Rat Chat by Jude Gilbert
Environmental News Issue 27

We’ve had a fantastic year for birds at Windy Hill. After 13 long hard years of managing to keep pests down to low levels the birds have really bounced back – up to 20 kereru have been counted a number of times and 50 kaka in one count in the Medlands valley alone. Birds are benefitting from the food abundance created by reduced rats and the wetter summer early this year.

The 620 HA sanctuary managed by the Windy Hill Rosalie Bay Catchment Trust now employs seven people – five of these people make up the field team who carry out the integrated pest management, one administers the Trusts finances, and a contractor carries out specialist monitoring as well as the Biosecurity Programme operating at the island’s main wharves and the airport. Conservation and biosecurity is a growing ‘business’ on island.

Rats have continued to be a worthy adversary – immensely responsive to good conditions a female rat can up the number of litters, and the number of babies per litter, she has per year. It is estimated that one pair of rats and their surviving progeny can produce 15,000 rats a year! This fecundity and their capacity to access the highest tree tops and every nook and cranny in any habitat is the reason for the slow but unstoppable decline of Great Barrier’s biodiversity. Even with 4800 stations for bait and traps checked on a regular basis we still trapped 2050 rats and a small number of mice between January and the end of October this year.

What is interesting is that most of the rats trapped are kiore – they bounce back after ship rat numbers are reduced, for some reason taking longer to respond to traps or bait. This has also been the situation at Glenfern Sanctuary. We are the only large island with both these species of rats which makes our pest dynamics incomparable to mainland sanctuaries – some research into the behaviour of, and between, the two species could reveal better ways of targeting them.

Next year we are planning a booster robin translocation from Pureora Forest to Glenfern and Windy Hill – this will increase the number of breeding pairs in the sanctuaries and bring in a new line of DNA. At Windy Hill there are currently five breeding females and 3 males who are very busy servicing all the females and feeding chicks in five nests. Their energy to keep their lineage going is impressive.

We look forward to continuing to increase the volume and diversity of our dawn chorus.