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Efficacy of Trail Cameras to Identify Individual Florida Panthers
Roy McBride and Rebecca Sensor

Southeastern Naturalist, Volume 14, Issue 2 (2015): 351–360

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Southeastern Naturalist 351 R. McBride and R. Sensor 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 Southeastern Naturalist R. McBride and R. Sensor 2015 Vol. 14, No. 2 352 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 Southeastern Naturalist 353 R. McBride and R. Sensor 2015 Vol. 14, No. 2 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 Southeastern Naturalist R. McBride and R. Sensor 2015 Vol. 14, No. 2 354 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). Southeastern Naturalist 355 R. McBride and R. Sensor 2015 Vol. 14, No. 2 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 Southeastern Naturalist R. McBride and R. Sensor 2015 Vol. 14, No. 2 356 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 Southeastern Naturalist 357 R. McBride and R. Sensor 2015 Vol. 14, No. 2 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. Southeastern Naturalist R. McBride and R. Sensor 2015 Vol. 14, No. 2 358 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. 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