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Why Are Iguanas' Skulls Being Crushed In The Name Of Science?

Joe Raedle
Getty Images

In an effort to reduce the number of invasive iguanas in South Florida, the has funded a project in which scientists from the University of Florida approach green iguanas sleeping at night with the goal of killing them.

According to a report in the Sun Sentinel newspaper on March 9 — and followed up with pieces in other media, including The Washington Post and National Geographic — one of the methods the scientists use is to drive a bolt into the iguana's head using a specialized tool. And, in some cases, they swing the animal against a solid object to bash in their skulls and brains.

The Sun Sentinel reported one of the scientist's claims that these methods are the "most humane" way of killing the iguanas — and notes claims that it falls within the state law about cruelty to animals. About 300 iguanas are known to have been killed so far. The study ends in June.

As I see it, these actions fit — even if unintentionally — a definition of animal cruelty. As the Animal Rights Foundation of Florida put it in a letter to the Miami Herald, the actions are downright "brutal" ways of dealing with living animals.

For one thing, the use of a bolt gun does not always render a target animal unconscious immediately, as Gene Baur of Farm Sanctuary points out in writing about farmed animals. Here, the slaughterhouse carries a lesson that we should not ignore when dealing with the iguanas, who most certainly can think, feel, and suffer.

It's a distressing notion, as well, that in the name of conservation, scientists act to crack animals' skulls against their research equipment — including the boats and trucks used to track them down. How could this not cause great pain to the iguanas in their last moments? How often does the act of killing by this method not cause a quick death? I don't know the answers to these questions, but I do know that no scientist — indeed no person — should send this kind of message about the value of sentient animals' lives, whether those animals are invasive to a region or not.

The Florida Fish and Wildlife Conservation Commission does not agree with this assessment. Carli Segelson of its communications department told me on Monday by email that "the University of Florida is using acceptable methods which have been put forth by the American Veterinary Medical Association" and that the study will continue as planned. Following the initial publication of this piece, University of Florida communications officer Ruth Borger responded via email, "We do not plan to comment further about this program."

Green iguanas' range includes parts of Mexico, Central America, the Caribbean and Brazil. They are reptiles whose behavior is highly social. Gordon Burghardt, Harry Greene and A. Stanley Rand describe in an article in Science magazine their observations in Panama of females nesting communally and of hatchlings emerging from nest sites together then closely attending to one another's movements. These authors write about the "coordinated social interaction, vigilance, and gregariousness" of young iguanas.

In a separate paper, Burghardt describes socially directed body rubbing, tail wagging and even grooming among the iguanas.

In other words, it's wrong to think that these reptiles are somehow simplistic creatures compared with birds and mammals. Intricate social behavior shouldn't be a deciding factor in whether animals are treated with kindness or cruelty, but it helps to know something about the organism we are considering here.

What do these iguanas do to earn them a bad reputation in Florida, leading to programs for their eradication via such brutal methods?

Lori Marino, neuroscientist and executive director of , responded by email in this way when I posed that question to her:

"Not much, it seems. They eat decorative plants, defecate, and, if you continue to bother them or corner them, ... wait for it... could slap you with their tail. According to the University of Florida IFAS Extension, iguanas eat 'valuable landscape plants...' and even '...flowers'.

"Trumped up charges against them include the fact that their feces are 'unsightly' and may carry salmonella, though no evidence for this claim is given. And, furthermore, if cornered, they may use their claws or tail to defend themselves, although they are not known for unprovoked aggression.

"This is a case of 'not in my backyard' syndrome and is a seriously overwrought response to these peaceful reptiles originally brought here by our own species."

The Sun Sentinel notes a similar set of concerns:

"The invasive reptiles have a penchant for destroying landscapes, damaging seawalls and pooping in pools. They also might be frightening to see, resembling some type of prehistoric creature."

I understand that invasive species often do require wildlife management: The question is how much and by what methods. Let's not forget that of all invasive species on earth, we humans ourselves may properly be considered at the top of the list. We routinely take over other animals' habitats and cause incredible destruction to other species and the environment.

In her message to me, Marino put it this way:

"Our classification of which species is 'wildlife' and which is 'invasive' tends to be based on our own aesthetics and convenience. But, our own species has been the most invasive of all, globally.

"While we overlook our responsibility to the environment with lenient regulations on exotic animal pet trade and the [commodification] of other species, we ask the iguanas to 'take the fall for us'. There is nothing humane or even scientifically-sound about 'fixing the landscape' to our liking. But that is exactly what is being done by the University of Florida in the [wanton] killing of healthy iguanas."

For me, the bottom line is this: The costs of crushing green iguanas' skulls — to the animals and to our own sense of humanity — is simply too great for this project to continue.

Barbara J. King is an anthropology professor emerita at the College of William and Mary. She often writes about the cognition, emotion and welfare of animals and about biological anthropology, human evolution and gender issues. Barbara's new book isPersonalities on the Plate: The Lives and Minds of Animals We Eat. You can keep up with her on Twitter@bjkingape.

Copyright 2021 NPR. To see more, visit https://www.npr.org.

is a contributor to the NPR blog 13.7: Cosmos & Culture. She is a Chancellor Professor of Anthropology at the College of William and Mary. With a long-standing research interest in primate behavior and human evolution, King has studied baboon foraging in Kenya and gorilla and bonobo communication at captive facilities in the United States.