If you are bear hunting from late May into June, your hunt will be influenced by the bear rut. Knowing all you can about it will make you a better hunter. In a research paper written by Kim Barber and Fredrick Lindzey in Washington State, they noted that female bears range from 6 to 16 days in estrous each spring with the average being 9.25 days. The length of estrous often depends on how quickly the sow is bred. During the research period, male bears were with females from 2 to 5 days, indicating that this was when they actually bred. It’s important to note that this data was collected by radio-collared black bears. Black bears are “promiscuous” breeders, meaning they can have multiple partners. Biologists once observed a female grizzly bear breed 10 times with 4 different males in a two-hour period.

During Barber and Lindzey’s research, they first observed males in the presence of females in between May 10th and May 21st.  These are important dates for bear hunters. This would be considered the first early stages of the bear rut. The last associations between males and females were around July 4th. This would indicate the end of bear breeding. If we can draw conclusions about bear rut from their research, the bear rut is about a 50-54 day cycle starting in mid-May and running through early June. Most of the time the male and female bears were in each other’s presence for 2 to 5 day intervals. A receptive female would usually have more than one male in her presence. The most interesting find of their study was that the peak breeding period was between June 11 and June 30. This is also an important date to remember. However, the peak breeding isn’t necessarily going to be the best hunting – though it very well may be. 

Barber and Lindzey found that there were “short term associations” between boars and females starting in mid May. This indicated that the boars were checking the sows for estrous, but moving on when they determined they weren’t receptive. However, the “long term associations” lasting between 2 to 5 days indicated the actual breeding period, which on average took place between June 11 and June 30. However, the first sows in their study were bred on May 21st. During a sow’s actual breeding period, multiple males visited the sow. Cubs in the same litter could have different fathers. It was noted, “each female had multiple opportunities to breed with more than one male.” The researchers noted that the dominance among males was determined before the actual breeding period, not during the breeding period. In this stable population, the boars weren’t fighting during the breeding period, but rather dominance had been established prior. However, in a hunted population where dominant males are being killed, dominance is less predicable and males are more likely to actively compete for females. The females also played a role in breeding by staying close to the dominant male during her estrous, not just the male staying with the female.

Male bears dramatically extended their home ranges during this 50 to 54 day period. This is perhaps the biggest take away for spring bear hunting. The big boars are on the move looking for receptive sows. Whenever one comes into estrous, she’ll attract multiple males and wherever she is will be the hotspot. When hunting over bait during this time, the males may not lock down on a site attracted by the food, but they’ll be less predictable. However, anything could show up at any time, especially if you’ve got sows without cubs coming into the bait. It’s important to note that boars are primarily interested in sows without cubs. Keep all this in mind for some great discussion at bear camp this spring. You might find you know more about the bear rut than anybody else around the campfire.