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Eric Regehr

Principal Quantitative Ecologist





Department Affiliation

Polar Science Center


B.S. Chemical Engineering, University of Kansas, 1998

Ph.D. Zoology & Physiology, University of Wyoming - Laramie, 2009


2000-present and while at APL-UW

Demographic response of a high-Arctic polar bear (Ursus martitimus) subpopulation to changes in sea ice and subsistence harvest

Laidre, K.L., T.W. Arnold, E.V. Regehr, S.N. Atkinson, E.W. Born, O. Wiig, N.J. Lunn, M. Dyck, H.L. Stern, S. Stapleton, B. Cohen, and D. Paetkau, "Demographic response of a high-Arctic polar bear (Ursus martitimus) subpopulation to changes in sea ice and subsistence harvest," Endanger. Species Res., 51, 73-81, doi:10.3354/esr01239, 2023.

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25 May 2023

Climate change is a long-term threat to polar bears. However, sea-ice loss is hypothesized to provide transient benefits in high latitudes, where thick multiyear ice historically limited biological productivity and seal abundance. We used joint live-recapture and dead-recovery mark-recapture models to analyze data for one of the most northerly polar bear subpopulations, Kane Basin. The data consisted of 277 initial live captures and genetic identifications (1992–1997 = 150, 2012–-2014 = 127), 89 recaptures or re-identifications (1992–1997 = 53, 2012–2014 = 36), and 24 harvest returns of research-marked bears during 1992–2014. We estimated mean annual abundance of 357 bears (95% CI: 221–493) for 2013–2014. This suggests a likely increase relative to our estimate of 224 (95% CI: 145–303) bears in the mid-1990s and relative to a previously published estimate of 164 (95% CI: 94–234) bears in the mid-1990s that used some of the same data. This is also supported by an apparent increase in the density of bears in eastern Kane Basin during 2012–2014. Estimates of total survival for females ≥3 yr old (mean ± SE: 0.95 ± 0.04) and their dependent offspring were similar to previous estimates from the 1990s, and estimates of unharvested survival for females ≥3 yr (0.96 ± 0.04) appear sufficient for positive population growth. Estimates of total survival were lower for males ≥3 yr (0.87 ± 0.06). We documented a reduction in mortality associated with subsistence harvest, likely attributable to implementation of a harvest quota by Greenland in 2006. Our findings, together with evidence for increased range sizes, improved body condition for all sex and age classes, and stable reproductive metrics, show that this small high-Arctic polar bear subpopulation remains productive and healthy. These benefits are likely temporary given predictions for continued climate change.

Using visual observations to compare the behavior of previously immobilized and non-immobilized wild polar bears

Stirling, I., E.V. Regehr, C. Spencer, L.E. Burns, and K.L. Laidre, "Using visual observations to compare the behavior of previously immobilized and non-immobilized wild polar bears," Arctic, 75, 398-412, doi:10.14430/arctic76118, 2022.

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1 Dec 2022

During 17 field seasons between 1973 and 1999, we conducted a long-term study of the behavior of undisturbed wild polar bears in Radstock Bay, southwest Devon Island, Nunavut. In a subset of 11 seasons (6 spring and 5 summer) between 1975 and 1997, we used three different drug combinations to chemically immobilize a small number of adult and subadult polar bears on an opportunistic basis and applied a temporary dye mark so that individual bears could be visually reidentified. We then used multinomial logistic regression to compare the behavior of 35 previously immobilized bears of five different demographic classes (sex, age, and reproductive status) to the behavior of non-immobilized bears of the same demographic classes in the same years and seasons. During the first two days after immobilization, bears slept significantly more and spent less time hunting than did bears that had not been immobilized. However, previously immobilized bears returned to the same behavioral patterns and proportion of total time spent hunting as non-immobilized bears within two days and no further negative behavioral effects were detected in the following 21 d. We visually confirmed successful hunting by three adult bears within 0.4 to 2.1 d of being immobilized, all of which went on to make additional kills within the following 24 h. The return to normal behavior patterns, including the ability to hunt successfully, within 48 h of immobilization appears consistent with the hypothesis that polar bears do not experience longer-term behavioral effects following brief chemical immobilization for conservation and management purposes.

