Hedgehogs: 12 things that may surprise you about Britain’s favourite mammal
What are hedgehogs? How can we help ensure their survival? And what on earth is a hedgehog carousel?!
For The Infinite Monkey Cage, Brian Cox and Robin Ince forage into the prickly lives of Britain’s favourite mammal. With special guests including poet Pam Ayres, they snuffle their way through the evolution of hedgehogs, their life cycle and how to stop them getting run over by robotic lawn mowers!
Here are 12 things you may not know about the spiny species.
The Infinite Monkey Cage
1. Hedgehogs don't have a flight or fight response
“This is one of the few animal species that you can actually get really close to,” says Sophie Lund Rasmussen (aka Dr Hedgehog). “Their strategy when faced with danger, or a human staring at them, is to stand completely still, and then decide whether to curl up or run away.”
2. They frown before they curl into a ball
“When a hedgehog is first nervous it frowns and it brings the spines forward over its eyes and its nose,” says Hugh Warwick, from the British Hedgehog Preservation Society. “Don’t give hedgehogs Botox,” he jokes, “because it really interferes with their ability to defend themselves!”
3. They are born with their spines
Hedgehogs are born with their spines under a layer of fluid-filled skin. The fluid is then absorbed and the spines appear. “If you had hedgehogs born totally without spines, they’d be defenceless,” says Hugh.
Unfortunately, as a defence strategy, spines are not what they used to be. A hedgehog’s natural predators will detect movement in the dark, so the tactic of staying still and curling up is very effective – but it’s not adapted to modern living, says Sophie: “If you do that in front of a car coming your way, it’s really not the best solution.”
4. They’re not related to porcupines
The hedgehog belongs to the order Eulipotyphla, which basically means “truly blind and fat,” explains Sophie. The family Erinaceidae consists of hedgehogs and moonrats (the hairy hedgehogs). Interestingly, we have a lot of species that have developed spines, like the porcupine, but they’re not related to hedgehogs.
5. Hedgehogs are promiscuous
After mating, the male hedgehog doesn’t stick around. “The females are left with all the work,” says Sophie, “bringing up the hoglets.”
A female usually gives birth to around four or five hoglets at a time and, because hedgehogs are generally very promiscuous, each litter may have several different fathers.
6. You can work out the age of a hedgehog from its jawbone
“You can tell the age of a hedgehog by counting growth rings in their jawbones, like you would do on trees,” explains Sophie Lund Rasmussen. The Danish researcher examined the jawbones of 400 dead hedgehogs and counted up to 16 years of growth rings in some. (Although the average was around two years of age.)
7. Hedgehogs have been (wrongly) accused of causing crop circles
When a female hedgehog comes into season and attracts a mate, the male will start circling her. This goes on and on, resulting in a little circle of compressed vegetation known as a “hedgehog carousel.” This led to the suggestion that crop circles were caused by hedgehogs – a theory soon debunked when it was calculated it would require 40,000 hedgehogs working in synchrony to make even one modest crop circle!
8. Hedgehogs can sprint
Hedgehogs can be pretty speedy when they want to be. They actually have very long legs, and “can run really fast”, says Sophie.
Broadcaster and poet Pam Ayres says it’s astonishing to witness: “You see them and they’re like a little mound and then when they decide to run, they lift up and these great long legs are suddenly apparent and they sprint off and it’s a great surprise how speedy they are.”
9. They are ferocious predators
Hedgehogs primarily eat macro invertebrates (the bigger bugs and insects), but if you analyse their faeces, you’ll see they eat “all sorts of things,” says Hugh Warwick. “I’ve collected stories of hedgehogs noshing on carrion, grabbing hold of a mouse which was injured, and trying to eat a chicken.”
“People consider hedgehogs really cute but they are actually also ferocious predators,” says Sophie. “I’ve seen recordings of a hedgehog taking on an adult pigeon and a blackbird and winning actually, and eating the bird.”
10. Hedgehogs self-anoint
Whenever a hedgehog comes across a pungent smell, like faeces, they’ll chew on the source of the odour, and then spread the sticky saliva over their spines. We assume that it’s to mask their own smell from predators, says Sophie: “A sense of extra perfume, you could say.”
11. They can roam big distances at night
“They can move over 2km a night, quite easily,” says Hugh. “They’ll travel great distances.” Unfortunately, this isn’t always easy in built-up, suburban areas.
“If you want a viable population of hedgehogs, you need a garden of about a square kilometre.” Most of us don’t have that, but we can help by putting 13cm holes in the bottom of our garden fences and walls to make “hedgehog streets”, so the animals can roam and extend the gene pool.
12. They are at risk from robotic lawnmowers
Humans are the greatest threat to the hedgehog. “They get tangled up in football nets,” says Pam Ayres. “They can just get trapped and die.” The same goes for the fine netting used in gardens. “It’s a question of lifting that stuff up away from the ground where they can get tangled up in it.”
Sophie’s research also shows that some robotic lawnmowers can hurt and kill hedgehogs. So she advises not leaving them running at night when the animals are active.
And, as well as putting holes in fences and rewilding areas to encourage insects, we can leave fresh water out in our gardens for hedgehogs to drink. “It’s a simple thing but it’s really important,” says Pam.
