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Kristin Laidre

Senior Principal Oceanographer

Professor, School of Aquatic + Fishery Sciences





Department Affiliation

Polar Science Center


B.S. Zoology, University of Washington - Seattle, 1999

Ph.D. Aquatic & Fishery Sciences, University of Washington - Seattle, 2003

Kristin Laidre's Website



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.

Light-level geolocation as a tool to monitor polar bear (Ursus maritimus) denning ecology: A case study

Merkel, B., J. Aars, K.L. Laidre, J.W. Fox, "Light-level geolocation as a tool to monitor polar bear (Ursus maritimus) denning ecology: A case study," Anim. Biotelem., 11, doi:10.1186/s40317-023-00323-4, 2023.

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21 Mar 2023

Monitoring polar bears is logistically challenging and expensive. Traditionally, reproductive history has been assessed using permanent marks from physically captured individuals, which requires assumptions about reproductive history based on their status at the time of capture. This is often supplemented with economically costly satellite telemetry (ST) collars restricted to adult females, which yield data on space use and reproductive history.

This study assesses the potential of adapting light-level geolocation (Global location sensing or GLS) tags, developed for birds and fish, to estimate life history metrics for polar bears. Traditionally, GLS uses light intensity and time of day to estimate approximate twice-daily locations. This information, combined with temperature data, can be used to assess approximate locations of maternity denning events, denning timing, general space use, and population connectivity.

Adult females (n = 54) were equipped, some several times, with a total of 103 GLS in Svalbard and Greenland from 2012 to 2021. Of these, 44 were also equipped with 80 ST collars during this period. This yielded GLS and ST data records for each individual up to 9.4 years (mean 4.0 years) and 5.1 years (1.5 years), respectively. Combined with capture information, the GLS and ST collars were used to score reproductive history (determined presence or absence of maternity denning events) for 72–54% of bear winters during this period, respectively. Using GLS yielded on average 4.3 years of unbroken reproductive history records (up to 8 years for some individuals) including denning phenology and age at first reproduction. Additionally, geographic locations could be estimated during spring and autumn (when twilight was present) with an average daily accuracy of 93 km (4–1042 km) and 58 km (5–550 km) when aggregating by season.

This study establishes GLS as a powerful, low-cost method for polar bear population monitoring that can provide data on reproductive history, including age at first reproduction, and maternity denning location and phenology in programs with ongoing recapture. GLS can also be used to monitor males and immatures that cannot wear ST collars.

Characteristics of ringed seal Pusa hispida ('natchiq') denning habitat in Kotzebue Sound, Alaska, during a year of limited sea ice and snow

Lindsay, J.M., and 14 others including K.L. Laidre, "Characteristics of ringed seal Pusa hispida ('natchiq') denning habitat in Kotzebue Sound, Alaska, during a year of limited sea ice and snow," Mar. Ecol. Prog. Ser., 705, doi:10.3354/meps14252, 2023.

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9 Feb 2023

Sea ice and snow are essential to Arctic ecosystems, playing key roles in the lives of Arctic marine mammals and the Indigenous Peoples who rely on them. Ringed seals Pusa hispida (‘natchiq’ in Inupiaq) use snow-covered dens on sea ice for pupping, but quantitative information on denning habitat requirements is limited, and it is unknown how changes in snow depth and sea-ice extent will impact ringed seals. Here, an Indigenous Elder Advisory Council and a multidisciplinary group of scientists used knowledge co-production to quantify fine-scale ringed seal habitat selection patterns in Kotzebue Sound, Alaska (USA), during a year of unprecedentedly limited snow and sea-ice availability. Together, we conducted unoccupied aerial vehicle-based surveys during spring 2019 and related seal counts to survey date, bathymetry, and novel proxies for snow depth and surface roughness that we derived from Landsat 8 surface reflectance and validated with on-ice measurements. Generalized additive models showed that counts of seal groups (all age classes) and pups were associated with later survey dates, deeper water, and habitat with bright Landsat 8 pixel values and intermediate pixel variability, which in turn were correlated with deep snow and surface roughness. We observed shallow snow depths, early sea-ice breakup, and high seal densities consistent with the extreme lack of ice available in 2019. Indigenous Knowledge, intentionally woven with scientific data, provided novel and more nuanced understandings of snow and sea-ice conditions for seals. Our results may give a glimpse at future ringed seal habitat and selection in a warming Arctic.

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In The News

For threatened polar bears, the climate change diet is a losing proposition

Associated Press, Seth Borenstein

With Arctic sea ice shrinking from climate change, many polar bears have to shift their diets to land during parts of the summer. Commenting on a recent study, Kristin Laidre notes that there is a growing body of evidence that polar bears cannot sustain themselves on land as the climate warms and sea ice habitat is lost.

13 Feb 2024

The Scientists Watching Their Life's Work Disappear

New York Times Magazine, Catrin Enhorn

The seven scientists here document the impacts of global warming on the nonhuman world. Their work brings them face to face with realities that few of us see firsthand. Some are stubborn optimists. Some struggle with despair. To varying degrees, they all take comfort in nature's resilience. But they know it goes only so far. These scientists are witnesses to an intricately connected world that we have pushed out of balance. Their faces show the weight they carry.

26 Oct 2023

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

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