Siargao Island Wildlife Sanctuary (SIWS)

The SIWS includes three major types of ecosystems: 1) terrestrial, 2) wetland and 3) marine, all exhibiting wide biological diversity.

Two species of Rhizophora are dominant in the mangrove forest. So far, only ten endemic species of flowering plants have been recorded, including the Philippine iron wood, Xanthostermum verdugonianus.

Several areas of thick beds of seagrasses and seaweeds were found. There are 59 species of seaweeds, comprising 37 percent of the total number of benthic seaweeds recorded from the Philippines. Also, eight species of seagrasses are found in the area, which is half of all the species found in the Philippines and the ASEAN region.

The fauna include several species of wetland birds, 11 species of terrestrial mammals, nine species of reptiles, three species of amphibians and 105 species of butterflies.

In the marine and wetland areas, 137 species of mollusks, 38 genera of corals and 106 species of fishes were recorded from a single reef.

Several endangered and rare species including Crocodylus porosus are found in the extensive mangrove areas and waters surrounding the island. The green turtle (Chelonia mydas) and the hawksbill turtle (Eretmochelys imbricata), dugongs (Dugong dugon) and whale sharks, (Rhincodon typus) are also present in the area.