Wildlife Research Wildlife Research Society
Ecology, management and conservation in natural and modified habitats

Can a predator see ‘invisible’ light? Infrared vision in ferrets (Mustela furo)

Haylie G. Newbold A B and Carolyn M. King A B
+ Author Affiliations
- Author Affiliations

A Department of Biological Science, University of Waikato, Private Bag 3105, Hamilton, Waikato 3200, New Zealand.

B Corresponding authors. Email: haylie.stevens@gmail.com, cmking@waikato.ac.nz

Wildlife Research 36(4) 309-318 https://doi.org/10.1071/WR08083
Submitted: 28 May 2008  Accepted: 19 February 2009   Published: 1 June 2009


Infrared (wavelengths >750 nm) light-emitting equipment is commonly used worldwide to monitor nocturnal predator and prey behaviour. However, it is possible that the infrared (IR)-light wavelengths emitted from the equipment are so close to the spectral threshold of some key species that the light may be detected. An operant procedure was used to test whether five male ferrets (Mustela furo) could see an IR light with peak wavelengths of 870 and 920 nm. First, the ferrets were taught to press a lever under a lit white light for food reinforcement (overall mean response accuracy was 89%). Changing the properties (wavelength and intensity) of the light did not disrupt the ferrets’ abilities to perform the learned task. When the light was changed to IR (870 nm), four of five ferrets responded to the light at levels significantly higher than chance (mean = 68%, n = 4188, P < 0.01). When glare from a red trial-starting light was removed, two of the five ferrets (S3 and S4) showed strong evidence (response accuracies of 84% and 78%, respectively, P < 0.01) that they could see IR at 870 nm; however, S3 definitely could not see IR at 920 nm (n = 124, mean = 47%, P = 0.53). We conclude that at least some ferrets can see the light emitted from standard monitoring equipment that uses IR wavelengths of ~870 nm. To ensure nocturnal predator and prey behaviours are not altered by IR surveillance, field programs should use only high-wavelength IR diodes (at least 920 nm).


The authors thank Bill Temple and Jennifer Chandler for their technical help, wealth of knowledge on behavioural studies involving animals and computer programming skills. We also thank Dun-Edin Farm Ltd for their time and commitment, and for entering the very lengthy and complex process of obtaining a ferret exemption permit with us, and Ray Littler for statistical advice. And finally, thanks go to Gavin Ng, Amy Tanahil and Bevan Newbold for their share in caring for the ferrets. This project was the first in New Zealand to involve captive ferrets since they were declared Unwanted Organisms under the Biosecurity Act 1993. It is now unlawful to keep, sell or release ferrets, either live-trapped or captive-bred, without an exemption permit from The Chief Technical Officer of the Department of Conservation, Wellington. We began this process in September 2004, and received our permit on 1st May 2005; the suppliers, Dun-Edin Farm Ltd, Dunedin (one of the last establishments still licensed to breed ferrets for export), also had to apply for permission to sell to us. Ferrets were received from them on 8th August 2005. Ethics permission (Protocol 621) was granted by the University of Waikato Animal Ethics Committee in February 2005 and extended until February 2007.


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Appendix 1.  Spectral properties of each coloured light-emitting diode, including the visible colour of the light, peak and the range of wavelengths as measured with a spectrometer, and intensity as measured with an OPhir PD-300 lazer power meter
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