Auckland Zoo Giant Weta at Auckland Zoo
- Thread starter Chlidonias
- Start date
What are the threats that almost drove this species to extinction? Were they all being eaten by rats that they didn't evolve with? Haven't the rats been around for at least hundreds of years?
the Polynesian rats were introduced to NZ somewhere between 800 and 2000 years ago [there is some dispute about when: Maori settled NZ about 800 years ago but there is published subfossil evidence of rats being here up to 2000 years ago which if so would mean there was an earlier visitation by Polynesians who either didn't stay or didn't survive. See this article which has further links within: http://www.landcareresearch.co.nz/research/research_details.asp?Research_Content_ID=50]
Brown (Norway) rats were the next rats introduced, on the first European ships in the late 1700s. Brown rats don't climb well so while they were a big threat to ground-dwelling animals they didn't really affect arboreal critters like giant weta. However by the mid-1860s the rats found on visiting ships changed to the black (ship) rat, and these are strongly arboreal. It was after the introduction of the black rats that the giant weta suffered catastrophic declines on the mainland (they are too big to hide and too placid to defend themselves), hence they are now found only on offshore islands (specifically Little Barrier Island).
Polynesian rats do climb well and are omnivorous but they weren't apparently as big a threat to the weta as the black rat. Now the Polynesian rat itself is, apart for a few tiny colonies, only found on offshore islands in NZ, out-competed by the more aggressive European rats!
Brown (Norway) rats were the next rats introduced, on the first European ships in the late 1700s. Brown rats don't climb well so while they were a big threat to ground-dwelling animals they didn't really affect arboreal critters like giant weta. However by the mid-1860s the rats found on visiting ships changed to the black (ship) rat, and these are strongly arboreal. It was after the introduction of the black rats that the giant weta suffered catastrophic declines on the mainland (they are too big to hide and too placid to defend themselves), hence they are now found only on offshore islands (specifically Little Barrier Island).
Polynesian rats do climb well and are omnivorous but they weren't apparently as big a threat to the weta as the black rat. Now the Polynesian rat itself is, apart for a few tiny colonies, only found on offshore islands in NZ, out-competed by the more aggressive European rats!