Reproductive success and offspring survival decline for female elephant seals past prime age

Allison R Payne; Max F Czapanskiy; A Marm Kilpatrick; Patrick W Robinson; Cara M O Munro; Kelli Ong; Adrien Bastidas; Alegra O Negrete; Brecken Theders; Bryn Stillwell; Danissa Coffey; Elijah Schweitzer; Elise Baugh; Jasmine Salazar; Keenan Chau-Pech; Mason Rodrigues; Mimi Chavez; Savanna Wright; Sofia Rivas; Joanne Reiter; Daniel P Costa; Roxanne S Beltran

doi:10.1111/1365-2656.14226

Reproductive success and offspring survival decline for female elephant seals past prime age

J Anim Ecol. 2024 Nov 19. doi: 10.1111/1365-2656.14226. Online ahead of print.

Authors

Allison R Payne¹, Max F Czapanskiy^{2

3

4}, A Marm Kilpatrick¹, Patrick W Robinson¹, Cara M O Munro¹, Kelli Ong¹, Adrien Bastidas¹, Alegra O Negrete¹, Brecken Theders¹, Bryn Stillwell¹, Danissa Coffey¹, Elijah Schweitzer¹, Elise Baugh¹, Jasmine Salazar¹, Keenan Chau-Pech¹, Mason Rodrigues¹, Mimi Chavez¹, Savanna Wright¹, Sofia Rivas¹, Joanne Reiter⁵, Daniel P Costa^{1

4}, Roxanne S Beltran¹

Affiliations

¹ Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California, USA.
² Department of Ocean Sciences, University of California, Santa Cruz, California, USA.
³ Bren School of Environmental Science and Management, University of California Santa Barbara, Santa Barbara, California, USA.
⁴ College of Creative Studies, University of California Santa Barbara, Santa Barbara, California, USA.
⁵ Institute of Marine Sciences, Long Marine Laboratory, University of California Santa Cruz, Santa Cruz, California, USA.

PMID: 39562521
DOI: 10.1111/1365-2656.14226

Abstract

Maternal age can influence reproductive success and offspring fitness, but the timing, magnitude and direction of those impacts are not well understood. Evolutionary theory predicts that selection on fertility senescence is stronger than maternal effect senescence, and therefore, the rate of maternal effect senescence will be faster than fertility senescence. We used a 36-year study of northern elephant seals (Mirounga angustirostris) to investigate reproductive senescence. Our dataset included 103,746 sightings of 1203 known-age female northern elephant seals. We hypothesized that fertility (maternal reproductive success), offspring survival and recruitment into the breeding population, and male offspring production would decline with advanced maternal age. Furthermore, we hypothesized that older females would shorten their moulting haul out to allow for more time spent foraging. We found evidence for both fertility and maternal effect senescence, but no evidence for senescence impacting offspring recruitment or sex ratio. Breeding probability declined from 96.4% (95% CI: 94.8%-97.5%) at 11 years old to 89.7% (81.9%-94.3%) at 19 years old, and the probability of offspring survival declined from 30.3% (23.6%-38.0%) at 11 years old to 9.1% (3.2%-22.9%) at 19 years old. The rates of decline for fertility and maternal effect senescence were not different from each other. However, maternal effect senescence had a substantially greater impact on the number of offspring surviving to age 1 compared to fertility senescence. Compared to a hypothetical non-senescent population, maternal effect senescence resulted in 5.3% fewer surviving pups, whereas fertility senescence resulted in only 0.3% fewer pups produced per year. These results are consistent with evolutionary theory predicting weaker selection on maternal effect than fertility senescence. Maternal effect senescence may therefore be more influential on population dynamics than fertility senescence in some systems.

Keywords: ageing; life history; marine mammal; maternal effect; phenology; senescence; sex ratio.

Abstract

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