Let sleeping bears lie: Even when hibernating, they are primed to fend off a sudden attack

By Richard Hartley-parkinson


Do not disturb: Black bears can wake up very quickly from hibernation to defend themselves if they believe they are about to be attacked - a skill that is necessary as they cannot burrow below ground for protection


The old saying 'let sleeping dogs lie' can be applied to hibernating black bears according to a study which found their heart rates increase whenever intruders gets too close.

Even though they appear as though they are fast asleep they can tell when someone, or something, is near them.

Despite attempts to be as quiet as possible, scientists discovered that American black bears react as though they are preparing for a sudden attack on them in their winter dens.


They can wake up very quickly from hibernation to defend themselves if they believe they are about to be attacked - a skill that is necessary as they cannot burrow below ground for protection.

Timothy Laske of Medtronic, a medical technology company in Minneapolis, said: 'When we retrieved our data, even though we tried to be as quiet as posible, the bears' heart rates increased before we reached the entrance to their winter den and remained elevated for a number of days.

'This confirms that despite apparent deep sleep, bears are always alert to danger and ready to act... Black bears often make their way into sub-urban areas which can be dangerous and stressful for both bears and humans,' he told the Independent newspaper.

'Understanding the silent effect of humans and the environment on bears will also allow better bear management.'

The hearts of 15 wild bears were monitored by scientists who took daily readings of their cardiac rhythms and they showed that bears are active for up to 18 hours a day.

Even though they appear as though they are fast asleep black bears can tell when someone, or something, is near them


On average they beat 200 times a minute, rising to 250 when humans were present.

For half the year, however, they are asleep and don't eat or drink, or urinate or defecate, and during this time their heart rate falls to as low as 14 beats a minute.

Despite the period of inactivity - when breaths happen twice a minute, lasting 14 seconds - they lose little of their muscles and their core body temperature does not fall as low as that of smaller animals that hibernate.

In black bears the body temperature is more likely to be a few degrees below 36C compared with near-freezing temperatures of other creatures.

Their metabolic rate falls by as much as three quarters when sleeping showing that they are hibernating properly and not just in some form of prolonged sleep.



source:dailymail