Data spanning nearly half a century shows that endangered southern resident killer whales are spending less time in inland waters, whereas their larger cousins, Bigg鈥檚 killer whales, are increasingly present in Puget Sound.
The National Oceanic and Atmospheric Administration southern resident killer whales as endangered in 2005 after rapid population decline in the late 1990s. Now, , split into three pods: J, K and L. Bigg鈥檚 鈥� sometimes referred to as transients 鈥� are more common, but difficult to count because they travel in smaller groups over wider ranges.
Looking at data from 鈥檚 Sightings Archive between 1978 and 2022, 乱伦社区 researchers modeled migratory trends based on observations from researchers, recreational boaters and whale watchers. They found that K and L pods are visiting Puget Sound less often, but the J pod remains well represented. The data on Bigg鈥檚 corroborates recent results showing a steady increase in inland waters.
The results in PLOS One.
鈥淲e do see increasing transient presence over time, but we don鈥檛 see a definitive decline or overall increase for the southern residents. Their presence here is much more variable,鈥� said lead author , a UW postdoctoral researcher of marine and environmental affairs.
Key behavioral and subtle physical differences . The southern residents eat salmon, while Bigg鈥檚 prey on seals, porpoises and other marine mammals. Seals and sea lions rebounded in Washington after the Mammal Protection Act, which may have drawn Bigg鈥檚 killer whales to inland waters, but that doesn鈥檛 explain the changing distribution of southern residents.
Because southern residents are organized into tight matriarchal societies led by female elders, researchers believe that social cues may play an important role.
鈥淒oes J pod know something that K and L don鈥檛? Or vice versa? We like to think about which pods have really old grandmas left and who’s teaching them where to go,鈥� said co-author , a marine mammal specialist at the National Oceanic and Atmospheric Administration (NOAA), West Coast Regional office.
Policies to protect southern residents typically apply to all pods. With K and L spending more time in coastal waters, NOAA for southern residents in 2021 to include 16,000 square miles of marine waters between the U.S. and Canada border and Point Sur, California.
Measures like the , which encourages commercial ships to slow down where whales are present, aim to mitigate the impact of noise. Boats are also of the southern residents.
Indications of changing habitat have prompted some to question the need for such regulations in Puget Sound, but these results underscore their continued importance.
鈥淓ven though we鈥檙e seeing less of K and L pods, we still have to think about how our actions impact J pod. They鈥檙e still hanging around,鈥� Koehn said.
The study also notes that southern residents and Bigg鈥檚 are sharing habitat more often, though it isn鈥檛 clear whether they mingle or avoid each other. This raises questions about their relationship and underscores the importance of accounting for both in management decisions.
鈥淗aving more transients around could be good for the southern residents, because they eat marine mammals that also eat salmon,鈥� Rand said.
But if the southern residents avoid the transients, their increased presence could be disruptive. Researchers are actively studying threats to the southern residents 鈥� including prey availability 鈥� to support the imperiled population.
This analysis wouldn鈥檛 have been possible without consistent contributions from citizen scientists. People who report whale sightings using apps like Whale Alert help researchers provide data to policymakers, which can be consequential for the whales.
鈥淭his study quantitatively shows things that people have been suspecting,鈥� Rand said. 鈥淭here are more transients here in Washington, but the southern resident鈥檚 story is a bit more complicated.鈥�
Additional co-authors include of the Whale Museum and of NOAA Fisheries Northwest Fisheries Science Center.
This study was funded by Washington Sea Grant, NOAA Fisheries West Coast and the Puget Sound Partnership.聽
For more information, contact Rand at zrand@uw.edu.