As the old joke goes: carefully! Crocodiles have terrifying predatory instincts and you only have to consider the risks taken by a courting male black widow spider to see how predatory instincts can ruin a beautiful moment.
Crocodiles and their close relatives, the alligators, caimans and gharials (collectively known as crocodilians), are large, lurking, muscular reptiles with sharp teeth, bone-crushing bites and an inclination towards grumpy solitude. Come the breeding season, though, they are more sociable.
Much of crocodilian communication is conducted via sound and they are among the most vocal of all reptiles. They bellow, grunt, growl, hiss and slap the water with heads and tails. American alligators produce an inaudible (to human ears) low-pitched rumble that vibrates the water around them so vigorously that droplets are thrown up into the air. Male gharials have distinctive swellings (called ghara) on the ends of their snouts that amplify the hisses and hornlike sounds issued through their nostrils.
These sounds are broadcast to repel rivals from breeding territories and to attract the attention of mates. Ingenious experiments on Chinese alligators, using helium gas to change the pitch of their vocalisations, have shown that they bellow at a frequency that resonates with their body size. This suggests that the vocalisations provide potential mates and rivals with clues about the size and strength of the bellower.
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How do crocodiles mate?
Females come and go between male territories and a few dominant males get the lion’s share of the attention. Crocodilian courtship can be surprisingly tender, involving much touching of snouts, rubbing of necks, blowing of bubbles and resting of heads on each other’s backs. In American alligators, courtship is a communal affair, involving large groups of males and females bellowing in chorus. They can be induced to bellow by a low B-flat played on a tuba. In Australia, low-flying helicopters seem to have a similar effect on saltwater crocodiles.
The act of mating itself is fairly straightforward and usually takes place in the water. A female signals she is receptive by assuming a submissive head-up posture and the male mounts her from above, twisting his tail and hind-quarters underneath her so that their genitals are in contact. Like most reptiles, but unlike most amphibians and birds, males are equipped with an erectile penis that delivers sperm close to the site of fertilisation within the female’s reproductive tract.
Intriguingly, some females are able to reproduce without mating at all - a process called parthenogenesis (virgin births). In 2018 an 18-year-old female American crocodile in a Costa Rican zoo laid a clutch of 14 eggs, at least seven of which were fertile, despite having been housed separately from other crocodiles for her entire life.
Main image: Getty
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