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22001155 SOUTHEASTERN NATURALIST 1V4o(2l.) :1345,1 N–3o6. 02
Efficacy of Trail Cameras to Identify Individual Florida
Panthers
Roy McBride1,* and Rebecca Sensor1
Abstract - We conducted a 2-y investigation to assess the efficacy of trail cameras to
identify individual Puma concolor coryi (Florida Panther). We established 35 camera sites
within the 28,328-ha northern Addition Lands region of Big Cypress National Preserve
from 1 January 2011 to 31 December 2012. To maximize the number of Florida Panthers
captured, we intentionally avoided the use of transects or grids for camera-site selection.
Instead, we placed cameras along known Florida Panther travel routes. We used a scent
lure at each camera site to encourage Florida Panthers to linger in camera range, thereby
increasing the opportunity to determine gender and observe anomalies that would aid in
identification of individuals. Our cameras captured Florida Panthers 2154 times, which
produced a total of 38,056 individual photos. We determined the identity of individual male
Florida Panthers in 93% of captures (n = 1190 of 1278). However, the absence of anomalies
in adult female Florida Panthers prevented us from identifying them consistently and with
absolute certainty, despite thousands of opportunities to do so. Therefore, we relied on the
morphological characteristics of dependent kittens to identify individual females in specific
instances. We feel that the modifications to the camera survey (i.e., cameras placed on travel
routes, high-quality digital cameras, and use of a species-specific scent lure) increased our
ability to determine gender and identify individuals.
Introduction
Using trail cameras to photograph Puma concolor L. (Puma) is not a new concept,
as evidenced by a 1937 camera expedition in Coahuila, Mexico, during which Stanley
P. Young and Tappan Gregory successfully photographed Puma in the wild (Young
and Goldman 1946). Since this early beginning, advances in trail-camera technology
have improved to the point whereby trained or untrained observers can easily document
Puma presence (Allen 2014, Allen et al. 2014, Dreibelbis et al. 2009).
Since 1981, we have attempted to enumerate Puma concolor coryi Bangs (Florida
Panther, hereafter Panther) by gathering physical evidence (e.g., tracks, urine
markers, kills, scats, and individuals treed by hounds) to determine a minimum
annual count (McBride et al. 2008). In 2004, we began to employ trail cameras in
the southeastern region of Everglades National Park (ENP) to augment our annual
survey work. Though it was easy for us to photograph Panthers, we found it difficult
to identify them as individuals, or even determine their gender, because often only a
partial photo of each animal was recorded as it passed quickly through the camera’s
motion-detector coverage area.
To address this problem, we incorporated a scent lure at ENP that encouraged Panthers
to linger at our camera sites, thereby increasing the number of photos produced
1Rancher’s Supply, Inc. - Livestock Protection Company, 26690 Pine Oaks Road, Ochopee,
FL 34141. *Corresponding author - livestockprotection@gmail.com.
Manuscript Editor: Joseph Clark
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per capture (Long et al. 2003, McBride and McBride 2010, Munoz-Pedreros 1995).
We hypothesized that multiple photographs would improve our ability to determine
gender and distinguish unique anomalies that would enable us to identify individual
Panthers. However, the limited number of Panthers in ENP did not allow a rigorous
test of our hypothesis. Therefore, we established 35 trail-camera sites within the
northern Addition Lands region of Big Cypress National Preserve (BCNP; NPS
2010), to determine if we could differentiate individuals in an area known to have
a higher Panther density (Belden et al. 1988, McBride et al. 2011). Identification
of individual Panthers can be used to enumerate populations, determine minimum
counts, and is essential for most mark–resight methods. Natural marks have been
successfully used to identify species that exhibit differences in pelage or other physical
characteristics (e.g., Panthera tigris L. [Tiger]; Royle et al. 2009). Furthermore,
mark–resight techniques have recently seen rapid improvements, with more powerful
and flexible likelihood-based methods which are readily accessible to researchers
and managers (e.g., Program MARK; McClintock and White 2011). Mark–resight
has previously been used to estimate Florida Panther densities (Pitman 2010, Sollmann
et al. 2013a), but the reliability for individual identification based on physical
characteristics was not explicitly assessed in those studies.
