Camera Trapping for Wildlife Research

This chapter addresses the general practicalities of deploying camera traps in the field, irrespective of the study design (unless explicitly stated). For additional details we also refer to Rovero et al. (2010), Team Network (2011), Ancrenaz et al. (2012), Meek et al. (2012), Sunarto et al. (2013) and van Berkel (2014). The study aim, and consequent sampling design, will determine the type of camera trap, the number of camera stations and cameras per station (single or pairs) to be set, their location and placement, and the season and duration of the sampling (Chapters 5–9). These factors will in turn determine the duration of the fieldwork, and the personnel, transport and infrastructure needed. In general terms, local expertise among the field team and the involvement of local personnel in the field (e.g. rangers, hunters, nature lovers) will be critical for choosing suitable camera trap sites even for studies that target the whole community of medium-to-large terrestrial vertebrates and for which a random sampling is recommended, such as in occupancy studies (Chapter 6).

Under some particular circumstances – e.g a new study area for which very little knowledge is available – a pilot study prior to the survey itself may be critical (Silver 2004; Jackson et al. 2005). This will help researchers identify suitable camera trap sites, ensure that a large enough area can be sampled, test the equipment under the specific field conditions, optimise the settings and positioning of the camera traps, train the field staff, and make contact with the local community ahead of the survey. While setting camera traps is relatively easy, trained field personnel are needed at all stages to ensure proper setting and retrieval of cameras and strict adherence to the sampling and camera-setting criteria needed for the particular study.

Once the sampling design has been defined (see Chapters 5–9), we propose that the following key steps are considered before any fieldwork is conducted:

1.Ensure that all requested authorisations are acquired from relevant authorities and local communities.

2.Ensure that means of transport, infrastructure (e.g. field station), and field staff and/or trained volunteers are available to conduct the survey during the specified period.

3.Make a list of all the equipment needed to conduct the survey including spare material (see below).

5.Plan in detail the itinerary of field days with a list of all the material needed, for each field team if multiple teams are involved, and for each field day (see below for checklist of material).

We strongly recommend mapping the camera locations (using a global map of the study area showing the field site(s) and a detailed map for each site(s)) and storing them in a GPS unit. This will assist precise navigation in the field (or to the sampling area). As a back-up it is also useful to have a hard copy of the camera site localities in case the GPS-stored locations are lost.

•Camera traps (including extra units), cables or mounting brackets with adjustable mounts (heads) to affix camera traps to trees.

•Portable devices to visualise images from cards in the field (e.g. a digital camera, a card reader, a tablet or a smartphone).

•Plastic binder containing a checklist of all equipment needed for daily trips to set up cameras, camera field guides, forms for recording metadata (camera trap setting and retrieval data and habitat forms), and printed copies of the map of the entire study area showing the field site(s) and detailed maps for each site(s), and the list of coordinates of all the camera sites.

•Umbrella to keep the camera dry in rainy conditions when checking the camera trap.

•Whiteboard (or blackboard) and marker pen to take ‘start’ and ‘end’ images.

•In areas with frequent human presence, laminated information sheets with contact address, aims of the study and information related to the protection of privacy (e.g. disclaimer note stating that images of humans and pet animals will be deleted); see Chapter 11, section 11.5.4.

•Additional useful items are: toolkit with pliers, knife, foldable saw to remove branches, lighter, pins (for posting information sheets), small SD card labels, pencils, opaque tape (to limit the range of the flash or motion detector), battery tester, small boxes for storing SD cards and a compass to avoid directing the camera trap towards the sun.

AIR camera traps may also need spare electric cables, cable ties or plastic straps to fix the electric cable to the supports to prevent animals from pulling out the cable plugs, and electrical tape to protect cables from being chewed by animals or to repair damaged cables. Setting the separate elements of AIR camera traps will usually require installing poles (using a pole pounder or heavy axe) as there may not be suitably placed trees to set each element at the right distance and angle from the target area.

While the above is meant to be a detailed list for a general study, the study area and context will determine the precise list or require additional items. In snowy conditions, for example, it may be useful to have a light shovel to remove snow from the camera traps (which are generally set 40–50 cm above ground level) and the area in front of them, and snow shoes or cross-country skis to make a trail of packed snow by walking up and beyond the trap a good distance as this allows animals to be directed through the camera trap site. In a humid climate placing packets of desiccant (reuseable silica gel) inside the camera box helps protect the unit from extreme moisture, but these need to be replaced and dried often.

