Invasive species

The biggest ecological issue on the SAFER Islands is the presence of introduced mammals: rats, mice, and rabbits. Rats have 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.

P1220296Pest Eradication Bense Islandmousecropped

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.

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. Only 3 rats were found in the interior heath (from 1077 trap-nights), whereas 82 rats were caught in coastal tussock areas (from 1612 trap-nights).

Index trapping on Bense Island
Rodent Research | View Gallery

Since these pest species are the biggest hindrance to healthy ecosystems on the island, it stands to reason that eradicating them is the single most important thing we can do to restore the islands to prime wildlife habitat.