Population-specific sex and size variation in long-term foraging ecology of belugas and narwhals

Abstract

Intraspecific variation in resource use by individuals of different age, sex or size may reflect differing energetic requirements and physiological constraints. Males and females often show differences in diet owing to sexual size dimorphism, different life histories and/or habitat use. Here, we investigate how sex and size influence the long-term foraging ecology of belugas and narwhals in Greenland, using stable isotopes of carbon and nitrogen from bone collagen. We show that males have a higher trophic level and a larger ecological niche than females in West Greenland belugas and in East Greenland narwhals. In addition, for these two populations, we find that δ 15 N increases with size, particularly in males. We hypothesize that sexual size dimorphism together with strong maternal investment drive these differences. By contrast, we find no differences in foraging ecology between sexes in West Greenland narwhals and observe no influence of size on trophic level. This may reflect the influence of interspecific competition in West Greenland, where the distributions of belugas and narwhals overlap, and/or geographical resource partitioning among different summer aggregations of narwhals. Our results suggest that sex and size variations in diet are population dependent, and probably the result of varying ecological interactions.

Combining δ13C and δ15N from bone and dentine in marine mammal palaeoecological research: insights from toothed whales

“…For one of the narwhal samples (ID: 956), we did not have access to the tusk, and therefore only sampled bone and embedded tooth. For belugas, we drilled tooth dentine from each skull; δ 13 C and δ 15 N data from the same specimens have been published previously in [13], and re-analyzed by [14]. See detailed sample information in Supplementary Table 1.…”

“…To contextualise the data generated in our study, we combined our findings with published δ 13 C and δ 15 N bone records (also from skulls) from 40 WG narwhals, 39 EG narwhals, and one additional beluga [14].…”

“…Boxplots showing the average differences in δ 13 C and δ 15 N composition between various skeletal elements analyzed from narwhal (tusk:bone, embedded tooth:bone) and beluga (tooth:bone). (A) δ 13 C and δ 15 N raw composition, with δ 13 C corrected for the Suess effect; (B) δ 13 C and δ 15 N corrected using the correction factor estimated for each species/skeletal element (data for narwhal: Supplementary Table 2; data for beluga: Supplementary Table 3); and (C) δ 13 C and δ 15 N corrected using the correction factors estimated for each narwhal population, considering known population differences [14]. All data can be found in Supplementary Table 4.…”

The Validation of a Non-Invasive Skin Sampling Device for Detecting Cetacean Poxvirus

“…Cetaceans' skin is considered a multidimensional feature that can provide a wealth of information, forming the basis of research in a wide number of studies covering a broad range of scientific branches [1][2][3][4][5][6][7][8]. Hence, this tissue has been used for long-term health assessments, enabling us to gain a closer look at the health status of marine mammals and aquatic ecosystems [9][10][11][12].…”

How low can you go: sex identification from low-quantity sequencing data despite lacking assembled sex chromosomes

“…Accurate sex identification is critical for elucidating the life history, behaviour, social structure, and demography of a species. It is particularly important for taxa where females and males differ in prey preference (e.g., Louis et al 2021), social interactions and mating behaviour (e.g., Amos, Schlötterer, and Tautz 1993;Pečnerová et al 2017), and seasonal movements and dispersal (e.g., Dobson and Stephen Dobson 1982;Greenwood 1980;Gower et al 2019). Reliable sex identification may also elucidate the impacts of past and present anthropogenic activities on wildlife, including prehistoric hunting or domestication practices (e.g., Nistelberger et al 2019), and the identification of the sex of and sex biases in ongoing wildlife poaching (e.g., Malisa et al 2005).…”