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From basic thermodynamic principles, I would normally expect prey species to be much more abundant than predators. Applying that to North American species like deer, wolves and bears, I would expect deer to be much more abundant, and when I run some Google searches, though the estimates for actual numbers per square kilometer span wide ranges, they all qualitatively agree with this expectation.

But looking at e.g. this trail camera footage from Algonquin Park

https://www.youtube.com/watch?v=a8cbqLQs1xs&ab_channel=KevinJeffery

Wolves and bears seem to show up about as often as the various deer species (white-tailed deer, moose, and something else, elk?) to within, say, a factor of two.

Why the apparent discrepancy between theoretical expectation and observed data? It's not a peculiarity of that location; I've seen a similar pattern in trail camera footage from several states.

Which ratio corresponds to experience of going for a walk in Algonquin Park? Are you about equally likely to encounter any of the large animal species, as the trail camera footage would suggest?

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    Is this 24/7 foottage or 'selected bits' foottage?
    – Willeke
    Jun 22 at 10:07
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    @Willeke I had been assuming the trail camera footage on YouTube was 24x7 in the sense that the only filtering was that done automatically to only show scenes with movement. Is that not the case? If it's been manually filtered, that makes it worse than useless for my purposes (of getting an intuitive feel for the distribution of different animals).
    – rwallace
    Jun 22 at 12:07
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    This is based on what people chose to post on Youtube? By this same logic, I'd also need an explanation of why it appears from looking on social media sites as if there are far more cats than any other non-human animal on earth.
    – T.E.D.
    Jun 22 at 17:53
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    I have a trail camera in my backyard in an exurban area of Connecticut (not as wild as Algonquin, of course, so take this with a grain of salt.) The two most common animals I get pictures of are deer and coyotes, and I probably get 5–10 times more deer pictures than coyote pictures. But I only post a small fraction of my deer pictures to Facebook, because once you've seen a few deer pictures you've seen them all. Jun 22 at 17:58
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    I had some trail cameras set up in a forested area, and the footage showed we had a serious problem with wild hogs. We saw 4-5 times more hogs than any other non-flying species. An in-person examination showed that the property was home to exactly three hogs, who wandered past the camera dozens of times per night. Moral of the story: when doing a population study, take trail camera footage with a grain of salt.
    – bta
    Jun 22 at 21:30

2 Answers 2

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If the footage has been put on YouTube, it's probably been edited. Reasonable editing would be to show the range of species and/or behaviour in the area - after all, it's entertainment or at most education, not data.

By looking closely at the video, it's possible to back this up: there's a jump at about 29s after 2 wolves exit to the right, when one pops into view in the middle, heading left. That suggests its entrance was trimmed out, which is unlikely to be automatic due to lack of detection, thus it was edited manually. There's actually a less obvious jump a few seconds earlier, where one wolf is heading right, gets about 2/3 of the way across, then 2 are. The timestamp at the bottom of the image shows a minute has passed, so it's probably another member of the same pack.

But I speculated earlier about the siting of the cameras. The camera owner is likely to have placed them where they're likely to see a lot of interest, such as areas known to be frequented by predators, while herbivores, being more plentiful, will be picked up anyway. In that sort of terrain, the larger herbivores will be slightly dispersed, while wolves at least move in packs. This will account for many repeats in the same place.

It's decades since I went to the Algonquin, but in broadly comparable habitat, your intuition is correct. Prey species are fairly commonly seen; predators far less so, even if you're looking for them. For example in Yellowstone we went to where we knew there was a good chance of seeing a wolf pack early in the morning. We saw them well (through telescopes) but we saw more deer and bison. We got one good view of a coyote that trip. In the Gaspesie (Québec) we saw a wide range of herbivores, often pretty close but the only carnivores we saw well were birds. Predators that are actively hunting will try not to be seen. Much of the rest of the time they're resting, and of course they're few and far between to start with. Many herbivores are almost constantly grazing and visible.

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    Also - and I don't say this lightly - read the comments on YouTube (especially the Geoff Pimlott's comment and its replies link - I think)
    – Chris H
    Jun 22 at 13:11
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I think there might be another reason beyond the accepted answer.

Predators have to roam a lot more throughout their territory in order to find food and if they fail an attack on a prey they have to go somewhere else because in that area all the animals will be alarmed and ready to run. Therefore the number of passages in front of the camera trap might not be proportional to the number of animals in the area.

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