Do whales go into heat?

By Stéphanie Tremblay

Anyone can recognize a cat in heat, but what about a whale? With the human eye, this is highly unlikely. But how does her male counterpart know that the female is ready to breed? How do females drop the hint… under water? No easy task without clear signs like the bloody discharge observable in dogs, or in an aqueous environment where odours are not so easily transmitted.

“Estrus” is the period during which the female is fertile. When the male and the female are available for breeding, we refer to the “rut”. Unfortunately, few studies offer precise answers regarding the period of fertility in marine mammals, especially cetaceans. Nevertheless, some observations have been made.

To date, only one comprehensive behavioural study of female cetaceans in estrus has ever been published. This study was conducted on captive spinner dolphins and demonstrated that females modify their behaviour when in heat. The conclusion is the following: of all the possible behaviours in this species, only one is exhibited when the female becomes available, i.e. the touching of her rostrum to the male’s genitals. In other words, the female inserts her snout into the male’s genital slit to let him know that she is ready to mate.

Some cetaceans such as the bottlenose dolphin will do a little scouting, that is, they will sniff the female’s genitalia to check whether or not she has entered her period of fertilization. To maximize their chances, males will get ready by remaining close to females, even if the latter are not ovulating, according to observations made by Richard Connor.