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Thursday, July 28, 2011

Black Bear Swats Cub

I have posted photos from my Father's camera trap before. He has property near Wayland, NY and uses no scents or other attractants. Here are two more that are worth sharing:

Black bear and cub
(Wayland, NY 6/11)
In this first black bear photo, notice the cub in the tree in the upper right corner. The photo is from the last week of June. This is the third year in a row that this location has produced black bear photos. That is an apple tree right behind Mom, but the apples are far from ripe. Perhaps she is just checking out the scene to determine whether it is worth coming back for fruit later in the season. I plan to check that tree for cub claw marks :)

Black bear swats cub
(Wayland, NY 6/11)
This second photo is an action shot. It appears that Mom has just given the cub a swat and the cub is recoiling. Of course, we can only speculate on the reason. I assume this is a disciplinary action. Was the cub not supposed to climb that tree? Maybe the cub was supposed to have stayed in the tree! Perhaps the swat has nothing to do with the tree at all. Is it time to wean the cubs? If so, this may be Mom's way of saying "No milk for you!". Although we can never know what went on, this remains an interesting photo and one worth sharing with you all!

Wednesday, July 27, 2011

Black Bear Trail Research PART III: Stride and Straddle Results

This is the third post regarding the black bear research my class conducted this summer in Massachusetts. Please review the first post here and the second post here. Today's post will concentrate on the measurements we took of the ritualized portion of the trail.
Measuring the straddle or width
of a black bear trail
(Massachusetts. 7/11)
Before I present results, let's make sure we all agree on terminology. "Straddle" is the same as the trail width. "Stride" is a little more confusing. Some authors measure stride from one track to the next track left by that same foot. For example, you could measure from a right rear track to the next right rear track. Other authors measure stride in a walk from one track to the next track. In the case of a direct register walk like our black bear, this would mean you are measuring on the diagonal, from a right track to a left track. Finally, some authors measure from the front of one track to the front of another track and some measure from the rear to the rear. In theory, this shouldn't matter. The key would be consistency. Check the book you are using for that author's particular methods.

As the photo to the left shows, we used Popsicle sticks and toothpicks to outline the deep, habitually used footfalls (I went into a little detail on an earlier post as to how we decided on the placement of the track within the deep impression). Then a wooden ruler could be placed on the edge of two tracks in order to properly measure the straddle or width of the trail. For the stride, we measured from the rear of one footfall to the rear of the next. In other words, we measured the distance from a right foot to a left foot, not a right to a right. Some authors would call this a step rather than a stride. We only measured a small portion of the habitualized trail. All measurements are in inches:
Stride (or step): 27, 26.75, 23.25, 26.5, 18
Straddle (or width): 15.75, 14.25, 17, 15.5, 17.38, 15.5

For a direct register walk, Rezendes (1999) gives a range of 17-23 for stride and 9.5-14.5 for a straddle. Elbroch (2003) posts numbers only slightly different at 17-25 and 8-14 respectively. Three of our five stride measurements exceed even Elbroch's larger figures. In addition, five of six straddles are above what would be expected. These results alone are interesting as they suggest the bear is not walking in a "normal" walk when creating these trails (or at least this one segment of this particular trail). However, there is a greater significance to these numbers that Nick pointed out to us while we were in the field.

Think: As stride increases, straddle should decrease. In other words, as I stretch out my steps, I would also be narrowing the width of my trail. Think of how an animal's trail looks in a walk compared to a run. A running animal can leave a trail that is only as wide as its tracks. Elbroch gives strides and straddles for a trotting bear as 27-37 inches long and only 6-10 inches wide. See what I mean? A bear's foot is about 5 inches wide, so a trotting bear is almost stepping in a straight line. But the results we obtained showed the opposite. The stride was elongated AND the width was increased. Visualize what the bears must do in order to use these trails. They are stretching their limbs farther than in a normal walk as well as placing their feet wider than they normally would. As I attempt this across my living room floor, I feel very uncomfortable and am reminded of a reptile rather than a mammal.
FLCC Black Bear Management Class 2011
(Paul's Ash Tree, 7/11)
What is the significance of this? Unknown. But if the other trails Nick and Val work with are similar, it sure seems as if the bears are modifying their normal gait when creating these trails. Why? Does this increase the chances that the bear will be able to straddle a tree and deposit scent? Is it a visual display? Does it increase muscle strength? So many questions, so few answers. I think that is the essence of research...

