Covering ground

By Mark Nale

- For the CDT

The fisher field research that began in State Game Lands 26 at the juncture of Blair, Bedford and Cambria counties is ready to expand into other areas.

A statewide study on fisher disease and food habits will conclude this summer, and another population study is about to begin in the Allegheny National Forest. Accurate population data could lead to the development of limited trapping season for fishers.

Indiana University of Pennsylvania is partnering with the Pennsylvania Game Commission on this three-year study of fishers, which began in August 2006. According to Dr. Jeff Larkin, the IUP biologist who heads the research end of the project, much has already been learned about the predator’s population density, habitat preferences and home range.

Fishers are medium-sized members of the weasel family, which contains skunks, river otters, pine martins, mink and wolverines. Their elongated bodies measure 30-47 inches and they weigh 5-14 pounds — the weight range of a typical house cat. Fishers are mainly nocturnal, resting in trees during the daylight hours. Four of the 24 radio-collared fishers died during the study. Two early mortalities were attributed to rabies and a possible road kill and, according to Larkin, more recently a male fisher with a broken leg was found dead in his den. The IUP team consisting of Larkin and three graduate students also examined evidence that a large owl had killed a female fisher.

“The batteries powering the radio transmitters on those remaining from our original 24 radio-collared fishers stopped transmitting last July,” Larkin said. “But we got exactly what we wanted from that first phase of our study — we got a good idea of the fisher’s home range.”

According to Larkin, the average home range for the female fishers was 1.66 square miles, while the well-traveled males covered an average of 7.26 square miles.

“On an annual basis, fishers share habitat, but we don’t know if two fishers use the same habitat at the same time,” Larkin said. “We just didn’t have enough data to determine that.”

Determining the home range was important as they move into the next phase of the study — a fisher population study in the Allegheny National Forest. Graduate student Hance Ellington will be conducting most of the field research in the ANF. In order to conduct the population study, the IUP team is planning to use hair snares to collect hair samples form individual fishers that live in the ANF. Learning the fishers’ habitat preferences and home range will help Ellington efficiently place their hair collecting devices in the correct habitat and the home ranges will help to determine how far apart he can place the hair traps.

“We used Geographic Information Systems forest-type data and the fisher project’s past findings to help us determine where to sample in the Allegheny Forest,” Ellington explained. “We will be placing 200 hair snares — two in each of 100 predetermined habitat cells.”

Hair snares, which were tested in and around SGL 26, are made from short pieces of 8-inch diameter black plastic pipe. One end of the pipe is baited and closed and three 30-caliber bore brushes are set inside, pointed toward the center. The brass brushes capture hairs from any animal that enters the pipe to investigate the bait or lure and then exits.

Because of DNA technology, only a hair sample is necessary to identify an individual fisher. The first hair sample constitutes the “marking” phase of a population study, and a “recapture” is made when a second hair sample is collected from the same fisher.

According to Larkin, with hair snares, there is less stress on the fishers because they are not handled. It takes less manpower to monitor the snares and one researcher can cover a much larger area.

“The only drawback to the hair snares is the cost of DNA analysis,” Larkin said. “The initial screening costs $13 and determines if the hair is from a fisher or not. A full DNA profile costs $100 and provides an individual identifier for each animal. All samples are run at the U. S. Forest Service’s Rocky Mountain Research Station in Montana, with the cost covered by our grant. “We are still waiting for the DNA results from our last group of fisher hair samples from SGL 26, and we are hoping for some recaptures. We need recaptures to get a reliable population estimate.”

Graduate student Sean Gess finished his radio-collared fisher field work last October and is currently analyzing his data. During his research, Gess identified 79 daytime resting sites, 55 of which were in large living trees. Many of the living and all of the dead trees contained some type of cavity. He shared some of his preliminary findings with Pennsylvania Outdoor News.

“My studies show that fishers tend to prefer older, more complex forests — less disturbed areas with lots of downed woody debris,” Gess reported. “The average dbh (trunk diameter at breast height) of trees selected for resting sites was nearly twice that of trees in non-selected areas. There seemed to be no preference for a particular tree species, and northern versus southern slopes didn’t seem to matter, either.”

A third IUP graduate student, Crissie Webster, is examining fisher carcasses to determine diet and the presence of three diseases — rabies, toxoplasmosis and sarcocystis. By examining the stomach contents of fishers killed accidentally by trappers as well as those from road kills, Webster has discovered a wide variety of food items.

“One stomach contained only blackberries and another had only venison, but most contained the remains or parts of multiple species,” Webster said. “These included a groundhog, a downy woodpecker, mice, pheasant feathers, a squirrel, a cottontail rabbit, chipmunks, raccoon, part of another fisher and even the paw of a red fox.

“Although one of our radio-collared fishers died from rabies early in the field work, none of the 30 fishers that I examined has tested positive for rabies. I found that interesting and even more interesting was that, even though there is no published data of fishers having toxoplasmosis, 100 percent of the fishers that I studied contained toxoplasmosis antibodies, which means that they had been exposed to the disease at some time in their lives.”

Larkin is quite pleased with the research thus far. Gess is finishing up his habitat/fisher resting site work, Ellington will begin his population field work in the Allegheny National Forest this month, and Webster needs the results from her 10 most recent road-killed fishers to finish her disease and diet study. As a side benefit, Larkin hopes that these studies will lead to a more efficient sampling protocol that can be used all over the state. When this research is over, more will be known about the fishers’ numbers, habitat requirements and habits in Pennsylvania. Mark Nale, who lives in the Bald Eagle Valley, is a member of the Pennsylvania Outdoor Writers Association. He can be reached at MarkAngler@aol.com.