Sunday 26 May 2024

The Vocabulary of Sperm Whales

It's well known that whales and dolphins can communicate using sound, sometimes over long distances. In some cases, this can involve sophisticated "whalesong" that animals can use, for example, to identify each other, and that may impart other information, too. But there are a great many species of cetacean, and what is true for one won't necessarily be true for all of the others, just as what's true of chimps won't always be true for baboons or marmosets.

We'd expect the most complex messages to come from those species with the most complex social lives. In these cases, it would be useful for the animal to identify not only its gender, fitness, sexual status, and so on, but also which other whales it might associate with, and where it stands in the local hierarchy. Most (but not all) cetaceans live in pods although, for many, we haven't gotten very far in identifying how those are structured. They all, however, have relatively large brains and it can be worth asking, for any given species, just how complex their communication really is.

Sunday 19 May 2024

Antelopine Antelopes: The Largest Gazelles

Grant's gazelle
The word "gazelle", as used in everyday English is a little vague, referring to a general concept of slim, agile, antelopes but not to anything with a precise scientific definition. Strictly speaking, however, it refers to a specific group of closely related animals, and some species that are commonly called "gazelles" strictly speaking aren't. During the 20th century, all true gazelles were placed in a single genus, Gazella, and it's this that defines the more rigid definition of what does and doesn't count. 

In more recent decades, Gazella has been split in three, with the resurrection of two 19th-century names as "new" genera. The original Gazella is widespread, including animals from both Asia and North Africa, but the other two are exclusively African. Eudorcas (literally "true antelope" in Ancient Greek) includes Thomson's gazelle of the Serengeti and its various relatives, while the remaining genus is Nanger, whose name apparently comes from a local Senegalese word for one of the species.

Sunday 12 May 2024

Before Cats Could Purr

Although the differences are obvious when we can see the spots or stripes on their fur, the various species of cat are often very similar in form, and it can be hard to tell them apart based on the skeleton alone. For this reason, through much of the 20th century, all of the "purring cats" except the cheetah were placed in the single genus Felis. That's not the case today, when we distinguish genera not only for the larger purring cats, such as pumas and lynxes, but others that modern genetic evidence tells us are distinct, such as the group that includes the ocelot.

Given this, it's hardly surprising that the same should go for fossil species, too. It may well be that if we had genetic evidence on those, or could even just see their coat colour, we would be more willing to distinguish them but, when all you have is an often fragmentary skeleton, there isn't much to go on.

Sunday 5 May 2024

Squirrels, Advance!

The rapid growth of human population over the last century or so has led to a decline in many species. As I talked about last month, however, some animals can live alongside us even in urban environments, and there are many more than can tolerate us in rural - yet not truly wild - habitats, such as cropland or pasture. Any species that can do this clearly has an advantage, in many cases being able to move into new parts of the world previously inhabited by some similar, but less human-tolerant species. Thus, we can see some native species replaced by foreign invaders, as has happened, for example, with mink in continental Europe and jackrabbits in the American southwest.

In Britain, the most familiar example of this is probably the replacement of our native red squirrels (Sciurus vulgaris) by invasive eastern grey squirrels (Sciurus carolinensis). Red squirrels were once common across the British Isles, but have now vanished from most of England and Wales, surviving in the far north of England and a few pockets elsewhere, but otherwise replaced by the greys. In large part this is due to the greys carrying a virus to which they are immune but the reds are not, but simple competition is another factor.