The relationship between body condition, fecundity, and mortality in Northern Resident killer whales
Rowley A, Kay S, Mikus M, Vergara V, Visona-Kelly B, Barrett-Lennard L 2025. The relationship between body condition, fecundity, and mortality in Northern Resident killer whales. Raincoast Conservation Foundation. https://doi.org/10.70766/01.0775
Funding for the work presented in this report was provided by a 2023 grant from Fisheries and Oceans Canada. The full time series of body condition data collected between 2014 and 2024 was facilitated by funders including Fisheries and Oceans Canada, the National Fish and WIldlife Foundation, Seaworld & Busch Gardens Conservation Fund, LNG Canada, the Ocean Wise Killer Whale Adoption Program, Mitacs, the Audain Foundation and the Vancouver Foundation.
We thank Holly Fearnbach and John Durban for their work developing the eye patch ratio metric of body condition and data collection in the early years of the study. We thank Gary Sutton and Dylan Smyth for data collection and data curation. Thanks also to Drew Grav-Graham and the Achiever crew. Thank you to Peter Thompson and Isaac Rankin for statistical advice. Cover image by Raincoast Conservation Foundation, SARA permit XMMS-2-2022.
Introduction
Since 2014, a team of scientists from the Raincoast Conservation Foundation (2022-2024), Ocean Wise Conservation Association (2014-2022), NOAA (2014-2017) and SR3 (2017) have collected aerial photographs of Northern Resident killer whales (NRKW) in the waters around northeastern Vancouver Island annually (August-September) in order to monitor body condition. In 2019, 2022, 2023 and 2024, additional field work was conducted on the Central Coast of British Columbia in June and/or July. Body condition was assessed from aerial photographs by calculating ‘eye patch ratios’ (Fearnbach et al. 2019), a measure of fatness behind the head calculated by dividing the distance between the eye patches at ¾ of their length by the distance between the anterior tips (Figure 1).
In this report, we first detail findings from field operations to assess NRKW body condition in 2023 and 2024. We then use the entire body condition time series from 2014 to 2024 to examine the relationships between body condition, survival and reproductive success in this population.
References
Fearnbach H, Durban JW, Barrett‐Lennard LG, Ellifrit DK, Balcomb KC. 2019. Evaluating the power of photogrammetry for monitoring killer whale body condition. Marine Mammal Science. 36(1):359–364. doi:https://doi.org/10.1111/mms.12642.
Ford JKB, Ellis G. 2006. Selective foraging by fish-eating killer whales Orcinus orca in British Columbia. Marine Ecology Progress Series. 316:185–199. doi:https://doi.org/10.3354/meps316185.
Kay S, Rowley, A, Visona-Kelly, B, Barrett-Lennard, L, Thompson, P, Sutton, G, Fearnbach, H, Durban, J., Darimont, C. “Cost of Maternal Care Revealed Through Body Condition in Northern Resident Killer Whales” [manuscript in preparation]
Raverty S, St. Leger J, Noren DP, Burek Huntington K, Rotstein DS, Gulland FMD, Ford JKB, Hanson MB, Lambourn DM, Huggins J, et al. 2020. Pathology findings and correlation with body condition index in stranded killer whales (Orcinus orca) in the northeastern Pacific and Hawaii from 2004 to 2013. PLOS ONE. 15(12):e0242505. doi:https://doi.org/10.1371/journal.pone.0242505.
Wright BM, Stredulinsky EH, Ellis GM, Ford JKB. 2016. Kin-directed food sharing promotes lifetime natal philopatry of both sexes in a population of fish-eating killer whales, Orcinus orca. Animal Behaviour. 115:81–95. doi:https://doi.org/10.1016/j.anbehav.2016.02.025.
Rowley A, Kay S, Mikus M, Vergara V, Visona-Kelly B, Barrett-Lennard L. 2025. The relationship between body condition, fecundity, and mortality in Northern Resident killer whales. Raincoast Conservation Foundation. https://doi.org/10.70766/01.0775