An understanding of trail camera detection zones helps with setting up more reliable camera placements. In this article, we break down the following:
Trail cameras use passive infrared sensors (PIR) to detect moving heat. The detection zone is the area in front of a trail camera’s PIR sensor where moving heat such as the body of an animal can trigger the camera. The detection of heat is important, as a trail camera only detecting movement would trigger every time vegetation moves in the wind.
The detection zone focuses on particular areas of a trail camera’s field of view. The size and shape of detection zones vary among different camera makes and models, as demonstrated by testing carried out by Bob Zak at Winterberry Wildlife. In some instances the detection zone is fully within the field of view, and in others it may extend outside the field of view, allowing the camera to activate before wildlife enters the scene. However, the latter can lead to an increase in false triggers. In the example image below, the NatureSpy Ursus detection zone is designed so the camera will trigger when an animal is more likely to be fully within the field of view.
Red area illustrates the detection zone within the field of view of the NatureSpy Ursus trail camera
A camera trap with a large detection zone and a quick, sensitive trigger is more likely to capture images consistently. These features are essential for a responsive and dependable detection circuit in a camera. Reliable detection circuits are one of the key benefits of good quality trail cameras, in addition to sharper images and robust housing.
Camera manufacturers describe detection range and flash range separately and, in some cases, they may not match up. For example, the Browning Recon Force Elite HP5 has a detection range of 30m and a flash range of 40m and the Bushnell Prime has a detection range of 25m and flash range of 30m. In practice, this means that animals are effectively illuminated in night-time images out to longer ranges, but it also means that trail cameras are more reliable and produce clearer images within commonly used ranges, such as 3 to 5 meters for many medium-large mammal species.
Browning Recon Force Elite HP5
Within a trail camera’s detection range, there are optimal focal ranges for reliably capturing high-quality images. Within these ranges, the animal will be fully within the field of view and close enough to show detail, such as the unique spots of a big cat or the feeding behaviours of a bird. Optimal ranges vary for different sizes of wildlife. For instance, for a wide range of medium to large mammals, a range of 3 to 5 meters between the camera and the focal point (e.g. a wildlife trail) will produce the clearest and most detailed images. This changes for smaller wildlife such as small mammals and birds, which often appear clearest within the 2.5 to 4 meter range. Many trail cameras begin to lose focus closer than about 2.5 meters to the subject.
Clear and detailed image of a leopard in the 3 to 5 meter range – Musekese Conservation
Measuring just 20cm long, the least weasel requires a closer camera setup in the 2.5 to 4 meter range
The performance and reliability of different trail camera makes and models can vary broadly. Understanding and quantifying these performance differences can be a key aspect of some research projects. For example, random encounter modelling is an approach commonly used to estimate species population density: This method requires researchers to accurately estimate the area monitored by a camera. Optimising camera trap methods for variables such as camera height and model can also affect the reliability of detection and individual animal identification. Learn more about choosing camera traps for scientific research here.
Installing a camera trap in a pilot test for mountain hare monitoring at Alladale Wilderness Reserve
Having a grasp of the technicalities of detection zones is helpful for establishing reliable trail camera setups. However, to effectively utilise this knowledge, it must be combined with hands-on experience gained by testing a trail camera model in specific scenarios. For example, try experimenting with different camera positions in a garden to find the most effective setup. For scientific research, pilot tests are also a useful way to gain a feel for the capability of different trail camera models before a full-scale study.
