Largest animal testes
Eubalaena, Right whale
500 kilogram(s)
Not Applicable ()

In whales, the testes are usually internal, and so only visible in dead specimens whose abdominal cavity has been cut open. The largest testes of any animal species are those of the right whale (genus Eubalaena), each of which may weigh as much as 500 kg (1100 lb) and produce as much as 4.5 litres (1.2 US gallons) of sperm.

Female right whales have been observed to engage in simultaneous copulations with males. This, along with the size of the male's testes, have led scientists to speculate that sperm competition is a factor in the whales' mating strategy.