BioMed Central Blog

Long-term monitoring in wild black bears

Wild black bears are remarkable animals. They can spend half their lives in a state of hibernation without access to food or water and yet are still able to rouse and defend themselves if disturbed. In an article published in BMC Physiology, Paul Iaizzo and colleagues have, for the first time, provided a fascinating new insight into how the bears do this.

By monitoring bears in the wild for a year (using insertable cardiac monitors originally developed for use on humans)  it’s become apparent that the variations in physiological states between hibernation and waking are immense. Daytime activity ranges from little or nothing in the Winter to c. 18 hours in Summer with heart rates fluctuating between 7-8 and 250 beats per minute.

During hibernation, which may last for up to six months every year, the heart rate of the black bear accounts for only 24% of the entire annual heartbeats, and breathing rates drop as low as 1 breath every 40 seconds. However, if alerted to potential danger, the bears are able revert to a “normal” state within seconds and undergo bursts of activity.

At the beginning of Winter pregnant bears are in deep hibernation, but their heart rate increases as their  pregnancy progresses, spiking during birth. After delivery the mothers heart rate returns to a hibernation state and for several weeks post delivery she exhibits much less movement, thought to prevent accidental damage to the suckling cubs.

One of the most unusual aspects of bear hibernation is that despite starvation and inactivity they exhibit very limited muscle wastage and loss of strength. This characteristic especially intrigues scientists who are looking for ways to transport humans vast distances, such as those encountered in space travel.

Photos courtesy of Paul Iaizzo, Dave Garshelis and Tim Laske.

Posted by Georgina Giddens at 14:55    Comments (0)