First conclusive evidence of Jackson’s chameleons feeding on Hawaiian insects and snails.
It’s official, the paper documenting native Hawaiian insects and snails from Jackson’s chameleon stomachs has been published in the online version of the journal “Biodiversity and Conservation.” The title is: “A reptilian smoking gun: first record of invasive Jackson’s chameleon (Chamaeleo jacksonii) predation on native Hawaiian species”, and the authors are Brenden S. Holland, Steven L. Montgomery, and Vincent Costello. (I think the date of publication is 25 December 2009, but you have to look in the “online first” section to find the paper.)
You can see the abstract for free at the Biodiversity and Conservation website, but if you want to read the entire paper, then you have to pay $34.00. I was a little surprised they included a head shot of a dead male Jackson’s in the paper. If there is ever any kind of a depredation program to keep these guys out of native forests, I suspect it will be met with fierce opposition by many folks who have a strong affinity for the cute little beasts. They have kind of become a Hawaiian icon – maybe not quite like the gecko, but they do have a certain status in Hawaii. In light of this, I would hope the Hawaii environmental and conservation community proceeds with caution and tries to exercise some good PR along the way. I don’t think a picture of a dead chameleon sends the right message, but then again its a research paper, not a community bulletin, so it’s probably not a big deal. I guess I am somewhat guilty of the same offense by calling them “killers” in one of my blog entries. Anyway, gruesome picture notwithstanding, I give these guys kudos for getting the paper out. I know both Steve and Vince fairly well and they are both really good guys and extremely good field biologists.
And now a little teaser from their paper (the last two paragraphs of the discussion):
“Much remains to be determined in terms of making an accurate assessment of the threat posed by Jackson’s chameleons in Hawaii, and further work is planned. For example, little is known about their precise range, elevation preference, reproductive season and rate, desiccation tolerance, and prey preference. Jackson’s chameleons occur in lower to mid elevationnon-native forests on Oahu, and have rarely been reported from tree snail habitat, which tends to be upper elevation dominated by native flora beginning around 600 m above sea level. The observations presented provide conclusive evidence that when chameleons are present in native forest where tree snails and other endemic invertebrates occur, they pose a threat.”
“It is possible that due to a number of factors, such as prey availability and distribution, changing climatic conditions, recent population establishment due to pet release or escape, Jackson’s chameleons are undergoing a range expansion into upper elevations. This is a concern for a variety of threatened and endangered invertebrate species, including tree snails (Achatinella spp.), pomace flies (Drosophila spp.) , rare damselflies (Megalagrion spp.), and rare amastrid and succineid land snails, all restricted to upper elevation forests such as Mt. Kaala Natural Area Reserve adjacent to the sampling locality. Prior to this discovery, as part of an ongoing collaborative study, one author (BSH) has collected several hundred chameleons, and gut contents are being examined from populations in the Round Top/Tantalus area of the Koolau Mountains, Honolulu, on eastern Oahu (Whiting et al. in prep). Endangered Oahu tree snail species have not been observed in this region in several decades. It is conceivable that predation by Jackson’s chameleons may have played a role in the local extinction of Achatinella spp. in this area.”