Field-Site Description
The 28,328-ha study area within BCNP Addition Lands contained a mosaic
of hardwood hammocks, Pinus (pine) flatwoods, Taxodium (cypress) domes, cypress
strands, seasonally flooded prairies, and marshes (Duever and Roberts 2013,
Duever et al. 1986, NPS 2010). The study area was surrounded on 4 sides by similar
habitat, also occupied by Panthers (Belden et al. 1988, McBride and Sensor 2014,
McBride et al. 2011,). Interstate Highway 75 (I-75) defined the southern boundary
of the study area. Specially designed wildlife underpasses facilitated safe passage
of Panthers beneath I-75 and into and out of the study area (Foster and Humphrey
1995, Jansen et al. 2010).
Methods
Equipment and camera-site maintenance
We maintained up to 35 Reconyx model PC900 trail cameras (RECONYX,
Inc., Homen, WI) in the northern Addition Lands region of BCNP. We chose
these digital infrared cameras for their fast trigger and ability to record multiple
photos per capture. Each camera was programmed to utilize the manufacturer’s
10 photos per trigger, RapidFire®, no delay setting. The cameras were equipped
with a passive infrared motion detector and a nighttime infrared illuminator for
both day- and night-photo captures.
We monitored cameras via an all-terrain vehicle every 14–21 days to retrieve
photos, check battery strength, remove obstructions (e.g., growing vegetation and
fallen limbs), and adjust cameras repositioned by Ursus americanus floridanus Pallas
(Florida Black Bear). We downloaded photos on-site onto a portable computer
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to assess camera function in the field and provide data storage for later analysis.
Photo data were stored and analyzed in an MS Excel software spreadsheet (Microsoft,
Redmond, WA) that included date and time of capture, camera-site number,
Panther gender, whether or not the Panther was radio-collared, number of kittens
(if present), and individual ID when possible.
Camera-site placement
To maximize the number of Panther captures, we intentionally avoided the use
of transects or grids for camera-site selection. Instead, we placed cameras along
known Panther travel routes (Allen 2014, Karanth and Nichols 1998, Logan and
Sweanor 2001) where we had repeatedly observed their tracks and urine markers
during 33 years of Panther survey fieldwork (McBride 1985, McBride and Sensor
2014). Strategic camera placement improved the likelihood that a Panther visiting
the study area would be captured (Allen 2014, Karanth and Nichols 1998). To
obtain optimal photos for individual identification, we attached cameras to trees
50–60 cm above ground level.
Lure
Based on our previous success using a gland-based scent lure (Livestock Protection
Co., Alpine, TX) in ENP (McBride and McBride 2010), we chose the same
attractant for this study. We placed the lure within 2 m of each camera site to encourage
Panthers to linger in camera range, thereby increasing the opportunity to
determine gender and observe anomalies that would enable identification of individuals
(Long et al. 2003, McBride and McBride 2010, Munoz-Pedr eros 1995).
Definition of Panther capture
When a solitary Panther passed close enough to a camera to trigger 1 diagnostic
photograph of the species, we defined this as 1 Panther capture. If multiple
individuals were photographed together, we counted that as multiple captures. For
example when a pair of adult Panthers were photographed together, we considered
it 2 captures, or if a Panther group consisting of a female and 2 kittens was
photographed, we considered that to be 3 captures, etc. If a Panther lingered in
the camera’s field of view and continued to activate the trigger, we called each additional
image a photo. Therefore a single capture could produce dozens or even
hundreds of photos. These photos maximized our opportunity to identify gender or
recognize an anomaly that could lead to individual identificatio n.
Gender and invidiual identification
Panther gender was primarily determined by presence or absence of testicles.
We made individual Panther identifications when we could observe one or more
unique markings such as scars, ear notches, cowlicks, crooked tails, and tick-bite
patterns (Allen et al. 2014, Kelly et al. 2008). We placed Panthers whose gender
we could not determine into a gender-unknown group. We distinguished some
females from one another based on morphological characteristics of their dependent
kittens, such as body size, ear length versus skull-size proportion, spot size
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and clarity, and tail markings (Fig. 1; Currier 1983, Hornocker and Negri 2009,
Logan and Sweanor 2009).
