CHOICE OF OVIPOSITION SITE IN PLEURODEMA BORELLII (LEPTODACTYLIDAE): IMPORTANCE OF CONSPECIFIC TADPOLE SIZE

Abstract

Selection should favor individuals that can assess the quality of their future offspring′s habitat in terms of its physical features and the presence of competitors or predators. Studies have shown that the presence of tadpoles at a site may deter adults from ovipositing there as the tadpoles may become competitors for resources or predators on the smaller conspecifics. Here I investigate whether tadpole size influences oviposition site selection in the leptodactylid Pleurodema borellii. The study took place at a location in northwestern Argentina, where this species naturally occurs, during five consecutive years. Six identically-sized pools were placed near an artificial pond allowing the frogs to breed without interference. Number of adults present at each pool and number of foam nests were recorded. Tadpoles were divided into three size categories (small, medium, and large) and were sampled twice a week. Adult P. borellii significantly chose two out of six of the pools to lay their eggs when small tadpoles were present, whereas they significantly avoided all the pools when medium and large tadpoles were present. The results suggest that an important factor in oviposition site selection in P. borellii is tadpole size. Females accepted a location with small tadpoles, possibly an indicator of a suitable breeding site, but they avoided locations with medium and large tadpoles that could become potential competitors as well as predators on the new progeny.