All settings need to be determined before the fieldwork and will depend on the study design (see Chapter 2). The fundamental settings are: (1) camera settings – date, time, photo and/or video mode and resolution, number of photos taken per trigger or video duration; (2) sensor settings – sensitivity, minimum time between photos; (3) flash intensity if adjustable; and (4) time-lapse mode (on/off). All cameras should be set and tested – including camera software updates – before travelling to the field so that they just need to be activated before use. This in turn implies that batteries need to remain inserted in the devices, to avoid losing camera settings. We also recommend using the correct type of SD card according to the information provided in the camera trap manual.

We recommend the use of rechargeable batteries (see Chapter 2), and it is important to stress that after fieldwork rechargeable batteries should be stored in charged state in a cool (i.e. around 15°C), dry, clean place, away from heat and metal objects, to maximise battery performance. The optimal level of charge for storing batteries depends on the type of batteries themselves, hence users should check the instruction manual provided by the manufacturers. As batteries will self-discharge during storage, before re-use they usually need to be recharged. Hence, it is recommended not to charge the batteries too early because they lose their capacity very quickly and might not be fully charged when used in the field. The time needed to charge the batteries before, during and after deployment needs to be considered in the study plan. This in practice means ensuring that a sufficient number of battery chargers are available; in addition, a supplementary set of batteries will be needed when batteries are replaced in the course of sampling. A battery tester may be useful in the field, especially for checking the charge level when setting/checking camera traps. Moreover, when carrying batteries during fieldwork it is important to ensure that there is no contact between poles of different batteries to prevent unexpected discharge and to store them well away from snow and/or water.

We recommend that each camera trap unit be uniquely numbered, or otherwise coded, for identification purposes. Write the code with a permanent marker or carve/etch it on the housing of each camera trap. Some digital camera traps can print a code automatically at the bottom of each photograph. The code of each camera can also be used as ID in the camera trap and picture databases. When a large number of camera trap units are used, we suggest creating a registry of the units (including a record of the brands, type of motion detector, year of activation, if the camera trap is still functional or not, if it is in the office or loaned to a volunteer, and special remarks). This will enable a quick overview of the devices that are available or in need of repair. Similarly, label the memory cards with the site and camera trap number; a progressive number can also be added in case multiple memory cards are used in the same camera during the course of the study.

Although the choice of specific camera sites will depend on the sampling design, the standard approach is to place the cameras at locations that maximise capture probability of the target species. Hence, knowledge about the signs of wildlife presence is essential. In the absence of animal signs or information from local guides, camera traps are generally set along wildlife trails, existing human trails (e.g. forest roads, hiking trails), or at the intersection of several trails. Other suitable sites are river crossing points (e.g. bridges), ridgelines or valley bottoms, or when a trail is narrowed by features (e.g. rocks) on either side.

With a few exceptions, e.g. capture–recapture studies that need paired camera traps (Chapter 7), usually one camera trap is set per site. It is recommended whenever possible to choose a camera trap site where the ground is relatively flat. Camera traps are most often strapped directly to a suitably located tree (preferably a straight and smooth one), but they can also be mounted on wooden poles (either brought in or made on site) – the latter allow for precise and repeatable placement. Alternatively, the use of mounting brackets with adjustable heads enables a quick setting and the optimal and precise orientation and fixing of the camera on any type of support, even on trees that are inclined and/or gnarled (Figure 3.1).

The most suitable height will be determined by the target species, the objective of the study and the camera trap functionality. For medium-to-large mammals setting camera traps at about 40–50 cm above ground level is standard. Particular habitat settings will need ad-hoc camera positioning; for example, in rocky and treeless landscapes, such as most of the snow leopard habitat, camera traps are mounted on natural-looking cairns made of rocks, which both protect and hide camera traps (e.g. Jackson et al. 2005). For a recent study on snow leopards (Panthera uncia) in Mongolia, the chapter authors successfully used wooden boards carved so that the base of the camera traps fitted into them, allowing for easier placement of camera traps on rocks.

The position and distance of the support (tree, pole, etc.) relative to the trail centre or passing area, which needs to be centred in the image frame, should be chosen based both on target animal(s) and camera specifications. If the study is targeting a small species the camera will need to be relatively close to the target area so that individuals will not appear too small in the frame. However, camera specifications will also determine the minimum distance; in particular, cameras can be kept close if their trigger speed is fast (see Chapter 2), whereas a greater distance will be required for cameras with slow trigger speeds. The flash intensity will also determine the minimum and maximum distance. In general, we recommend a distance of 3–5 m from the camera to the centre of the trail/area through which the target animal is assumed to pass. The intensity of the flash can be reduced ‘manually’ by sticking on opaque tape if the camera trap does not offer the option of adjusting the flash via its settings (Figure 3.2). The same arrangement can be used to adjust the detection zone, by manually limiting the motion detector width.

