Gray seals live along some of the coldest coastlines in the North Atlantic, including regions of Canada where winter temperatures drop sharply, winds intensify, and coastal waters approach freezing. Despite these challenges, they continue to thrive thanks to a combination of physical adaptations and behavioural strategies that evolved over thousands of years.
Their ability to stay warm, conserve energy, raise young in bitter weather and find food under shifting ice shows how well suited they are to life in extreme conditions. Many of their survival tools are not immediately visible, but each plays a key role.
Thick blubber keeps them insulated during long dives, strong lungs and a slow diving heart rate help them conserve oxygen, and their winter pupping season provides young seals with a safer start in areas where predators are less active.
Taken together, these traits explain why gray seals remain one of Canada’s most resilient marine mammals even when winter pushes conditions to their limits.
This article is for general knowledge only and is based on information from online sources. Research on marine mammals continues to evolve, and local conditions can change from year to year. Photos are for illustrative purposes only.
Thick Blubber Provides Powerful Insulation
Beneath the skin of every gray seal lies a substantial layer of blubber, and this dense, fatty tissue is one of the most important tools they have for winter survival. Blubber works as both insulation and an energy reserve, functioning much like a heavy parka that never comes off.
According to Fisheries and Oceans Canada, gray seal blubber can be several centimetres thick, which slows the loss of body heat even when the surrounding water hovers near freezing. This matters because water pulls heat from the body far faster than cold air does. Without this thermal barrier, seals would lose warmth too quickly to remain in icy waters for long periods.
Blubber also stores calories that seals rely on when food becomes more difficult to access. Winter storms, shifting ice, and longer dives can make hunting unpredictable, so having a built in energy supply helps them remain active even when conditions temporarily reduce feeding opportunities.
This stored energy becomes especially important for pregnant females and nursing mothers, who need consistent reserves to support their pups while still maintaining their own body heat.
They Give Birth On Ice And Frozen Beaches
Pupping season for many Canadian gray seals takes place in mid-winter, a timing that may seem surprising until you consider why the species evolved this strategy.
Mothers often choose pack ice, remote islands, or frozen shorelines as birthing sites because these environments limit access for predators and reduce disturbance from other animals. Cold, open spaces may appear harsh, but for seals they provide a relatively safe nursery that is difficult for threats such as coyotes, foxes, or large birds to reach.
Newborn pups are not immediately suited to the freezing ocean, so they spend their first few weeks entirely on land. During this time, they rely on a thick, woolly white coat called lanugo, which helps trap heat even when temperatures drop far below freezing. Researchers from the University of New Brunswick note that this fur acts as insulation until the pups gain enough blubber to enter the water.
During these critical early weeks, mothers produce extremely high-fat milk, among the richest of any mammal, which helps pups rapidly build the blubber layer they need. By the time they wean and take their first swim, they are better prepared to handle Canada’s frigid coastal waters.
They Slow Their Heart Rate During Dives
Gray seals are powerful and efficient divers, and one of their most remarkable adaptations is their ability to conserve oxygen and energy while underwater. When a seal begins a dive, its heart rate slows dramatically, sometimes dropping from around 60 beats per minute at the surface to fewer than 10 beats per minute during the deepest parts of the descent.
This natural response, known as the mammalian dive reflex, allows the seal to stretch limited oxygen supplies over several minutes. Studies published by the Journal of Experimental Biology show that this slowed heart rate works alongside other adaptations, such as rerouting blood flow to essential organs, to help the seal stay submerged longer.
In winter, this ability becomes especially important. Cold water accelerates heat loss, and seals must dive efficiently to avoid unnecessary exposure. A slower heart rate reduces energy spent on unnecessary movement, allowing them to search for fish across wider areas without overheating or burning through their energy reserves.
It also helps them reach winter aggregations of prey, which often shift to deeper waters as surface temperatures drop. By controlling their metabolism so precisely, gray seals can continue hunting even when the environment becomes challenging or unpredictable.
