Sunday, 25 June 2023

Pennsylvania Elk with a Wyoming Accent

We're familiar enough with the idea that humans in different parts of the world speak with different accents and vocabulary, even if they are otherwise speaking the same language. ("Faucet, railroad, trashcan, truck, don't say 'sidewalk' or you suck.") This is true of all languages that are spread over a sufficiently large geographic area; for instance, European and Brazilian Portuguese are at least as different as UK and US English. Even within a single national dialect, we can often distinguish local accents and some differences in spoken grammar and terminology - few native English speakers could confuse a blue-collar Texan with a New Yorker.

Since animals don't have language in the human sense, we might not expect the same thing to be true of them. Animals have distinct vocal repertoires, but these are largely instinctive, and a cat goes 'miaow' regardless of where it lives. (Well, arguably it goes 'meow' if it's American and 'nyan' if it's Japanese, but you get the point). It's perhaps not surprising that there is variation between individual songbirds of the same species, or among cetaceans, given the complexity of their calls, but we might not think of it among terrestrial mammals.

Sunday, 18 June 2023

The Raccoon Family: Olingos

Northern olingo
While it's probably fair to say that the members of the raccoon family unique to Latin America are less well-known to those of us in the English-speaking world than are their northern counterparts, the olingos are likely the least well-known of all. Raccoons, coatis, and kinkajous were all scientifically described back in the 18th century - at least in general terms, if not all of the species recognised today. The cacomistle, while known to the Aztecs, didn't reach the scientific literature until 1830, but we have to wait another four decades before anyone European seems to have noticed the olingo.

This was William Gabb, who had been asked by the government of Costa Rica to conduct a three-year biological survey of the Talamanca region, on their eastern border with Panama. He completed the survey in 1876, but died two years later from malaria contracted while on the expedition. His real expertise was in dinosaur fossils so when he discovered a previously unknown species of living mammal, he sent the skull and pelt to Joel Asaph Allen at Harvard. Granted, he was an ornithologist (he would later help to set up the Audubon Society) but he did also have an interest in mammals, and was able to identify the animal as a new member of the raccoon family "as unlike [raccoons and coatis] as these... are unlike each other".

Sunday, 11 June 2023

A Tale of Three Ground Sloths

Today, sloths are slow-moving tree-dwelling animals found only in South and Central America. For most of their evolutionary history, however, the majority of sloths have been ground-dwellers, in many cases too large to have climbed a tree even if they had wanted to. In comparison, tree sloths are a relatively recent evolutionary development. 

Ground sloths, however, are not a single type of animal in the strict biological sense. This is because the two-toed and three-toed sloths that we have today are not especially close relatives, last sharing a common ancestor at least 28 million years ago. In fact, tree sloths evolved twice, in separate branches of the sloth family tree, and some ground sloths were more closely related to one or the other. On this basis, we used to divide the ground sloths into two families, but the fact that some of lived recently enough that we can recover and analyse DNA from their fossils gave us some surprising detail and a key 2019 study suggested that we should consider there to be no fewer than six different families of ground sloth.

So whatever we can say about one sort of ground sloth isn't necessarily true of all the others, even on quite a broad scale.

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).