Natural histrory of Rhinella jimi (Anura; Bufonidae) : an invasive species in Fernando de Noronha

Author(s)

Julia Tolledo Santos

• Document type: Master's Dissertation
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2011-00-00

Examining board members

Renato Neves Feio; Paulo Christiano de Anchieta Garcia

• Advisor: Luís Felipe de Toledo Ramos Pereira

Abstract

The introduction of alien amphibian species has shown concern as it may contribute to the imbalance of native animal communities, causing environmental damage. These species feed on native species, breed rapidly due to the absence of predators and competitors, may also transmit diseases to native species and cause problems associated to hybridization with related species. Rhinella jimi is a Bufonidae of R. marina species group that was introduced in the archipelago of Fernando de Noronha near 120 years ago. This population presents a high prevalence of deformities, as almost 50% of adults have some external anomaly. About 20% of them present eye problems, some being completely blind. The main objective of this research was to study the natural history and reproductive biology of the population of Rhinella jimi from Fernando de Noronha, considering the high incidence of deformities among the individuals of this population. In the first chapter we described the tadpoles of R. jimi, necessary for the assessment of deformities evaluated in the second chapter. The third chapter was a study of the diet of this population, based on data from stomach contents complemented by isotopic composition analysis. In the fourth chapter we investigated the way that blind individuals locate and capture prey, as well as the possible consequences that vision problems may have on the physical conditions of animals. The fifth chapter is a study of reproduction, with descriptions of vocalizations and behaviors. The results showed a high prevalence of deformities among tadpoles, with more than half of them being deformed. Deformities in larval stage occur mainly in the oral disc and are connected to a shorter time foraging and a lower efficiency in the acquisition of food. Despite the absence of prey in the stomach of blind subjects, the study showed that these toads have a diet similar to the half blind individuals (with only one functional eye). Half blind individuals and individuals with no deformity (normal) had ants as the main prey, but Diplopoda was an important item in the diet of half blinds, while for normal individuals Coleoptera was more abundant. The feeding behavior differed between normal and blind individuals, with blind ones using tactile stimuli and a sit-and-wait foraging strategy, and normal ones using visual stimuli and active search foraging strategy. Vision problems also affect the body mass of the toads, as blind individuals had lower body mass. We observed the occurrence of sexual dimorphism in size, with females larger than males, and a trend of higher egg production and reproductive effort in normal individuals. We observed two reproductive strategies adopted by males, both blind and normal individuals, the vocalization and the active search for females. Deformed individuals (tadpoles and adults) present disadvantages in comparison to normal ones. In all cases half blind individuals presented intermediate patterns between normal and blind ones. The extent of disadvantages observed could imply in individual elimination in the natural range of this species. However, in the island the conditions may support their existence up to successful reproduction (AU)

• FAPESP's process: 09/03736-2 - Natural history of Rhinella jimi (Anura: Bufonidae): an invasive species in Fernando de Noronha
• Grantee: Julia Tolledo Santos
• Support Opportunities: Scholarships in Brazil - Master