It is fairly well known that the three pods of killer whales that frequent Puget Sound are listed as endangered under the Endangered Species Act. It is also well known that their primary prey — chinook salmon — are listed as threatened.
It can’t be good that the whales are struggling to find enough to eat, but we are just beginning to learn that the situation could be dire for orca females who become pregnant and need to support a growing fetus during times of a food shortage.
Sam Wasser, a researcher known for figuring out an animal’s condition from fecal samples, recently reported that about two-thirds of all orca pregnancies end in miscarriage. And of those miscarriages, nearly one-third take place during the last stage of pregnancy — a dangerous situation for the pregnant female.
In a story published today in the Encyclopedia of Puget Sound, I report on Sam’s latest studies, along with other work by a team of biologists who are using unmanned aircraft (drones) to keep track of the physical condition of the Southern Resident orcas, including pregnant moms.
Sam’s latest study involves measuring hormones in killer whales, which can tell us a lot about a whale’s condition. The story of how hormones change under varying conditions is a little complicated, but I hope I was able to explain in my article how this works. When adding the effects of toxic chemicals that mimic hormones, we begin to understand the conditions that may be critical to the whales’ long-term survival or their ultimate extinction.
One longtime assumption, which may be shot down by the hormone studies, is that the whales’ most difficult time for food comes in winter, when salmon are generally scarce. These new studies by Sam and his colleagues suggest that the greatest problem comes in the spring, when the whales return to Puget Sound to discover that spring runs of chinook salmon can no longer be found — at least not in significant numbers.
The work with a drone carrying a high-resolution camera is providing precise measurements about the length and width of each killer whale. Pregnant females are especially interesting, and it will be important to document whether physical changes observed in the drone study can be correlated with hormonal changes seen in the other study.
“We’ve moved toward some great sophisticated technology,” Lynne Barre told me. “These great technologies combined can tell us more than any one method can … such as when and where food limitations might be affecting their health and reproduction.”
Lynne heads NOAA’s Protected Resources Division in Seattle and oversees recovery efforts for the endangered Southern Residents.
By the end of this year, NOAA is expected to release its five-year status report on the Southern Resident orcas. In addition to reporting on many new findings, the document will re-examine the risk of extinction for these killer whales and consider whether actions proposed to help them have been carried out.
Last year, the Southern Residents were listed among eight endangered species across the country that are headed for extinction unless recovery actions can be successful. The eight, selected in part because of their high profiles, are known as “Species in the Spotlight.” In February, five-year action plans were released for all eight species.
The plan called “Priority Actions for Southern Resident Killer Whales” (PDF 2 mb) focuses on three primary factors affecting the whales’ survival: a shortage of food, high levels of toxic chemicals and effects of vessels and noise. The concise 15-page document describes some of the work being carried out on behalf of the whales, although new ideas are coming forth all the time.