Watch out! Insecure relationships affect vigilance in wild spider monkeys ( Ateles geoffroyi ) Abstract Vigilance is used to monitor extra-group threats as well as risky group members. We examined whether relationship quality affects vigilance patterns of spider monkeys. We used focal animal sampling to collect data on social interactions and individual vigilance of all adults and subadults (N = 22) in a community of well-habituated Geoffroy’s spider monkeys living in the protected area of Otoch Ma’ax Yetel Kooh, Yucatan, Mexico. Through a principal component analysis of seven indices of social interactions, we previously obtained three components of relationship quality, reflecting the levels of compatibility, value, and security. Such components could differentially affect vigilance depending on whether vigilance is directed to extra-group threats or risky group members. We tested whether an individual’s vigilance was affected by (1) the mean level of compatibility, the mean level of value and the mean level of security across subgroup members; (2) the lowest level of compatibility, the lowest level of value, and the lowest level of security with any subgroup member; and (3) the mean level of compatibility, the mean level of value, and the mean level of security with neighbors (i.e., subgroup members within 5 m). We did not find evidence for any effect of compatibility and value; however, security did affect vigilance, as individuals were more vigilant when they had a less secure relationship with the subgroup member with the lowest level of security or with the average neighbor. Significance statement Vigilance for monitoring group members is common in primate species. We examined whether the quality of social relationships with subgroup members and neighbors modulates vigilance in wild spider monkeys. We used three components of relationship quality (reflecting the levels of compatibility, value, and security) and predicted each component would affect vigilance depending on whether vigilance was directed to extra-group threats or risky group members. We found no evidence that compatibility and value affected vigilance. However, an increase in vigilance occurred when spider monkeys had a less secure relationship with (1) the subgroup member with the lowest level of security and (2) the average neighbor. Our results show monitoring risky group members is an important component of vigilance, especially in species facing low predation pressure.

Proximity to humans is associated with longer maternal care in brown bears Abstract In the sexual conflict over the duration of maternal care, male mammals may improve their reproductive success by forcing early mother–offspring separation in species where lactation supresses estrus. However, when individual females benefit from continuing to care for their current offspring, they should adopt counter-strategies to avoid separation from offspring. Here, we tested whether spatial segregation from adult males and proximity to humans during the mating season could be associated with longer maternal care in the Scandinavian brown bear (Ursus arctos). Using resource selection functions (RSFs), we contrasted habitat selection patterns of adult males and those of adult females with yearlings that either provided 1.5 years of maternal care (“short-care females”) or continued care for an additional year (“long-care females”) during the mating season, the period when family break-ups typically occur. Males and short-care females had similar habitat selection patterns during the mating season. In contrast, habitat selection patterns differed between males and long-care females, suggesting spatial segregation between the two groups. In particular, long-care females used areas closer to human habitations compared with random locations (defined here as selection), whereas males used areas further to human habitations compared with random locations (defined here as avoidance). Our results show a correlation between habitat selection behavior and the duration of maternal care. We suggest that proximity to humans during the mating season may represent a female tactic to avoid adverse interactions with males that may lead to early weaning of offspring. Significance statement In mammalian species where lactation supresses ovulation, males may gain a reproductive advantage by forcing early mother-offspring separation; however females can respond through behavioral tactics. We show that female brown bears with yearling cubs can spatially segregate from males during the mating season and that this behavior is associated with longer maternal care. Females selecting areas close to human habitations tend to keep their yearlings for an additional year, suggesting that human presence could have a shielding effect from males. Our study is among the few to explore sexual conflicts over the duration of maternal care close to weaning and shows that animals have the potential to adjust their behavioral tactics to make use of human-dominated landscapes.

