Decreasing body size is associated with reduced calving probability in critically endangered North Atlantic right whales

Body size is key to many life-history processes, including reproduction. Across species, climate change and other stressors have caused reductions in the body size to which animals can grow, called asymptotic size, with consequences for demography. A reduction in mean asymptotic length was documente...

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Bibliographic Details
Published in:Royal Society Open Science
Main Authors: Pirotta, Enrico, Tyack, Peter L., Durban, John W., Fearnbach, Holly, Hamilton, Philip, Harris, Catriona M, Knowlton, Amy, Kraus, Scott D., Miller, Carolyn, Moore, Michael, Pettis, Heather, Photopoulou, Theoni, Rolland, Rosalind, Schick, Robert, Thomas, Len
Format: Article in Journal/Newspaper
Language:English
Published: 2024
Subjects:
Bayesian state-space model
Body size
Capital breeding
Eubalaena glacialis
Health
Length
North Atlantic
Online Access:https://research-portal.st-andrews.ac.uk/en/researchoutput/decreasing-body-size-is-associated-with-reduced-calving-probability-in-critically-endangered-north-atlantic-right-whales(51ef5901-1230-466f-94c4-e78b4758c474).html
https://doi.org/10.1098/rsos.240050
https://research-repository.st-andrews.ac.uk/bitstream/10023/29389/1/Pirotta_2024_RSOS_Decreasing-body-size-calving_CC.pdf
Description
Summary:Body size is key to many life-history processes, including reproduction. Across species, climate change and other stressors have caused reductions in the body size to which animals can grow, called asymptotic size, with consequences for demography. A reduction in mean asymptotic length was documented for critically endangered North Atlantic right whales, in parallel with declines in health and vital rates resulting from human activities and environmental changes. Here, we tested whether smaller body size was associated with lower reproductive output, using a state-space model for individual health, survival and reproduction that quantifies the mechanistic links between these processes. Body size (as represented by the cube of length) was strongly associated with a female's calving probability at each reproductive opportunity. This relationship explained 62% of the variation in calving among reproductive females, along with their decreasing health (20%). The effects of decreasing mean body size on reproductive performance are another concerning indication of the worsening prospects for this species and many others affected by environmental change, requiring a focus of conservation and management interventions on improving conditions that affect reproduction as well as reducing mortality.

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