Sexual maturity in whales and dolphins

Aerial shot of killer whales

Aerial shot of killer whales

Ah puberty, those awkward years on the road to sexual maturity. It’s not clear if whales and dolphins must also suffer the dramatic ups and downs of the human teenager, but some do have to suffer big differences between the sexes when it comes to the actually timing of sexual maturity.

In several posts we’ve encountered the term sexual dimorphism, which is a fancy term for differences between males and females. For whales and dolphins, mostly whales, sexual dimorphism tends to be mostly related to size. Female baleen whales tend to be slightly larger than males, meaning men like the large ladies and aren’t shy about it. Because if male baleen whales didn’t go for larger mates that wouldn’t work well for courtship and evolution would have had to come up with a different strategy by now to ensure propagation of the species. And in the largest toothed whales the males tend to be much larger than the females.

But I slightly digress. This size difference leads to a difference in the timing of sexual maturity. According to the Encyclopedia of Marine Mammals, male sperm whales are much larger than females and bigger animals take a longer time to reach sexual maturity. “The estimated age at attainment of sexual maturity for the female sperm whale is from 7 to 13 years and for males, is approximately 20 years.” A similar timing difference is found in killer whales and pilot whales. Talk about awkward.

The encyclopedia doesn’t say if the ladies wait for their cohorts to age gracefully into sexual maturity or not. I’m guessing they don’t bother and accept passes from the “older men” swimming about. Okay mid twenties and thirties isn’t old, but if the female is 7 to 13, well it’s all relative. Dolphins on the other hand don’t have to worry because they are closer in size and reach sexual maturity around the same time.

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