Flight initiation distance in dragonflies is species-specific, positively related to starting distance and sometimes body length

Predator escape behaviour is a critical component of dragonfly life history. Flight initiation distance is the distance at which escape commences, and is well studied in vertebrates, barely studied in invertebrates, and entirely unstudied in dragonflies. Here we test four principles regarding flight initiation distance as derived from studies of vertebrates to examine if they apply to dragonflies in Sri Lanka: (1) flight initiation distance is a species-specific trait; (2) flight initiation distance increases with starting distance (the distance at which the experimenter begins an approach); (3) larger individuals have longer flight initiation distances; and (4) flight initiation distance varies between the sexes in some species. We collected 105 flight initiation distances from 11 species (known sex and size). Flight initiation distances varied between species and positively with starting distance. In one of three data-rich species (n ≥ 10), flight initiation distance was positively associated with body length. Flight initiation distance did not vary with sex in our sample. Escape responses evoked by standardised human approaches represent a fruitful methodology to study dragonfly escape behaviour in the wild.