Tracking the prey rather than the predator with GNSS

Global Navigation Satellite System (GNSS) technology has revolutionised the way 3-dimensional positions are determined on and above the Earth’s surface. GNSS-based positioning has become a vital tool for a wide range of applications in areas such as surveying, mapping, asset management, precision agriculture, engineering and construction. A lesser known application that has benefited immensely from the introduction of GNSS technology is animal tracking. For about 50 years, the tagging and tracking of animals has been invaluable in the quest to better understand animal behaviour and ecology (the study of the relationships that living organisms have with respect to each other and their natural environment). Monitoring animal populations is also necessary for conservation purposes, particularly in an era of human expansion into traditional animal habitats. Over the last two decades, the use of GNSS technology has been responsible for significant advances in this field. GNSS provides the ability to obtain accurate, regular and frequent estimates of the changing distributions of many rare animal species. However, employing conventional GNSS-based animal tracking methods to study drop bears and other tree-dwelling animals is extremely difficult due to their habitat. The dense tree canopy regularly causes extended periods of complete GNSS signal loss, and sensors are often damaged during attacks on prey. This paper outlines an alternative, indirect GNSS-based approach for tracking drop bears. Rather than attaching sensors to the animals themselves, the prey is tracked in order to map the population. A case study demonstrates that this method can effectively estimate the number and spatial distribution of drop bears in the area. It also provides valuable insights into the animal’s hunting behaviour.