Alligators on the beach. Killer whales in rivers. Mountain lions are miles away from the next mountain.
In recent years, the sightings of large carnivores in places where conventional wisdom says they should "not be" have increased, largely because the local population, which has been hunted to extinction, rebounds thanks to conservation [1
A Duke University book published today in the journal Current Biology suggests the opposite.
It notes that alligators, sea otters, and many other large predators – both marine and terrestrial – reenter new and alien habitats to re-colonize ecosystems that were originally hunting grounds for them before humans decimated their populations and long before scientists began to study them.
"We can no longer capture a large alligator on a beach or coral reef as an anomalous sighting," Sai d Brian Silliman, Rachel Carson Associate Professor of Marine Biology at the Duke's Nicholas School of the Environment. "It's not an outlier or a short-term blip, it's the old norm as it was before we pushed these species into hard-to-reach shelters and now they're coming back."
Silliman and his colleagues found that alligators, sea otters, river eaters, gray whales, gray wolves, mountain lions, orangutans, and bald eagles, among other large carnivores, now also contain data from recent scientific studies and government reports in the "novel" habitats abundant or more abundant than in traditional ones.
Their successful return to ecosystems and climates that have long been banned or too stressful for them leads to one of the most widely used paradigms of large-scale animal ecology, Silliman
"The widely accepted assumption in scientific and popular media is Alligators love swamps, sea otters are best in saltwater forests, orangutans need undisturbed forests Marine mammals prefer polar waters, but this is based on studies and observations made during the severe decline They value us by demonstrating how adaptable and cosmopolitan they really are, "said Silliman.
For example, marine animals such as stingrays, sharks, shrimp, horseshoe crabs and manatees now account for 90 percent of alligator diets in seagrass or mangrove ecosystems, showing that alligators adapt very well to life in salt water
The unexpected adaptability of these returning species presents exciting new opportunities for protection, Silliman emphasized.
"It tells us that these species can thrive in a much wider variety of habitats Sea otters, for example, can adapt and thrive if we introduce them into estuaries that have no kelp forests of climate change, the otters will not" , he said. "Maybe they can even live in rivers, we'll find out soon enough."
When top predators return, the habitats they re-occupy also benefit, he said. For example, the introduction of sea otters on seabed beds helps to prevent beds from being suffocated by epiphytic algae that feed on excess nutrient effluent from farms and towns. The Otters do this by eating Dungeness crabs, which otherwise eat too many algae grazing sea slugs, which form the bed's front line of defense.
"It would cost tens of millions of dollars to protect these riverbeds by rebuilding upstream watersheds with adequate nutrient buffers," said Silliman, "but Sea Otters achieve a similar result alone, with little or no cost to taxpayers."
Sea Otters promote the recovery of seagrass meadows
"Are the spirits of nature's past nature today's ecology?" Brian R. Silliman, Brent B. Hughes, Lindsay C. Gaskins, Qiang He, M. Tim Tinker, Andrew Read, James Nifong and Rick Stepp. Current Biology 7. May 2018. doi.org/10.1016/j.cub.2018.04.002