acta ethologica最新文献

Prey animals must balance the benefits of foraging in a particular area with their risk of predation in that area and often prioritize indirect cues to predation risk over direct cues of predators when making decisions about foraging under the risk of predation. Researchers using giving-up density (GUD) as a metric to assess perceived predation risk have found that it is affected by microhabitat, with certain animals willing to spend more time foraging (i.e., lower GUD) in relatively dense microhabitats and less time foraging (i.e., higher GUD) in relatively open microhabitats. This phenomenon has been attributed to those animals perceiving less predation risk when near or under shelter. However, the measurement has often confounded microhabitat density with distance from shelter in species without conspicuous dens. We measured GUD in foraging small mammals while experimentally manipulating microhabitat density and controlling for spatial location of the forager. Small mammals increased foraging (i.e., decreased GUD) as expected when we increased microhabitat density, but they did so despite those manipulations being randomly permuted spatially over the course of four rounds of data collection. Our results indicate that experimentally controlling for the potentially confounding effect of the forager’s distance to a safe location, such as dens, nests, or other shelters, did not remove the effect of microhabitat density on perceived predation risk. Thus, our results suggest that an animal’s perception of risk is likely mediated by both their location in their home range and the microhabitat at that location. We provide suggestions for further work.

Most triatomine bugs (Hemiptera: Reduviidae: Triatominae) are hematophagous, though Belminus species can live off of cockroach hemolymph to complete their life cycle. In this work, we described the fixed action pattern (FAP) employed by B. ferroae to identify, approach, and suck on a living cockroach. The FAP described here is composed of the following stereotyped behaviors: (1) visual and/or olfactory detection of the cockroach, (2) reaching, (3) cautious approach, (4) antennal exploration, (5) extension of the proboscis, (6) piercing to sedate, (7) walking away and waiting (postsedation behavior), (8) second cautious approach, (9) extension of the proboscis, (10) piercing to suck hemolymph. The FAP sequence observed suggests that Belminus bugs are not predators like the rest of reduviids (assassin bugs)—but are kleptophagous ectoparasites, since they do not attack and kill a prey but rather steal hemolymph from its invertebrate host. Based on these ethological observations, we propose kleptophagy as a trait that naturally groups the Belminus species into the Triatominae subfamily. In order to identify chemicals cues that could elicit such FAP, we examined the behavior of B. corredori, B. ferroae, and B. herreri in response to the cockroaches’ odor, fresh cockroach feces and fresh rodent wastes. The last two sources were tested based on the assumption that abundant chemicals near host refuges could serve as cues for host orientation. We found that the cockroach odor emanating from a box significantly attracted B. corredori and B. herreri in a still air olfactometer. The three Belminus species approached the captive cockroach after 1 h, but avoided to climb the box. Odors emanating from the cockroach feces attracted B. corredori and B. ferroae in a Y-olfactometer. Triatomines and their hosts have intimately shared the same refuge for millions of years; certain molecules occur across invertebrate and vertebrate refuges and are recurrent in human abodes, thus plausibly explaining how these bugs can readily switch to the domestic habitat, while keeping with their kleptophagous nature.

Across animal taxa, females of non-territorial species have potential opportunities to mate with multiple partners; hence, the primary mechanism available for males to ensure paternity is to guard the receptive female after copulation and repel other males. Hypothetically, mate-guarding is costly for males in terms of energy acquisition and increased risk of injury, and beneficial for females in terms of decreased harassment by other males and an increase in available foraging time. Here, we provide a detailed description of mating behavior and test these hypotheses in the Spix’s Whiptail (Ameivula ocellifera). Mating behavior is characterized by the following events: (1) a male courts a female in the entrance of her burrow; (2) if courtship is accepted by the female, a consensual copulation occurs; (3) after copulation the male accompanies the female during her daily activity, being aggressive towards other males; (4) when the female returns to the burrow, the companion male remains vigilant at the entrance and repels rival males. Besides the mate-guarding strategy, alternative mating tactics are adopted by some males that do not guard females after courtship and consensual copulation, while others try to copulate opportunistically with a female without prior courtship. Companion males spent more time vigilant, less time actively foraging, and captured less prey when compared to solitary males. Accompanied females captured prey in a similar proportion to solitary females but spent more time vigilant and less time foraging. Companion males won 100% of their interactions with rival males, chasing them away from the females. Accompanied females hence did not suffer harassment from other males when companion males were close. Our results evidence energetic costs of mate-guarding for males but not increased risk of injuries. By accepting mate-guarding, females do not appear to have energetic gains and lose the advantage of cryptic mate choice but can benefit from access to high-quality males and protection from harassment.

Birds can behave aggressively towards conspecifics to defend a territory and to compete for access to food and mates. The effects of phenotypes, such as sex and age, in aggressive behaviour have not yet been fully understood. Moreover, differences in aggression levels can reflect alternative behavioural strategies (i.e. proactive–reactive axis). We aimed to understand the relation between aggressive behaviour and different phenotypes (i.e. age, sex, body size) and between behaviours present in the proactive–reactive axis (i.e. aggression, exploration and fear). We studied the behaviour of a highly territorial species that shows sexual dimorphism, the Sardinian warbler (Sylvia melanocephala), using four behavioural tests: mirror, exploration, predation and tonic immobility. The tests measured respectively aggression, exploration and fear (the last two). Our results showed that the studied behaviours were not related to each other, suggesting an absence of the proactive–reactive axis. Only body size was found to predict aggressive behaviour, which might signal fighting ability in this species. Males and females did not differ in their aggression levels, suggesting that both sexes might play a role in territory defence. These results may reflect the importance of territorial defence in both sexes for species evolution.

