Title

Parental Care and Tadpole Schooling in the Neotropical Frog, Leptodactylus insularum

Date of Completion

January 2011

Keywords

Biology, Ecology|Biology, Evolution and Development

Degree

Ph.D.

Abstract

The Neotropical frog Leptodactylus insularum exhibits a rare combination of social behaviors—maternal care and tadpole schooling. Previous studies speculated on the adaptive function of maternal care, but had not examined it in detail. I performed field observations and predation trials to determine the benefit of maternal care and the cost of schooling on tadpole anti-predator behavior. Females of the Panamanian frog Leptodactylus insularum guard their nests and schools of tadpoles, communicate with their schools using body-pumping movements, lead them around the swamps, and aggressively defend their offspring against predators. Attending mothers improved tadpole survival; attended schools survived almost twice as long as deserted schools. Out of 66 schools monitored in two seasons, only eight schools survived until metamorphosis, and all received maternal care. The presence of an attending female had no effect on the speed of tadpole development or growth rates, however. Females do not appear to be leading schools to new foraging patches. Instead, females may be leading tadpoles in order to avoid rare, but potentially devastating moments, such as vertebrate predation or desiccation. Tadpoles develop in ephemeral environments and are susceptible to desiccation. In response, they actively forage throughout development and achieve metamorphosis in only 16 days. However, the activity of tadpoles within the school is very conspicuous and may increase vulnerability to predation. To determine if schooling tadpoles are more vulnerable to predation, I compared predator encounter rates, escape speeds, and spatial avoidance of predators by two schooling and solitary species of tadpoles (L. insularum and Physalaemus pustulosus, respectively) that develop in ephemeral ponds. Individual L. insularum tadpoles were more active, encountered more predators, and experienced higher mortality rates than did tadpoles of P. pustulosus. However, vulnerability due to activity was predator-specific; higher activity rates were associated with increased mortality only in the presence of aeschnids, which rely on movement for hunting. ^

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