New Zealand Journal of Ecology (2023) 47(2): 3530

Predator control to protect a native bird (North Island kōkako) also benefits Hochstetter’s frog

Research Article
Michael R. Crossland 1,2*
Hollie Kelly 3,4
Hazel J. Speed 5
Sebastian Holzapfel 1,6
Darryl I. MacKenzie 7
  1. Department of Conservation, Private Bag 3072, Hamilton 3240, New Zealand
  2. School of Life and Environmental Sciences, The University of Sydney 2006, NSW, Australia
  3. Department of Zoology, Zoology Building, King’s College, University of Aberdeen, Aberdeen AB24 2TZ, United Kingdom
  4. Shape Shifters Ltd, 2 Durward Gardens, Kincardine O’Neil, Aboyne AB34 5BZ, United Kingdom
  5. Department of Conservation, PO Box 32-026, Devonport 0624, New Zealand
  6. Department of Conservation, PO Box 343, Thames 3540, New Zealand
  7. Proteus Research and Consulting Ltd, PO Box 7, Outram 9062, New Zealand
*  Corresponding author

Control of introduced predators is part of the management strategy for many conservation programs. However, when such programs are designed to protect a single species, the benefits to sympatric native species are usually not assessed. We used site occupancy modelling to investigate whether predator control implemented to protect a native bird species (North Island kōkako) in the Hūnua Ranges, New Zealand also benefits the sympatric native Hochstetter’s frog population. We hypothesised this benefit is possible because both native species are vulnerable to introduced mammalian predators that are targeted by control measures. Model results indicate that the predator control history of sites was the only factor to exhibit a strong and consistent relationship with occupancy by frogs. Under a range of realistic model scenarios, the probability of occupancy by juvenile, sub-adult, and adult frogs was consistently higher at sites that receive intensive predator management. Relationships between occupancy probability and other site factors (number of refugia, air temperature) existed but were inconsistent among frog age classes and either occurred independent of predator control history or appear less biologically relevant than predator control. The results support the notion that predator control designed to protect North Island kōkako in the Hūnua Ranges also benefits the Hochstetter’s frog population.