Males displayed a trailing response to both female and male pheromone trails over blank controls. In this study, the ability of male brown tree snakes (Boiga irregularis), a tropical, rear-fanged colubrid, to follow pheromone trails produced by reproductively active conspecifics was tested in the laboratory by using a Y maze. Of particular importance is the ability of snakes to locate conspecifics during the breeding season via the detection of pheromone trails. The ability of snakes to follow pheromone trails has significant consequences for survival and reproduction. Pheromone trailing behavior of the brown tree snake, Boiga irregularis. The source of the fungus in this outbreak was not determined however, the warm, moist conditions under which the snakes were housed likely predisposed them to opportunistic cutaneous fungal infections. The fungus has been identified as the Chrysosporium anamorph of Nannizziopsis vriesii based on its formation of solitary dermatophytelike aleurioconidia and alternate and fission arthroconidia. The same species of fungus was isolated in pure culture from the skin of three snakes, but fungal cultures were not performed on samples from the fourth snake. Hyphae that penetrated through the superficial surface of the epidermis often formed terminal arthroconidia. These lesions were associated with bacteria and numerous septate, branched fungal hyphae within the epidermis and overlying serocelluar crusts. Histologically, lesions consisted of epidermal hyperplasia and hyperkeratosis, with foci of epidermal necrosis, intraepidermal vesicle formation, and subacute inflammation of the underlying dermis. The deaths of three of the snakes were directly attributable to the cutaneous disease the other snake died from renal failure and visceral gout, most likely induced by gentamicin therapy. All snakes died within 14 days after clinical signs were first noted. Lesions usually started where ventral scales overlapped and spread rapidly. The ventral scales were most commonly affected, and lesions began as areas of erythema and edema with vesicle formation, followed by development of caseous brown plaques. Nichols, D K Weyant, R S Lamirande, E W Sigler, L Mason, R TĬutaneous fungal infections occurred in four captive brown tree snakes (Boiga irregularis). Increased containment efforts on Guam are needed to prevent further colonizations, but a variety of additional management efforts would also benefit the island's remaining bird populations.įatal mycotic dermatitis in captive brown tree snakes (Boiga irregularis). Our results draw attention to the enormous detrimental impact that brown tree snakes are likely to have upon invading new areas. Large clutch size and large body size were also related to longer persistence times, although large body size appeared to delay, but not prevent, extirpation. The most important factor predisposing a species to coexistence with brown tree snakes was its ability to nest and roost at locations where snakes were uncommon. Declines in northern Guam were also relatively synchronous and occurred from about 1976 to 1986 for most species. Declines of ≥90% occurred rapidly, averaging just 8.9 years along three roadside survey routes combined and 1.6 years at a 100-ha forested study site. Twelve species were likely extirpated as breeding residents on the main island, 8 others experienced declines of ≥90% throughout the island or at least in the north, and 2 were kept at reduced population levels during all or much of the study. Our results indicate that 22 species, including 17 of 18 native species, were severely affected by snakes. We analyzed two sets of survey data gathered in northern Guam between 19 and reviewed unpublished sources to provide a comprehensive account of the impact of brown tree snakes on the island's birds. Past studies have provided qualitative descriptions of the decline of native forest birds but have not considered all species or presented quantitative analyses. Predation by brown tree snakes (Boiga irregularis ) devastated the avifauna of Guam in the Mariana Islands during the last half of the twentieth century, causing the extirpation or serious reduction of most of the island's 25 resident bird species. Impacts of the Brown Tree Snake: Patterns of Decline and Species Persistence in Guam's Avifauna
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