Tuesday, February 15, 2011

The Story of Pronghorn 166

Last year about this time I witnessed the capture of a Pronghorn doe. She was spending the winter just west of Glasgow with a large group of other Pronghorn. She was singled out and captured by a crew using a helicopter and a net gun and then fitted with a GPS collar as part of a research project by Andrew Jakes. The number written on her ear tag is 166. I have previously posted about her capture and location over the summer.

A few weeks ago I received a phone call from Andrew. He had just completed a flight to see if the animals wearing collars for his study were still alive after this extraordinarily snowy winter that has been so hard on these animals. Surprisingly, most of his animals were still alive, but he informed me that 166's collar was emitting a mortality signal (if the collar does not move a certain period of time, the signal changes so that researchers know the animal is most likely dead).

The news wasn't entirely unexpected with the number of animals dying this winter. However, what he told me next was rather remarkable.
Andrew told me they thought she was next to the highway and that she had probably been struck by a vehicle.

That wasn't the remarkable part; lots of Pronghorn have been struck and killed by vehicles this year.
The remarkable part was where it happened.
The mortality signal from her collar told us she was about 9 miles west of Jordan, Montana near highway 200. This location is approximately 70 miles south of where she was captured last winter and in between was Fort Peck Lake and miles of rugged Missouri River Breaks habitat not generally known as winter habitat for Pronghorn.
I had just driven that highway a day earlier and went right past her. My path and hers had crossed again, although at the time I didn't know it. I had noted a number of dead antelope on that trip and I even thought I might know exactly where she was at.

Ten days ago Kelvin Johnson, FWP biologist from Glasgow, and I headed south to find her. We found plenty of Pronghorn on our drive south, all gathered together trying to make it through the winter.

The animal I remembered in the ditch was a buck and about four miles for the spot we were given. About a half mile from the location, we found the remains of about four road killed Pronghorn and figured she must be in this group. The receiver picked up no signals and none of the heads we could find had an eartag. We continued down the road to our given location and found a lot of Pronghorn wintering just south of the highway. But we didn't find 166. No signal. Nothing.

This is the area we were searching in.

We walked around a bit and went to the top of the ridge near the location, and turned the antenna in all directions, but still no signal. We headed home disappointed to not have found her and speculated a number of different ways to explain why we couldn't find her. My sentimental favorite was that she had just stayed curled up for so long that the mortality signal had kicked on but she was still alive and now was wandering around further south. There were two other live Pronghorn with collars in the area (both had made a similar trip as 166), but we didn't pick up the signal from those animals either. Maybe the receiver wasn't working well. Maybe.....

Another flight early last week put to rest my idea that she was still alive. The location of the mortality signal was a bit elusive, but it was still there. A new location, not that far from the old location, was passed my way.

Last Friday I was once again heading down this highway on my way home. I really wanted to be the one to find 166. She had become a special animal to me so I borrowed an antenna from the FWP biologist in Billings and a receiver from another FWP biologist in Roundup and headed north. I had gotten out of town much later than I had wanted and it was starting to get dark when I got near the new location. I knew that the signal on the collar quit for portions of the day but I didn't know when that was. I told myself that if I put the antenna on the receiver and wasn't able to pick up a signal, I would have to try again another day. It was quite cold and blowing when I stepped out of the car and turned on the receiver. I tuned in the frequency, plugged in the antenna and immediately heard loud beeps coming from here collar. I was very close.

The signal directly led me down the ditch on the north side of the highway about a quarter mile when I noticed a leg sticking out of a snow bank and then the top of a Pronghorn head. I pulled the antenna off the receiver and waved the receiver over the head. No signal. Must not be her but I know she is close. As soon as I put the antenna back on the receiver it became very apparent that the antelope I was looking at had to be her. I brushed the snow back from around her neck and there was the collar. I had found her. It was close too - I later found out the transmitter was scheduled to turn off at 5:00 pm and the time on my photos was 4:46.

Above you can see the back of her head with the yellow ear tag. There was a small chunk of wire stuck in the eartag - a testament to the trials these animals undergo each year during their migrations. The prior week she must have been too well buried in the snow for us to pick up a signal from her collar.

Above is a GoogleEarth map where I plotted the known locations we have of 166 from the VHF transmitter on her collar - where she was captured (in the middle), her summer location (top, just north of Limerick, SK), and her final location (bottom) - a line nearly 170 miles long. It was amazing how near her capture location was to a straight line between her summer spot and the point of her demise. But the more interesting part is going to be when we get the GPS locations from her collar to see what she did in between those points and the path she took to get that far south after the snow started. So - more to come regarding the story of Pronghorn 166 and her extraordinary journey.


Carin said...

Wow John, wonderfully written, it was great to hear her story. So sorry for her ending, such a tough year for the antelope. It will be interesting to see her complete travels she took. Thanks for sharing her story.

Clare said...

Nicely told John. Perhaps a magazine article is in order. It is a story that deserves a wide audience.