Figure 3.1 Mounting brackets with adjustable heads enable rapid setting, and offer optimal and precise orientation and fixing of the camera trap on any kind of tree. (Fridolin Zimmermann)

Camera traps are usually set perpendicular to the trail to obtain a good side image of the passing animal (important for identification of species and individuals); however, they can also be placed slightly off perpendicular to the trail (i.e. about 60° between camera trap aim and trail) to increase the portion of trail covered by the frame and the detection zone, thus increasing the detection rate for PIR camera traps. For specific research aims, such as determining the minimum group size of group-living animals (e.g. wolves), the angle of the camera trap aim may be better placed more parallel to the trail than the standard setting to maximise the number of individuals detected simultaneously. However, we recommend not to orient the camera traps beyond 45° relative to the target trail for two reasons: (1) with increasing orientation the images will be of either the heads or backs of passing animals; and (2) the functionality of the PIR motion detector may be compromised. This is because when an animal walks straight towards the camera trap it hits the two vertical sensors of the PIR simultaneously, and this does not trigger the camera trap as the PIR detector works by sensing the differential between the two sensors (see Chapter 2, section 2.2). Moreover, the smaller the angle between the camera detection axis and the animal trail, the smaller the motion of the animal relative to the sensors, and this in turn lowers the sensitivity of the PIR detector (A. Pittet, personal communication 2015).

Figure 3.2 The intensity of a xenon flash can be reduced ‘manually’ by sticking opaque tape in the middle of the flash if the flash cannot be modulated via the settings of the camera trap. The same can be done with infrared LED flashes, by covering the first one or two top or bottom rows of LEDs. (Fridolin Zimmermann)

We recommend testing the positioning of the camera trap to determine the detection zone. This can be done using the camera’s ‘walk test’ mode, a red LED lighting when the camera senses a person moving in front of it (effectively acting like a passing animal) and by checking it at different distances and directions relative to the trap. This helps with the initial positioning of the unit, which should then be refined by taking test images. This step is critical to assess the camera’s field of view, which may not coincide with the sensor’s detection zone (Chapter 2) and enables a check to be made if the pictures are well framed. Viewing test images can be done by using an ordinary digital camera, having previously checked that it can read the specific image format of the camera trap. Alternatively, image viewers, tablets or smartphones can also be used if these are able to read SD cards. Also, a number of camera trap models mount monitors in the unit, but these are very small and consume excessive amounts of battery power.

For sites with steep terrain, when using single camera traps these should be set on the downhill side relative to the target area to ensure that the camera is approximately at the same height as the target (Figure 3.3). In addition, and especially on narrow trails in steep terrain, camera traps can be fixed to the side of a tree via mounting brackets, to increase the distance from the camera to the centre of the trail while reducing the chance that animals touch the camera trap itself.

Figure 3.3 Single camera traps in sites with steep terrain should be set on the downhill side relative to the target area (left, camera circled in red). If placed on the uphill side (right), animals, especially smaller ones, will be missed and movement and sunlight in the background can cause false triggers. (Fridolin Zimmermann)

Because of the shape of the detection zone of the sensors used in PIR camera traps, a camera trap set on an ‘ideal’ site (i.e. with a vertical support and flat terrain) will need to be inclined slightly downwards for optimal performance (Meek et al. 2012). This ensures that animals passing closer to the camera relative to the target area are not missed; at the same time, it limits the far end of the detection zone, hence preventing animals passing beyond optimal camera range (i.e. more than approximately 8–10 m from the camera) from triggering the camera but not appearing clearly on the image or not being properly illuminated by the flash. Depending on the study, the optimal position of passing animals can be chosen by selecting obligatory passages, for example because of dense vegetation or a rock limiting the far side of the frame (Figure 3.4).

