acta ethologica最新文献

Species have developed several defensive strategies for survival in response to predation pressures, including chemical, acoustic, visual, and behavioral mechanisms. Anurans serve as prey for numerous species, leading to the evolution of a diverse array of antipredator strategies. Among these strategies, acoustic emission defenses are categorized into distress calls, alarm calls, and warning calls. Although distress calls in frogs have been recognized to occur within the audible spectrum, the occurrence of ultrasound calls has been suggested for one species, but not yet confirmed. Based on our observations, we confirmed the presence of ultrasound distress calls emitted by an adult Haddadus binotatus. The distress call exhibited a high-pitched tone with decreasing frequency modulation and ultrasonic harmonics extending up to approximately 44 kHz. The presence of ultrasound frequencies in distress calls may confer advantages in deterring a broader range of predators. The use of broad-band screams synchronously with other behaviors, as raising the front of the body while arching the back and extreme mouth-gaping, intensified the defensive display, likely being more efficient in deterring predation. We observed similar behavioral repertoire for an adult Ischnocnema cf. henselii. Therefore, it could be widespread across individuals of other Brachycephaloidea genera as well.

Traffic noise is a pervasive pollutant that affects wildlife at individual and group levels through mechanisms such as disrupting communication, affecting antipredator strategy, and/or changing how they use space within a habitat. Urbanization is expanding rapidly—few places remain untouched by anthropogenic noise disturbance—so understanding the implications of noise on wildlife behavior is paramount to conservation efforts. We asked whether traffic noise could change space use and social network metrics in flocks of captive birds. Specifically, we quantified the effects of playbacks of traffic noise on individual sociality (weighted degree, number of social partners weighted by the frequency of interactions with those social partners) and flock clustering (global clustering coefficient, connectivity of neighbors). In this study, we recorded social interactions and space use of flocks of captive zebra finches (Taeniopygia guttata) before, during, and after an experimental traffic noise introduction in two treatments: high- and lower-amplitude noise. Our results demonstrated that individual sociality and flock clustering increased in response to the noise introduction in both high-amplitude and low-amplitude treatments. Additionally, birds in the high-amplitude treatment spent more time in the room with active playback during noise playback whereas birds in the lower-amplitude treatment decreased time spent in the room closest to the high-amplitude treatment. Increased social behavior in response to traffic noise could influence disease transmission, social learning, and mating dynamics. We suggest future studies explore the mechanisms driving increased social behavior in traffic noise, such as perceived predation risk, vigilance, and cross-sensory interference.

Squirrels and some corvids have successfully adapted to urban conditions. Their populations are often more abundant in city parks than in rural areas. These species may compete, especially in terms of food resources. We studied interactions between corvids (hooded crows and rooks) and red squirrels inhabiting urban park, mostly in relation to supplementary food utilisation in Poland. The study included the following: (a) feeding trials, when squirrels were offered hazelnuts and all stealing attempts by other animals were noted; (b) direct observations of groups of animals (at least one squirrel and one corvid species) with all behaviours being recorded. During the feeding trial, and with constant corvid presence, corvids tried to steal almost every third nut cached by squirrels. Regardless of the season, the share of nuts that corvids tried to steal was similar. When the feeding trial proceeded, more squirrels joined in order to obtain food. On the contrary, the presence of corvids seemed to refrain other corvids from joining the trial. The presence of a bird/squirrel audience did not result in more deceptive caches. During direct observations, squirrels interacted mostly with corvids, and less often with people or other squirrels. The most frequent interaction of squirrels with other animals was flight and chasing away; for corvids, it was chasing and following or attempting to steal food. Overall, we showed that corvids can be food competitors and kleptoparasites for red squirrels. Red squirrels, with whom people often have affinity relationships, benefited from direct supplementary feeding. Corvids, in turn, learnt to follow red squirrels to steal human-delivered nuts.

Two cyprinodontids, Garmanella pulchra and Cyprinodon artifrons, coexist in a small mangrove floodplain on the Yucatan Peninsula, enabling comparison of male territoriality in two species with similar social structure and resource needs. There were two contrasting situations, one where territorial males of G. pulchra were several times more abundant than those of C. artifrons and one where the reverse was true. In both situations, the roughly circular breeding territories were non-overlapping intraspecifically and showed complete overlap interspecifically. Territories of both species were several times smaller in the situation where they were numerically dominant. In that situation, the territories of G. pulchra were about twice as large as those of C. artifrons and males of both species showed higher conspecific aggression, lower heterospecific aggression, more reproductive activity, lower feeding rates, and lower percentages of body fat. In both situations of relative density, the percentage fat content was orders of magnitude greater in C. artifrons than in G. pulchra, potentially reflecting higher rates of territorial male turnover in the latter. Social behavior in the wild, described for the first time for both species, generally conforms to typical cyprinodontid themes for territorial and reproductive behavior. There was no evidence, in G. pulchra, of the courtship dance, nor the overt, male parental care described for Jordanella floridae, a species once considered a congener.