An experimental increase in female mass during the fertile phase leads to higher levels of extra-pair paternity in pied flycatchers Ficedula hypoleuca Abstract Female mass in most altricial birds reaches its maximum during breeding at egg laying, which coincides temporally with the fertile phase when extra-pair paternity (EPP) is determined. Higher mass at laying may have two different effects on EPP intensity. On the one hand, it would lead to increased wing loading (body mass/wing area), which may impair flight efficiency and thereby reduce female’s capacity to resist unwanted extra-pair male approaches (sexual conflict hypothesis). On the other hand, it would enhance female condition, favouring her capacity to evade mate guarding and to search for extra-pair mates (female choice hypothesis). In both cases, higher female mass at laying may lead to enhanced EPP. To test this prediction, we reduced nest building effort by adding a completely constructed nest in an experimental group of female pied flycatchers (Ficedula hypoleuca). Our treatment caused an increase in mass and thereby wing loading and this was translated into a significantly higher EPP in the manipulated group compared with the control group as expected. There was also a significant negative relationship between EPP and laying date and the extent of the white wing patch, an index of female dominance. More body reserves at laying mean not only a higher potential fecundity but a higher level of EPP as well. This interaction had not previously received due attention but should be considered in future studies of avian breeding strategies. Significance statement While most research has been focused on determining possible criteria for extra-pair mate choice by females, less effort has been made on establishing if female traits are related to EPP and its intensity. One such trait is mass at laying which attains its highest level for breeding females of altricial birds. Our study indicates that a higher mass during the fertile phase not only has implications for female fecundity and predation risk but also for EPP in the resulting brood as more mass means a higher EPP.

Age-related patterns of yolk androgen deposition are consistent with adaptive brood reduction in spotless starlings Abstract Female birds can influence offspring development by adjusting egg size or by a differential allocation of egg resources. Such maternal effects can be expected to be shaped by natural selection, given the costs connected to the allocation of maternal resources. Among egg components, yolk androgens play an important role in affecting offspring life-history traits. Despite their relevance for nestling development, factors accounting for the observed within- and between-clutch variation are still poorly known. By using a cross-sectional sampling approach, we tested the effect of female age, laying order and laying date on the deposition of yolk androstenedione (A4) and testosterone (T), since young and older females could maximize their fitness differently according to breeding conditions. We found a remarkable lack of differences in overall yolk androgen levels across different ages. However, comparing first-year with older females, our results showed that age did not influence yolk T levels at the beginning of the breeding season, whereas at the end, first-year females transferred lower hormone levels than older females. Within clutches, both androgens increased across the laying sequence, suggesting that late nestlings benefit from an increased allocation that could compensate hatching asynchrony. However, when considering A4, we found that, whereas older females always increased A4 levels across the laying sequence, first-year females did not increase it at the end of the breeding season, thus increasing the likelihood of brood reduction when environmental conditions became hardest. These findings suggest that yolk A4 variation may be particularly important at the within-clutch scale, by providing females with a tool to modify nestling hierarchies. Significance statement The study of maternal effects shows that avian mothers can adjust offspring development to environmental conditions by altering egg composition. The effects of maternal age on such egg allocation process depend on the balance of benefits and costs that affects each age class. We examine if young and older mothers differ in terms of yolk androgen deposition and egg quality, since age may influence offspring fitness, and could represent a costly maternal investment. We found an absence of overall age-dependent patterns in yolk androgen deposition, except when we considered laying order and laying date. In late clutches, when breeding conditions are harsher, 1-year-old females carried out a lower deposition of both resources (yolk mass) and modifiers (androgens) than older mothers did. We suggest that such a pattern would reinforce the effects of hatching asynchrony, favouring brood reduction at the end of the breeding season by first-year females.

