WASHINGTON (Reuters) - People living on the Solomon Islands in the Pacific Ocean long had spoken of a big, tree-dwelling rat called vika that inhabited the rainforest, but the remarkable rodent managed to elude scientists -- until now.

An illustration of a new species, Uromys vika is shown in this illustration provided September 28, 2017. Courtesy Velizar Simeonovski/The Field Museum/Handout via REUTERS

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 Solomon Islands, spotting one as it emerged from a tree felled by loggers.

It instantly joined the list of the biggest rats in the world, weighing about four times more than an ordinary rat and measuring about 1-1/2 feet (about half a meter) 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 on Thursday.

The orange-brown rat dines on nuts and fruit, 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 thick-shelled 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 Solomon Islands, called Poncelet’s giant rat, is twice the size.

The world’s largest rodent is not a rat, but rather South America’s barrel-shaped 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,” Lavery said.

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

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