Ethology最新文献

Remaining immobile for an unpredictable period after being touched by a potential predator (post-contact immobility, PCI) may favor survival. However, the factors that determine variation in PCI duration are poorly understood. We tested whether PCI duration depends on the surrounding conspecific density (the selfish prey hypothesis) in the tropical antlion larvae Myrmeleon crudelis. These insects avoid predation by being immobile or burying themselves. The selfish prey hypothesis predicts a reduction in the PCI duration as conspecific density increases because this high density of conspecifics around can stimulate the redirection of the predator's interest in other nearby potential prey. In the field, we measured PCI and found that its duration was independent of the conspecific density. In the lab, we also measured the PCI of a subset of the same larvae in the absence of neighbors. Using a paired design, we found that PCI duration was lower in the lab in the absence of neighbors than in the field. Our results suggest that the antlion larvae did not follow the selfish prey hypothesis. We propose two alternative explanations. First, the larvae have a limited ability to detect neighbors in the field and keep up with the changing number of surrounding active pits. Second, burying may be more important than PCI as an antipredator strategy. In our lab experiment, larvae had a more accurate idea of the conspecific density around their pit because they explored the area. We propose that knowing the absence of conspecifics triggered a shorter PCI duration. Under a high predation risk (i.e., no other prey to which the predator would redirect its attention), the larvae select the unequivocal antipredator behavior of burying. This work illustrates the relevance of accurate information in deciding how to avoid predation, especially when prey can prioritize between alternative behaviors, with success varying between the contexts.

Intraspecific sexual communication, crucial in reproductive interactions, often involves the interchange of signals like vibrations, visual signals, and chemical compounds like sex chemical cues. Within the arachnids, solifuges (“camel spiders”) are an understudied group in terms of the detection of chemical compounds during mate searching and sexual interactions. In solifugids, the malleoli, chemoreceptor structures located on the ventral side of legs IV, are putative structures capable of capturing chemical signals. Our study focused on chemical male perception of female cues in Titanopuga salinarum (Ammotrechidae), examining associated behavioral modifications and the role of malleoli. We analyzed alterations in the motion pattern (activity pulse) and specific behaviors performed by males in association with female chemical stimuli. Using experimental arenas, we exposed males to female chemical cues stimuli similar to those available at the field. Stimuli comprised females (F) and cuticular extracts (CE), with corresponding controls. Males with intact malleoli (N = 26 with F, N = 20 with CE) were compared to those with malleoli removed (N = 21 with F, N = 17 with CE). We found partial evidence that males detect chemical cues of females deposited on the substrate. We observed no differences in the duration and number of the activity pulses spent in the zones with and without stimuli in any of the groups analyzed. However, the males exhibit significant changes in locomotion patterns in response to female chemical cues, suggesting a behavioral response to these stimuli. This finding suggests that the males of this species detect the female chemical cues and modify their behavior, and can quickly gather the necessary olfactory information where the stimulus is located. In addition, we found a possible condition-dependent regime for the detection of female cues by males, which would be expected from life-history characteristics of T. salinarum. Our findings prompt discussion from a sexual selection perspective, suggesting the importance of chemical communication in intraspecific interactions in this elusive but fascinating animal model.

Long matings are abundant in insects despite the range of the costs involved. The causes and consequences of the evolution of long mating remain an interesting problem for behavioural ecologists. We studied extraordinarily long mating that involves repeated intromissions interspersed with latent periods in the Parthenium beetle (Zygogramma bicolorata). We conducted a series of interrupted mating assays to examine the fitness consequences of different components of this curious mating behaviour. We tested multiple adaptive hypotheses concerning male fertility and competitive ability. We found that sperm transfer and fertility did not exhibit a linear increase with the number of intromissions. There was also no evidence of nutrient transfer by the males. Interestingly, our results showed that both sexes suffered a significant cost of long mating. Further, female remating behaviour was found to be modulated by the length of the previous mating. Additionally, males were observed performing a curious leg rubbing behaviour during the inter-intromission latent period, putatively serving as a copulatory courtship function that reduced female resistance to the continuance of mating. Therefore, we show that while the long mating may still serve a mate-guarding role, there are additional fitness effects of such behaviour that need careful consideration. Our study provides insights into the adaptive significance of long mating and its fitness consequences.

