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Advancing Primate Research
and Conservation Through the Use of Camera
Traps: Introduction to the Special Issue
Paula A. Pebsworth &Marni LaFleur
#Springer Science+Business Media New York 2014
Abstract Effective conservation and management of primates depend on our ability to
accurately assess and monitor populations through research. Camera traps are proving
to be useful tools for studying a variety of primate species, in diverse and often difficult
habitats. Here, we discuss the use of camera traps in primatology to survey rare species,
assess populations, and record behavior. We also discuss methodological considerations
for primate studies, including camera trap research design, inherent biases, and some
limitations of camera traps. We encourage other primatologists to use transparent and
standardized methods, and when appropriate to consider using occupancy framework
to account for imperfect detection, and complementary techniques, e.g., transect counts,
interviews, behavioral observation, to ensure accuracy of data interpretation. In addi-
tion, we address the conservation implications of camera trapping, such as using data to
inform industry, garner public support, and contributing photos to large-scale habitat
monitoring projects. Camera trap studies such as these are sure to advance research and
conservation of primate species. Finally, we provide commentary on the ethical
considerations, e.g., photographs of humans and illegal activity, of using camera traps
in primate research. We believe ethical considerations will be particularly important in
future primate studies, although this topic has not previously been addressed for camera
trap use in primatology or any wildlife species.
Keywords Cameratrap.Conservationethics .Methods.Primat es.Remote photography
Int J Primatol
P. A. Pebsworth
Department of Anthropology, University of Texas, San Antonio, TX 78666, USA
P. A. Pebsworth
Department of Soil Science, Stellenbosch University, Stellenbosch, South Africa
M. LaFleur (*)
Institute for Population Genetics, University of Veterinary Medicine, 1220 Vienna, Austria
At the XXIVth International Primatological Congress in Cancun, Mexico, a sympo-
sium entitled “Advancing Primate Research and Conservation through the Use of
Camera Traps”brought primatologists together to discuss how camera trapping facil-
itates the study, management, and conservation of nonhuman primates. The symposium
organizers (Marni LaFleur and Chia L. Tan) gathered information on the current state of
camera trap applications in primate research and promoted the standardization of
qualitative and quantitative methods. This forum provided camera trap users and
would-be users the opportunity to discuss relevant topics, such as selecting the best
hardware and accessories for one’s project needs and budget, overcoming technical and
methodological difficulties, and making reliable inferences from camera trap data. This
special issue highlights some of the camera trap research presented at the IPS sympo-
sium in Cancun, and also addresses some of the discussion points that followed, e.g.,
data interpretation and standardized methods.
In this special issue editorial, we review a variety of camera trap applications that
have been used in primatology: surveying rare species, assessing primate populations,
and recording behavior. Next, we provide primatologists with methodological consid-
erations for their camera trap studies. We then discuss how camera traps can be used to
determine the conservation status of primate species and as a means promoting and
protect primates. Finally, we address some of the ethical concerns that may arise when
using camera traps in primate research, such as recording illegal activity and
(potentially) protecting human anonymity. Surprisingly, given the extent of human–
wildlife conflict on the global scale, ethical considerations and camera trap use are not
discussed in any wildlife research that we are aware, but could be particularly important
in cases of animal poaching and trafficking. We base our editorial on the information
presented at the IPS symposium, the articles within the special issue, and the literature
to date on camera trap use in primatology.
Camera Trap Applications
Surveying Rare Species
Natural resource, e.g., water, land, plants, management decisions are heavily influenced
by the abundance and distribution of rare species (Thompson 2004). Unfortunately, by
their very nature, rare species are a challenge to study because their populations may be
clumped or sparsely distributed over a large range, and/or their behavior may be elusive
(Thompson 2004). Rare species may also reside in remote areas where field conditions
are difficult and traditional survey methods, e.g., direct observation, capture/recapture,
are likely to be ineffective or impractical (Kierulff et al.2004;Tanet al.2013). In these
instances, camera traps have proved to be an effective tool for surveying primates,
without the need to observe the individuals directly or physically trap them (Fig. 1).
Camera traps can record presence/absence of a rare or elusive species (Bezerra et al.
2014;Gerberet al.2014), establish habitat requirements (Head et al.2012;Numata
et al.2005), and document geographical range (Easton et al.2011). To optimize the
likelihood of capturing the focal subject, researchers have used lures (Bezerra et al.
