Observation and Assessment of Wild Life With Camera

Reliable assessment of animal populations is a long-standing challenge in wildlife ecology. Technological advances have led to widespread adoption of many different techniques used to monitor wildlife populations, and a wide variety of field and analytical approaches have been developed and refined (Burton et al. 2015; Caravaggi et al. 2017). The use of remote field cameras is now more common in surveying wildlife distributions, abundances, behaviors, activity levels, and community structures (Robinson et al. 2014; Rowcliffe et al, 2014; Burton et al. 2015; Fuller et al. 2016; Moeller 2017). Methods for capturing animals on film when researchers are not present have been used in ecological research for decades but use of camera traps dramatically increased with the advent of commercial wildlife camera traps in the early 1990s (Kucera and Barrett 1993; Swann et al. 2011). Camera traps, or cameras that are remotely activated via an active or passive sensor, offer reliable, minimally invasive, visual means of surveying wildlife. Remote-sensing camera traps are becoming increasingly popular survey instruments, as they are a cost-effective, non-invasive method of study. Camera trap data often takes the form of a still image or video of an individual or group of individuals, of one or more species, which have been detected within the camera’s zone of detection (Caravaggi et al. 2017). These images and videos are often linked with relevant date, time, and location information.

Advantages and Limitations

Quantifying animal behaviors, distributions, or abundances can present many challenges. Direct observation of wildlife allows for assessment of individual responses to environmental or other anthropogenic stimuli (Caravaggi et al. 2017). However, a human observer may influence the behaviors and responses of the animals being monitored, and a human observer is limited in the number of animals a single person can observe (Caravaggi et al. 2017). Additionally, certain species and their corresponding habitats are not amenable to direct, field-based observations, or direct observation may be dangerous (Caravaggi et al. 2017; Moeller 2017). In the past, many of these species were monitored using radio (VHF) or satellite (GPS) telemetry, activity sensors, or biologgers (Caravaggi et al. 2017). However, many of these methods have significant logistical and inferential limitations, and thus, new methods of obtaining data are being developed. Camera traps, if used appropriately and within certain constraints, are among these increasingly popular new methods. Perhaps the biggest advantage of camera traps in comparison with other sampling methods such as direct observation, trapping, or tracking is that they can record very accurate data without the animal being captured or the researcher being present (Swann et al. 2011). These camera trap data, unlike data produced by live-trapping or human observations, can then be reviewed by other researchers as well.

The benefits of using camera trap designs in ecological research are well-represented in scientific literature. Despite these many advantages, camera trap systems also have several downfalls. The most common problems include loss of data, failure of trigger mechanisms to activate the cameras, lack of troubleshooting, and misfires resulting in many photographs with no animals in the frame (Swann et al. 2011). Many factors may influence the performance of camera traps. Poor performance of camera trapping equipment is usually caused by a combination of weather, user experience and skill, and unique conditions, such as poorly engineered equipment or damage to equipment by animals (Swann et al. 2011). In addition, there are great differences among types of camera traps in terms of their sensitivity, zones of detection, and performance under different environmental conditions (Swann et al. 2004). Some of these factors can be alleviated, whereas others, such as weather, are beyond immediate control. It is therefore important to know the problems of potential equipment and select traps suitable for local application.

Camera traps, while simple to use, are complicated by the fact that they are designed for use in many applications, under many field conditions, and for a wide range of target species (Swann et al. 2011). Research purposes may include studies of avian nest ecology, detection of rare species, estimation of population size and species richness, as well as research on habitat use and occupation of human-built structures (Swann et al. 2011). These unique applications may all have unique camera trap requirements. For example, a camera trap used to detect rare species in a remote area needs to be rugged and usable in a variety of weather conditions, reliable, and capable of operating and taking photographs for several weeks after it is set without being checked. In contrast, a camera trap used to monitor avian nest ecology must be quiet, unobtrusive, and capable of taking large numbers of photographs in succession. Differences in field conditions and target species may also influence choice of camera traps (Swann et al. 2011). A camera set up in the high humidity of a tropical field site experiences different technological challenges than a camera set up in the frigid Arctic. Ecological work in areas where vandalism is an issue or where large, curious animals may destroy cameras requires armoring or camouflage of equipment. And finally, camera traps used to study small, fast-moving animals such as birds require different trigger systems, lighting sources, and focal lengths than camera traps used to study large mammals or other taxonomic groups (Swann et al. 2011).

Validity for Wildlife Monitoring

The make and model of camera trapping equipment, and the settings and deployment protocols used have important consequences for species detectability and the interpretation and repeatability of camera trap results (Burton et al. 2015). It is thought that the large amount of variation in camera trapping equipment and protocols can cause significant heterogeneity in species detectability, especially within studies where protocols are not consistent (Burton et al. 2015). Additionally, details of sampling design are central to the interpretation and extrapolation of survey results (Burton et al. 2015). Many studies in the recent past have relied on poorly supported assumptions about the relationship between camera trap detections and ecological parameters of interest (Burton et al. 2015). The recent growth in popularity and applications of camera trap surveys suggest that creative methodological and analytical solutions will be increasingly used to investigate animal behaviors, including those in response to anthropogenic impacts (Caravaggi et al. 2017). Thus, it is also increasingly important to report methodological details of camera trapping surveys more consistently, especially to validate the use of camera traps to obtain certain types of data for analysis and extrapolation.