Ecologically, Teraina is also highly interesting, for several reasons. Firstly, as is readily apparent from its peculiar geographical and geological features, it possesses a combination of
ecosystems that is quite unique in the entire world. Secondly, it holds the world's largest population of a rare bird
species though it is over from that bird's original home. Furthermore, it was until fairly recently home to some enigmatic
dabbling ducks which are now
extinct. Last, the island's
biodiversity seems to prove quite conclusively that, probably by about 1200 AD or so, the island was temporarily inhabited by a significant number of humans. At present, there is no formal protection for the islands' ecosystems or species, but it has been suggested to legally protect key habitat, namely the boglands. it actually benefits from human land use change and the
feral cats. The former provides the birds with more habitat, while the cats have so far managed to keep Teraina completely free of
black rats (
Rattus rattus) which due to their tree-climbing habits would seriously jeopardize the species' existence, should they become established in numbers.) and
apple guava (
Psidium guajava) are the most significant, apart from the coconuts.
Frangipani (
Plumeria) and
hibiscus are popular as
ornamental plants. In any case, there is considerable evidence from
Ancient Hawaiʻi that
Polynesian seafarers travelled between southeastern Polynesia and
Hawaiʻi with some regularity, perhaps as early as 400 AD, but certainly by about 1200 AD. Since it is almost inconceivable – given the prevailing winds, ocean currents, known trade routes, and the difficulty with which these birds can be kept alive during voyages), an imperial-
pigeon (
Ducula), and maybe a
Todiramphus kingfisher or an
Aplonis starling make the most likely candidates for birds gone extinct prehistorically. It must be considered, however, that given the lack of fieldwork it is not quite clear what effect changing
sea levels would have had on Teraina. If the sea level were only half a meter (c. 2 ft) higher it is certainly possible that the forest and freshwater lake would be replaced by shrubland or dunes and a brackish lagoon. That notwithstanding, it is well possible that a
Polynesian sandpiper related to or identical with the
Christmas sandpiper from
Kiritimati once lived on Teraina.
Other fauna As with most outer Pacific islands, there are no native land
mammals. Polynesian rats (
Rattus exulans) are present on Teraina, apparently since prehistoric times. They may have arrived with flotsam after storms further west, or accidentally or deliberately (as food) been introduced by prehistoric seafarers. Their present-day impact on the bird population is minor, but if
rails were once present on Teraina, the rats had probably some role in these birds' disappearance, and maybe in that of any other birds gone extinct in prehistoric times too. If a Polynesian sandpiper once bred on Teraina, it is almost certainly those rats that are responsible for these birds' disappearance; only a single
taxon of
Prosobonia remains today, precariously holding its own on atolls that are devoid of any rat species. is also found in Teraina's lake.
Feral dogs,
cats and
pigs occur in varying numbers on Teraina; the cats especially are responsible for some decline in the number of ground-nesting seabirds. On the other hand, as noted above, the cats have thus far kept the rat population at bay.
Lacustrine species reported from Teraina include
fish. and some unspecified "
shrimp", i.e. (in all probability) a member of the
Crustacea. Teraina's freshwater fish include the marbled eel (
Anguilla marmorata), a
Caranx freshwater
trevally, and
Oreochromis tilapias and the milkfish (
Chanos chanos). The latter two, and perhaps also the trevally, were introduced in recent times. The eels were already established by 1877; like many
Anguillidae they are
catadromous and able to migrate some distance on dry land. Thus it may be presumed that the lake is continuously being restocked from the Pacific, though apparently no actual field data exists on the habits of the eels of Teraina. As on many
Indopacific islands rich in coconut (
Cocos nucifera) trees, the coconut crab (
Birgus latro) is often encountered on Teraina. A few green turtles (
Chelonia mydas) nest on the beaches. It is not a very important nesting site however and the
clutches have a rather low probability of success, as Teraina is one of the Kiribati islands where turtle egg collecting is permitted. == See also ==