Mutualistic relationship between Baird´s tapir Tapirus bairdii and brown basilisk Basiliscus basiliscus at Corcovado National Park, Costa Rica

Abstract

Some symbiotic relationships, like mutualism, benefit individuals of the species involved.  While there are documented instances of animals feeding on blood-feeding organisms that infest other vertebrates, cases of reptiles feeding on mammals are rare.  In this note, we present a case of a brown basilisk, Basiliscus basiliscus, feeding on the back of a Baird’s tapir, Tapirus bairdii, in Costa Rica.  Observations were conducted in Corcovado National Park, Costa Rica, where one of the authors (D. Paniagua) leads excursions with tourist groups.  During these excursions, brown basilisks have been observed on the backs of tapirs, hunting horseflies (Tabanidae) that land on them to feed on their blood.  At least 10 instances of this behavior between brown basilisk and tapirs were recorded.  These cases were observed more frequently on hot days and when there was sufficient water in puddles or other sources.  When tapirs rested in dry areas, the presence of brown basilisk was not observed.  This behavior aims to feed on female horseflies, which constantly harass tapirs by trying to land and feed on their blood.  Brown basilisk obtain food and help tapirs by reducing painful horsefly bites and the potential spread of diseases.  This mutualistic behavior had not been previously described for either of these 2 species.