Food or host: do physiological state and flower type affect foraging decisions of parasitoids? Abstract Within the optimal foraging theory framework, parasitoids constitute ideal models to elucidate combined physiological and environmental determinism of foraging behavior between current and future fitness gains. Parasitoid females need hosts to lay eggs for their reproduction (immediate gain), but also sugar food resources for their survival (future gain). According to theoretical models and previous empirical studies, fed females should favor host foraging, whereas females with lower energetic reserves should search for food. Surprisingly, the influence of mating status and food quality has not been considered, whereas they may both constitute major factors altering animals’ choices between reproducing and feeding. We tested decision-making on Aphidius rhopalosiphi parasitoid females with different life expectancy levels (as set by recent feeding history) and mating status, using two flower species with contrasted attractiveness and nectar suitability. Interestingly, all fed and unfed females with different expected lifetime levels favored reproduction over nutrition since they are mated. This could be explained by their reproductive status that appeared to be the main determinant of their foraging decisions. For a given expected lifetime, mated females favored more reproduction whereas unmated ones favored food. Physiological status of females (mating and lifetime expectancy) did not interact with flower species on their foraging decisions nor did it modify their preferences, as they always favored the most attractive flower, which does not have the best nectar. These results highlight the need for more empirical studies to evaluate the interactions between different intrinsic factors and to carefully consider the mating status in model assumptions, as it influences foraging behavior between immediate and future fitness gains. Significance statement Parasitic wasps need hosts to lay eggs for their reproduction (immediate fitness gain) and sugar resources for their survival (future fitness gain). Empirical studies and related theoretical models about foraging decisions of parasitic wasps between current and future gains included influences of energetic and resource availability constrains. We examined assumptions used by those mathematical models by empirically testing two new factors, food qualities provided by two nectar provisioning flower species with contrasted functional traits, which had surprisingly no impact on decision-making, and mating status which we showed to play a decisive role on decision-making between food or host resources. These factors should henceforth be considered in model assumptions or in models themselves to realize accurate predictions and to provide a better understanding of foraging decisions made by female parasitic wasps.

Male guppies differ in daily frequency but not diel pattern of display under daily light changes Abstract Sexually signalling animals must trade off the benefits of attracting mates with the consequences of attracting predators. For male guppies, predation risk depends on their behaviour, colouration, environmental conditions and changing intensity of predation throughout the day. Theoretically, this drives diel patterns of display behaviour in native Trinidadian populations, where males display more under low-light conditions when their most dangerous predator is less active. Here, we observed Australian guppies in a laboratory setting to investigate their diel display pattern, and if this pattern is controlled by ambient light intensity. We also quantified individual variation in both the daily frequency and diel pattern of displays, and if such variation relates to body size, colouration and a non-sexual behaviour. Under a typical daily light regime, male guppies displayed mostly in the first hour of observation. Extending the duration of dawn-like lighting, however, resulted in an extended period of high display, demonstrating that light intensity per se is an important cue for this behaviour. These findings mirror those obtained for Trinidadian populations, suggesting that male courtship timing is likely shaped by broad, potentially generalizable features of guppy ecology. The effect of acclimation to captive conditions on male behaviour is also discussed. Whereas the temporal pattern of display appeared consistent, individuals varied in their daily display frequency, and this was correlated with variation in colour phenotype and a measure of non-sexual risk acceptance behaviour. Such relationships pose promising avenues for integrating behavioural and sensory ecology with contemporary work on behavioural syndromes and animal personality. Significance statement To limit the costs of their conspicuous colour patterns, male guppies should alter their behaviour to avoid predation. However, our understanding of how different individuals deal with this problem is lacking. Following individuals in the laboratory, we demonstrated individual variation in the daily frequency of male displays, and this was correlated with variation in colour phenotypes and non-sexual behaviour. However, all male guppies displayed more in the early hours of the day and extending the period of low lighting also extended this period of elevated display. These findings replicate and expand experiments on native populations, suggesting that male courtship timing is likely shaped by broad, potentially generalizable features of guppy ecology.

