Nesting Habitat Restoration on Mona Island

Restoring Nesting Sites for the Mona Island Iguana through the Removal of the Invasive Australian Pine

Invasive Australian Pine forest on Mona Island.


Cielo E. Figuerola, Robert J. Mayer, Iván Llerandi, Idelfonso Ruiz and José L. Herrera


Department of Natural and Environmental Resources of Puerto Rico and Island Conservation


In May 2017, we headed to Mona Island to begin the implementation of a project focused on restoring nesting sites for the endangered and endemic Mona Island Rock Iguana by removing the invasive Australian Pine (Casuarina equisetifolia). This project is being developed by the U.S. Fish and Wildlife Service through the Coastal Program, the Department of Natural and Environmental Resources of Puerto Rico (PR-DNER), and Island Conservation, with the support of the local non-government organization Vida Marina. Australian pines were introduced to Mona in the 1930s so their wood could be harvested and used for various purposes, as utility poles, for example. However, transporting the wood off the island was very expensive and logistically challenging. As the years went by, profits decreased and markets changed, and the pine plantation was abandoned. Unfortunately, the plantation was established on prime nesting habitat for the Mona Iguana, making nesting very difficult.

Raking and removing the thick layer of pine needles.

All debris was removed from the logging site.


Invasive Australian Pines have harmful impacts on Mona’s ecosystem in many ways. Through the release of certain compounds, they change the chemistry of the soil and preventing growth of native vegetation. They can cause beach erosion in coastal habitats and can decrease plant biodiversity, just to name a few of their impacts. For iguanas specifically, when pine needles fall and cover the ground, they form an almost uniform carpet of invasive plant matter in the understory, occluding the sandy substrate iguanas need to excavate to build their nests. The pine needle carpet prevents them from nesting in these areas. Another problem is the constant shade produced by the pines — iguanas need to build their nests in areas with sun exposure and in the shady pine forest this is not possible. These pine impacts combined with the ongoing invasive vertebrate species impacts (like egg and hatchling predation by feral pigs and cats) put Mona Iguanas at risk, especially during their most vulnerable life stages. Our main goal with this project is to cut down the pines, remove the pine needle carpet, and then place trail cameras in the restored sites to document iguanas using these newly restored and habitable areas to nest in future nesting seasons. We’re hoping that the wood from these trees can be repurposed to repair infrastructure on the island. Vida Marina has vast expertise in Australian Pine felling through their coastal restoration efforts in the northern region of Puerto Rico.

Despite some challenges, we have been able to conduct three successful field trips and we have met our goals for each trip. So far the team has removed 36 pine trees and over 270 kg of pine needles and debris in 15 days of work. Six new nesting areas for iguanas have been created, which translates into 1.08 km² of ideal habitat for nests. The best reward for our efforts is seeing that iguanas are already nesting in the restored plots! We documented three nest attempts and three nests in-progress in an area that, prior to pine removal efforts, had five pine trees growing and a pine needle carpet five inches deep. Over the past five years, we have been conducting nest surveys and we had never seen a single nest in this area. Unfortunately, after these observations Mona Island received the impact from Hurricane Maria and our follow-up visits were paused. We know the island did not suffer from the winds but it did from the rain. We hope to go back to Mona in the upcoming weeks and assess how the nesting areas have been impacted by the hurricane and how that impact translated into the hatching season. On a positive note, so far our efforts have directly translated into the results we were hoping for, and almost immediately. These results clearly show how important and needed these new nesting sites are for iguanas on the island and how important it is to manage the threats caused by invasive species appropriately.

Iguanas began digging in the newly cleared sites immediately.

The restoration team from Department of Natural and Environmental Resources of Puerto Rico and Island Conservation.