Figure 1. A. Female Panther identified by her two ≤2-month-old kittens that have distinct
dark spots and short legs, torso, and tail; B. Female Panther identified by her three
>4-month-old kittens that are distinguished by their fading spots and larger size (e.g., longer
legs, torso, and tail).
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Results
Gender
Our 35 trail cameras recorded 2154 Panther captures resulting in 38,056
Panther photos from 1 January 2011 to 31 December 2012. All camera sites (n =
35) recorded panthers on multiple occasions. The mean number of photos per
capture was 18 (range = 1–820). We were able to determine the gender of adult
Panthers in 98% (n = 1859) of adult captures (n = 1904). Sixty-seven percent
(n = 25,498) of Panther photos (n = 38,056) were identified as males and 31%
(n = 11,797) as females.
Male panthers
We determined the identity of individual adult male Panthers in 93% (n = 1190)
of male captures (n = 1278). We distinguished a total of 11 separate individual
males by either their unique anomalies (n = 7) or radio collars (n = 4) (Fig. 2). Of
the male captures, 70% (n = 898) were of uncollared individuals, 30% (n = 377)
were radio-collared, and we were unable to determine if the remaining 3 males were
collared. We could not identify individuals in the remaining 7% of male captures
(n = 88) due to photo angle, condensation on lenses, Panther distance from camera,
motion-blurred photos, or the absence of unique markings.
Female panthers
We determined the identity of individual adult female Panthers in 43% (n = 252)
of female captures (n = 581). Individual female Panthers were identified either
by their unique anomalies, radio collars, or morphological characteristics of their
dependents (Fig. 1). Of the female captures, 56% (n = 326) were of uncollared individuals
and 43% (n = 252) were radio-collared. We could not determine if Panthers
were collared or uncollared for <1% (n = 3) of female captures because their neck
areas were not visible in photos.
Discussion
Our research objective to identify individual Panthers with trail-camera photos
required us to develop a method to maximize the number of photos per capture to
increase our opportunity to recognize unique identifying features. Our method had 3
important components: (1) we strategically chose camera sites by placing them along
known Panther travel routes which were identified by re-occurring Panther sign (e.g.,
tracks, urine markers, and scat; Allen 2014, Karanth and Nichols 1998, Logan and
Sweanor 2001); (2) we used high–quality, digital-infrared cameras (e.g., Reconyx
PC900) capable of taking rapid successions of high-resolution images to capture
diagnostic images critical in identifying Panthers; and (3) we placed a proven scent
lure at each camera site to encourage Panthers to linger in camera range, thereby
increasing the opportunity to determine gender and observe features useful in their
identification (Long et al. 2003, McBride and McBride 2010, Munoz-Pedreros 1995).
Using a species-specific scent lure resulted in more Panther photos per capture
and did not attract non-target species (Long et al. 2003, McBride and McBride
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2010, Munoz-Pedreros 1995). We found that Panthers sometimes passed within
several meters of the lure without detecting it, which suggested that Panthers were
not drawn to our camera sites from long distances. However, we concluded that
when Panthers detected the lure, they stayed at camera sites longer, which increased
the number of photos recorded per capture. Lure effectiveness proved essential in
maximizing our ability to determine gender and observe anomalies that we used to
identify individual Panthers.
We were able to identify adult males with or without radio collars because each
individual exhibited unique, permanent morphological differences. The radio-collared
Panthers in our study area were part of telemetry studies that were ongoing in
a larger area. While the radio collars made it easier to identify the 4 collared male
Panthers, the absence of collars would not have precluded us from identifying them
using the same methods that we employed to identify the 7 uncol lared males.
