Course:CONS200/2021/The use of camera traps for conservation: Advances and limitations
George Shiras III, an American congressman, is widely credited as being the first ‘camera trapper’, way back in the 1890s.It was quite a simple idea – a tripwire would trigger a camera and flash units. This tripwire could have bait attached or simply be low along the ground. His photographs were published in the July 1906 issue of National Geographic, which was almost completely filled with his photography. Though Shiras did this for pleasure, and later to promote conservation, he didn’t use it for science. Frank M. Chapman would be the first to do that. He was on Barro Colorado Island in Panama and had seen tracks left by at least two cat species, though he did not know which. He realised a camera trap may give the answer and used the same technique as Shiras.
Right now, A camera trap is used by biologists and conservationists to capture images of wildlife with as little human interference as possible. It is typically equipped with a motion sensor – usually a passive infrared (PIR) sensor or an active infrared (AIR) sensor using an infrared light beam (WWF). In this article we will elaborate the use of camera traps for conservation and its advances and limitations.
Advances of camera traps
Camera trapping has become a widely used tool for monitoring wild species, providing video and images for research on interested species due to its convenience and stability. It is a common and non-invasive tool that can be used under almost any soil and weather condition. This means camera trapping is independent of human operations. Wild animals are usually vigilant because of the presence of humans, the target objects will probably run away or disappear once they are alerted by someone who is holding a camera. Another limitation is that photographers or observers probably will not be able to stay long enough under a harsh environment until the interested objects appear, even if they have found the interested objects, the time for them to gather information is limited due to a too cold or too hot environment and threats from dangerous species. These problems will be solved by setting up camera traps. Since camera trapping can operate by itself under almost any conditions and any time, it’s much easier to obtain large quantities and good quality of videos and photos to find, recognize wild animals and obtain a lot of detailed information.
Camera traps has proved itself to be a useful tool for identifying large variety of species and its reliability to correctly estimating features like sex, age, population structure and density with an appropriate setup . By analyzing these features thus, we are able to study wild animal’s habits, birth rate, well-being, and their class system if applicable. Even though traditional surveys are also efficient, and it’s much cheaper compared to camera trapping, but it’s highly dependent on environment conditions and requires experienced personnel. Camera trapping is a better and more efficient way for surveys, as it’s neither dependent on environmental conditions nor experienced researchers, it also does not require highly intensive field work. Another very important aspect is: camera trapping makes the studying of rare, endangered species possible when the monitoring is restricted or prohibited by authorities, as the presence of humans when monitoring will disturb endangered species, cause panic or even harm. Since the existence of camera trapping can be easily simulated to objects that are able to blend into the environment, like woods, rocks or even fake animals, thus negative effects to wild animals can be lowered or eliminated.
Camera trapping has emerged in recent years as an ideal way of observing wildlife in remote locations without the interference of a human presence. In this sense, the new technology now provides conservationists with the ability to measure natural wildlife activities and population density in real time, which is a wonderful advantage over the previous method of direct observation, which could result in lower wildlife counts as wild animals are adapted to steer clear of humans, thus hiding their true presence in nature to some extent. Rovero and Zimmerman (2016) report that camera trapping is an excellent means of spotting and identifying new species as well as tracking the population health of rare or endangered species. One of the particular advantages of camera trapping is that it is fairly non-invasive, and provides a way of capturing the natural behaviour of wild species. The absence of humans during the phase of observation ensures that the data truly represents the behaviour of animals in the wild without any human interference. Certainly, the presence of humans – when they are on site to observe directly – can cause many species to retreat. Sharma et al. (2020) acknowledge just how useful camera trapping is, particularly when researchers are looking for elusive species – ones which are very shy when humans are nearby. In particular, the newest cameras can be left in place for a month, and only take photographs when an animal passes the camera. Together with the imagery and time-stamping, an accurate record can be kept of the distribution of animals, their habits, and even the particular behaviour of a single animal.
Another advantage of camera trapping is that it can record human behaviour in a certain area, and this can include illegal behaviours (Sharma et al, 2020). While there are natural concerns about preserving people’s privacy, when people are on Crown land, they are subject to laws against illegal hunting, fishing and trapping. Therefore, the camera trap can prove helpful in reducing the extent of human activities which are harmful to nature, and provide evidence which can be used in court to prosecute those who are abusing wildlife (Sharma et al, 2020). Overall, camera trapping is an efficient and accurate means of measuring and observing wildlife, and also serves as an effective means of deterring poaching and other activities which are harmful to wildlife species.
Limitations of camera traps
Operational issues：Camera trap takes pictures by sensing the displacement of objects within the field of view, this feature makes it possible to take multiple pictures and store them frequently. Each camera can take a few thousand pictures per month. When there are multiple cameras in a camera trap, it can produce tens of thousands or more pictures a year. This poses a challenge to the storage capacity of the data and is a huge workload for the image optimization process based on weather data. It takes around 14 hours to process one thousand photos . There still lacks a standardized method to analyze population size or individuals’ activities, through mark-recapture principle based on camera-traps.
False positives problem: Strong winds may trigger the camera to take pictures because the camera will film when it detects moving vegetation, and active filming may also occur because the camera or the post on which it is mounted has moved under the action of the wind.
False negative problem: There is usually an unknown number of animals walking into the camera trap vision but not captured by the camera, it leads to an underestimate of species richness and abundance. Also, The size of the animal is also one of the reasons why the recording accuracy is affected, the camera is usually more likely to miss small animals. Compared to spoor recording, this lower recording of camera-trap ranged from 22% in brown hyenas to 64% in civets. In Australia, larger animals are more likely to be underestimated using the camera trap, it may be because larger animals are much bigger in size than smaller animals in Australia and they do not have enough moving spaces around the camera vision. Another reason for the missing recording of large animals is the existence of camera triggering time. It is the time the animal gets into the monitoring range of the camera to the time the camera takes a phone. For the camera triggering during, large animals have more chance to leave the vision of the camera than smaller animals since they move faster.
Have effects on animal's behavior: Although the noise of current generated by a camera trap and the shutter sound when taking pictures are small and barely detectable by humans, they are often detectable by wild animals and cause some deviations in their behavior. In addition to sound, the camera's flash may attract the animal's attention.Some cameras use infrared light to assist in filming, which reduces the chance of being detected by animals, but cameras that use visible light to assist in filming are likely to attract the attention of animals and change their activity and movement range.
Tropical rainforests are home to half of the world's species, but with species going extinct at a rapid pace worldwide, it's difficult for conservationists to keep close tabs on the overall health of ecosystems, even in places where wildlife is protected. Researchers found that observational data from camera traps can help (Rice University, 2021).
Besides the case of tropical rainforests, the use of camera traps to estimate population size greatly helped towards the conservation strategy for the species, and more generally, the monitoring of other threatened populations and communities(Trolliet et al., 2013). This use of camera traps was highlighted in a study on the activity patterns of mammal communities in Indonesian rainforests (van Schaik et al., 1996).
Camera traps are also increasingly being used to study plant-animal interactions. Moreover, focal observations need to be conducted in the study of the seed dispersal capacity of a given plant species, to list the frugivore species interacting with the plants and to define the quantitative contribution of each species in the process of seed dispersal. Camera traps are revolutionary in this regard, as they allow the identification of diurnal, nocturnal, and shy species that would not be seen using other methods such as direct observation. (Trolliet et al., 2013). This is exemplified by the study of Nyiramana et al. (2011), who discovered that a species of rodent, the forest giant pouched rat Cricetomys emini (Wroughton, 1910), was responsible for the secondary dispersal of large seeds in an Afro-tropical forest.
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