Why do grass snakes knot themselves up?

ASuch is the flexibility of grass (and other) snakes that they can sometimes tie themselves in knots as they settle into tight grasses or slither into narrow cracks. How intentional this behaviour is remains largely unknown. It certainly doesn’t seem to cause grass snakes any obvious problems. They usually simply pull the knot wide with their super-muscular skeleton and slide through the loop as if the knot weren’t there.

Tying itself in a knot can also be an accidental by-product of the grass snake’s famous ‘play dead’ response. When threatened by predators, these reptiles often bunch their coils and stay stock still, lolling their tongues and rolling their eyes into their skulls with theatrical aplomb. The behaviour is reasonably common in adults, but rarer in young snakes. One study found that 66 per cent of wild-caught grass snakes exhibited the death-feigning response when threatened, yet no (lab-reared) hatchlings appeared to rely on this adaptive behaviour.

By playing dead, this grass snake may dissuade predators – including badgers, foxes, hedgehogs and domestic cats – from tucking in.