P.A. Pebsworth, M. LaFleur
2014;Kierulffet al.2004), strategically placed camera traps near critical resources,
such as natural canopy bridges (Gregory et al.2013), bamboo zones (Easton et al.
2011), and natural licks (Lhota et al.2012). Additional methods of careful and targeted
placement are described by Loken et al.(2013), Olson et al.(2012), and Tan et al.
Assessing Primate Populations
Primates are among the most threatened taxa, with almost half of the world’sprimate
species in danger of extinction from habitat destruction, illegal wildlife trade, and
commercial bushmeat hunting (Mittermeier et al.2009). Primatologists need to monitor
endangered populations, so that they can inform the public of a population’s plight,
encourage governments to conserve these species, and raise the necessary funds to
introduce and implement critical conservation measures. Camera traps offer the possi-
bility of continually monitoring a population indefinitely (or nearly indefinitely) and
Fig. 1 (a) A very rare photo of a silky sifaka (Propithecus candidus) on the ground at the Anjanaharibe forest
site in the Makira Natural Park, Madagascar. (b) An aye-aye (Daubentonia madagascariensis) at the
Farankarina protected area near Masoala National Park, Madagascar. (Photos by Zach J. Farris.).
Use of Camera Traps: Introduction
can be used to assess primate demographic patterns (Fig. 2). For example, long-term
camera trap projects can reconstruct group composition, including births, disappear-
ances, and interbirth intervals (Galvis et al.2014). In addition to demographic patterns,
camera traps can be used to record specific primate behaviors, which are addressed
Recording Primate Behavior
Focal animal follows provide a wealth of data and information, as they document all
behaviors of interest and primates’use of various resources (Altmann 1974). However,
following animals in this way requires habituation, which is not always feasible or
advisable (Jack et al.2008; Souza-Alves and Ferrari 2010), as doing so may be
detrimental to their health and wellbeing (Bezerra et al.2014; Boyer-Ontl and Pruetz
2014;Butynski2001; Williamson and Feistner 2003,2011). Camera traps may provide
a viable data collection alternative, in situations where animal follows and habituation
Fig. 2 (a) Ring-tailed lemurs (Lemur catta) with an infant at the Tsimanampetsotse National Park, Mada-
gascar. (Photo by Marni LaFleur.) (b) Chacma baboons (Papio cynocephalus ursinus)congregatetodrink
water and eat soil at the Wildcliff Nature Reserve, South Africa. (Photo by Paula Pebsworth.).
P.A. Pebsworth, M. LaFleur
are not advisable. Primate studies have capitalized on camera traps’ability to monitor
fixed locations where a specific behavior or resource use occurs, as well as interactions
among and between species, as addressed in more detail next.
One of the first camera trap applications for recording behavior was geophagy, i.e.,
the deliberate consumption of earth materials (Fig. 3). Camera trap studies have
documented which species frequent geophagy sites (Link et al.2011;Matsubayashi
et al.2007), patterns of consumption (Galvis et al.2014;Pebsworthet al.2012), and
possible seasonal effects of geophagy (Blake et al.2010). Because geophagy sites are
important contributors to a primate’s overall health and they can be monitored with
relative ease, these sites should be considered conservation priorities and target areas
for gathering camera trap data (Matsubayashi et al.2007; Pebsworth et al.2012).
Other primate resources, such as foods, can also be monitored using camera traps.
Studies focusing on the consumption of masting fruit resources (Miura et al.1997;
Prasad et al.2010), seed dispersal (Miura et al.1997), and of primates dropping or
knocking off fruits that terrestrial animals then eat (Prasad et al.2010), have informed
Fig. 3 (a) Diademed sifaka (Propithecus diadema) at a geophagy site in the Maromizaha Forest, Madagascar.
(Photo from San Diego Zoo Global/University of Turin/GERP.) (b) Adult female chacma baboon (Papio
cynocephalus ursinus) eating soil at the Wildcliff Nature Reserve, South Africa. (Photo by Paula Pebsworth.).
