Prying yourself out of bed on a frigid winter morning can be an excruciating chore.

For a Big Brown Bat, it can be downright deadly.

“They were literally dropping and dying,” said Nathalie Karvonen, the executive director of the Toronto Wildlife Centre.

The centre’s workers are nursing about 50 bats back to health after rescuing them from the biting cold.

The bats were found outside Thursday in -19C temperatures near the Tannery Mall in Newmarket after they were rudely awakened from hibernation.

“Clearly something happened that somehow displaced them from where they were hibernating,” Karvonen said. “There’s absolutely no way they would have chosen to spend the winter in the exposed outdoor spot where they were.”

Six of the bats froze to death before rescue staff arrived.

Despite their name, Big Brown Bats aren’t all that big — each bat only weighs about 15 grams.

“You can imagine being a little fragile 15-gram animal in this freezing temperature — you don’t have much protection,” Karvonen said.

A single bat fits easily in the palm of Lisa Fosco’s gloved hand.

Fosco, the centre’s wildlife rehabilitation manager, carefully holds the bat in a tea towel. With her other hand she plucks a wriggling mealworm from a plastic container with a pair of tweezers.

She brings the mealworm to the bat’s mouth to coax it to eat, and the bat chomps down with miniature fangs.

Hand-feeding the bats is a time-consuming task. Now that they’ve woken up, the little bats are hungry — each bat can eat about 40 mealworms a day. It took more than 12 hours yesterday to feed the more than 50 bats, Karvonen said.

Big Brown Bats typically hibernate from November to March, taking shelter in a cave or attic and huddling together for warmth.

“They build up fat reserves so they’re well-hydrated when they go into hibernation,” Karvonen said.

When they are active during the summer months, a bat can eat three-times its own body weight in live insects a day.

“The bats are very important animals to the balance of ecological systems because they do eat so many insects. They help to keep mosquitoes and other insects in check,” Karvonen said.

When the animals are nursed back to health, Karvonen said they may be able to induce hibernation, a difficult job in captivity because it requires precise temperature and humidity control.

“We don’t have really the proper facilities for that. Hibernation equipment is incredibly expensive,” Karvonen said.

If hibernation is possible, the priority will be to put the female bats to sleep first. Big Brown Bats mate in the fall before they hibernate, but the female holds off the pregnancy during the winter and does not give birth until the spring.

One of the problems with the bats coming out of hibernation early, Karvonen said, is that the females may mistakenly give birth too soon, their cycles thrown off by the warmer temperatures inside the building.

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Karvonen said the wildlife centre, which runs on donations, appreciates any help it can get to care for the bats until the spring, when warmer weather will allow them to fly free. There’s a particular need for volunteers who are vaccinated against rabies, as they are the only ones who can handle the bats to feed them.

And the bats must be fed daily — Karvonen ordered 31,000 more mealworms on Friday.

“They can’t be released in the winter-time,” Karvonen said.