Running Head: CAMERA-TRAPS AND BOBCATS Camera-Traps and Bobcats: An Introduction to Field Camera Technology as a Tool for Wildlife Conservation Jared M. Collins - Global Field Program Miami University – Oxford, Ohio
Nov 08, 2014
Running Head: CAMERA-TRAPS AND BOBCATS
Camera-Traps and Bobcats: An Introduction to Field Camera
Technology as a Tool for Wildlife Conservation
Jared M. Collins - Global Field Program
Miami University – Oxford, Ohio
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Abstract
Modern field camera technology provides a quantitative approach to wildlife research that is
non-invasive, low in cost and labor, and effective at documenting and monitoring the presence of
cryptic wildlife. Essentially, a field camera is comprised of a point-and-shoot style digital
camera with a storage device, flash unit, trigger mechanism, and power supply, encased in a
camouflage, weatherproof shell that can be mounted to a tree. The purpose of this paper is to
introduce this technology and describe how camera-traps have been effectively utilized in the
context of wildlife conservation science. In addition, the Hoosier bobcat (Lynx rufus) is
introduced as a prime subject for camera-trap conservation in northern Indiana. Furthermore, the
author outlines an approach to research that recognizes strategic and systematic logistics specific
to the case of the Hoosier bobcat. The author concludes that a case-specific approach, in which
camera-traps are strategically placed within suspected bobcat movement corridors, may be the
most effective method to detect the presence of the bobcat in northern Indiana.
Introduction
Over the past few decades, the field camera, or camera-trap, has become increasingly popular as
a reliable and effective method to capture visual documentation of extant wildlife. In its most
basic form, a camera-trap is a digital camera equipped with motion sensor or infrared sensor
technology, enclosed in a protective camouflage casing. Photo-trapping with the use of a
camera-trap provides a quantitative approach to wildlife research that is non-invasive, low in cost
and labor and, most importantly, effective at documenting and monitoring the presence of highly
cryptic wildlife (O'Connell, Nichols, & Karanth, 2010). Consequently, conservation scientists
worldwide have begun to utilize this technology more frequently as a key tool for ecological
research and wildlife assessment initiatives (Rowcliffe & Carbone, 2008). Some of the many
important conservation science initiatives of the past that have utilized camera-traps include a
wide variety of baseline presence/absence inventories and biodiversity (i.e., species abundance
and richness) assessment surveys (Rowcliffe & Carbone, 2008). More recently, camera-traps
have been utilized by researchers to study the feeding behavior, activity patterns and population
dynamics of rare, wide-ranging, and/or reclusive species (O'Connell et al., 2010). Ultimately,
there is little doubt that the use of this technology has significantly improved our understanding
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of the complex ecological relationships and population dynamics of many rare and endangered
species.
Perhaps one of the most important applications of the camera-trap to date has been to document
the existence (and, subsequently, the abundance) of rare and elusive mammal species. Many of
these camera-trap studies have been focused on wild felid populations that are inherently
scattered and reclusive, and that inhabit environments of difficult terrain, where traditional forms
of non-invasive observation are problematic, if not impossible. In fact, a literature review by
Rowcliffe & Carbone (2008) has shown that "the single most common use of camera traps has
been to estimate the abundance of cat species, relying on individual recognition from coat
patterns". For instance, camera-traps have become instrumental in the documentation of felid
biodiversity in the inhospitable tropical environment of Borneo. In 2003, a camera-trap survey
in the thick rainforest of Gunung Mulu National Park, Sarawak, Malaysia, was responsible for
the first ever visual documentation of the Bornean bay cat (Catopuma badia), one of the world's
rarest wild felines (Dinets, 2003). In addition, a 17 month (May 2008 - October 2009) survey
conducted by Cheyne & Macdonald (2011) further utilized camera-traps to document the
remaining four of Borneo's five wild felid species, including the Sunda clouded leopard (Neofelis
diardi), the leopard cat (Prionailurus bengalensis), the flat-headed cat (Prionailurus planiceps),
and the marbled cat (Pardofelis marmorata). Elsewhere across the globe, camera-trap
technology and photo-trapping has been equally instrumental in detecting and/or monitoring rare
wild cat populations. For instance, since 2010, camera-traps have been used effectively to
document and monitor rare felids such as the Andean cat (Leopardus jacobita) in the west-
central highlands of South America (Reppucci, Gardner, & Lucherini, 2011), the African golden
cat (Profelis aurata) in the tropical lowlands of central and west Africa (Aronsen, 2010), and the
Iberian lynx (Lynx pardinus) of Spanish Europe (Garrote et al., 2012; Gil-Sanchez et al., 2011).
