A mothers work…

I’ve recently been going through some of the pictures that we get from the cameras we place around the dens of females.

20058 sniffs a young tree before going out to forage

We place cameras at these dens to get estimates of how many kits females have, and I think we’ve done a pretty good job doing that (as evidenced by some of the images we have shown in previous posts). One of other benefits though is that we learn (sometimes) about what female fishers are catching to eat and even how often they are foraging.

Two of our females have been particularly informative this year. They live at different elevations, in different vegetation types, and have different litter sizes. One female fisher was captured on camera bringing back a wood rat, a lizard, eggs, and a few other items that we could not identify. The other female returned to her den primarily with squirrels of different varieties. I’ve included a few of those photos in this post. Both these females (released in year 3 of our study) were foraging at all times of the day and very often can be seen leaving the den to go foraging just after brining a food item to their den. Sometimes these two females were returning with prey items 3 times day and these are just the events we capture on cameras. These observations provide support to something we already know about fishers – they are very flexible in the food they eat and they forage often.

20058 returns with a woodrat

20058 returns with egg


2189C returns with squirrel

2189C returning to her den with unknown prey item


Fishers grow quickly in addition to having high metabolic rates. Thus, females must nourish themselves and their young almost constantly. Particularly as the kits get older they need large amounts of energy, and females with large litters are strained even more – a mother’s work is truly never done.  The consequence is that females must forage a lot and they expose themselves to risks, like predators (more on this in another post), a higher proportion of their time compared to periods when their energetic needs are not so high. If females can catch large prey items, assuming they are available, then they do not have to forage quite so often and can spend more time at the den with their kits. We still have work to do before we can quantify exactly what all fishers (including females in dens) are eating on Stirling and how this might affect their future success. In the meantime we know that most of our females make it through lactation and that at least some of their kits are also making it. The information we are getting from dens and den cameras is just another important way we better understand how fishers are making a living in the Northern Sierras.


Categories: Updates | Tags: , , , , , , | 3 Comments

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3 thoughts on “A mothers work…

  1. jan johnson

    Hi Aaron – such cool stuff. That image with the ‘unknown’ prey item – does that look like a kit?? looks almost like a small martes…

    • aaronfacka

      I can definitely see a resemblance to a kit or smaller Martes species. Unfortunately, the cameras we use are only 3 megapixel (which is generally just fine) but not for fine detail at this distance. A few reasons that lead me to think its not a kit. First, its too small for kits at this stage. By early June the kits are nearly 2/3 the size of mom. Second, she is coming up the tree and not down (this is not obvious from a single picture). If you look closely, which is hard to do, you can see that the tail is rounded and fisher tails tend to be more pointed or frayed looking. The snout is also kind of short and proportionally the eyes are larger than a fisher. The reason I called it “unknown” was because I couldn’t decide if it were a flying squirrel a ground squirrel or even a chipmunk. Anyone out there that can ID it definitively get a gold star. Thanks for the observations.

  2. Beverly Fontaine

    Hi Aaron and Crew – As a Mom myself, I can absolutely verify the fact that we are very flexible in the food we eat, and we forage often. lol Thanks for the great pictures and blog up-date. Bev

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