Wildlife & Habitat
Cats, rats, goats, and mice brought by human settlers modified the habitat at Jarvis Island for terrestrial wildlife, and by 1966 the Pacific Ocean Biological Survey Program found only three species of seabirds breeding on the island. The last cat was removed in 1990, and since that time seabird diversity and numbers have increased dramatically. Verification that cats had truly been eliminated came when refuge staff found Audubon’s shearwaters, a small species that is completely intolerant of cats, nesting in former cat dens on the island. Removal of the last cats allowed hundreds of pairs of blue noddies to start breeding at Jarvis again.
Today, Jarvis supports 14 species of breeding seabirds, making it second only to Kiritimati Island in the number of species surviving on islands in the Line archipelago. Its sooty tern colony is one of the largest in the world, with an estimated 1 million terns using the island.
The strong upwelling to the west of the island may allow large numbers of this unusual tern to forage in the neuston layer (the top few inches) of the nearby ocean to thrive there. Jarvis also serves as a wintering site and way station for several species of migratory shorebirds, including the bristle-thighed curlew, a species of concern due to its small population size.
Jarvis Island is the crest of an ancient coral reef cap and massive underlying extinct volcano, emerging from the deep ocean floor of the equatorial Pacific. The equatorial undercurrent deflects off the western flank of the seamount, pushing nutrient-rich waters up into the sunlit zone, thereby increasing marine productivity and benefiting many species of marine life. This important phenomenon may be limited only to Howland, Baker, and Jarvis Islands because of their steepness and location on the equator. The upwelling is especially strong at Jarvis because of its larger size, supporting continuous mats of soft corals and large schools of plankton-eating fish.
Until 2000, the coral reefs at Jarvis were largely unexplored, though 90 species of mollusks had been collected and identified. A narrow fringing reef surrounds the island, but a broad submerged reef terrace extends off the eastern shoreline, dominated by moosehorn and rose corals. Live coral covers about 50 percent of the reef terrace, and about 62 species of corals have been reported at Jarvis as os 2006. Table and staghorn corals are rare but increasing. Heavy wave action limits coral growth on shallow slopes, but encrusting and plate corals are abundant. Live coral covers about 33 percent of the shallow slopes off the western and southern coasts, but less off of other coasts where wave action is heavy. Several submersible dives in 2005 revealed many deepwater corals and other abundant deep sea life at depths of 200-1,000 meters off the western side of Jarvis.
A total of 252 fish species have been recorded at Jarvis Island. Densities of large fish (e.g., sharks, jacks, grouper, and parrotfish) are second only to those at Palmyra Atoll. Large numbers of manta rays are found off the southeast terrace, and sea turtles are also abundant. At least nine species of algae have been collected at Jarvis, including four species of green algae (mostly Halimeda), two of brown algae (mostly Lobophora), and three of red algae (mostly crustose coralline). Jarvis supported the largest biomass of fish compared to any other areas. However, surveys in 2008 reported declines.
Jarvis Island supports only vegetation tolerant of the hot, often extremely arid conditions of the equatorial Pacific, typically small bunch grasses and low herbaceous plants.
Very little is published about the insect or land snail fauna of Jarvis. As with Howland and Baker Islands, the most conspicuous terrestrial invertebrates are the red hermit crabs that rove in large numbers after sunset, eating organic detritus.