Survey Methods: An Overview
Radio-telemetry is a critical aid for gathering detailed information on habitat use or preferences, movement patterns, home range utilization, and social interactions, especially in animals that cannot be readily observed like most solitary or nocturnal carnivores. Traditional VHF (Very High Frequency) radio collars, first applied in the 1960s are being replaced by more sophisticated GPS (Geographic Positioning System) or satellite-linked systems able to track and store movements on a daily or hourly basis for an entire year or more (see, for example, our work in Mongolia). By matching the animal’s GPS coordinates with a habitat map compiled using satellite images or aerial photographs and ground-truthing, the researcher is able to determine what habitat features or conditions are most important with respect to feeding, resting or breeding. Movements over time indicate how much space the animal requires and whether or not this is shared with other individuals. Conservation plans can be more responsive to these needs by incorporating these and other elements. And by tracking one or more known snow leopards on the ground, one is more likely to detect other untagged individuals using the same area. Along with data on average home range size and prey densities, scientists are able to better estimate snow leopard population size (number of cats present in survey area) and density (number of cats per unit area, typically expressed as 100 kilometers square).
- Has the potential of generating intensive data on a wide variety of topics
- essential approach for any species about which little ecological or behavioral information is available
- Radio-tagging tends to be invasive, since animals must be trapped, immobilized and then fitted with a radio-collar
- requires highly trained biologists able to spend long periods of time in the field to catch and monitor collared individuals
- high or very high cost due to equipment and manpower needs (up to 10x other techniques)
- radio-collars are notoriously prone to failure, while VHF-tagged snow leopards often move beyond tracking range, thus precluding data collection