Use of Camera Traps: Introduction
researchers on how primates contribute to forest ecology. Moreover, video camera
trapping showed that seasonal fruit abundance may influence interspecific competition
between common chimpanzees (Pan troglodytes troglodytes), gorillas (Gorilla gorilla
gorilla), and forest elephants (Loxodonta cyclotis)(Headet al.2012). Camera trap
research on habitat use patterns by sympatric chimpanzees and gorillas reflect the
species’dietary preferences, in that chimpanzees are frugivorous and prefer montane
forests and gorillas are folivores and are distributed across habitat types (Nakashima
Unlike primate resources, predation events and predators are notoriously diffi-
cult to monitor. However, if you are extremely lucky, camera traps can be useful in
documenting predation events (Fig. 4). Moreover, owing to the relative length of
time camera traps are deployed, when compared with the amount of time one can
spend observing, and the fact that observer presence can influence predator
behavior, camera traps are also useful for detecting predators (Fig. 5) and under-
standing how primates react to their presence. Predator avoidance strategies have
been detected via camera trap photos in white-bellied spider monkeys (Ateles
belzebuth)andredhowlers(Alouatta seniculus)(Blakeet al.2010;Linket al.
2011), and the authors suggest that these primates are more likely to use geophagy
sites when they know where their predators are, even if the predators are
nearby. Simlairly, ring-tailed lemurs (Lemur catta) stay in trees for longer
periods when their largest aerial predators, Madagascar harrier hawks
(Polyboroides radiata), are also present in the trees (LaFleur unpubl. data).
This is likely because the hawks have large wingspans and cannot attack
between branches (LaFleur unpubl. data).
Camera traps can also be used to assess other forms of behavioral plasticity.
Loken et al.(2013) used camera traps to assess whether canopy connectivity
influences terrestrial behavior in orangutans (Pongo pygmaeus morio), a predom-
inately arboreal primate. This species of orangutan is native to Borneo, where
habitat destruction and fragmentation have altered primate habitat (van Schaik
et al.2009). Camera traps documented that terrestriality is common in this
population of orangutans and represents a locomotion strategy to overcome loss
of canopy connectivity. Further, these results suggest orangutans may have more
ecological flexibility than once thought.
Camera trap studies have shown that activity patterns vary more than traditional
views, in such species as ring-tailed lemurs (Lemur catta:LaFleuret al.2014), gray
snub-nosed monkeys (Rhinopithecus brelichi:Tanet al.2013), and savannah chim-
panzees (Pan troglodytes versus: Boyer-Ontl and Pruetz 2014)(Fig.6). Each of these
primates has been traditionally classified as diurnal (Kirk and Kay 2004;cf.Donati
et al.2013 and Traina 2001 for Lemur catta). Nighttime activity in these primates has
been attributed to avoiding extremely high daytime temperatures (Boyer-Ontl and
Pruetz 2014) and exploiting ephemeral resources (LaFleur et al.2014;Tanet al.
2013). Moreover, some of the nocturnal behaviors documented by camera traps have
been novel, such as cave use and pool soaking by unhabituated groups of Pan
troglodytes verus (Pruetz 2007). Such unexpected animal activity may have important
implications for our understanding of species ecology, including activity budget, food
intake, and predator avoidance, and highlights the behavioral flexibility of these
P.A. Pebsworth, M. LaFleur
Many different camera traps are available, and a researcher’s site, objectives, and
budget determine which camera is most appropriate. Camera trap technology is
changing rapidly, so we do not discuss specific makes or models but offer some
considerations for selecting a remotely triggered camera and how to determine whether
it will be appropriate for a research site and objectives.
Flash Type and Intensity
Camera traps with infrared flash take color daytime and monochromatic nighttime
photos, while camera traps with white flash take color photos regardless of light levels.
