Behavioral Ecology and Sociobiology最新文献

Abstract

Social interactions among individuals within a species profoundly influence behavioural and life history traits, impacting fitness. While extensively studied in cooperative and eusocial species, the effects of social environment on fitness in non-social species, particularly insects, remain less explored. Our study investigates the impact of social environment, specifically male density, on fitness-related traits in the hymenopteran parasitoid Venturia canescens. The research focuses on longevity, reproductive behaviours (latency before mating, mating probability and duration), and offspring production capacity. Through a lifespan study, males were exposed to either isolation or regular encounters with conspecific males, alternating with periods of female presence or absence. Results show a trend of reduced longevity in socially exposed males and a significant decline in mating success with age in the social context. However, reproductive behaviours and offspring produced by males remain unaffected. This study sheds light on the intricate interplay between social environment, ageing, and reproductive strategies in non-social insect species, emphasizing the need for further exploration of social effects on male behaviour and notably potential influences of interactions between male and females but also between females.

Significance Statement

Impacts of social interactions on individuals were largely explored in social species, but remain little studied in non-social ones. This study aims at testing the impact of male-male interactions before the encounter of a female (past social interactions) on male reproductive behaviours and longevity in a non-social parasitoid wasp. We show that longevity is negatively affected by the past social interactions in this wasp. Those interactions also impose a decline in male mating probability with age (senescence pattern) or mating experience (number of matings). Latency before mating, mating duration and offspring production are not influenced by social environment. On the other hand, offspring production increases with mating experience.

Abstract

Offspring that delay dispersal in cooperatively breeding species have been hypothesized to gain direct fitness benefits via parental facilitation—being passively tolerated on their natal territory by their parents—thereby enjoying enhanced survival and increased probability of acquiring a breeding position in the population. Here we describe active facilitation in the acorn woodpecker (Melanerpes formicivorus) by parents and siblings assisting the dispersal of helpers in their social group. Helpers in this species compete for reproductive opportunities in “power struggles” that take place when all breeders of one sex die or disappear, creating a reproductive vacancy. Individuals compete at power struggles in coalitions of relatives, in which larger coalitions are more likely to be victorious. Based on observations of banded birds, we found that an estimated 26% of individuals competing as part of a winning coalition at a power struggle returned to their home territory at its conclusion, suggesting that they were facilitating the dispersal of kin (generally parents or siblings) that stayed to become breeders on the new territory. In at least one group, sibling facilitation was reciprocated; that is, a bird that was helped at a power struggle by a sibling joined that same sibling as part of a coalition at a subsequent power struggle. Dispersal facilitation is a novel means by which parents can nepotistically enhance the direct fitness of offspring and siblings can enhance each other’s inclusive fitness in this highly social species.

Significance statement

Parental facilitation—being passively tolerated on the natal territory—may provide significant direct fitness benefits to helpers in cooperatively breeding species. We describe active facilitation of helper dispersal in the acorn woodpecker, where helpers compete in coalitions for reproductive opportunities at “power struggles” following the death or disappearance of all breeders of one sex. About one-fourth of individuals—including both parents and siblings—competing at power struggles were apparently facilitators who assisted related helpers by participating in the power struggle but then returned to their home territory rather than stay to breed on the new territory. In at least one group, dispersal facilitation was reciprocated; that is, a bird that was helped at a power struggle by a relative later joined that same relative as part of a coalition at a subsequent power struggle. Active dispersal facilitation by parents and siblings is an important, previously unrecognized, form of nepotistic behavior in this highly social species.

Socioecological conditions are expected to influence the timing, or phenology, of when adult females give birth to offspring. Females may time reproduction such that offspring are born to maximize the length of the period that offspring have to forage during the growing season. In communal breeders, females may alter reproductive phenology to maximize benefits of group-living through synchronizing reproduction and improve offspring survival. We used an 11-year dataset on a population of communally breeding degus (Octodon degus) to test whether the (i) reproductive phenology was influenced by the abundance of food, social conditions, and the degree of masculinization of females and (ii) reproductive synchrony was influenced by similar access to food and degree of masculinization among females and communal litter size, in multi-female groups. The phenology of litter parturition (parturition day) was negatively associated with the abundance of food at burrow systems during winter (but not during spring) and was negatively associated with the number of adult females per social unit in the spring. Synchrony of litter production within communal groups increased in years with less available food. Our study suggests that degu females timed reproduction based the socioecological conditions likely to be experienced by their dependent offspring.

