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PostPosted: Sun Feb 16, 2020 2:13 pm 
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We all wonder how long we have to wait before species X shows up, where species X is usually bobcat or puma. "Be patient" is the common answer. Another answer that holds water? "You'll get a lot of squirrels and deer before you get any cats." If you're a glutton for punishment and have saved your camera trapping results you can calculate the probability in days of waiting at a 95% confidence level. Field biologists use this method to analyze camera trapping results. (I am trying to understand it.)

The graph shows the differences between species at a pool in a seasonal creek. It's based on 1158 camera days over several years. You don't count all photos or clips in this analysis. Ten photos within 1 hour of each other are counted as a single detection event. This convention reduces inflated values due to animals that are "frequent repeaters". My calculations are based on data pooled across seasons. If I sorted the data into winter versus summer the probabilities would at least be different for bears, and maybe other species too.

Attachment:
CEDAR STUMP POOL SPP PROBS.png


The values at the end of the green bars are number of weeks. I can usually get black bear, gray fox and striped skunk in a week. The calculation tells me I have to wait 10 weeks for a bobcat and 5 months for a puma. The missing species are long-tailed weasel and coyote. I've gotten both species nearby: the weasel once, and coyotes 3 times.

I have camera trapped this ravine since 2008. It is the best location that I know of for bears, but it is NOT the best one for puma. I may have more to say about better locations after I analyze data from other sets. Though our impressions don't always agree with the data, this exercise didn't give me any surprises.


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PostPosted: Sun Feb 16, 2020 6:56 pm 
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You've put a lot of effort into this endeavor of yours, it's a good idea too. Most folks can understand graphs as it's a clearly visible way of conveying data for presentations. Where would the human species fit into this graph?

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PostPosted: Sun Feb 16, 2020 10:46 pm 
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Hahah! Well, the only human who goes there is me. The only other person who showed up was a kid in shorts with a rock hammer -- an aspiring miner, I guess. He was careful to keep his face out of view but peered closely at the camera and said, "Hmmm, Cal Fish and Game . . . " The family moved to Nevada. Yours truly makes an appearance every month or two, at least nowadays, and is often caught in video talking to the dog, or cursing at bear mischief.


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PostPosted: Mon Feb 17, 2020 10:07 am 
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cameratrapcodger wrote:
Hahah! Well, the only human who goes there is me. The only other person who showed up was a kid in shorts with a rock hammer -- an aspiring miner, I guess. He was careful to keep his face out of view but peered closely at the camera and said, "Hmmm, Cal Fish and Game . . . " The family moved to Nevada. Yours truly makes an appearance every month or two, at least nowadays, and is often caught in video talking to the dog, or cursing at bear mischief.

Well at least you're not talking to your video cams like I do :)

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PostPosted: Mon Feb 17, 2020 7:21 pm 
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Interesting. I'm no statistician (my several courses in statistics were far longer ago than I care to think about), but that's an interesting analysis. It's very different than what I'd get here where gray squirrels would be the most common capture followed by white-tailed deer. Of course there's a lot of seasonal variation -- last summer and fall one of my camera traps caught a long-tailed weasel several times a week, but it hasn't shown up since late November. I'm also finding that one location that had been very good for many species ever since I began camera trapping has, in the last few years, almost dried up since a nearby trail now gets a lot of use from runners where three years ago it hardly ever got any use. So much information to be gathered, so little time.

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PostPosted: Mon Feb 17, 2020 9:32 pm 
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Woody, I left out the gray squirrels, deer mice, wood rats, and deer. The squirrels in particular are overwhelming esp during hot weather when they are drinking all day long. I also get many perching birds in late summer, with Hermit thrushes taking the prize for most photos. I am now tabulating some other sets and am including the deer.


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PostPosted: Wed Mar 25, 2020 3:20 pm 
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I go by a different method...humans stink, therefore a bear will follow the scent to see what you are doing in the area...so let the animal come to the camera. Then set out 10 or 15 cameras in a location where you have the background you want, hide the cameras well and check once a week.

The more cameras the better chance for your photo. That's raising the odds and works for any animal. It helps if you know the habits of all the animals before setting cameras. As we get older it helps to use a GPS so you can locate the cameras. I always set my cameras in a large circle like a trap line, makes checking and finding the cameras easier. A 5 to 10 mile hike is a good start and can be adjusted on the first checking.

The more cameras the better...


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PostPosted: Sat Mar 28, 2020 10:00 am 
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Cliff, couldn't agree more about the number of cameras and knowing your critters' habits.


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PostPosted: Sat Mar 28, 2020 12:12 pm 
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"couldn't agree more about the number of cameras"
Yes indeed. The other issue is how many animals pass behind the camera or off to the side just far enough for the camera to miss them. Except for snow or soil that would hold tracks, we never know how many time the camera miss.

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PostPosted: Tue Mar 31, 2020 4:18 pm 
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Very interesting study.
I'd like to know more about the methods. If you'd care to share a link that would be great.
Seems like there are many variables one could plug into the formula? I'm curious how one might factor for camera stations that are intentionally set for specific species, if that would make any difference in the stats? For example, I set cameras for wolverine/lynx and during winter it works out quite well, but spring, summer and fall I get a variety of non-snow obligate critters at the same stations.


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