Trade-offs between foraging reward and mortality risk drive sex-specific foraging strategies in sexually dimorphic northern elephant seals

• Published in: Royal Society Open Science
• Main Authors: Kienle, Sarah S., Friedlaender, Ari S., Crocker, Daniel E., Mehta, Rita S., Costa, Daniel P.
• Other Authors: E&P Sound and Marine Life Joint Industry Project of the International Association of Oil and Gas Producers, Alfred P. Sloan Foundation, Office of Naval Research, NOAA Dr. Nancy Foster Scholarship Program, David and Lucile Packard Foundation, Gordon and Betty Moore Foundation, University of California Natural Reserve System, National Ocean Partnership Project
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2022
• Subjects: Elephant Seals
• Online Access: http://dx.doi.org/10.1098/rsos.210522; https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.210522; https://royalsocietypublishing.org/doi/full-xml/10.1098/rsos.210522

Sex-specific phenotypic differences are widespread throughout the animal kingdom. Reproductive advantages provided by trait differences come at a cost. Here, we link sex-specific foraging strategies to trade-offs between foraging reward and mortality risk in sexually dimorphic northern elephant seals ( Mirounga angustirostris ). We analyse a decadal dataset on movement patterns, dive behaviour, foraging success and mortality rates. Females are deep-diving predators in open ocean habitats. Males are shallow-diving benthic predators in continental shelf habitats. Males gain six times more mass and acquire energy 4.1 times faster than females. High foraging success comes with a high mortality rate. Males are six times more likely to die than females. These foraging strategies and trade-offs are related to different energy demands and life-history strategies. Males use a foraging strategy with a high mortality risk to attain large body sizes necessary to compete for females, as only a fraction of the largest males ever mate. Females use a foraging strategy with a lower mortality risk, maximizing reproductive success by pupping annually over a long lifespan. Our results highlight how sex-specific traits can drive disparity in mortality rates and expand species' niche space. Further, trade-offs between foraging rewards and mortality risk can differentially affect each sex's ability to maximize fitness.