Using claws to compare reproduction, stress, and diet of female bearded and ringed seals in the Bering and Chukchi seas, Alaska, between 1953-1968 and 1998-2014.
|Temporal extent||1953 -2014|
|Author(s)||Crain Danielle1, Karpovich Shawna2, Quakenbush Lori2, Polasek Lori3|
|Affiliation(s)||1 : Baylor University, Waco TX, 76706, USA
2 : Alaska Department of Fish and Game, 1300 College Road, Fairbanks, AK 99701, USA
3 : Alaska Department of Fish and Game, 1255 W 8th St, Juneau, AK 99802, USA
|Keyword(s)||bearded seals, ringed seals, ice seals, cortisol, progesterone, pregnancy, claws, stable isotopes|
Rapid climate warming is decreasing sea ice thickness, extent, and duration. Marine mammals such as bearded (Erignathus barbatus) and ringed (Pusa hispida) seals, which use sea ice for pupping, molting and resting, may be negatively affected. Claws from bearded and ringed seals store up to 14 and 12 years of sequential analyte data, respectively. These data can be used to compare reproduction, stress, and diet across decades. In this study, we compare progesterone, cortisol, and carbon and nitrogen stable isotopes in female bearded and ringed seals during 1953-1968 (pre-1968, a period prior to sea ice decline) to 1998-2014 (post-1998, a period during sea ice decline). When comparing these periods, bearded seals had statistically higher cortisol concentrations post-1998, and for both species δ13C was more negative post-1998, while progesterone and δ15N did not change. There was a positive relationship between progesterone and cortisol Z-scores for both species, except for ringed seals post-1998. There was a negative relationship between cortisol Z-scores and δ13C for bearded seals evident in post-1998 indicating that higher cortisol Z-scores are associated with more negative δ13C in bearded seals in recent years. This negative relationship between cortisol and δ13C in bearded seals suggests a shift to higher prey diversity, possibly due to changes in sea ice in the Pacific Arctic evident post 1998. Progesterone Z-scores corresponded to expected differences among non-pregnant, unimplanted, implanted, and post-partum individuals. Using these data, pregnancy history was determined for reproductive years for each individual female sampled which could allow for yearly pregnancy rates to be calculated given a large enough representative sample of the population. These results combine decades of observational studies with hormones and stable isotopes to infer changes in reproduction, stress, and diet, as well as the connection between these life history parameters.
|Acknowledgments||Information on seal diet and condition would not be possible without the willingness of the seal hunters to contribute samples from their harvest, the support of their communities, local governments, and Tribal Councils. We thank Anna Bryan for assistance in entering and error checking recent data. We thank the University of Alaska museum in Fairbanks, AK for access to the following historical claws: UAM:Mamm:11434, 121684, 121735, 121751, 121813, 121815, 121816, 121818, 181827, 121829, 121833, 121897, 121930, 122132, 122245, 122561, 19059, 19062, 36825, 36826, 36830. We also thank two anonymous reviewers for their comments. Research was funded by the National Oceanic and Atmospheric Administration (NOAA), National Marine Fisheries Service under award NA16NMF4390029 to the Alaska Department of Fish and Game. Marine mammal samples were collected under NMFS Permit Nos 358-1585, 358-1787, 15234, and 20466 issued to ADF&G.|