Ecosystems Reclaimed by Major Predators, Alligators, and Sea Otters

Large predators like mountain lions, alligators and killer whales are in the process of moving into ecosystems that are not traditionally associated with them. 


Videos have been recorded of mountain lions prowling grasslands, and alligators seen in Florida beaches. Killer whales have been seen swimming in freshwater rivers. None of this is natural, but a lot of people hypothesize that the animals are taking new territories over because their populations have rebounded due to conservation efforts.  

New research published this week by Current Biology, which worked with researchers from Duke, and the University of California suggests that the animals are actually returning to and taking back many of these ecosystems that they left. Due to industrialization and human expansion, there has been an ongoing battle to give more to animals and to conserve a lot of the land. Sometimes this doesn’t work out. But despite what is done, a lot of the Predators have decided to go where they want.

The researchers specifically looked at sea otters on the Pacific coast of the U.S. who have expanded recently from forests to estuaries, salt marshes, and seagrass beds. They also looked at alligators in the Southeastern U.S. who have continued to expand from freshwater swamps to marine habitats like mangroves and seagrasses.

The research concludes that the predators are reconquering ground they had occupied before human activity drove them out. The research is based off of historical and archeological evidence on where these animals used to be before human expansion.

Study co-author, Rachel Carson and associate professor of Marine Conservation Biology at Duke’s Nicholas School of the Environment, Brian Silliman, said in a Duke University press release, “We can no longer chock up a large alligator on a beach or coral reef as an aberrant sighting, 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.”

He also made this statement in the press release, “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 live best in saltwater kelp forests; orangutans need undisturbed forests; marine mammals prefer polar waters. But this based on studies and observations made while these populations were in sharp decline. Now they are rebounding. They’re surprising us by demonstrating how adaptable and cosmopolitan they really are.”

The research proves that this is not an outlier situation or a short-term blip. The animals are just going back to where they used to be. This is also something that benefits humans and animals alike. For example, sea otters in estuarine seagrass beds help protect the beds from being smothered by the kind of algae that feeds on its excess nutrient runoff from inland farms and cities. Otters eat the Dungeness crabs which eat too many algae grazing sea slugs that are supposed to protect the beds.

According to Brian Silliman, “It would cost tens of millions of dollars to protect these beds by re-constructing upstream watersheds with proper nutrient buffers, but sea otters are achieving a similar result on their own, at little or no cost to taxpayers.”

The study’s conclusion argued that its findings should be taken into consideration when lawmakers have to determine conservation policy.




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