Dishonest Bears

Mammals use a variety of means to communicate with one another: vocal, scent, and visual. Even those that are mostly solitary need to do this from time to time, whether to mark out their territories as a warning to others or to attract mates. 

Often these signals need to convey more than the basic message, but also provide some information about the animal that left them. This often includes physical fitness, whether to intimidate potential intruders or to advertise oneself as a sexual partner. At close range, this can be achieved through such things as growing huge antlers, proving that you have the physical capacity to waste resources on something that's otherwise pointless. But, at longer range, a simple indicator of size may be all that's required.

All the World's Antelopes: Reedbuck and Rhebok

Bohor reedbuck

Quite where, within the larger bovid family, the reedbucks belong was long a matter of contention. They are medium-sized antelopes, tending to prefer habitats with plenty of water, distinguished by the fact that not only their visible horns, but also the bony cores on the inside, have transverse ridges running round them. The detailed structure of their teeth has some resemblance to that of the true bovines (that is, cows, bison, and the like) but it's hard to see that as anything other than parallel evolution. 

The most widely followed scheme in the late 20th century placed them with the grazing antelopes, such as sables and their kin, but even then there was a suspicion that this was only because nobody knew what else to do with them. Once we were able to do detailed genetic analysis, it turned out that they are pretty much in a group of their own, not especially close to anything, having diverged from the ancestors of the true grazing antelopes before that group diverged from the goats. Our best guess is that this happened between 16 and 14 million years ago; there are antelopes with longer lineages, but not many.

Hippos in the Tiber

The hippopotamus (Hippopotamus amphibius) is an iconic African animal. While their distribution is very patchy, in part due to their reliance on large waterways, they are found across essentially the whole of Africa south of the Sahara and north of the Kalahari and the South African veldt. A second, endangered, species belonging to the same family, the pygmy hippo (Choeropsis liberiensis), lives only on the southern coast of West Africa, between Sierra Leone and Côte d'Ivoire. 

But hippos were once common in Europe and southern Asia. In the case of Europe, for example, we have fossils from Portugal to Greece, and as far north as the UK. Nevertheless, hippos have never been especially diverse, at least in comparison to groups such as deer or pigs, and they are grouped into no more than around six widely accepted genera. This includes the two that are still with us, and we don't have a large amount of information on three of the others.

All the World's Antelopes: Sables and Other Horse-Antelopes

Sable antelope (male)

The hippotragines are one of several small subfamilies of antelope. Small that is, in terms of number of species, because physically they are quite large. The name literally translates as "horse-goat", but that second part is often used taxonomically as a term for antelopes, so "horse-antelope" might be closer to the intent. It was coined in 1845, partly on account of the physical build of the animals, with their long legs and muscular, horse-like necks.

The subfamily includes the oryxes and gemsbok, but arguably the most horse-like members of the group are the sable antelope (Hippotragus niger) and its closest relatives. Sable antelopes stand around 140 cm (4'7") at the withers, which is almost exactly the official height that separates full-size horses from ponies. They weigh between 160 kg and 230 kg (350 and 510 lbs), which is well within the range for domesticated ponies, indicating a slighter build than animals bred, in part, to bear the weight of humans. Their shape, however, is quite horse-like, an effect accentuated by the presence of a clear mane down the back of the neck.

Otter Whiskers

Four years ago, I posted about whiskers, a feature common to the majority of mammal species, from horses to mice. They are so widespread that they must have evolved very early on, probably well before marsupials diverged from the placental mammals, back in the time of the non-avian dinosaurs. Even so, as humans, we are probably most familiar with them from domesticated animals, especially the carnivorous ones that so often share our homes.

The carnivorans form a natural evolutionary group within the placental mammals, arbitrarily (if conveniently) ranked as an "order". The various living families within this order can in turn be classified as either "feliform" or "caniform", depending on whether they are more closely related to cats or dogs. The dog-like group contains a great many species, which might be more varied than we would think at first glance.

Eocene (Pt 5): Cerberus and the Pangolins

Eurotamandua

Today, when we think of large carnivorous land mammals, we think of such things as dogs, cats, and bears, but, while some of these families do date back to the Eocene, they were not found in Europe at the time. Instead, the dominant group of carnivorous mammals were the hyaenodonts.

While the name translates as "hyena-tooth" due to the description of the first fossils to be found, hyaenodonts were not hyenas, or even closely related to them. They belonged to a group entirely separate from the living carnivorans, and that survived alongside them until as recently as 10 million years ago, near the end of the Miocene. For most of that time, they could be regarded as primitive holdovers, vestiges of their past glory, but in the Eocene they were still at the height of their power.

Having said this, the first hynaenodonts to enter Europe were physically unimpressive, succeeding largely due to the fact that there wasn't much else to compete with. These are traditionally grouped into a subfamily called the "proviverrines", although the details are debated. For one thing, it's not at all clear which family (if any) they are a subfamily of. This is largely due to the higher-level classification having shifted since they were first named, but the membership of the group is also in doubt, since it's not at all clear that all of the traditionally defined species share a unique common ancestor with one another.

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.