Wildlife & Habitat
The low reef island is the crest of an ancient coral reef cap and massive underlying volcano. Beyond the shallow fringing reef and terrace, the slopes of the extinct volcano drop off sharply to the deep floor of the equatorial Pacific Ocean. The equatorial undercurrent deflects off the western flank of Howland, pushing nutrient-rich waters up into the sunlit zone, 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.
A total of 109 species of stony corals have been identified at Howland through 2010, including thickets of staghorn, plate, brain, and table corals. The 8 most abundant genera are Acropora, Favia, Fungia, Leptoseris, Montipora, Pavona, Pocillopora, and Porites. Despite a possible recent massive coral kill at Howland, related to the 1997-98 global bleaching event, live coral coverage is high, averaging more than 50 percent on the terrace and on some portions of bottom habitat. However, a massive bleaching event was underway in February 2010.
Seabirds and shorebirds are the dominant wildlife on land. Thirteen seabird species and nine shorebird species have been observed during the limited trips to Howland Island. The earliest bird surveys at Howland Island took place long after the introduction of Polynesian rats (by 1854), making it difficult to know exactly what bird species were present originally. Cats were introduced during 1935 to 1942, resulting in a further loss of seabird diversity. Polynesian rats were eliminated from the island sometime after 1938, and feral cats were eliminated from the island by 1986. Today the most numerous breeding seabird species at Howland are the lesser frigatebird (Fregata ariel), masked booby (Sula dactylatra), and sooty tern (Onychoprion fuscatus).