Hissing like a snake: bird hisses are similar to snake hisses and prompt similar anxiety behavior in a mammalian model

The ABC-D of animal linguistics: are syntax and compositionality for real?

In several animal species, an alarm call (e.g. ABC notes in the Japanese tit Parus minor) can be immediately followed by a recruitment call (e.g. D notes) to yield a complex call that triggers a third behaviour, namely mobbing. This has been taken to be an argument for animal syntax and compositionality (i.e. the property by which the meaning of a complex expression depends on the meaning of its parts and the way they are put together). Several additional discoveries were made across species. First, in some cases, animals respond with mobbing to the order alarm-recruitment but not to the order recruitment-alarm. Second, animals sometimes respond similarly to functionally analogous heterospecific calls they have never heard before, and/or to artificial hybrid sequences made of conspecific and heterospecific calls in the same order, thus adding an argument for the productivity of the relevant rules. We consider the details of these arguments for animal syntax and compositionality and argue that, with one important exception (Japanese tit ABC-D sequences), they currently remain ambiguous: there are reasonable alternatives on which each call is a separate utterance and is interpreted as such ('trivial compositionality'). More generally, we propose that future studies should argue for animal syntax and compositionality by explicitly pitting the target theory against two deflationary analyses: the 'only one expression' hypothesis posits that there is no combination in the first place, for example just a simplex ABCD call; while the 'separate utterances' hypothesis posits that there are separate expressions (e.g. ABC and D), but that they form separate utterances and are neither syntactically nor semantically combined.

Regardless of personality, males show similar levels of plasticity in territory defense in a Neotropical poison frog

Animal personality traits are sometimes linked to an individual's degree of plasticity, with certain personality types being more plastic than others. In territorial species, consistently high levels of aggression might increase the risk of harmful fights, while consistently low aggression might lead to the loss of a territory. Consequently, reacting plastically with an appropriate territorial response should be beneficial to avoid these risks. An integrative investigation of both personality traits and plasticity can help us better understand the dynamics of aggressive interactions during male-male competition. Here, we used a free-ranging Neotropical poison frog population to investigate the role of plasticity in male territorial aggression towards intruders. We conducted repeated standardized territorial intrusion experiments mimicking frogs of different body sizes via playback calls with different peak frequencies. We found individual repeatability for the latency to reach and approach a simulated intruder and observed that both aggressive and less aggressive males decreased their level of aggression towards big intruders. However, our results do not support a correlation between personality and plasticity in the context of male territory defense during the breeding season. We discuss how such a correlation between personality and plasticity might be conditional on the costs and benefits across contexts.

Family before work: task reversion in workers of the red imported fire ant, Solenopsis invicta in the presence of brood

Among social insects, task allocation within its group members remains as one of the paramount pillars of social functionality. Division of labor in many eusocial insects is maintained by behavioral flexibility that can shift according to the needs of the colony they reside in. Workers typically, over time as they age, shift from intranidal nurses to extranidal foragers. If the needs of the colony change, either from the needs of the adults or the brood therein, workers shift their behavior in order to compensate for the need of a particular task to be done. This shift, either accelerating towards a behavior associated with an older worker, or regressing back into the nest, is not clearly understood in social insects outside of honeybees. In this study, evaluated how brood type affected the red imported fire ant, Solenopsis invicta, worker task reversion and acceleration. Through observation of worker behaviors performed over multiple time-points per day, we discovered that worker task reversion and acceleration does occur within this ant species. Furthermore, the type of brood influenced the rate at which this occurred, with larvae having the strongest effect of all types. Finally, there was a propensity for workers to maintain their new behavior throughout the experiment. This study shows that the needs of brood within a social insect colony can influence the behavior workers perform, reversing the age polyethism that is common among social insect species.

Extending the vibroscape to agroecosystems: investigating the influence of abiotic factors and monitoring insect vibrational signaling

Environmental conditions are crucial factors that influence communication systems and affect animal behavior. Research in the field of biotremology has improved our understanding of insect behavior, ecology, and evolution. However, the interactions between vibrational signaling and environmental factors are less studied, mainly because of technical issues faced in field trials. We therefore developed and tested an approach to investigate the effect of abiotic factors on insect vibrational signaling and explored its implementation as a monitoring tool for insect vibrational signals, using a vineyard as an agroecosystem model. Our results showed a significant decrease in insect signaling activity during unsuitable conditions of high temperature and wind velocity. We determined for the first time, the daily signaling pattern of the two insect pests, Scaphoideus titanus and Halyomorpha halys, in natural conditions. Biotremology techniques could be profitably used to monitor not only the presence of target pest species but also the biodiversity associated with vibrational signaling insects. In particular, the method implemented in this study could be used as a tool to compare the quality of cultivated areas under different management systems.

Season does not influence the response of great tits (Parus major) to allopatric mobbing calls

Many species of birds emit mobbing calls to recruit prey to join mobbing events. This anti-predator strategy often involves several species and, therefore, implies heterospecific communication. Some species of tit exhibit a sensitivity to allopatric mobbing calls, suggesting that heterospecific recognition is based on an innate component. To date, however, we have no information on whether the perception of allopatric calls varies with season, despite seasonality playing an important role in the perception of heterospecific call in some species. In this study, I investigate the responses of European great tits (Parus major) to the calls of a North American bird species, the black-capped chickadee (Poecile atricapillus), during two seasons: spring and in autumn (breeding and non-breeding seasons, respectively). Great tits approached the sound source during both seasons, with no significant difference in response between seasons. These findings indicate that season does not influence the response of birds to allopatric calls, and will help to shed light on the evolution of interspecific communication.

