12/19/2023 0 Comments Are there lots of snakes in guamNo sexual size dimorphism in relative tail length or width has been reported, though male Brown Tree Snakes often achieve a larger total length than do female Brown Tree Snakes ( Savidge 1991, Rodda et al. This proportion is intermediate among snakes and relatively short compared with most arboreal snakes ( Guyer and Donnelly 1990). Rodda)īrown Tree Snakes have tails that average 21% of their total length. 2006).Ī juvenile Brown Tree Snake from Guam, showing the Guam population's characteristic shade (light/medium brown) and vague black banding, as well as the species' characteristic defensive pose, short snout, and large eyes. Toxicity varies greatly among prey species, with select birds and lizards being highly susceptible to neurotoxic elements of the venom ( Mackessy et al. Compared with the copperhead, however, the Brown Tree Snake lacks a means for injecting the venom (only capillary action conveys the venom into prey). 1991, 1993), though it overlaps with the toxicity of that of species considered dangerous (e.g., North American Copperheads, Agkistrodon contortrix). The venom is relatively mild for humans ( Weinstein et al. 1992, 1993, Jackson and Fritts 1995, Mackessy et al. The teeth are of moderate length, the upper rearmost of which are enlarged and grooved to facilitate penetration of venom into prey ( Vest et al. The snout is short and the eyes are large, with the elliptical pupil characteristic of nocturnal species ( Figure 1). Any hole that will admit a Brown Tree Snake's head will allow passage of the entire snake (unless a very large meal has recently been ingested). For a snake of this length, the head size is actually normal, but the body is extraordinarily slender ( Rodda et al. The Brown Tree Snake conveys the impression of having a large head in relation to the diameter of its neck and body. The species name irregularis recognizes the diversity of morphology in the species. As currently recognized, Boiga irregularis includes all of the closely related brown Boiga found east and south from Sulawesi to Australia and the Solomon Islands (see a later section on Geographic Distribution), though various proposals have been suggested to recognize locally distinctive forms. The easternmost representative of this Asian radiation is the Brown Tree Snake. The genus Boiga is an Asian radiation of slender rear-fanged snakes, with 33 described species (EMBL Web site accessed 31 January 2006: ) insofar as it is known, all members of the genus are nocturnal and all but one are arboreal. A cluster of similar genera is sometimes characterized as the subfamily Colubrinae (formerly placed in Boiginae). The Brown Tree Snake is one of about 1,800 species of modern snakes lumped into the poorly resolved and presumably polyphyletic family of “typical” snakes: Colubridae. Our favorite is northern Australia's “Doll's Eye,” which recognizes the disproportionately large eyes of this species, especially when it is young ( Kinghorn 1964). Ultimately, all Pacific islands are at risk but especially those obtaining cargo through Guam.īoiga irregularis is most often called the Brown Tree Snake, though a variety of names are in local use ( Rodda et al. Cargo destinations most at risk are in Micronesia, especially the Northern Mariana Islands, but Guam also has direct air transportation links to Hawai‘i that will soon be supplemented with direct ship traffic. government annually spends several million dollars inspecting cargo outbound from Guam to exclude Brown Tree Snakes. To protect other vulnerable Pacific islands, the U.S. In addition, the snake continues to substantially impact domestic poultry, pets, the island's electrical power infrastructure, and human health. Guam's 12 forest birds were especially impacted, with 10 species eliminated and the other two severely reduced. The Brown Tree Snake caused the extirpation of 13 of Guam's 22 native breeding birds and contributed to the extirpation of several species of native bats and lizards. Under the right conditions, it is capable of high rates of reproduction and population growth. This secretive nocturnal arboreal snake occurs in all habitats on Guam, from grasslands to forests. Over the following two decades it spread throughout the island with little public or professional recognition of its extent or impacts. The Brown Tree Snake, Boiga irregularis (Merrem, 1802), was accidentally transported to the island of Guam shortly after World War II.
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