Ethology最新文献

Animals use colours, morphological structures and behaviour to advertise their dominance status and ability to obtain resources (Resource Holding Potential, RHP) in agonistic contexts with conspecifics. Dominance relationships are also known between species, although the interactions and the information used to assess the other species' RHP remain obscure and empirical evidence of interspecific recognition of status is hard to obtain. Using behavioural inference is particularly important when a species needs to assess the potential loss of fitness in terms of reproduction or survival (e.g., risk of damage or predation) that could be inflicted by another species acting as a predator, parasite or competitor. Our study shows for the first time the existence of interspecific recognition of status signals: Blue tits Cyanistes caeruleus (subordinate species) perceive Great tits Parus major (dominant species) as threats as hole-nesting competitors, and respond differently based on the size of the great tit's black tie stripe. Blue tits seemed to recognize the meaning of great tits' black ties because they were bolder when defending their nests against small-tie (less dominant) great tits than when repelling attacks by large-tie (more dominant) great tit males. Our results stress that behavioural inference can potentially be used to assess the meaning of status signals that presumably evolved in an intraspecific signalling context.

Individuals join mixed-species groups to gain benefits such as improved foraging and predator detection. Birds in the family Paridae often drive mixed-species flocking in North America, and these species can act as community informants for forest-wide eavesdropping networks. Although we know a great deal about how this communication functions in anti-predator contexts, less is known about how the vocalizations of members of these flocks may affect the foraging behavior of potential flockmates. In this study, we presented naturally occurring mixed-species flocks of chickadees, titmice, and nuthatches with one of four playback conditions: chickadee-only calls, nuthatch-only calls, calls of both species, and a silent control. We hypothesized that the flocks would be most responsive to playbacks that contained calls from more than one species. We also tested an alternative hypothesis that predicted that birds would be most responsive to the nuclear species within the flock (chickadees). We found that birds were more likely to arrive, and arrived more quickly, for the playbacks with calls from both species compared to playbacks of nuthatches alone or the silent control. Playbacks of chickadee calls alone attracted an intermediate number of birds, which did not differ significantly from the mixed-species flock condition, or the nuthatch call alone condition. Our hypotheses were not supported due to the lack of significant difference between the mixed-species playbacks and the chickadee playbacks. However, our findings do indicate that different species in these flocks can react differently to the calls of members of these flocks and that future studies may continue to find asymmetries in attraction to these different social signals.

Competition is at the heart of evolution (Darwin, 1859). Every individual to date has ancestors that were once more successful in passing their genes to the next generation than others. As a result, individuals should strive to outcompete others and perhaps to make their competitor's life even harder, for instance, by cheating on them. In such a competitive world, it might come as a surprise that across the phylogenetic tree individuals help others, including bacteria (Diggle et al., 2007), amoebae (Strassmann & Queller, 2011), insects (Field & Leadbeater, 2016), fishes (Frommen & Fischer, 2021), birds (Riehl, 2013), and our own species (Burton-Chellew et al., 2010) to name just a few examples.

Why would anyone help a potential rival? Theoretical work has shown that helping can lead to direct and indirect fitness benefits for the helper. For instance, helping kin might enable them to reproduce more often or to better care for their offspring. Because their offspring is genetically related to the helper, the helper gains indirect fitness benefits by transmitting shared genes to the succeeding generation (Hamilton, 1964). However, not all cooperation takes place between relatives, such as most of our own cooperative interactions occur between unrelated friends, workmates, or business partners. Here, indirect fitness gains cannot explain cooperation. However, helping others can also result in direct benefits, if previous recipients return the help in the future; this is called reciprocity (Trivers, 1971).

The significance of reciprocal cooperation to the functioning and stability of human societies has been recognised in many academic disciplines. Reciprocity is a widespread practice in our species (Bowles et al., 1997). It forms the basis for economic transaction and trade (Frank et al., 2018). As an ethical imperative, it is central to many world religions (Neusner & Chilton, 2008). Reciprocity is also a trait that emerges early in our ontogeny, as children at the age of 3 years reliably reciprocate (Warneken & Tomasello, 2013), suggesting evolutionary conservation (Warneken & Tomasello, 2009). Further, it has been described in human foragers (Jaeggi & Gurven, 2013), whose socio-ecology is probably closest to the conditions of early humans (Tooby & Cosmides, 2015).

