Camera Trapping for Animal Monitoring and Management: a Review of Applications Don E
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1 Camera trapping for animal monitoring and management: a review of applications Don E. Swann and Nic Perkins Abstract Introduction Camera traps are being used throughout the world Cameras that record images of wild animals when to address a wide range of issues in wildlife man- humans are not present have a long history in ecol- agement and to address both research and man- ogy, but their use dramatically increased with the agement questions that cannot be easily answered introduction of commercial infrared-triggered with other methods. In addition to detecting rare cameras in the early 1990s. Today, the term ‘camera species and providing answers to practical man- trap’ typically refers to cameras units that are trig- agement questions, camera traps have a potentially gered by the movement of an animal within a large role in assessing global changes in biodiver- detection area, although the term also can describe sity of mammals. The quality of camera traps is cameras set to take photos at set time intervals. continuing to improve, and field and analytical Nearly all camera traps used in current wildlife techniques are also moving rapidly forward. This applications are small (the size of a shoebox or paper reviews the current state of camera trapping smaller), consist of only one piece, shoot digital still in wildlife ecology with a focus on new and or video images, and are passively triggered using emerging applications in management and moni- an infrared light source. Nevertheless, a dazzling toring. Recent papers, including many in this array of commercial camera traps and optional fea- volume, indicate that camera traps have the poten- tures are available (Rovero et al. 2013; Swann et al. tial to be a powerful new tool in areas of animal 2004, 2011; <http://www.trailcampro.com>), and ecology where they have not previously been these can be further modified by researchers. widely used, such as estimation abundance, sam- Camera traps have been applied to nearly every pling of small animals, and establishing conserva- aspect of vertebrate ecology, including to study tion priorities based on regional monitoring. In nest ecology, research activity patterns and behav- addition, the use of camera traps by citizen scien- iour, document rare species or events, and estimate tists and environmental educators continues to state variables such as species richness, occupancy, grow and become more integrated with more tra- abundance (Cutler and Swann 1999; Kucera and ditional scientific studies. Barrett 2011). Data recorded by camera traps 061402 Camera Trapping 1pp.indd 3 23/06/2014 3:13 pm 4 PARt 1 – CameRA TRappiNG FOR ANimal MONITORING: CASE STUDIES typically consist of an image (e.g. Plate 1.1), series Chapter 10). Kucera and Barrett (2011) list several of images, or video of an individual or group of recent examples, including a new species of striped animals within the area of detection covered by the rabbit (Nesolagus timminsi) in South-east Asia (Sur- camera trap, as well as other information such as ridge et al. 1999), a range extension for the Sulawesi the date, time, and location of the photograph. palm civet (Macrogalidia musschenbroekii) (Lee et al. Because most individuals in the image can be iden- 2003) and the documentation of the wolverine tified to species, the trap thus records the presence (Gulo gulo) in California for the first time since 1922 of that species at that place and time. Other infor- (Moriarty et al. 2009). Camera traps also have been mation, such as behavioural data (e.g. Meek et al. used to reliably estimate, for the first time, the 2012) or events such as predation or feeding (e.g. abundance of the tiger (Panthera tigris; Karanth and Zimmerman et al. 2011) can also be recorded. In Nichols 1998) and other species where individuals some cases individual animals can be identified can be readily recognised based on their spot pat- either through tags previously affixed by research- tern. After many years of debate and poor informa- ers or by unique natural marks. Some data gath- tion on the number of species of mammals present ered by physical trapping techniques, such as in natural areas, camera traps are now producing reproductive condition and genetic data, cannot reliable estimates of species richness and other usually be obtained by camera traps, but camera community measures (Tobler et al. 2008; O’Brien et trap data are often combined with other techniques al. 2011) that are not based on poor-quality observa- such as radio-telemetry (e.g. Larrucea et al. 2007) tional data or generalised range maps (e.g. New- and genetics (e.g. Janečka et al. 2011). mark 1995; Parks and Harcourt 2002). Despite the limits of the data that can be gath- As demonstrated at the First International ered by camera traps, experience during the past Camera Trapping Colloquium in Wildlife