A biologging perspective to the drivers that shape gregariousness in dusky dolphins Abstract Knowledge of proximate (causation and development) and ultimate (evolution and survival function) causes of gregariousness is necessary to advance our knowledge of animal societies. Delphinids are among the most social taxa; however, fine-scale understanding of their intra-specific relationships is hindered by the need for underwater observations on individuals. We developed a non-invasive animal-borne camera system with the goal of examining influences on gregariousness in dusky dolphins (Lagenorhynchus obscurus). We analyzed video and diving records from 11 individual dusky dolphins off Kaikoura, New Zealand. We examined the influence of biologger attachment on dolphin behavior and tested hypotheses regarding the effects of physiology, predation, and inter-individual variation on conspecific interactions. Dolphins did not exhibit increased rates of descent or ascent in the minutes immediately following biologger attachment, indicating a lack of behavioral response. Respiration rate was positively related to dive depth and duration, suggesting that diving is energetically expensive for this species. Gregariousness was negatively related to dive depth providing evidence that the physiological constraints of diving are likely to limit social behavior. Calves were not observed more frequently in infant (vs. echelon) position with increasing depth, highlighting the likelihood of other anti-predation strategies (e.g., dilution effect) in mother-calf pairs. We found that gregariousness differed between individuals within similar social groups, suggesting the importance of collecting data at the individual level. The evidence presented herein suggests that the further development of animal-borne camera systems will yield further insight into the mechanisms underlying delphinid social behavior. Significance statement Dolphins are highly social and thus excellent model species for examining the cause and function of gregariousness. However, their cryptic nature poses a challenge to collecting the fine-scale data at the individual level required to conduct rigorous hypothesis tests. We overcame this obstacle by deploying a non-invasive cutting-edge biologger on free-ranging dusky dolphins to collect information on diving behavior, physiology, gregariousness, and mother-calf strategies. Results indicate that diving is energetically expensive, even to relatively shallow depths, and these costs likely hinder gregariousness at depth. Individual differences in gregariousness were apparent and as expected in this fission-fusion society. Unexpectedly, mother-calf pairs appeared to utilize strategies other than spatial positioning to minimize predation risk. This study advanced knowledge of dolphin social life and helps to improve the degree of data resolution in cetaceans to a level on par with terrestrial studies.

Using time-series similarity measures to compare animal movement trajectories in ecology Abstract Identifying and understanding patterns in movement data are amongst the principal aims of movement ecology. By quantifying the similarity of movement trajectories, inferences can be made about diverse processes, ranging from individual specialisation to the ontogeny of foraging strategies. Movement analysis is not unique to ecology however, and methods for estimating the similarity of movement trajectories have been developed in other fields but are currently under-utilised by ecologists. Here, we introduce five commonly used measures of trajectory similarity: dynamic time warping (DTW), longest common subsequence (LCSS), edit distance for real sequences (EDR), Fréchet distance and nearest neighbour distance (NND), of which only NND is routinely used by ecologists. We investigate the performance of each of these measures by simulating movement trajectories using an Ornstein-Uhlenbeck (OU) model in which we varied the following parameters: (1) the point of attraction, (2) the strength of attraction to this point and (3) the noise or volatility added to the movement process in order to determine which measures were most responsive to such changes. In addition, we demonstrate how these measures can be applied using movement trajectories of breeding northern gannets (Morus bassanus) by performing trajectory clustering on a large ecological dataset. Simulations showed that DTW and Fréchet distance were most responsive to changes in movement parameters and were able to distinguish between all the different parameter combinations we trialled. In contrast, NND was the least sensitive measure trialled. When applied to our gannet dataset, the five similarity measures were highly correlated despite differences in their underlying calculation. Clustering of trajectories within and across individuals allowed us to easily visualise and compare patterns of space use over time across a large dataset. Trajectory clusters reflected the bearing on which birds departed the colony and highlighted the use of well-known bathymetric features. As both the volume of movement data and the need to quantify similarity amongst animal trajectories grow, the measures described here and the bridge they provide to other fields of research will become increasingly useful in ecology. Significance statement As the use of tracking technology increases, there is a need to develop analytical techniques to process such large volumes of data. One area in which this would be useful is the comparison of individual movement trajectories. In response, a variety of measures of trajectory similarity have been developed within the information sciences. However, such measures are rarely used by ecologists who may be unaware of them. To remedy this, we apply five common measures of trajectory similarity to both simulated data and real ecological dataset comprising of movement trajectories of breeding northern gannets. Dynamic time warping and Fréchet distance performed best on simulated data. Using trajectory similarity measures on our gannet dataset, we identified distinct foraging clusters centred on different bathymetric features, demonstrating one application of such similarity measures. As new technology and analysis techniques proliferate across ecology and the information sciences, closer ties between these fields promise further innovative analysis of movement data.

