Responses of house mice to the removal of mammalian predators and competitors
Version of Record online: 17 FEB 2012
© 2012 The Authors. Austral Ecology © 2012 Ecological Society of Australia
Volume 37, Issue 8, pages 971–979, December 2012
How to Cite
GOLDWATER, N., PERRY, G. L. W. and CLOUT, M. N. (2012), Responses of house mice to the removal of mammalian predators and competitors. Austral Ecology, 37: 971–979. doi: 10.1111/j.1442-9993.2011.02356.x
- Issue online: 21 NOV 2012
- Version of Record online: 17 FEB 2012
- Accepted for publication December 2011.
- body weight;
- house mouse;
- mainland island;
- predator and competitor release
Efforts to eradicate multiple mammal pests from offshore islands and fenced mainland ‘habitat islands’ often fail to remove mice, and such failures can result in a dramatic change in the food-web whereby the removal of larger mammal pests facilitates a population explosion of mice through predator and competitor release. We investigated the ecological responses of house mice to the removal of mammalian predators from a 500-ha fenced sanctuary at Tawharanui, northern New Zealand. Data on population structure and body condition of mice trapped in 2007, in four habitat types within the sanctuary, were compared with baseline data collected in 2001, before mammal control operations commenced. We hypothesized that: (i) in the absence of mammalian predators mouse densities would increase in all habitat types that provide vegetation cover, and (ii) in the absence of mammalian competitors mice would become heavier due to greater access to food resources. Mouse densities were significantly higher in 2007 than in 2001 in three habitat types. The high density of mice in forest – where none were trapped prior to control – suggests a competitive release, in which mice profited from the removal of ship rats. No mice were caught in the presence of ship rats on a forest trap-line at a control site outside the sanctuary. Mice trapped in 2007 were significantly heavier than those trapped in 2001, and significantly heavier than mice trapped at the control site. Greater access to food in the absence of competing and predatory mammals probably explains the heavier body weight of Tawharanui mice. There has been a significant change in the mammalian food-web at Tawharanui, such that the house mouse is now the primary pest. A rapid and dramatic increase in mouse numbers is likely to adversely impact invertebrates and seedling recruitment, which in turn could affect ecosystem functions.