Sex-specific activity and movement in the threatened marsh fritillary Euphydryas aurinia

Abstract Sex-specific behaviour links environmental conditions to population processes, yet it is rarely quantified in threatened insects. Understanding how the sexes differ in activity and movement matters both for interpreting monitoring data and for habitat management. Here we used capture–mark–recapture data from a large population of the marsh fritillary ( Euphydryas aurinia ) on Gotland, Sweden, comprising 2,679 captures of 1,711 marked individuals over 27 survey days. For every capture we recorded whether the individual was settled, in flight or feeding, and matched it to the temperature recorded by a centrally placed, sun-exposed logger. We also measured the displacement between successive captures. The probability of being settled decreased with increasing temperature whereas the probability of flying increased, and we found no evidence that this response differed between the sexes. Males were nevertheless less likely to be settled and more likely to fly than females. Displacement between successive captures was similar in the two sexes, but increased with the interval between captures in males and not in females, so male space use expanded over the season while female displacement showed no such increase. Mark–recapture estimates further indicate that the strongly male-biased capture ratio overstates the bias in the population. Implications for insect conservation Monitoring and habitat assessment should record sex, because capture numbers partly reflect behaviour rather than abundance. The absence of a corresponding expansion in females suggests that conditions at a fine scale within occupied patches, and not patch occupancy alone, may matter for recruitment.