skip to main content


This content will become publicly available on January 1, 2025

Title: Contrasting offspring dependence periods and diving development rates in two closely related marine mammal species

Understanding the ontogeny of diving behaviour in marine megafauna is crucial owing to its influence on foraging success, energy budgets, and mortality. We compared the ontogeny of diving behaviour in two closely related species—northern elephant seals (Mirounga angustirostris, n= 4) and southern elephant seals (Mirounga leonina, n= 9)—to shed light on the ecological processes underlying migration. Although both species have similar sizes and behaviours as adults, we discovered that juvenile northern elephant seals have superior diving development, reaching 260 m diving depth in just 30 days, while southern elephant seals require 160 days. Similarly, northern elephant seals achieve dive durations of approximately 11 min on their first day of migration, while southern elephant seals take 125 days. The faster physiological maturation of northern elephant seals could be related to longer offspring dependency and post-weaning fast durations, allowing them to develop their endogenous oxygen stores. Comparison across both species suggests that weaned seal pups face a trade-off between leaving early with higher energy stores but poorer physiological abilities or leaving later with improved physiology but reduced fat stores. This trade-off might be influenced by their evolutionary history, which shapes their migration behaviours in changing environments over time.

 
more » « less
Award ID(s):
2052497
PAR ID:
10525500
Author(s) / Creator(s):
; ; ; ; ; ; ;
Publisher / Repository:
Royal Society Open Science
Date Published:
Journal Name:
Royal Society Open Science
Volume:
11
Issue:
1
ISSN:
2054-5703
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    We report on an accumulation of mummified southern elephant seals (Mirounga leonina)from Inexpressible Island on the Victoria Land Coast (VLC), western Ross Sea, Antarctica. This accumulation is unusual, as elephant seals typically breed and molt on sub‐Antarctic islands further north and do not currently occupy the VLC. Prior ancient DNA analyses revealed that these seals were part of a large, Antarctic breeding population that crashed ~1,000 yr ago. Radiocarbon dates for Inexpressible Island mummies range from 380 to 3,270 yr before present, too old to have been created by Scott's Northern Party in 1912 and varying too widely in age to represent a catastrophic death assemblage. Skeletal measurements reveal that most Inexpressible Island mummies are adult or subadult males. The presence of male elephant seals on Inexpressible Island until several hundred years ago suggests that, at a minimum, it served as a haul‐out site for the large Antarctic population and may have hosted a breeding colony. The conditions that allowed this Antarctic population to use the Ross Sea, the factors spurring its decline, and the implications for the adaptability and sensitivity of the species to environmental change all merit further study.

     
    more » « less
  2. null (Ed.)
    The ability to maintain a high core body temperature is a defining characteristic of all mammals, yet their diverse habitats present disparate thermal challenges that have led to specialized adaptations. Marine mammals inhabit a highly conductive environment. Their thermoregulatory capabilities far exceed our own despite having limited avenues of heat transfer. Additionally, marine mammals must balance their thermoregulatory demands with those associated with diving (i.e. oxygen conservation), both of which rely on cardiovascular adjustments. This review presents the progress and novel efforts in investigating marine mammal thermoregulation, with a particular focus on the role of peripheral perfusion. Early studies in marine mammal thermal physiology were primarily performed in the laboratory and provided foundational knowledge through in vivo experiments and ex vivo measurements. However, the ecological relevance of these findings remains unknown because comparable efforts on free-ranging animals have been limited. We demonstrate the utility of biologgers for studying their thermal adaptations in the context in which they evolved. Our preliminary results from freely diving northern elephant seals (Mirounga angustirostris) reveal blubber’s dynamic nature and the complex interaction between thermoregulation and the dive response due to the dual role of peripheral perfusion. Further exploring the potential use of biologgers for measuring physiological variables relevant to thermal physiology in other marine mammal species will enhance our understanding of the relative importance of morphology, physiology, and behavior for thermoregulation and overall homeostasis. 
    more » « less
  3. Abstract

    Utilization of marine photovoltaic energy is primarily focused on surface harvesting with limited photovoltaic cell implementations in submarine environments. Potential applications include marine wildlife telemetry devices, autonomous underwater vehicles, or remote sensing assets. In these applications, understanding the power at depth is critical, but there has yet to be a long‐term study of cell performance in a realistic marine environment that spans time, geographic location, and depth. In this paper, we present photovoltaic assessments carried out by devices mounted to adult female northern elephant seals (Mirounga angustirostris) during their spring migrations in the Pacific Ocean with deployment times between 76 and 107 days. Encompassing a large geographic area between Santa Cruz, California, and the Aleutian Islands of Alaska during their migrations, elephant seal behavior allows for repeated depth profiles each day, making them an ideal host for subsurface power assessments. This paper presents the first longitudinal study of photovoltaic cell performance in the marine environment that spans location, time, and depth. This work discusses the calibration, data time alignment, and power calculations of these oceanic deployments. Deployment results, including power results and energy predictions from the data record, are presented up to 22 m in depth. We highlight how the recorded power data of these cells compares to previously published results and how depth impacts subsurface power and energy harvesting.

     
    more » « less
  4. Abstract

    The profound impacts that maternal provisioning of finite energy resources has on offspring survival have been extensively studied across mammals. This study shows that in addition to calories, high hemoprotein concentrations in diving mammals necessitates exceptional female-to-pup iron transfer. Numerous indices of iron mobilization (ferritin, serum iron, total-iron-binding-capacity, transferrin saturation) were significantly elevated during lactation in adult female Weddell seals (Leptonychotes weddellii), but not in skip-breeders. Iron was mobilized from endogenous stores for incorporation into the Weddell seal’s milk at concentrations up to 100× higher than terrestrial mammals. Such high rates of iron offload to offspring drew from the female’s own heme stores and led to compromised physiologic dive capacities (hemoglobin, myoglobin, and total body oxygen stores) after weaning their pups, which was further reflected in shorter dive durations. We demonstrate that lactational iron transfer shapes physiologic dive thresholds, identifying a cost of reproduction to a marine mammal.

     
    more » « less
  5. Elephant seals sleep 2 hours a day while diving for months at sea, rivaling the record for the least sleep among mammals. 
    more » « less