Population growth is limited by nutrition and toxin impacts on pregnancy success in endangered Southern Resident Killer Whales

The Southern Resident killer whale population (Orcinus orca) was listed as endangered in 2005. Population growth is constrained by low offspring production for the number of reproductive females in the population. We are examining nutritional and toxicant impacts on offspring production in these whales through noninvasive endocrine and toxicant measures acquired from their scat, located by detection dogs. These methods enabled us to obtain a relatively large sample size to assess pregnancy occurrence and failure as well as temporal impacts on pregnancy success from poor nutrition, toxicants and other stressors. Up to two thirds of all pregnancies detected using reproductive hormone metrics miscarried; one third of these miscarriages likely occurred relatively late in gestation when the cost is especially high. Nutritional stress was shown to be an important contributor to pregnancy failure in these fish-eating whales that heavily rely on threatened or endangered Chinook salmon. Elevated lipid metabolism under nutritional stress increases levels and toxic potential of persistent organic pollutants, which may add to these cumulative impacts. Results point to the importance of promoting salmon recovery to enhance population growth of these whales. The physiologic and toxicant measures used in this study can also be used to monitor the success of management actions, promoting adaptive management of this important apex predator to the Pacific Northwest