Invasive species

The biggest ecological issue on the SAFER Islands was the presence of introduced mammals: rats, mice, and rabbits. Prior to their eradication in 2016, rats had been present on Bense and Little Bense islands since the 1800’s when whaling ships frequented the neighbouring harbour. European rabbits were also introduced at this time and later farming practices have seen sheep, cattle, and horses in residence. The last of the ungulates were removed in 1985, and South American sea lions are the only native mammals present.

Rats are excellent generalist predators and their presence on an island precludes the survival of bird species like tussac birds and Cobb’s wrens. Mice are thought to compete with native birds for food, as both eat insects and other invertebrates. Rabbits graze native vegetation, causing erosion and hindering natural regrowth.

Before attempting to eradicate these pests, Index Trapping was conducted on Bense Island to better understand the basic ecology of the rodents there. We sampled in the two main vegetation types: coastal tussock grass and interior heath. Mice were regularly found in both habitats but rats were overwhelmingly restricted to the coastal tussock areas.

Rodent Research | View Gallery