The testicles of the blue whale are over 70 cm long and weigh about 50 kg. Testicle dimensions in whales vary greatly, as they do in man. Yet the sperm cells of this whale are no larger than human sperm cells. Human testicles have a combined weight of approximately 40 g, corresponding to roughly 0.06 per cent of total body weight. The testicles of a stallion weigh almost 350 g, or 0.27 per cent of its total body weight.
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Chimpanzees have the heaviest testicles of all anthropoid apes, with a combined weight of 119 g (0.27% of body weight), while a gorilla’s testicles are much smaller, in both relative and absolute terms (29.6 g, 0.02%). The human male is therefore somewhere in the middle.
There is very special sub-group among fighting cocks: they have especially large testicles, and are both ‘transvestites’ and ‘homosexual’. This type of male was discovered some years ago by a Frisian potato farmer and bird expert, Joop Jukema. The unusual creature turned out to be hard to distinguish from a female with the naked eye and displayed homosexual behaviour. The discovery was a bombshell for the biological community. The farmer christened his discovery faar, which in Frisian means patriarch. Only 1 per cent of the breed are patriarchs. It had been discovered fifty years previously that there are different types of fighting cock males: ‘basemen’, which defend a small territory against others like themselves, and ‘satellites’. The latter forage about and are tolerated by the basemen. At the time this discovery caused a sensation, but finding a third type half a century later was extraordinary.
According to the potato farmer the faar was discovered so late because its appearance meant that it was mistaken for a female. Females are brown, while males have strikingly coloured neck feathers to impress females, and in addition the male is considerably larger than the female. The discoverer began to doubt the received wisdom when he occasionally spotted a bird that departed from the norm: a fighting cock without spectacular neck feathers, but with the dimensions of a male. As regards colour it was a female, but the wings were over 17 cm long, which was very unusual for a female. Internal examination
showed it to be a male, with particularly large testicles. Of course the farmer called in back-up, from scientists at Groningen University. There was great curiosity about the faar’s reproductive behaviour: it was found to have a preference for mating with its own sex.
The researchers assumed that the faars ‘leave their sperm behind’ in basemen, which then transfer it to a female. Thanks to their large testicles they can easily swamp sperm from other males with their abundant production. Normally they have little chance of mating with a female, because females are closely guarded by other males. These homosexual ‘transvestites’ are not inclined to compete openly, and yet have found a way of reproducing!
A comparable situation exists with lizards of the genus anolis. Some males remain as small as females and hence are not regarded as rivals by other males. They are able to move about the territory of larger male lizards unnoticed and mate with females. They must, though, keep a low profile, or they run the risk of unwanted homosexual contact.