Sunday, December 31, 2006
A year of camera trappin'
Luck--or being at the right place at the right time accounts for some success, but not all success. I wanted to measure my camera trapping success under different conditions. After all, who wants to trudge through cold rain and mud only to find 20 exposures without critters. It’s like the Earth Goddess forgot to put your packages under Nature’s Christmas tree. So it's time to summarize the many days I squandered in the woods (when I could have been doing something useful, like raking leaves or cleaning gutters).
On a spreadsheet I recorded:
a) the amount of time the cam was available to photograph wildlife,
b) the location (a trail in the woods, a clearing, a water hole), and
c) the attractants used (bait, scent, scat, etc.), if any.
The cameras captured images of 14 species of mammals and one mammal I couldn't identify. This is a highly biased selection, because once an animal gave me a lead, I usually targeted the critter for pictures. Some species were easy to photograph. Foxes, skunks and rodents were attracted to baits, while ringtails and bobcats were not as vulnerable. Deer commonly use trails through the woods, but I wasn't after deer. I find it a little odd that there weren't more pictures of raccoons. And how come I'm not getting coyotes? The neighbors say 10 years ago they howled all night. Have they all been trapped out? The most unexpected picture was the shrew. Pure chance! The biggest thrill was the ringtail and puma, and the bear was gratifying after the ordeal it put me through.
Apologies to my ornithological friends. I never tried to photograph birds, but I got their pictures anyway. Jays, ravens and titmice were all attracted to sunflower seeds, but the hermit thrushes were a surprise. They were the most common visitor to one small waterhole deep in a ravine, where they seemed to be feeding on aquatic insects. (If there was a way to get closeups with these cameras I could get interested in taking pics of dicky birds).
I defined success rate as # of photos with animals divided by the total # of photos.
Total # of camera-trap-days: 755
Total # pictures: 2085
Total # animal pictures: 1060
Overall success rate: 50%
Range of success rate:
by camera: 20% to 90%
24 hr vs night: 33% vs 74%
unbaited sets: 22% (24 hr), 73% (night)
meat sets: 44% (24 hr), 79% (night)
waterhole sets: 72% (24 hr)
seed bait sets: 38% (24 hr), 74% (night)
WHAT DOES IT MEAN?
NUMBER OF CAMERA TRAP DAYS: From Nov 13, 2005 to year's end 2006 I had anywhere from 1 to 5 camera traps in operation. I used 5 cameras: a Cuddaback, an Olympus 390, two Olympus 360Ls, one Sony P32, and 5 Sony s600s. (The Cuddaback is commercial, the others are "homebrews", hacked by the codger himself). I didn't run traps all year long. So the sample size could have been larger.
CAMERA DIFFERENCES: There were differences between cameras in the time required to fire up when the PIR first detects "moving heat. I didn’t compare cams because the sample size was small in some cameras, and there were too many uncontrolled variables. When I adopted the Sony s600, I stopped using the others. The s600 doesn’t fire up as fast as the p32 and P41, but the 6 MP pictures are a compensation. The biggest improvement for me was the production of the new Trail Mode chip for the Pixcontroller board. It allows rapid succession of exposures. Once activated the camera remains on for another 30 seconds after each PIR event. This allows the camera to rapidly fire like a paparrazo. That’s exactly what I want—a camera that takes as many pictures possible as long as the animal is present. "I don't want no schtinkin' minimal interval of 1 minute between pictures."
24 HR VERSUS NIGHT MODE: At many camera sets where the sun reached the ground the sensor detected warm moving air and triggered the camera. False triggering explains the different success rates of the 24 hr and night modes. I got fewer false triggers in night mode.
BAITED VERSUS UNBAITED CAMERAS: Bait almost always increased the number of animal pictures (success rate). Presence or absence of bait seems to have made little or no difference at night. This seems odd, and may be an artifact. I need to look into this next year.
CONCLUSION: My highest success rates came when I used bait, and set the mode for nocturnal shots only. Isolated waterholes attracted birds and mammals just as well as bait does, and 24 hours a day at that, though bears never bathed or drank at night. But I failed to photograph a number of mammals that I know are here. I'll sample more habitats this coming year, and experiment with different kinds of lures. My colleagues and I are also talking about teaming up to do an experiment on the effectiveness of different attractants.