Running Hyenas of Greece

Chasmaporthetes

Mentioning a "hyena" today likely brings to mind the image of a muscular, aggressive, scavenging creature, probably with a spotted coat. This, the spotted hyena (Crocuta crocuta), is, however, only one of three species alive today, with the two lesser-known ones being smaller and less aggressive. In fact, the hyena family includes a fourth living species as well, although this isn't always referred to as a "hyena" because it's really only dangerous to termites and can't crack bone like "true" hyenas can.

Four living species isn't very many for a family of mammals but, like many other such small groups, there is a long fossil history that includes a great many extinct forms. These varied in form even more than the living species do. At one extreme are animals larger and stronger even than the living spotted hyena, while at the other (all living very early on) are small tree-climbing animals that looked more like civets. 

Somewhere in between are the "running hyenas".

Viverrids: Genets of Northern Africa (and beyond)

Common genet

At the dawn of scientific taxonomy in 1758, the group of animals that would later become the civet family included four species that we still recognise today. Two of these - skunks and mongooses - were later moved elsewhere, and one of the others was, of course, the defining species of the family, the large Indian civet.

The other was the common genet (Genetta genetta). Frédéric Cuvier split the genets off from the civets proper in 1816, recognising just one other species - which molecular evidence has since shown isn't a viverrid at all, although this wasn't obvious even in the late 20th century. His basis for the distinction was that genets have a much smaller scent gland than civets, although he conceded that the secretions it produced were, in his words, "très manifeste". 

Just Cold Enough

Northern meadow jumping mouse

Hibernation is one of the most effective means that mammals can employ to withstand harsh winter temperatures. Many mammals, especially larger ones, use other means, such as growing a winter coat, caching food, or simply moving somewhere warmer, but, if the goal is to reduce energy requirements when you can't get out to feed, hibernation is the most effective means of doing so.

During hibernation, bodily metabolism slows right down, so that an animal may need as little as 1% of its usual calorie supply to stay healthy. This has negative consequences, so that the animal does need to wake at intervals to stave them off, and how often this happens varies from species to species. In this respect, true hibernation can be distinguished from shorter, often daily, bouts of torpor by the fact that each "sleep" can last for weeks or even months. 

Staying Away from the Boys

Many large, hooved mammals live in herds. This has obvious advantages of safety in numbers, spreading the work of looking out for predators, as well as benefiting from the knowledge of more experienced herd members as to the best places to find food or shelter. The structure and composition of these herds vary from species to species, but one common trait is that males and females often form single sex herds that travel apart for much of the year.

This is referred to as "sexual segregation", and was first formally described by Charles Darwin in The Descent of Man. It isn't unique to mammalian herd animals, being seen in everything from fish shoals to bird flocks, as well as in non-hooved mammals (dolphins, bats, primates, etc.) Most zoological research, however, has tended to focus on large cloven-hooved mammals, such as deer and antelopes.