Tracking Fisher Behavior with Non-Invasive Methods
1. Taylor Luneau
5/10/12
Utilizing Non-Invasive sampling methods in documenting the distribution and
behavior of Martes Pennanti
Abstract
Tracking and photographic stations offer a non-invasive sampling method when
studying mammals with large home ranges like Fisher (Martes Pennanti). Fisher, found
most commonly in lowland mixed coniferous forests, are characterized by their similarity
to the weasel family, but with a stockier, elongated muzzle and rounded ears fixed close
to a triangular head. Their preferred solidarity and large home ranges make the Fisher an
elusive and difficult animal to study. However tracking can be implemented as a means
to understand their large home ranges and identify significant features in their
microhabitats. Once sign has dictated a high activity level of fisher in one confined area,
photographic stations can be used to document fisher behavior and characteristics. The
use of this kind of sampling method avoids any chance of injuring or tampering with the
natural behavior of the animal, thereby limiting ethical concerns and scientific bias.
During the period of February 12th to April 12th, 2012 two locations were observed for
fisher behavior. Both sites were identified by Susan Morse at her research facility in
Jericho, VT where she currently maintains the longest running track and sign survey in
the country. Once cameras were strategically set in view of these “hot spots” they were
checked once a week for data collection. Fifty-eight pictures were taken during the two
month period with a total of twelve separate visits by fisher, five occurring at site one and
seven occurring at site two. All of the pictures revealed behavior consistent with scent
marking and was appropriate for the time considering March has been noted as the most
active time in the fisher breeding season. The non-invasive techniques used were
successful in collecting non-biased information about the presence, characteristics and
behavior of fisher within our transect. The continued use of non-invasive sampling
methods is imperative in the conservation of the mammalia species and furthermore
detrimental to the preservation of genetic and ecological diversity in the Northern woods
of New England.
Introduction
Many species of the genus Martes can be found north of 35 degrees latitude,
where snowfall envelops their natural habitat for a large portion of the year (Proulx,
2006). When considering possible techniques in documenting the elusive mammal, one
must strongly consider the use of tracking in combination with photographic stations
positioned strategically at well-traveled corridors. Scientists have employed the method
of tracking in the past as a means to document the presence of fisher (Martes pennanti) in
diverse habitats as well as ascertain specific behaviors and monitor population trends
(Proulx, 2006). The presence of snow provides a well-defined substrate for the fisher to
leave its trail behind and allows trackers a suitable means in documenting the fisher’s
place in space and time. Snow is not the only substrate suitable for this job; in fact sand
2. 2 Taylor Luneau
and mud can be employed in the absence of snow but are far less abundant than the thick
white blanket provided by northern winters.
Development of new, more technological methods has discouraged many
scientists from implementing tracking as a means for mammal documentation (Beauvais,
1999). For instance with the dawn of radio-telemetry, many scientists have preferred the
use of radio collars when studying animal movements and behavior (Proulx, 2006).
However similar to live trapping, the animal must be restrained, anaesthetized and
otherwise marked in order to study and record the animal meticulously. Other than the
many ethical concerns which accompany this invasive practice, the simple disruption of
the animals natural behavior may present scientific challenges as well. The use of baiting
at a live trap, for instance may cause an animal to stray away from its natural habitat to
investigate the unknown food source (Proulx, 2006). This invasive method creates a bias
when assessing the animal’s natural movement across a particular landscape through the
alteration of its normal behavior and trajectory.
We must therefore consider the benefits gained through using a non-invasive
sampling method such as tracking. Not only does the technique afford a more specific
measurement of an animal’s movement through microhabitats, (in comparison to radio
collars) but a fine scale analysis of resource use, foraging behavior and scent marking.
Furthermore, tracking and photographic stations, unlike radio-collars or live traps, offer a
non-invasive method to observing mammals without otherwise harming the animal or
altering its behavior (Pulliainen, 1982).
Tracking and photographic stations can offer valuable information about Martes
and how they utilize their winter habitats. Male fisher home ranges average around 8^2
miles while females average closer to 6^2 miles (Douglas and Strickland, 1987).
