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Coqui calls on the rise

Posted on November 20, 2014 by Lissa Strohecker

A male coqui guards a clutch of eggs inside a pipe. With coqui populations on the rise throughtout the state there is an increased likelihood of coqui inadvertently reaching Maui. MISC file photo

A male coqui guards a clutch of eggs inside a pipe. With coqui populations on the rise throughtout the state there is an increased likelihood of coqui inadvertently reaching Maui. MISC file photo

The call of the lone coqui may not be increasing in volume, but calls reporting coquis on Maui are on the rise.

There’s been a dramatic increase in coquis arriving on Maui. In 2013, 25 Maui residents reported the presence of these noisy amphibians, almost double the reports from 2012 and 2011 combined. And the trend seems to be continuing for 2014, with reports of these invaders popping up in surprising places across Maui.

Coqui frogs are known to be in a handful of scattered populations around the island. According to the Maui Invasive Species Committee, all are under control and on target for eradication, with the exception of Māliko Gulch in Ha‘ikū. But the influx of new arrivals has the MISC crew concerned.

“We interview homeowners when there are new frogs reported, but we haven’t found any clear source of introduction,” said MISC Operations Manager Adam Radford. “In general, there are more frogs in the state than there used to be.” As coquis increase in number, particularly on Hawaii Island, so do the chances that the notoriously loud hitchhikers will spread elsewhere.

If you have heard a coqui, you know why they are not a welcome addition to your neighborhood. A single male frog has an 80- to 90-decibel screech, as loud as an alarm clock or freeway traffic. The frogs call from dusk until dawn. Coquis arrived in Hawai‘i sometime before 1988. In the absence of predators or competitors, their numbers ballooned, reaching densities exceeding 36,000 frogs per acre – two to three times greater than in their native range in Puerto Rico.

The coquis’ ear-splitting chorus may be the most obvious impact of this invasive species, but recent research suggests there are secondary, less-apparent consequences to allowing these quarter-sized pests to become established. Researchers have long known that coquis eat invertebrates such as insects, spiders and worms, but they recently discovered how these invasive amphibians skew the ecosystem in Hawai‘i.

What goes in must come out. The coqui frogs’ most significant change to the landscape is through the increased nutrient input from their droppings. While this sounds like a good thing, altering nutrients can create an environment more hospitable to non-native species.

This coqui was discovered by an observant Maui resident, hiding in a potted plant recently purchased from a garden shop. MISC file photo.

This coqui was discovered by an observant Maui resident, hiding in a potted plant recently purchased from a garden shop. MISC file photo.

Researchers found increased leaf production rates in invasive strawberry guava in coqui-invaded sites compared to other sites. Plants native to Hawaii evolved in nutrient-poor conditions, so increased nutrient input favors non-native plants. Additionally, scientists found a greater number of insects in the order Diptera (flies) associated with coqui-invaded areas, the outcome of more excrement and more coqui carcasses.

Unfortunately, the coqui frog is widespread on Hawai‘i Island and cannot be eradicated. There, residents work together to control frogs in individual neighborhoods, and nurseries bathe plants at a hot water treatment facility before shipping stock off island. Barriers around parking lots prevent frogs from moving between cars and the areas surrounding the lot. But in the big picture, these stop-gap measures only will provide a temporary respite. We can prevent this from happening on Maui. With only one significant population in Māliko Gulch, land managers believe that the frogs can be eradicated, and new infestations thwarted.

You can help. Report coqui frogs to the Maui Invasive Species Committee at 573-6472. Support business and landscapers who take steps to prevent the spread of coquis via the plant trade. And, find a list of certified coqui-free businesses at coquifreemaui.org. For more detailed information about recent research on impacts of coqui, check out the coqui frog information page under priority pests at mauiinvasive.org.

