Posts Tagged With: Argos

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.

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First male captured.

Getting a weight.

Getting a weight.

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Categories: Field Day | Tags: , , , ,

Warm winter nights….and happy endings.

When you wake up in the morning, you never really know what the day is going to have in store for you.  We do, after all, carve out our niche in the world by following the daily habits of small furry critters in a predominantly wild landscape.  We often grow attached to our fuzzy wards (how could we not?).  So when something in our data collection portends trouble for one of them, we mobilize to see what we can do.

Males that we capture and deem healthy enough to carry the weight sport ARGOS collars.  These collars communicate with orbiting satellites to determine the collar’s location and the satellites then relay location information via email right to my laptop.

There’s me in the corner!

Armchair biology.  Technology!  While this sounds like a road to obsolescence for field biologists, we still need to track the collar (and fisher) down when the data tells us something is amiss.  The collars are only on during certain times each day, and during this window the collar transmits once a minute to the satellites.  We’ve got a nifty receiver that lets us track it down via strength of the signal and distance from the collar as it transmits.

Male 190 was released in December 2011, and has been with us a little while.  He’s often seen at female den trees during mating season, and all in all, he’s just a sturdy, well built fellow.  It was distressing, therefore, to see some of the data from his collar suggest that he might no longer be with us.  To figure out if 190 was ok Julie and I looked into when the collar transmits and, lucky for us (sarcasm), it transmits from 5PM – 9PM and again from 1AM-5AM.  With the weather being wet as it has been for a time, we knew it was going to be an interesting hunt.  Just what we enjoy, if you can believe it.  We hoped for a dropped collar, and tried not to think about finding a carcass.  It was wet, getting dark, and we were heading into uncertain terrain.

Andria volunteered to go out hunting with me.  With the rain and the wet muddy roads, going in by truck was out of the question. Not to mention our only access was a long and partially closed road that would have required chainsaws, and more time (and daylight) than we could afford.  So ATVs were on the menu.  We knew the area we were headed to, and had a rough route planned (no one had visited this area since the rain, so all routes are tentative).  After dropping the trucks and heading out on the ATVs we began hearing the signal we had hoped for.  We continued on our pre-planned route, as a time or two doing this has taught me that signals broadcast up from a creek bottom can give misleading readings from a ridge top.  Along the way we had to move downed trees and rocks.

After getting all the way down to where our most recent data suggested 190 may be, we could hear no signals from the collar.  This had me daring to think that maybe, just maybe, he’s still alive – but somewhere other than where the recent points told us he might be.  We rushed as best we could back to the top of the ridge and posted up for a few minutes.  Lo and Behold, the signal boomed in to our receiver and continued to change in direction and intensity, quite quickly.  He was not far from where we randomly stopped, doing his thing and probably oblivious to our racket!  

Relief.   Elation.  High fives.  Back to the truck.  We were able to get out there, nose about, and determine that this guy is still hanging around, though probably weathering the worst of the rain in a tree hole somewhere, shielding the collar from reaching the satellites.  A good nights work, and home before 10PM.

 

UPDATE 2/15/2014:  Activity data from collar came through tonight and shows good readings across the board.  Sweet.

Categories: Updates | Tags: , , , , , , , , ,

On The Road Again

A lot of what we talk about and report on is our female fishers. I suppose there are a lot of reasons for that but a major one is that we usually track our females and most of our males wear Argos transmitters produced for us by Sirtrack. The great thing about these transmitters is that we don’t have go out and do the tracking. The location is estimated through overhead satellites that transfer the data to a processing center that then sends it to us in our email – what some have dubbed “armchair biology”. One of the really important reasons we put these on males is because they allow us to track fishers over long distances.

Male fishers have big home ranges compared to females and they seem to cover a lot of area. Here, I have included a figure that shows data that we have collected on 4 males from the last 3 months (not all our males are included here). You can see from the points that they do a pretty good job of staying away from home ranges of other males even when when they share a common border and have some overlap. Just for fun I included a visual representation of a Kernel Density Estimator for female fishers. Basically, the darker colors are where female fishers are found the most. As you might expect there is a some overlap between males and females, but some males are somewhat off by themselves. It makes sense the the biggest most dominant males have home ranges that include more female’s home ranges, but we are still testing this hypothesis.

The locations for 4 selected males

Yesterday Kevin described the frustration of not being able to find animals that “disappear”. The information we are getting from our Argos collars have been really informative with regards to showing us the fishers sometimes do seem to just go exploring. Just recently we have had two males that have seemed to wander away from their usual haunts. Had we been tracking these animals with regular VHF telemetry it is likely we would have just “lost” an animal for awhile until it eventually showed up again. We know females take these same types of trips, but I suspect we catch them in the act far less frequently.

If you look below at the two other figures  I’ve included you can see male 1 and male 4 have each recently taken petty significant jaunts. Male 1 only recently set out toward the east. He has covered about 10 miles in the space of about a week. The other male made about a 20 miles round trip over the course of about a month. Notice that he wandered right through the middle of one of those dark red areas – the home range of one of our females released in year 2.

What do these trips represent for a male fisher? Well, that is another thing we are still thinking about. Maybe they are checking out locations of females. Particularly with the breeding season fast approaching it may be useful for males to keep track of potential mates. Perhaps they are simply looking for an area that has higher concentrations of prey or maybe, like ourselves, they just want to see some place new once in a while.

Male 1 recent movements

Male 4 recent movements

Categories: Updates | Tags: , , , , , , , , | 2 Comments

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