Acoustic detection of flying vertebrate pest in fruit orchard: Case study of lorikeets

Australian fruit growers face huge losses due to the damage sustained from flying vertebrate pests such as birds and flying foxes. Growers spend hundreds of thousands of dollars in combating these pests due to the strict stipulations by the Department of Environment and Resource Management requiring all deterrent measures to be non-lethal. Some of the counter measures include canopy netting, tunnel netting, odour repellents, sounds, lights, scare guns, fruit bags and chemicals. These methods involve high capital and periodic maintenance costs and are rendered ineffective over a period of time since these pests are intelligent enough to find ways to overcome such obstacles. Thus, fruit growers are trying to find more effective methods to control the problem while trying to minimize their costs. Emerging trends in this area, particularly in the United States of America (USA), include the use of drones, automatic detection and warning systems, which in turn, can trigger a particular type of deterrent system and thereby protect crops. Infrared/laser scanning technologies has been found effective in detecting pests in small confined areas. Such technologies are usually customised to suit a particular geographical area and also the type of flying vertebrate pests being combated. This project is geared towards the development of a detection system which can effectively detect the presence of lorikeets in a lychee orchard in the Burnett region. Acoustic detection of bird species in the field environment is a challenging endeavour due to a complex mix of sound sources. Although there are several approaches to detect them, they are effective in only some particular situations. For example, infrared technology is effective in detecting pests in small confined area because of number of hardware components required while visual observation techniques require large amount of processing power. This shortcoming has prompted a study into the development of a sensor unit that can effectively detect flying vertebrate pests like lorikeets within the specified range under conditions typically found in lychee orchards. In this research, a new portable sensing device which uses a combination of acoustic sensors that can be used trigger a beacon or a sound whenever lorikeets are detected, was used. This sensor was tested during the lychee season of 2015/16 and has been found to be effective in detecting lorikeets up to 20 metres, with the detection rate ranging from 71% to 30% in the range of 2 metres to 12 metres. The detection system was customized to be effective in a specified range to detect lorikeet calls in lychee orchards. It is very cost effective and portable. Further, this is the first time that such a detection system has been used in a lychee orchard in the Wide Bay Burnett region and in wider Australia itself. These preliminary efforts possess great potential to explore the development of such devices to entail better crop management practices in the region.