Sunday, 4 June 2023

Social Posting - Bear Style

Communication between animals is an important feature of all mammalian species. For those living in groups, it can help to maintain social bonds and provide urgent information, such as the unexpected arrival of a predator. If a mother has young, she may need to find them if they become lost or attend to them if are distressed, and so on. Even solitary adult animals need to communicate with others of their species, whether it be to mark out a territory and ensure that others don't poach their food source, or to find a mate at the appropriate time.

At least among mammals, there are two primary modes of communication that are generally studied by researchers. Perhaps the more obvious of these to we humans is vocal communication, since that's the main one we used in pre-literate societies. Not all species are especially vocal, but many are, and some are using sound outside of the human hearing range - such as the ultrasound squeaks of many small rodents such as mice. One estimate suggests that around 95% of mammal species use acoustic communication and this may be on the low side (it's 100% in birds and 90% in amphibians, but apparently less than 5% in reptiles, suggesting that it has evolved at least three times).

Saturday, 27 May 2023

When the Desert is Too Dry

The round-tailed ground squirrel lives
further east, and is not threatened
Many mammal species are territorial, carving out a patch of land for themselves which they then defend from same-sex members of their own species. Typically, they are less bothered about members of the opposite sex, for obvious reasons, and such territories will often overlap. Male territories tend to be larger than those defended by females, making it easier for them to meet as many females as possible. 

The size and relative location of such territories naturally vary between species, but also depend on the local conditions of terrain, climate and so on. The harder it is to find food, for instance, the larger your territory will need to be. As young animals grow up and leave home, they will need to find unoccupied territories to inhabit, or else somehow drive an existing resident out and take over. Males commonly travel further than females so that they don't end up with only their sisters or close cousins as potential mating partners, although there are a few species where it works the opposite way around.

Sunday, 21 May 2023

The Raccoon Family: Kinkajous - the primate-like "raccoons"

Raccoons proper are well-known animals, both familiar and distinctive even to those of us living in countries where they are not native. Among the other members of the raccoon family, coatis are at least familiar to people in the southern US. Ringtails ("cacomistles") are probably more obscure, being smaller and mostly active high up in trees at night, but at least, they too, live in the US. The remaining species, however, live only in Latin America and it's probably fair to say that they are much less familiar to English speakers than those groups with more northerly representatives.

Perhaps the most distinctive, and certainly the most studied, of these is a genus with just one species: the kinkajou (Potos flavus). It was first scientifically described by Johann Schreber in 1774, in an earlier volume of the book in which he would later describe (among other things) cheetahs, snow leopards, and bobcats. While he was understandably clear those were all cats, the identity of the kinkajou was not so obvious. In the days before Darwin, this may not have held any deep meaning for him, but his conclusion was that his new animal was a kind of lemur.

Sunday, 14 May 2023

Oligocene (Pt 2): Europe's Big Break

The dawn of the Oligocene is marked by a sudden cooling of the Earth's climate, of which the most obvious consequence was the creation of the Antarctic ice sheets. These locked up so much water that sea levels dropped worldwide, reshaping coastlines. Nowhere were the consequences of this more apparent than Europe, despite its great distance from Antarctica.

Prior to the Oligocene, it would have been possible for a hypothetical traveller to sail from what is now the eastern Mediterranean, through the Paratethys Sea (now the Black and Caspian Seas) due north and into the Arctic Ocean. The body of water that made this possible, the Turgai Strait, was already becoming shallower and narrower as the Oligocene approached, and the sudden dip in sea level finished it off altogether, closing off the sea route that had once run along the eastern flank of the Ural Mountains. 

Sunday, 7 May 2023

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.

Sunday, 30 April 2023

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. 

Sunday, 23 April 2023

The Raccoon Family: Cacomistles

While true raccoons and coatis were first scientifically described during the 18th century, the third member of the raccoon family that's native to the United States was not described until 1830, by Heinrich Lichtenstein - who later went on to found the Berlin Zoo. It's unclear (at least to me) exactly what he thought the animal was. So far as I can translate the original German, his original description says that it's somewhere between a civet and a coati in appearance, but also looks quite like a fox. Based on which, he gave it the scientific name Bassaris astutus, a mixture of Greek and Latin that roughly translates as "cunning fox".

The scientific name didn't stand, because it turned out that the first part of it had already been used for a kind of butterfly. Furthermore, while he originally referred to the animal by its Spanish name "cacomixtle", since the specimen he knew of came from somewhere near Mexico City, in English we now call it a ringtail (Bassariscus astutus) or, less accurately, a "ring-tailed cat". Even so, in many parts of the US, an Anglicised form of the Spanish name is still in wide use.