Modeling spatiotemporal abundance and movement dynamics using an integrated spatial capture–recapture movement model

Hostetter, N.J., E.V. Regehr, R.R. Wilson, J.A. Royle, and S.J. Converse, "Modeling spatiotemporal abundance and movement dynamics using an integrated spatial capture–recapture movement model," Ecology, 103,, doi:10.1002/ecy.3772, 2022.

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1 Oct 2022

Animal movement is a fundamental ecological process affecting the survival and reproduction of individuals, the structure of populations, and the dynamics of communities. Methods to quantify animal movement and spatiotemporal abundances, however, are generally separate and therefore omit linkages between individual-level and population-level processes. We describe an integrated spatial capture–recapture (SCR) movement model to jointly estimate (1) the number and distribution of individuals in a defined spatial region and (2) movement of those individuals through time. We applied our model to a study of polar bears (Ursus maritimus) in a 28,125 km2 survey area of the eastern Chukchi Sea, USA in 2015 that incorporated capture–recapture and telemetry data. In simulation studies, the model provided unbiased estimates of movement, abundance, and detection parameters using a bivariate normal random walk and correlated random walk movement process. Our case study provided detailed evidence of directional movement persistence for both male and female bears, where individuals regularly traversed areas larger than the survey area during the 36-day study period. Scaling from individual- to population-level inferences, we found that densities varied from <0.75 bears/625 km2 grid cell/day in nearshore cells to 1.6–2.5 bears/grid cell/day for cells surrounded by sea ice. Daily abundance estimates ranged from 53 to 69 bears, with no trend across days. The cumulative number of unique bears that used the survey area increased through time due to movements into and out of the area, resulting in an estimated 171 individuals using the survey area during the study (95% credible interval 124–250). Abundance estimates were similar to a previous multiyear integrated population model using capture–recapture and telemetry data (2008–2016; Regehr et al., Scientific Reports 8:16780, 2018). Overall, the SCR–movement model successfully quantified both individual- and population-level space use, including the effects of landscape characteristics on movement, abundance, and detection, while linking the movement and abundance processes to directly estimate density within a prescribed spatial region and temporal period. Integrated SCR–movement models provide a generalizable approach to incorporate greater movement realism into population dynamics and link movement to emergent properties including spatiotemporal densities and abundances.

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In The News

Polar bears of the past survived warm periods. What does that mean for the future?

Anchorage Daily News, Ned Rozell

A small population of polar bears living off Greenland and Arctic Canada increased by 1.6 times when comparing numbers from the 1990s to 2013 and 2014. Lighter sea ice might have benefited the animals because sunshine penetrates thinner ice better, which stimulates small living things. That means more food for seals, the main food of polar bears.

3 Jun 2023

UW polar bear expert appears in BBC-produced film about the Arctic

UW News, Hannah Hickey

A new production, "Arctic: Our Frozen Planet," narrated by Benedict Cumberbatch, screens May 25 and 27 at the Pacific Science Center in Seattle. Eric Regehr, a researcher at the UW Applied Physics Laboratory, appears in the film doing fieldwork on Wrangel Island, an island off the northeast coast of Russia that is home to the world’s highest concentration of polar bears.

23 May 2023

Why Russia's war in Ukraine is bad news for polar bears, too

The Washington Post, Dino Grandoni

The invasion is first and foremost a human tragedy, but it is also dire for wildlife, stalling scientific work on polar bears and other wildlife threatened with extinction. Sanctions and other policies have chilled scientific collaboration between American and Russian biologists, leading to nixed research trips, canceled conservation work, restricted funding and uncollected data related to imperiled species at risk of disappearing in the coming decades without human help.

15 Apr 2023

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