June 21, 2010
Scientists Discover Unusual Rhino Beetle Behavior
Invasive species severely impact small islands
Russ Campbell, Guam's territorial entomologist and Aubrey Moore, UOG extension entomologist, welcomed New Zealand scientist, Trevor Jackson to Guam in early June. Jackson was invited to assist in the release of a virus into the rhino beetle (Oryctes rhinoceros) population. This virus only infects rhino beetles and it has been successful in controlling populations of the pest on other Pacific islands.
Aubrey Moore and his assistant Bob Bourgeois are been rearing rhino beetles individually in mason jars in order to have healthy beetles to infect with the virus. Hungry beetles are taken to the Guam Plant Inspection Facility, fed the virus, and then strategically released into island rhino populations. Once the beetles are infected, the virus damages their stomach walls causing them to stop eating.
During Jackson's visit the team discovered unusual rhino beetle behavior: the beetles were not breeding on the ground in decayed logs as normal; they were breeding in the detritus trapped in the tree branches. In cutting down 11 large coconut palms they found a complete ecosystem in the crowns including brown tree snakes, crabs, and, unfortunately, all life stages of rhinoceros beetles, from eggs to larva to young adults. This new discovery makes the release of the bio-control virus even more vital. Moore thinks this arboreal breeding behavior, seen only on Guam, may be due to the fact that the brown tree snake has wiped out most of Guam's rats. Elsewhere, rats love to live in coconut crowns, and they love to eat rhino beetle grubs.
This never-before-seen rhino beetle behavior of breeding in the crowns of coconut trees underscores an important point of invasive species on small islands. Their impact is often severe because there are no natural enemies, such as predators, parasites, or diseases, to control their population growth.
Image 2: Dr. Aubrey Moore administers a bio-control virus to a rhino beetle. Credit: Herman Crisostomo
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