Summary
We conducted daily censuses on a marked population of the damselfly Calopteryx maculata for two complete breeding seasons to document the reproductive tactics of individual males. Overall, 78% of the 600 males studied defended territories and 14% of those territorial males were also observed engaged in sneaking behaviour on some days. When sneaking, males did not defend territories but attempted to steal females from other males' territories. Sneakers were usually previously successful territorial males who emerged early in the season and began sneaking relatively late in their lives (Fig. 2). Thus the adoption of sneaking was conditional and related to both male age and population density. We suggest that sneaking, in this species, is a "make the best of a bad situation" tactic adopted when intense male-male competition forced older males to abandon territoriality. Thus, sneaking allowed males with declining resource holding potential to prolong their reproductive careers after they were no longer able to hold a territory.
Methodology
Our study was conducted in June, July and August of 1984 and 1985 on a 1-km long, spring-fed stream that flows through woodland and meadow before it empties into Lake Opinicon in Frontenac County, Ontario. Since Calopteryx maculata is restricted to such streams, we were able to mark and census the entire population of adult males and females during both years. Each individual was netted as soon as it appeared on the stream and an identifying number was painted on its hindwing. Since we found none of our marked individuals during irregular sampling of the nearest adjacent populations, several kilometers distant, we assume that movement among populations was negligible (see also Waage 1972).