Sex‐related differences in the postmolt distribution of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea

Abstract

The population of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea is in a unique position on the continental shelf edge, with vast shelf waters to the south, and deep Southern Ocean to the north. We describe sex-related differences in the winter distribution of this population, from data collected by 20 conductivity-temperature-depth satellite relay data loggers deployed in February 2011 at the end of the annual molt. The regional daily speed was calculated, and a state-space model was used to estimate behavioral states to positions along individuals' tracks. GLMMs estimated that males and smaller individuals, diving in shallower water, traveled less far per day of deployment (males 14.6 AE 2.26 km/d, females 18.9 AE 2.42 km/d), and males were estimated to dive in shallower water (males 604 AE 382 m, females 1,875 AE 1,458 m). Males and smaller individuals were also estimated to be more resident; males spent an average 83.4% AE 7.7% of their time in a resident behavioral state, compared to females at 74.1% AE 7.1%. This evidence that male and female Weddell seals in the southern Weddell Sea are adopting different strategies has not been shown elsewhere along their circumpolar distribution.

From pup to predator: generalized hidden Markov models reveal rapid development of movement strategies in a naïve long‐lived vertebrate

“…Sex differences in activity budgets were not evident in Scottish pups, suggesting that sex‐specific ontogenetic changes are not driven solely by physiological differences, but are likely also influenced by environmental factors. Similar regional sex differences in foraging behaviour have been reported for adult Weddell seals Leptonychotes weddellii (Langley et al ), but a causal mechanism has not been identified. Such behavioural plasticity might be driven by regional and seasonal differences in the diversity of available foraging habitat or prey types.…”

Sex-specific variation in the use of vertical habitat by a resident Antarctic top predator

“…A detailed description of the deployment technique and individual deployment data are presented in [47,53]. Dive data were collected using algorithms developed for high-latitude, deepdiving seals [48,49,54] and CTD data were collected, calibrated, and processed according to MEOP (marine mammals exploring the oceans pole to pole) Consortium standards [20].…”

“…We use HMMs to identify Weddell seal dive types or vertical movement states, and the effect of temporal covariates on the probability of switching between them. Geographical differences in diving activity [47] suggest that the two sexes may use different vertical habitat. We identify the depths where seals spend time hunting and link hunting activity to in situ oceanographic conditions, making this the first study to describe sex-specific preferences for vertical habitat in this circumpolar resident top predator.…”

Weddell seal behaviour during an exceptional oceanographic event in the Filchner-Ronne Ice Shelf in 2017

“…Weddell seals have been intensively studied in the western Ross Sea and East Antarctica (e.g. Stirling 1969, Harcourt et al 2000, Burns & Kooyman 2001, Hindell et al 2002, Lake et al 2005, Wheatley et al 2006, Heerah et al 2013); however, our understanding of their ecology in the Weddell Sea in the wintertime is still sparse (Langley et al 2018, Nachtsheim et al 2019, Photopoulou et al 2020). Here, we document the behaviour and habitat utilization of four Weddell seals in the Filchner-Ronne Ice Shelf region in 2017.…”