Larger body size leads to greater female beluga whale ovarian reproductive activity at the southern periphery of their range

Ferguson, Steven H.; Yurkowski, David J.; Hudson, Justine; Edkins, Tera; Willing, Cornelia; Watt, Cortney A.

doi:10.1002/ece3.8367

Cited by 3 publications

(2 citation statements)

References 76 publications

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“…There is some evidence for latitudinal differences in body size in mammals following Bergmann's rule (Meiri and Dayan 2003;Adamczak et al 2020). Indeed, female beluga whales were found to have larger body size at the poleward edge of their range in the Canadian Arctic (Ferguson et al 2021). Although beyond the scope of this study, in light of the recent range expansion to a higher latitude in AUFS, this could potentially have an effect on adult female body size.…”

Section: Discussionmentioning

confidence: 75%

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Is regional variability in environmental conditions driving differences in the early body condition of endemic Australian fur seal pups?

Wall

Thalmann²,

Wotherspoon

et al. 2023

Wildlife Res.

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Context. Good body condition in juvenile marine mammals is crucial for survival and, therefore, population demography. Australian fur seals, endemic to Australia, recently established a breeding colony at the southern edge of their range, at The Needles, a small group of islands in southwest Tasmania (43.6614°S) and a significant distance from their core breeding range in Bass Strait. Aims. We aimed to compare pup body condition at two breeding colonies, distinct in time since establishment and latitude. Specific aims were to: (1) establish the timing of peak pupping, to compare condition of known-age pups, and determine a baseline at The Needles; (2) investigate pup body condition over time at an established colony; and (3) gain insight into the effects of environmental conditions on pup body condition. Methods. We conducted a colony comparison of pup body condition using condition indices at The Needles and an established breeding colony in Bass Strait, Tenth Island, for the 2019/20 and 2020/21 breeding seasons. Pup body condition was quantified at Tenth Island over 18 years (2003-2020) using a long-term morphometric dataset. To establish breeding phenology at these two colonies, we determined peak pupping date for the 2019/20 breeding season using daily pup counts. We assessed the effect of environmental parameters on body condition for the long-term dataset. Key results. Pups from The Needles displayed significantly higher body condition than those from Tenth Island, despite similar peak pupping date. Breeding phenology was consistent with published timing for Australian fur seals. Pup body condition at Tenth Island over the 2-year colony comparison was comparable to the historical average. Environmental drivers that affect maternal foraging efficiency are linked to pup body condition. Conclusions. Higher pup body condition at The Needles is likely underpinned by better foraging conditions resulting in increased pup provisioning levels. Our results indicate that south-west Tasmania is a region of foraging and emerging breeding importance for Australian fur seals. Implications. Future research to monitor pup body condition, maternal foraging behaviour and ecosystem productivity at The Needles will help to provide greater understanding of likely population trajectories at this southernmost breeding site for Australian fur seals.

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Section: Discussionmentioning

confidence: 75%

“…2020). Indeed, female beluga whales were found to have larger body size at the poleward edge of their range in the Canadian Arctic (Ferguson et al . 2021).…”

Section: Discussionmentioning

confidence: 99%

Is regional variability in environmental conditions driving differences in the early body condition of endemic Australian fur seal pups?

Wall

Thalmann²,

Wotherspoon

et al. 2023

Wildlife Res.

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Sexual dimorphism in toothed whales (Odontoceti) follows Rensch’s rule

Caspar

Begall

2022

Mamm Biol

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Rensch’s rule entails that male-biased sexual size dimorphism scales allometrically with body size and is assumed to generally apply to polygynous taxa. However, so far only few mammalian groups have been shown to conform to it. Toothed whales (Odontoceti) not only span a substantial range of body sizes, but are commonly presumed to be predominantly polygynous, thus representing a promising candidate group to test for Rensch’s rule. Here we compiled a dataset of sex-specific body lengths in 57 species of toothed whales and demonstrate that sexual size dimorphism in this group does indeed follow Rensch’s rule. When focusing on selected subgroups of toothed whales, conformity to the rule was prominent among lineages of the speciose superfamily Delphinoidea, while it was not found in the beaked whales of the family Ziphiidae. These results support the assumption that polygynous and polygynandrous mating systems and marked precopulatory intrasexual competition between males are common among toothed whales. However, female-biased sexual size dimorphism as well as monomorphism occur at notable frequencies as well, suggesting that reproductive strategies are nevertheless variable among these marine mammals.

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Assessing seasonal spatial segregation by age class of beluga whales (Delphinapterus leucas) in Western Hudson Bay estuaries

2022

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Segregation of adult males from adult females and immature animals is known to occur in some beluga whale populations, but it is unclear if such segregation occurs in Hudson Bay, where the largest summering population in the world is found. Using imagery from a photographic aerial survey conducted in August 2015, we examined spatial distribution by age class with respect to several environmental variables near two of three main estuaries, Churchill and Seal River, used by Western Hudson Bay belugas in the summer season. Belugas photographed during aerial surveys were classified by age manually using an identification decision tree, and GPS coordinates of their locations were plotted in ArcGIS. Distribution by age class was examined in relation to five habitat characteristics: distance to coastal habitat, bathymetry, sea surface temperature, and extent of river plume. Habitat characteristics and the proportion of animals by age classes were similar in both estuaries, indicating no segregation, and suggesting the environmental data assessed were not associated with patterns of distribution and density of age classes at the spatial and temporal scale being investigated. Overall density of calves was almost three times higher at the Seal River; however, suggesting this location may be preferred for calf rearing in the summer season. Results provide a greater understanding of spatial patterns of beluga whale habitat use in western Hudson Bay, and information useful in conservation and management advice.

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Larger body size leads to greater female beluga whale ovarian reproductive activity at the southern periphery of their range

Cited by 3 publications

References 76 publications

Is regional variability in environmental conditions driving differences in the early body condition of endemic Australian fur seal pups?

Is regional variability in environmental conditions driving differences in the early body condition of endemic Australian fur seal pups?

Sexual dimorphism in toothed whales (Odontoceti) follows Rensch’s rule

Assessing seasonal spatial segregation by age class of beluga whales (Delphinapterus leucas) in Western Hudson Bay estuaries

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