Ethology and related disciplines, with a strong concentration on the behavior biology of humans and other animals

Use of ultraviolet cues in female mate preference in the sailfin molly, Poecilia latipinna  Abstract Photopigments that allow for ultraviolet (UV) vision occur in numerous fish species. In several species that also reflect short wavelengths, there is an indication that UV cues are important in forms of social signaling including mate choice. The sailfin molly, Poecilia latipinna, is closely related to species that use UV-reflective structures in mate selection, but it is unknown whether P. latipinna possess UV-reflective structures and whether the perceived presence or absence of these structures influences mating decisions. We detected prominent UV features on males and fewer, smaller reflective areas on females and then tested the role of these markings in mate preference. We focused on female preference, as male ornamentation and signals in the visible spectrum are known to influence female mating decisions. Using a two-choice paradigm, we exposed sexually receptive females to males whose visual appearance was manipulated by filters that either transmitted the full spectrum or blocked UV wavelengths. Female mollies significantly preferred males viewed under full spectrum, whereas male controls had no preference for females in UV-present or UV-absent light environments. While the ubiquity of these markings across both sexes may suggest additional roles for UV communication (i.e., shoaling), our results suggest that femaleP. latipinna take into account information transmitted in the UV markings when making visual mate choice decisions.

Chemical recognition in a snake–lizard predator–prey system Abstract In a predator–prey interaction, the fitnesses of the predator and the prey depend on their abilities to recognize each other, a process that may involve different sensory modalities. Squamate reptiles are highly dependent on chemical senses for such recognition, and here we explored the ability of a generalist saurophagous snake, Philodryas chamissonis, to discriminate scents of two congeneric and sympatric lizard prey species, Liolaemus nitidusand L. chiliensis. A generalist saurophagous snake might just be sensitive to lizard scents in general, and if so, no discrimination between prey species is expected. However, these lizards use different substrates; L. nitidusbasks on rocks, whereas L. chiliensis mainly basks on bushes and rarely on ground. The snake P. chamissonis basks on ground and rocks, and rarely on bushes. Therefore, if the rate of encounter affects the ability to recognize prey, we predict that P. chamissonis would show prey discrimination because scents of L. chiliensis may be encountered less frequently in its habitat. Results showed that the snake had a refined discrimination of lizard prey, reducing tongue flick rate and movements in response to scents from the common prey scents, L. nitidus. We also studied the ability of L. chiliensis to detect the snake and found that snake scents triggered a reduction in activity. The potential infrequent encounter between predator and prey may explain the asymmetric predator–prey recognition, as can be predicted from the “life-dinner” principle.

Timescale effects of 17α-ethinylestradiol on behavioral consistency in male threespine stickleback Abstract While the effects of 17α-ethinylestradiol (EE2) on male-typical behaviors are well studied, much less is known about the timing of these effects or the context in which these effects occur as most studies assay behavior at a single time point or in a single context. Additionally, exposure may affect behavior at levels beyond overall responsiveness, such as by altering behavioral consistency over time. Male threespine stickleback (Gasterosteus aculeatus) experienced three different contexts (single female, single male, paired female-male) over the course of 8 days, with an experimental group of males receiving EE2 after the first day. Exposure to EE2 disrupted responsiveness, behavioral consistency, and behavioral variation in all three social contexts. The timescale over which alterations in behavior occurred differed based on whether the conspecific was presented singly or paired with an opposite sex conspecific, stressing the importance of examining the effects of contaminants in multiple contexts.

Efficiency of antipredator training in captive-bred greater rheas reintroduced into the wild Abstract High post-release mortality of captive greater rheas reintroduced into the wild might be mitigated with antipredator training that helps released individuals recognize their predators. We analyzed whether captive-bred greater rheas conserve antipredator behavior, and evaluated the efficiency of antipredator training by recording survival after reintroduction into the wild. Training involved 12 individuals and consisted of a stimulus representing the natural predator (taxidermized puma) paired to an aversive stimulus (simulated capture). The control stimulus consisted of an innocuous object (chair) that was not paired to the aversive stimulus. Thirty and 60 days after the last training session, we presented the trained and control individuals (nine untrained individuals) to the predator stimulus, which was not paired to the aversive one. All of the greater rheas showed vigilant and running behaviors in the presence of the predator model. Trained individuals did not discriminate between a predator and a non-predator stimulus but they recognized the predator up to 2 months later. Survival was nil 8 months after release. However, only one individual was killed by a puma, whereas the remaining individuals died due to dog attack and poaching. Training did not increase survival of reintroduced greater rheas because of the failure to consider other potential predators, such as dogs or humans. Therefore, captive breeding might have affected greater rheas’ behavior by preventing them from recognizing man as a predator.

