and the only people who are allowed on the island are research teams who receive waivers to collect data. It is blocked off to the public to protect human and snake life. Endangered species Because there are so many snakes on one island — by some estimates one snake to every square meter (10.8 square feet) — there is competition for resources. Despite a population of 41 recorded bird species on Queimada Grande, the golden lancehead (Bothrops insularis) relies on only two: the Troglodytes musculus (southern house wren), which is usually able to avoid the golden lancehead as a predator; and the Chilean elaenia (a species of flycatcher), which feeds on vegetation in the same area as the snake. The island was previously thought to have a population of about 430,000 snakes, but recent estimates are much lower. The first systematic study of the population of the golden lancehead found the number to be 2,000 to 4,000, concentrated almost entirely in the rainforest area of the island. This might have happened because there was a limited amount of resources and the population became level, but in 2015 an estimate by a herpetologist on a Discovery Channel documentary stated that the population remains at 2,000 to 4,000 golden lanceheads. The golden lancehead also may be at risk from inbreeding, effects of which are evident in the population. Because of the overall low population of the golden lancehead, the snake was labelled critically endangered on the IUCN Red List of Threatened Species. It also was placed on the list of Brazil's endangered animals. The island is also home to a smaller population of Dipsas albifrons, a non-venomous snake species. See also Ilhas Queimada Pequena e Queimada Grande Area of Relevant Ecological Interest References External links Atlas Obscura: Snake Island: Ilha da Queimada Grande National Geographic Field Tale: Snake Island Mark O'Shea's Lost Worlds Vice News: Snake Island Full Length Snake Island Brazil: Taste Of Poison Paradise Queimada Grande Areas of relevant ecological interest of Brazil Geography of São Paulo (state)