Stewart island robin / toutouwai. Photo - DOC

Hedgehog survey yields interesting results

Predator Free Rakiura’s search for hedgehogs has yielded some interesting results - despite few of the spiky mammals being spotted!

With support from landowners, local contractors, SIRCET, and the Rakiura DOC office, 147 cameras were set up in a 13-square-kilometre area surrounding Oban in May 2023. The idea of the camera survey was to see if we could find a boundary for the population of hedgehogs – so that we can start to understand how big the hedgehog problem might be. A further six cameras were used as a ‘control’, within the township,  where hedgehogs have previously been known to be present.

Each camera was baited with wet meat cat food, and the cameras were in place for at least 10 nights. More than 30,000 images were captured by the cameras! No hedgehogs were detected in the survey area, while one was detected in the control area. Lots of other species were detected across the grid, including possums, rats, cats, deer, and many birds. 


The camera deployment team getting ready to roll out. 
From left: Jack Dobbins, Sandi Van Leeuwen (front), James Ware, and Kevin Carter (front).

There was one animal detected which may have been a mouse. Further review of the images by PFR’s research partner Manaaki Whenua was unable to confirm whether this was the case - it’s possible the animal was a small rat - potentially kiore. We know that mice arrive on Rakiura but don't seem to set up an established population. So this possible sighting is helpful information not only for Predator Free Rakiura but others interested in mice sightings. We've passed on the images to Department of Conservation and Environment Southland.

There could be several reasons why hedgehogs weren’t found within the
survey area:

  • Hedgehogs were already hibernating at the time – we know that hedgehogs hibernate in winter, and we were searching for them close to hibernation time. 
  • Baited cameras weren’t an effective method for detecting them. 
  • Hedgehog density (the number of hedgehogs out and about) was too low to detect them.
  • Hedgehogs are absent from the survey area.

‘No detections’ of hedgehogs doesn’t mean that the work hasn’t been valuable, nor that hedgehogs aren’t out there. There hasn’t been any other recent data available on hedgehog distribution, so this work creates a baseline for us to work from. It was also a great opportunity to test baited cameras as a tool for
hedgehog detection, and we’re keen to build from that with other techniques and at a different time of year.

The results could mean that hedgehogs are limited to the township, but we will need to do more research into hedgehogs on Rakiura - including where they are and how many there may be. The results from the survey have also helped us to begin building a data set on other species in the area, which is beneficial to PFR, too! We will keep you posted with what will come next for our hedgehog investigations!

In the meantime, a big thankyou from PFR to landowners and local contractors
for their support in delivering this important research!

Read our previous story about our Hedgehog Survey work here.

 

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