet" is also often seen, although it has the disadvantage of not clearly distinguishing it from all the other palm civets that live in Asia. Which, since there are no palm civets outside of Asia, isn't really narrowing it down much.

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.