How do you get sperm from a crocodile ? “Very carefully is the short answer,” says Brett Nixon, a professor at the University of Newcastle, who has studied the sperm of animals including platypus, rabbits and the saltwater predators to better understand human reproduction. (The long answer is that you sedate the croc and extract sperm using a method euphemistically dubbed a “digital massage”.)

A new study has found reduced sperm production and testosterone in mice exposed to forever chemicals. Credit: University of Newcastle

It turns out, compared with animals, humans are not good at making sperm. Rams ejaculate about 100 billion sperm compared with a man’s measly 100 million. The humble fruit fly unleashes monster sperm that’s six centimetres long – about 20 times its body length.

See Full Page