The Whale Pages: Change in Habitat Use by Southern Resident Killer Whales
Every year for the past 9 years the Center has written a weekly segment in the local paper, the San Jun Journal, in the month of August. These informational articles are called "The Whale Pages". Below is the second installment of the four part series.
When it comes to Southern Resident killer whales (SRKW), no single organization has more data than the Center for Whale Research (CWR). For more than 40 years, we have maintained sighting records and health assessments in the form of photographs and reports, not only from our own encounters but from the public and other researchers as well.
This type of long term consistent data on wild animals is extremely rare, and extremely valuable. Long term studies, like ours, can track changes in ways that short term studies cannot. For example, the shift in the amount of time the SRKWs are spending in the core summer habitat area of the Salish Sea, would be merely anecdotal if not for the years and years of information we have about how the whales use this area.
Over the course of the past five years the Southern Resident killer whale community of J, K, and L pods has become increasingly fractured. Evidence suggests that a lack of salmon in their core summer habitat is causing them to have to split up to find enough food. This fragmentation of the pods is worrisome. Our research shows that orcas are highly social animals, but we don’t yet fully understand just how important social cohesion is to the overall health and recovery of this highly endangered population of whales.
In 2013, when even J pod (the most resident of the resident killer whales) was conspicuously absent from their core summer habitat for days and weeks at a time, we were able to confirm that there was a significant shift occurring. Not only were the whales absent for the majority of that summer, but the way they behaved while they were here had already began to change. As many observers have since noticed, the whales are spending more and more time fragmenting into small, spread out groups. The 2017 whale season is shaping up to be as bad or worse than 2013.
It is important to continue documenting these changes so that we can compare with the baseline data and look for correlations. With our 4 decades of data, we can begin to unravel the cause of these changes. Unsurprisingly, the decline in the abundance of Chinook salmon, the whale’s main food source, is a key factor. In particular, the low numbers of Fraser River Chinook returning each year is a severe cause for concern.
On the South side of the US/CA border, the importance of the Fraser River Chinook salmon frequently gets left out of the conversation. This is despite the fact that, historically, fish from this run are the main source of food for the whales in the spring and summer. But, as the number of fish returning to the Fraser during the spring run steadily decreases, so too does the presence of resident
killer whales in our waters.
It is clear that our “resident” killer whales are steadily decreasing their presence in what was, historically, their core habitat. Correlations with salmon returns, along with our studies of killer whale feeding habits, make it clear that this absence is due to a need to search for food in other areas. Until Fraser River Chinook runs improve, it is likely that we will continue to see a decline in SRKW presence.