2023–24 Fijian Crested Iguana Report

Restoring Forests for Fijian Crested Iguanas

Submitted by Peter Harlow

Taronga Conservation Society, Australia with Mamanuca Environment Society and South Pacific Regional Herbarium, Fiji

replanting for iguanas
Team botanist Alivereti Naikatini (L) and volunteers transferring potted seedlings from Yanuya Island, ready to plant on Monuriki Island.

Overview

The Fijian Crested Iguana (Brachylophus vitiensis) is a Critically Endangered species suffering from habitat destruction and the loss of native forest trees and predation by feral domestic cats, mongoose, and rats. For some island populations of this species, the threat posed by habitat destruction is most clear in the loss of tree species comprising their entire diet.

The uninhabited island of Monuriki is the second-most important island for the long-term survival of this tree-dwelling species, yet there are only 100 to 150 iguanas remaining there today. Monuriki had been subjected to almost 50 years of intensive goat grazing and regular forest fires. The goats were removed in 2011, but recovery of the island’s vegetation did not follow. Eight of the 10 most important food species for Fijian Crested Iguanas had become locally extinct. The only two edible tree species remaining were rare and comprised fewer than 2% of all forest trees. The iguanas remaining on Monuriki could not eat 98% of the remaining trees.

Seedlings grown in the nursery
Volunteer Rory Keenan (L) and Raluve Vadada (R) at the family nursery on Yanuya Island. Seedlings are grown to a larger and stronger size before reintroduction.
Peter Harlow (L) with Joeli Vadada and Cevua seedling

Plant Restoration Objectives

IIF stepped in to provide funding to reintroduce three of the most important native trees in the diet of the Crested Iguana: False Sandalwood (Vavaea amicorum; 62% of iguana diet), Lime Berry (Triphasia trifolia; 16% of diet) and Pacific Jasmine (Jasminum didymum; 10% of diet). Additionally, the conservation team is working toward planting Vesi Wai (Pongamia pinnata) trees, another food source for the iguanas and a culturally valuable plant for Fijians. While only a handful of reforestation projects have taken place in Fiji, and knowledge about reintroducing these species is limited, the conservation team was happy to see a survival rate for the transplanted trees that has provided a solid start in providing food for the remaining iguanas.

IIF also granted funding for the harvest of approximately 3,500 ripe False Sandalwood fruits, which were gathered in four trips to Qalito Island over a six-week period. The hope was that the thousands of seeds in the fruit spread in the forest would result in a large supply of seedlings. Unfortunately, getting these seeds to germinate in the wild has been a challenge. So the conservation team switched plans and began planting established, potted seedlings grown in a nursery. There are now 64 False Sandalwood seedlings established at two sites on Monuriki Island. Within a few years these will be fruiting, and the Crested Iguanas on Monuriki will not only have a good food source, but will also disperse the seeds around the island for natural germination.

Ripe False Sandalwood fruit (L) and native Ebony fruit (Diospyros sp., R) are both important in the diet of Fijian crested iguanas
Volunteer Kara on Castaway Island preparing a False Sandalwood seedling for transplanting. The soil around the roots of each seedling were carefully wrapped in cotton cloth.

Future Plans

The next step was planting more False Sandalwood and restoring the populations of Lime Berry and Pacific Jasmine on Monuriki. The latter two species appear to be fickle in both flowering and producing fruit. During the annual wet season in January 2024, the conservation team returned to Castaway Island to collect 150 False Sandalwood and Lime Berry seedlings. The team planted the False Sandalwood seedlings on Monuriki Island, as well Lime Berry and Vesi Wai potted seedlings. As with earlier plantings, survival rates were modest but fortunately sufficient to push the needle toward reforestation of these species on the island. The conservation team has raised more than 140 False Sandalwood and Vesi Wai seedlings in the same private nursery on Yanuya Island, which are ready for planting.