Ethology最新文献

Although researchers have widely considered male song to influence female mate choice, it is less clear whether male song affects the likelihood of female encounters with males or their evaluation of potential mates. It is also unclear whether intra-sexual competition alters female reliance on male acoustic signals during mate selection. To investigate these questions, we conducted experimental studies on female mate choice in the Chinese cricket (Gryllus chinensis). We first demonstrated a significant correlation between the frequency of male courtship songs and calling songs and male body length. We then designed three experiments to manipulate males' ability to chirp. In each experiment, a group of female crickets (n = 2, 4, 6, and 8) chose between two males with known body and forewing lengths: in the first, one male could chirp while the other could not due to forewing removal; in the second, both males could chirp; and in the third, only the larger-bodied male had its forewings removed. In the first experiment, most females chose the male that could chirp. In the second, females preferred the larger-bodied male when competition was low, but selected the male with larger forewings when competition intensified. In the third experiment, significantly fewer females chose the larger-bodied male when we removed its forewings. These findings suggest that male acoustic behavior is used by females in choosing which males to approach and that intra-sexual competition among females modulates the influence of male calling song characteristics on female mate choice.

Understanding the costs and benefits of plural breeding, a reproductive strategy in which direct reproduction is shared by females in multi-female groups, requires that we examine the impact of males on females. The aim of this study was to examine potential additional fitness costs associated with male social organization to plurally breeding females in the caviomorph rodent, Octodon degus. Using a 10-year dataset, we used linear mixed model approaches to determine if male social organization was related to body mass, access to food resources, abundance of fleas, and glucocorticoid levels of females during offspring care. The body mass of adult females during lactation was negatively associated with the number of adult males per group and was marginally lower in groups with multiple males than in groups without males. Close examination of these trends suggests that the most biologically relevant difference is between groups with multiple males and groups without males. Male social organization did not impact female access to food, ectoparasitic flea loads, and FCM levels. Abundance of food and ectoparasite levels covaried with year of study and across females, while FCM levels varied across social groups examined. Altogether, these results suggest that the presence of male degus in multi-female groups has a small but negative effect on the condition of females. The lack of statistically significant relationships with other variables and untested conditions of the social environment and individual condition suggest that how males impact females is complex and condition-dependent.

Behavioral flexibility, the ability to adjust behavior in response to environmental changes, is crucial in extreme and novel urban environments. This study assessed behavioral flexibility in both immature (n = 11) and adult (n = 12) urban Kelp Gulls (Larus dominicanus). This is a generalist seabird highly associated with anthropogenic food resources, making it a valuable model to explore behavioral features that could promote this habit. We examined the relationship between a reversal learning task, which assessed the speed of acquisition and subsequent reversal of a stimulus–reward association, and a detour-reaching task, which tested inhibitory control by assessing the ability to suppress ineffective behaviors. The results showed no significant effect of age on either task. All individuals were able to control impulsive behaviors and reverse a previously acquired response. The reversal phase was more challenging than the acquisition phase, with individuals making more errors, especially regressive ones (i.e., inability to learn and maintain a new stimulus–reward association). Although the difference was not statistically significant, two clear patterns emerged: slower individuals during the acquisition made fewer errors and adapted more quickly during the reversal task and those who made more errors in the cylinder task also tended to make more errors in the reversal learning task. Our findings suggest that individuals learned a new color-reward association easier than they inhibited a previously learned response. This underscores the importance of inhibitory responses during the reversal phase. In conclusion, urban gulls exhibit notable cognitive abilities in adapting their behaviors and decision-making based on environmental cues, which could be crucial when exploiting diverse and dynamic food sources. Furthermore, behavioral flexibility was found to be independent of the age of the gulls. This may be because neophobia is low at all ages in this species; its effect is not strong enough to lead to a difference between adult and juvenile gulls.

Aggressive interactions are ubiquitous in the animal kingdom and are a key context favoring the evolution of familiar recognition. This cognitive ability has been widely reported in male crustaceans, including Pagurus hermit crabs. However, our understanding of female–female aggression and female cognitive ability remains relatively limited. Here, we describe the pattern of intrasexual aggression and assess the presence of familiar recognition in females of the hermit crab Pagurus middendorffii through two consecutive trials with 1-day's cohabitation. In the first trial, pairs of similar-sized females typically engaged in aggression using their appendages, though shell fights were rare. Following a 1-day's cohabitation, in the second trial, female behaviors did not differ between familiar (previously paired) females and unfamiliar (newly paired) females. As familiar recognition is beneficial in avoiding the associated costs of aggression, the lower frequency of energetically costly shell fights might explain the lack of evidence for familiar recognition in female P. middendorffii, as the benefits of recognizing opponents in such less intense interactions may be limited.

Defensive mutualisms occur in many ecosystems, but the impacts of environmental stressors on defensive services are unclear. Predation stress can create trophic cascades that influence relationships in lower trophic levels in food webs, including defensive mutualisms. Eusocial species often engage in defensive mutualisms, and stressors experienced by individuals within a colony may affect the behavior of the entire colony, such as cooperative and aggressive behaviors in defensive services. We tested whether experiencing a simulated bear attack (i.e., predation stress) affects mutualist defense behavior of a eusocial species, western thatch ants (Formica obscuripes), which defend aphids against predators in exchange for honeydew food. We exposed randomly selected thatch ant nests to a simulated bear attack to mimic natural bear predation (2022: n = 6 simulated bear attack, n = 22 not attacked; 2023: n = 8 simulated bear attack, n = 29 not attacked). We then exposed aphid-tending thatch ants to an aphid predator stimulus (e.g., lady beetle) approximately 5 weeks and 13 weeks after the simulated bear attack. Ants attacked the lady beetle more frequently during the second trial compared to the first trial, but this was more pronounced for ants whose colony did not experience the simulated bear attack. Year also interacted with trial time point to affect ants' behavior on the plants near aphid aggregations. Our results suggest that predation stress caused by the simulated bear attack may cause changes in ant defensive services that can last for months and which may be complicated by yearly differences in abiotic and biotic factors.