Also, camera-trap technology has played an important role in establishing the northernmost
extent of the North American range of the jaguar (Panthera onca) and the jaguarundi (Puma
yagouaroundi) in north and central Mexico, respectively (Gutierrez-Gonzalez et al., 2012;
Monterrubio Rico et al., 2012). This plenitude of evidence suggests that camera-trap technology
has become an increasingly important tool for researchers seeking to gain insight on the secret
life of wild felines. Therefore, the goal of this paper is to further examine field camera
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technology as a wildlife conservation tool, and determine how this technology might be used
effectively to detect and/or monitor the presence of the bobcat (Lynx rufus) in northern Indiana.
What is a camera-trap, and how does it work?
Camera-traps are fixed, remotely activated, digital cameras that utilize motion or heat detection
technology to capture images of passing wildlife. Essentially, each field camera is comprised of
a point-and-shoot style digital camera with a storage device (e.g., memory card), flash unit,
trigger mechanism, and power supply all encased in a protective, weatherproof shell that can be
mounted to a tree or post. Camera-traps are designed to imprint the date and time on each digital
image, and many cam-traps are equipped to take both still photographs and short video clips.
The captured footage is automatically written to an SD card where images are stored until they
can be transferred to a tablet or PC. The image storage capacity of most current cam-trap models
can be quite enormous depending on the size of memory card used (e.g., most models support up
to 32GB). Camera traps are triggered by the motion and/or heat of wildlife that comes within a
certain distance (i.e., typically 40-60 ft.) of the trap sensor, and the sensitivity of the trigger can
be adjusted to optimize use according to time of day and time of year (TrailCamPro, 2012).
Furthermore, as a result of improved battery life technology, many current cam-trap models are
capable of remaining operational for up to a year or more on one set of batteries (i.e., typically 8
AA) (TrailCamPro, 2012). Currently, camera-traps are readily available and relatively
affordable, and Amazon.com features a wide variety of Bushnell and Moultrie field cameras at a
range in price from just under $150 per unit, to over $400.
Field cameras are necessarily equipped with either an incandescent or an infrared flash device.
The difference between infrared and incandescent cameras is that the former uses infrared light
to take pictures, and this infrared flash is invisible to passing wildlife (TrailCamPro, 2012).
Most infrared camera-traps also allow for video recording at night, which is another advantage of
the infrared flash device. However, color pictures can be taken only during daylight hours, and
all night-time pictures are monochromatic contrasts (TrailCamPro, 2012). Alternatively,
incandescent cameras allow for stunning full color visuals even in the pitch-dark of the night.
The term "incandescent" refers to the traditional flash bulb device that flashes a bright light to
capture images in full color with clarity and brightness. The primary disadvantage to this
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approach is that an incandescent flash is extremely bright, which has the potential to frighten
passing animals and discourage resident wildlife from entering the observation zone
(TrailCamPro, 2012).
How can a camera-trap be used as a tool of conservation?
The observation and documentation of wildlife distribution and movement patterns is of critical
importance as a source of baseline data for a wide array of conservation initiatives (Kays et al.,
2011), and research from Gibbs (2000) has demonstrated that "population monitoring" plays a
crucial role in ecological studies and wildlife conservation initiatives (as cited in Heilbrun, 2006,
p. 69). Thus, it is not at all surprising that the camera-trap, a device specifically designed to
detect and document, has become such an important tool in the world of conservation science.
