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

• 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
• Other Authors: University of St Andrews. School of Biology, University of St Andrews. Centre for Research into Ecological & Environmental Modelling, University of St Andrews. Centre for Social Learning & Cognitive Evolution, University of St Andrews. Scottish Oceans Institute, University of St Andrews. Institute of Behavioural and Neural Sciences, University of St Andrews. School of Mathematics and Statistics, University of St Andrews. Centre for Energy Ethics, University of St Andrews. Office of the Principal, University of St Andrews. Sea Mammal Research Unit, University of St Andrews. Statistics, University of St Andrews. Marine Alliance for Science & Technology Scotland
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2024
• Subjects: Bayesian state-space model; Body size; Capital breeding; Eubalaena glacialis; Health; Length; QH301 Biology; DAS; MCC; QH301; North Atlantic
• Online Access: https://hdl.handle.net/10023/29389; https://doi.org/10.1098/rsos.240050

Funding: This work was supported by the Office of Naval Research (grant nos. N000142012697 and N000142112096) and the Strategic Environmental Research and Development Program (grant nos. RC20-1097, RC20-7188 and RC21-3091). Photogrammetry was supported by NOAA grant no. NA14OAR4320158 to Woods Hole Oceanographic Institution, and by NOAA's Southwest Fisheries Science Center. 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. Peer reviewed