J pod in Haro Strait, 7/20/2018. Photo by Stephen Rink
Transient pods are typically smaller than resident pods. Transients are also less vocal, and tend to hunt quietly. Unlike fish, mammals have excellent hearing, making it essential for transient orcas to travel in quiet and stealthy groups. Transients exhibit the same behaviors as other orcas and cetaceans, including spyhopping, breaching, porpoising, foraging, resting and lob tailing.
Overall, transient orca population numbers appear to be holding steady. However, one particular group of transients living in the Gulf of Alaska, the AT1 group, is listed as depleted under the Marine Mammal Protection Act. The AT1 groups was in Prince William Sound during the Exxon Valdez oil spill. Since then, the pod has shrunk from 22 individuals to 7, a decline that is attributed to the spill and its impacts.
West Coast transient orcas are highly contaminated with PCBs and other toxins. Since they eat marine mammals, they ingest the toxins that are present in their prey. They have been found to be one of the most contaminated cetacean populations in the world.