On Gasparilla Island, located in southern Charlotte and northwestern Lee County, the invasive and environmentally damaging black spiny-tailed iguana has become a major concern to both environmentalists and residents. Unlike the invasive green iguana found on Sanibel and Captiva, which is an herbivore, the spiny-tailed iguana is an omnivore. It eats not only native vegetation, but also local birds, marsh rabbits, green anoles, young gopher tortoises, and snakes. Since 2006 Lee County has spent an average of $100,000 a year in an attempt to eradicate this invasive from Gasparilla Island. To date, nearly 10,000 spiny-tailed iguanas have been caught and euthanized, mostly from the northern end of the island. The sheer numbers of these lizards, coupled with their high fecundity, make their removal a daunting and expensive task.
The eradication program is having results. In 2010 the number of mature, breeding adults was down considerably from the previous estimates of more than 12,000 lizards. The rise of this invasive on one small island is an ominous tale of a well-meaning but misguided individual who released a few breeding pairs from his backyard cage some 30 years ago. One man, George Cera, has personally captured and killed more than 16,000 black iguanas. He wrote a book about his experiences called The Iguana Cookbook-Save Florida, Eat an Iguana.
To date, this incredibly fecund lizard has not yet made it to mainland Florida. As an omnivore, great climber, and prolific breeder, this large iguana could quickly overrun entire ecosystems. In fact, the black spiny-tailed iguana is noted in the Guinness Book of World Records as the fastest lizard alive, having been clocked at speeds of more than 21 miles per hour, just shy of the fastest recorded human running speed of 23.4 miles per hour.
The black iguana has few natural predators in Florida. Bobcats have learned to hunt and eat adults, and owls and great blue herons take the juveniles. Alligators would readily eat them but there are no alligators found on Gasparilla Island. The recent cold winters have also helped to keep the burgeoning population in check.
Black Spiny-tailed Iguana (Ctenosaura similis)
Other names: black iguana, iguana
Status: FL = invasive and expanding its range, IUCN = LC
Length: 3.3-5 ft (1-1.6 m)
Weight: 2.6-8.8 lb (1.2-4 kg)
Life span: to 25 years
Reproduces: egg laying with as many as 70 eggs laid per clutch
Found: LC, ChC, coastal
Months found (breeding season is in lower case): JFMamjjasOND.