Tracking, while time intensive, provides a finer analysis of the fisher behavior and
minimizes their large range distribution to a series of “hot spots” where photographic
stations can be implemented. Fishers are usually found in mixed forests with continuous
overhead cover (Powell, 1993). Specifically, in the Northeast of the United States fisher
have demonstrated a strong selection towards lowland coniferous forests containing
spruce, fir, white cedar and some hardwood forests (Powell, 1993). Their choice in
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5/10/12
habitat is most likely a result of their preference in food availability and denning sites
(Douglas and Strickland, 1987).
As a member of the weasel family, the medium sized mammal is characterized by
its stocky build, elongated muzzle and rounded ears set close to a rather triangular head
(Powell, 1993). The fur of the fisher is highly dependent on the individual as well as the
season and sex of the mammal (Powell, 1993). During the winter months, when this
study was undertaken, the fisher has primarily a dense, black coat with lighter colored
hairs around the face and shoulders (Powell, 1993). There is also high sexual dimorphism
within the species as males typically have a larger body size and more pronounced
physical weight than females (Powell, 1993). This dimorphism may allow the two sexes
to easily coexist within the same habitat through sharing available resources that are of
great demand. For instance as carnivores, Fisher prey primarily on snowshoe hare,
squirrels mice and porcupines but will occasionally forage on berries as well (Powell,
1993). Dimorphism therefore aids in leveling demand between sexes for restricted prey
within their selected home ranges and affords plenty of denning sites for both males and
females.
Based solely on our understanding of Fisher preference in home ranges and food
demands, we can narrow our search for fisher tracks to lowland mixed forests. With this
information we can utilize tracking to identify the presence of Fisher and then further
investigate to find areas of high traffic such as denning sites, scent marking stations or
food sources. Once our investigation has yielded a potential “hot spot” of activity, we can
then proceed to using photographic stations to obtain a greater understanding of Fisher
behavior in their natural habitats. This process provides a non-invasive, un-biased means
to the examination of Fisher populations and behavior and thus provides us with a less
stressful alternative to other techniques. If this traditional technique is used in accordance
with highly stringent data collection and analysis, a more proficient means to assessment
of the ecological needs of Fisher can be determined.
Methods
Establishment of transect
4. 4 Taylor Luneau
Our intent in documenting Fisher behavior, led us to choosing transects in low
land mixed coniferous forests. These transects were located at Wolf Run, a research
facility operated by Susan Morse, where she has collected data on mammal species,
varying from black bear to bobcat and fisher, for more than 36 years; making it the
longest running track and sign survey in the U.S. (Keeping Track). Susan had recognized
these particular transects as ones that would provide habitat connectivity and wholeness
as well as noted keen marking behaviors and track identifications. Two particular “hot
spots” were chosen as valuable areas for photographic stations. The valuableness of these
spots were due to the high density of fisher tracks as well as the high likelihood of being
scent-marking stations.
Tracking
When detecting Fisher track and sign there are clear characteristics which one
must take in to account during the identification process. Firstly we must recognize the
matter by which Fisher move through out their habitat. The movement of Fisher is quite
typical to the weasel family (Powell, 1993). Characterized by a bounding gait, the
forelimbs, moving together with one slightly ahead of the other, leave the ground just
prior to the landing of the hind feet. The track of the hind feet, therefore overwrites that
left by the fore feet (Morse, 2011). In good substrate we will notice four slightly
asymmetrical toes with the presence of a fifth off set toe on the medial side of the print
(Morse, 2011). Behind these toe impressions will be a knobby, interconnected upside
down “C” that corresponds to the palm pad of the Fisher (Morse, 2011). One may also
note a small round impression behind the palm pad, this impression is caused by the
carpal pad and can only be found on the fore foot (Morse, 2011).
