Detection of Himalayan thar using a thermal infrared camera

The thermal characteristics of thar and their alpine habitat (including expanses of bare rock) were determined as a function of time throughout the night, by measurements from imagery acquired with a thermal video camera. Measurements were also made on thar in a farm environment, to determine the radiant temperature difference between their considerably hotter heads and cooler bodies. Thermal infrared (TIR) imaging for detection of thar in an alpine environment should not be attempted until about six hours after sunset, to allow time for rocks to cool sufficiently. Ideally, imaging should be carried out from a few hours before dawn until about one hour after sunrise. At these times, and under the conditions encountered in this study (thar at a distance such that pixel sizes of about 40 cm square were encountered), moving thar will be easily detected. It is highly probable that stationary thar in an alpine environment could be detected with a high degree of reliability, on the basis of radiant temperature alone, if pixel sizes equivalent to imaging areas of 20 cm square could be used. These pixel sizes approximate the dimensions of a thar head, which is relatively hot. Thar moving in an alpine environment can probably be unambiguously detected with current TIR cameras operating from an aircraft, if the aircraft disturbs the animals and causes them to run about. However, cameras available in New Zealand will only allow limited swath widths to be covered (c. 100 m). As the use of TIR imaging for operational detection of thar has much in common with detection of possums, it should be possible to share the development cost of any operational system for TIR imaging across a range of animal population estimation applications (probably also including such animals as chamois, deer, seals, albatross, etc.).