There are a plethora of interesting facts about Orcas (Orcinus orca), better known as Killer Whales, that make them so intriguing to humans. One fascinating thing about Orcas is the feeding preferences seen between resident and transit ecotypes. In the eastern North Pacific Resident orcas feed primarily on salmon species, while transient orcas in the same area preferentially feed on marine mammals. These feedings strategies can present particular problems, specifically with respect to their prey availability. Some collaborative fundamental research originating from academics and government researchers in Washington is shedding light on the reproductive efforts of Souther Resident Killer Whales (SRKW) living in the inshore waters of Washington State and British Columbia, which primarily feed upon endangered Chinook salmon.
Wasser et al's 2017 study assessed the fecundity of this group from 2008 to 2014. They measured the breakdown products of key physiological and sex hormones in orca fecal samples (where they used orca scat detecting dogs). They also used orca DNA extracted from the scat to determine sex, family pod and identity of the individual responsible for the leavings. They discovered up to 69% of all detectable pregnancies were unsuccessful; of these, up to 33% failed relatively late in gestation or immediately post-partum, when the cost is especially high. Low availability of Chinook salmon appears to be an important stressor among these fish-eating whales as well as a significant cause of late pregnancy failure, including unobserved perinatal loss.
This has very important implications as to how we must manage these endangered mammals. Yes it is all well and good that we protect these majestic whales, but to do this we first have to start with the salmon, which is a completely different problem all in itself for the salmonid species of the Pacific Northwest which continue to reduced return rates.
Please see the free full tex
t of this article:
Wasser SK, Lundin JI, Ayres K, Seely E, Giles D, Balcomb K, et al. (2017) Population growth is limited by nutritional impacts on pregnancy success in endangered Southern Resident killer whales (Orcinus orca). PLoS ONE 12(6): e0179824. https://doi.org/10.1371/journal.pone.0179824
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0179824
Learn a bit about the scat detecting dogs
http://www.washington.edu/news/2017/06/29/study-shows-high-pregnancy-failure-in-southern-resident-killer-whales-links-to-nutritional-stress-and-low-salmon-abundance/