5. Taylor Luneau
5/10/12
Figure 1. Depicts the tracks left by Martes pennanti. l.f. stands for left fore while l.h.
stands for left hind (Taylor, Raphael, 1988). Fore feet prints average around 4in long
by 3 and 1/2in. wide; hind feet prints average roughly 3in long by 3in. wide (Morse,
2004). The length between bounds averages between 12-50in (Morse, 2004).
While the tracks of fisher will most often be found in a two by two pattern, other
configurations are quite probable. Track sets of three or even four may exist as the Fisher
walks or runs through its environment (Morse, 2011). It should also be noted that
backtracking should always be used when investigating the distance and directional
changes of any mammal tracks. If forward tracking is used shortly after the tracks are
laid, an animal could be pushed to change their behavior, direction or habitat in response
to the investigators pressure (Proulx, 2006).
Locating possible scent marking stations
Tracks identified as Fisher may lead to highly disturbed areas noted by Morse as
“shuffle marks” (Morse, 2010). These shuffle marks correspond to flattened areas in the
snow where fisher have rubbed their bodies or possibley rolled around (Morse, 2010).
The use of urine or feces is also common in scent marking behavior and should be looked
for when encountering possible scent stations (Morse, 2010). Many fisher scent stations
6. 6 Taylor Luneau
can be found on elevated surfaces such as rotten logs, sticks or rocks (Morse, 2010). The
absorbent nature of rotten logs provides a good natural substrate for obtaining and
holding scent for a long time and should therefore be investigated intently (Morse, 2010).
Belly hairs as well as “tar-like” secretions from Fisher perianal glands may be
distinguished as well at these stations and will provide further evidence to the presence of
Fisher (Morse, 2010).
Documentation and use of photographic stations
Once possible scent stations were acknowledged the use of Reconyx game
cameras were employed to document the area. Reconyx hyperfire game cameras were
mounted on surrounding trees located in clear vision of probable scent marking stations
at Wolf Run. Documentation of the sites of interest occurred from February 12th, 2012 to
April 12th, 2012. Cameras were checked roughly once a week in order to record
visitations of mammals and preserve pictures taken. A computer was taken in to the field
when checking the cameras and after removing the memory card of the cameras, content
was observed to note changes in visitation and use. At the culmination of the experiment
only pictures of Fisher were used in collective data sets and interpreted for the mammals
behavior.
Results
Fifty-eight pictures were taken during the two-month period lasting from February 12th to
April 12th 2012. The photos analyzed are a cumulative set between the two sites of
interest and had a total of twelve separate visits, five occurring at site 1 and seven
occurring at site 2.
7. Taylor Luneau
5/10/12
Figure 1. Represents the percent of total pictures taken on each visitation. This
illustrates the varying activity levels of Fisher within our transect during our two
month study period. Note that two visitations occurred during March 5th but have
been grouped into one sample.
0
0.05
0.1
0.15
0.2
0.25
0.3
12-Feb
14-Feb
16-Feb
18-Feb
20-Feb
22-Feb
24-Feb
26-Feb
28-Feb
1-Mar
3-Mar
5-Mar
7-Mar
9-Mar
11-Mar
13-Mar
15-Mar
17-Mar
19-Mar
21-Mar
23-Mar
25-Mar
27-Mar
29-Mar
31-Mar
2-Apr
4-Apr
6-Apr
8-Apr
10-Apr
12-Apr
Percentoftotalpicturestaken
Date of Visitations
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
12am-1am
1am-2am
2am-3am
3am-4am
4am-5am
5am-6am
6am-7am
7am-8am
8am-9am
9am-10am
10am-11am
11am-12pm
12pm-1pm
1pm-2pm
2pm-3pm
3pm-4pm
4pm-5pm
5pm-6pm
6pm-7pm
7pm-8pm
8pm-9pm
9pm-10pm
10pm-11pm
11pm-12pm
Percentoftotalvisitations
Time of day
11. Taylor Luneau
5/10/12
Fisher not only visited the sites at varying intensities through out the month but
also at varying times. Referring to Figure 2 we note that fisher visited the sites most often
between the hours of 6 and 7am. Visitations during this period of the day account for
more than 33% of the total visitations recorded. Sixteen percent of the total visitations,
the second most, occurred between the hours of 6 and 7pm. Also note worthy, was the
varying temperature that unexpectedly fluctuated through out the two-month span.
