Sarigan is an extinct volcano, with the highest point being at 549 meters (Berger et al. 2005). The slopes are so steep that hiking is dangerous; in fact, one member of our field party, Ping Kapileo, broke his ankle while cutting transects.
Sarigan’s tropical climate is hot and humid, with daytime temperatures ranging from 84° to 90°F., and nights from 70° to 75° F. (ibid.). The island is small, 5.0 square miles in area and 3 km across (ibid.); one could hike across it in a day, if one didn’t mind climbing a lot. Sarigan’s steep eastern and southern slopes are sparsely vegetated with grasses and ferns, whereas the western and northern slopes are more gentle and support native forest and coconut forest (Fancy et al. 1999). Native forest is common in ravines and was estimated in 1997 to cover 29 ha of the island, comprising 18% of the forest area of Sarigan (ibid.). Coconut (Cocos nucifera) plantations were estimated to cover 133 ha of the island, comprising 82% of the forest area (ibid.). Sarigan’s forests have been severely degraded by feral goats and pigs. In 1997, little palatable vegetation was found in the understory of the coconut forest by Fancy et al. (1999). Feral animals were removed through a campaign conducted during 1998, utilizing shooting from a helicopter and on the ground (Kessler 2002). Numbers of plant species, frequency of individual plant species and ground cover increased dramatically within a year after feral animal removal (Cruz et al. 2000).