A killer whale in the Salish Sea is observed bugging a porpoise, a behavior that has long perplexed researchers. A study from Wild Orca and UC Davis SeaDoc Society investigates what might be behind it. Credit: Wild Orca
Researchers examine a perplexing behavior.
For numerous years, researchers have actually been puzzled by the behavior of Pacific Northwest fish-eating killer whales, who have actually been seen pestering and sometimes eliminating porpoises without eating them.
A research study just recently released in Marine Mammal Science, co-led by Deborah Giles of Wild Orca and Sarah Teman of the SeaDoc Society, a program of the UC Davis School of Veterinary Medicine, looked at more than 60 years of recorded interactions in between Southern Resident killer whales and cetaceans in the Salish Sea to much better comprehend why they show this habits.
Southern Resident killer whales are a threatened population, numbering only 75 individuals. Their survival is totally tied to the fortunes of Chinook salmon– likewise a threatened types. Without sufficient Chinook salmon, these whales are in danger of extinction.
“Its due to the fact that fish-eating killer whales have an entirely various ecology and culture from orcas that consume marine mammals– even though the 2 populations live in the very same waters. We must conclude that their interactions with porpoises serve a various purpose, but this function has only been speculation until now.”
Three possible explanations
While scientists have actually taped circumstances of Southern Resident killer whales taking part in porpoise harassment as early as 1962, reasons for this habits have long stayed a mystery. Giles, Teman, and a group of collaborators examined 78 documented occurrences of cetacean harassment from 1962 to 2020. The research study recommends 3 plausible descriptions:
” Mismothering behavior– also referred to as displaced epimeletic habits to researchers– may be due to their limited opportunities to take care of young,” Giles discussed. “Our research has actually shown that due to poor nutrition, almost 70% of Southern Resident killer whale pregnancies have resulted in miscarriages or calves that died immediately after birth.”
Salmon specialists
In spite of these interesting insights, Giles, Teman, and their partners acknowledge that the exact factor behind cetacean harassment might never ever be fully comprehended. What is clear, however, is that cetaceans are not a part of the Southern Resident killer whale diet. Southern Resident killer whale diets are extremely specialized for salmon, making the concept of eating cetaceans extremely unlikely.
” Killer whales are intelligent and extremely complicated animals. Its an amazing example of killer whale culture,” Teman states. “Still, we dont anticipate the Southern Resident killer whales to start eating porpoises.
This research study underscores the value of saving salmon populations in the Salish Sea and throughout the whales entire range. Keeping an appropriate supply of salmon is vital for the survival and wellness of Southern Resident killer whales and the general health of the Salish Sea ecosystem.
Affinity for play
This study comes at a time when a separate population of killer whales on the Iberian Peninsula has actually drawn global headings for engaging with, and on 3 occasions, sinking boats off the coast of Portugal and Spain. Eventually, the Southern Resident killer whales and the Iberian Peninsula orcas are 2 different populations with unique cultures. One thing the 2 may share is their affinity for play habits.
Recommendation: “Harassment and killing of cetaceans (” phocoenacide”) by fish-eating Southern Resident killer whales (Orcinus whale)” by Deborah A. Giles, Sarah J. Teman, Samuel Ellis, John K. B. Ford, Monika W. Shields, M. Bradley Hanson, Candice K. Emmons, Paul E. Cottrell, Robin W. Baird, Richard W. Osborne, Michael Weiss, David K. Ellifrit, Jennifer K. Olson, Jared R. Towers, Graeme Ellis, Dena Matkin, Courtney E. Smith, Stephen A. Raverty, Stephanie A. Norman and Joseph K. Gaydos, 28 September 2023, Marine Mammal Science.DOI: 10.1111/ mms.13073.
The research study was moneyed by Wild Orca and SeaDoc Society. Extra partners consist of the University of Exeter, Fisheries and Oceans Canada, Orca Behavior Institute, National Oceanic and Atmospheric Administration, Cascadia Research, The Whale Museum, Center for Whale Research, Ocean Research College Academy (ORCA) at Everett Community College, Bay Cetology, North Gulf Oceanic Society, George Mason University, and Marine-Med.
Social play: Porpoise harassment may be a kind of social play for killer whales. Like many smart species, these whales often participate in lively activities to bond, communicate, or simply enjoy themselves. This habits might benefit group coordination and teamwork.
Searching practice: Another hypothesis suggests that cetacean harassment might hone their salmon-hunting skills. Southern Resident killer whales might see porpoises as moving targets to practice their searching strategies, even if they do not plan to consume them.
Mismothering habits: This theory suggests that the whales might be trying to provide take care of porpoises they view as weaker or ill– a symptom of their natural inclination to assist others in their group. Women have actually been experienced carrying their departed calves and have been seen similarly carrying porpoises.
A killer whale in the Salish Sea is observed bothering a porpoise, a habits that has long perplexed scientists. While researchers have tape-recorded instances of Southern Resident killer whales engaging in porpoise harassment as early as 1962, reasons for this habits have long stayed a secret. Southern Resident killer whale diets are extremely specialized for salmon, making the concept of eating cetaceans extremely unlikely.
“Still, we dont anticipate the Southern Resident killer whales to begin eating porpoises. Eventually, the Southern Resident killer whales and the Iberian Peninsula whales are two various populations with unique cultures.