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