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Q and A: Yellowstone Grizzlies

2/4/2018

Photo credit: Jim Peaco

A few weeks ago, I posted asking visitors, and enthusiasts if they had questions about Yellowstone grizzly bears. These were some of the questions folks had; I tried to answer questions to the best of my abilities based upon current science. Some questions may have been more policy related (away from ecology and biology), and opinion based. In these instances, I tactfully attempted to answer the questions with the best interest for the species in mind.

Q: How often do grizzlies leave their den in the winter (if at all) ? I’ve heard several different answers to that question
A: There isn't really a straight forward answer for how often or how many times bears will leave their dens during winter/hibernation. However, there are reasons why they may leave their dens. There have been instances of black bears/grizzlies emerging, wandering a bit and then returning to their den (they do not stray to far). However, there may be a wide range of reasons for premature emergence. Sometimes this can be attributed to human disturbance (recreational activity, skiing, snowmobiling, etc.). Other times, it could be because of favorable conditions not requiring a bear to remain in hibernation. In Florida, male black bears have a much more condensed denning period, some not even hibernating or denning at all! Food availability affects when bears enter, and when bears emerge from hibernation as well. (Cited: Haroldson, M. A., Ternent, M. A., Gunther, K. A., & Schwartz, C. C. (2002). Grizzly bear denning chronology and movements in the Greater Yellowstone Ecosystem. Ursus, 29-37.)

Q: How many grizzly bears are in Yellowstone?
A: Just in Yellowstone alone, there is an estimate 150 grizzlies. This is a conservative estimate. In the Greater Yellowstone Ecosystem, as of 2016, approximately 690 grizzlies.

Q: Tyler, the white bark pine nuts seem to be an inconsistent source of food for the bears, What determines a good year for the crop versus a bad year?
A: They are inconsistent as a food source. The inconsistency in their availability can cause several things to happen. First off, let me address what determines a good year from a poor year. Ultimately, the number of pine cones produced; the number of healthy and pinecone producing trees. This is largely affected by the mountain pine beetle infestation. Pine beetles are native to the Rocky Mountains. However, because of continued climatic imbalances, warmer weather and less harsh winters at higher altitudes has allowed these beetles to infest even the highest standing groves of whitebark pine. This isn't good news for bears, but also isn't good news for clark's nutcracker, and pocket gophers. The pinecone itself contains pine nuts, which are high in fat. When in heavy abundance, these are a great food source for grizzlies. Moreover, there should not be an extreme worry about a shift away from whitebark pine. Grizzlies are omnivore generalists and have dietary plasticity (opportunistic). Typically, years where the whitebark pine have good seed crops, grizzlies (male and females) will be found at higher elevations (whitebark are high elevation trees). When whitebark pine crops fail, grizzlies tend to forage on root crops at lower elevations, also in search of ungulates (this brings them closer to people and roadways anecdotally). It has been observed that grizzly mortality is higher during years of poor whitebark pine production and availability. Changes in food abundance or sources is not an indicator to predict survivability or survival rates, unless the bears move to an area of larger human disturbance. Though, just because bears move to lower elevations doesn't mean they will suffer increased mortality; it is when bears shift to lower elevations and areas that have been altered by humans that creates more risk for them. Bears that shift to lower elevations in secure habitat (home range) are obviously not exposed to the same risk. (Cited: Schwartz, C. C., Haroldson, M. A., & White, G. C. (2010). Hazards affecting grizzly bear survival in the Greater Yellowstone Ecosystem. Journal of Wildlife Management, 74(4), 654-667. Cited: Logan, J. A., Macfarlane, W. W., & Willcox, L. (2010). Whitebark pine vulnerability to climate‐driven mountain pine beetle disturbance in the Greater Yellowstone Ecosystem. Ecological Applications, 20(4), 895-902.)

Q: Just one question, are they protected from hunters?
A: In the National Parks, yes. Currently, management has been turned over to the states since grizzlies have been delisted. There is no active hunting season for grizzlies in the states of Wyoming, Montana, and Idaho currently. That will most likely change in the future.

