Relative efficacy of chew card and camera trap indices for use in hedgehog and rat monitoring

ABSTRACT

Monitoring is an important component of pest species management in New Zealand. Chew cards are increasingly used for mammalian pest monitoring. They are effective for measuring the relative abundance of rats (Rattus spp.), but their effectiveness for measuring hedgehog (Erinaceus europaeus) relative abundance has not been tested. Camera traps are also increasingly used as a monitoring tool, but there has been little calibration with other methods. We investigated whether chew card indices and camera indices for hedgehogs and rats gave consistent monitoring results. We also explored the relationship between the relative abundance of rats and hedgehogs using these indices. Hedgehog and rat chew card indices both showed a positive relationship with the respective camera indices for each taxon. However, cameras had fewer detections than chew cards when relative abundance was low (particularly for rats). Interference by rats did not appear to affect detection of hedgehogs with chew cards. Although not a strongly supported result in our study, the relationship between rat and hedgehog relative abundances requires further study and is a reminder that single-species pest control may not produce desired biodiversity outcomes.

KEYWORDS:

• Conservation
• competitor release
• pest mammals
• pest management
• relative abundance

Acknowledgements

Our thanks to Alice Baranyovits, Ohara McLennan, Isobel King and Melissa Kirk who helped with field work. We also thank Jo Peace for technical support. This research was conducted under University of Auckland Animal Ethics Committee Approval No. 001896. Permission to undertake research at the sites was given by the Hibiscus and Bays, Kaipātiki, Albert-Eden, Henderson-Massey, Puketapapa, Upper Harbour and Whau Local Boards. The Centre for Biodiversity & Biosecurity and The University of Auckland contributed funding towards this project. We also thank Dave Kelly, Stephen Hartley for their comments on this manuscript and Deb Wilson and anonymous reviewers for comments on previous versions of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by The University of Auckland; The Centre for Biodiversity & Biosecurity.