Posted by Sam Lincoln

Biological systems are incredibly complex (see ecological networks blog). Introducing a spider to eat a fly may not help; New Zealand found that out the hard way with rabbits and ferrets. When one food source is running low, most predators prey-switch, and in New Zealand that often means moving onto our native birds. We regularly control rats both in our homes and local parks with little knowledge of the indirect impacts wrought upon biological systems. My Masters project aims to take a first look at how domestic cats respond to the removal of rats in local parks – are they eating more of our birds?

In Auckland Council’s local parks, a mix of native and introduced birds share their space with predators such as rats and domestic cats. There has been much recent debate about the impact of cats in New Zealand; while scientists agree that cats have negative impacts on our native species, the SPCA often has a far more cat-friendly view citing rodent control by domestic cats as potentially helping birds. Even politicians are involved in the cat debate, with Conservation Minister Maggie Barry in one corner fighting for kiwi versus Prime Minister John Key representing Moonbeam. My pilot study of 11 cameras set for two nights captured 14 individual cats in two local parks (as well as a few possums and an MSc student).

By assessing the changes to cat behaviour after removing rats from half of the sites, I will get a first look into what really goes on between cats, rats and birds – is rat control bad for birds due to increased predation by cats, or are rats the main culprits in an urban environment? What would happen if cats were to go? Should we instead be moving toward a predator free New Zealand where our birds can exist without either of these mammalian invaders?

Sam Lincoln is an MSc student in the Centre for Biodiversity & Biosecurity, School of Biological Sciences, University of Auckland. She is trying to disentangle interactions between domestic cats and rats in urban environments. She is supervised by Margaret Stanley, John Innes and Al Glen.