A motion-detection based camera trap for small nocturnal mammals with low latency and high signal-to-noise ratio

1. Camera traps are useful for monitoring wildlife populations, but traps
may not always trigger when targeting small, nocturnal species. Motion
detection techniques have advantages over time-lapse and heat-triggered
traps, but need to be deployed to maximize signal-to-noise ratio. 2. As
part of a study of flying squirrels (Glaucomys) in urban environments we
developed motion detecting camera traps using a raspberry pi microcomputer
and camera and a 940 nm IR illuminator on a tree-mounted wooden platform.
The system was built from commercially available parts and was comparable
in cost to a consumer camera trap, although this cost did not include a
waterproof housing. We compared the performance of our system to
commercial trailcams. 3. Four pi cameras successfully documented visits by
Glaucomys and other animals to bait placed on the platform over three
nights at four wooded sites: suburban and rural backyards, a private
outdoors club, and a small urban nature reserve (16 camera X site
combinations, 48 trap nights). The traps showed low latency, with an
average of < 1 night until detection of Glaucomys at each site.
Data collected had a high signal-to-noise ratio; of 2182 capture events
55% documented Glaucomys, 40% documented non-target mammals, 1% were
caused by large insects, and the remaining 4% were unknown. Commercial
camera traps placed at the sites failed to capture many of these events.
4. The low cost and high signal-to-noise ratio of this system may make it
easy to adapt for other small animal applications. The main modifications
required to deploy this system in new situations will be in locating or
providing a fixed or static background against which animals can be
observed and in using masking techniques within motion detection software.