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.


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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A better mouse trapper

Fishers, like most mustelids, are predators. Unfortunately, the food available to them versus what they kill and eat are often unknown to researchers. We have dedicated a good chunk of our summer trying to understand better what is available for fishers to eat compared with what they actually select on our study site. This summer we had several folks out trapping and documenting potential prey species for fishers across the Stirling district. Many people were involved but we had three excellent field crew out there doing most of the work. Alex, Erika, and Jesse (see their lovely photos below) were out most days setting and checking traps in diverse types of cover and tree stand types. The point of all this is to attempt to understand where specific types of prey are found on the landscape based on differences in the environment and forest management practices.

We are just starting to examine these data to document and explore specific patterns of occupancy and distribution for different prey species. Nevertheless, we encountered many different species of mammals, birds, and herpetofauna (snakes and lizards mostly) across the landscape thru the summer. We captured deer mice (Peromyscus spp.) just about anywhere we set traps, and woodrats (Neotoma spp) also occupy diverse land covers types. We do not catch them as often as deer mice, but they are still abundant. The crew also captured ground squirrels (Otospermophilus beechyii), Douglas squirrels (Tamiasciurus douglasii), various chipmunks, and even hapless ringtail (Bassariscus astutus). While setting and checking traps they also kept an eye out for lizards and snakes. A few of the snakes were of the venomous variety (rattlesnakes) as well as snakes that are not quite so dangerous but just as cool. Alligator lizards and fence lizards also seem to be in lots of places as well. Other types of potential prey species like gray squirrels, black-tailed jack rabbits and flying squirrels were also noted but seem to be harder to capture in live-traps.

Of course, when you put a lot of fresh peanut butter and oats out in a forest you get other critters that are interested. Bears are a common visitor and they are usually unconcerned with maintaining the integrity of our trapping grids. They move, turnover, often destroy, and at other times even steal traps! Bears are one of our nemeses both when doing this kind of work and just about everything else (they are everywhere). We also see foxes and occasionally we even see a fisher wander across a trapping grid.

The crew is primarily taking data on where we capture specific types of animals. They also document the sex and relative age of each species, measure the weight, examine them for ectoparasites and  give them marks and tags so we can document which individuals we have recaptured. We are also collaborating with Deana Clifford and the Wildlife Investigations Lab to evaluate some captured animals for rodenticides and diseases. All these data are important to future analyses and monitoring.

Vegetation types are also important and we

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collect information on the number of trees and shrubs that occur on each trapping grid. Sometimes the crew accidently document other species of plants. They often don’t’ know this until a day or two later when they realize they have a poison oak rash and then must bear the burden of scratching and itching for several days. It’s a badge of honor. We all wear it proudly at one point or another – except for those people lucky enough not to be affected (we are all looking at you Jesse) – if not without a large degree of annoyance.

Good times were had by all and more importantly we have collected new and interesting information that will help us conserve and manage fishers and fisher forests.

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Young of the Year

It’s been nearly 3 months since we found our first dens of 2015, and we’ve been busy continuing to try and track females and get pictures of kits.  It hasn’t always been easy, and many of the females this year managed to move out of their natal dens unseen.  However, our persistence has finally been paying off over the past few weeks.  So far, we have confirmed a total of 19 kits from 11 denning females!  This averages to 1.7 kits per female, which is on par with what we have found in previous years. Mostly we’ve seen fishers with either 1 or 2 kits, although we did confirm a 3-kit litter from one female.

It’s enjoyable to me to see how fast the kits are growing. In just the last couple of weeks we have started to see some of the kits climbing down trees on their own, and playing around outside of dens (with adult supervision).  In some instances, the kits seem to be following mom to the new den instead of her carrying them.  It also appears from the photos that the females are starting to bring back more prey items to the dens.

At this point, it is very difficult to pin new maternal dens down. The females are out foraging the majority of the day, and since the kits are becoming more mobile it is probably easier for her to pack up and move to a new home.  There are still a couple of females from whom I think we have missed seeing a kit or two.  We will continue to opportunistically walk in on everyone to try and get as accurate of count as possible before the juveniles dispersal in the fall.

Below is a slideshow of many of the kits we have confirmed thus far. I have tried to put them chronologically so you can get an idea of just how fast these fishers are growing up. The first picture is from April 3rd, and the latest from June 8th.  Also, a camera from a log den found about a week ago captured hundreds of images of a female eating a squirrel while her kits were around! I put these into a slideshow you can watch HERE.

