Claiming the broadest range of any of the world’s pinnipeds, the harbour seal is a familiar sight along many temperate Northern Hemisphere coastlines—and a popular snack item for behemoth marine predators like great white sharks, makos, and orcas.
When these relatively small (and, c’mon, full-on adorable) seals haul out on beaches, tidal mudflats, and nearshore rock stacks, though, they also fall under the radar of land-based meat-eaters. A new study published in Ecology shows that the yippy, yappy “songdog” of the Americas, the coyote, can be an effective predator of harbour seals—the smallest of them, at least.
The insights come from California’s North Coast, where, beginning back in 2016 and 2017, researchers surveying the harbour-seal colony at MacKerricher State Park noted carcasses of seal pups that had apparently been dragged away from the swash into the dunes. More dead pups in similar locations and conditions—most with skulls detached or entirely missing—turned up in the following years.
Tracks, scat, and bite marks suggestive of a canid attack all pointed to coyotes as the likely culprits—a suspicion confirmed last year when camera traps documented the songdogs in action tugging seal pups into the dunes. (And here’s our obligatory “circle-of-life” acknowledgment: Nobody likes seeing a baby seal taken out, but predation is just part of the game here on Planet Earth, and a reality of harbour-seal existence since forever. Also: Harbour seals can be plenty bitey themselves.)
Between the numerous carcasses and the camera-trap images, the study authors attribute the loss of some 55 seal pups at the MacKerricher rookery since 2016 to coyotes—and noted that a varied guild of scavengers, from rodents to gulls, ravens, and bald eagles, profited from the spoils.
The study suggests that seal pups less than a couple of weeks old—i.e., the littlest and most defenseless around—are the main ones these beachgoing coyotes target. That’s not particularly surprising, as harbour seals quickly grow heftier than your average western coyote (typically lighter and slighter than the burly “eastern coyote” or “coywolf” of eastern North America).
The researchers also cast their investigative nets more widely and collected documentation of coyote predation on seal pups in other stretches of California’s Pacific coast, home to one of more than a dozen harbour-seal stocks in the U.S. This included direct observations and photographs of coyotes ambushing pups in the Drakes Estero and Bolinas Lagoon rookeries farther south in Marin County. There, a single coyote or pair would rush upon “hauled-out harbour seals at the edge of exposed intertidal sandbars within coastal lagoons,” sending adults and pups alike scrambling for the water. Amid the chaos, coyotes would snatch pups onshore or even out in the shallows.
At MacKerricher State Park, coyotes appeared to preferentially feed on the energy-rich brain tissue of killed pups—hence the detached or missing skulls noted in the majority of seal carcasses found in dune vegetation. Interestingly, a similar zombie-ish taste has been noted in brown hyenas that prey on young Cape fur seals along Namibian and South African beaches, the favored brain material providing not only a high-calorie hit but also perhaps a moisture source for the shaggy “strandwolf” in such arid coastlands as the Namib Desert’s seashores.
Though coyotes undoubtedly primarily relish marine mammals in the form of carrion, they have been documented actively hunting them before, including harbour-seal pups farther north along the U.S. West Coast in Washington State as well as sea otters in Alaska. A particularly interesting case from Cape Cod, Massachusetts showed that the canids—at least eastern coyotes, anyway—can sometimes dispatch not just pups, but older and larger pinnipeds: In the winter of 2002, a coyote on that North Atlantic peninsula’s Nauset Beach was seen killing a good-sized yearling or adult harp seal larger than itself, being dragged about by its prey in the process. Analysis of the seal carcass showed the coyote had latched onto the throat of the seal and, in the only visible wound, “efficiently severed its jugular vein.”
Meanwhile, coyotes and brown hyenas aren’t the only terrestrial carnivores known to hunt seals and other marine life. The polar bear, of course, is best-known for this behaviour, but, then again, it’s as much a marine carnivore as a terrestrial one. But brown bears, too, for example, have been documented preying on harbour seals and sea otters in coastal Alaska. African lions of the Namib Desert pounce on hauled-out Cape fur seals (and also snack on such exotic fare as cormorants and flamingos, not to mention beached whales). Jaguars in multiple corners of the coastal Neotropics dispatch nesting sea turtles (as big as leatherbacks). And a recent study shows pumas in Patagonia can be highly effective predators of Magellanic penguins—and that local extirpation of the large cats by sheep farmers in the past may have allowed penguin colonies to establish on accessible mainland seashores once too vulnerable to puma predation.
Indeed, the spectre of raids by land-based predators has surely influenced the geography of pinniped (and seabird) rookeries and haul-outs since time immemorial. The new paper on seal-pup predation at MacKerricher State Park suggests harbour seals there may be increasingly favoring intertidal rocks over formerly more heavily used mainland beachfront as haul-outs, possibly (though not definitively) in response to the threat of coyotes.
And other canids besides the American songdog will set their sights on marine mammals. Arctic foxes burrow into the snowy sea-ice lairs of ringed seals to prey on pups, which have also been killed by red foxes. Although they are more liable to scavenge hyena-killed carcasses, Cape black-backed jackals in southern Africa sometimes try tackling live seal pups as well—a task made easier when groups of these small wild dogs cooperate, one throttling the pup while others tug at flippers and other parts of the body.
The grey wolf, biggest of all wild canids, will also look to the sea for dinner options. Wolves along the Pacific margin of northwestern North America—including the so-called “sea wolf” of southeastern Alaska and British Columbia’s temperate-rainforest coast—don’t just scavenge beachwrack, but also hunt harbour seals and sea otters. (The dearly departed lone wolf named “Staqeya” that pursued a solitary coastal living on the outskirts of the city of Victoria on British Columbia’s Vancouver Island some years back was an adept seal-hunter.)
Grey wolves boast quite the varied diet, but it’s hard to imagine it’s quite so diverse as that of its little cousin, the coyote (often known historically as the “brush wolf” or “prairie wolf”). A nose-to-tail omnivore, the songdog will happily nosh on papayas and mangoes in the Mexican tropics, wild grapes in the temperate deciduous forest, and cactus and mesquite beans in the North American deserts, alongside the dizzying range of carnivorous fare it’s wont to hunt or scavenge: from rodents, rabbits, waterfowl, and baby sea turtles up to deer, elk, and bison. And then there’s the dietary breadth exhibited by those coyotes that, famously (or infamously), thrive in urban environments: A study on such city-dwelling canids in southern California showed ornamental fruits, garbage, and domestic cats were big menu items, alongside more typical wild foods.
Oceans
Predator vs Prey
Backyard wildlife