Kays et al., 2011 describe the camera-trap as a "visual sensor to record the presence of a broad
range of species providing location-specific information on movement and behavior". As a
"visual sensor" of wildlife, the camera-trap offers researchers the perfect Eulerian approach to
tracking the movement of wildlife, in which a specific location is monitored to capture the
movement of all the wildlife that passes by (Kays et al., 2011). In contrast, the Lagrangian
approach to tracking wildlife movement exists as a more labor intensive (and potentially
dangerous) approach that requires the temporary capture of individual animals for the purpose of
tagging or implanting a radio-telemetry monitoring device (Kays et al., 2011). Consequently,
cam-traps are often championed as an effective and non-invasive biodiversity assessment tool,
and this location-specific solution has quickly become a popular approach to document species
richness and abundance worldwide.
A detailed literature review covering the combined topics of "camera-traps" and "conservation
science" revealed that, over the past decade, wildlife research featuring the use of camera-traps
has primarily focused on baseline systematic assessments such as species richness surveys,
relative abundance studies and other biodiversity-related objectives. For example, rapid species
richness surveys in Malaysia and Lebanon have successfully utilized camera-trap technology to
document the cryptic wildlife of two ecologically distinct habitats. A rapid assessment survey
conducted by Mohd. Azlan & Lading (2006) in the tropical forest environment of Sarawak,
Malaysia, utilized camera-trap technology to capture visual documentation of several rare and
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elusive mammals (i.e., the binturong Arctictis binturong, the bearded pig Sus barbatus, the
Sunda clouded leopard Neofelis diardi) currently listed as Vulnerable by the International Union
for the Conservation of Nature (IUCN, 2012). Likewise, a rapid assessment survey conducted
by Abi-Said & Amr (2012) in the subtropical scrubland environment of Jabal Moussa, Lebanon
also utilized camera-trap technology to capture visual documentation of several rare and elusive
mammals, in this case revealing the southernmost extent of the range of the least weasel
(Mustela nivalis) and the Eurasian badger (Meles meles). Furthermore, camera-traps have also
been instrumental in aiding the analysis of the relative abundance and density of shy, rare and
elusive wildlife populations. For instance, a rapid abundance assessment of carnivores
conducted by Gerber et al. (2010) in the rainforest environment of eastern Madagascar utilized
camera-traps to gather, for the first time, valuable baseline data regarding the abundance and
density of the fossa (Cryptoprocta ferox) in the eastern part of its range. Consequently, their
research discovered that fossa abundance and density may be much lower in the wet forests of
the eastern half of the island, when compared to that of conspecific populations in the western
dry forests (Gerber et al., 2010). Ultimately, each of the studies outlined above have utilized
camera-trap technology to gather important bits of baseline data that will allow for more
complex ecological studies to be undertaken in the future.
Why the bobcat?: Lynx rufus in Indiana
So then, why the bobcat? What is the point of studying a wild cat population that is officially
listed by the IUCN (2013) as a species of Least Concern? Lynx rufus has a long history in
Indiana as a beneficial predator and generalist carnivore. Bobcats are entirely carnivorous, and
while they prefer to prey on rabbits, they also feed on rats, mice, moles and squirrels, as well as
woodchucks, raccoons, feral cats and even deer (Kelly et al., 2008; Whitaker & Mumford, 2009).
Bobcats have been needlessly destroyed due to the misconception that they are vicious predators,
while, in fact, they are a beneficial carnivore, effective at controlling rodent populations and
culling sick or injured deer and mesopredators (i.e., raccoons, feral cats, etc.).
