Every year, Salish Sea residents eagerly await the return of the southern resident killer whales to their Summer feeding grounds. In late June, the orca community’s three extended family groups or pods were spotted off the coast of Vancouver Island. This year a total of 73 orcas—made up of J, K, and L pods—have returned to a quieter ocean due to the COVID-19 shutdown, and recent sightings suggest that a member of J pod is pregnant.
To find out more about these endangered social mammals and their future, we spoke to Ocean Networks Canada’s junior staff Scientist Kristen Kanes, who specializes in passive acoustics research methods to study at-risk cetaceans.
Question (Q): How many different kinds of killer whales are there in British Columbia?
Answer (A): British Columbia is home to 3 different ecotypes of orca or killer whales which are culturally, morphologically, and genetically distinct: residents, transients—also known as Bigg’s, and offshores. These ecotypes are also ecologically distinct, meaning they occupy different ecological niches. Resident orcas only eat fish—primarily Chinook salmon; Bigg’s orcas eat marine mammals; and offshore orcas have a broad diet that notably includes sharks.
Within the resident ecotype, there are two different communities: the northern residents and the southern residents, two separate populations that do not interbreed and although their habitats overlap they are rarely seen in the same region at the same time.
While they are culturally distinct from each other, many aspects of the lives of northern and southern residents are similar—they live in tight-knit, social, matrilineal families and are dependent on salmon for food. However they have completely different call repertoires, similar to languages, so they are unlikely to understand each other.
Q: Why do southern resident killer whales return to the Salish Sea every year?
A: Starting in the Spring and continuing through Summer and Fall, salmon pass through the coastal waters of the Salish Sea on their migrations from the open Pacific Ocean to spawn in the rivers where they were born. This makes Summer a particularly good time for orcas to hunt Chinook salmon and socialize in the Salish Sea.
Q: What are the indicators of the southern resident orcas’ return to the Salish Sea?
A: The southern residents have a distinctive call repertoire and each individual orca looks unique to the practiced eye, so they are not tracked by satellite the way some other animals are. We know the southern residents are back when an observer spots them on the water, or they are heard on one of the several hydrophone networks deployed in the Salish Sea. Currently ONC gathers data from 16 hydrophones, including 6 in the Salish Sea. Other organizations listening for orcas in the Salish Sea include the Saturna Island Marine Research and Education Society (SIMRES) and OrcaSound, which livestreams their data.
Q: How long do they spend in the Salish Sea each year?
A: In the past, the southern residents typically spend nearly 200 days a year in the Salish Sea, primarily between May and October. During the rest of the year the southern residents can be found anywhere from southern Alaska to central California, though they continue to visit the Salish Sea periodically throughout the year.
In recent years they have been spending less time in their Summer hunting grounds and they returned late this year. Photogrammetry—which uses photographic images and calculations to make reliable measurements—has revealed that some of these orcas are malnourished and it is widely believed that they spend less time in the Salish Sea due to decreased foraging success in the region. Dwindling Chinook salmon returns are likely the cause, along with anthropogenic underwater noise. Ship noise and other human-caused sounds mask the echolocation clicks orcas use to search for food, which can make their prey more challenging to find. Orcas depend on sound to “see”, so imagine trying to navigate in a thick fog.
Q: New research shows that the COVID-19 slow-down has resulted in a quieter ocean. Is research being done on the impact that hushed seas might have on the southern resident killer whales?
A: Researchers from several Canadian and United States organizations are working together to study the southern residents during these strange times and watch for behaviour changes now and in the coming years. However, if this quieter time does improve things for the orcas we likely won’t see the effects for a while. First, they need to find food. Once they’re fed and healthy, we may start to see more robust body conditions in photogrammetry studies or decreased stress hormones in their fecal samples. The real test of impact will be if their birth rates and survivorship improve over the next few years. So we won’t know how changes in anthropogenic noise has impacted them on a population level for some time.
Q: Recent sightings suggest that J-35 is pregnant. When is she due to give birth?
A: Orca gestation is 15-18 months, so it could be some time before 22-year-old J-35 (Tahlequah) gives birth. It’s challenging to know how many months pregnant she is from an aerial photo, so we don’t know exactly when she's due, besides assuming that she's been pregnant for some months already because she's showing.
In 2018, Tahlequah made headlines around the world for her display of grief after her calf died shortly after birth. Resident orcas have been known to support their deceased calves at the surface and transport them as they travel for a few hours to a few days after death, but Tahlequah carried her calf for an unprecedented 17 days of mourning.
Reproductive success in the southern resident community has been low in recent years: over the last two decades only about 25% of newborns have survived. Scientists suspect the low reproductive success rate is tied to reduced foraging success due to low Chinook salmon returns. This is compounded by the effects of anthropogenic noise and organic pollutants that are very concentrated in apex predators like orcas and can have toxic effects if released into the blood stream, such as when fat stores are drawn on during times of starvation.
I hope that the three new pregnancies spotted through continuing photogrammetry studies will be a turning point for these orcas, but the population trend of recent history is hard to ignore and these pregnancies will only be successful if the orcas can find enough food. This unprecedented time of hushed seas may be exactly what the orcas need to make it easier to find food, but only if there’s food here to be found.
Listen to more orca sounds here.