Camera trapping

A haunted house? Strange noises that stop when you get there? Or maybe you’re wondering what is making that strange noise in the attic? Or what scary beast is roaming around your garden at night? What was it? A burglar looking for his next target? Maybe you have also wondered where the birds that are nesting on your property are? Or even what happens in the nearby forest when no humans are around? Camera Traps are exactly what you need!

« Camera Trapping »?

Beautiful one-off images of snow leopards have recently been published by the BBC and National Geographic. One-off, because it is difficult to stumble upon this animal. You might wonder how this is relevant to you. However, these animals are ghost-like, and not many people can boast about having seen one in nature. People that have filmed them were not there by chance; lots of clues, the work of biologists and testimonies of the locals have guided them to this point. Besides, they weren’t even there at all when the images were captured. Although, if these photos are the fruits of their labours, it is necessary to give credit where credit’s due.

The real heroes of the story are the Camera Traps. A practise, which is now democratised, sometimes rerouted into CCTV and relatively common when studying fauna. Without Camera Traps, these types of images, and many more, would be almost impossible (at least without a more invasive method).

Ecologists who want to start studying a wild animal in a given area often immediately find themselves faced with two challenges: that of knowing if the species is still present, and if so, how prosperous they are, and how many of them there are. Even if for bolder species, this problem can be solved by going to the field themselves, for other species things seem to be a lot more complicated. For this reason, for decades, a reliable evaluation of animal species has posed problems.

In response to this problem, a large variety of field methods and analytical approaches have been developed, and improved, of which include the use of Camera Traps, or “Remote Photography”.

Why use Camera Traps? Are they really miraculous?

Camera traps are photographic (or video) tools which are placed in nature, and are usually triggered when an animal, or a human, passes by, but sometimes they are on a timer. They are tools which are particularly useful because they are more than a simple image capture system. They need not only to be equipped with a camera but also with a system which detects when an animal is nearby, a fixation system or a support, and a system to store the date collected without losing it… Not to mention that the whole camera must be resistant to, or protected from, bad weather, or at least be autonomous enough to function for several weeks, or even months, without human intervention. Sometimes, it is even necessary to avoid or resist theft and vandalism.

A non-invasive tool to observe natural behaviours

The human desire to observe wild animals, without disturbing them, probably goes back to the prehistoric period. This was a time when hunter-gatherer tribes built blinds. In the 17th century, buccaneers had fun by climbing to the top of trees to discretely observe animals non-predatory defence behaviours. Our ability to observe animals in any context is reinforced by the development of photography and other, more recent, innovations like small portable batteries, electric light and digital equipment.

These technologies, which form the basis of Camera Trapping, allow us to make discrete and non-intrusive observations of a variety of wild animals, in a wide variety of habitats, at any time of day and even in the most difficult of conditions.

However, not only does Camera Trapping allow us to contemplate nature, it also allows us to study wild animals without invasive human intervention. Over these last decades, man’s interest in the wellbeing of animals has increased, pushing researchers to develop ethnic and non-intrusive sampling techniques. Besides, recent improvements in this technology have allowed us to answer questions that it was difficult to respond to beforehand. The use of Camera Trapping to study and follow wild fauna has therefore recently considerably increased. This is a trend that is likely to continue, thanks to improvements in the power and performance of these devices combined with a reduction in their cost.

Since the pioneering photos captured by huge cameras powered by wires, technological advances in infrared sensors and digital technology have now provided us with non-invasive and profitable ways to detect and obtain reliable and precise data on animals which would otherwise have been unobtainable, and to have this data confirmed by more than one specialist. Also, the use of Camera Traps in this field has, uncontestably, improved our understanding of their ecological relationship, and more recently, of their dynamic and population. From urban parks to the most remote forests, from very common to very rare spaces, elusive and often enigmatic, there now exists numerous studies and monitoring which implicate the use of these Camera Traps.

Numerous Ecological Applications

The enthusiasm for the use of this emerging technology in ecology has brought about the creation of “Camera Trapping Experts”, who have learnt a lot from their mistakes. Ecologists are now reviewing specific trap systems and discussing the most common errors made in the field as well as the technological aspects of different traps.

Currently, camera traps are used in the conservation and management of species, at various stages of their projects. Faced with uncertainty, some decision-makers respond with paralysis and call for an attempt to obtain “more information” whilst others decide to act despite this uncertainty, even if they make bad choices.

