Brown Tree Snake Thrives on Guam Despite Genetic Bottleneck

The brown tree snake (Boiga irregularis), native to northern Australia, eastern Indonesia, Papua New Guinea and nearby islands, arrived in Guam after World War II, likely as a stowaway on cargo aircraft. Since the 1940s the species has devastated native bird and reptile populations and causes hundreds of power outages each year by climbing utility poles.

A July 2026 study published in Science Advances used long‑read sequencing to examine the snake’s genome. Researchers identified nearly 19,000 structural variants—duplications, deletions and rearrangements—especially in genes linked to immunity and smell. The study’s corresponding author Trevor Krabbenhoft said, “The brown tree snake is maybe not wildly diverse, but it has important sources of genetic diversity that have been underappreciated.” First author Christopher Osborne added, “It’s possible that endangered species may have more flexibility in their genes than we realize.” These hidden variations help explain how a population founded by only a few individuals survived a severe bottleneck and expanded to densities of up to 30,000 snakes per square mile.

The findings suggest that other inbred or endangered populations might retain more adaptive capacity than previously thought, offering new perspectives for conservation biology and invasive‑species management on Guam and elsewhere.