The Science of Snakes and Frogs: Invasive Species in Hawaii

by Rosalinda Villegas, age 15

Many residents in Oahu, Hawaii are kept up at night by a thunderous roar of chirps. The chirps are mating calls from male coqui frogs. Some residents say the chirps can be as loud as a jet.

The coqui population has been growing recent years, making the island of Oahu home to most of the state’s frog population. The frog population in Oahu began to grow when the frogs started sneaking onto cargo pallets and stowing away in cars from Hawaii.

In 2011 there were as many sightings of coqui frogs on Oahu as the previous seven years combined. Before, there were many sightings, Derek Arakaki and two others on the coqui eradication team would go capture the frogs on Oahu once or twice a month. Last year, there were times when they had to go coqui hunting twice a week.

Oahu residents fear the frog’s chirps will stop tourists from visiting. Hawaii is not home to any natural predators to stop the coquis from advancing, which leaves all of the work to the eradication team. The team finds the frogs by mimicking the males’ mating call, making them call back and easier to find. Once they find the frogs, they trap them in a clear tube. There have been some occasions when the team captured so many that they had to kill them with citric acid, the most commonly used chemical to kill the frogs.

In the Oahu town Hauula, the coquis were spreading across several homes and a city park. Residents heard their calls, but did not report them to pest control experts, thinking the cries were from birds. By the time they called the pest control, the frogs had multiplied. Now they have been breeding for two years.

In Oahu, a recession-induced budget cut forced the state to reduce the number of cargo inspectors from 95 to 50. Since the state made that cut, the agricultural department prioritized checking out-of-state cargo. This is because imports are more likely to have harmful species, like snakes.

Snakes are a problem in Hawaii because they could wipe out Hawaii’s native endangered bird species. A dozen snakes were captured last year in only 6 months. Carol Okada, an agriculture department plant quarantine manager says, “There’s a reason why all the snakes are coming out this year. We’re not out in force anymore.”

Once the state cut down the number of cargo inspectors, the problem of the snakes and frogs started to grow, making it harder to stop their advance.

[Source: Associated Press]