Spring Awakening Bears emerge to forage intensely - lethargy is a myth

Spring Awakening: Bears emerge to forage intensely – “lethargy” is a myth

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Spring brings the first breath of warmth into the woods and the promise of a great reawakening for wildlife.  As winter’s cold grip loosens and the snow begins to melt,  the first to stir in the secluded dens of the forest are the mature male black bears or boars (Washington Department of Fish and Wildlife. 2022). To humans, bear hibernation has the connotation of sleep, sleepiness, and lethargy.  This anthropomorphic interpretation is being used as a rationale for the proposed removal and banning of bear hunting in the Spring. So it deserves exploring more – are spring bears truly lethargic?

As a point of clarification, the cartoonish anthropomorphizing of hibernation has no basis in fact or science.  Black bears fast during hibernation.  They accumulate a large mass reserve before the winter and fast while denned during the winter, which minimizes activity, mass and energy loss, and protein catabolism (Robbins, 2012). Their metabolic rate is cut nearly in half and their heart rate slows to as low as eight beats per minute (Rogers 1987).

Hibernation is truly incredible as fat stores are metabolized to provide energy and maintain body temperature, while muscle and other tissues are largely preserved. This adaptation helps ensure that, despite not eating or drinking for months, bears lose minimal muscle mass (Bowersock 2021).  In fact, and perhaps more surprising, is that hibernating black bears are always alert to danger and ready to act (BioMed Central Limited 2011).  

blood origins spring bears being lethargic is a myth

Black bears emerge to forage intensely

After months of hibernation, the boars emerge cautiously into the spring daylight.  Their first priority is simple but vital: replenishing their energy reserves. Black bears lose 16-37% of their body weight during hibernation (DelGuidice, 1991), and boars will spend their initial days foraging (Robbins, 2012).  This weight loss is entirely fat rather than muscle, and upon emergence, black bears travel to and focus on high-quality forage in the spring to better maintain body mass after emerging from hibernation while opportunistically preying on available animals like elk calves encountered while foraging for plants. (Bowersock 2021).  

Their metabolic switch is flicked back “on” upon emergence from their dens, and it’s important to emphasize the intensity of their spring travel and behavior.  Their immediate priority is to replenish the fat mass they have lost. Foraging behavior is intense, as they focus on consuming large amounts of available food sources, scouring the landscape for whatever food is available including early spring plants, leftover berries, and carrion. This is a critical period where their feeding intensity is high to rebuild energy reserves for the active months ahead​ (Robbins, 2012).

In fact, bears fitted with monitors (akin to a smartwatch) that measure physiological variables recorded the highest daytime vs. nighttime heart rate in bears consistently in the early spring months (February – April) and summer (Laske et al. 2011).  In contrast to emerging lethargic, food-motivated bears are very active. According to Laske et al., 2011 both heart rate and activity increased through the spring for at least a month following emergence from hibernation in early April. Black bears do not emerge in the spring as lethargic – far from it, as nature and necessity dictate. 

blood origins spring bears awaken for intense foraging

Black bear boars emerge with high testosterone 

In the spring, Black bears respond with gusto to another necessity – procreation.  Beginning in late spring, females lay down scent trails via urine which boars very actively follow, chasing away and fighting with vigor for their chance to spread their seed (Rogers 1999).  

In fact, in boars serum testosterone concentration was found to rise in the spring before the bears left their dens(McMillin 1976).

Once their immediate need for food is addressed, mature males shift their focus to territory and dominance. In preparation for the upcoming mating season, boars engage in solitary patrols of their ranges, marking trees with their claws and rubbing their scent glands on surfaces to signal their presence to other males. Dominance is crucial, as larger, stronger males will claim access to the most desirable territories, which are rich in food and females. As the weeks progress, these boars sharpen their focus on securing mates, all while staying vigilant for younger rivals. This early emergence grants them an edge in asserting control over their environment before females and younger males become active.

blood origins spring bears emerge from hibernation and forage intensely

“Lethargy” is an unsupported myth of black bear behavior

In our research, there is only 1 anecdote of “lethargy” in black bears, which was confined to sows and cubs during the April emergence, but not in a peer-reviewed academic paper (in a calendar,[Rogers 1989]).  Future research in a peer-reviewed journal from the same author clarified this and moved it from the realm of semantics to bear behavior, specifically for cubs following hibernation in which it was noted that some bears become active only after several minutes of prodding and handling. Even so, fewer than one percent of bears die during hibernation (Rogers 1999).

