Beloved in Puerto Rico, the coin-sized coqui frog’s loud chirps have become so widespread on Hawaii island that eradication in some areas has been abandoned. But the critters’ presence might be growing on Oahu, and serious efforts to eliminate them are needed to prevent devastation of tourism and property values.

The quarter-sized frogs arrived in Hawaii in the late 1980s, apparently by ship, and by 2002 had spread throughout Hawaii island and begun arriving in the other islands.

By this year, densities had reached 224,000 frogs per acre in some natural areas of Hawaii island, according to the Coordinating Group on Alien Pest Species.

The coqui frogs’ loud "ko-kee" chirps at night have discouraged some visitors from renting accommodations in some areas of the island, said Lori Buchanan, acting manager of the Big Island Invasive Species Committee.

Just as many reports of coqui were made on Oahu last year than the seven prior years combined, which is a disturbing development.

The Oahu Invasive Species Committee is asking people on the island to go outside their homes for 15 minutes from 7:30 to 8 p.m. Wednesday and listen for the coqui’s distinctive mating call. They should report their findings to 643-7378, oisc@hawaii.edu or via the free Honolulu 311 smartphone app (download the app at can-do.honolulu.gov/apps/14).

Vigilance is indeed crucial, as the coqui frogs go beyond being a noise nuisance. They are an invasive species that is gradually altering the ecosystem of Hawaii island as they eat mites, ants and other bugs, scientists say.

They cause economic damage, too: In 2005, the presence of coqui became a disclosure requirement in real estate transactions on Hawaii island, with real estate values dropping within 500 meters of frog infestations.

Since 2008, the coqui has been reported throughout Oahu, including Waikiki and the Diamond Head neighborhood. Rachel Neville, manager of the Oahu committee, said it receives about three reports a month, and group employees are sent out to capture the frogs. The group has been able to help eradicate them in Wahiawa and Hauula, but more can be expected.

"Some of them come over in plants," Neville told the Star-Advertiser’s Gary T. Kubota. "They come over in cars and trucks. The reality of the situation is that they’re being constantly introduced into the island."

Unfortunately, many coqui have been found in recent years close to the base of Oahu’s forested mountains, where they can multiply away from being heard. Hawaii has no natural predators to halt their steady advance onto Oahu and must depend on eradication teams to mimic their mating call and trap the frogs with a clear tube when they come near or, in a few cases, kill groups of frogs with citric acid.

The coqui’s numbers have grown on Oahu as the recession-caused budget cuts reduced cargo inspectors from 95 to 50. Gov. Neil Abercrombie has restored 10 inspectors, a good restart to help keep the frogs from arriving in cargo through what could be a critical period.

The abandonment of some areas of Hawaii island that have become dense with coqui should sound an alarm on Oahu.

Next week’s attempt to organize findings on Oahu should be the first of numerous "Go Out and Listen Nights," leading to the coqui becoming an extinct species on this island.