Dear friends:
I am using camera traps to investigate wild boar population density and I am analysing data collected over 7 weeks. I broke them into four 12 or 13-day sections (pseudo-replicates) and realised the number of detections in the first section is much higher than the other 3 sections (216, 147, 145,124 respectively). May I ask has anyone come across similar situations (i.e. the number of detections being high immediately after set-up, and decreases after the 7-10 days or so)? What could be the possible reason for this pattern?
Thanks in advance
Eagle
28 June 2019 2:46pm
Hello Blue Eagle,
You don't mention what type of camera trap you are using, so it's hard to speak to specifics, but I can tell you that I've seen the same pattern on real-time transmission cameras and we eventually traced it back to the camera being less reliable as the battery drains. What are the battery levels reporting at in the later images?
Eric
1 July 2019 2:57pm
Given that the rechargable batteries are starting out with lower voltage, I would suggest trying to run a test wherein you use standard alkaline or high powered Lithium as a test to see if that resolves your issue. If it does, and you want to make sure you can still use rechargeable batteries, maybe consider something like:
https://www.amazon.com/AA-Batteries-Rechargeable-ECO-Friendly-Recyclable/dp/B079JFK22D/ref=sr_1_3?crid=3UY7WGNZXC31Q&keywords=lithium+rechargeable+aa+batteries&qid=1561989505&s=gateway&sprefix=lithium+rec%2Caps%2C173&sr=8-3
as those will maintain a full 1.5 v level until they totally run out of power. Both NiCD and NiMH batteries exhibit a voltage drop as power depletes, which could be what is causing decreased detections.
2 July 2019 9:25am
There was a talk recently at ZSL where a similar thing was found using camera traps studying wild pigs in the Osa Penisula. Tracking and other audio evidence showed that the pigs populations were circumnavigating camera traps which appeared to be giving a reduced level of detection.
@ollie.wearn made an interesting point as he has found in his research that wild pigs are extremely sensitive to human or unfamiliar smells and will avoid anthing that holds the scent. Once the pigs know the cameras are there they are likely to avoid them.
Something to think about as I would doubt it would be anything to do with those cameras.
Eric Schmidt
Wildlife Protection Solutions (WPS)