Less than a decade ago, very little was known about where Southern Resident killer whales go when they leave Puget Sound in the winter. Since then, NWFSC scientists and collaborators have learned a lot about the winter migration and habitat use of these endangered whales using satellite-linked tags and during surveys at sea.
From 2012-2016, satellite tags were deployed on a total of 8 Southern Resident killer whales. Even with this small number of tags, scientists gained vast amounts of information about the whales’ presence and movement patterns, which indicated the specific areas that are particularly important to the whales.
The satellite tag data also supplemented other studies to learn more about the whales’ coastal range, behavior, winter diet, and body condition than could be gathered from opportunistic sightings alone, such as from NOAA ship surveys and the coastal sighting network of citizen scientists, research partners, and others.
The information from a tagged whale from K pod, for example, revealed how just how far south the whales travelled, where they spent more time foraging, and how far off the continental shelf they travelled compared to locations where they stuck closer to the coast. Scientists learned that the longest of K pod’s round trips to northern California and back was completed in about 3 weeks.
In addition to collected data from the remote tags, researchers aboard a NOAA ship were able to follow tagged whales and its associated pod, as much as weather permitted during winter’s rough seas. These scientists collected multiple fecal and prey fragment samples during such surveys to help understand the whales’ coastal diet. Southern Residents were observed feeding on salmon on numerous occasions, answering a long-standing mystery (at the time) on what these whales primarily eat during the winter.
Following tagged whales and their pod at sea also gave the scientists an opportunity to improve tracking methods using the whales’ stereotypic calls and echolocation clicks, which were detected on a towed hydrophone array and sonobuoys. This technology made it possible to track killer whales during conditions that preclude visual monitoring, such as at night.
Scientists were able to observe how the whales utilize their habitat during the winter and collect related ecosystem data such as bird counts, zooplankton collections, and oceanographic information. These data provided key information that can inform designations of critical habitat for these endangered animals. Scientists confirmed that the California Current ecosystem likely provides important winter foraging habitat for not only killer whales, but also for other marine wildlife as well.
Scientists following a tagged whale and their associated pod were also able to collect tissue biopsies to yield information on the level of contaminants and their genetic stock structure (i.e., family relationships). Small amounts of skin and blubber biopsy samples from Southern Residents and offshore whales helped the researchers measure the health of the whales and make inferences about their diet.
NOAA Fisheries ended satellite tagging studies of the Southern Residents following the death of a tagged whale in 2016 from a fungal infection that may have been associated with the tag deployment. We continue to study the seasonal occurrence using non-invasive methods, primarily through the deployment of autonomous passive acoustic recorders at key locations identified from the satellite tagging data.