Effects of sea ice on growth rates of an endangered population of gray whales

Gailey, Glenn; Sychenko, Olga; Tyurneva, O.Yu.; Yakovlev, Yu. M.; Vertyankin, Vladimir V.; Wolf, Peter; Drozdov, K. A.; Zhmaev, I.

doi:10.1038/s41598-020-58435-3

Cited by 21 publications

(37 citation statements)

References 42 publications

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“…It is not known whether these calves died or just did not return to the Sakhalin feeding ground. Considering the high site fidelity expressed by Sakhalin gray whales and low survival rates observed during calves' first year of life [45,110], it is more likely these animals died. Low calf survival rates for baleen whale calves is not uncommon and observed in, for example, ENP gray whales [10,111] and humpback whales as well [112].…”

Section: Wnp Population Sizementioning

confidence: 99%

“…The fact that within-season LIR values did not approach zero, and remained fairly constant after the maximum observed within-season lag period of 70-80 days, was indicative of insufficient duration of the survey period to fully capture the migration towards wintering grounds. The nearshore feeding area was typically sea ice-free after June [45], although individuals can arrive on the foraging grounds before ice-free conditions [30,45], and photo-identification field seasons mostly started in July. Survey efforts ended around the beginning of October due to adverse weather conditions often prevailing in this period.…”

Section: Site Fidelity and Movement Patternsmentioning

confidence: 99%

“…This is especially the case when bioenergetic models are used that require information on anthropogenic or natural factors affecting energy intake, energetic cost of movement patterns over the available feeding areas and difference in prey availability in these areas [49,50]. In fact, interannual variation in the energy reserves of whales has been detected and correlated with both prey availability and whale fecundity [113], as well as with sea spring ice cover [45]. During years with more sea ice cover or lower prey availability in the nearshore feeding area, animals might make more use of the offshore area to compensate.…”

Section: Site Fidelity and Movement Patternsmentioning

confidence: 99%

“…One key difference between the WNP feeding grounds off Sakhalin versus those used by ENP gray whales, is the spatial area of these feeding grounds. With approximately 600 and 700 km 2 for the nearshore and offshore feeding areas, respectively, the feeding grounds used by WNP whales [45] are drastically smaller in comparison to those used by ENP whales. A tagging study on 23 individuals in the Pacific Coast Feeding Group (PCFG), a subset of ENP whales who do not migrate to the Bering, Chukchi or Beaufort seas to feed, showed individual feeding-area home ranges (90% isopleth) and core areas (50% isopleth) of 3,107 km 2 (±4,140) and 840 km 2 (±1,159), respectively [46].…”

Section: Introductionmentioning

confidence: 96%

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Site-fidelity and spatial movements of western North Pacific gray whales on their summer range off Sakhalin, Russia

Bröker

Gailey²,

Tyurneva

et al. 2020

PLoS ONE

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The Western North-Pacific (WNP) gray whale feeding grounds are off the northeastern coast of Sakhalin Island, Russia and is comprised of a nearshore and offshore component that can be distinguished by both depth and location. Spatial movements of gray whales within their foraging grounds were examined based on 13 years of opportunistic vessel and shore-based photo-identification surveys. Site fidelity was assessed by examining annual return and resighting rates. Lagged Identification Rates (LIR) analyses were conducted to estimate the residency and transitional movement patterns within the two components of their feeding grounds. In total 243 individuals were identified from 2002-2014, among these were 94 calves. The annual return rate over the period 2002-2014 was 72%, excluding 35 calves only seen one year. Approximately 20% of the individuals identified from 2002-2010 were seen every year after their initial sighting (including eight individuals that returned for 13 consecutive years). The majority (239) of the WNP whales were observed in the nearshore area while only half (122) were found in the deeper offshore area. Within a foraging season, there was a significantly higher probability of gray whales moving from the nearshore to the offshore area. No mother-calf pairs, calves or yearlings were observed in the offshore area, which was increasingly used by mature animals. The annual return rates, and population growth rates that are primarily a result of calf production with little evidence of immigration, suggest that this population is demographically self-contained and that both the nearshore and offshore Sakhalin feeding grounds are critically important areas for their summer annual foraging activities. The nearshore habitat is also important for mother-calf pairs, younger individuals, and recently weaned calves. Nearshore feeding could also be energetically less costly compared to foraging in the deeper offshore habitat and provide more protection from predators, such as killer whales.