The next time you hear someone state that it’s not fair chase to hunt a bear in the Spring because it’s lethargic, now you can tell them the truth. A truth based on science and logic and not on a cartoonish anthropomorphic vestige of Black bears. Far from black bears being lethargic upon their emergence in the spring – they are truly awakened and going about the business of being black bears. 

If you doubt the science, then there is really only one other foolproof test to determine lethargy.

  1. Ask your friend who believes that they are lethargic, to go wake up a hibernating black bear. 
  2. If they say no you are crazy, ask yourself, “why are they saying no?” 
  3. Your response to that response: “You should be fine don’t worry … the bears are lethargic remember!”

References:

  1. Washington Department of Fish and Wildlife. (2022, February 23). Commission Question and Answers. Retrieved from https://wdfw.wa.gov/sites/default/files/2022-03/Commission%20Question%20Answers_Feb23_2022.pdf 
  2. DelGuidice G.D. et. al. (1991). Weights and Hematology of Wild Black Bears During Hibernation.  Journal of Wildlife Diseases, 27(4). 637-642. https://pubmed.ncbi.nlm.nih.gov/1758029/ 
  3. Robbins, C. T., Lopez-Alfaro, C., Rode, K. D., Tøien, Ø., & Nelson, O. L. (2012). Hibernation and seasonal fasting in bears: the energetic costs and consequences for polar bears. 1​ Journal of Mammalogy, 93(6), 1493-1503. https://doi.org/10.1644/11-MAMM-A-406.1 
  4. Bowersock, N. R., Litt, A. R., Merkle, J. A., Gunther, K. A., & van Manen, F. T. (2021). Responses of American black bears to spring resources. Ecosphere, 12(11), e03773. https://doi.org/10.1002/ecs2.3773 
  5. Rogers, L. L. 1987. Portrait of a black bear. Encounters 10(2):10-13. https://www.bearstudy.org/images/stories/Publications/Portrait_of_a_Black_Bear.pdf 
  6. BioMed Central Limited. “Fast asleep to wide awake: Hibernating bears, predation and pregnancy.” ScienceDaily. ScienceDaily, 25 August 2011. www.sciencedaily.com/releases/2011/08/110817022136.htm. 
  7. T. G. Laske, David L. Garshelis, Paul A. Iaizzo. Monitoring the wild black bear’s reaction to human and environmental stressors. BMC Physiology, 2011; DOI: 10.1186/1472-6793-11-13   https://bmcphysiol.biomedcentral.com/articles/10.1186/1472-6793-11-13 
  8. Rogers, L. L. 1999. Spring and the mating season. North American Bear Center Newsletter 3(2), Spring, 1999:1-2. https://www.bearstudy.org/images/stories/Publications/Spring_and_the_Mating_Season.pdf 
  9. McMillin, J. M., U. S. Seal, L. L. Rogers, and A. W. Erickson. 1976. Annual testosterone rhythm in the black bear (Ursus americanus). Biology of Reproduction 15:163-167.  https://www.bearstudy.org/images/stories/Publications/Annual_Testosterone_Rhythm_in_the_Black_Bear.pdf 
  10. Rogers, L. L. 1989. A year in the life of a black bear in northern Minnesota. Page 1 In 1990 Minnesota Weatherguide Calendar. Publ. by Science Museum of Minnesota, Freshwater Foundation, and WCCO Weather Center. Mpls., Minn. https://www.bearstudy.org/images/stories/Publications/A_year_in_the_life_of_a_black_bear_in_northern_Minnesota.pdf 
  11. Rogers, L. L. 1999. Black bear. Pages 157-160 in Don E. Wilson and Sue Ruff, eds. The Smithsonian Book of North American Mammals. Smithsonian Institution Press. Washington, D.C. https://www.bearstudy.org/images/stories/Publications/The_Smithsonian_Book_of_North_American_Mammals.pdf