Even though reciprocity seems ubiquitous and significant in our species, its proximate mechanisms and ultimate causes are still not well understood. The purpose of this special issue is to explore the principle of reciprocity in a diverse way by employing theoretical and empirical research as well as presenting observational and experimental evidence while featuring a multitude of species from invertebrates to humans. In the follo

Electric fish are good models in neuroethology as any behavior in electric fish involves both locomotor and electrical displays, which are experimentally accessible and controlled by well-known neural circuits. The agonistic behavior within the genus Gymnotus has been evaluated in Gymnotus carapo and Gymnotus omarorum, providing an advantageous model system to address comparative analyses. Gymnotus sylvius is a weakly electric fish which occurs in sympatry with G. omarorum in freshwater environments of Argentina. Here, we describe the agonistic behavior of G. sylvius in laboratory conditions. All dyads engaged in intense fights, with a latency to the first attack of 8 ± 7.8 s and a contest phase of 42.71 ± 31.7 s. Individual initiative in the first attack predicted contest outcome with no apparent influence of body weight asymmetry between contenders. Contenders did not escalate in their aggression during the short contest; in turn, subordinates tended to retreat in response to dominants' attacks. Submission and dominance were expressed by electric signals: dominants increased their basal electric organ discharge (EOD) rate after contest resolution, resulting in a persistent EOD rate rank. Subordinates also emitted chirps and offs during the contest and post-resolution phases without a clear temporal pattern. The agonistic behavior of G. sylvius presents some similarities with other species of the genus Gymnotus: EOD rank between dominants and subordinates, electric signals of submission, and the presence of attacks in the post-resolution phase. On the other hand, it also presents differences: a shorter evaluation phase in G. sylvius, initiative as a determinant of outcome, a higher attack rate of dominants in G. sylvius, a different temporal pattern of chirps, and different mechanisms to separate EOD rate of dominants and subordinates. These facts open a promising road to analyze the evolution of different neuroendocrine strategies, operating on homologous neural pathways, to command the same behavior.

Ballooning is a mechanism of aerial dispersal present in some groups of spiders. By releasing silken threads that are blown by the wind, spiders can travel long distances through the air. Aglaoctenus lagotis is a wolf spider that lives its entire life associated with a funnel-web, despite the wandering habit that characterizes species in this family. We can find two forms of the species in Uruguay, one of them a strict inhabitant of grasslands of Uruguay. The high habitat specificity and the spiderlings observed surrounding the maternal web suggest a low aerial dispersal capacity in this species. In this study, we tested whether A. lagotis spiderlings are capable of dispersing by ballooning. We conducted laboratory and field experiments during the day and night, to record the occurrence of ballooning and typical behaviours that precede ballooning. We recorded ballooning both in the laboratory and in the field, and it was more frequent during the day. Although it has been reported repeatedly in species from this family, we never observed the pre-ballooning tip-toeing behaviour in A. lagotis. Ballooning was preceded by dropping on dragline, considered a behaviour that could generate aerial dispersion of lesser distance than that generated by the tip-toeing. In this paper, we shall discuss the implications of this form of aerial dispersal, considering that the species analysed is a web wolf spider.

The bewildering courtship phenotypes of male birds of paradise (Paradisaedae) represent a classic example of sexual selection through mate choice. While the majority of sexual selection studies have focused on either mate choice or intrasexual competition, males across a variety of taxa adopt alternative mating tactics as additional means of obtaining fertilization when they are otherwise unable to. For example, across various polygynous birds, subordinate males engage in sneak copulations, which may offset the fitness costs of prolonged subordinate periods. Despite exhibiting strong mating skews and male delayed plumage maturation, reports of sneak copulation in the birds of paradise are exceedingly rare. After reviewing an extensive video collection of courtship interactions, we found examples of mountings by female-plumaged birds in three birds of paradise species: the Western parotia Parotia sefilata, Carola's parotia Parotia carolae, and the magnificent bird of paradise Cicinnurus magnificus. While homosexual mountings by females have been documented previously in Lawes' parotia P. lawesii, adult males in the magnificent bird of paradise violently attacked intruding female-plumaged birds attempting to mount receivers, suggesting that they may be immature males engaging in alternative mating tactics. Overall, the rare video footage described here is suggestive of two fascinating, yet unexplored phenomena in polygynous birds: alternative mating tactics and female homosexual behaviour.