Ability makes a thief: vision, learning, and swift escape help kleptoparasitic hover wasps not to fall prey to their spider hosts Abstract Stealing prey items from other animals entails obvious benefits for the thief. However, this so-called kleptoparasitic behavior can also involve costs including injury or even death, especially when stealing from a potential predator. Here, we examined how kleptoparasitic hover wasps (Parischnogaster sp.) that steal prey items out of spider webs handle the risk of falling prey to their hosts. We tested the wasps’ ability to evade different webs under natural and experimental conditions and whether webs are perceived visually. Further, we tested whether wasps learn about web position and are able to avoid them in future trajectories as well as how quick wasps escape from webs once entangled. Additionally, we recorded the attack time for different spider species towards prey items placed into their webs, to estimate the risk of being attacked when entangled. Our results provide strong support for visual web perception by wasps facilitating the successful evasion of webs in flight trajectories, learning capability, and quick escape from webs once entangled. At the same time, the results, together with our observations in the field, suggest a specialization of kleptoparasitizing spider webs with overall lower risk of predation. Significance statement Stealing prey from other predators often entails significant risk of injury and death. Yet, most research on such kleptoparasitism focused on the benefits to the kleptoparasite or the cost to the host, thereby overlooking an important component to explain the evolution and maintenance of kleptoparasitism. Here, we examine the potential costs for hover wasps when stealing prey from spider webs and test how wasps reduce the potential risks of this kleptoparasitic foraging behavior. While often described from casual observations, kleptoparasitism in hover wasps is so far unstudied. We show that kleptoparasitism from spider webs is associated with costs for hover wasps, but that visual detection of webs, avoidance learning, and rapid escape behavior mitigate those costs. Our study hints at hover wasps targeting certain host species where their mitigating strategies are most effective.

Echolocation call divergence in bats: a comparative analysis Abstract Animal vocalizations experience pressures from ecological conditions, but their diversification may be constrained by morphology and evolutionary history. To date, the relative contribution of these factors to acoustic diversity is unclear in most vertebrate groups. Bats constitute one of the most speciose and diverse mammal groups, and most bat species rely on vocalizations for orientation, foraging, and communication. Here, we examine echolocation calls of 207 bat species across 17 families to weigh the relative role of phylogenetic inertia, natural selection, and morphological constraints in shaping echolocation call diversity in bats. Using the large dataset, we confirm that foraging guilds, phylogenetic relationships, and forearm length account for the majority of the variation in call parameters among bats. Foraging guilds play a major role in influencing call parameters in low duty cycle bats. At the family level, the variation in call parameters is primarily explained by differences in body size and phylogenetic relationships. Path analyses indicate that phylogeny determines call output not only by their direct effect on call parameters but also by having an indirect effect via foraging guilds and body size. These results demonstrate that natural selection, phylogenetic constraint, and morphological constraint shape echolocation call divergence in bats. Our findings underscore the importance of both adaptive and non-adaptive mechanisms underlying the evolution of echolocation calls in bats. Significance statement Ecology, morphology, and evolutionary history are tightly coupled; therefore, disentangling the relative strength of these components underlying acoustic diversity is a big challenge. Using a large dataset of bats, we assess the influence of phylogeny, ecology, and body size on echolocation call parameters. We conclude that ecological selection, phylogenetic constraint, and morphological constraint play a crucial role in shaping echolocation call divergence among bats. This study expands our knowledge of the relative contribution of adaptive and maladaptive mechanisms to echolocation call diversity at different taxonomic levels in bats.