This section is 1.30 min long, with soundtrack.

Chapter size: 16 MB (.mpg) or 3 MB (.mov).

Topics and Behaviours covered: 22 KHz and 50 Khz ultrasonic calls (see commentary below)

Chapter commentary:
Smell and touch are not the only senses that rats use, and the colony is echoing with sounds that we can’t hear. Rats can communicate in the ultrasonic range, above the 20 KHz upper limit of our hearing. Whilst the function of these vocalisations are mostly unknown, most are produced socially. Rats have three kinds of calls in at least two different ultrasonic frequencies.

This long 22 KHz call, whose frequency has been lowered to make it audible, can be emitted by subordinates, and may express fear or even pain. At other times it may be used as a warning or an alarm call. It is also emitted by females prior to mating and by males after ejaculation.

Two other types of calls operate at even higher ultrasonic frequencies, in the 50 to 100 KHz range.

This call is heard in a mating context, often when males follow females. In some cases it seems to make the females more likely to be sexually receptive.

This less complex call can be heard in an aggressive context.

And indeed there were some signs of conflict developing between our rats...(see next section).