The ocean covers a large portion of the planet's surface and is home to an incredible number of species, including orcas. In recent years, scientists have learned a great deal about these cetaceans, yet they continue to amaze us, reports PHYS.org.
One of the most mysterious groups of orcas is the population of southern resident killer whales in the Pacific Ocean. For years, researchers have observed a relentless decline in their numbers, yet the reasons behind this phenomenon remain unclear. It was previously believed that the decrease in the southern residents' population was due to insufficient access to food, but new research suggests otherwise.
In a new study, a pair of marine mammal scientists from the University of British Columbia discovered that the claim that the population of southern resident killer whales is sharply declining due to lack of access to salmon is incorrect.
The study's authors, Burak Saygili and Andrew Trites, stated that they consulted with recreational fishermen and whale-watching teams to gain more insight into the orcas' access to prey. Earlier studies indicated that orcas are facing challenges, as their population is not only declining but also the number of offspring is decreasing. Unfortunately, no one still knows why.
It is worth noting that the southern resident killer whales are a population that inhabits the coastal waters of North America, from California to British Columbia, as well as parts of the Salish Sea. The latest census indicates that there are only 73 orcas currently residing in the ocean, living in three pods.
It is known that during the warm months, orcas swim north and then return south with the onset of winter. Observations also show that the whales are struggling for survival. Unfortunately, the results of the new study did not clarify the situation but rather exacerbated it: researchers found that seals, other whale species, and marine porpoises and lions in the region are thriving, but not the orcas.
Previously, scientists suspected that the cetaceans simply lacked access to salmon, which significantly complicates their lives since it is their primary food source. However, recreational fishermen, also seeking salmon, report no issues catching it and have observed southern residents doing the same. Additionally, whale-watching teams informed researchers that they regularly see endangered orcas swimming among schools of salmon.
As a result, scientists proposed that the orcas are likely encountering difficulties in catching salmon. Moreover, they also suggested that this issue may be related to the noise in the ocean created by boats. The study authors note that there is significantly more marine traffic in the area where they live compared to regions further north, where northern orcas thrive.
Furthermore, it is suggested that whales may experience feeding challenges at different times of the year: while they can obtain enough food in the summer, they struggle in the spring.