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Happy Birthday Dear Fishers…

Likely a little belated in most instances (and possible early for a few others), but mid-March to early-April is the time when fishers’ give birth to their kits. Our oldest on-air female just turned 8 years old, while the oldest male we are tracking turned 9!

This is a busy time of year for us on the ground. We try and locate the den-sites for all females who are old enough to have kits. In addition, we set up and maintain motion-censored cameras at all of the dens, attempting to get a glimpse into activities around the den as well as detect kits once a female chooses to move to another den.

This year, we are tracking 18 females who could potentially den and have kits. Thus far, 13 individuals are exhibiting behavior consistent with denning (staying in the same tree over multiple days). In addition to females giving brith, spring is also the time of year when breeding occurs. Males are busy roaming around trying to find the females, and often end up at their dens. As such, our camera’s have been takings lots of really interesting photos.

I made a “motion picture” from the photographs of one remote camera over the course of a few days at a natal den, which you can view HERE.  Also below are a few pics from various dens so far. Enjoy!

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Shh! Don’t Wake the Bears

A fair amount of the sampling we conduct throughout the year includes us using some kind of bait and/or lure to try to attract fishers to a certain area. As you might guess, many other animals are attracted to these smells and the prospect of a free meal. Some of these critters may end up stealing our bait or getting caught in traps (thus preventing fishers from entering). However, this is more of a slight annoyance, and pales in comparison to the usual impact of the black bear. Throughout much of the year black bears are a common visitor, and their presence is often obvious. Not many other animals can completely disassemble a wooden/metal trap, or tear a track plate box into 10 pieces. In fact, bears cause so much destruction, we frequently use a word that you may have never heard of to describe the carnage:

beared, v. having been altered from function by the actions of a bear.
“The trap was beared, and it took Kevin 20 minutes to find all of the pieces that were strewn about 50m downslope of the original location.”

We’ve tried to construct ways to mitigate their impact. At one point while doing camera surveys, we even drilled 2x4s to trees about 8-10ft up. These extended ~6ft out away from the trunk, and bait was hung about a foot above the end of the board. These “run poles” attempted to allow only a small, good tree climbing animal access to the bait. Many bears were unfazed by the challenge, and eventually would succeed in getting the free food. Don’t get me wrong, I still like bears. They are awesome animals and I always enjoy getting a glimpse of one out in the woods. However, they do cause us lots of frustration. In the end we usually just grin and bear it, because there really isn’t much we can do to stop them.

Throughout the winter, most of our time is spent simply trying to get daily estimated locations of fishers. It is also a time where we catch up on going through our massive collections of pictures from remote cameras that were taken during other times of the year. So although many of the bears are still sleeping out in the woods and not currently bothering us, we relive their destruction (and ultimately our frustrations) that are caught by our cameras.

I thought I would share a few photos of some of the bears more destructive moments.

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Spot Trapping

At the end of our Fisher Frenzy last fall, most of us were pretty satisfied with the fruits of our labor. We had captured more fishers than in any of the previous years’ efforts, affixed all of our available VHF collars on females, caught a good crop of juveniles, and all of the fishers we examined seemed to be in pretty good health. What else could we ask for?

Well, there was one question that I couldn’t get out of my head – Where are all of the adult males? We only captured three, and knew of a 4th that was on the air but never captured. This is in contrast to 17 adult females caught during the same time period. Of course, we expect to find fewer males due to their larger home ranges, but only capturing three adults? Something seemed wrong here.

After we finished up our main Fisher Frenzy, the team here continued to run a small number of traps, attempting to target particular fishers that avoided capture. For most of December and January, we didn’t have much success. We kept recapturing fishers that we had caught during the Fisher Frenzy, but the target fishers wouldn’t enter our traps.

However, to our delight a couple of weeks ago, we caught a fisher that we had never seen before. It ended up being a large 4.8 kg male!  He was in excellent condition, and we put a collar on him. He was in an area that we aren’t currently tracking any other adult males (but we did have plenty of traps in this area during the Fisher Frenzy).

Starting to wake up.

Starting to wake up.

Dustin and Pierce monitoring the first male captured.

Dustin and Pierce monitoring the first male captured.

Fast forward three days later. In the exact same trap, another unmarked fisher was captured. Once again, it was an adult male! This guy was slightly smaller than the first (4.3kg), but was also in really good condition. We put a collar on him as well, and let him go.

