Invasive Snake's Appetite Increases Spider Population in Guam

A new study suggests that spider population has increased in jungles of Guam in the western Pacific Ocean, thanks to the invasive brown tree snakes.

Researcher Haldre Rogers from the Rice University in Houston estimated the population growth of the spiders in Guam near the Pacific islands by counting the number of spider webs in the region. She found that the spider population in Guam jungles has increased 40 times more than the population found in other forests in the nearby regions.

Rogers blamed the increase in invasive brown tree snakes as the main cause behind the spiders' population growth. The brown tree snakes are native to coastal Australia, Papua New Guinea and some other islands. 

Although they are not native to Guam, the brown tree snakes was introduced to the jungles in the 1940s.

According to the U.S. Geological Survey (USGS), the snake species in Guam is said to be the only species that has been documented to be reproductive outside the native range.

The snakes' diet system includes variety of foods including lizards, birds and other mammals. While the young ones consume small birds, the adult males are known to prey on big birds. This has raised a grave concern to the bird species in Guam, where their population has dwindled and is almost depleted.

The invasive species has wiped out about 10 of the 12 native bird species so far, with the last two species surviving in certain regions owing to protection taken to trap snakes. The decrease in bird population has helped the spiders in the areas to thrive, simply because their predators - the birds - have vanished, reported OurAmazingPlanet.

"Anytime you have a reduction in insectivorous birds, the system will probably respond with an increase in spiders," Rogers told OurAmazingPlanet.

"With insectivorous birds in decline in many places in the world, I suspect there has been a concurrent increase in spiders, she said.

Although the government is spending huge amount of money to protect the native bird species by checking for the snakes that secretly snuggle in cargos or aircraft, it has become very difficult to find the snakes as they are hard to see.

The findings of the study are published in the journal PLOS ONE.