Nighttime color photographs can be critical for conducting a faunal inventory and
studies requiring individual recognition, but white flash may frighten target subjects
Fig. 4 (a) Madagasc ar’s largest terrestrial predator, the fossa (Crypropracta ferox), entering the nest of the
largest aerial predator, the Madagascar harrier hawk (Polyboroides radiata). (b) Six minutes later the fossa
leaves with a hawk in its mouth. (Photos taken at the Tsimanampetsotse National Park, Madagascar by Marni
Use of Camera Traps: Introduction
and alter detection probabilities. In addition to flash type, researchers studying noctur-
nal primates may want to consider whether the camera automatically adjusts flash
intensity based on the distance to the primate. This feature maximizes the probability of
detecting primates while minimizing visible or audible cues that potentially alter
Trigger Speed and Sensitivity
How much time passes between camera activation and when a photograph is taken is
critical to many studies. Most cameras employ a passive infrared sensor that activates at
some time after it detects a difference in heat motion between the fore- and background
temperature. Cameras with a short trigger delay (<1 s) are ideal for capturing relatively
fast-moving, small, or solitary primates, whereas a longer trigger delay (>1 s) may be
better for slow-moving, large, or group-living primates. False negative images, i.e., a
Fig. 5 (a) A Cape leopard (Panthera pardus) which shares its range with chacma baboons (Papio
cynocephalus ursinus), and (b) a Madagascar harrier hawk (Polyboroides radiata), which shares its range
with ring-tailed lemurs (Lemur catta). (Photos taken at Wildcliff Nature Reserve, South Africa by Paula
Pebsworth and Tsimamampetsotse National Park, Madagascar by Marni LaFleur.).
P.A. Pebsworth, M. LaFleur
primate triggered the sensor but moved out of the frame before the photograph was
taken, result from a trigger speed that is too slow, but cameras with fast trigger speed
are often more expensive.
The sensitivity, or the camera’s ability to detect heat motion, decreases when
ambient temperature is low, or when the difference between ambient temperature and
the subject’s body temperature is small (i.e., <2.7°C) (Meek 2012). Decreased sensi-
tivity can result in failure to trigger the camera trap. Alternatively, in very hot
environments the camera can be highly sensitive and triggered more easily by nontarget
movements, e.g., wind or moving vegetation (Gregory et al.2013;Roveroet al.2013).
Sensitivity can be adjusted on most cameras.
Detection area varies between camera models and is an important determinant in the
number of photos taken. Some cameras use a conical detection zone, while others use
Fig. 6 (a) Ring-tailed lemur (Lemur catta) nighttime activity at the Tsimanampetsotse National Park,
Madagascar. (Photo by Marni LaFleur.) (b) Senegalese chimpanzee (Pan troglodytes versus) nighttime
activity. (Photo by Kelly Boyer Ontl.).
Use of Camera Traps: Introduction
horizontal bands and vertical axis zones (Rovero et al.2013). Obviously, a larger
detection zone allows a larger area to be monitored. The detection zones of some
cameras are wider than their field of view, which can be useful in capturing fast-moving
primates. However, wide detection zones may produce a surplus of blank photographs
taken when primates enter the camera’s detection zone but not the field of view.
Cameras with narrower detection zones produce fewer blank photographs but may
also fail to detect primates that move quickly or are not well centered in front of the
Most camera traps are digital and require secure digital memory cards. Larger card
sizes, e.g., 4–32 GB, allow for longer deployment time, a large number of photographs,
or video recording.
Camera traps are expensive and may be difficult to replace once in the field. To
prevent or discourage theft, they can be attached to trees or other substrates
with security cables. Cameras can also be housed in external metal security
boxes, which have the extra protection of being tamper-proof and can also be
locked and securely attached.
Effects of Climate
Moisture and extreme temperatures affect image quality and power. Researchers
combat high humidity and precipitation by placing an internal desiccant inside the
camera housing to prolong dry conditions (Blake et al.2010;Miuraet al.1997). In
addition, covering the camera in a thin transparent polyethylene bag or wrap can act as
a barrier to moisture and debris (Numata et al.2005). Intense sunlight can also impact
camera performance, as it degrades plastic lenses.
In addition to image quality, camera trap performance declines with extreme tem-
peratures, e.g., <0°C and >30°C. In very cold temperatures, alkaline batteries quickly
discharge, so lithium or nickel metal hydride (NiMH) rechargeable batteries are the best
option. NiMH rechargeable batteries fail sooner in hot weather (when temperatures
exceed 32°C), and alkaline and lithium batteries are preferable.
Small portable solar panels with built-in lithium polymer batteries are also available
for camera traps. These are safe for use in extreme temperatures and are automatically
chosen as the main power source for the cameras, although we recommend internal
batteries as backup to solar power.
Trap Days and Camera Placement
Camera trap days are the number of 24-h periods that cameras are employed, multiplied
by the number of cameras in operation (Blake et al.2010; Rovero et al.2013). The
research goals determine the number of camera trap days necessary for data collection.
