Automatic video surveillance of wild animals in their natural surroundings allows a permanent record to be made of all activity within a pre-determined arena. The traditional method of direct observation, particularly when applied to group living animals, can lead to biases towards focal individuals. In addition, the proximity of a human observer may make the detailed study of extremely shy and/or nocturnal animals impossible.

We have developed a 12V DC battery powered, fully portable, weather-proof, monochrome, closed circuit television system. This is capable of filming automatically a selected arena of at least 10m by 10m for over 168 consecutive hours. Recording over such a long period is achieved using a time-lapse video recorder. Because of the continuous presence of the equipment at a site, habituation is more rapid than to a human observer. Without adjustment, the system can film in conditions of bright sunlight through to total darkness. Filming in the dark is achieved by exploiting the sensitivity of monochrome CCD cameras to infra-red (IR) light (and indeed one CCD chip has been designed especially for IR sensitivity). Arenas can easily be floodlit using infra-red light emitting diode (LED) arrays to provide sufficient illumination for good video filming, with the mammals being totally unaware of the IR light. The low power consumption of the LED arrays allows the system to operate without excessive battery requirements.

The system employs a combination of light switches, passive-infra-red (PIR) detectors (which trigger in the presence of animals), and timer devices to control the function and switching of lights and recording modes. A "vertical interval time code" (VITC) generator adds a computer readable time code to the tape as it is being recorded. This code is in real time - and therefore it is not affected by different time-lapse speeds of recording, and provides a resolution of up to 0.04 seconds. Therefore, given the correct computer software and hardware, analysis can be undertaken directly from the original tape. The system is based on "off the shelf" surveillance equipment and is designed to be compatible with all such technology, allowing for simple upgrading. Our experience is such that one person can set up and maintain at least six independent systems and so allow for simultaneous recording at multiple sites on a day-to-day basis. However, it is feasible to run the system from an alternative source, such as solar or wind generated power, therefore allowing operation in remote situations, when daily attendance is not feasible.

We discuss the function and assembly of standard, low-cost equipment, which has enabled us to study the detailed behaviour of the European Badger Meles meles [1] and the Red Fox Vulpes vulpes. We also explain some of the more expensive technology, required for specialised applications.

References

1. Stewart, P.D.; Ellwood, S.A.; Macdonald, D.W. (1997). Remote video-surveillance of wildlife - an introduction from experience with the European badger Meles meles. Mammal Review, 27, 185-204.