The obvious question not asked on Campbell Live tonight (21 September) about the Little Blue Penguins on Rangitoto was "Now that the rats have been eliminated from these islands by the Pest Off rat control programme, what will be the results for penguins and native forest birds?"
The answer is that there will be a dramatic difference. Some of you may know that as well as being Chair of the Auckland Regional Council, Mike Lee has had a passion for the Hauraki Gulf Islands and for his efforts to reduce the impact of rats on birdlife on these islands. Most other people pointed the finger at stoatsas the key predator of native birds. Mike, correctly, showed great foresight and pointed out that rats have had an even greater devastating impact on all native forest birds on both the mainland and on islands. He has spearheaded efforts to clear the islands of rats starting with Tiri Tiri Matangi . It was great that the August 2009 issue of Forest and Bird acknowledged Mike's efforts starting the campaign to get pests off what is now literally the "Treasure Island" of TiriTiri Matangi.
I first met Mike 25 years ago and he was then determined to re-establish bellbirds on Waiheke. It was unsuccessful because everyone underestimated the impact of rat predation. But Mike learned from this failure and has gone on with the ARC to create some of New Zealand's great nature sanctuaries.
I understand that with the removal of rats from islands in the Gulf there has been an explosion in the number of Little Blue Penguins and of all the other native birds. This is exactly what will happen on Rangitoto
In summary then:
The "one off" rat elimation operation on Rangitoto resulted in removal of these dreadful predators.
It also resulted in tested shellfish showing no sign of the anticoagulant rat bait residue.
2 of 5 penguins autopsied showed minute traces of rat poison but this was in concentrations so low that it was improbable that it had any causative effect on the penguin deaths.
"Pest Off" is used all through the warehouses on the Auckland waterfront to control rats in these storehouses of foods and shipping goods. There is a legal requirement on all warehouse owners to do this. Pest Off, sometimes called Talon is the control method of choice.
It is far more likely that the source of the minor traces of Pest Off (brodifacoum) in the 2 penguins rather than from the DOC operation on distant Rangitoto was instead was much more local to the North Shore. The residual rat bait identified in dead penguins on the North Shore is much more likely to came from dead or dying rats and mice falling down under gravity into the Waitemata Harbour waters beneath these warehouses and then being eaten by fish or penguins.
Good science always requires you to have an untreated "control".
When the 5 penguins found dead on the North Shore beach were tested in Australia for a range of chemicals, it was acknowledged to be a "first". This testing had not been done before. If this is the case, there is a high probability that if my "wharf warehose poisoned mice and rat theory" is valid, tests even before the Rangitoto pest control operations went ahead should have been done. These may well have revealed minute quantities of rat poison in some of the penguins that had been swimming around the wharfs eating anything that took their fancy.
The test of this theory would have been to have had a control penguin population that you had done chemical tests on even before the Rangitoto operation went ahead....but that would have required extraordinary foresight and we all know how little of that there is around.
It might be worth from now on testing any dead penguins found on the North Shore over the coming years.
If fish or penguins catching mice seems all too farfetched to some of you, remember that here in the South Island beech forests a celebrated "fly" used for trout fishing is a mouse. These are widely sold in the fishing gear shops. The trout love eating mice and trout grow fat on mice in the beech mast years caught as they swim across the beech forest rivers and streams.
I think it is marvellous that as a result of the Rangitoto Island pest control operation by DOC this winter, Auckland City now has an pest free 2,000+hectare island on its doorstep. This will become one of the world's great nature reserves.