Impacts of harmonic radar tagging on the flight ability of male Bactrocera tryoni and Bactrocera jarvisi (Diptera, Tephritidae)

Understanding the movement dynamics of fruit flies is critical to both surveillance and control strategies with much of what is known coming from mark–release–recapture or flight mill studies. However, recent studies have demonstrated the feasibility of field-tracking fruit flies using harmonic radar (HR). In this study, the effects of attaching HR tags to Bactrocera tryoni and Bactrocera jarvisi were assessed in large indoor cages with both cultured and wild flies. The Queensland fruit fly, B. tryoni, is a major horticultural pest in the Northern Territory and east coast of Australia. Jarvis' fruit fly, B. jarvisi, is one of the lesser Australian fruit fly species, with a distribution in northern and eastern Australia. Three flight-associated behavioural parameters were recorded: (1) flight success (proportion of flies that flew), (2) time to flight (period from release to take-off) and (3) flight duration (period from take-off to landing). Untagged flies were more likely to fly and also took flight more quickly than tagged flies with this result holding across fly species and fly origin (wild or cultured). Similarly, wild flies were more likely to fly than cultured flies, but no differences were observed between the flight successes of the two fruit fly species. For all tagged flies, mean time to flight increased with successive flight trials, while untagged flies mean time to flight over time varied with species and fly origin. The effect of tagging on flight duration varied by species (tagged > untagged for B. tryoni, tagged < untagged for B. jarvisi) but not by fly origin with species. Together, these results quantify the negative effects of HR tagging on B. tryoni and B. jarvisi flight behaviours that should be taken into account when interpreting the biological relevance of HR tracking studies. These results also suggest that HR tracking of fruit flies would benefit from the further development of smaller and lighter tags.