Understanding how heatwaves impact on different aspects of mating behaviour and fertility is getting increasingly important. In this context, laboratory fertility and mating experiments involving manipulation and exposure of insects to different thermal conditions are common procedures. To conduct such experiments practical methods such as dyes are needed for an easy, non-invasive discrimination of individuals. We report here a study measuring the effect of an extended heat stress applied to males on several parameters of mating behaviour and fertility of laboratory populations of Drosophila subobscura derived from two distinct European locations. We found highly detrimental effects of heatwave on mating behaviour—with longer (courtship and copulation) latencies and lower mating occurrence but no changes in mating duration—and fertility, with reduced fecundity and reproductive success. Furthermore, we also tested the efficacy of food dye as a marker for individual discrimination and mating occurrence. While food dye did not allow to infer the occurrence of a mating based on a transfer of coloration from male to female, it did not affect mating and fertility, attesting its utility has a method for discriminating individuals within mating experiments in the context of thermal studies. Importantly, despite the fact that the heatwave was only applied in males, we observed an impact on behaviour of females that mated with stressed males, by often refusing their nuptial feeding. This opens possibilities for further integrated research on the changes of female and male mating behaviour and fertility under different thermal scenarios.

Increased group size is predicted to dilute predation risk for individuals and increase predator detection at the group level. Individual vigilance tends to decrease with group size for many species. However, this pattern varies across species, context, space, and time. We explored the effects of group size on vigilance behaviors of white-tailed deer (Odocoileus virginianus) in relation to season, sex-age status, group composition, diminishing food returns, and intraspecific competition. We used classical behavioral observation methods and camera traps to study deer behavior. Sex-age class, season, intraspecific competition, and diminishing food returns interacted with group size to shape vigilance behaviors in deer. During spring, the effect of group size was essentially non-existent, and during winter, vigilance patterns exhibited a non-linear relationship with group size. Subadult deer benefited most in terms of increased foraging and decreased vigilance from the presence of 1–2 conspecifics, likely a maternal family group. This effect diminished in the presence of additional conspecifics (≥3), apparently as a function of contest competition. Individual deer spent less time at a site in areas with greater intraspecific abundance; however, in the presence of conspecifics, the relationship was reversed. Our research suggests that maternal family groups play an important seasonal role in vigilance behaviors of deer. Our study demonstrates the complex effects of group size in white-tailed deer. Group size effects are generally considered to be in response to changes in predation risk; however, our work supports a growing body of evidence that group size effects may also be influenced by intraspecific interactions.

Migratory shorebirds such as Calidris alba, C. fuscicollis, and Charadrius semipalmatus congregate in stopover areas like coastal wetlands to rest and feed, building up sufficient energy for their ongoing migration. To investigate the feeding ecology of these three shorebird species during their stopover, we conducted a comparative analysis of their feeding behavior and prey in Lagoa do Peixe National Park. We examined the feeding behavior using video recordings of 594 actively foraging individuals. Additionally, we determined the shorebirds' diet by analyzing 106 droppings collected from two areas within the park: the beach's intertidal zone and the lagoon's mudflats. The results highlighted that shorebird species showed marked differences in feeding strategies and prey captured during foraging. C. semipalmatus employed a visual-run-stop strategy with surface pecking, with no significant variations observed between the beach and the lagoon. The two Calidris species utilized a tactile-continuous hunting strategy, involving pecking and probing, with some variations observed between the beach and the lagoon. Multiple probing was mostly used on the beach, and single probing in the lagoon. The variation in probing behavior between the Calidris species appeared to be associated with differences in substrate type and food availability in the respective habitats they frequented. Additionally, our findings indicated that visual searching led to a more diverse prey selection, particularly in the lagoon. These differences in foraging strategies suggest that shorebird species can exploit the park's intertidal plains and trophic resources differently, emphasizing the importance of considering spatial and dietary variability in studying their foraging behavior.

Tool use by animals, traditionally studied mainly in captive primates due to its relevance to human evolution, has been investigated in both free-ranging and captive mammals. Here, I present a report on tree bark and branch use behaviours by a free-ranging Japanese marten (Martes melampus). The marten put its face in a water-filled container, looking for something, and then it proceeded to make a scooping motion with a bark held in its mouth. Subsequently, it picked up a branch with its mouth and tried to scoop something from the water with it. Upon inspecting the container approximately 2 weeks later, I found a larva belonging to the family Syrphidae. While it is unclear if the marten was trying to catch this larva, its behaviour resembled reach extension behaviour seen in chimpanzees. The use of bark or branches may provide an advantage by allowing access to objects in hard-to-reach positions.

In recent decades, reports on responses to death and dying individuals in non-human animals have been increasing. Here, we report the case of a striped hyena who refrained from eating a juvenile conspecific carcass in its territory. We inferred that the juvenile was an offspring of the individual. Although the hyena discovered the carcass several days before any other conspecific, other than maintaining vigilance over it and sniffing it repeatedly, it did not consume it; only an unfamiliar hyena did so. This is the first documentation of thanatological behavior in striped hyenas.

Annual killifish have an annual life cycle unique among vertebrates. Adults lay desiccation-resistant eggs in the soil of the temporary pools they inhabit. Courtship behavior of some Neotropical killifish consists of a series of displays performed by males and females that ends in the total or partial burial of the couple. However, little information exists on their reproductive isolation mechanisms, including a detailed analysis of courtship signals. In this study, we analyzed the courtship behavior of a Neotropical annual killifish (Austrolebias nigripinnis) within a comparative frame. The most frequent units in males were lateral (44%) and sigmoid displays (26%), where males exhibit morphological and color patterns to females. Females showed a high frequency (44%) of quiescence, suggesting that this unit may have an evaluative role during courtship. Behavioral units recognized in this species show some differences with other related species (i.e., Austrolebias affinis), mainly in frequency and duration, but also in sequence. Although the results of this work cannot determine if these differences constitute reproductive isolation mechanisms, it provides fundamental elements to try to establish kinship relationships and solve the complexity implicit in the definition of species.