Iguanas are present in Puerto Rico, but they are not native to the island. They are a widespread, established invasive species that poses a significant environmental and economic concern for the Commonwealth. Understanding the situation requires examining the specific species involved, how it arrived, and the damage it causes across the island’s natural and built environments.
The Status of the Green Iguana in Puerto Rico
The specific species that has successfully colonized the island is the Green Iguana (Iguana iguana). This introduced and invasive species is causing demonstrable harm to the environment and human interests. Estimates suggest the population numbers in the millions, potentially surpassing four million individuals as of 2012.
Population densities in certain habitats have been recorded as high as 223 individuals per hectare, far exceeding concentrations observed in the iguana’s native range. These high densities are concentrated in specific areas, particularly coastal zones, mangrove swamps, urban centers, and areas featuring man-made waterways. Iguanas also utilize road corridors for basking and dispersal, expanding their reach into new territories.
How the Iguanas Arrived and Spread
The introduction of the Green Iguana began primarily due to the exotic pet trade starting in the 1970s. Many imported individuals escaped or were intentionally released by owners who found them difficult to care for once they grew larger. Genetic analyses suggest that a significant portion of the founding population originated from commercial iguana farming operations in countries like Colombia and El Salvador.
The iguanas found an ideal environment in Puerto Rico. The tropical climate provides year-round warmth and abundant vegetation, which suits this largely herbivorous species. Crucially, the island environment lacks the natural predators that control iguana populations in their native ranges. This low-predation environment, coupled with high reproductive success (females lay clutches of eggs with over 90% viability), allowed the population to grow exponentially from the 1990s onward.
Ecological and Infrastructure Impact
Green Iguanas cause significant negative impacts across ecology, agriculture, and infrastructure, with annual losses estimated in the millions of dollars. Ecologically, iguanas compete with native fauna by consuming the flowers and fruits of native plants. This herbivory reduces seed production for local flora and decreases available nectar for native nectivores, such as hummingbirds and bats.
In the agricultural sector, the damage is direct and substantial, as iguanas feed on a variety of commercial crops. Specific crops frequently targeted include squash, papaya, watermelon, tomatoes, and beans, leading to considerable financial losses for farmers. Iguanas are skilled climbers and often feed on valuable produce in fields and gardens.
The structural integrity of the island’s built environment is also compromised by the iguanas’ behavior. Females dig extensive burrows to create nesting chambers, which destabilize the ground beneath infrastructure:
- Sidewalks
- Canal banks
- Seawalls
- Roadbeds
Iguanas also seek out heat sources to aid in their metabolism, often congregating near electrical substations and airport runways. This behavior can lead to short circuits, mechanical failures, and power outages.
Control and Management Efforts
The government has classified the Green Iguana as an invasive pest to facilitate control measures. The Department of Natural and Environmental Resources (DNER) established an interagency committee to develop a systematic approach. One main strategy involves the physical removal of animals through culling, often carried out by licensed individuals and volunteer groups using air rifles.
Efforts also focus on targeting the reproductive cycle, with teams actively seeking out and destroying iguana nests to remove thousands of eggs each season. Experts estimate that roughly 80% of the population must be removed annually to achieve a neutral growth rate, highlighting the difficulty of eradication. For agricultural protection, simple perimeter fencing is the most effective management method for farmers. The government has explored commercial utilization, encouraging the safe exportation of meat and other products derived from removed iguanas.