Wednesday, July 20, 2011

Black Bear Trail Research PART II: Camera Trap Results

This is the second post regarding the black bear work my students did in early July in Massachusetts. You really should check out my first post here before you read this post :)

On our second day with Nick, we returned to the same location as the day before in order to retrieve our cameras and take some measurements of the part of the trail that showed clear, repeatedly used footfalls. Nick led us along to the location leisurely, providing interesting natural history facts along the way. As we approached the trail, we had kind of strung out into two groups, separated by about 10 yards.  I was in the second group when I heard someone ahead of me yell "BEAR!". When I looked up, I could see a black bear changing direction to move away from us about 20 yards ahead. The perspective from the members of the first group was even more dramatic: we had actually walked up on a black bear using the ritual trail! The lead group was literally ten yards from the bear before the people noticed it. The bear was so focused on what it was doing that it didn't notice us either. We all got great views of the bear as it walked away from us and dissolved into the forest.

Black bear using ritual trail
(Massachusetts,  7/11)
Seeing the bear was amazing, but it was also important for our research. First, we had camera traps set at both ends of the habitually used part of the trail. We disrupted the bear before it got to the second camera location, but s/he walked right past our first camera (my first camera trap of a black bear, BTW). The camera was set at the edge of a wallow. In the photo, that would be to the right. However, this bear skirted the far edge of the wallow and started in on the ritual trail dry. The time and date stamp on the photo to the right are correct.... it was so dark in the forest the infrared flash went of causing the photo to be colorless. As you can imagine, the students and instructors alike were pumped. This was far more than we had bargained for! I had already warned the students that measuring black bear sign is far easier than actually seeing the animals. Now I fear they are spoiled, but to put it in perspective, Nick told us that in his eight years of measuring these trails, this was the first time he ever saw a bear actually on one.
FLCC students measuring fresh black bear tracks
(Massachusetts, 7/11)
The other aspect of this encounter that was so useful for us as researchers is that we now had actual footprints to measure. I watched as several students placed their hands in the freshly made tracks in a show of empathetic tracking. It was a powerful moment for us and really connected these divots and marks on the trees to the flesh and blood animals that made them. To use the trails "properly"(meaning that a bear would put its feet into the existing footfalls on the trail) requires the bear to walk in what is called a direct register. This means that the rear foot falls into the track made by the front foot. In essence, this means the front track is destroyed or covered, so we were only able to measure the size of the rear track. Exclusive of the claws, the rear track measured 5 1/4 inches wide and 7 1/4 inches long. This is a good size track for an adult black bear. In the photo above, you can see that we have used toothpicks to outline one of the tracks.

Measuring footprints of black bear, Brian Cole (left) and
JVN (right) (Photo by: Sasha Mackenzie, 7/11)
Nick said something interesting on our first day together. His many years of measuring the bear trails has lead him to believe that the way they are putting their feet down when using these trails is different than "normal". He feels that the length of the stride and straddle (width) of the trail indicates the bear is doing something other than walking in a relaxed manner (and more in a ritualized way). Rather, the numbers do not "add up" with the numbers he gets when measuring a bear trail say in the mud or snow, in an area where there is NO ritual trail. We adopted Nick's method for measuring the steps and trail width. We used toothpicks and Popsicle sticks to outline the tracks when they were visible and we centered an imaginary track into the deep, existing footfall when a fresh track was not present. Our results bore out what Nick had stated: the stride and straddle simply did not match what would be expected of a "normal" gait when compared with the published literature. I will discuss how we interpreted those results in my next post.

Black bear using ritual trail
(Massachusetts, 6/11)
More Camera Trap results: We mailed Nick two camera traps before our trip. Regular readers of this blog know that I use Cuddeback Capture cameras. We chose to send him two IR cameras so there would be no visible flash to interrupt the bears' behavior or to alert it to the presence of the cameras. This means any low light images will be in black and white. Results? Nick placed the cameras on two different ritual trails for five days before we arrived. One camera produced no bear results, but the other captured two images of black bear on the trail. Whether this was one bear photographed twice or two different bears, we may never know. Here are those images:
The first photograph is from June 29th at 920 am. This looks to me like an adult bear. Young bears give the impression of having large ears because they have such a small head by comparison.
Black bear photographed using a ritual trail
(Massachusetts, 7/11)
The second photograph is from several days later and used the IR flash. What clues would I have to tell if this was a different bear than the one from the 29th? They were captured in such different poses that it is difficult to tell size properly. Nick felt that maybe there was a difference in the muzzle between the two bears, but I lack his experience and am not confident in making that determination at all.
Black bear using ritual trail
(Massachusetts, 7/11)
I shared the photograph of the bear we saw at the beginning of this post. Please note that that photograph was taken many miles away from these others, on a completely different ritual trail. We left a camera with Nick when we left and he placed it back in the location closer to his home, where he had already gotten the above two photographs. Nick emailed me a few days ago and sent me two more photos from that trail. He agreed to leave it out "until the snow flies" so it will be interesting to document the activity on that one trail. See that large tree in the center of the photos, behind the bears? That is a marked tree with scratches, bites and evidence of rubs. It may only be a matter of time before we get a nice image of a bear adding to the marks..... Sure wish I had video :)

