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Parental care is a common strategy among vertebrates to ensure successful reproduction. Anuran amphibians have evolved a remarkable diversity of reproductive methods including advanced levels of parental care. Among the most derived strategies are those of the Neotropical poison frogs (Dendrobatidae). These amphibians exhibit a wide array of behavioural traits such as egg guarding, larval transport by parental frogs and larval feeding with trophic (unfertilized) eggs. Ranitomeya variabilis from the upper Amazon basin in Peru deposits both eggs and tadpoles in phytotelmata. The exploitation of these small pools is advantageous as it lowers the risk of predation, but it is more costly because of limited resource availability. Additionally, poison frog larvae are often cannibalistic, so the identification and avoidance of conspecifics represents an adaptive behaviour for these amphibians. While studies have shown that poison frogs actively avoid depositing with conspecifics, the mechanism for assessing pool quality remains unknown. In field experiments, we found that parental R. variabilis frogs used chemical cues to recognize the presence of tadpoles in phytotelmata. Furthermore, they distinguished between cannibalistic and noncannibalistic tadpoles, a behaviour that supports the survival of their own offspring. 2011 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Multimodal signals convey information that can be detected by receivers using two or more sensory modalities. The information transmitted through secondary channels may be mostly useless, redundant, complementary, or essential. Although each option implies different evolutionary scenarios, the relative role of signal subcomponents in a secondary channel has rarely been tested. Anuran amphibians are known for their extensive use of auditory signals, but growing evidence suggests their common use of multimodal signals where the visual component represents the secondary channel. Territorial males of the nontoxic frog Allobates femoralis use bimodal (acoustic þ visual) signals to recognize conspecific intruders. We used playback experiments to test the relative importance of three visual subcomponents (body coloration, body size and body movement) in a multimodal signal to elicit agonistic reactions in males. The probability of attack was highly related to the movement and size of a dummy frog but very poorly related to dummy’s coloration. The results suggest that any body movement, and not only vocal sac movement, is a nonredundant component of a bimodal signal that probably modulates male aggression. Against our expectations, males readily attacked dummy frogs painted to mimic the cooccurring frog Ameerega trivittata as well as models lacking some of their own pattern’s subcomponents (white lines and yellow patches). Colourful frogs did not use body coloration as a visual cue for conspecific recognition. Both patterns recall the importance of carefully manipulating the availability of visual information in interpreting the origin and evolution of multimodal signals.

In the evolution of species recognition mechanisms, the differential reactions of receivers towards a signal may be as important as variation in the signal features. In many animals, the auditory system's most sensitive range often matches the dominant frequency range of the signals. The degree of spectral matching, however, can be modified by stimulus intensity and, therefore, patterns detected in the laboratory should ideally be confirmed by field experiments. Territorial males of the dart-poison frog, Epipedobates femoralis, approach vocally active conspecific intruders. Since phonotaxis (followed by fighting) affects male fitness, the auditory system is predicted to discriminate against heterospecific calls. We tested the role of spectral and temporal call features in call discrimination by conducting playback experiments in the field with synthetic calls. To study the effect of heterospecific interference on the male's phonotactic reaction, we measured signal parameters and signalling activity of four sympatric species. The highest probability of response coincided with the spectral and temporal features of the population's advertisement call and the probability of approach was matched to the average frequency of this call. In addition, the degree of matching was sensitive to the number of notes per call. The decrease in the probability of response, however, was steeper at lower than average frequencies, where the probability of heterospecific interference was highest. Our results suggest that under field conditions frequency tuning interacts with temporal call features in maximizing the detection of conspecific signals and reducing the probability of heterospecific interference.

The ability to associate environmental cues with valuable resources strongly increases the chances of finding them again, and thus memory often guides animal movement. For example, many temperate region amphibians show strong breeding site fidelity and will return to the same areas even after the ponds have been destroyed. In contrast, many tropical amphibians depend on exploitation of small, scattered and fluctuating resources such as ephemeral pools for reproduction. It remains unknown whether tropical amphibians rely on spatial memory for effective exploitation of their reproductive resources. Poison frogs (Dendrobatidae) routinely shuttle their tadpoles from terrestrial clutches to dispersed aquatic deposition sites. We investigated the role of spatial memory for relocating previously discovered deposition sites in an experimental population of the brilliant-thighed poison frog, Allobates femoralis, a species with predominantly male tadpole transport. We temporarily removed an array of artificial pools that served as the principal tadpole deposition resource for the population. In parallel, we set up an array of sham sites and sites containing conspecific tadpole odour cues. We then quantified the movement patterns and site preferences of tadpole-transporting males by intensive sampling of the area and tracking individual frogs. We found that tadpole-carrier movements were concentrated around the exact locations of removed pools and most individuals visited several removed pool sites. In addition, we found that tadpole-transporting frogs were attracted to novel sites that contained high concentrations of conspecific olfactory tadpole cues. Our results suggest that A. femoralis males rely heavily on spatial memory for efficient exploitation of multiple, widely dispersed deposition sites once they are discovered. Additionally, olfactory cues may facilitate the initial discovery of the new sites.

The ability to differentiate between one's own and foreign offspring ensures the exclusive allocation of costly parental care to only related progeny. The selective pressure to evolve offspring discrimination strategies is largely shaped by the likelihood and costs of offspring confusion. We hypothesize that males and females with different reproductive and spatial behaviours face different risks of confusing their own with others' offspring, and this should favour differential offspring discrimination strategies in the two sexes. In the brilliant-thighed poison frog, Allobates femoralis, males and females are highly polygamous, terrestrial clutches are laid in male territories and females abandon the clutch after oviposition. We investigated whether males and females differentiate between their own offspring and unrelated young, whether they use direct or indirect cues and whether the concurrent presence of their own clutch is essential to elicit parental behaviours. Males transported tadpoles regardless of location or parentage, but to a lesser extent in the absence of their own clutch. Females discriminated between clutches based on exact location and transported tadpoles only in the presence of their own clutch. This sex-specific selectivity of males and females during parental care reflects the differences in their respective costs of offspring confusion, resulting from differences in their spatial and reproductive behaviours.