Large tree­dwelling rat found in Solomon Is­lands

Otago Daily Times - - World -

WASHINGTON: Peo­ple liv­ing in the Solomon Is­lands long had spo­ken of a big, tree­dwelling rat called vika that in­hab­ited the rain­for­est, but the re­mark­able ro­dent man­aged to elude sci­en­tists — un­til now.

Af­ter search­ing for it for years with cam­eras mounted in trees and traps, sci­en­tists said they fi­nally caught up with the rat on Van­gunu Is­land, part of the Solomons, spot­ting one as it emerged from a tree felled by log­gers.

It in­stantly joined the list of the world’s big­gest rats, weigh­ing about four times more than an or­di­nary rat and mea­sur­ing about half a me­tre long.

‘‘Vika lives in a very thick, com­plex for­est, and it is up in the canopy so it is dif­fi­cult to find. It is also a rare species. It is likely there are not many of th­ese rats left,’’ mam­mal­o­gist Ty­rone Lav­ery of the Field Mu­seum in Chicago, who led the re­search, said yes­ter­day.

The or­ange­brown rat eats nuts and fruit. It has short ears, a smooth tail with very fine scales and wide feet that al­low it to move through the for­est canopy.

The rat is re­puted to chew holes in co­conuts to eat the in­side. ‘‘I haven’t found proof of this yet, but I have found that they can eat a very thick­shelled nut called a ngali nut,’’ Lav­ery said.

A small number of rat species around the world ri­val vika’s size. Lav­ery said a vika rel­a­tive also in­hab­it­ing the Solo­ mon Is­lands, called Pon­celet’s gi­ant rat, was twice the size.

The world’s largest ro­dent is not a rat, but South Amer­ica’s bar­rel­shaped capy­bara.

A phe­nom­e­non called the ‘‘is­land ef­fect’’ may help ac­count for the size of vika and other big rat species in the Solomon Is­lands.

‘‘The is­land ef­fect, or is­land syn­drome, re­lates to the ef­fects liv­ing on an is­land has on the evo­lu­tion of body size. On is­lands, small species such as rats, evolve to have larger body size, they at­tain higher pop­u­la­tion den­si­ties and they pro­duce fewer off­spring,’’ Lav­ery said.

‘‘Vika also prob­a­bly ar­rived on an is­land where there were no other large mam­mals liv­ing in the canopy eat­ing fruits and nuts so the species evolved to fill this niche.’’

Vika should be con­sid­ered crit­i­cally en­dan­gered, with log­ging threat­en­ing its habi­tat, Lav­ery said .

The re­search was pub­lished this week in the Jour­nal of Mam­mal­ogy. — Reuters

PHOTO: REUTERS

An il­lus­tra­tion of a new species, Uromys vika, that has been found liv­ing in trees in the Solomon Is­lands.

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