Splitting the Troop

Primates are, for the most part, social, group-living animals. This underlies many aspects of human behaviour and likely played a role in our development of intelligence. Often, these groups have a fission-fusion structure, where new members come and go, but, in other species, they can be long-lasting and stable. Either way, just as with nation-states or tribal societies among humans, nothing lasts forever. Groups die and new groups form.

This can be due to disaster or misfortune, but it can equally well be due to success. If a group becomes too large, there may no longer be enough food in the local area to keep it healthy, or parasites or disease may spread too rapidly within it. Or it may simply become too large for dominant individuals to control. In fission-fusion societies, this may lead to a temporary break-up into local subgroups that otherwise remain in contact. Sometimes, however, the pressure is too great and the only solution is for a new group to form.

Viverrids: Civets of Southeast Asia

Large Indian civet

Our definition of the Viverridae family has, as I noted previously, undergone some ups and downs over the centuries. It was first named, in 1821, for the genus Viverra, which, when it was first described, had contained five species. Even by 1821, four of those had been moved elsewhere - and three are no longer even in the family. But, by the rules of scientific naming, unless we scrap the family entirely, Viverra must remain within it. Which leaves one species that, in a sense, defines the family, and against which everything else in it is compared.

That species is the large Indian civet (Viverra zibetha). Thus, even though "viverra" literally means "ferret" in Latin, this means that we can reasonably call the Viverridae "the civet family", as I will be doing from here on in.

The Air Conditioning in Your Nose

The nasal cavities are not mere holes running through the head. Anatomically, at least, that's broadly true at either end - in the vestibule immediately behind the nostrils, and in the nasopharynx above the throat. But in between, in the area above the mouth and separated from it by the palate, the air instead must pass through defined channels. 

These channels are formed by the "conchae", projections from the outer side of each nasal cavity stretching almost to the inner surface, so that most of the air is forced through the narrow slots between them. These conchae are, in turn, formed by the turbinate bones, delicate, paper-thin, sheet-like structures rolled up like a scroll, and covered in the same sort of fleshy lining that we find in, say, the trachea (windpipe).