Mammals
Hooded Seal
Cystophora cristata · also called hooded seals
Just four days after giving birth on the Arctic ice, a hooded seal mother prepares to leave her pup, already tripled in weight from a diet of some of the richest milk produced by any mammal on Earth, the shortest complete nursing period documented anywhere in the animal kingdom.
Overview
The hooded seal, Cystophora cristata, is a distinctive Arctic seal native to ice-covered waters across the North Atlantic and adjacent Arctic Ocean, migrating between specific breeding, moulting, and feeding areas. Its record-breaking four-day nursing period, exceptionally fat-rich milk, and males’ unusual inflatable nasal sac and red nostril membrane displays make it one of the more physically and reproductively extreme seal species found anywhere in the world.
A pup raised at record speed
Few mammals compress reproduction into as short a window as the hooded seal, whose pup goes from birth to fully weaned and independent of its mother’s milk in barely more time than it takes most other mammals to establish a feeding routine.
Status
Vulnerable and decreasing, present across suitable ice-covered habitat throughout the North Atlantic and adjacent Arctic Ocean, with declines linked to historical hunting, changing sea ice conditions, and shifting prey availability.
Hooded Seal: common questions
How short is the hooded seal's nursing period really?
This species weans its pup in just four days, the shortest nursing period documented in any mammal, an extraordinarily brief window during which the pup triples its birth weight almost entirely on the mother's extremely fat-rich milk before she departs to resume feeding herself.
What is the inflatable structure on a male hooded seal's head?
A male of this species has an inflatable nasal sac that expands into a balloon-like structure on top of the head, used alongside an additional bright red membrane inflated from one nostril, both serving as visual and vocal display structures during competitive encounters with rival males in the breeding season.
Why is the hooded seal's milk so unusually rich?
This species produces milk with an exceptionally high fat content, among the richest documented in any mammal, an adaptation that allows the pup to gain weight extremely rapidly during the unusually short four-day nursing period before the mother must return to foraging.
Why is the hooded seal considered Vulnerable?
This species has declined in parts of its range due to a combination of historical commercial hunting, changes in sea ice conditions affecting breeding success, and shifts in prey availability, pressures that together have kept the species classified as Vulnerable despite its continued presence across suitable Arctic and North Atlantic habitat.