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The Far Ranging Elephant Seal

Another singularly incredible and ruthlessly exploited species, the Northern Elephant Seal has returned from the brink of extinction, increasing its population steadily for the last 125 years. From as few as 20 individuals in the late 1890s, as many as 150,000 seals now occupy their historic territory in the eastern Pacific ocean. Migratory, Northern Elephant Seal travel as far north as Alaska and British Columbia, as far south as northern Mexico, and as far west as Hawaii before returning twice a year to islands and beaches on and off the Pacific coast. In the summer, they come to molt; in the winter, bulls come to battle for supremacy and to breed with female seals, which have come to bear their pups from the previous year’s breeding season.

After an eleven-month gestation, female seals give birth to a single pup. The females nurse the often boisterous pups, providing them milk with the highest fat content of any mammalian species on the planet. The pups quickly put on weight. And they need to. The females have fasted since shortly after arriving at the birthing area, and they return to sea about two months after giving birth. When the weaners get up the courage to head out to sea themselves, they don’t have to worry about seal hunters, but they do have other issues to face.

Because of unusually high water temperatures that have persisted in the Pacific ocean for several years, the marine organisms (including anchovies, sardines, and mackerel) on which sea lions, harbor seals, elephant seals, fur seals, and others depend for sustenance can no longer be found in abundance. This has forced female seals to travel further to sustain themselves and has driven hungry pups to leave their rookeries to hunt for food on their own before they have the strength or skills to do so successfully. Many become so malnourished in the attempt that they perish. The lucky ones are rescued when they wash up on a nearby shore. In recent years, organizations like the Marine Mammal Center have rescued, tended, fed, and released record numbers of sick, injured, and emaciated seal pups of various species.

In the case of Northern Elephant Seal pups, some venture into the surf and get pulled out to sea by the overly strong currents or get washed out to sea by strong storms. Some leave the beach only to fall prey to Great White and other sharks patrolling the Pacific coastline. Others simply aren’t strong enough to prosper after leaving their birthing colonies. Either they tarry too long on the beach and waste the stores of fat they had built up, or their mothers, weakened by the lack of food before they arrived, could not provide enough high-quality milk to sustain their pups until they could successfully hunt for themselves. The latter is a phenomenon—linked to climate change—that has also been reported by researchers studying the Southern Elephant Seal, a related species that frequents the Antarctic or Southern Ocean.

If the unusually persistent high temperature of the Pacific Ocean results from climate change, as many scientists believe, weakened mothers and underfed pups will not be the only negative effects that climate change will have on the Northern Elephant Seal. Some elephant seal colonies have seen higher pup mortality rates in recent years. Climate change has also been linked to a higher percentage of male births among elephant seal—both northern and southern species. Should this persist, the population of the species will almost certainly diminish with fewer females available to give birth to new pups.

More powerful storm systems and stronger El Niño events are also likely to cause increased erosion on the off-shore islands and coastal enclaves that elephant seal have been using for birthing colonies in the winter and safe havens in the summer (when they experience catastrophic molts and cannot venture into the ocean). And as sea levels rise over the next fifty to one hundred years as a direct result of climate change, many of the islands and coastal beaches that now provide habitat to the elephant seal will cease to exist, inundated by encroaching ocean waters.

Thanks to the fossil record, we can trace the lineage of the elephant seal back to the Miocene era, as many as 23 million years ago. To secure blubber as fuel for lamps, we nearly annihilated the elephant seal (and many whale species) in a little more than a hundred years. And our stubborn love affair with coal, oil, and gas, may cause the ultimate extinction of the elephant seal and other marine and terrestrial species in the next hundred years. If not sooner.

References:

Climate Change and Seal Survival: Evidence for Environmentally Mediated Changes in Elephant Seal, Mirounga leonina, Pup Survival
Climate changes put the freeze on elephant seal births
Elephant Seals and Climate Change
Elephant seals shed light on climate changes
Elephant Seal Births Are Up, but the Pups Struggle to Survive
Elephant Seal Tracking Reveals Hidden Lives of Deep-diving Animals
Elephant Seals
Marine Mammal Center’s Elephant Seal Care Picks Up On Local Beaches
Northern Elephant Seals: A Dramatic Conservation Success
The Northern Elephant Seal: A Life of Singular Extremes
North Pacific Climate Mediates Offspring Sex Ratio in Northern Elephant Seals
Seals and Their Race against Climate Change
Unusual Ocean Conditions Continue to Cause Record Strandings
Warming Ocean Temperatures May Reduce the Survival Rate of Elephant Seals
Warming Waters Bias Elephant Seal Sex Ratios
World Expert on Seals Discusses their Fate in the Context of Climate Change