By Lissa Fox Strohecker. Originally published in the Maui News, August 10th, 2014 as part of the Kia‘i Moku Column from the Maui Invasive Species Committee

Filed Under: Invasive Animals, Kia'i Moku Column Tagged With: 2014, coqui frog, coqui-free certification, maliko coqui, Maui coqui

A most unwanted neighbor–coqui frogs

Posted on October 27, 2011 by Lissa Strohecker Leave a Comment

A coqui frog hiding on a landscape plant

A coqui frog hiding on a landscape plant

A recent trip to Hilo highlighted the impact coqui frogs can have on our quality of life. It was not just the chorus heard throughout town and in my hotel room, but the fact that they could be heard while having dinner, enjoying a beach park and hiking through native forests. They’re everywhere. Recent estimates indicate that coqui have infested more than 60,000 acres of East Hawaii, from the ocean to 4,000 feet in elevation. With Hawaii County now planning to liquidate its coqui-control equipment, this noisy neighbor seems to have become a permanent resident on the island of Hawaii.

My work creates many opportunities to talk about coqui, and I am often asked why they are perceived as a nuisance in Hawaii when they are beloved in their native home of Puerto Rico.

One consideration is that they have no natural enemies here and can reach population densities more than twice that of their native range. This may cause significant problems for native insects (which they eat), change soil composition to the benefit of non-native plant species and compete with Hawaii’s native birds for food. Possible economic impacts in infested areas include diminished property values and sales, a change in the quality of visitor experiences due to their persistent nocturnal calls and decreased sales in the floriculture and nursery industry.

During my short visit to Hilo, I learned that a colleague with deep ties to Hawaii agriculture was facing the prospect of moving and foregoing personal professional opportunities, primarily because of the coqui. These experiences strengthened my motivation to keep coqui from becoming widely established on Maui.

Signage indicating the coqui-free status of a local business.

Signage indicating the coqui-free status of a local business.

Coqui are believed to have been introduced to Hawaii by hitchhiking on plants or associated products in the late 1980s. Since then, coqui have shown up on most of the main Hawaiian Islands, in California, and Guam on plant shipments. This is still the primary avenue for dispersal, particularly from heavily infested areas. To help minimize the risk of introducing coqui to your neighborhood, the Maui Invasive Species Committee started a coqui-free certification program. The voluntary program encourages plant industry participants to adopt specific practices to reduce movement via the nursery trade. If you see a business designated as “coqui-free,” you can feel confident that you will not be purchasing coqui along with your plants or plant products.

Like the Big Island, Maui has coqui. Unlike the Big Island, Maui has only six infested areas, which cover an estimated 227 acres. Eleven population centers (areas with five or more calling males) have been removed since 2004. Five others have very low numbers of coqui. Really, only one substantial population remains. Maui has kept populations from becoming established by quickly responding to reports of new coqui locations. Although new introductions from infested areas are a constant concern for Maui residents, quickly identifying and capturing a few rogue males typically prevents a couple of coqui from becoming thousands. Left unchecked or unreported, coqui populations on Maui would be sure to rival East Hawaii at some point.

Citric sprinkler

The author preparing a large-volume sprinkler for citric acid delivery.

In Haiku, for example, an area that once had low numbers of coqui has now spilled over into a steep-sided gulch. Efforts have begun to remove coqui from the 225-acre area by applying a 12 to 16 percent solution of citric acid (a food additive). But challenging terrain and trying to work at night (when coqui are most active) have demanded the development of creative citric application tools. These include fixed-line sprinklers, high-volume sprayers and even limited use of a helicopter in inaccessible areas. Although daunting, successful control efforts over the last four years have shown that the key to preventing coqui from permanently establishing is early detection of new locations, repeated systematic treatment of known populations and removal of frog-friendly habitat.

Unfortunately, even the combined resources of state and county agencies on Hawaii, as well as regular outings by community-based coqui control groups, have been no match for the coqui.

On Maui, we only have one large population left. We still have a strong chance to become and remain coqui-free. Please help by calling the Maui Invasive Species Committee at 573-MISC (6472) if you happen to hear a coqui frog.

More information about the coqui-free program can be found at www.coquifreemaui.org.

Adam Radford is the operations manager for the Maui Invasive Species Committee. He manages MISC’s efforts to control invasive plants, animals, and banana bunchy top virus.

Originally published in the Maui News, March 14, 2010 as part of the Kia‘i Moku Column.
You can find all the articles in the Kia‘i Moku series
http://www.hear.org/misc/mauinews/

Filed Under: Invasive Animals, Kia'i Moku Column, MISC Target Species Tagged With: 2010, coqui frog, coqui-free certification, invasive animals, maliko gulch

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