Patrolling the area, not ousting intruders, relates to reproductive success for territorial male Leon Springs pupfish, Cyprinodon bovinus

We considered the relationship between the benefits and costs of territorial defense in a wild population of the Leon Springs pupfish, Cyprinodon bovinus. We defined benefit as the number of eggs deposited on an artificial substratum placed within the defender’s territory. Costs included two defensive behaviors. First, males frequently “patrolled” their territories, swimming back-and-forth across their area. Second, males chased intruding Pecos gambusia (Gambusia nobilis) as well as small male and female conspecific C. bovinus from their territories. Both of these species prey on the territorial defenders’ eggs; additionally, small male C. bovinus will attempt to “steal” spawns from the territorial defender by spawning with females in the territory. Our analyses revealed that only patrol frequency was related to the reproductive benefit of the territory. Neither chases against gambusia nor conspecifics were predicted by egg numbers on the breeding substrata. We speculate that the frequency of patrolling is an indicator of territorial value and note the qualitative differences in chasing behavior against the different species of intruder.