A camera trap is a remotely activated camera that is equipped with a motion sensor or an infrared sensor, or uses a light beam as a trigger. Camera trapping is a method for capturing wild animals on film when researchers are not present, and has been used in ecological research for decades. In addition to applications in hunting and wildlife viewing, research applications include studies of 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.
Camera traps, also known as trail cameras, are used to capture images of animals in the wild with as little human interference as possible. In recent decades, with advancements in the quality of camera equipment, this method of field observation has become more popular among researchers. Hunting has played an important role in development of camera traps, since hunters like to use them to scout for game. These hunters have opened a commercial market for the devices which have led to many improvements over time.
The great advantage of camera trapping is that they can record very accurate data without the animal being captured. These data are superior to human observations, because they can be reviewed by other researchers. They minimally disturb wildlife and can replace the use of more invasive survey and monitoring techniques such as live trap and release. They operate continually and silently, provide proof of species presence in an area, can teach what prints and scats go with which species, can provide evidence for management and policy decisions and policies, and are a cost effective monitoring tool. Infrared flash cameras have low disturbance and visibility. Besides olfactory and acoustic cues, camera flash may scare animals so that they avoid or destroy camera traps. The major alternative light source is infrared, which is usually not detectable by mammals or birds.
Camera traps are also helpful in quantifying the number of different species in an area; this is a more effective method than attempting to count by hand every individual organism in a field. It can also be useful in identifying new or rare species that have yet to be well documented. By using camera traps, the well-being and survival rate of animals can be observed over time.
Camera traps have revolutionized wildlife research and conservation, enabling collection of photographic evidence of rarely seen and often globally endangered species, with little expense, relative ease, and minimal disturbance to wildlife. Camera traps can document wildlife presence, abundance, and population changes, particularly in the face of deforestation and habitat destruction. Camera traps enable collection of baseline population data on elusive mammals and birds where only estimates — and often just guesses — were possible before. Camera traps are increasingly being used to raise conservation awareness worldwide, with Non-governmental organizations (NGO)s embracing the tool as a powerful way of reaching out to the public through electronic media. Wildlife conservation groups such as Panthera, Wildlife Conservation Society (WCS), World Wildlife Fund (WWF) have found camera trap videos and photos to be an important part of campaigns to save threatened or endangered species.
The earliest models used traditional film and a one-shot trigger function. These traditional cameras contained film that needed to be collected and developed like any other standard camera. Today, more advanced cameras utilize digital photography, sending photos directly to a computer, even though this method is uncommon it is still highly useful and could be the future of this research method. Some cameras are even programed to take multiple pictures after a triggering event.
There are non-triggered cameras that either run continuously or take pictures at specific time intervals. The more common ones, however, are the more advanced triggered cameras that go off only after sensing movement and/or a heat signature to increase the chances of capturing a useful image, infrared beams can also be used to trigger the camera. Video is also an emerging option in type of camera traps, allowing researchers to record running streams of video, to document animal behavior.
The battery life of some of these cameras are another important factor in which cameras are used; large batteries offer a longer running time for the camera but can be cumbersome in set up or when lugging the equipment to the field site . 
Weather proofing for cameras has helped to protect the film from damage and even the cameras themselves. The cameras are often put into waterproof housing; these casings can also help in disguising the equipment from animals.
Noise-reduction housing is helpful in limiting the possibility that animals will be disturbed by the camera and possibly relocate. Sound recording is also another feature that can be added to the camera. This is useful in recording animal calls and in noting the times when specific animals are the most vocal.
Effects of weather and the environment
Humidity has a highly negative effect on camera traps and can result in camera malfunction. This can be problematic since the malfunction is often not immediately discovered, so a large portion of research time can be lost. Often a researcher expecting the experiment to be complete will trek back to the site, only to discover far less data than expected – or even none at all.
There is also the possibility, if it is a motion activated camera, that any movement within the sensitivity range of the camera’s sensor will trigger a picture, so the camera might end up with numerous pictures of anything the wind moves, such as plants.
The best type of weather for it to work in is any place with low humidity and stable moderate temperatures.
As far as problems with camera traps, it cannot be overlooked that sometimes the subjects themselves negatively affect the research. One of the most common things is that animals unknowingly topple a camera or splatter it with mud or water ruining the film or lens.
One other method of animal tampering involves the animals themselves taking the cameras for their own uses. There are examples of some animals actually taking the cameras and snapping pictures of themselves.
An interesting side note is that locals in the area of a camera trap who sometimes use the same game trails as the animals to move through the forest can be caught on camera. This adds to the human dynamic of the research and can make camera’s a useful tool for anti-poaching or other law enforcement effort.
One of the most important things to consider when setting up camera traps is choosing the location in order to get the best results. Camera traps near mineral licks or along game trails, where it is more likely that animals will visit frequently, are normally seen. Animals congregate around mineral licks to consume water and soil, which can be useful in reducing toxin levels or supplement mineral intake in their diet. These locations for camera traps also allow for variety of animals who show up at different times and use the licks in different ways allowing for the study of animal behavior.
Another major factor in whether this is the best technique to use in the specific research is which type of species one is attempting to observe with the camera. Species such as small-bodied birds and insects may be too small to trigger the camera. Reptiles and amphibians will not be able to trip the infrared or heat differential-based sensors, however, methods have been developed to detect these species by utilizing a reflector based sensor system. However, for most medium and large-bodied terrestrial species camera traps have proven to be a successful tool for study.
- Swann, D. E., Kawanishi, K., Palmer, J. (2010) Evaluating Types and Features of Camera Traps in Ecological Studies: A Guide for Researchers. In: O'Connell, A. F., Nichols, J. D., Karanth, U. K. (Eds.) 2010. Camera Traps in Animal Ecology: Methods and Analyses. Springer, Tokyo, Dordrecht, London, Heidelberg, New York. ISBN 4-431-99494-7. Pages 27–43.
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- O'Connell, A. F., Nichols, J. D., Karanth, U. K. (Eds.) (2010). Camera Traps in Ecology: Methods and Analyses. Tokyo, Dordrecht, London, Heidelberg, New York: Springer.
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- An application of camera traps in ornithological research
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