Males were most often individually identified because of ear injuries (Fig. 2),
which were probably the results of fights with conspecifics (Benson et al. 2011,
Hornocker and Negri 2009, McBride and Sensor 2014). Although we were able
to identify uncollared males by anomalies, body wounds (e.g., lacerations and
punctures) often heal over time, leave little physical sign of previous injury, and
therefore are not useful in identification of individuals. However, ear injuries, e.g.,
notches and tears (Benson et al. 2011, Hornocker and Negri 2009, McBride and
Sensor 2014) typically do not mend completely, and often increase in size, area,
and number following subsequent confrontations (Fig. 2). Therefore, it is important
that analysis of anomalies take into consideration injuries that change over time and
could lead to misidentification and double counting of individuals. In some cases,
as we analyzed multiple photos from a single capture, Panthers initially considered
to be females were later confirmed as males by a single photo in the series that revealed
their testicles. These cases demonstrated the advantage of multiple photos
per capture for accurate gender determination.
Female Panthers did not exhibit as many body wounds as males because intraspecific
aggression is not as prevalent in females (Benson et al. 2011, Hornocker
and Negri 2009, McBride and Sensor 2014). Thus, an absence of physical differences
prevented us from recognizing uncollared females consistently and with absolute
certainty, despite thousands of opportunities to do so. In addition, a Panther family
group was not always photographed together, which made it difficult to distinguish
uncollared females with juveniles from uncollared females without juveniles. As an
example, female Panther #184 was photographed 118 times at multiple camera sites
after the birth of her kittens, of which she was alone 63 times, was photographed
with 1 kitten 11 times, with 2 kittens 23 times, and with 3 kittens 21 times. Without
a radio collar, this female could have been mistaken for a number of different
females based on different litter sizes. To overcome this problem, we used age of
kittens and distance from other litters to differentiate family groups and thereby
determine a minimum number of females present (Fig. 1).
The length of our 2-y study provided opportunities for us to observe adult
females courting males, pregnant females, and kittens when they became large
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Figure 2. A. Male Panther identified by its unique ear notch; B. Aside from wearing a radio
collar, this male Panther could also be identified by its unique ear n otch.
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enough to accompany adult females. This progression allowed us to identify
individual females and changes in kitten pelage, size, mortalities, and eventual
dispersal. We also recognized individual litters by their proximity and size (age) of
the kittens which were born months earlier or months later and could not possibly
be confused as the same litter (Fig. 1). We caution against using this technique in
short-term or intermittent camera-trap studies (Long et al. 2003, Kelly et al. 2008,
Negroes et al. 2010, Paviolo et al. 2008) due to the possibility of missing the kitten
cycle completely. Additionally, we caution against using time-delay settings of >1
second (Kelly et al. 2008, Long et al. 2003, Negroes et al. 2010) because kittens
that often follow closely behind their mother will likely be mi ssed.
Although we recognize that the absence of radio-collared Panthers in a study
area could make identification more difficult, it did not preclude accurate identification
based on anomalies and morphological characteristics. We avoided “estimates”
and “best judgments”, and in the event of questionable identifications, we chose to
err on the side of caution by placing such individuals in the u nknown category.
We feel that the design of the camera survey (i.e., cameras placed on travel
routes, high-quality digital cameras, and use of a species-specific scent lure) and
the large number of photos obtained of individuals on multiple occasions helped
us identify the gender consistently and determine a minimum population number
at our study site. Although the presence of kittens was advantageous, we conclude
that identification of females was less reliable than males. Thus, researchers
should make their own determinations regarding standards for reliability of female
identification based on their individual study goals. Finally, newer mark–resight
techniques are in development that may accommodate full or partial identification
of some population segments (McClintock and White 2009; Sollmann et al. 2013a)
or make use of ancillary data (Sollmann et al. 2013b). If these methods are proven
to be accurate, they have the potential to provide defensible Florida Panther population
numbers. Our results indicate that our method for identification of individual
adult males is reliable and can be used in such analyses.
Acknowledgments
We thank the US Fish and Wildlife Service, National Park Service, and Florida Fish and
Wildlife Conservation Commission for providing funding, equipment, and in-kind project
support. We also thank Pedro Ramos, Ron Clark, and Deborah Jansen for providing logistics,
equipment, and overall project support, and Cougar McBride of Rancher’s Supply, Inc.
for camera-site fieldwork. Special thanks to NPS staff John Kellam (NPS) for assistance
with manuscript, photographic, and figure edits. Thanks also to the Florida Fish and Wildlife
Conservation Commission and the thousands of citizens who purchased Florida Panther
Trust Fund license plates.
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