Recent conservation efforts have shifted to include a more holistic approach to protection of ecosystems as we further recognize the interconnectedness of ecological community members. It is not commonly sufficient to focus on just one endangered species within recovery plans as we usually find multiple species in peril within threatened environments. Here, we continue a long-term effort to understand the complex behavioral dynamics of the Leon Springs pupfish ( Cyprinodon bovinus ) and the Pecos gambusia ( Gambusia nobilis ), both of which are classified as endangered species. The Leon Springs pupfish is critically endangered and only found in one spring system in Western Texas, USA. In addition to substantial habitat loss, these egg-laying, territorial fish may be suffering from small population sizes due to the constant predation of newly laid eggs by the generalist Pecos gambusia. Leon Springs pupfish continuously defend their small territories from invading gambusia, with long and short chases, appearing to attempt to remove the potential egg predators. From video recordings of these endangered fishes within their only natural habitat, we monitored behavioral interactions to determine if these aggressive chases by male pupfish are effective in actually removing gambusia from the territory for a substantial period of time in order to allow for successful egg deposit following spawning. The results found have implications for future recovery plans in our efforts to protect these endangered fishes.