Q: Okay, I have been reading that there are quite a few male bears, black and grizzlies still roaming, not in a den. Why do you think that is?
A: Based on denning chronology, male grizzlies typically enter their dens later, and emerge earlier than other demographics in their population (females with cubs, solo females). Less than 10% (cumulative) of males in the grizzly population emerge from their den between the 4th week of January and the 1st week of February. Typically, bears will emerge from hibernation when food becomes available (mid March for males is typical). However, there can be a wide range of reasons for premature emergence. This can sometimes be attributed to human disturbance (recreational activity, skiing, snowmobiling, etc.). Other times, it could be because of favorable conditions not requiring a bear to remain in hibernation. In Florida, male black bears have a seriously shorter denning time as compared to northern black bears (this is if they den at all! (Cited: Haroldson, M. A., Ternent, M. A., Gunther, K. A., & Schwartz, C. C. (2002). Grizzly bear denning chronology and movements in the Greater Yellowstone Ecosystem. Ursus, 29-37.)

Q: Since the closing of the dumps in the 70's and over time the grizzly became once again to fear human contact, and not associate people with food, do you feel that today's grizzly in the park have become re-conditioned to humans and food, and if so, what can be done to correct the problem without de-listing them and making them fear hunters again? I ask because I feel strongly that 150 in the park today is a terrifying low number, and unacceptable if they het delisted.
A: So to answer your first question: Grizzlies do not become conditioned to people. I think you have the terms "conditioned" and "habituation" maybe confused. There are some individual bears that have a higher tolerance for dealing with people, tourists, and wildlife managers. This we would call being habituated to human presence. Is this a huge issue? I personally do not see this as an enormous issue. Food conditioned bears: I feel the park service and the forest service have done a fantastic job educating people about food storage and taking precautions to ensure bears do not obtain human food rewards. Your question pertaining to delisting; the purpose of the endangered species act is to recover populations and restore them to a standard they are able to be "delisted." If we were to keep species listed forever, the act would lose purpose. Keeping species protected longer unnecessarily causes the act to lose its teeth. It is easier to delist, then relist - rather than to keep animals listed unnecessarily. 150 bears is an extremely conservative estimate for Yellowstone alone, as is 690 for the entire ecosystem. There could be as many as 300 grizzlies in Yellowstone, and maybe even 1000 in the ecosystem. It depends which numbers you look at. It is a reasonable concern about hunting; some bears are so habituated they would become easy targets for hunters. In this scenario, some wildlife managers, biologists and others have suggested a buffer zone around the park; this would be an area that would be off limits to hunting.

Q: Tyler I grew up in the Yellowstone area and have always wondered why we can’t get a solid count on the number of Grizzlies in the ecosystem. Is there anything new to assist in determining the population? And have the Grizzlies moved into the Snake River range?
A: Large mammals, especially carnivores, given any environment (Yellowstone) are extremely hard to count. You will never account for 100% of the population. Statistical methods are often applied to help wildlife managers and researchers estimate population . With grizzly bears, monitoring unique females with cubs-of-the-year yearly help us gather useful information to gauge population (stats can also help account for bear families not observed). I would get into the specifics of this, but it can be confusing and hard to understand. Currently the Interagency Grizzly Bear Study Team (IGBST) uses Chao 2, mark recapture, to estimate the population. To my knowledge, no grizzly families were identified in the Snake River Range area during 2016 or 2017. However, that is not to dismiss the possibility that grizzlies could be in that area. Male bears have much larger home ranges than females, so the possibility could exist. Maybe a transient bear. You just never know! It is a lot of area for people to cover and examine. (https://www.usgs.gov/science/interagency-grizzly-bear-study-team?qt-science_center_objects=0#qt-science_center_objects) (Cited: Long, R. A., MacKay, P., Ray, J., & Zielinski, W. (Eds.). (2012). Noninvasive survey methods for carnivores. Island Press.)

If you have any further questions, please feel free to comment below, or send a message using the "contact tab" on the upper bar of the website page. Thank you!

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Q and A: Yellowstone Grizzlies

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