Temperatures averaged around 27 degrees Fahrenheit during each visitation however had
a low of 3 degrees Fahrenheit on March 5th and a high of 45 degrees on March 8th.
As noted by Powell, fisher are characterized by their stocky and elongated build,
triangular head, dark fur and small rounded ears. From this we can quickly infer that the
pictures presented in Figures 3-7 are all of Fisher (Martes pennanti). What seems more
difficult however, is discerning differences between male and female sexes. As discussed
previously, males typically have a much larger body size and pronounced physical weight
than females (Powell, 1999). However Douglas and Strickland also noted significant
differences in both length and weight of juveniles in comparison to the much larger adults
(Douglas and Strickland, 1987). Males, who are generally spermatic by twelve months,
undergo an enlarging of the Testes during the winter months and reach their largest in
size by March (Douglas and Strickland, 1987). We can see in figure three what appear to
be enlarged testicles of the male fisher placed directly atop of the stump that it is perched
on. We should also note the large size of it’s tail and hind end which largely resemble
that of the size of the fisher in Figure 4. The size of the tail and hind end of this animal
largely resembles that of the male in Figure 3.
While a striking resemblance exists between the Fisher portrayed in Figures 3 and
4, there appears to be a strong difference between those and Figure 5. Here we note a
shorter and less wide tail, and more importantly a much slimmer body. The fisher in
Figure 5 is discernable smaller than that of 3 and 4 and should therefore be referred to as
another fisher entirely. The sex of this fisher is difficult to determine due to lack of
critical evidence, however based on the characteristics provided we can assume that the
Fisher in Figure 5 is either an adult female or a juvenile of either sex.
The Fisher seen in Figure 6, which strongly resembles that of Figure 4, has taken
a very similar pose to that of Figure 5. The animal in Figure 6 clearly has a much larger
12. 12 Taylor Luneau
body, head and tail size when compared to that of figure 5. This is further evidence
leading us to believe that the fisher in Figure 5 is probably not an adult male. We can also
see in Figure 7, a fisher that is laying out across the stick in the middle of the frame. This
behavior, or a similar one, was observed in each visitation depicted in Figures 4-7. In
each visit, the face, belly or groin was rubbed on the stick protruding from the fallen log.
This behavior was documented in several pictures on each visitation. Furthermore we
note the behavior seen in Figure 5 and 6, and observe the fisher pressing its nose firmly
against the same stick that had been rubbed against. This behavior was also observed in
each of the visitation depicted above.
Discussion
The utilization of non-invasive sampling methods has been shown by this study to
provide not only verifiable documentation of the presence of Martes pennanti, but also
defining characteristics as well as defining differences in behavior. The traditional
method of tracking was employed in discovering fisher sign and identifying important
features in the fisher’s microhabitats. After determining these important features, the
implementation of photographic stations further expanded our understanding of fisher
characteristics and behavior. Not only did this non-invasive technique avoid harming the
animals in any way, but it also documented the animals in a non-biased way by
maintaining the natural behavior and trajectories of each fisher.
Due to the clear likelihood of the Fisher in Figure 3 being a male, we can suggest
that the fisher seen in Figures 3, 6 and 7 are also male due to the large similarities
between the animals. We can also suggest that the believed male fishers are all one and
the same. Due to the larger energy requirements of males, their home ranges tend to be
disproportionately larger than those of females (Powell, 1999). For this reason home
ranges of the same sex tend not to overlap (Powell, 1999). However, home ranges of
opposite sexes tend to overlap extensively which Powell termed “intrasexual
territoriality” (Powell, 1999). The animal’s territory is comprised of resources, such as
food and mates, and will often be prioritized by only one male (Powell, 1999). While
Powell asserts that the use of scent marking can deter male-male aggressive interactions
by claiming territory ownership, Douglas and Strickland discovered that evidence of
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intraspecific fighting existed and occurred 37% more often between adult males than
adult females (Douglas and Strickland, 1987). It would therefore make sense that the
male fisher observed in this area would be the only male documented due to our transect
being far smaller in size than the predicted home ranges necessary for more than one
male fisher.
