Large Predators Are Reclaiming Some of Their Old, and Unexpected, Territories

large predators reclaiming territory

Story at-a-glance -

  • Modern-day humans are increasingly sighting large predators in unexpected areas, like an orca, typically an ocean dweller, spotted in an Oregon river
  • These occurrences are deemed anomalies, but according to an intriguing new study published in Current Biology may actually be a sign of the animals reclaiming territory that was theirs all along
  • For instance, alligators on the southeast U.S. coast have expanded into saltwater ecosystems, mountain lions have expanded into grasslands and wolves have expanded into coastal marine ecosystems
  • The findings are positive in that many species may be more adaptable than we thought, which bodes well for the continued threats to their habitat, and as animals recolonize areas they bring with them immense benefits to the ecosystem that would be difficult, if not impossible, to recreate otherwise

By Dr. Karen Shaw Becker

It’s taken somewhat for granted that large predators, from big cats to alligators, live in very specific and distinct habitats. Mountain lions live in mountains, for instance, alligators in freshwater and wolves in grasslands and woodlands, for instance. But what if those are only assumptions, made because human encroachment on these wild animals’ habitats has made it so?

Modern-day humans are increasingly sighting large predators in unexpected areas, like an orca, typically an ocean dweller, spotted in an Oregon river and then, a couple of years later, in Scotland’s river Clyde. Meanwhile, alligators, which are said to tolerate saltwater but not prefer it, have been spotted on Florida’s beaches while mountain lions have been spotted in residential and even urban areas — far from a mountain in sight.

These occurrences are deemed anomalies, but according to an intriguing new study published in Current Biology may actually be a sign of the animals reclaiming territory that was theirs all along.1

Large Predator Habitats May Be Far More Diverse Than Expected

Human activities, ranging from hunting to habitat destruction, have decimated the populations of many large animal species worldwide. As such, in the modern day we’ve only seen them exist in limited habitats, but that doesn’t mean it was always that way. Researchers wrote in Current Biology:2

Humans have decimated populations of large-bodied consumers and their functions in most of the world's ecosystems. It is less clear how human activities have affected the diversity of habitats these consumers occupy. Rebounding populations of some predators after conservation provides an opportunity to begin to investigate this question.”

Conservation efforts have paid off for a number of species, and with their numbers coming back they’re expanding into wider ranges, including those where they’re not typically expected. The study gave a number of examples, including:

Sea otters along the northeast Pacific coast have expanded into estuarine marshes and sea grasses

Alligators on the southeast U.S. coast have expanded into saltwater ecosystems

Seals have expanded into subtropical climates

Mountain lions have expanded into grasslands

Black bears have expanded into intertidal zones

Wolves have expanded into coastal marine ecosystems

Orangutans, long thought to require undisturbed forests, have expanded into disturbed forests

According to study author Brian Silliman, Ph.D., Rachel Carson associate professor of marine conservation biology at Duke University's Nicholas School of the Environment, animals like alligators, gray whales, wolfs, mountain lions and orangutans may be showing up in novel environments just as much as their traditional ones, if not more. He said in a press release:3

“The assumption, widely reinforced in both the scientific and popular media, is that these animals live where they live because they are habitat specialists. Alligators love swamps; sea otters do best in saltwater kelp forests; orangutans need undisturbed forests; marine mammals prefer polar waters.

But this is based on studies and observations made while these populations were in sharp decline. Now that they are rebounding, they’re surprising us by demonstrating how adaptable and cosmopolitan they really are.”

Animals May Not Be Seeking Out New Habitats but Re-Colonizing Old Ones

When an animal appears somewhere unexpected, somewhere it “shouldn’t” be, it’s often suggested that it may be exploring a new area in search of food, given the stresses put on its usual habitat. This does happen, but it’s also possible that, as their numbers rebound due to conservation efforts, animals are re-colonizing areas they’ve lived in all along.

“We can no longer chock up a large alligator on a beach or coral reef as an aberrant sighting,” Silliman said. “It’s not an outlier or short-term blip. It’s the old norm, the way it used to be before we pushed these species onto their last legs in hard-to-reach refuges. Now, they are returning.”4

Silliman and colleagues used data from studies and government reports to make their determinations, looking in-depth at alligators and sea otters, including using fossil evidence to prove they likely once lived in areas now considered off limits.5

“Historical records, surveys of protected areas and patterns of animals moving into habitats that were former hunting hotspots indicate that — rather than occupying them for the first time — many of these animals are in fact recolonizing ecosystems,” the researchers wrote.6 The revelation has major implications, including a need to perhaps reset historical baselines that guide expected predator diversity in specific habitats.

This, in turn, would challenge conservationists to expand protections in the newly re-colonized habitats as well as require humans to learn how to coexist with the new (or not-so-new) inhabitants.

There’s good news to the findings, too, including signs that many species may be more adaptable than we thought, which bodes well for the continued threats to their habitat. In addition, as animals re-colonize areas they bring with them immense benefits to the ecosystem that would be difficult, if not impossible, to recreate otherwise.

Silliman used the example of sea otters returning to estuarine sea grass beds, where they feast on Dungeness crabs. The crabs like to eat sea slugs, which are a prime defense against algae overgrowth that can smother marine life. So by cutting down on the population of Dungeness crabs, the otters help sea slugs to thrive, reducing algae growth and improving the marine environment.

"It would cost tens of millions of dollars to protect these beds by re-constructing upstream watersheds with proper nutrient buffers," Silliman said, "but sea otters are achieving a similar result on their own, at little or no cost to taxpayers."7 As large predators return to other unexpected areas, it’s likely they’ll have equally unexpected, and impressive, benefits to the surrounding ecosystems and overall environment.