Grizzly bear 663 was only captured, handled and collared once during her lifetime; trapped on October 2, 2010 at Jasper Creek in Yellowstone National Park. At the time of her first and only capture, she was 6 years old, weighing 206 lbs. and not accompanied by any cubs at that time. The Interagency Grizzly Bear Study Team fitted 663 with a radio collar. In 2011, during aerial flights and visual observations, no cubs were observed. During 2012, she was observed with 2 cubs-of-the-year (COY) during May, but no cubs were observed during the month of June; presumably, both cubs perished but the cause of mortality is unknown. In 2013, 663 cast her collar. Observations during 2013 concluded that 663 did not have cubs. During 2014, 663 was observed with two cubs-of-the-year; later in the summer, she was observed with only one. The following year 2015, she was observed with no cubs, suggesting that her lone remaining cub perished some point during 2014. As of 2020, grizzly 663 is 16 years old.
Figure(s): Four maps depicting varying spatial components pertaining to grizzly 663 from 2016-2018. During this three-year period, citizen scientists and park personnel observed 663 for 180+ credible and verified observations. (A) Displays observations by month, and outlines 50% and 95% observational home ranges (OHR). (B) Displays Kernel Density Estimation (KDE) while outlining 50% and 95% OHR. (C) Displays habitat and vegetation type located inside of the 50% and 95% OHR, which is predominantly big sagebrush, Idaho fescue with inter-mixed subalpine fir. (D) Displays movement tracks calculated by linking subsequent sightings based on date and time.
Since 2016, grizzly 663 has exhibited seasonally 'predictable' movements. The road which runs from Mammoth to Cooke City fragments her observational home range. From 2016-2018, grizzly 663 completed one full reproductive cycle. During this period of time, we estimate her 95% observational home range at roughly 40 km2; her 50% observational home range sits at roughly 28 km2. While grizzly 663 has a range that is noticeably smaller than the documented average by the Interagency Grizzly Bear Study team, it could be for several reasons. In areas of high density or similar necessity for nutritional resources, ranges exhibited by female grizzlies are much smaller as opposed to those home ranges documented in low-density areas. This change is likely due to competition for space, and areas of frequent foraging; also the avoidance of dominant male grizzlies (Blanchard & Knight 1991, Dahle & Swenson 2003, Schwartz et al. 2003, Dahle et al. 2006, Edwards et al. 2013, Bjornlie et al. 2014).
Grizzly 663 is just one of nearly half-a-dozen females within the Lamar Valley area that exhibit an observational home range less than 100 km2 over a three year period. In the case of Lamar Valley, given the number of observations and the number of unique individual bears surveyed in one day (n = 31), we speculate that the density is a driving factor for smaller home ranges for females with cubs in this region of Yellowstone, and could vary seasonally.
"Not all who wander are lost": Movements and ranges of grizzlies in the Greater Yellowstone & The story of Grizzly 480
Grizzly 480 was born sometime around 1996, somewhere in the confines of Yellowstone National Park. The Interagency Grizzly Bear Study Team (IGBST) first captured grizzly 480 at Cascade Creek, YNP, on October 8, 2004. His capture was part of the annual research and monitoring initiative set forth by the IGBST. During this initial capture, he was first marked and radio-collared. Two-days post initial capture grizzly 480 found himself back into the same trap; he was released on-site and not handled. Just short of one-year, on September 25, 2005, grizzly 480 was captured at Antelope Creek, YNP. The following year during 2006, grizzly 480 ‘shucked’ his collar (dropped).
There was a hiatus in monitoring for grizzly 480; nearly 13-years elapsed until grizzly 480 made contact with IGBST researchers. On September 20, 2018, grizzly 480 was captured at Antelope Creek, YNP. During his handling, they collared him for research monitoring. Two weeks later, researchers captured grizzly 480 at Cascade Creek, YNP. Between his first and second captures in 2018, he cast his collar. At the time of the second subsequent capture, he was released and not handled (Haroldson et al. 2005, 2006, 2007, 2018)
Grizzly 480 displays traditional movements for a male grizzly bear in the Greater Yellowstone Ecosystem (GYE). Unlike females and females with cubs, males have much larger home ranges. Also, males do not display a high level of fidelity to their home ranges as females exhibit. Home range size is a function of resource availability; as sizes of home ranges decrease, habitat quality increases (Steiniger et al. 2010). A home range is defined as the “area traversed by the individual in its normal activities of food gathering, mating, and caring for young” (Burt, 1943). Home ranges are incredibly variable based on sex, age, and demographic groups. Several factors should be considered with the construction of home ranges for grizzly bears (Munro et al. 2006, Ross 2002, McLellan 1989).
1. Grizzlies are omnivorous and eat primarily vegetation.
2. Often, they will roam widely in search of berries and food sources during late summer and autumn (dispersal, and motivated by food)
3. They are not territorial (their home ranges do overlap!)
4. Adult and subadult males will have home ranges known to be several times larger than that of females
5. Home range is directly impacted by population density
6. Bears may move hundreds of kilometers during dispersal.
7. Grizzlies are known to avoid some environments such as high elevations with rocks, snow, mainly because of limited food; however, that does not exclude them crossing such an environment.
8. Grizzlies are slow to mature and reproduce (one of the slowest reproductive rates amongst all terrestrial mammals)
As mentioned, population density can greatly influence grizzly movements. In areas of high density or similar necessity for nutritional resources, ranges exhibited by female grizzlies are much smaller as opposed to those home ranges documented in low-density areas. This change is likely due to competition for space, and areas of frequent foraging; also the avoidance of dominant male grizzlies (Blanchard & Knight 1991, Dahle & Swenson 2003, Schwartz et al. 2003, Dahle et al. 2006, Edwards et al. 2013, Bjornlie et al. 2014). Patterns of movement are generally food driven; early spring, when bears first emerge from their dens, they will move to lower elevations in valley regions, where there is likely absence of snow, in efforts to find new green vegetation. Females with cubs-of-the-year (COY), however, will likely remain at higher, less preferred areas close to the den, due to the need for security of their cubs during a time of lacking mobility. As spring progresses, movements increase, and this stays true until the fall for most bears.
In the case of grizzly 480, an adult male grizzly bear, their movements generally peak during May & June. Daily activity and movement levels for both male and female grizzly bears typically peak during dawn or dusk, which we refer to as a “crepuscular activity pattern.”
Despite significant changes in distribution, and the availability of specific food resources and habitat, lifetime home ranges did not change for male or female grizzly bears and remained consistent between 1975-1993 in comparison to 1994-2012.
Tyler Brasington is a native born and raised Pennsylvanian, yet proud current Wisconsin resident. He graduated from the University of Wisconsin-Whitewater with a B.S. in Environmental Science. Currently, Tyler is pursuing his masters in Natural Resources with the University of Wisconsin-Stevens Point. He has worked in Yellowstone National Park under the guidance and supervision of Dr. George Clokey and Dr. Jim Halfpenny.
Disclaimer: The information and views expressed on this page do not necessarily represent the views of the Department of Interior, US Geological Survey, National Park Service or the United States Government.
The Greater Yellowstone Grizzly Project
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