Work

Multidecadal shifts in hooded seal dive behaviour in a changing ocean

Year: 2026

Type: article

Abstract: The high northern latitudes are warming rapidly, reducing sea ice coverage and altering salinity regimes, with widespread ecosystem-level consequences. Although horizontal range shifts of marine animals under climate change are well documented, long-term changes in vertical habitat use by marine predators remain poorly understood. We analyzed a three-decade biologging dataset (1992–2019) from 45 hooded seals ( Cystophora cristata) breeding in the Gulf of St. Lawrence to investigate how this population has altered its diving behaviour in response to climate change. Using multinomial generalized additive mixed models, we quantified dive duration and depth across sex, functional oceanographic domains, decade, and season. As males and females differ in physiology, and partition the water column during foraging, we assessed whether climate-driven changes in vertical habitat structure would differentially affect the diving behaviour between sexes. Sexual dimorphism persisted, with females making shorter and shallower dives more frequently than males. However, both sexes experienced marked shifts in dive duration, from predominantly 5–15 min dives in the 1990s to 15–25 min dives in the 2000s and 2010s. These changes were spatially structured, reflecting basin-scale thermohaline reorganization, and temporally coordinated with migration. Shallow dives dominated early and late migration, whereas deeper, longer dives peaked mid-migration. Our results demonstrate behavioural plasticity in response to changing vertical habitat conditions.

Source: Arctic Science

DOI: 10.1139/as-2025-0108