Antilopine Antelopes: Dwarf Antelopes of southern Africa

Steenbok

The "antilopine" subfamily of antelopes, so named because it happens to include the first animal scientifically described as an antelope rather than a goat, is itself divided into at least two major branches. There may or may not also be minor ones, depending on what you think is worthy of naming, but the two main ones are quite clear, and perhaps separated from one another around 12 million years ago towards the end of the Middle Miocene.

One of these groups contains the gazelles, along with the springbok, some other gazelle-like animals, and that "first" antelope mentioned above, the blackbuck. These are, for the most part, smallish slender, fast-running antelopes living in arid or semi-arid habitats in both Africa and Asia. The second group are the dwarf antelopes, found only in Africa and quite visibly different from gazelles. 

Unravelling the History of Seals

Allodesmus, a desmatophocid

Trying to determine the largest patterns in evolution can be a daunting task. Here, we often want to look at large numbers of species, comparing the living ones and filling in the gaps with fossils that are often incomplete, ambiguous, or that simply haven't been discovered yet. As a result, there are several big transitions in mammalian evolutionary history that we'd like to get a better look at. Bats are a significant case in point; their small fragile skeletons don't preserve well if we want to see more than teeth, and how they developed their forelimbs into wings remains obscure.

With some groups, however, we do have sufficient fossil evidence that we can look at a whole group of animals and get some idea, not just of how it originated, or where it fits in the larger mammalian family tree, but what ups and downs it has faced over the course of its existence. This can tell us what alterations in climate or geography drove changes within the group and how and when particularly evolutionary innovations developed.

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.

Scratching the Surface

The environment of the Earth is shaped, not just by sunlight, wind, and the geography of mountains and seas, but by the living organisms living on it. This process has been described as "ecosystem engineering", and it inevitably affects far more than the organism that's doing the modification - sometimes negatively, but often in ways that are generally beneficial.

In its broadest sense, ecosystem engineering can include changes to a habitat caused by the mere existence of an organism. The existence of multiple trees in close proximity creates a forest, which is a very different sort of environment to, say, a grassland, and this obviously has huge effects on what the resulting habitat is like for other organisms. One could also think here of coral reefs or the nutrient-rich hotspots created by a whale carcass sinking into the depths.

Antilopine Antelopes: Almost-Gazelles of Tibet

Tibetan gazelle

It's often the case that the common name of a type of animal in English does not map directly to a scientific understanding, especially once we add modern genetic discoveries into the mix. So it is with the word "gazelle", which derives from an Arabic word that literally means something like "graceful" or "slender" and is used to refer to a range of relatively slim, fast-running antelopes. 

In a stricter, scientific sense, gazelles would really only include those species closely related to the genus Gazella, short-coated animals, often with dark stripes down the side, and that tend to live in hot deserts or semidesert regions. Even this excludes animals such as springboks, since they are less related to the true gazelles than is, say, the blackbuck. Most true gazelles live in Africa, but there are some in Asia, mostly in the Middle East, but with one reaching as far east as northern China. However, a second group of animals commonly called "gazelles" also lives in Asia, and not somewhere that most Westerners would generally associate with such animals.

Oligocene (Pt 10): The First Elephants with Trunks

Barytherium

During the Oligocene, Africa remained an island continent, separated from Asia by the Tethys Sea that ran from the Atlantic, through what is now the Mediterranean, and then south of the Zagros Mountains to connect with today's Persian Gulf. The Tethys was narrower in the Oligocene than it had been in the preceding epoch, due both to Africa's slow northward movement and the fact that sea levels were lower, but it was still substantial. As a result, the large herbivores of Eurasia, such as pigs and rhinos, had yet to enter Africa, resulting in quite a different fauna there.

The same was not, however, necessarily true of smaller mammals, some of which had been there for some time, more able, perhaps, to be accidentally carried across on floating vegetation. (A rare event, to be sure, but tens of millions of years gives a lot of opportunities to get it right). There may not have been antelopes in Africa yet, but there were certainly rodents.

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.