Manage- two decades indicates why they are powerful tools ment and Research, new developments in camera for addressing conservation of populations of trapping are arriving at a staggering pace. Camera native species, especially mammals. First, camera traps themselves are rapidly evolving, becoming traps provide basic knowledge of the distribution faster, cheaper, more resilient, and more versatile of mammals (their presence in a certain place), (Meek 2011). Researchers are developing new tech- which is essential for conservation on both the niques for deploying them, including using verti- local and regional scale, but often previously lack- cal mounts (Swann et al. 2004; Welbourne, Chapter ing for the many species that are nocturnal, avoid 20). More researchers are aware that detectability is humans, and seek cover. Second, they are relatively always < 1 in camera studies (Kéry 2011) and are inexpensive, which means they can be deployed becoming more adept and sophisticated at analys- very efficiently to increase sample sizes over wide ing camera trap data using occupancy and other areas (De Bondi et al. 2010). And third, camera traps methods (O’Connell and Bailey 2011). They are rap- are relatively non-invasive and safe for both idly improving methods for managing data, humans and animals. From a practical point of including extracting data directly from photos, view, it is obviously much easier to sample popula- eliminating the need for data entry, and even tions of very large mammals with camera traps developing methods for using pattern recognition than with live traps. to identify animals automatically (Falzon et al., As a result, camera trapping has been truly sig- Chapter 28). And of course, they are improving nificant for wildlife management and conservation methods for sharing data through the internet and throughout the world. Camera traps have docu- cell phone applications. mented species that are new to science, or occur in What is truly exciting about camera trapping in areas where they were thought to be locally extinct the modern era is that the explosive adoption of or not previously known to exist (e.g. Sangay et al., this technology, in synergy with improvements in 061402 Camera Trapping 1pp.indd 4 23/06/2014 3:13 pm 1 – CameRA TRappiNG FOR ANimal MONITORING AND maNAGemeNT 5 camera trap quality, wildlife data analysis, and animals) and the characteristics of animals that information management, is resulting in novel can be determined from videos taken at the camera applications in wildlife conservation around the sites, including its size and speed. world. It is a testament to the rapid advances in One of the complications of using the REM has camera trapping that several important develop- to do with the difficulty of accurately estimating ments in camera trapping have occurred since the the area of the detection zone. Although this prob- very recent publication of a major book on the sub- lem has been addressed using distance sampling ject, Camera Traps in Animal Ecology (O’Connell and techniques by Rowcliffe et al. (2011), papers pre- Bailey 2011). The goal of this paper is to provide a sented in this volume (e.g. Welbourne, Chapter short summary of some of these applications and 20) suggest that another approach may be to explore their potential for creating ground-break- mount cameras vertically (facing down at the ing developments in the coming years. ground), so as to more precisely control the area of detection. This approach may not be appropri- ate for larger animals in tropical areas where a Estimating animal abundance and density large amount of vegetation is present, but might Camera traps are often used to provide an index of work in less vegetated areas and for smaller mam- abundance (also called relative abundance), such mals in most habitats. as the number of photos of a species per trap night. However, indices typically provide biased esti- mates of abundance (Anderson 2001), which in Studying small animals camera trapping is primarily due to spatial varia- Another interesting new direction for camera trap- bility and detectability (O’Brien 2011). Many users ping is in studies of smaller animals, including of camera traps assume that the number of photo- mammals such as insectivores, rodents, and small graphs per unit time is an accurate reflection of the marsupials, as well as birds and herpetofauna (e.g. number of individual animals present. However, Welbourne, Chapter 20). Camera traps have been this assumption may not be valid because many used in small mammal research for some time, but factors may influence the number of photographs, typically to determine temporal patterns (e.g. Pear- including attraction to the camera trap, trap shy- son 1959). Recent work on small mammals with ness, use of or type of attractant, weather, ability of more accurate new commercial traps, particularly the camera trap to detect an animal when present, in Australia with ReconyxTM brand traps that pick and others.