Based on the evidence provided that limits the possibility of more than one male
in a specific territory, we are led to believe that the fisher appearing in Figure 5 is a
female. The slender build of the animal and the clear differences in body shape when
compared to that of Figures 3, 4, 6 and 7, suggest that the fisher in Figure 5 is actually a
different animal. However if this is possible, why do the two animals share such similar
behaviors? Both appeared very interested in the sticks at site 1 and 2 and for some reason
rubbed up against them during each visitation. Furthermore, both of the fisher pressed
their noses against the sticks, a behavior which is most likely in accordance with
smelling, multiple times during each visitation.
What is believed to be occurring is the process of communication through scent
marking. Powell noted the likelihood of fisher during the winter to approach and drag
their bellies across stumps protruding from the snow (Powell, 1999). This behavior,
which is also clearly seen in Figures 3-7, is noted as scent marking by Powell. It is
presumed that the abdominal, plantar and perianal glands located on the animal, secrete a
“tarry” like substance which provides valuable information to other fishers in the area
(Feldhamer et. al, 1984). This includes information about the sex of the animal as well as
the sexual activity, maturity and perhaps territorial behavior (Powell, 1999). This
information of sexual activity, aimed towards mates, reaches it’s most abundant during
the breeding months of late February through mid April (Coulter, 1966). During mid
March, the increase in fisher activity appears to be correlated to the breeding season, and
as Powell notes, is highly dependent on elevated levels of male testosterone (Powell,
1999). The believed scent marking in Figures 3-7 are in clear agreement with the fisher
breeding season and behavior as well as the high sexual activity of male fisher during the
month of March.
The information provided by this study has given a clear look into the scent
marking behavior of Martes pennanti and determined our transects as significant
14. 14 Taylor Luneau
breeding zones for the animal. With this in mind, we can assess the habitat surrounding
our transects to obtain a greater understanding of the ecological necessities for a specific
habitat to support a breeding fisher population. For instance, we may find that the hare
population within the surrounding area is optimal in supporting the caloric demands of
multiple fisher. We may also determine that there is an abundance of hemlock in the area
where fisher will cache their food; or perhaps a healthy abundance of yellow-birch where
fisher will nest in it’s cavities. Further studies should be conducted to obtain a more in
depth understanding of the fisher behavior as well as scent marking and mating rituals.
However if anything, tracking has provided us the simple understanding that the fisher
population in our study area is healthy enough to participate in the breeding season. From
this we can draw conclusions to why this habitat is able to successfully support this
population.
The use of tracking and photographic stations offers a powerful alternative to
newer sampling methods. The non-invasive means by which the method is carried out
and the unbiased results that it produces are un-paralleled. With Vermont, and much of
the rest of New England and New York, providing necessary habitat for fisher and other
mammals, it is imperative that we maintain habitat connectivity to support the health and
sustained growth of the mammals in our environment. Wide ranging species like the
fisher must be uninhibited when moving from region to region in search of resources like
food, denning sites and mates. We must continue to study these amazing animals to
obtain a greater understanding of their biological demands as a means to preserve genetic
and ecological diversity. The use of tracking and photographic stations as sampling
methods, are therefore necessary tools in the conservation and diversity of the biological
communities that surround us.
Acknowledgements
I would like to thank Susan Morse for sharing her tracking expertise and
mammalia knowledge with me. I am extremely grateful to Sue and Keeping Track
for allowing me to study the fisher population on their land at Wolf Run in Jericho,
VT and for also providing me with Reconyx game cameras to document fisher
behavior. Susan has taught me so much in the woods and I owe her a great debt.
Furthermore I would like to send a special thank you to Valerie Banschbach for her
guidance and assistance through out the duration of this project. My opportunity to
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study with Keeping Track would not have existed had it not been for Valerie, and for
that I thank you so much.
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