In densely vegetated areas we recommend removing branches in front of the camera and cleaning the ground in front of the camera trap of debris and vegetation that could cover the animal or reflect the flash causing the image to be overexposed. Vegetation moving in the wind can even falsely trigger the camera trap (Figure 3.5). Clearing the area will also avoid plant regeneration when the camera trap is kept unattended in the field. In addition, because PIR camera traps can be triggered by sunlight impinging directly on the sensor or reflected off the ground or vegetation in front of the sensor, camera traps should not be directed towards sunlit areas or large rock faces which may absorb heat and cause false triggering. In cold climates and during winter it is important to account for the variable height of the site targeted due to snowfall and melting. This ideally requires adjusting the camera trap positioning accordingly over the course of the survey. Alternatively, the camera trap can be set higher than normal in anticipation of snowfall or at sites that are less exposed to snowfalls, such as under large trees.

Setting AIR camera traps is more complex as they consist of different elements. The transmitting and receiving units should be set at an appropriate height above ground level, measured at the location of the target species’ expected path of travel where it intersects the infrared beam. The target point can be positioned exactly where it is wanted in the frame by directing the infrared beam to the right location. Electric cables should be sheathed to protect them against damage by animals.

Figure 3.4 Obligatory passages such as those created by dense vegetation, large rocks, cliffs or human constructions (e.g. bridges, walls or wood piles) can be used to ensure the animals are centred in the field of view of the camera traps. (Fridolin Zimmermann)

Figure 3.5 Branches and vegetation in front of the camera should be removed and the ground in front of the camera trap cleaned of debris and vegetation, as they could cover the animal or reflect the flash causing the image to be overexposed. Moving grass or branches can even falsely trigger the camera trap. (KORA)

Once the camera unit is placed, the following sequence should be done to make it ready for use:

•Check the detection range and take a test image to ensure the camera is functioning and is correctly set.

•Activate the camera and take a ‘start’ photo of a field team member holding a whiteboard or blackboard with the following information: camera unit ID, start date and time, name of the person holding the board. We recommend making trial ‘start’ photos as depending on flash type, colour of the board, and inclination of the board relative to the camera, the writing on the board may not be visible.

As mentioned earlier, the exact camera trap location should be recorded using a GPS unit and in dense forest the site can be flagged to find it more easily the next time, though this can expose the camera trap to theft. In addition to marking the locality on the GPS itself, the latitude and longitude (and coordinate system) should be recorded on a form (Appendix 3.1) along with other metadata, namely: camera trap ID number, site number, local name (when available), camera model, memory card number, start date and time, camera trap settings (useful if several people check the camera trap sites and later on when the data are analysed). Depending on the study, additional data on the habitat type or any other relevant information can be collected (e.g. presence of roads nearby, particular signs or features such as waterholes found at the site, den sites, animal tracks, etc.).

If information panels for passers-by are used, they should not be set right by the camera trap itself because people will go right up to the camera to read them. This would lead to a high number of non-target pictures.

Modern camera traps have a long autonomy which will partly depend on the battery type used (Chapter 2) and memory card capacity. Although battery duration and memory card capacity are not limiting factors, camera traps may fail due to water ingress, animal and human inference, or from mud or snow on the lens, fallen branches or fast-growing vegetation blocking the field of view, or for unknown technical problems. Thus camera traps should ideally be visited frequently enough to reduce their down time. In areas with frequent risks of interference (from humans or large mammals) cameras may need to be checked on a weekly or biweekly basis, while in areas with a low risk of disturbance monthly camera trap checks may be sufficient. When surveys are conducted in temperate zones during winter time, it becomes important to check the sites regularly (e.g. once a week) especially after fresh snowfall or periods of thaw.

•When arriving at the site a picture with a board similar to the ‘start’ photo should be taken to check if the camera trap is still functioning. The board need only mention date and time in this case.

•Check if date and time, and other settings are correct before switching off the camera trap (if not, report it on the form; see Appendix 3.2).

•Record the date of the control or removal and the number of pictures on the counter on the form. If the camera trap is not functioning, the reason (e.g. batteries out of power, memory card full, camera covered with snow, sabotage, etc.) if known should be recorded on the form; see Appendix 3.2).

•Replace the memory card. Check the battery indicator if the camera trap has one and change the batteries when necessary. If the camera trap has no battery indicator it is advised to use a portable battery checker (otherwise it is necessary to rely on previously testing the camera autonomy with the batteries actually used).

•Visualise the images with a portable device to see if they are well framed, whether there is vegetation in the way, whether there is a problem with sunlight causing blank photos, to detect possible camera trap failure (e.g. black picture because of non-functioning flash) or how well the camera trap is performing in terms of the number of images of animals. For site settings with pairs of camera traps, check if both camera traps have approximately the same number of pictures. If there is a marked discrepancy, check the sensitivity of the motion detector of the camera trap with the lowest number of pictures and if necessary replace the camera.

