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

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. [ABSTRACT FROM AUTHOR]