Coqui Frogs in Hawaii

Here on the Big Island of Hawai'i, the Coqui Frog has taken hold, especially at the lower elevations on the East side. Many areas of Puna, Hilo, and Hamakua have become inundated with the incessant night time chirping.

Hawai'i's lush vegetation, warm temperatures and high humidity not only welcome human visitors but indiscriminately provide a tropical paradise for the more than 1,000 alien plants, vertebrates, and invertebrates that have been accidentally introduced from all corners of the world over the past 65 years. Some have become established at the expense of native species, competing for habitat and nutrient sources.

One species that has garnered much attention recently is the coqui frog, Eleutherdactylus coqui. Its ability to quickly adapt to Hawai'i from its native Puerto Rico and reach unprecedented numbers, the absence of predators, and its noisy mating behavior have made the coqui frog the target of government and community eradication and control efforts.

Why Are Coqui Frogs a Problem in Hawai'i?

The coqui frog, Eleutherodactylus coqui Thomas (Anura: Leptodactylidae), was accidentally introduced into Hawai'i from Puerto Rico in about 1988. Aside from being a major noise nuisance, the frogs pose a threat to Hawai'i’s island ecosystem. Coqui frogs have a voracious appetite that puts Hawai'i’s unique insects and spiders at risk. They can also compete with endemic birds and other native fauna that rely on insects for food. The frogs are quite adaptable to the different ecological zones and elevations in the state and have been found from sea level to 4,000 feet elevation (at sites in Volcano on Hawai'i). Scientists are also concerned that an established coqui frog population may serve as a readily available food source if (or when) brown tree snakes are accidentally introduced in Hawai'i.

Coqui populations have exploded in the last 15 years from presumably a single infestation to over 200 on the Big Island alone. They are also present on Maui (40 or more infestations), O`ahu (5 sites) and most recently on Kaua`i (1 site, subject of an eradication effort with citric acid in June 2003). Puerto Rico averages 40 frogs (reproductively mature adults, not including juveniles) per 20 x 20 m plot compared to > 200 in Big Island plots, primarily because of the lack of predators (owls, snakes, tarantulas, scorpions) in Hawai'i.

The Life Cycle of a Coqui Frog

Coqui frogs belong to a genus of frogs that do not have a tadpole stage and therefore do not require a body of water to reproduce. Instead, the female lays the eggs on damp moss or leaf litter, or inside a rolled or folded leaf, and the eggs are brooded by the male, who keeps them moist until they hatch.

Coqui Eggs 8 Days Old At first, the eggs look white to off-white and opaque, about the size of large tapioca pearls. As they mature, the eggs enlarge, darken and become transparent, resembling papaya seeds, with the frog embryo visible inside. When the tiny froglets hatch in 14-17 days, they are about ½ inch (5 mm) long.

In its native Puerto Rico, the female coqui frog usually lays a cluster or clutch of 34-75 eggs four to six times a year; however, under laboratory conditions in Hawai`i, mating pairs produce a clutch every 2½ weeks without loss of fertility – that’s 26 clutches a year, or more than 1,400 eggs per female per year! It takes about 8 months for froglets to mature. Adult coqui frogs may live as long as 4-6 years.

A Homeowner's Guide to Coqui Frog Control

FIRST, KNOW YOUR ENEMY:

    * Coqui do NOT breed in water. They have no tadpole stage. The eggs are laid on land and they hatch out as tiny frogs. Remember, they are tree frogs.
    * The males are the singers. If you hear only one frog, that doesn't mean you have only one frog. It just means you have only one male. That situation will change shortly, and soon you'll have hundreds of males.
    * At dusk (or earlier if its overcast), the males climb your trees and start singing. The females will climb up for mating.
    * Daytime hangout is anywhere there is cover: tall grass, under fallen leaves, logs, rubbish, etc.

SECOND, CLEAN UP YOUR ACT:

    * Cut your grass on the lowest mover setting and rake it up.
    * Rake up the fallen leaves. Broadcast hydrated lime on your lawn to sweeten the soil and   discourage the frogs.
    * Take all that stuff laying around outside and haul it off to the dump: flowerpots, PVC;   anywhere a frog the size of a dime can hide. You've probably been meaning to do this anyway.

THIRD, MAKE THEM COME TO YOU:

    * Sure, you can tromp around for hours trying to locate one of the little buggers, and work up a great deal of frustration, or you can lure them to you. Make a recording of their call. Place a speaker up high outside your door where your night light will illuminate the action. Lean a log from the floor to the speaker. At night, play the recording. The females will flock to your speaker, and you can pick off the little hussies.

FOURTH, STICK IT TO THEM:

    * Identify the trees harboring males. At eye level, wrap the trunks in fly paper. You'll catch both sexes and can pick them off. The fastest way to kill the caught frogs is to step on them. If that's too violent for you, freeze them or put them in a jar and lime them or pour boiling water on them. Pau frogs!