•Test the camera trap if it did not take any pictures, especially if you have good reasons to assume that animals passed in front of the camera (e.g. fresh tracks), and if needed replace it.

•After checking the camera trap, the orientation of the camera traps should be readjusted and tested following the same procedure as described when the traps were first placed in the field.

•Before leaving the site make sure that the device is switched on with the date and time correctly set, and that the camera trap is well oriented, fixed firmly to its support and locked to avoid damage and theft; finally, take a photograph using the black/whiteboard with the same information as when the camera trap was activated.

Upon retrieving camera traps, an ‘end’ image should be taken similarly to the ‘start’ one using the black/whiteboard. Information on camera functioning and any other notes should be recorded on the form.

After completing the fieldwork, all the camera traps should be checked for additional data stored in their internal memory (if they have one); any such data should be recovered on a memory card labelled with the site and camera trap number, and subsequently saved in the appropriate data folder. Finally the internal memory should be formatted to remove all pictures. The camera traps should subsequently be cleaned carefully, i.e. avoid scratching the lens, with a glass cleaner, especially the glass in front of the camera and the lens of the PIR. The traps should then be tested and if necessary and possible repaired. Upon completion of the study, the traps should ideally be stored in plastic boxes in a cool, dry and clean place. The camera trap units’ database should be update with the latest information from the inventory. All batteries and additional accessories (poles, mounting brackets, cables, locks, etc.) should be sorted, maintained (e.g. rechargeable batteries need to be stored charged) and inventoried. All broken or missing material should be replaced right away. Ideally all material should be stored separately in appropriate storage units labelled according to their content so that the material can easily be found by any of the field staff at the beginning of the next survey.

Ancrenaz, M., Hearn, A.J., Ross, J., Sollmann R. and Witting, A. (2012) Handbook for Wildlife Monitoring Using Camera-traps. BBEC II Secretariat, c/o Natural Resources Office, Chief Minister’s Department, Kota Kinabalu, Sabah, Malaysia.

Jackson, R.M., Roe, J.D., Wangchuck, R. and Hunter D.O. (2005) Surveying Snow Leopard Populations with Emphasis on Camera Trapping – A Handbook. Sonoma, CA: The Snow Leopard Conservancy.

Karanth, K.U. and Nichols, J.D. (2002) Monitoring Tigers and Their Prey: A Manual for Researchers, Managers and Conservationists in Tropical Asia. Centre for Wildlife Studies, Karnataka, India.

Meek, P.D., Ballard, A.G. and Fleming, P.J.S. (2012) An Introduction to Camera Trapping for Wildlife Surveys in Australia. Invasive Animals Cooperative Research Centre, Canberra, Australia, http://www.feral.org.au/camera-trapping-for-wildlife-surveys (accessed 2 October 2014).

Rovero, F., Tobler, M. and Sanderson J. (2010) Camera trapping for inventorying terrestrial vertebrates. In: J. Eymann, J. Degreef, C. Häuser, J.C. Monje, Y. Samyn, and D. Vanden-Spiegel (eds), Manual on Field Recording Techniques and Protocols for All Taxa Biodiversity Inventories and Monitoring. Abc Taxa, Vol. 8 (Part 1). pp. 100–128.

Silver, S. (2004) Assessing Jaguar Abundance Using Remotely Triggered Cameras. Jaguar Conservation Program, Wildlife Conservation Society, New York.

Sunarto, Sollmann, R., Mohamed, A. and Kelly, M.J. (2013) Camera trapping for the study and conservation of tropical carnivores. Raffles Bulletin of Zoology Supplement 28: 21–42.

TEAM Network (2011) Terrestrial Vertebrate Protocol Implementation Manual, v. 3.1. Tropical Ecology, Assessment and Monitoring Network, Center for Applied Biodiversity Science, Conservation International, Arlington, VA, USA. http://www.teamnetwork.org/protocols/bio/terrestrial-vertebrate (accessed 22 April 2015).

van Berkel T. 2014. Camera Trapping for Wildlife Conservation. Expedition Field Techniques. Royal Geographical Society: London.

¹ It should be noted that camera traps can be stolen regardless of locks, therefore in some circumstances frequent relocation of cameras to prevent theft or vandalism may be needed (Karanth and Nichols 2002).