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Sperm whales live in the remote open ocean. Or at least, that’s what scientists have long thought. The U.S. government’s 2010 recovery plan for sperm whales characterizes their range as “generally offshore.” A 2016 study of their Australian range describes the whales as foraging in “deep offshore areas of the world’s oceans.” This understanding goes way back. In Moby-Dick, published in 1851, the whaling ship Pequod chases sperm whales far from shore, days from port.
But that doesn’t mean sperm whales want to restrict themselves to the open ocean. A new study that looks at records from the heyday of “Yankee whaling”—1792 to 1912—found that sperm whales used to hang out much closer to the coast. Though sperm whales need deep water to hunt for food, they abandoned areas near the coast because that’s the first place humans hunted them out. “We typically go for what’s easily accessible first,” Tom B. Letessier, the lead author of the study and a marine biologist at the Zoological Society of London, told me. Those remote ocean habitats, in other words, aren’t the only places where sperm whales have always lived; they are the last hideouts of the whales that survived centuries of whaling that reduced their population by more than half. (The study focused on the Western Indian Ocean, but the pattern is likely the same around the world, Letessier said.)
A generation after the end of significant whaling in 1986, the ocean’s giants are still in hiding. But if humans managed to stop hitting them with ships or tangling them in nets and were able to make marine activities a lot quieter, there should in theory be nothing stopping sperm whales from recolonizing those coastal areas. In places where the sea gets deep close to shore, like Monterey Bay, California, you could probably see them spout from the beach.
Sperm whales aren’t the only species for which our range maps might be all wrong. Lots of species’ contemporary ranges are likely defined not just by climate tolerance or availability of food but by distance from dangerous humans, experts told me. So are we trying to save animals in the wrong places? If our ideas about where species belong are based on relict populations that live as far from humans as possible, we risk boxing wildlife into limited, resource-poor areas. In a world where animals are already dealing with rising temperatures, hunting, fishing, and the commandeering of ever-larger chunks of their homes for agriculture and development, trying to conserve them in subpar habitat seems like a terrible idea.
Species conservation often relies on the idea of a “native range,” a somewhat amorphous concept that roughly means the area where a species normally or naturally occurs—not including any places where humans brought it. That range is typically assumed to be the best possible habitat for a species. Protected areas may be built around it. Reintroduction efforts will attempt to repopulate it. And if species stray outside it, they may be considered “invasive” and possibly even targeted for removal.
But “using the concept of native range limits us,” Brian Silliman, an ecologist at Duke University, told me. Silliman, who wasn’t involved in the sperm-whale study, believes that many maps of native ranges are off—and not by just a little bit. He gave me an example he learned about in a very visceral way: by nearly being eaten by an alligator. He was collecting data on snails on a barrier island off the coast of Georgia and was ambushed by a 12-foot gator, a species not known for hanging out in or near the ocean. Silliman found himself pinned under the gator and fought back, punching its sides until it got spooked and fled. “Turns out alligators are all over the southeast shore in marine environments,” he told me. Why didn’t we know gators could thrive on the beach? Because we had killed all the beach gators.
The same phenomenon has occurred with many animals. Calling a cougar a “mountain lion” suggests that it prefers the mountains, but Silliman says they used to prowl the lowlands, too, where there were more prey. “There’s no such thing as a mountain lion,” he said. “We just made that up. That’s the last place that it lived.” When conservationists worked to reintroduce sea otters to the Pacific Coast, they assumed they would live … in the sea. But reintroduced otter populations are flourishing in salt marshes and seagrass beds, where they are protected from orcas and sharks.
Silliman thinks our assumed native ranges for many species are just a quarter of the total historical range. And in many cases, the “native range” that animals occupy now might be places where they can barely survive—because they are the harsh, marginal places that humans don’t want to go: steep slopes, high mountains, polar seas. Conservationists may be pouring resources into the wrong places, trying to coax animals to live and reproduce in suboptimal environments.
Calling for conservation to take into account the “full” or “true” range of a species seems sensible, but nailing down what that range is gets complicated fast. If the point is to figure out where an animal “naturally” lived before it was hunted or harassed out of parts of its habitat by humans, in some cases that might mean looking back a few hundred years. In others, it might mean turning back the clock thousands of years. One analysis of ancient-panda diets suggests that their mountain bamboo forests are not their ideal habitat; it calls for new panda protected areas in the lowlands, where their diets could be more varied. This would mean returning to a range they inhabited thousands of years ago.
In North America, if you try to define native ranges as where species lived before people arrived and began influencing ecosystems, your maps are going to be from the Pleistocene. You would be stuck trying to re-create a very different world—a Midwest covered in glacial ice, a land of mammoths and giant ground sloths. Elk arrived from Eurasia only 15,000 years ago. The cattle egret arrived in North America, on its own wing power, in the mid-20th century. Ranges are also definitely going to keep changing in the future, especially as the climate warms. Should new areas colonized by species seeking cooler temperatures count as part of their native range?
Conservationists have typically focused on protecting and restoring species in their native range only, but if that range is often misunderstood and fundamentally dynamic, creating a single definitive map for each species may remain elusive. The way out of this dilemma that I favor remains a minority view, but I like it for its logical coherence: Ditch the idea of a single native range altogether.
Instead of asking “Where does this species belong?” some conservationists are beginning to ask something more like “Where can this species thrive without causing unwanted effects?” They are looking at areas where the species can do well today—and in a warmer tomorrow. These areas are very likely to overlap significantly with a more traditionally defined native range, but they could include areas the species has never been before—or at least not in human memory. One broadly accepted approach that moves away from strict fealty to native ranges is to welcome new arrivals moving with warming as climate “refugees,” rather than labeling them as “invasive.” Another more controversial tactic is to physically move species to suitable habitats as the climate makes former habitats inappropriate, a practice called “assisted colonization.”
Learning about the environmental history of places and species will still be important, even if we move away from basing our conservation strategies on native ranges. For example, knowing that sperm whales are happy to live near the coast is useful information for imagining where they might thrive in the future—and for drawing the contours of proposed marine protected areas.
Given how much humans have changed the world, we are unlikely to be able to return everything to the way it used to be, even if we could agree on how far back to go. But we can work hard to create a world where wild animals are abundant and thriving in habitats that meet their needs. And the good news is that when you stop killing animals and protect the kind of habitat they like, they can bounce back. Wolves recolonized Western Europe, and humpback whales and some populations of green sea turtles have seen population increases of more than 1,000 percent since being listed as endangered. Wild animals can return.
When and if animals recolonize ancient habitats or expand to new habitats that are now quite close to human spaces, there are likely to be some tension. Researchers are already documenting an uptick in human-wildlife contact as humans sprawl into wildlands, as animals move in response to climate, and as conservation succeeds in bringing species back to old haunts. Coexistence can create conflict, danger, crop loss, and other problems, but there are benefits too. Seeing sperm whales from the beach, hearing a wolf howl from the suburbs, giving a green turtle, or an alligator, some leeway when you head out to go surfing: In a world where we work hard to make space for other species, we might be surprised at how cozy they are willing to get with us humans.