Capturing these males was important for a variety of reasons. First off, it will allow us to gather some location data on them so we can see what areas they occupy. Secondly, it reinforces to me that there are fishers out there that can go undetected for years, and that we aren’t catching all the animals that are out on the landscape. We won’t know the exact age of these males for a while, but based on their size and developed sagittal crests, both of these guys were probably older than two. This means they avoided capture during the Fisher Frenzy 2013 and 2014, and possibly even 2012. Of course, is could be simply that they spend most of their time outside of the main Stirling tract, and were just now passing through the area for some reason (perhaps scoping things out as we get nearer to breeding season). We don’t have the resources to trap many of the areas adjacent to Stirling, so any fishers occupying those lands might go undetected. Hopefully their collars will give us many good locations over the next year.

Personally, it eased my fears of something more serious going on with the males. It’s hard not to go through all the doomsday scenarios after not catching very many. Possibly they simply aren’t as prone to entering traps as females, or maybe many males are partially occupying areas we don’t end up trapping. Whatever the reason, it was a welcome relief to capture these two guys.

Sean babysitting as he was starting to wake up.

Sean babysitting male #2 as he was starting to wake up.

Andria, Roger, and myself waiting for the drug to take effect.

Andria, Roger, and myself waiting for the drug to take effect.


First male captured.

Getting a weight.

Getting a weight.

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On this day

Today (December 9th) is a special day for me. Five years ago today I recall walking down a snow covered mountain road holding one end of a wooden box that contained a fisher. Holding the other end of that box was Roger and right beside us walked Richard and Scott – also holding the ends of a box the held a fisher. Our destination was a small clearing in the forest where many of our friends, colleagues, and even members of the media awaited us. More precisely, they waited for the fishers. The two female fishers we carried in those boxes would be the first 2 fishers released as part of our translocation project onto the Stirling district. We placed the boxes near the edge of the clearing and opened the doors and waited, and then we waited a little more. All the humans eagerly waited for the fishers to emerge from those boxes, but the fishers had other ideas. I can’t say I blame them. Having a bunch of beady-eyed humans looking at you can’t be a fun situation for a fisher (or any other creature either I imagine). I suspect we all, especially the members of the media, had a great illusion that the fishers would emerge promptly and slowly, pose for a few pictures, and then saunter away at a leisurely pace while we snapped pictures and looked on in awe. The reality was quite the opposite as both fishers, in their turn, streaked out of their boxes as a flash of brown into this new place they we hoped they could make into a home. Seeing the fishers run off gave a sense of great accomplishment and wonder but also of great responsibility and future hard work. I suppose Scott provided the most sobering perspective of the day (to me anyway) when he simply said “There are now fishers in the northern Sierra”. Yep, there sure were and that meant that we had to keep track of them, study them and also move an additional 38 fishers over the next 2 years.

Hill releasing fisher

Releasing a male fisher in December 2009


Female fisher looking out of release box

Two years later on December 9th I was once again standing in a big circle of people waiting for fishers to come out of wooden boxes. Once again the media (see link for one article and some pictures) was there as well as friends and collaborators of the project. The outcome was much the same as fishers sat in the boxes refusing to leave and when they finally did they fled with extreme expediency. We released 2 females and 1 male, and they would be the last of the fishers translocated to Stirling. Not all the releases were met with media attention or lots of people milling around waiting to take pictures. In fact, most fishers were released with just 1 or 2 people looking on and waiting. Personally, I prefer a small release entourage. In all cases, the releases were the easiest part of the whole process.

It might take me an entire book to write about the tremendous effort that it took to get fishers to Stirling. There are myriad stories about trapping, handling, and transporting fishers. There are just as many about long meetings and phone calls where we considered all the risks and benefits and tried to decide the best course of action, and for each story I have the rest of our team might have 20 more. Yet, all those stories and experiences would only tell a small part of the entire story, because there were literally years of planning and discussion that went into developing and creating the project and the collaborations that made it all work. Most of that happening long before I ever even knew about the project. So, while I consider December 9th the birthday of the project we should always remember that it had a very long gestation as well, and that process went without fanfare or appreciation. The days we released fishers, and how those days came to be, are only one part, and perhaps the least important part, of what our project is all about.


Some of the team handling a fisher before release

transport boxes in truck

Transport boxes full of fishers heading to Stirling

On December 10th, 2009, a day after we released the first fishers, Roger and I set out to find them. It was a mixed bag as we found one female within 1 km of the release point and had no luck finding the other. It took a few days, a few weeks actually, but we eventually found the other female. We tracked both of these females, as well as 7 other released in late December and January of 2010, throughout the spring. Both those two females survived and produced kits the first year as did most of the other females we tracked. Since that day we have spent nearly every day for 5 years looking for fishers to understand the specifics of how and where they live and reproduce. Of course, “we” isn’t Roger and I anymore. “We” is now a large number of folks that work, and have worked, in the field collecting data, and without them the project would not continue. It is also all the people behind the scenes and behind desks and telephones, in front of computers, in laboratories, and in many places and roles that make the project continue to work. The project would have failed a long time ago without all those many people and they all deserve a great deal of gratitude and appreciation. We continue looking for fishers and learning about their lives and ability to survive and reproduce on a landscape managed primarily for timber production. We don’t know everything, obviously, and though we’ve made great strides more information, time, and thinking is needed to fully understand the dynamics that drive fisher populations on Stirling. Nevertheless, five years later we know that there are STILL fishers in the northern Sierra Nevada.

