SMELLS AND SEX

This section is 2min long, with soundtrack (see also "SILENT CLIPS")

Chapter size: 21 MB (.mpg) or 4 MB (.mov).

Topics and Behaviours covered: Olfactory communication, sexual behaviour, male-male competition, mating queues, lordosis, ear wriggling, genital licking (see commentary below).

Chapter commentary:
(numbers in bold refer to behaviours also shown in the silent clips):
Smells are also an important component of the rat’s world. They are used to identify individuals, their sex, dominance status and oestrous cycle. By now the rats have also probably tuned in to a “clan” smell. A wild rat (1) visiting the colony produces great excitement. This mixture of aggression and fascination is not only because he looks different. His smell does not match that of the clan.

The wild rat is also attracted by the smells emanating from the colony. One smell in particular can provide a frisson of excitement like no other, at least amongst the males: that of a female on heat. Unless mated, female rats come into oestrous every five days or so. Oestrous lasts a few hours and males are attentive to any development. In areas sparsely populated in the wild, males may travel over several kilometres to find females. In densely populated areas where food is abundant, like in farms, or here, females are more easily available. But males have to compete. And the race to find the female is on, sometimes, even before the sun has set.

But the female does not make it easy. Moving around the colony, she invites the males to chase her, and encourages competition. Soon she has a queue following her. It is only when she stops to present her rump in lordosis that the first male in the queue can mate, whilst the others look on. A close examination reveals that her ears are vibrating. This is very sexy - at least for rats (2).

After the male has copulated, he licks his genital area (3) whilst the female moves on followed by the rest of the horde.

But when does solicitation end and harassment begin? And why do females mate with several males anyway? (see next section: "Multiple Partners")...