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

Abstract

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.

Validation and measurement of physiological stress and reproductive hormones in wolf hair and claws

“…The results of our study suggested there are potential management benefits from using historical samples to evaluate population-level changes in reproductive and stress-related steroid hormones due to environmental stressors or changes in reproductive activity over periods of time. Further, additional physiological parameters such as dietary stable isotopes, trace minerals, or contaminants can be determined in both hair and claw tissues and are incorporated during growth and are therefore temporally linked to hormone concentrations in the same tissue allowing for exploring potential stressors (Bechshøft et al 2012b(Bechshøft et al , 2015Crain et al 2021; M. J. Keogh, ADF&G, unpublished data).…”

“…Although other studies have measured stress‐related or reproductive hormones in claws of other species (Baxter‐Gilbert et al 2014, Karpovich et al 2020, M. J. Keogh, ADF&G, unpublished data), our study is the first attempt to measure hormones in wolf claws. Additionally, we measured hormones in archived tissue samples collected from 4–25 years ago, demonstrating the potential to assess changes in stress and reproductive hormone concentrations in populations over decades (Bechshøft et al 2012 a , Hunt et al 2016, Crain et al 2021).…”

“…Thus, steroid hormone concentrations in wolf hair are related to circulating concentrations between late spring or summer through the fall when hormones are incorporated into the growing hair. Claws, another keratinous tissue, also contain steroid hormones and have been used to examine stress associated with premature birth in dogs (Veronesi et al 2015), stress associated with proximity to roads in turtles (Baxter‐Gilbert et al 2014), and reproductive status in mammals (Karpovich et al 2020, Crain et al 2021; M. J. Keogh, Alaska Department of Fish and Game [ADF&G], unpublished data). Claws contain material deposited continuously during growth, providing a tissue to track physiological information over months to years (Ethier et al 2010).…”

Assessing chronic stress in wild mammals using claw-derived cortisol: a validation using European badgers (Meles meles)

“…The measurement of hormone in hair is further complicated by potential seasonal variation in pelage growth rates and hair lengths ( Maurel et al, 1986 ), whereas claw growth remains relatively consistent in most species examined ( Ethier et al, 2010 ). Although used in turtles ( Baxter-Gilbert et al, 2014 ); chameleons ( Matas et al, 2016 ); cattle ( Comin et al, 2014 ); seals ( Karpovich et al, 2020 ; Crain et al, 2021 ); cats ( Contreras et al, 2021 ); and dogs ( Mack and Fokidis, 2017 ; Jasmine et al, 2018 ), little research has investigated how claw GC concentrations differ within and among free-living individuals, nor explored the sources of this variation.…”

Double-check in lizard age estimation: use of phalanx bone and keratin claw sheath lamellas

“…Mammalian claws include soft internal structures covered by a rigid horn above [23]. The external keratin horn might include the periodically banded structures; this fact proves the presence of annual differences in physiological condition of the animal [24]. The reptile claw comprises bone of distal phalanx and epidermal sheath, with keratinized corneus of the unguis an less keratinized subunguis epidermis [25,26].…”