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.
The affective state of animals, that is, their mood and emotions, is altered by stressful (negative) or enriching (positive) experiences. In turn, the affective state influences decision making, thereby helping animals when coping with environmental challenges and opportunities. However, it is largely unknown how social experiences modulate the affective state. Here, we performed a judgement bias test to study the effects of rearing group-size and experimentally assigned current rank on the affective state of the cooperatively-breeding cichlid fish Neolamprologus pulcher. To assess affective state, we developed and validated a judgement bias test for this species. Fish learned to discriminate between a positive and a negative stimulus as shown by different latencies to approach the stimulus. Furthermore, the response curves to the stimuli conformed to the ones expected in judgement bias tests: fish showed an intermediate latency to approach an ambiguous stimulus, which significantly differed from the latencies to approach the positive and the negative stimulus. Unexpectedly, there were no significant effects of rearing group size and current social rank on the affective state of N. pulcher, despite known effects of these two social parameters on behaviours and physiology of this species. This may mean that observed behavioural and physiological differences in the treatment environments do not allow valid predictions about the affective state elicited by these environments. Alternatively, it may need more socioecologically relevant testing paradigms when evaluating the valence of social environments.
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.
Males often employ different reproductive tactics to gain access to females based on their condition and the surrounding environment. Predation risk is expected to have a significant influence on the frequencies of alternative reproductive tactics because these tactics typically differ in activity, which may result in differences in predation rate. In theory, such predation effects can explain the evolution as well as the maintenance of alternative reproductive tactics. Yet, there is little experimental work testing how predation risk affects alternative reproductive tactics. To assess such effects of predation, here we report on experiments with the two-spotted spider mite Tetranychus urticae. The two-spotted spider mite is a small arthropod herbivore species, in which males exhibit precopulatory mate guarding by mounting preadult moulting (and hence immobile) females. Two reproductive tactics are observed during mate guarding: The fighting tactic involves attacking other males to drive them away, while the sneaking tactic involves mounting the females and remaining motionless, even when contacted by other males. In this study, we exposed pairs of male and female spider mites to a predatory mite (Phytoseiulus persimilis) and observed their survival and male response to a predator when females were guarded by either fighter or sneaker males. We found that predation risk was not significantly different between fighter and sneaker males. However, the immobile females were more often preyed upon when guarded by sneakers than when guarded by fighters. We attribute this indirect effect of predation risk to the sneakers continuing to mount females even when a predator is nearby.
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.
Predatory interactions result in strong selection pressures acting on multiple aspects of animal behaviour. Anti-predator strategies are therefore common in most animals, typically signalling at various stages of a predation event. Many species of caprimulgids perform conspicuous anti-predator displays, including stereotyped behaviours and vocal signals. Here, we described distress calls of red-necked nightjars (Caprimulgus ruficollis), produced when birds are trapped and unable to escape during a predatory interaction. Distress calls are harsh, low-frequency guttural vocalisations with irregular amplitude modulations. The age and sex of birds partially explained the acoustic variation observed, whereas size-related morphological features were poor predictors of the acoustic structure. Age-sex differences in distress calls may respond to physiological constraints associated with sexual dimorphism and/or developmental variation. Alternatively, directional selection associated with differential predation risk on each age-sex class may have resulted in the observed differences in distress calls. The extremely deep voice and the harsh quality of distress calls fit the structure of aggressive signals and may resemble those produced by a larger animal. We propose that these calls serve as a last resort strategy to reduce post-encounter risk of predation, either as a startling effect to facilitate escape or to attract other predators that could intimidate the captor.
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.
The flash coloration hypothesis postulates that otherwise cryptically colored animals suddenly displaying conspicuous colors during movement confuse predators, reducing capture. Morpho helenor butterflies have contrasting colors on dorsal (iridescent blue) and ventral (brown) wing surfaces, resulting in sequential blue “flashes” during flight. We tested whether this flashing pattern reduces avian predation on M. helenor in Atlantic rainforest by changing the flashing effect in three experiments. In Experiment 1, we added a blue band to the ventral wing. In Experiment 2, we covered the dorsal wing's blue band with a brown band. Control groups in each experiment were painted such that wing color patterns remained unaltered. Survivorship was evaluated through mark-recapture censuses and beak marks on the wings. Results show that survivorship of treated butterflies in Experiment 1 decrease markedly compared to unaltered control individuals, while survivorship of treated butterflies in Experiment 2 did not differ compared to control individuals. In Experiment 3, we detected scant predation on treated (blue band added to ventral wing) and control butterflies (brown band added to ventral wing) on the forest floor (wings closed), corroborating that flash coloration is an important protective mechanism during flight. Our field experiments provide the first evidence, to our knowledge, that flash coloration in bright blue Morpho butterflies is an effective defense mechanism against avian predators in a tropical rainforest.
Pre-copulatory sexual cannibalism is an extreme form of aggression toward potential mates. In this study, we examined condition-dependent female aggression and its effects on mating success and frequency of pre-copulatory sexual cannibalism in the jumping spider Phidippus audax Hentz 1845. We examined two of the leading hypotheses of why sexual cannibalism may occur, (1) female mate choice and (2) adaptive female foraging. We separated 137 adult virgin female P. audax into three feeding treatments: (1) well-fed spiders, (2) 14-day food deprived, and (3) 28-day food deprived. We recorded weight loss (14- and 28-day treatments) and survival rates. We conducted mating trials to measure the proportion of non-aggressive and aggressive male and female behaviors, male mating success, and pre-copulatory sexual cannibalism. Females deprived of food had higher weight loss and lower survival rates than well-fed females. In addition, food deprived female spiders exhibited higher proportions of aggressive behaviors and pre-copulatory sexual cannibalism, and lower mating success compared to well-fed spiders. We found that as male size increased females were less likely to cannibalize males, but we found no effect of male body condition on whether a male mated with or was cannibalized by a female. Our results are consistent with the adaptive foraging hypothesis and corroborates prior research on pre-copulatory sexual cannibalism.
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