Larger females have more calves: influence of maternal body length on fecundity in North Atlantic right whales

Stewart, JD; Durban, JW; Europe, Hollis M.; Fearnbach, Holly; Hamilton, P. K.; Knowlton, AR; Lynn, MS; Miller, C.A.; Perryman, WL; Tao, BWH; Moore, M. J.

doi:10.3354/meps14040

Cited by 27 publications

(29 citation statements)

References 28 publications

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“…We found that calves' TLs were positively related to their mothers' TLs, meaning longer calves were associated with longer mothers (Figure 5). This same trend was observed in humpback whales in Eastern and Western Australia (Christiansen et al, 2016;Russel et al, 2022), as well as in Eastern North Pacific gray whales (Christiansen et al, 2021) and southern and North Atlantic right whales (Best and Rüther, 1992;Christiansen et al, 2018;Stewart et al, 2022). In general, longer body lengths are associated with increased calf survivorship, as well as increased reproductive success in baleen whales (Pack et al, 2009;Stewart et al, 2022).…”

Section: Body Size Of Mother-calf Pairssupporting

confidence: 64%

“…Photogrammetry from unoccupied aircraft systems (UAS, UAVs, or drones) is an effective non-invasive tool for obtaining measurements of cetaceans in remote environments (Durban et al, 2015). UAS have been used to measure body condition in blue (Balaenoptera musculus), gray (Eschrichtius robustus), and northern (Eubalaena glacialis) and southern right whales (Eubalaena australis) (Christiansen et al, 2016;Durban et al, 2016;Christiansen et al, 2018;Lemos et al, 2020;Christiansen et al, 2021;Stewart et al, 2022;Torres et al, 2022). For humpback whales, studies have described trends in body condition along the migration routes (Christiansen et al, 2020b;Russell et al, 2022), the North Atlantic feeding grounds (Aoki et al, 2021), and the Western Australian breeding grounds (Christiansen et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Seasonal gain in body condition of foraging humpback whales along the Western Antarctic Peninsula

et al. 2022

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Most baleen whales are capital breeders that use stored energy acquired on foraging grounds to finance the costs of migration and reproduction on breeding grounds. Body condition reflects past foraging success and can act as a proxy for individual fitness. Hence, monitoring the seasonal gain in body condition of baleen whales while on the foraging grounds can inform how marine mammals support the costs of migration, growth, and reproduction, as well as the nutritional health of the overall population. Here, we use photogrammetry from drone-based imagery to examine how the body condition of humpback whales (Megaptera novaeangliae) changed over the foraging season (November to June) along the Western Antarctic Peninsula (WAP) from 2017 to 2019. This population (IWC stock G) is recovering from past whaling and is growing rapidly, providing an opportunity to study how whales store energy in a prey-rich environment. We used a body area index (BAI) to estimate changes in body condition and applied a Bayesian approach to incorporate measurement uncertainty associated with different drone types used for data collection. We used biopsy samples to determine sex and pregnancy status, and a length-based maturity classification to assign reproductive classes (n = 228; calves = 31, juveniles = 82, lactating females = 31, mature males = 12, mature unknown sex = 56, non-pregnant females = 12, pregnant females = 3, pregnant & lactating females = 1). Average BAI increased linearly over the feeding season for each reproductive class. Lactating females had lower BAI compared to other mature whales late in the season, reflecting the high energetic costs of nursing a calf. Mature males and non-pregnant females had the highest BAI values. Calves and juvenile whales exhibited an increase in BAI but not structural size (body length) over the feeding season. The body length of lactating mothers was positively correlated with the body length of their calves, but no relationship was observed between the BAI of mothers and their calves. Our study establishes a baseline for seasonal changes in the body condition for this humpback whale population, which can help monitor future impacts of disturbance and climate change.