Geographical variation in male calls and the effect on female response in little penguins Abstract We investigated the variation in male advertising calls of two subspecies of little penguins (Eudyptula minor minor and Eudyptula minor iredalei), which live in two different regions within New Zealand. We found that the call frequency in both exhalation and inhalation phrases in male advertising calls differed between the two subspecies. Further, we conducted a reciprocal playback experiment to examine how females at the two geographical locations respond to the local and non-local male calls. Females tended to approach towards their regional calls, indicating that females recognize and might prefer their local male calls. Interestingly, E. minor iredalei females responded vocally to their local calls and took a longer time when approaching, while E. minor minor females did not use any vocalization during the approach and selected their local calls within a shorter time. However, given our limited sample size, we cannot exclude the possibility that these observed differences might be due to individual differences. Thus, further research is required to evaluate whether male mating signals and female responses to the male calls have diverged between the two subspecies.

Body size and group size of Cuban tree frog ( Osteopilus septentrionalis ) tadpoles influence their escape behaviour Abstract Tadpoles risk attack from both aquatic and aerial predators. We investigated how body size and group size influenced the behaviour of tadpoles before and during a predatory attack from above to test the predictions of the theoretical economic escape model. We examined escape (swimming) response of small and large Cuban tree frog (Osteopilus septentrionalis) tadpoles kept under three density treatments and predicted that increased group size, body size and depth in the water column would all reduce perceived risk and, therefore, escape responses to simulated predation. Compared with the lower density groups, tadpoles in higher density groups moved shorter distances, and many individuals did not even move away in response to being touched. Contrary to our predictions based on the economic escape model, smaller tadpoles (which should be more vulnerable to a greater suite of predators) were less reactive than larger tadpoles, and this result may reflect different costs of escape. Finally, although tadpoles might be exposed to a wider range of predator species (aerial as well as aquatic predators), we found no effect of initial depth on escape responses. In conclusion, it appears that the main benefit of increased group density in O. septentrionalis tadpoles is likely to be predator dilution, and that variation in densities of tadpoles influences the escape behaviour of individual tadpoles, regardless of tadpole size.

Defensive strategies of neonate nurse sharks, Ginglymostoma cirratum , in an oceanic archipelago of the Western Central Atlantic Abstract Two defensive tactics of neonates of nurse sharks, Ginglymostoma cirratum, are reported based on underwater observations. Described as “hiding behaviour” and “substrate resemblance”, the defensive strategies were categorized according to the predominant habitat in which the individuals were found and to the behaviour displayed by the sharks in the presence of the observer. In structurally more complex habitats with a wide availability of shelters, the preferential behaviour displayed by neonates is to hide inside holes or crevices. When in open areas deprived of refuges, neonates tend to resemble arborescent coverings as seaweed banks or colonies of octocorals, which allows the use of more exposed habitats without increasing the susceptibility of capture by predators. Both aspects are relevant for a better understanding of the behaviour of neonates of G. cirratum and have important implications for identifying important habitat in nursery areas, and also for the management of this vulnerable species off South America.

Stress hormone metabolites predict overwinter survival in yellow-bellied marmots Abstract Biological assays of stress, in particular noninvasive measures, are valuable tools for wildlife management. Chronic stress can have negative impacts on fitness outcomes, and an area of particular interest is if elevated baseline stress levels are predictive of survival outcomes. We examined the relationship between fecal glucocorticoid metabolites (FGMs) measured from samples collected during routine trapping and overwinter survival in a wild population of yellow-bellied marmots (Marmota flaviventris). In particular, we asked if elevated FGMs were associated with reduced survival probability. Both higher yearly FGM levels averaged over several months and higher late season FGM levels averaged over the several weeks before hibernation were associated with lower probability of survival. Additionally, there was an interaction between late-season FGM levels and body mass, such that the association between late-season FGMs and survival was much stronger in animals with lower body mass (i.e., in poorer condition). This study highlights the promise of using stress hormone metabolites, a noninvasive measure, for studying factors affecting survival in this and potentially other natural wildlife systems.

Socially mediated plasticity of chorusing behavior in the gladiator frog Hypsiboas rosenbergi  Abstract Competition for mates often occurs in social settings composed of many displaying males. While this poses some special challenges for communication, the proximity of other males may also provide information that chorus participants may use to adaptively adjust their calling behavior to the local level of competition. Conducting behavioral observations in natural choruses as well as playback experiments with focal males, I investigated socially mediated plasticity in the calling behavior of a neotropical gladiator frog, Hypsiboas rosenbergi. In natural choruses, male call rate was negatively correlated with the distance to the nearest calling neighbor, suggesting that the presence and distance of competing males influences call rate in this species. In a playback experiment that tested for the effect of the presence and competitiveness of rivals, H. rosenbergi males proved able to quickly notice changes in their acoustic environment and to respond to those changes in a graded fashion. As competition increased (either by increasing the number or attractiveness of the simulated rivals), males raised their calling rate; as competition was reduced, males lowered their calling rate. This indicates that males can perceive changes in their social environment and modify their calling behavior in ways that reflect the level of competition in the chorus. This socially mediated plasticity in calling behavior may help males to economize their energy reserves.

Tears stop the “pedophile” in mice: involvement of the vomeronasal system Abstract The Olfactory system serves more than just sensory function. The detection of chemosensory cues in the environment can trigger different emotional and social responses. A recent study described a juvenile mice pheromone that suppresses sexual behavior from other adult mice, through the activation of the vomeronasal-accessory olfactory system and the medial amygdala neural pathways.