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Section: Wnp Population Sizementioning

confidence: 99%

Section: Site Fidelity and Movement Patternsmentioning

confidence: 99%

Section: Site Fidelity and Movement Patternsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

See 2 more Smart Citations

Site-fidelity and spatial movements of western North Pacific gray whales on their summer range off Sakhalin, Russia

Bröker

Gailey²,

Tyurneva

et al. 2020

PLoS ONE

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“…The occurrence of carotenoids within the mineralized bone matrix is unknown, however their origin can be explained. The north western gray whales diet [50] is mostly composed of crustaceans, especially mysids (Mysidacea) [51] which are rich in carotenoids, lipo-glyco-carotenoproteins [52] highly-unsaturated fatty acids and phospholipids [53,54].…”

Section: Resultsmentioning

confidence: 99%

Extreme biomineralization: the case of the hypermineralized ear bone of gray whale (Eschrichtius robustus)

et al. 2020

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Selected hypermineralized bones (rostrum and tympanic bullae) have yet to be characterized for diverse species of whales (Cetacea). Hypermineralization in these structures is an example of extreme biomineralization that, however, occurs at temperatures around 36 °C. In this study we present the results of analytical investigations of the specimen of tympanic bulla isolated from gray whale (Eschrichtius robustus) for the first time. Examination of the internal surface of the bone mechanically crushed under a press revealed the presence of a lipid-containing phase, which did not disappear even after complete demineralization of the bone material. Additionally, analytical investigations including CARS, ATR-FTIR, Raman and XRD confirmed the presence of carbonated bioapatite and a collagen- lipid complex as the main components of this up to 2.34 kg/cm3 dense bone. Our experimental results open the way for further research on understanding of the principles of hypermineralization in highly specialized whale bones.

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Predicting the population consequences of acoustic disturbance, with application to an endangered gray whale population

McHuron

Aerts²,

Gailey³

et al. 2021

Ecological Applications

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Acoustic disturbance is a growing conservation concern for wildlife populations because it can elicit physiological and behavioral responses that can have cascading impacts on population dynamics. State‐dependent behavioral and life history models implemented via Stochastic Dynamic Programming (SDP) provide a natural framework for quantifying biologically meaningful population changes resulting from disturbance by linking environment, physiology, and metrics of fitness. We developed an SDP model using the endangered western gray whale (Eschrichtius robustus) as a case study because they experience acoustic disturbance on their summer foraging grounds. We modeled the behavior and physiological dynamics of pregnant females as they arrived on the feeding grounds and predicted the probability of female and offspring survival, with and without acoustic disturbance and in the presence/absence of high prey availability. Upon arrival in mid‐May, pregnant females initially exhibited relatively random behavior before they transitioned to intensive feeding that resulted in continual fat mass gain until departure. This shift in behavior co‐occurred with a change in spatial distribution; early in the season, whales were more equally distributed among foraging areas with moderate to high energy availability, whereas by mid‐July whales transitioned to predominate use of the location that had the highest energy availability. Exclusion from energy‐rich offshore areas led to reproductive failure and in extreme cases, mortality of adult females that had lasting impacts on population dynamics. Simulated disturbances in nearshore foraging areas had little to no impact on female survival or reproductive success at the population level. At the individual level, the impact of disturbance was unequally distributed across females of different lengths, both with respect to the number of times an individual was disturbed and the impact of disturbance on vital rates. Our results highlight the susceptibility of large capital breeders to reductions in prey availability, and indicate that who, where, and when individuals are disturbed are likely to be important considerations when assessing the impacts of acoustic activities. This model provides a framework to inform planned acoustic disturbances and assess the effectiveness of mitigation strategies for large capital breeders.

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Effects of sea ice on growth rates of an endangered population of gray whales

Cited by 21 publications

References 42 publications

Site-fidelity and spatial movements of western North Pacific gray whales on their summer range off Sakhalin, Russia

Site-fidelity and spatial movements of western North Pacific gray whales on their summer range off Sakhalin, Russia

Extreme biomineralization: the case of the hypermineralized ear bone of gray whale (Eschrichtius robustus)

Predicting the population consequences of acoustic disturbance, with application to an endangered gray whale population

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