Sunday, July 17, 2011

Black Bear Trail Research

FLCC Black Bear Management Class
Mohawk Trail State Park, MA 7/11
In early July, my Black Bear Management class traveled to Massachusetts to work with Nick and Val Wisniewski of Walnut Hill Tracking & Nature Center. The trip was funded through a grant by the National Science Foundation. Specifically, we wanted to see how Nick and Val conduct their research on specific kinds of black bear trails. Typically, these trails are heavily marked with scratched, rubbed and bitten trees and the bears that travel on them step in the same spots each time, making deep depressions in the soil. There is no universally accepted name for the trails but Paul Rezendes and his students coined the term "ritual trail". I have heard them called habitual use trails, mark trails and last week a man from Alaska told me that when he was a boy, they called them "hot foot trails" (and were made by brown bears). I have extensive photos posted in a Picasa Web Album here. Take a look and it will give you a much better idea of the markings associated with these trails (and will save me from reposting so many photos to this entry).

We arrived mid afternoon and got ourselves settled in to the campground. The campground is well forested and bordered on one side by the well-named Cold River. Sasha and I had planned a mini-study to get the students used to taking measurements, recording data, recognizing bear sign and generally thinking like researchers. We took the students along the campground road and showed them how many of the telephone poles had bear bites on them. After inspecting about ten poles, we sat at some picnic tables for a few minutes and started brainstorming questions we could ask and data we would need to take to answer those questions.
Black bear bite on telephone pole
(Mohawk Trail State Park, MA 7/11)
We decided that a good starting point would be to quantify the number of poles that were bitten, how many bites on each pole and the height of the highest and lowest bites. In addition, we noticed that some of the poles had wires running down them and although all the poles are treated with creosote, some really reeked of the stuff. We felt those were reasonable variables to take into account that may influence whether a bear was willing to bite the pole or not. I photographed each bite and experimented a little with using a transparency sheet to help identify each bite photo as shown at the left. I will post our results in another entry later...

Nick Wisniewski shows a bear bite
(MA, 7/11)
The next morning we got up early, had a quick breakfast, met up with Nick and headed out to see the "ritual trail" we were going to study. On our way to the trail, Nick pointed out a variety of wildlife sign. We saw moose tracks, coyote scat and of course, bear sign. Nick pointed out a tree that had been bitten years ago by a bear. This provided a nice contrast to the bites on the telephone poles since those do not heal.  One myth I hear over and over again is that bears will stand on their hind legs and bite as high as they can so that smaller bears will be able to measure themselves and know to stay away. I cannot say for sure that never occurs, but I can say for sure that bear bites can be found very low off the ground, as if done from all four legs.

Bear scratches on a birch tree
(MA, 7/11)
When we reached the ritual trail, the students fanned out to look at the amazing amount of sign present. We found scat (relatively fresh), scratches, bites, straddle trees and of course, the well worn foot steps that give the trail its name. We had three camera traps and decided to place one at either end of the trail. One of the questions we wanted to answer was whether bears used the trails in one direction or two. This particular trail is about 40 yards long and is dominated by a large birch tree with several years of bear sign. We gave the students a chance to absorb the scene and ask as many questions as they wanted. After about an hour, we continued hiking, stopped for lunch and eventually made it to another section of ritualized footsteps. But these appeared to have gone cold and not in use.

Patty Wakefield and Nick inspect a heavily marked red pine
(MA, 7/11)
This second trail was in a red pine stand and some of the trees were heavily scratched. It was interesting to note how different the pines looked compared to the birches. We saw beech trees with climbing scars. We crammed as much into our day as possible. By 5pm, we were back at the vehicles saying good bye to Nick and trying hard not to get our hopes up about the camera traps. Since they were only going to be set for 24 hours, we really did not have a great chance to capture a bear in action. We returned to the campground, swam in the Cold River, cooked dinner in a rainstorm and fell asleep dreaming of bears... Next post: Our results.