For example, LaFleur et al.(2014) determined in less than a month that Lemur catta
P.A. Pebsworth, M. LaFleur
frequently engaged in nighttime activity. However, rare behaviors or infrequently
seen species will likely require extended periods of monitoring. In species inven-
tory studies, an accumulation curve can be used to assess if the duration of
sampling has sufficiently captured species present (Tobler et al.2008). In this
case, time needed to carry out a survey is inversely proportional to the number of
camera traps used. The more camera traps used, the more quickly the accumula-
tion curve will level off. However, the distance between cameras may be impor-
tant, as cameras that are placed nearby one another may not produce photographs
that are independent events. This also applies to the time lag between photo-
graphs. Researchers must think carefully about how and why they consider
photographs independent, as this will influence the results (LaFleur et al.2014;
Tan et al.2013).
Camera traps can be placed strategically or systematically. Systematic placement
involves determining set intervals for cameras. In this case, camera placement may be
based on a grid (Gerber et al.2012;Headet al.2012), in convenient areas such as on
trails (Farris et al.2014;Headet al.2012), or randomly (Nakashima et al.2013).
Random sampling aims to meet certain statistical requirements, to achieve independent
sampling (Nakashima et al.2013).
All sampling methods have biases, and camera traps are no exception. Images
captured can be biased by species-specific characteristics, as camera trap detec-
tion is higher in gregarious species that forage and travel together than solitary
individuals (Treves et al.2010) and they are also more effective at detecting
smaller, solitary, and nocturnal species than wildlife patrol units (Burton 2012).
Population assessments using camera traps can also be affected by anthropo-
genic disturbances and human presence. For example, Gray and Phan (2011)
reported that camera trap detection was lower in areas within a day’swalkfrom
human settlement and that even after 750 nights of surveys, camera traps failed
to capture all species known to exist within the Phnom Prich Wildlife
Correcting Camera Trap Biases
When possible, researchers should compare sampling methods to determine
whether their data are biased. Ideally, biased camera trap data should be
corrected or offset by using an occupancy framework (Gerber et al.2014),
and/or combining camera trap surveys with complementary methods. Many
established methods have been used in combination with camera trap surveys
to improve data reliability, e.g., direct observation and spot counts (Galvis et al.
2014;Pickleset al.2011; and line transects, Farris et al.2014), although other
methods also have inherent biases such as variation in detection, small sample
size, and low precision (Gerber et al.2014). When camera traps and direct
observation fails to establish species presence, indirect observation (spoor, feces,
nest, carcasses) can be employed (Nakashima et al.2013;RossandReeve2003;
Stevens et al.2011).
Use of Camera Traps: Introduction
Implications for Primate Conservation
Primatologists are concerned with the survival of their research taxa (Setchell 2013).
Baseline analyses and environmental monitoring are essential components of conser-
vation management, and camera traps are effective tools both alongside and apart from
traditional habitat and animal monitoring programs (Ahumada et al.2013;Galviset al.
2014). For example, camera trap monitoring and surveillance of Peruvian primates
showed that trap success and encounter rates dramatically decreased immediately after
land clearance and gas pipeline installation; however, animals resumed use of land
bridges after construction (Gregory et al.2013). These data were used to inform gas
and oil developers, who continued to maintain corridors when clearing forested areas
(Gregory et al.2013). Another camera trap study documented Gorilla gorilla diehli for
the first time in Cameroon’s Kagwene Gorilla Sanctuary (Wildlife Conservation
Society, 2012). This elusive species has rarely been viewed directly, and researchers
and conservation organizations discourage habituation because of potential hunting
pressures. The Wildlife Conservation Society used these data as part of community and
public awareness campaigns, and footage served to inspire local people, governments,
and the global community to protect and conserve this Critically Endangered great ape.
Data such as these can enable conservation planners to assess and progress toward
conservation goals and to target and design interventions (Gregory et al.2013;O’Brien
et al.2010; Wegge et al.2004).
The largest globally coordinated camera trap monitoring project, Tropical Ecological
Assessment & Monitoring Network (TEAM), also provides opportunities for primate
conservation planning through camera trap data (www.teamnetwork.org). TEAM
report activities of terrestrial vertebrates and currently monitor 16 tropical forest sites
across Africa, Asia, and Latin America. Camera trap data are collected according to
strict protocols, and all researchers can access the data via an online database.