Several behaviors occur in the aftermath of within-group conflicts. These include spontaneous affiliation toward the victim from an uninvolved third party. When third-party affiliations reduce the stress of the victim, this behavior has been defined as consolation. Given the absence of previous reports, the objective of the present study was to evaluate the presence of third-party post-conflict affiliation when dogs (Canis lupus familiaris) observe their owners arguing. We carried out two studies varying the intensity and the duration of the dispute. Affiliative behaviors toward each of the owners were registered, as well as stress-related behaviors. Our findings support the existence of third-party affiliation from dogs toward their owners during and after a conflict between them, evidenced as higher rates of victim-directed affiliative behaviors in the experimental condition versus the control, in both studies. Moreover, dogs exhibited more stress-related behaviors in the experimental condition compared to the control, but only in the second study, which suggests these stimuli were experienced as aversive, even though they were not aimed at the dogs. In addition, in the second study dogs displayed aggressor-directed behaviors that could be interpreted as appeasement. Finally, there was no evidence that the level of the bond between the dog and each owner acts as a modulator of affiliative behavior. Further studies are required to expand our understanding of these abilities of dogs and its effects on the emotional state of the victim.

The chick-a-dee call of chickadees, tits, and titmice is a vocal system used in a wide range of social contexts by both sexes throughout the year and is one of the more structurally complicated vocal systems outside of human language. Relatively little is known about the chick-a-dee calls of mountain chickadees, Poecile gambeli, however. This is an important species for increasing our comparative understanding of variation in chick-a-dee calls as they are one of the chickadee species with the largest naturally occurring flock sizes. Flock size relates to the social complexity of flocks, and the social complexity hypothesis for communication predicts that individuals in more complex social groups should communicate with greater complexity than individuals in simpler social groups. Correlational and experimental evidence in support of the hypothesis has been found in the calls of a wide range of species, including Carolina chickadees, P. carolinensis. Here, we provide the first description of the variation in note composition and note-ordering rules in calls from mountain chickadee flocks in California and Colorado. California flocks were found to be significantly larger than Colorado flocks. Analysis of note-type usage and transition probabilities between note types found that calls of California birds were more complex than calls of Colorado birds, supporting a key prediction of the social complexity hypothesis for communication. We also found relatively high rates of reversals of note-ordering rules in mountain chickadee calls, which might help explain the complexity of the chick-a-dee calls of this species. Additionally, birds in flight produced calls with different note compositions when compared to perched birds. Generally, the note-type ordering and transition probabilities of calls of mountain chickadees seem comparable to other better-studied chickadee species, although their frequent note-type order rule reversals suggest potential syntax-like properties in this call system.

Wolf spiders can learn simple spatial navigation tasks. Previous studies have shown that the wolf spider Tigrosa helluo can use environmental edge features (reference frame landmarks) to learn the location of a dry target in flooded T-mazes; however, the relative importance of different types or numbers of landmark cues to spatial learning remains unknown. We used a modified open arena water maze and recorded the ability of adult female T. helluo to find a target reward (a dark and dry cup) among cups that were identical to the target but flooded. We measured variation in spatial learning by measuring time to target with no landmark (control), with a beacon (a landmark that is part of the target), with an associative cue (a landmark associated with a specific navigational action), and with both a beacon and an associative cue (N = 92 subjects, n = 23 per landmark cue treatment). For each treatment, we tested females for five trials each on four consecutive days, with the last trial on the fourth day having an altered target location, totaling 19 training trials and one reversal trial (1840 trials). We found that spiders took significantly less time to find the target over subsequent trials within a day and learned more quickly when landmark cues were present, but we found no difference in the type or number of landmark features in the meantime to target entrance. After learning a target location, moving the landmark significantly increased the mean time to target entrance in the combined beacon and associative cue treatment relative to other treatments. Our results indicate that wolf spiders use visual beacons and associative cue landmarks alone or in combination and that performance improves across trials when landmarks are present and deteriorates more when multiple landmarks are moved.