Some people speak about partial observability to express the impossibility of managers observing and estimating the parameters describing the state of nature. Partial observability leads to this uncertainty. In this context, before contemplating these decision-making processes aiming to push a population, a species or an ecosystem towards (or keeping this in) a desirable state (or far from undesirable situations), Camera Traps are part of the arsenal to assess its current state. Therefore, these Camera Traps push towards choosing an adequate course of action to accomplish these objectives and solve problems.

Once the objectives have been clarified, the camera traps can again help managers in their management and follow-up actions by serving as a base and source of information.

Camera Trapping is also useful in the study of animal behaviour. Before the arrival of the radio telemetry in the 1960s, direct observation was essentially the only way in which behavioural ecologists and ethologists studied animal behaviour. Even today, direct observation remains very widely used. Camera Traps are relatively recent tools in the arsenal of ethologists. Like radio transmitters, Camera Trapping has many advantages and improves certain interesting aspects of direct observation. The casing, the noise, and sometimes the flash associated with certain camera traps can, of course, modify animal behaviour, but this probably causes less of a disturbance than the physical presence of a researcher spying on the animal. Ecologists use this tool to quantify the temporal and spatial activity of the animals they study, or to target specific behaviour.

By contrast, the photographs do not always allow the ecologists to obtain precise information, since the animals actions can not necessarily be determined by a single photograph or video. This tool is also used for many other subjects linked to animal behaviour. For example, studying seasonal rhythms, or nest predation, the supply of provisions (the composition of food, the compromise between food and the monitoring of the environment…), distribution, social organisation, the use of habitats or passageways, the observation of behaviour within nests and burrows, reproduction…

In ecology, camera traps are used to estimate the abundance of species when it is possible to identify the animals individually via photographs.


Photos of a tiger taken by Camera Trapping. These photos allow identifications and determinations of the gender and age category to be made. Both photos are taken by the same trap, in Nagarahole, India, by Ullas Karanth, Wildlife Conservation Society.


Nowadays, Camera Trapping encompasses a wide range of equipment and uses. This wide range of uses allows researchers to generate an abundance of new information. The possibility to establish standardised methods leads some people to consider Camera Traps as an important element in projects monitoring biodiversity.

All of these uses are well known by ecologists nowadays. Even coroners and forensic scientists have begun to use them in order to determine what happened to a human body left in the woods. Lauren Meckel, Chloe McDanel and Daniel Wescott, from the Forensic Anthropology Centre of Texas State University, United States, were able to discover that deer can eat parts of a human carcass.


Photo of a deer eating a human bone, taken on 5th January 2015, on the grounds of the Forensic Anthropology Centre of Texas State University. The other photo shows a human rib after being eaten by one or two deer.


The disadvantages of Camera Traps

On the other hand, the disadvantages of the use of Camera Trapping systems in ecology are less well known. These disadvantages have not received as much attention, even though experienced researchers have surely noticed them.

The first of these problems is the loss of data due to problems with the equipment. Some systems have received much praise, which has subsequently been offset by testimonies of bad experiences attributed to their use in a tropical context. However, the same type of bad experience has also been noted in other contexts.

These specific problems include both a malfunction of the trigger mechanism (when the camera doesn’t record anything), and multiple photographs which show no animals. The malfunctions of the device can be a nightmare for biologists who work with this tool in remote regions as they take time to notice the problem. For example, if they only visit their Camera Traps once a month to collect the data and replace the batteries, and if the images cannot be viewed directly in the field, they lose two months of data before they can even begin to try and solve the problem.

It must also be noted that numerous factors influence the performance of Camera Traps. Their poor performance is usually caused by the combination of climate, inexperience, and the lack of user skills, unique terrain conditions (such as an animal that breaks the equipment), and poorly designed equipment. All this doesn’t take into consideration the specific characteristics of the camera model (sensitivity, detection zone…). Some of these factors can be controlled, but others cannot. So, even though this tool has become popular in the scientific community and even beyond, there are still many cases of failure reported by the ecologists who use them.

For this reason, it is necessary to anticipate the majority of these problems by preparing and tracking, by reading other studies, by consulting experts or by conducting tests yourself. It is also important to understand both the problems and the potential of these Camera Traps and to choose those which best fit the intended use. Hence the question entitling the next article!

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