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Fisher Frenzy 2014

We recently wrapped up our month-long fall trapping event (aka Fisher Frenzy).  This is the 4th year we have conducted this large scale trapping event, and 2014 proved to be our most successful to date.  Over the course of the month, we were able to capture 32 individual fishers!

We conduct this trapping effort for a variety of reasons.  First and foremost, it allows us to affix radio-collars on fishers.  Most of our collar’s batteries tend to last a little over a year, and thus the collars we put out in 2013 do not have very much life left.  The new collars we put out should last us until next year at this time and allow us to track the fishers throughout the year.  We also learn a lot by examining the fishers we do catch.  We can get an idea of overall condition, age, past reproduction, parasite load, and old or new wounds.  Sometimes, we even get the shock of seeing something completely unexpected, like imbedded porcupine quills!

On a more personal note, trapping is the time of year that we actually get to see fishers (as well as some of the other forest mesocarnivores) up close and personal. This is immensely enjoyable to me, as most of the year it’s rare even to get a glimpse of the fishers we are tracking on a daily basis.

As in previous years, we spent the first two weeks trapping the east side of the district before moving to the west side for another two weeks.  On the east side, we totaled 36 fisher captures of 24 individuals (18Female:6Male).  11 of these were fishers that we had never captured before (6F:5M).  Our success slowed down on the west side of the district, but we did manage 17 total fisher captures of 8 individuals (5F:3M).  Of these, 4 were fishers who had not been caught before (3F:1M).

In total, we ran over 2,700 trap nights!  We recaptured 17 fishers from previous years (14F, 3M), as well as picked up 15 fishers (9F:6M) that we had never caught before.  Our overall trapping success rate for fishers was 1.9%.  Besides fishers, we also capture quite a number of other animals in our traps.  We managed to catch 45 spotted skunks, 32 ringtails, 15 grey foxes, 3 striped skunks, 2 raccoons, and even 1 bear cub (luckily mom didn’t seem to be around).

Every year, there are a few wise fishers that manage to evade our traps.  At the end of trapping, we had 4 known on-air fishers that we did not catch.  Adding those animals to the number of fishers we did catch gives us a “minimum known alive” population size of 36 individuals.  Of course, it’s likely we are not capturing all the fishers that are out on the landscape (we are also not able to trap every area we would like to because it’s not logistically feasible).

In order to run trapping at such a large scale (~100 traps open per night), we require a large amount of personnel, time, and effort.  This year, we had over 25 people come out to help us with our daily trap checks and examinations! All of the project cooperators (California Fish and Wildlife, North Carolina State University, Sierra Pacific Industries, US Fish and Wildlife Service, and Wildlife Conservation Society), made large contributions to help pull this event off.  A HUGE thank you to everyone who gave their time and effort to help make this year’s trapping a success!

Here are a few pictures from this year:

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Getting the Point

Getting the Point            

October is long gone and the shortening days of November signal that fall trapping is coming to a close. Unfortunately, we have not been able to update all of you with the happenings as much as we’d like, but I suspect we’ll be putting out more posts in the coming weeks.

One of the parts of trapping, and handling fishers, that I most anticipate is in the moments after we’ve sedated a fisher and get to physically examine it for the first time. One of the first priorities is to  see if it has any major wounds or ailments that need immediate attention or that give us concern. Recently, while examining a female fisher (captured on Stirling in the fall of 2012) we noticed that there was something odd about the area around her right shoulder and neck. Not coincidentally Roger and Kevin both spotted the same thing when I did and all three of us were looking on at several very large, stiff, and prominent hairs jutting from the fisher. I found myself thinking ‘those don’t look like fisher hairs, and I wonder what they are?”. Kevin and Roger were apparently thinking the same thing and nearly in unison we shouted “PORCUPINE!”. A little further examination confirmed our suspicions. Three porcupine quills were embedded in the young female’s right shoulder suggesting she had an encounter with porcupine in the not too distant past.


