What controls the snakes population in its native range?
To many people’s surprise, the answer to this question lies not in what could possibly eat the brown Treesnake but instead what primarily immature snakes themselves eat. This food source, mainly small lizards, is far more limited in its native range (coastal Australia, Papua New Guinea, and a large number of islands in northwestern Melanesia) than the bountiful feast that awaited it on Guam and may be available for the snake on other oceanic islands. The combination of extraordinarily high lizard densities, the main food source for young snakes, and birds that did not evolve in the presence of snakes with no natural defenses against them allowed the snakes to successfully colonize Guam. The continued high lizard densities, mostly credited to introduced species that mature rapidly and reproduce frequently, has allowed the brown Treesnake to maintain densities of nearly 13,000 per square mile in some areas, even in the absence of native birds.
