Saturday, July 31, 2010

Black Bear Mating Season

Black Bears in Virginia mate between June and July. Females typically do not breed until they are 3 years old. Once females come into season, they usually leave scent trails, and male bears (boars) quickly hone in on the scent. More than one male may catch the female's scent and this can lead to some potentially violent showdowns between competing males. Adult males are definitely a 'beast of a different nature' and are solitary creatures during the non-breeding season. However, during the breeding season they are more visible, and you should use caution while in the vicinity of a boar during this time of year as they are far more aggitated.

LOVE IS IN THE AIR! A Sow (left) and Boar(right)

Both males and females increase their movements during mating season, and both leave scent marks on trees and in vegetation. Females continue to forage during this time and generally can maintain their weight. However, males forage very little during mating season and lose approximately 20% of their fall weight during the 7-8 weeks of mating season. Males travel extensively in search of females and can have mating ranges 10-15 miles in diameter.

Large males chase younger males away, but mature, evenly-matched, males fight for dominance and mating rights. Old males carry numerous scars on their heads and necks from mating battles (as the one shown in the photos above).

Males follow females to assess their receptiveness, regularly sniffing areas where the female has sat and the female herself when possible. Couples often play and rest together during courtship. Males may follow individual females and guard them against rivals for up to 9 days before the female becomes receptive and mating occurs. A pair will mate repeatedly over several days. Both male and female black bears commonly have more than one mate and the most active mating occurs in July.

After mating, the female may be pregnant, but that does not mean she will give birth to cubs. Bears, weasels and some seals have developed a process called delayed implantation. The fertilized egg develops into a small embryo called a blastocyst. This is where the interesting stuff begins. After this brief period of development, the fertilized egg suddenly stops growing and simply floats freely in the uterus for several months (i.e. Delayed Implantation).

If female bears do not attain sufficient body fat or weight, their embryos will not develop. If a sow is in peak condition when she heads into her winter den, the embryo implants in the uterus and begins to develop. She'll wake up during January or February to give birth. Black bears give birth to between one and four cubs, with two being the most common.

If the sow is not in peak condition at the onset of hibernation, her body will re-absorb the embryo and not give birth that year. This gives bears more control over their reproductive rate than just about any other animal. Once a deer is pregnant, they are pregnant, and winter pregnancy can be fatal. Animals diverting energy to reproduction during the difficult winter months run the risk of falling victim to predation.

A short low-quality clip of 2 bears mating back in 2008. This was captured with a point-and-shoot camera's video recorder.
Each Summer I hope to get another chance at videotaping bears while mating but so far it has eluded me.

The Black Bear population does not have the ability to increase rapidly. Bears are among least productive mammals. In theory, a male and female black bear born this year - if they breed as soon as they reach sexual maturity and as often as possible, and if their offspring did the same - could in the space of ten years have grown to a population of 15 bears, assuming none died. By comparison, a pair of whitetailed deer could produce more than 1,000 descendants in 10 years!

For more Black Bear photos, information and video clips, visit the black bears section of my Web site.