Primatologists can also contribute data to this project but must adhere to guidelines
including the use of a minimum of 60 camera traps per project. More information on
TEAM can be found on their website (www.teamnetwork.org).
Field primatologists face a complex array of issues related to primate subjects, which
often stem from the competing need for resources by wild primates and humans, and/or
the management of habitat by local governments or officials (Wolfe 2005). Several
excellent publications have resulted from the recent initiative to highlight the ethical
dilemmas faced by field primatologists (Fedigan 2010; MacKinnon and Riley 2010;
Malone et al.2010), but the use of camera traps has not been addressed directly. In fact,
to our knowledge, ethical concerns of camera trapping have not been addressed in the
Some of the ethical considerations of using camera traps are the same as those
encountered by conducting fieldwork in general, such as potentially witnessing illegal
activity, while others are unique to camera traps, including what constitutes informed
consent by humans that are photographed. Inevitably, whether intentional or not,
researchers employing camera traps will capture photographs of humans. We thus need
P.A. Pebsworth, M. LaFleur
to determine under what circumstances, if any, these photos are used. Human activities
could, of course, be the focus of our research, as we may want to document human
presence or human impact on nonhuman primate habitats. In these instances, permis-
sion from the researcher’s Institutional Review Board (IRB) or similar for human
subjects is likely to be necessary. However, if photographs of people are merely a
“by-product”of data collection, what should we do with these unintended data, and
should we still seek IRB approval?
Ethnographers generally provide copies of data to all informants and go to great
lengths to protect informant identity (Murchison 2010). Should we adopt similar
policies? One could imagine providing photos to each person captured by cameras
quickly becoming unmanageable. Alternatively, it may be more suitable to provide
information, rather than actual photographs, to local people with reference to the
location of cameras and goals of research. Along these lines, and similar to some of
the concerns of sociocultural anthropologists, we also need to consider data storage
policies and decide who will have access to these images. What should we do if local
authorities request (or demand) copies of our camera trap images as a condition of our
research, or even after the research has taken place? Can we protect the anonymity of
the people in our photos, and, with reference to illegal activities, do we want to? Illegal
activity is likely to be the most ethically difficult (and common) potential scenario
researchers will face with camera trap studies. In some instances, providing photo-
graphic documentation to local authorities on illegal harvesting of forest resources,
hunting, or capturing animals could aid forest protection and prosecution of wrong-
doers. Yet, in other cases, this information may do little to further our conservation
agendas and could act to alienate local people and threaten our future research and
There are no simple answers to these complex issues, but we hope to initiate a
discussion on some of the ethical conundrums primatologists may face when using
camera traps and encourage forethought related to the conflicts that may arise when
using camera traps in primate research.
The articles in this special issue reflect a variety of primate studies that employed
camera traps and collectively provide a summary of the applications primatologists
are using. Camera traps are proving to be an effective tool in the documentation of
primate ecology and spatial distribution patterns. Further, as human activity con-
tinues to alter primate habitat and behavior, we suggest camera traps can monitor
primate populations that should not be habituated or whose behavior would be
greatly altered by human presence. However, camera traps are not a research
panacea and have inherent biases. We encourage primate researchers to test and
acknowledge these limitations and to use corrective and complementary techniques
when they are warranted. We also recommend that researchers adhere to method-
ological protocols and report qualitative and quantitative methods accurately to
facilitate intersite and -species comparisons. We particularly encourage further
research into the ethical concerns raised by using camera traps in primatological
Use of Camera Traps: Introduction
Acknowledgments We thank the editor of International Journal of Primatology, Dr. Joanna Setchell, for
help and assistance in the production of this special issue and particularly this editorial. In addition, we thank
our co-guest editor, Chia Tan, and Keith Riggle for their support, suggestions, and reviews of earlier versions
of the manuscript. We thank the symposium participants (Advancing Primate Research and Conservation
through the Use of Camera Traps) and attendees for their contributions and thought-provoking discussion
points. Funding was provided by the Austrian Academy of Science (M. LaFleur) and Wilderness Wildlife
Trust (P. A. Pebsworth).
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