Close up of 3 porcupine quills in right shoulder of female fisher captured on Stirling in 2014


Female fisher with porcupine quills in right shoulder

Perhaps you are wondering why such a fuss about a few porcupines quills? Well, there are a few reasons that this got us excited, but mainly it was because we have never found a fisher on Stirling with porcupine quills. The discovery is significant because fishers are one of the few consistent predators on the spike-laden rodents when they occur together. As  you probably know, or can deduce, porcupines have all those spikes as more than just a bold fashion statement – they offer pretty good protection from most predators (view a recent video of an African porcupine vs lions). Fishers are uniquely adapted to capture and kill porcupines and they may have an important role in regulating porcupine populations in some areas. Porcupines are large relative to other prey fishers catch and kill (e.g., squirrels and hares) and they provide a large source of energy to fishers (read this if you want to learn more). We have never documented porcupines on Stirling, since we’ve released fishers, and this suggests that porcupines are rare. Having porcupines and fishers on Stirling at the same time might alter the dynamics of how and where fishers forage, their home ranges size and structure, and even their population dynamics.


Porcupine (Erethizon dorsatum)

We don’t know if our female fisher actually killed a porcupine, but she certainly ran across one and we have a pretty good idea of the places she likes to hang out in. For now, it is only a fun little anecdote about one of the fishers on Stirling. Nevertheless, it is an exciting story and perhaps the first in a series of important observations. Such information is one of the reasons we endure a long trapping season and why we subject animals to the burden and stress of capture. Ultimately, it is all important information about what fishers are doing and how their daily lives translate into their ability to persist.


Depiction of a fisher capturing a porcupine (painted by Consie Powell)


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The Most Wonderful Time of the Year

Yes, I know the saying is generally reserved for a little later in the year, but that only applies to people who haven’t had the pleasure of trapping fishers in the fall. For those of us that have, and are about to again, the fall trapping season really is a marvelous time to be alive and doing field work. October 13th marked the beginning of our annual large-scale trapping and population monitoring effort on the Stirling district. Some have called this hectic rush to capture fishers the ‘fisher-palooza’, the ‘trapping blitz’ and sometimes just ‘fall trapping’, but I’ve always been fond of the term “Fisher Frenzy”. For those of you that have experienced it you’ll understand why I prefer this term — it really is a month-long frenzy. It is extremely enjoyable to set traps, capture and process fishers but it is always a grueling period where everyone is constantly busy and slightly stressed about everything that is going on.

On a daily basis we are deploying, checking, baiting, and hauling over 100 traps scattered across much of the study site. This may not seem all that bad except that it is critical that we check each and every trap once a day, at a minimum, and it takes a lot of thought and planning to make sure that we get this done. Each trap is usually about 1 mile from another and it can take 1 person half a day to check just 20 traps. In addition to fishers we catch foxes, ringtails, opossums, raccoon, and the bears are always investigating, rolling, and sometimes damaging traps too. If it snows or rains then that adds to both our comfort levels (have you ever spent all day checking traps on an ATV in the rain?) as well as the possibility we will not be able to get into our trap sites easily. The field crew (led by the intrepid Kevin Smith) has spent weeks fixing traps, finding locations, getting bait, and organizing routes and people. So, you can imagine they are already a probably a little stressed and maybe even sleep deprived, but they are doing an outstanding job.

I suppose I have’t made the experience sound all that wonderful to this point, but the reality is all the preparation and the daily grind is a very small price to pay for the experience and information we get from the fall trapping effort. Trapping fishers allows us to see, and examine, fishers that have been out on the landscape for the last year (or longer) and evaluate how well they are doing. It also introduces us to new fishers that have been born on Stirling and to get information on their condition, age, reproductive status, parasites as well as genetically identifying them. From the trapping data we can evaluate how much the population has grown, or shrank, and we can collar new animals so we can continue to track them.  So, we learn a lot about the fishers, and the experience is a great time as well. Being out in the woods and setting and checking traps is, at least for me, one of my favorite things about field work and I enjoy the experience immensely. It is also a time when the different members of our team get to be around each other and work together for a common purpose. We learn a lot and generally have a great time. So, as you read this some member of the crew might be leaning over a closed trap and hearing the muffled chuckle that a trapped fishers makes and seeing those lovely green eyes staring back at them from the trap. We should all be so lucky! With luck we’ll be able to keep everyone up to date on our trapping success over the next few weeks.

I’m enjoying myself like a kid at Christmas with a bunch of presents that are sitting out in the woods just waiting to be unwrapped. Indeed, it is the most wonderful time of the year.


Categories: Field Day

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