Scientists from the University of Washington discovered that female southern orcas from British Columbia were hunted worse than northern killer whales due to female matriarchal shortages; this may explain why the northern population is growing in numbers while the southern population is slowly dying. . Research published in the journal behavioral ecology.
Northern killer whales live in the northern waters of British Columbia (part of Canada), while southern killer whales live in waters further south. Most pregnancies in the Southern population end in miscarriage or death of the newborn. Now there are only 73 individuals left in the population.
At the same time, the population of killer whales living in the north of the region is constantly increasing. There are more than 300 northern killer whales today. The two populations are very similar: they live in similar conditions, eat the same food (salmon), but for some reason one dies while the other thrives.
Both northern and southern killer whales are united in clans controlled by females past reproductive age. They even help adult sons hunt.
Scientists observed killer whales from 2009 to 2014. They found that northern adult males with a viviparous mother hunted less than southerners. Perhaps this is because the northern men were helped by their mothers. In general, males living in the south catch 152% more salmon per hour than females. For the growing northern population, this trend has reversed; females catch 55% more salmon per hour than males.
This may mean that southern females receive less prey: they are eaten by males. The study found not a single case in which a southern female killer whale, who recently gave birth to a calf, successfully obtained food for herself.
The scientists hope that additional observations will help shed light on why the behavior of the two populations differed and whether this was due to a lack of matriarchy in the south.