Aggregation behaviour of Bufo maculatus tadpoles as an antipredator mechanism

Citation
M. Spieler et Ke. Linsenmair, Aggregation behaviour of Bufo maculatus tadpoles as an antipredator mechanism, ETHOLOGY, 105(8), 1999, pp. 665-686
Citations number
59
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Animal Sciences","Neurosciences & Behavoir
Journal title
ETHOLOGY
ISSN journal
0179-1613 → ACNP
Volume
105
Issue
8
Year of publication
1999
Pages
665 - 686
Database
ISI
SICI code
0179-1613(199908)105:8<665:ABOBMT>2.0.ZU;2-W
Abstract
Most anurans of the species-rich community of the Comoe National Park (Ivor y Coast) use ephemeral savannah ponds to spawn. Owing to the great risk of desiccation and the large number of predators, the mortality for tadpoles i s very high in these ponds. Therefore, colonization of other spawning habit ats might be highly advantageous. Such spawning sites are presented by the Comet river, which is characterized by frequent and unpredictable changes o f the water level. Only Bufo maculatus (Anura: Bufonidae) and one other buf onid species breed in small and shallow inlets and puddles created by the r ising and falling of the predator-rich Comet river. We observed that predat ory fish advanced to the spawning sites of the toads, when the water level rose. If the toad larvae were attacked by these predators, they formed dens e aggregations of up to several thousand individuals. These aggregations we re maintained for longer periods on one place at the river's edge where the y are inaccessible to the larger predators. In field experiments we ascerta ined that this aggregation behaviour in tadpoles was caused by a combinatio n of two stimuli: first, a chemical cue from injured tadpoles and second, a mechanical stimulus caused by rapid movements of aquatic predators. Initia l trials indicated that tadpoles aggregating at the bank were, however, dis advantaged compared with free-swimming larvae in having slower growth and a n increased risk of desiccation. This is presumably why aggregations broke up within 24 h after the predators had left these puddles, as the water lev el fell. At this point these tadpoles either spread out or formed loose swa rms near the bottom of the puddles. This swarming behaviour differed consid erably from that induced by aquatic predators.