Richard Collins: 'Immortality' for mothers who give sons a head start in life
University Reproductive Post / Travelling Center Research An Credit Exeter With His For Ellifrit Mother David Adult Of Male / Whale
There’s a spot in my heart which no cailín may own...
Despite its name and fearsome reputation, the male killer-whale is a Mammy’s boy. He stays with mother throughout his life, making occasional excursions for one-night-stands with females in other pods. It’s a mean strategy: the seduced female’s pod must raise the resulting calf.
Meanwhile, Casanova’s doting parent, if she has not been impregnated by a visiting male herself, dances attendance on her favourite son, keeping rivals at bay and sharing food with him. She hopes that a head-start in life will make him a major stud. Half of his genes are hers. If he manages to sire many offspring, she is assured of 'immortality'.
Humans and killer whale females are among the half-dozen species known to live on after the menopause. The other four species are, like the killer, toothed whales.
There has been much head-scratching among zoologists as to why these creatures survive ‘ovarian retirement’. A wild animal, which is no longer able to breed, is a drain on resources. There are no free lunches, pensions, golden handshakes, or retirement schemes, for animals who are ‘past it’. Nature is cruel — a stag losing his harem to a rival won’t last long. Nor will a silverback ousted in a coup. Eels die after mating. So do Pacific salmon, male honeybees and many other insects.
With humans, the reasons are clear: grannies and grandads remain useful in their ‘golden years’. ‘Oldies’, the community’s filing cabinets, have wisdom, the fruit of long experience. ‘Knowing where the bodies are buried’ can be crucial to a creature’s fortunes during lean times and unexpected challenges.
The killer whale matriarch may live for more than two decades following her last parenthood. In her dotage, she protects her favourite son, keeping him out of harm’s way and reducing his risk of injury fighting with rivals. She is no feminist, alas: no special favours are bestowed on her daughters.
But the killer whale’s North-Korean-style society is a closed book. How do we discover what goes on behind closed doors in the depths of the sea?
Charli Grimes and colleagues at the University of Exeter have found a way. They use ‘tooth-rake marks’. The killer whale is the sea’s apex predator — no other creature, not even the great white shark, will attack a healthy adult one. The skin is exceedingly tough: only the tooth of another killer whale is likely to penetrate it. His scars are a mutilé de guerre’s CV. Marks on a whale’s skin indicate a warlike past. But how are researchers to gauge the extent of such scarring?
The Centre for Whale Research in the United States has been monitoring whale pods since 1976, using photographs to identify individuals. It has created a photographic who’s who of whales. Grimes and his team used the photos to gauge the extent of scarring on individuals and correlated it with their mothers’ breeding status. They found that males protected by menopausal mothers had 34% fewer scars than those whose mothers were still fertile.
God bless you and keep you, mother mo chroi!