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Wildlife & Habitat

Frigatebird chick

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.

  • Birds

    sooty terns 150x118

    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). 

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  • Mammals

    Bottlenose Dolphin 150x90

    On most staff visits to Howland Island, a group of approximately 40 bottle-nosed dolphins (Tursiops truncatus) appear as the ship approaches the island. In 1993, individuals from this group were observed preying on rainbow runners (Elagatis bipinnulatus) that were sheltering under the vessel. Formal quantitative surveys of marine mammal distribution and abundance have not been undertaken at the refuge. Historically, sperm whales (Physeter macrocephalus) were caught near Howland in the nineteenth century (Townsend, 1935, cited in Sibley and Clapp, 1965).

     

  • Reptiles

    green turtle

    Two land species have been documented on Howland Island, the snake-eyed skink (Cryptoblepharus peocidopleurus) and mourning gecko (Lipidodactylus lugubris). Both were reported by Hague 1862. They then served as alternative prey for the cats when they were on the island. During recent visits, only the snake-eyed skink was found. Green turtles (Chelonia mydas) and Hawksbill turtles (Eretomochelys imbricata) are found foraging on the reef around Howland Island.

  • Fish

    emperor angelfish and hump coral 520x289

    Approximately 324 species of reef fish are known from Howland reefs. This compares with 247 species from nearby Baker. Moreover, ten families of fish reported at Howland have not been reported from Baker, and six minor families from Baker have not been reported from Howland. Of interest is the presence of several species of goby and scorpion fish families at Howland and the lack of these families at Baker.
     

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  • Invertebrates

    Hermit crab

    Howland Island is home to large numbers of the strawberry hermit crab, Coenobita perlatus. This large biomass of land crabs plays a dominant role in terrestrial food webs on the island where they consume a wide variety of organic matter.

  • Marine Habitat

    staghorn colonies 150x118

    Howland’s shallow marine benthic habitats consist of fringing reef crests, shallow back reefs, steep fore reefs, spurs-and-grooves, and small reef terraces. The last two habitats are restricted to the windward (east side) of the island. In addition, a shallow short channel was blasted through the narrow fringing reef during the pre-World War II era to facilitate small boat access between the shoreline and ocean. The deep slope habitats below depths of 65-98 feet have not been surveyed by divers, although remotely operated vehicles (ROVs) have been launched to collect video- and camera-based data. Pelagic habitats occur further offshore beyond the influence of upwelling and nearshore oceanographic processes. Nearshore habitats include distinct upwelling zones off the west side of the island; oligotrophic waters off the windward reefs; and turbulent rip currents and possibly mesoscale eddies off the north and south ends of the island. The PIFSC has conducted oceanographic research off the island to contrast the differences between nutrient rich upwelling zones and the ambient nutrient-poor ocean conditions outside areas of upwellingcurrents.

     

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  • Island Habitat

    Kou on Howland

    Howland Island is vegetated with grasses, herbaceous plants, and shrubs. Areas devoid of vegetation occur along exposed beach and shoreline areas. Only strand species able to survive long periods of drought and irregular opportunities to reproduce during the infrequent wetyears of the ENSO persist here. By 1924 when Christophersen (1927) did the first thorough survey of Howland Island’s vegetation, there had already been approximately a century of visits by Europeans and guano miners. Despite this traffic and the potential for introductions, Christophersen found a very depauperate flora consisting of five native species (Lepturus repens, Boerhavia sp., Portulaca lutea, Tribulus cistoides, and Cordia subcordata) and one that had probably been accidentally introduced (Portulaca oleracea). Since then at least 4 more species were intentionally introduced (Cocos nucifera, Casuarina sp., Pandanus sp., and Coccoloba uvifera) and at least 7 as wave carried adventives or additional accidental introductions by humans (Digitaria pacifica, Sophora tomentosa, Sida fallax, Scaevola taccada, Suriana maritima, and Tournefortia argentea) for a contemporary total of only 16 species. On a short visit in 2004, only nine species of plants were located (Flint and Eggleston 2004). It is likely that seeds of additional species are regularly washing up on the beach and then dying back as conditions become too dry or high surf washes the plants away. The link below lists all the plant species of Howland Island, collections or first observations, and most recent information about current presence or absence. 

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Last Updated: Jan 21, 2016
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