Effects of food, kinship, and density on the longevity of spiderlings

Cannibalism is a behavioral characteristic found in a wide variety of animal groups. Although the rates of cannibalism can vary from one group to another, studies indicate that the main factors contributing to an increase in the frequency of such behavior are the availability of food, population density, the behavior and availability of victims, and environmental stress. We carried out different laboratory experiments to assess whether different factors such as the presence or absence of food among siblings and non-siblings, and at different densities among conspecific and heterospecific individuals, affect longevity of recently emerged Brazilian brown recluse (Loxosceles intermedia Mello-Leitão, 1934) and Chilean recluse (Loxosceles laeta (Nicolet, 1849)) spiderlings during periods of starvation. The results revealed that the survivorship of L. laeta during starvation was significantly higher than that of L. intermedia and that the addition of conspecific individuals increased survival rates by 1.5- and 1.6-fold, respectively. The tolerance of conspecifics differed between the two species, and generally, cannibalism was not observed, probably due to the risk of predation and limited consumption by weakened spiders, which coincided with the continued availability of endogenous vitelline reserves, thus indicating that the use of these spiderlings as a food resource may act to regulate starvation in more resistant spiders. The greater longevity and conspecific tolerance of L. laeta may be important factors contributing to the establishment of large populations of this spider in restricted areas, whereas for L. intermedia, hunger probably functions as a trigger for dispersal.

Pathways linking female personality with reproductive success are trait- and year-specific

Personality (i.e., among-individual variation in average behavior) often covaries with fitness, but how such personality–fitness relationships come about is poorly understood. Here, we explore potential mechanisms by which two female personality traits (female–female aggression and female nest defense as manifested by hissing behavior) were linked with annual reproductive success in a population of great tits (Parus major), a socially monogamous species with biparental care. We hypothesized that personality-related differences in reproductive success result from variation in reproductive decision (lay date, brood size) and/or parental provisioning rates. Relative support for these mechanisms was evaluated using path analysis on data collected in two successive years. We reveal that larger broods were provisioned at a higher rate by both parents and that female, but not male, provisioning rate was involved in the trade-off between offspring number (brood size) and fledgling mass. Among-individual variation in female aggression, via its association with female provisioning rate, was negatively linked to fledgling mass (i.e., indirect effect), yet only in one of the study years. Male provisioning rate did not influence these relationships. In contrast, among-individual variation in hissing behavior was directly and negatively linked with fledgling mass in both years, via an underlying mechanism that remains to be identified (i.e., direct effect). Together, our findings emphasize that personality–fitness relationships may come about via different mechanisms across personality traits and/or years, thereby illustrating additional complexity in how selection might act on and maintain among-individual variation in behavioral phenotypes in the wild.

Does Liolaemus lemniscatus eavesdrop on the distress calls of the sympatric weeping lizard?

For a prey, its best ticket to stay alive is to get early and accurate information on predation risk and so, escape from predation at low cost. Some prey species have evolved the ability to eavesdrop signals intended for others, which contain information on predation risk. This is the case for the vocalizations produced by prey species when interacting with predators. Although primarily studied in birds and mammals, eavesdropping on vocal signals has been recorded in some lizard species. Here, we explored whether the lizard Liolaemus lemniscatus eavesdrops on the distress calls of its sympatric species, the Weeping lizard (L. chiliensis). Individuals of the Weeping lizard respond to these calls by displaying antipredator behaviours (i.e., reduced movement), and individuals of L. lemniscatus may potentially display similar defences if they decode the information contained in these calls. Our playback experiments showed that individuals of L. lemniscatus responded to the sound stimuli (distress calls and white noise), reducing their activity, but they did not discriminate between these two stimuli, suggesting that L. lemniscatus does not eavesdrop on the distress calls of its sympatric lizard species. We discuss some hypotheses to explain the lack of eavesdropping by L. lemniscatus on the Weeping lizard distress calls.

Behavioral snake mimicry in breeding tits

Many animals mimic the behavior or the appearance of venomous snakes. When humans or other potential predators place their hand near the nest of tits belonging to the family Paridae (and a few other species), the incubating female performs a hissing display that mimics the inhalation hiss of a viper or another snake. They hiss vigorously while lunging their head forward and shaking their wings and tail, repeating this behavior several times. The structure of the hiss in tits is similar to that of the inhalation hiss of a snake, providing evidence of significant convergence of the mimic toward the model. The behavior of individual females is repeatable among trials. Individuals that flew away from their nest box only performed the hissing display on 6% of later trials, when present at their box, whereas individuals that did not fly away hissed on 28% of occasions, consistent with great tits Parus major either cautiously flying away or staying put on their nest while actively defending it. Individuals that flew away produced fewer chicks than individuals that stayed and hissed. The hissing display was more common when snakes were more abundant: 1) When breeding late during the season; 2) when breeding at sites with more snakes; and 3) when breeding in subtropical and tropical China with a higher abundance of snakes than in Denmark with a lower abundance. The frequency of nest predation was higher in sites with no snakes, and the frequency of predation increased with decreasing frequency of hissing display. These findings are consistent with expectations for frequency-dependent selection acting on snake mimicry.