Predator control and the health and abundance of North Island weka—a report on the Motu region project

Download the publication

Predator control and the health and abundance of North Island weka—a report on the Motu region project (PDF, 4,718K)

Abstract

A population of North Island weka (Gallirallus australis greyii), a threatened flightless rail, was monitored in both predator trapped and non- trapped areas of forest and pasture from 1999 to 2012. The aim of the study was to determine if predator control would lead to long-term increases in weka health and abundance, thereby increasing the resilience of the treated population to stochastic events.

800 stoats, 209 feral cats and 40 ferrets were removed from the trapped area. Adult and juvenile weka in both the trapped and nontrapped areas appeared healthy (based on weight and visual checks) and have increased in numbers. Survival of juveniles to 12 months of age was 69% in the trapped area and 64% in the non trapped area, with predation by mustelids (both confirmed and suspected) being the largest cause of death in both areas.

Between 2003 to 2010 adult density in the trapped area increased from 0.14 to 0.36 weka per hectare and in the non- trapped area from 0.24 to 0.30 weka per hectare. Fifty seven weka were inadvertently captured in mustelid and cat traps and trapping tunnels were repeatedly modified to try to exclude weka. These changes have resulted in a decrease in the number of weka being trapped.

The opportunity to monitor the effects of mustelid trapping on a weka population during a major non predator related stochastic event did not arise during the term of the project.

Contents

• Abstract
• Background
• Objectives of the Project
• Methods
  • Study areas
  • Predator control
  • Objectives of Predator Control
  • Stoat control
  • Ferret control
  • Cat control
  • Mustelid monitoring
  • Rodent monitoring
  • Weka monitoring
  • General monitoring
  • Juvenile monitoring
• Results
  • 1. Predator control
  • 2. Weka monitoring
  • 3. Juvenile monitoring
• Discussion
  • Predator control
  • Weka monitoring
• Appendix 1: Stoat Control at Toatoa (1998–1999)
• Appendix 2: Stoat Control at Motu (1999–2012)
• Appendix 3: Ferret Control at Motu (2006–2012)
• Appendix 4: Mustelid Control at Motu (1999–2012)
• Appendix 5: DOC200 trap layout
• Appendix 6: DOC250 trap layout
• Appendix 7: Location of DOC200 and DOC250 traps
• Appendix 8: Density index calculations
• Appendix 9: Cat Control at Motu (2002–2012)
• Appendix 10: Call counts
• Appendix 11: Population and Adult health
• Appendix 12: Nest Monitoring (1997–2002)
• Appendix 13: Chick Monitoring (1997–2002)
• Appendix 14: Juvenile Monitoring (1997–1999)
• Appendix 15: Juvenile Monitoring (1999–2011)
• Appendix 16: Weather and climate
• Acknowledgements
• References