I had previously posted the following query: "We are interested in trapping invasive Jackson's chameleons in the wild, any ideas?" We want to control/eliminate chameleons from native habitat. As a follow-up, I had an idea. The ‘io was listed as an endangered species in 1967 under the Federal Endangered Species Act because little was known about this species and raptors worldwide were experiencing significant declines. Today they are only known to breed on Hawaii Island, though historically had a wider distribution including multiple islands. Thinking about the recent rebound of endemic Hawaiian Hawk populations on the Big Island, it occurred to me that if we could release a handful of these birds on Oahu, we could potentially accomplish re-establishment of this endangered species and possibly bring a native Hawaiian predator over to control an ecologically damaging lizard. Raptors constitute major natural predators of chameleons in eastern Africa, as well as other regions.
Brenden--This sounds theoretically plausible (and I'd love to see lots of 'io on Oahu and fewer Jackson's chameleons), but could we ever expect to see enough 'io here to really make a difference in the chameleon population? How great a percentage of an 'io's diet would be chameleons? A wonderful thought, but I'm a bit skeptical about its practicality.
Yes, natural controls are preferable, but you need to carefully assess how reintroduction of even a native species could perturb the existing foodweb - what if the 'io spurned seeking out camouflaged chameleons and targeted birds, mammals or other lizards instead. Then, while you might have a flourishing population of 'io, the chameleon would remain and a host of existing species would be threatened. However, investigating the 'io foodweb on Hawaii Island might shed light on introduction outcome on Oahu.
Hawaii has no native land mammals (except a bat, which occurs on Hawaii and Kauai but is extinct on Oahu) and no native lizards, so predation on them would not be a problem. Fossil evidence indicates that the 'io did once inhabit Oahu, so re-establishing a population here would not result in the creation of an unnatural condition.
Perhaps not an 'unnatural condition', but Oahu's ecosystem has evolved and adapted since the 'io disappeared. Reintroductions can result in cascade effects beyond simple predator-prey relationships - one of the reasons why reintroductions are often beset by problems. Though Oahu has no native mammals, the mammals that exist there now are integrated into the ecosystem, so the effects of introductions must be assessed on all elements of the foodweb, not just those that are deemed to belong there.
Interesting points and concerns, though whether rats, cats, Indian mongoose, and other common established invasive mammals in Hawaii's native forests, that could potentially serve as prey species for 'io are considered "integrated into the ecosystem" is debatable. True though that "things can always get worse". But either way, rather than this being the primary concern, I think that since 'io evolved as a bird predator, to me the Oahu populations of the endangered elepaio would be the major concern, since they are already under stress from the usual suspects: habitat loss and degradation, avian malaria, and predation by cats and mongoose. The "hope" might be that since introduced birds of similar size to natural prey of 'io are more abundant, that 'io would further assist in restoration of forest community balance by knocking down these population levels. We see FAR more nonnative birds in the field than native, and a number of these species have been shown to be direct competition for the Hawaiian forest birds. But to the point that 'io might eat a few chameleons, but may not control them, I agree, but let's say 'io becomes reestablished in the process (+), controls nonnative birds (+), rats (+), and mongoose (+), add in your favorite of the 32 species of non-native herpetofauna (+!). Could be some value, but prediction of outcomes is the tricky part!
Hi Brendan, They are recently trialling methods of biocontrol using hawks in the Canary Islands (Gran Canaria Is.) to control for the invasive Californian King Snakes. They are not sure yet if it will be successful, but the people involved are http://www.lifelampropeltis.es/
and here's a link to the IUCN pdf with more info on the problem: https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCoQFjAA&url=http%3A%2F%2Fwww.issg.org%2Fpdf%2Faliens_newsletters%2FA32.pdf&ei=p_U0U4_XBJCclQWCi4GQCg&usg=AFQjCNHPuJ32-xY8HNffrNxw_NYgPU0xOQ&bvm=bv.63808443,d.dGI
Maybe contact them for more info.
Cheers,
Melissa
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