DENizens of the Trees

In the last 2 weeks we have managed to confirm that at least 5 of our females have settled into patterns consistent with denning behavior. We detected the first on about March 21 and that is the earliest we have detected a female in a den over the last 3 seasons (more on that  later). Three of the females were released in year 2 of the translocation. One of those females did not den last year and 2 did. The other females were those released in year 3. This is positive because it shows that the females from last year found mates and appear to have had kits. We demonstrated this last year with first year animals, but observing it for the second year adds data and understanding to important population processes. Matt observed a male fisher at female 1F111’s den tree already this year. This was a female released in year 3  and the den is about 11 km east of where we released her. I am still amazed that males show up at den trees seemingly right after females establish them, but since that is a male fishers specialty I guess I shouldn’t be surprised at all.

Black oak den tree

The dens are spread across a big swath of the district. From the west side in the Big Chico Creek Drainage to the east side near highway 70. We even have one female denning on the north side of Deer Creek. We still have a lot of females that have yet to den so it should be interesting to see the distribution of their dens when all is said and done.

Den tree (on right) of female 1F111

The first two years of the project  the earliest we ever found a den was March 23 and most were found after April 1. This year we have found 3 dens before March 23 and another 2 before the 26th, One reason for this might be that we have better access to where females are because we have had relatively little snow accumulate over the winter. The last two years we were snowmobiling/snowshoeing into dens through much of April. Alternatively, the relatively mild winter might have simply allowed females to den a little bit earlier (some anyway) because they were in a better condition. At least three of these females appear to have never given birth before (based on past tracking and physical examination), and this could influence their body condition and timing of birth. All of this is speculation of course, and the bulk of females have yet to den so we might just be observing natural variation in timing of births. It will be interesting to see if other studies detect earlier than usual denning behavior.

We’ll be putting cameras on all the den trees we find to document when females move their litters to maternal dens and to make minimum estimates of their litters sizes. More information to come….

A view of the area immediately adjacent to a fisher den

Categories: Updates | Tags: , , , , , , , , | 1 Comment

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One thought on “DENizens of the Trees

  1. jan johnson

    Love what you’re doing here Aaron! Thanks for sharing 🙂

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