Territorial defense is ineffective at protecting eggs from predation in the endangered Leon Springs pupfish...

In an experimental field study, we examined the effectiveness of territorial defense by male Leon Springs pupfish (Cyprinodon bovinus) in safeguarding eggs from predation. Both Pecos gambusia (Gambusia nobilis) and small C. bovinus intrude into territories to forage and will follow spawning pairs to eat newly deposited eggs. To test whether attacking and chasing these intruders would reduce the number of eggs that territorial males lost to predation, we excluded large males from different portions of their territories but still allowed the smaller fish to access those areas. Males lost many of their eggs to predators, but a similar number and proportion of eggs were lost to predation whether males could or could not defend those portions of the territory. We speculate that the haphazard distribution of egg laying by females may play a more important role than territorial defense in mitigating egg predation and discuss broader concerns of egg predation and habitat loss as threats to the survival of this endangered species.