Factors That Up the Chances an Exotic Pet Gets Released into the Wild

People dump their exotic animals for logical, if not good, reasons

Matt Collins

Slough slog. Wet walk. Swamp tromp. Whatever you call it, it's a hike in the knee-deep to waist-deep water of the Everglades or other aqueous environments. A slough, pronounced “sloo,” is stagnant or slow-moving water. Slough, pronounced “sluff,” is a snake's shed skin. And the sloughs in the slough is why I won't slog.

Oh, I did a few slough slogs in my younger days. We would range from hammock to hammock, some of which might even let you hang a hammock. A hammock, pronounced “hammock,” is a stand of trees that forms a small island. A hammock, pronounced “lazy man's nap station,” is a sling you can attach to two trees within the hammock.

Anyway, my slough-slog days were when the Everglades included alligators (which ordinarily shy away from people), disease-causing mosquitoes, rattlesnakes and various other critters that could do me harm. But now the Everglades is home to thousands—perhaps hundreds of thousands—of Burmese pythons. And some pythons are big enough to at least try to eat an adult alligator—a famous 2005 photograph shows the remains of a death match in which a python was split asunder after swallowing all or most of a similarly sized gator. So, I'm not slogging through any sloughs that contain enormous, potentially me-eating snakes that properly belong 10,000 miles away in Southeast Asia.


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The founders of this predatory serpent population were possibly some snakes that escaped from a local breeding center damaged during Hurricane Andrew in 1992, as well as pets released into the wild. But why would people toss their adored animal buddy into the swamp?

“Despite the importance releases play in the invasion process for the pet trade pathway, most of the research to date has focused on the factors influencing the establishment of exotic pet populations and not on the factors related to their initial introduction (or release ...),” write Rutgers University researchers Oliver C. Stringham and Julie L. Lockwood in their paper “Pet Problems: Biological and Economic Factors That Influence the Release of Alien Reptiles and Amphibians by Pet Owners,” published online in August in the Journal of Applied Ecology. Therefore, “we set out to identify broadscale and easily measured biological and economic factors that influence the release of these exotic pets by their owners.”

Stringham and Lockwood analyzed databases of animals available for sale as pets and information on life-history traits—that is, how fast various species grow, how big they get, how many offspring they can have. What they discovered is what you would probably suspect, but which until their research, nobody could say for sure: chances that somebody will relocate their pet to the great outdoors depend on how many of the beasties were available to be sold in the first place, how cheap they were and how much damn bigger they'll grow in their relatively long lives than when they were cute little babies.

These factors are independent of the likelihood of the swamp thing establishing itself in its new environment. Thus, in some cases, abandoned creatures live their lives without consequence. But some species take over and bust up the joint. For example, a 2012 study in the Proceedings of the National Academy of Sciences USA found that where the Florida pythons slither, observations of native populations of raccoons were down 99.3 percent, possum sightings plummeted by 98.9 percent, and rabbits were either gone completely or were hiding deep in their holes as they'd done (while called “wabbits”) during the Elmer Fudd incursion of 1940.

The Rutgers authors note that “integrating the release stage into risk management can result in a more robust and accurate assessment of invasion risk.... Such risk assessments have been used to guide legislation aimed at curbing invasions through import bans of high risk species.” The research team also writes that “our results can be used to craft legislation targeted at reducing the probability of release of species. For example, our results can be used to target taxing and licensing efforts towards high-release risk species.... Regardless of the approach, a data-driven effort to document factors that result in exotic pet releases can advance a more comprehensive, evidence-based approach to risk management and policy implementation.”

One day, when evidence-based approaches, data-driven efforts, and reasonable taxation and legislation are back in vogue, the information in this study could come in handy.

Steve Mirsky was the winner of a Twist contest in 1962, for which he received three crayons and three pieces of construction paper. It remains his most prestigious award.

More by Steve Mirsky
Scientific American Magazine Vol 319 Issue 5This article was published with the title “Pets Gone Wild” in Scientific American Magazine Vol. 319 No. 5 (), p. 82
doi:10.1038/scientificamerican1118-82

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