Sunday, September 28, 2008

Track of the Week 1: Analysis

Thanks to everyone who participated this week. It was fun for me to read and join in on the discussion. I should be posting the next track of the week later on Monday.

The facts as I remember them:
This was taken along the beach in southeast Alaska (in an area with no black bears) in mid April, I think at the hind end of the herring spawn (there were quite a few herring eggs lower on the beach). The bear trails went into and out of the woods at various points, I saw nothing to suggest that there was more than one bear making the trails, but didn't spend a lot of time examining them so it is possible. We did not see any bear tracks that were of significantly different size. I did not see evidence of where it had eaten, but again we did not spend a lot of time following the tracks very far, particularly as the snow disappeared in the woods and made trailing a lot more difficult. I also do not recall noticing any fresh bear scat along the beach.

The answers to the "official" questions:

2. Which foot?

I'll start with the second question. I think it is pretty clear this is a bear track due to its size and general shape, so with that understanding, this is the front left foot. The heel pad in a hind bear track will generally register much longer than in the front (the difference can clearly be seen in the second photograph). Additionally claws in the hind foot are generally shorter than what can be seen here.

On bear tracks the inner toe is the smallest (sometimes not registering in the track), here the left-most toe is bigger than the right-most (and all five toes are showing) so it should be the left track. Additional verification can be seen by examining the second picture and seeing that that foot is on the left side of the trail.

1. What species?

This is a brown bear track. One thing to note is that the claws are quite long, sticking pretty far beyond the toes. This is a common trait in brown bears, black bears generally have much shorter claws. From what I've seen long claws on the front feet are a common characteristic for many animals that do a lot of digging. This happens to be a coastal brown bear and I haven't noticed them doing a ton of digging (might be more my poor observation skills than anything else) but apparently the inland brown bears (grizzlies) do a fair bit of it.

Another trait to notice is that if a straight line is drawn from the bottom of the outer toe across the top of the heel pad the innermost toe will generally fall at least halfway above the line. A black bear's line of toes is usually more curved and its inner most toe will fall more below such a line.

Now, in response to the discussion in the comments:

I would like to note that I am excited to have such advanced discussion going on, I was definitely not expecting it. Some of it is beyond my ability to analyze at this point, so I will mostly leave that alone. What I will do is give my best interpretation of the tracks with the understanding that I am no great expert and my opinion isn't necessarily likely to be more correct than yours.

I'm not sure of the gait here, but I think that the bear was moving slowly, stopped and looked to the right. The positioning of the right front foot so far out on the left edge of the picture as well as the way there are two right hinds between the right fronts and the way the left front is closely surrounded by hinds, but there is not another left front a similar distance back all contribute to me thinking that.

I thought it was interesting that there seemed to be consensus for some things commenters seemed to be relying on pressure releases for, but disagreement in others. The most commonly agreed upon thing (of the things that I can't verify) is that it was a female, which I am still curious to know more about the reasoning on.

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