Ross Alford and Jodi Rowley

Abstract

To gain information on the microhabitat use, home range and movement of a species, it is often necessary to remotely track individuals in the field. Radio telemetry is commonly used to track amphibians, but can only be used on relatively large individuals. Harmonic direction finding can be used to track smaller animals, but its effectiveness has not been fully evaluated. Tag attachment can alter the behaviour of amphibians, suggesting that data obtained using either technique may be unreliable. We investigated the effects of external tag attachment on behaviour in the laboratory by observing 12 frogs for five nights before and five nights after tag attachment, allowing one night to recover from handling. Tag attachment did not affect distance moved or number of times moved, indicating that the effects of tag attachment are unlikely to persist after the first night following attachment. We then compared harmonic direction finding and radio-telemetry using data collected in the field. We fitted rainforest stream frogs of three species with tags of either type, located them diurnally and nocturnally for approximately two weeks, and compared movement parameters between techniques. In the field, we obtained fewer fixes on frogs using harmonic direction finding, but measures of movement and habitat use did not differ significantly between techniques. Because radio telemetry makes it possible to locate animals more consistently, it should be preferred for animals large enough to carry radio tags. If harmonic direction finding is necessary, it can produce reliable data, particularly for relatively sedentary species.

Jodi J.L. Rowley and Ronald Altig

The Southeast Asian frog Limnonectes limborgi and the closely related L. hascheanus have been considered direct developers for almost 50 years. We report that rather than having direct development, L. limborgi has nidicolous development (= eggs oviposited terrestrially and larvae are free-living but nonfeeding) from large, nonpigmented eggs laid in a terrestrial nest constructed by the male. Thirteen nests were observed at four sites in Cambodia and Vietnam, five of which contained clutches of up to 15 eggs or tadpoles. Calling males were in attendance regardless of the presence of or developmental stage of their progeny. Large yolk reserves present as late as stage 37 and the lack of organic material in the gut indicate that these tadpoles do not feed. It is likely that L. hascheanus also has nidicolous development.

Jodi Rowley, Vinh Quang Dau, Huy Duc Hoang, Tao Thien Nguyen, Duong Thi Thuy Le and Ronald Altig

Gracixalus gracilipes, G. quangi, and G. supercornutus are small, morphologically and molecularly similar treefrogs with green blood from Vietnam, Laos and southern China. The breeding biologies, eggs, embryos and larvae of these three species are poorly known, and the male advertisement call of only G. quangi is known; this species has a hyperextended vocal repertoire. We provide new information on the breeding habitats, eggs, embryos and tadpoles of these three species and describe the calls of G. gracilipes and G. supercornutus. All three species deposit egg clumps on leaves overhanging shallow pools and puddles in forests. Like G. quangi, the calls of G. gracilipes and G. supercornutus are non-stereotypical, with individual calls highly variable in structure, duration, amplitude and frequency. Both calls are frequency modulated and have a dominant frequency of 4.1-4.7 kHz and many harmonics. The functional significance of these variations is unknown, and it is not known how common hyperextended call repertoires are within the genus.

Duong Thi Thuy Le, Jodi J.L. Rowley, Dao Thi Anh Tran and Huy Duc Hoang

Abstract

While deforestation is one of the greatest drivers of biodiversity loss, our understanding of the effects of habitat modification on species is limited. We investigated the diet of a forest-dwelling frog species, Morafka’s frog (Odorrana morafkai), in a highland forest in Vietnam in relation to habitat disturbance, sex and season. We surveyed the species at 45 sites in forest of varying disturbance and examined its diet using stomach flushing, estimating prey availability via trapping. We detected significantly fewer O. morafkai in highly disturbed habitats compared to moderately disturbed or non-disturbed habitats. We revealed that O. morafkai is a dietary generalist, identifying 28 prey types, primarily invertebrates. Prey composition, the number of prey items per stomach and prey volume per stomach did not vary between disturbance levels. Diet did not vary significantly between sexes, except that females had a higher prey volume. Prey composition in the species varied between seasons, with Coleoptera and Orthoptera dominating the diet in the rainy season and Lepidoptera in the dry season. The number of prey items per stomach and prey volume were significantly higher in the rainy season. There was a significant correlation between prey availability and diet composition. The low number of O. morafkai detected in highly disturbed habitats suggests that this habitat may not be optimal for the species, despite having a generalist feeding strategy and presumed high mobility. This study provides a window into the impact of an increasing threat, habitat disturbance, on forest-dependent amphibian species.