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Abstract

Two different mate-locating tactics coexist within the California patch butterfly (Chlosyne californica): territorial defence of perch sites on hilltops and non-territorial patrolling of slopes and washes. Patrolling males were observed only during periods of high population density. At these times, some marked individuals used both tactics, indicating that they possessed the behavioural flexibility to practice either hilltop territoriality or downslope patrolling. Downslope patrolling was not simply a ‘making-the-best-of-a-bad-job’ option for males unable to secure territories. First, patrollers were not smaller on average than territorial males. Second, downslope patrollers typically became most numerous several hours after the hilltopping territorial males peaked in density. In the late morning and midday when patrollers predominated, temperatures were relatively high (perhaps facilitating patrolling flight) and foraging females (some of which were sexually receptive) were much more abundant. Patrolling is therefore likely to be a mate-locating supplement to hilltopping rather than an inferior substitute for it.