After World War II, a few snakes reached Guam; they now number up to 30,000 per square mile, and scientists found 19,000 hidden genetic changes

Brown tree snakes invaded Guam after World War II, likely hidden in cargo, and now reach densities of up to 30,000 per square mile.

The invasion drove native forest birds to local extinction and causes hundreds of power outages annually.

Researchers at the University at Buffalo used long-read genome sequencing and found 19,000 hidden genetic changes in the snake population.

The hidden DNA changes challenge earlier assumptions that the snakes would suffer severe inbreeding due to a small founding population.

The genetic flexibility helps explain how the brown tree snakes adapted and became a notorious invasive species.