Dispersión de Semillas dentro del Bosque

Please don’t feed the iguanas!

The green iguana (Iguana iguana), also known as the American iguana, is a large, arboreal, mostly herbivorous species of lizard of the genus Iguana. Usually, this animal is simply called the iguana. The green iguana ranges over a large geographic area, native from southern Brazil and Paraguay as far north as Mexico, and has been introduced from South America to Puerto Rico and is very common throughout the island, where it is considered an invasive species.

A herbivore, it has adapted significantly with regard to locomotion and osmoregulation as a result of its diet. It grows to 1.5 meters (4.9 ft) in length from head to tail, although a few specimens have grown more than 2 meters (6.6 ft) with bodyweights upward of 20 pounds (9.1 kg).

This iguana (also known as “la gallina de palo”, meaning “bamboo chicken” or “chicken of the trees” in Puerto Rico) has been in the island’s environment for decades. It is estimated that the first introductions, escaped pets, occurred in the seventies. However, it was not until the 1990s that an explosion of the population of this species began to be noticed.

Wildlife scientists who study exotic species use a statistical parameter known as the “rule of ten”: one in 10 animals escape into the wild; one in 10 of the one that escape survive to establish a reproductive population; and one in 10 of these established species becomes a pest.

Since, statistically, few species escape and even fewer survive, the populations increase very little at first. However, for those species that manage to escape, survive and thrive, the population gradually increases and eventually, the increase is exponential, as the number of reproductive pairs increases with each generation.

So, for years most people did not even notice that the iguanas had already established themselves in Puerto Rico. Now they are practically everywhere. The Department of Natural and Environmental Resources (DNRA by its Spanish initials) estimated at least four million iguanas in 2012, which was a conservative estimate. Today there should be many, many more.

These large reptiles have adapted very well to the types of habitat available in Puerto Rico. They reproduce at least annually. Interestingly and unfortunately for our environment, the female stores sperm in her body and is able to self-fertilize her eggs for several years without the need to mate again, and can live up to two decades in the wild. In other words, it is very difficult to stop their population growth at this time. Only a high consumption of iguana products and the marketing of these could generate the necessary catch rate to control the iguana population on the islands of Puerto Rico.

Is there a solution to the problem of overpopulation of exotic species like the green iguana, and is there anything that can be done to prevent history from repeating itself with other exotic species?

The real problem is that, once we start seeing exotic species in our parks, forests and bodies of water, the population of these is already significant. If the population of the invasive species is small, perhaps it can be controlled if it is dealt with quickly enough. With a large population, unfortunately, it becomes virtually impossible unless the habitat where the species is found is clearly defined by boundaries that allow wildlife experts to corral the population. Wildlife experts have only been able to eradicate or control species on small islands or manageable sites.

(Adaptado de / Adapted from “Preguntas Frecuentes sobre la Iguana Verde o Gallina de Palo en Puerto Rico / Frequently Asked Questions about the Green Iguana in Puerto Rico”, por / by: Ricardo López-Ortiz, MS,PhD, Puerto Rico DRNA)