The bobcat once ranged widely across the state of Indiana, however, residential and agricultural
pressures from an expanding human population have resulted in widespread deforestation and
the associated loss and fragmentation of bobcat habitat. Consequently, this loss of habitat,
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coupled with detrimental effects of trapping, sport hunting and predator control initiatives, has
resulted in a severe decline of the bobcat population in Indiana over the past century (Whitaker
& Mumford, 2009). By 1970 it became necessary to place the bobcat on the state endangered
species list and, over a decade later, a survey by Mumford & Whitaker (1982) revealed that the
"bobcat was quite rare in Indiana" (as cited in Whitaker & Mumford, 2009, p. 601). Yet, by
2005, the Hoosier bobcat population had recovered sufficiently enough in the forested hills of
southern Indiana to warrant its removal from the state endangered list. However, the reality of
extreme landscape fragmentation in northern Indiana, and the associated lack of quality bobcat
habitat, has resulted in what is essentially a bobcat-free zone across the northern half of the state
(Whitaker & Mumford, 2009). Yet, in spite of this extremely fragmented and unfavorable
environment, the bobcat's presence has been confirmed in northern Indiana on 6 occasions
(representing six individuals) since 1993 (Whitaker & Mumford, 2009). The first two
confirmations occurred in 1993 in the extreme northeastern corner of Indiana (i.e., Dekalb and
Steuben counties) (Whitaker & Mumford, 2009). The Dekalb confirmation is of particular
importance as the first confirmed report of Lynx rufus in northern Indiana since 1970. A third
confirmed report from northeastern Indiana was documented at the Pigeon River Fish and
Wildlife Area in Lagrange County in 1998 (Whitaker & Mumford, 2009). The other three
confirmed reports come from the heart of the Wabash/Tippecanoe watershed in north-central
Indiana; Fulton County (1996), Cass County (1997), and Carroll County (1999) (See Appendix I,
Map 1) (Whitaker & Mumford, 2009). In addition, many unconfirmed reports also exist,
including a 2001 sighting witnessed by the author near Goshen, Indiana (Elkhart County).
Ultimately, the singular situation of the bobcat in northern Indiana presents the perfect
opportunity to utilize camera-traps as an approach to survey an elusive and locally rare mammal.
Discussion
The preceding three sections of this paper were intended to introduce field camera technology,
describe how this technology has been utilized in the context of conservation science, and
introduce the Hoosier bobcat as a prime subject for camera-trap conservation. This final section
is intended to illustrate how field camera technology might be used effectively to detect and
monitor the presence of the bobcat in northern Indiana.
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Questions about Lynx rufus that might be answered with the help of camera-traps include: Are
bobcats in northern Indiana part of a local population, or are they transients moving between
larger populations in Michigan and Kentucky? Or, how might the fragmented agricultural
landscape of northern Indiana effectively limit the movement and interaction of the bobcat
metapopulation? As a norm, wildlife researchers look to use a variety of productive means to
estimate the distribution and abundance of a species of interest, generally utilizing both Eulerian
(location-specific) and Lagrangian (host-specific) technology. However, most host-specific
technologies (i.e., tags, collars, implants, etc.) are labor intensive, and they can be quite difficult
(and even dangerous) to use when monitoring wild carnivores that are rare, elusive or nocturnal,
not to mention unpredictable and aggressive (e.g., many wild felids). In the case of the Hoosier
bobcat, wildlife researcher Scott Johnson of the Indiana Department of Natural Resources
(IDNR) successfully utilized a Lagrangian approach (i.e., fitted radio collars) to monitor 38
individual bobcats in southern Indiana (Whitaker & Mumford, 2009). From December 1998 to
April 2005, Johnson carefully documented the distribution, density and habitat preferences of a
relict population of bobcat in south-central Indiana. By tracking, trapping and the fitting
bobcats with radio collars, Johnson gathered valuable data that would eventually be instrumental
in the development of a bobcat habitat management plan. Johnson's work revealed that while,
the bobcat of southern Indiana prefers to inhabit remote wooded areas, it is not averse to moving
about a fragmented landscape if it can find temporary refuge in swamps and wooded
bottomlands (Whitaker & Mumford, 2009). In 2005, Johnson's long-term management and
research program began to show results as the bobcat was officially removed from Indiana's
endangered species list and reclassified as a Species of Special Concern (Whitaker & Mumford,
2009).
