Killer whale mothers ‘pay high price’ for raising sons, say researchers

Raising sons is an exhausting experience that leaves killer whale mothers less likely to produce more offspring, a new study suggests. According to the research, each living son cut a mother’s annual likelihood of successful breeding – a calf surviving to the age of one – by about half. Furthermore, the effect continued as the sons grew older, indicating they were a lifelong burden on their mothers, the scientists said.