Running wheels are frequently used to improve the welfare of captive animals, increase environmental enrichment, and, by doing so, reduce stereotypic behaviors. With the exception of a single investigation, all previous scientific literature investigating wheel running behavior has been based on animals in captive environments. This specific study reported that free-ranging animals in the Netherlands voluntary run in wheels placed in nature. Our study explores that same line of investigation, examining whether wild animals will voluntarily use running wheels in a natural area in Paraguay in comparison to the urban and semi-urban settings in the Netherlands. Of the 1857 small mammal visits we recorded, only two occasions showed evidence of what could be considered as wheel running behavior; over 100-fold fewer than previously reported. The potential reasons for the observed difference in wheel running activity, such as different species pool or seasonality, are discussed. The difference, however, is expected to be due to the much lower probability of Neotropical mammals in a remote natural site encountering man-made objects and experiencing urbanization-related behavioral patterns.

The patterns of affiliative interactions between subadult males are not well known. In female philopatric species, like long-tailed macaques, such relationships may be important in fully understanding socioecological contexts and processes. Subadult males have particularly important relationships with other males, often associated with the challenges of dispersal. This study assesses the patterns of affiliation among subadult males by comparing data from two allopatric populations. We collected over 400 hours of behavioral data on 27 total subadult male long-tailed macaques in Bali, Indonesia. We found that patterns of affiliation between subadult males measured by dyadic interaction rates and individual interaction rate composites varied between these populations. We observed significant variation across three domains of affiliative behavior: (1) resting in spatial proximity, (2) allogrooming, and (3) affiliative gesture exchanges. In each context, the subadult males of one population exhibited higher rates of affiliation than the other. We conclude patterns of affiliation between subadult males, and the importance of maintaining those relationships, respond to variation in socioecological contexts that may be population-specific rather than species-specific.

There is increasing evidence for species using information from heterospecifics to assess predation risk or habitat quality. Notably, a series of influential studies, using geometric symbols added to nest boxes, has shown that migratory flycatchers copy tits’ apparent nest-site preferences and settle in nest boxes bearing the same symbol as tits’ nest boxes. This “Selective Interspecific Information Use” hypothesis was recently challenged by the “Owner Aggression” hypothesis, stating that nest occupancy patterns are instead driven by tits aggressively excluding flycatchers from particular empty boxes to use as potential re-nesting sites after nest predation. Here, I propose the “Adaptive Interspecific Information Use” hypothesis, which outlines the predicted fitness benefits of nest-site copying or rejecting, and, importantly, provides an explanation for inconsistent experimental results to date. Indeed, neither previous hypotheses satisfactorily explains why flycatchers switch from copying to avoiding tits’ preferences, when tits’ clutch sizes are small or tits are at the laying stage. Adding to the recent debate, I show how predictable changes in nest predators’ search image and tits’ anti-predator behaviour may explain this variation. Indeed, incubating tit species aggressively defend their nest against nest predators, including by emitting snake-like vocalisations, which may generally deter predators from boxes bearing a tit nest symbol. By contrast, the undefended tit nests—which occur during laying before incubation starts, or potentially in individuals with small clutches—are easy prey that predators may specifically target. If predators cue on tit nests’ symbol, I therefore predict that, to reduce predation risk throughout the season, flycatchers may switch from avoiding the symbol of undefended tit nests to preferring the symbol of tits incubating large clutches. I propose experiments to test these predictions. Overall, considering nest-site copying in the landscape of fear framework, rather than invalidating the Selective Interspecific Information Use hypothesis, may be key to understand its evolution.

Mechanisms of conflict resolution, e.g. reconciliation, have been reported from a number of group-living animals, particularly primates. However, whether or not conflict resolution occurs in the cooperatively breeding callitrichids (marmosets and tamarins) remains a matter of debate. Captive studies provide contrasting evidence for the occurrence of reconciliation, and no evidence has been previously available for wild groups. Here, I present data on post-conflict behaviour in wild moustached tamarins, Saguinus mystax, which suggest that reconciliation occurs among wild callitrichids, too. However, reconciliation seems to occur very rarely among these primates, probably due to the generally peaceful nature of their social relations.

Multimodal signalling reinforces specific messages in communication. In gopher tortoises, similar to other reptilian species, visualization of conspecific and chemical exudates from the skin may serve as a multimodal display advertising information about conspecific species, sex, or individual qualities, but this has not been fully elucidated. For gopher tortoises, one such possible source of chemical cues could be secretions from seasonally enlarged mental glands (MG). Here, we used both sexes of gopher tortoises in a paired choice presentation of MG secretions vs. distilled (DI) water on resin tortoise models to assess visual presence with tortoise-specific secretions. We examined behaviours to treatments to examine if MG secretions are recognizable olfactory cues and if visual cues alone are sufficient to maintain social interactions using a simple visual presentation vs. a complex visual and olfactory presentation. Tortoises of both sexes spent more total time (p < 0.001) and performed a greater number of behaviours (p < 0.001) towards the MG-treated model, relative to the neutral control (DI-treated model), suggesting that olfactory MG secretions are also required, along with visual presence of a tortoise, to engage in social behaviours. Our results are among the first for this species suggesting that pheromone usage may drive social interactions in social behaviours.