Posts Tagged With: home range

On the Road Again

For much of the spring and early summer, the job of tracking most of the female fishers isn’t all that difficult. Denning females spend a lot of time in their dens, so we usually have a specific point for starting our searches.  When they go out foraging, we know they will need to return to their den eventually, and often aren’t found too far away from these sites.

As we move into June and July, the kits grow quickly and become more mobile. The time spent in any one den becomes shorter, and females are out and about more and more. Keeping track of them starts to become more difficult. Once August rolls around, we often observe some larger movements, many of which take the females outside of the areas we have tracked them over the last many months.

This pattern of females making larger moves around this time is something we notice every year, but the reason is not fully known. Possibly, this has to do with them depleting the easy food sources closest to their dens, and these moves take them to better hunting grounds.

Another hypothesis for this move is that females are taking their kits to the edges (or outside) of their ranges to let them become familiar with an area for them to “disperse” to. Especially for any juvenile males, it is not advantageous for them to remain near their mom’s home range, so making a move to get the kits away from her range makes sense. Whatever the reason, it’s fun (although often frustrating) to track them in some different areas.

By now, the juveniles should be very close to dispersing (if they haven’t already) and being on their own. We will begin our trapping efforts in a few weeks, and it will be exciting to see if we can capture some of these youngsters, especially in the areas that we are seeing the adult females traveling to.

69940map

2015 VHF locations for 69940, a two year old denning female. Blue stars indicate locations from January until the middle of August.  At that point she took off to the southwest. Green stars show her locations from middle of August into the middle of September.

Juvenile fisher from the end of August. Getting big!

Photo of a juvenile fisher taken at the end of August. Getting big!

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Categories: Field Day | Tags: , , , ,

“Fire Ferocious”

“Fire! Fire! Ferocious fire! 
You restless wall of flame. 
Fire! Fire! Roaring higher! 
Your fury to never tame.”

                                     – Mark R. Slaughter

 

Fire is an omnipresent threat to both individuals and populations of fishers. Fires that burn very hot can devastate the over story trees and with them the places where fishers forage, rest, and den. So, we are always aware of the potential effect that a large fire might have on our relatively small population of reintroduced fishers.

In the last week a fire just to the east of our study site (the Chips fire) has been putting up a lot of smoke and growing ever larger. Presently, the fire doesn’t directly threaten any of the fishers we are tracking, but its western boundary is within 5 miles of at least 2 females. Since the fire began on July 29th it has grown to nearly 16,000 acres and is not predicted to be contained for at least another 2 weeks (see the link already provided).

If you examine the included map you can compare the current area of the fire to the area where the majority of our female fishers have been found (blue dots; these data are incomplete and unedited) and where they have denned (black crosses). Though I have not delineated individual females in this figure you can see that a fire of similar area positioned in the middle of the study site would encompass a large number of dens and female home ranges.  Additionally, when you consider the fire shown here is relatively small (the largest wildfire can be over 100,000 acres) you can begin to appreciate how easily a single fire event could have dire ramifications for any fisher population in the west (in particular reintroductions).

Hopefully, the Chips fire will have little (preferably no) effect on our reintroduced fishers, but as with most things, we just don’t know what will happen. Fishers are obviously not the only species that are threatened by fires (marten are found in or near this fire), but they are our primary focus in this forum. Eventually, fire will likely have some impact on this incipient population. Those impacts will be related to the population size and spatial distribution of the animals. With luck, the population will grow and expand so that it can withstand perturbations such as wild fires.

Map comparing the area of the Chips Fire to female fisher locations

 

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