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Section: Body Size Of Mother-calf Pairssupporting

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Seasonal gain in body condition of foraging humpback whales along the Western Antarctic Peninsula

et al. 2022

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“…Another recent study found evidence of stunted growth in young right whales (<10 years old) that were observed with attached gear or whose mothers had attached gear or severe entanglement injuries while nursing (Stewart et al, 2021) indicating an additional sub‐lethal effect. This stunted growth effect has also impacted the reproductive output of females (Stewart et al 2022). Here we apply another tool—photographic evidence of health—to assess how entanglements are affecting right whale health.…”

Section: Introductionmentioning

confidence: 99%

Fishing gear entanglement threatens recovery of critically endangered North Atlantic right whales

Knowlton

Clark

Hamilton

et al. 2022

Conservat Sci and Prac

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North Atlantic right whales frequently become entangled in fishing gear, which can negatively affect their reproductive output and probability of survival. We estimated individual whale health from a hierarchical Bayesian model fit to photographic indices of health. We reviewed 696 whales sighted from 1980 to 2011 and assigned 1196 entanglement events to 573 individuals in six categories of increasing injury severity and estimated monthly median health scores (0-100 scale) for the duration of their life within the study period. We then quantified the relationship between entanglement injury events and their severity with survival, reproduction, and population health. Severe entanglements resulted in worse health for all whales-males and females with severe injuries were eight times more likely to die than males with minor injuries. Females with severe injuries that survived had the lowest birth rates. Though the relationship between entanglement and fecundity was complex, we found that as the health of reproductively active females declined, their calving intervals increased.Unimpacted whale health scores declined significantly over three decades, 1980s, 1990s, and 2000s, suggesting food limitations may be contributing to population-wide health declines. Decadal health scores of entangled whales showed a more notable reduction in health suggesting a clear and perhaps synergistic effect.

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“…Energy budgets are also affected by variability in the distribution and availability of their copepod prey (primarily Calanus finmarchicus ), which has been linked with female reproductive success (Meyer‐Gutbrod et al 2015). Likely as a result of energetic effects, total body lengths have decreased over time (Stewart et al 2021), which further impacts reproductive output (Stewart et al 2022). Whales are also exposed to anthropogenic noise (Hatch et al 2012), chemical pollutants and biotoxins (Doucette et al 2012), which can compromise health (e.g.…”

Section: Introductionmentioning

confidence: 99%

Estimating the effects of stressors on the health, survival and reproduction of a critically endangered, long‐lived species

Pirotta

Schick

Hamilton

et al. 2023

Oikos

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Quantifying the cumulative effects of stressors on individuals and populations can inform the development of effective management and conservation strategies. We developed a Bayesian state–space model to assess the effects of multiple stressors on individual survival and reproduction. In the model, stressor effects on vital rates are mediated by changes in underlying health, allowing for the comparison of effect sizes while accounting for intrinsic factors that might affect an individual's vulnerability and resilience. We applied the model to a 50‐year dataset of sightings, calving events and stressor exposure of critically endangered North Atlantic right whales Eubalaena glacialis. The viability of this population is threatened by a complex set of stressors, including vessel strikes, entanglement in fishing gear and fluctuating prey availability. We estimated that blunt and deep vessel strike injuries and severe entanglement injuries had the largest effect on the health of exposed individuals, reinforcing the urgent need for mitigation measures. Prey abundance had a smaller but protracted effect on health across individuals, and estimated long‐term trends in survival and reproduction followed the trend of the prey index, highlighting that long‐term ecosystem‐based management strategies are also required. Our approach can be applied to quantify the effects of multiple stressors on any long‐lived species where suitable indicators of health and long‐term monitoring data are available.

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Larger females have more calves: influence of maternal body length on fecundity in North Atlantic right whales

Cited by 27 publications

References 28 publications

Seasonal gain in body condition of foraging humpback whales along the Western Antarctic Peninsula

Seasonal gain in body condition of foraging humpback whales along the Western Antarctic Peninsula

Fishing gear entanglement threatens recovery of critically endangered North Atlantic right whales

Estimating the effects of stressors on the health, survival and reproduction of a critically endangered, long‐lived species

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