DEVIL WEED (Chromolaena Odorata)
What and Why: Devil weed is considered one of the world’s worst 100 invasive species according to Oahu Invasive Species Committee (OISC), and is thought to have the potential to be extremely invasive to Hawaiʻi. The plant’s name comes from its leaves, which have three veins that look like a pitch fork. The shrub has pale purple, triangular shaped leaves with toothed edges. When crushed, the plant has a distinct smell of turpentine. The spread of this invasive plant is exacerbated by its tiny fruits, which have soft white hairs that can easily be carried by the wind and water, or eaten and spread by birds. The hairs may also attach themselves like Velcro to passing animals, including human hikers.
Like many invasive plants, devil weed can take over areas and impede the growth of native species by shading them out and releasing toxins into surrounding soil. Soil and watershed quality are negatively impacted.
Where: First detected in Kahuku Training Area in 2011, devil weed has since been found in other locations around Oʻahu, including Kahana Valley, Pūpūkea and ʻAiea. OISC’s management goal for devil weed is island-wide detection and eradication.
What and Why: The population of endemic waterbird and migratory waterfowl in the Hawaiian Islands has been greatly impacted by the more frequently occurring outbreaks of avian botulism. Avian botulism is in fact a food poisoning that the birds experience from ingesting large amounts of invertebrates that carry concentrated amounts of the bacteria Clostridium botulinum (strain C). Once a waterbird ingests enough of the toxin, the bird becomes paralyzed and eventually drowns or starves.
Avian botulism can spread quickly within a bird population via the “carcass-maggot cycle” if affected carcasses are not removed from the environment quickly. If a bird carcass remains in the environment long enough for flies to lay eggs in it, then maggots develop and bio-concentrate the toxin that comes from that carcass. Fish and invertebrates in the wetlands can also accumulate the toxin and cause botulism in the waterbirds that eat them.
With the changing climate, it is thought that avian botulism will increase globally because the bacteria Clostridium botulinum (strain C) thrives in warmer water temperatures. Many of Hawaiʻi’s native waterbirds are already at risk of extinction, and avian botulism will only add to their plight.
Historically, wildlife refuge staff and volunteers have worked hard to quickly remove carcasses from their wetlands, but often the carcasses are located in areas of thick vegetation, making them hard to detect in a timely manner. Our goal is to assist the wildlife refuges via canine/olfactory surveys, especially in thickly vegetated areas that may prove challenging for visual surveys. In 2017-2018 our lead K9 trainer participated in a USGS-led study on the efficacy of using detector dogs to survey for avian botulism. While the study results have not been officially published yet, we believe based on experience that canine surveys can complement human/visual surveys quite well, and contribute to a more thorough overall surveillance effort to prevent and respond to botulism outbreaks.
Where: We have assisted and are on call to assist Hanalei National Wildlife Refuge (Kauaʻi) with botulism surveys. Our lead K9 trainer has also conducted botulism surveys at James Campbell National Wildlife Refuge (Oʻahu). Avian botulism has occurred on all the major Hawaiian islands, including Kauaʻi, Big Island, Maui, and Oʻahu, as well as on Midway Atoll. Our goal is to have trained dog/handler teams on standby to deploy to all locations, either for preventive surveys or outbreak response.
What and Why: More information coming soon…
Where: Kahuku Point, Oʻahu
ROSY WOLFSNAIL (Euglandina Rosea)
This volunteer pilot project was cancelled due to our determination that dogs are not effective tools in detecting these snails by scent. Read Working Dogs for Conservation’s report from their 2009-2010 feasiblilty project, which reflected similar findings.
What: According to the Global Invasive Species Database (issg.org), Euglandina rosea is considered one of the world’s 100 worst invaders. The presence of Euglandina rosea has been strongly linked to the extinction and decline of numerous snail species in every area where it has been introduced. Due to its voracious and predaceous appetite the rosy wolfsnail is a fierce invasive gastropod that can severely threaten native gastropods. They consume smaller gastropods such as the native Hawaiian snails (Pūpū kuahiwi) which dubs them the “the cannibal snail.”
Why: To support the population growth of native Hawaiian tree snails by preventing the cannibal snails from predating on them. Native snails (Pūpū kuahiwi) evolved here in Hawaii and are found nowhere else in the world. These unique snails don’t even eat plants. They eat algae that grow on the leaves of trees. Pūpū kuahiwi take about five years to reach maturity, whereupon they produce one to seven live offspring a year. They also tend to live on or beneath a single tree, which heightens their vulnerability to predation and habitat change.
In contrast, the rosy wolfsnails feed exclusively on other mollusks and reach maturity in one year. The rosy wolfsnail lays 25 to 45 eggs annually and is highly mobile and quick, thereby vastly outstripping the reproductive rate and range of the Pūpū kuahiwi.
Read more about the endangered Hawaiian snails and the challenges they face in this article.
Where: While rosy wolfsnails may be found throughout the islands, the target areas include the predator exclosures that provide habitat for the endangered Hawaiian tree snails.