While the future of the bobcat in southern Indiana seems very promising, the status of the bobcat
north of Indianapolis is a big question mark. Perhaps a strategic and systematic camera-trap
survey could shed some light how the bobcat uses the fragmented agricultural landscape of
northern Indiana. One important strategic aspect of this study should logically concern the
current distribution of the bobcat in northern Indiana (i.e., as reported by Whitaker & Mumford,
2009), and how this information might be used to augment decisions concerning cam-trap
placement at a state-wide level. For instance, a comparative examination of a map of this simple
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distribution superimposed over a map of Indiana's major watersheds suggests that Lynx rufus
could be using the remnant gallery forests of these drainage basins to actively penetrate the
northern half of the state (See Appendix I, Maps 2 & 3). Therefore, placing camera-traps
strategically within an inferred range based on a combination of extant location data and
educated reasoning may allow for the most efficient use of limited resources. One important
systematic aspect of this bobcat camera-trap study would naturally concern the most effective
design of research methodology to properly suit the specific case of Lynx rufus. For instance, as
a crepuscular carnivore, Lynx rufus is shy and elusive, and most active after dusk, making it a
difficult species to observe in the wild. However, a study by Heilbrun et al. (2003) revealed that
bobcat individuals can be accurately identified on a consistent basis by the unique markings of
their pelage, and thus, capture-mark-recapture population studies can be effectively conducted by
camera-trap alone. Furthermore, the collective experience of researchers worldwide has shown
that the unique color and spot patterns of wild felids can be best recognized in full color images.
Therefore, a logical approach to photo-trapping the bobcat might consider a rotation of both
incandescent and infrared field cameras, thereby providing a supply of full color, nighttime
photographs for comparative purposes, while also limiting the spooking potential of incandescent
cameras alone.
Conclusion
The observation and documentation of wildlife distribution and movement patterns is of critical
importance as a source of baseline ecological information (Kays et al., 2011). Hence, it is not at
all surprising that the camera-trap, a device specifically designed to detect and document, has
become such an important tool in the world of conservation science. Many researchers have now
adopted the use of camera-trap technology as an Eulerian (location-specific) approach to meet
wildlife observation and population assessment objectives (Kays et al., 2011). Furthermore, a
plenitude of published literature suggests that camera-trap technology has been of exceptional
importance in the context of wild felid population monitoring initiatives. However, field camera
technology has yet to be utilized in the case of the Hoosier bobcat and the status of this cryptic
carnivore remains a mystery in the northern half of Indiana. Yet, perhaps a properly funded,
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state-wide cam-trap investigation of bobcat movement could yield the load of data necessary to
properly distinguish zones of bobcat residency from zones of bobcat transience.
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Appendix I
Map 1: The 92 counties of Indiana.
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Map 2: Major Indiana Watersheds - The greater Wabash watershed includes the Wabash River (10) and eight
smaller tributaries: Raccoon Creek (16), Sugar Creek (15), Wildcat River (11), Deer Creek (12), Mississinewa River
(13), Salamonie River (14), Eel River (31), and Tippecanoe River (6) (Whitaker & Mumford, 2009).
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Map 3: Confirmed reports of Lynx rufus in Indiana from 1970-2001 (42 reports from 25 counties).
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Appendix II
Image 1: Incandescent field camera used by the author to take the following pictures
Image 2: Resident wildlife of Norton Lake, Indiana - Northern Raccoon (Procyon lotor)
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Image 3: Resident wildlife of Norton Lake, Indiana - Virginia opossum (Didelphis virginiana)
Image 4: Resident wildlife of Norton Lake Indiana - Raccoon and Opossum
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Image 5: Resident wildlife of Norton Lake Indiana - White-tailed Deer (Odocoileus virginianus)