NEW PUBLICATION LINKS BODY CONDITION TO PREY AVAILABILITY AND SURVIVAL FOR ENDANGERED SOUTHERN RESIDENT KILLER WHALES
A research paper titled “Survival of the Fattest: Linking body condition to prey availability and survivorship of killer whales” was recently published in Ecosphere, a journal of the Ecological Society of America (https://doi.org/10.1002/ecs2.3660). This collaborative paper used drone-derived photogrammetry data collected by SR3’s Dr. Holly Fearnbach, SEA’s Dr. John Durban and colleagues since 2008 in an analysis led by Dr. Josh Stewart from NOAA’s Southwest Fisheries Science Center. The paper evaluated the link between our non-invasive measurements of body condition and the subsequent mortality probability for Southern Residents, specifically revealing that whales in poor condition had a 2-3 times higher chance of dying than whales in more robust condition. This demonstrates huge potential for using our body condition metrics as early warning indicators of individual and population health, providing managers with options for implementing enhanced recovery strategies to hopefully prevent deaths rather than making decisions in response to them. This is very important for helping to conserve and recover this small and endangered population.
We were also able to link changes in body condition to the abundance of specific salmon stocks. Notably, there was a significant correlation between the condition of J pod whales in September and the abundance of Chinook salmon returning to the Fraser River in the preceding summer months, whereas L pod body condition correlated with the abundance of Chinook returning to Puget Sound. K pod whales changed little in body condition during the study and did not correlate with salmon abundance from any specific area or tributary, likely indicating that K pod rely on a variety of salmon stocks for their summer diet. These new data help to identify priority salmon populations that are important for Southern Resident condition and population health, and help further focus recovery actions. Identifying specific salmon stocks that are important for Southern Residents has been challenging in the past, but our results show the utility of using our high-resolution body condition data to identify important prey populations. SR3 and colleagues are now extending our photogrammetry monitoring to detect changes in whale in body condition and identity salmon populations that are important to the Southern Residents throughout the year.
Aerial image of J41, an adult female Southern Resident killer whale, successfully foraging alongside her juvenile offspring J51. Image collected by Holly Fearnbach and John Durban, from SR3 and NOAA, respectively, using an unmanned octocopter that was flown >100ft above the whales under NMFS permit #19091.