“Helping those who help others” appears to be a widespread phenomenon. It is typically framed as indirect reciprocity in which individuals who are seen to help later receive returns from third parties. Here, I propose that helping can also be explained by the benefits that result from helping related helpers (where relatedness means sharing genes more than average, whether due to genealogy or some other mechanism). I test the functional roles of relatedness (or “kin selection”) and of reciprocity in explaining helping by varying the population structure and the number of interactions in individual-based simulations. First, with a unitary population in which individuals had a greater tendency to meet others of their own type, there were high levels of a discriminating strategy which helped other helpers. This can be explained by kin selection, in which helpers who help other helpers increase the payoff of their own strategy despite incurring a cost themselves. Introducing an “island population” structure reduced these indirect fitness benefits from helping, and this caused the frequency of the discriminating strategy to decrease markedly. Finally, increasing the number of interactions caused only a small increase in the level of the discriminating strategy (and thereby of helping helpers), consistent with indirect reciprocity (by means of the simplest strategy) being very weak. I argue that relatedness requires greater attention as an alternative to indirect reciprocity in explaining why individuals might help those who help others.

The ability of anuran larvae to efficiently locate food is essential for their growth and development, but little is known about the sensory modalities they use to find food. We experimentally assessed the role of visual and chemical cues in finding food in tadpoles of the invasive species Lithobates catesbeianus. In the two-choice experiment, using rectangular containers that offer visual and/or chemical food cues on opposite ends, tadpoles chose the side where the chemical cues of the food were present consistently. The visual cues alone showed an initial transient attraction of tadpoles, which disappeared after a few minutes, suggesting that tadpoles are potentially capable of seeing contrasting objects, at least, at a close range and in clear waters and daylight conditions. We also evaluated the foraging behaviour and the capability of tadpoles to find food in an open field experiment under two different lighting conditions: natural daylight and darkness. Results showed that tadpoles find food faster in dark conditions, confirming that chemical cues alone are sufficient for tadpoles of this species to find food. Moreover, the time spent feeding and the number of tadpoles simultaneously exploiting the food patch were greater in darkness suggesting that environments with low visibility conditions could favour the establishment of L. catesbeianus. Understanding the sensory modalities used by tadpoles of this invasive species to find food could help to understand the potential abilities to expand and establish in novel environments.

Oviposition site selection by parents is an important factor that affects offspring survival and parental fitness. The relative importance of sexes in oviposition site selection in anurans is rarely evaluated, especially in species with resource-defense mating systems, where males defend territory containing eventual oviposition sites before advertising for females. Using a phytotelm-breeding frog (Kurixalus eiffingeri) with male territoriality, we examined 310 bamboo stumps (potential for oviposition sites) to determine whether male and female choice of oviposition site based on physical characteristics (stump height, inner diameter, stump depth, water depth, and water volume). We found that males preferred a site with higher stumps that were deeper and contained more water, while females showed no preference for sites based on the characteristics observed. Although we do not exclude the possibility that K. eiffingeri female oviposition site selection can be relied on and/or correlates to male advertisement calls, this study is one of few studies to examine the role of both sexes in oviposition site selection simultaneously, and provides empirical evidence that oviposition site selection is primarily determined by males in an amphibian with a resource-defense mating system.

In animal fights, there are often size asymmetries between opponents. Although larger individuals typically dominate smaller ones, size is not the sole determining factor, as the competitors' motivation, aggressiveness, resource value, physiological characteristics, and strength also play crucial roles in fighting outcomes. In this study, we evaluated the influence of body size on dominance hierarchy and contest success during intra- and inter-specific contests in two fish species: the native mojarra of the Balsas basin Amphilophus istlanus and the invasive convict cichlid Amatitlania nigrofasciata. We used size-asymmetric males to carry out experimental contests. The number and type of aggressive behaviors, time to contest outcome, and dominant individual at the end of the contest were determined. In contests between two native mojarra, the smaller individual always lost. In contests between convict cichlids, the smaller contestants lost in all contests where size asymmetry was greater than 20%. In interspecific contests, the native mojarra performed more aggressive behaviors than the invasive convict cichlid and dominated convict cichlids despite a size disadvantage. This suggests that in terms of competition via interference, the native mojarra can counter the arrival of the invasive convict cichlid.