Life history theory emphasizes that finite resources result in allocation trade-offs among the competing interests of self-maintenance, growth, reproduction, and survival. Environmental conditions, particularly during development, can influence these life history trade-offs, leading to the coupling of physiological and behavioural traits with life history strategies. Thus, populations may vary in the pattern of trait covariation, clustering along a fast-slow continuum, termed the extended pace-of-life syndrome (POLS) theory. We aimed to test how variation in ecological conditions influence life history trade-offs and their association with behaviour and physiology by comparing captive bred and wild-collected southern rainforest sunskink (Lampropholis similis). The captive bred skinks were the offspring of the wild-caught skinks, and all tests were conducted in the laboratory. We found that the groups differed, on average, in growth rate, body condition, thermal preferences, sprint performance, and activity. Counter to our expectation, wild-caught skinks exhibited a faster pace of life relative to captive-bred skinks despite experiencing more challenging environmental conditions. Furthermore, life history trade-offs were not detected, nor were traits correlated to form the syndrome. Studies are needed to identify the proximate mechanisms causing life history trade-offs and how they lead to the coupling, or decoupling, of physiological and behavioural traits. Such information will provide vital insight into how ecological forces drive the evolution of traits.

In spring, many migrating songbirds exhibit protandry (the phenomenon whereby males precede females in arrival at breeding sites). The reed bunting (Emberiza schoeniclus) is a short-distance European migrant which expresses a high degree of protandry and combines both nocturnal and diurnal movements during migrations. In experimental conditions, we studied the proximate mechanisms of protandry and compared locomotor behavior between spring and autumn migrations. We assumed that captive behavior is a proxy for the behavior that birds demonstrate in the wild. Combined, the analysis of seasonal patterns and circadian dynamics of locomotor activity suggested that male reed buntings depart from wintering grounds by daytime flights approximately two weeks earlier than females. Later, they develop nocturnal activity, take off shortly before dawn and continue their flight for several hours in the morning. We argue that such behavior allows males to benefit from both the advantage of nocturnal flight and an efficient start of foraging, thereby reducing the stopover duration (by minimizing search/settling costs) and increasing the total migration speed. In contrast, females express predominantly nocturnal migratory activity in spring. We observed that in spring males had lower fat reserves compared to females. We suggest that males can forage during diurnal movements and therefore do not need to store large energetic reserves. In contrast, in autumn, both sexes display similar patterns of locomotor activity and fat reserves. Overall, our results describe unique sex-specific migratory behaviour and physiology in reed buntings in spring, which, we assume, contribute to spring arrival protandry in this species.

Brood parasitism and nest predation are among the main causes of breeding failures in passerine birds. Brood parasites threaten to the nest, while predatory birds threaten to both the nest and the parents. The objective of this study was to experimentally evaluate whether male and female Chestnut-capped Blackbirds, Chrysomus ruficapillus, recognize and respond to different nest threats during the breeding stages. For this purpose, we presented taxidermy models of a brood parasite, Molothrus bonariensis; a nest predator, Caracara plancus; and a non-predator species, Colaptes campestris, on the nest of C. ruficapillus. Additionally, we filmed nests without the display models to compare them with the nests exposed to taxidermy mounts. We assessed whether parents returned to the nest for each sex based on nest attention, visit frequency, and visit duration through the filming of a total of 44 nests. The parental return to the nest in the experimental trials varied between the sexes and breeding stages. During the incubation stage, males increased their nest attention and frequency of visits in the presence of the non-predator and brood parasite models. Females also increased their frequency of visits in the presence of the non-predator model in relation to the predator and brood parasite models. During the nestling stage, males extended the duration of their visits in the presence of the predator model compared to nests without the display model. Meanwhile, females showed no differences in their behavior during this stage. Overall, the Chestnut-capped Blackbirds parents demonstrated the ability to recognize the presented models and responded differently to different threats at different stages of the breeding cycle. The flexible responses they exhibited may be consistent with the `threat-sensitive predator avoidance´ hypothesis.

Abstract

Populations of long-distance migratory species may exhibit dissimilarities in the leeway of scheduled annual migration programs, the routes they follow and their convergence at ecological barriers. The aim of this study was to fill the current geographical gap, spanning over 1,100 km longitudinally between southern France and eastern Austria, in the pan-European assessment of the migration ecology of the European Roller Coracias garrulus, and contribute to completing the puzzle of spatio-temporal patterns of migration, stopover and wintering at the Western-Palearctic scale for this species. We utilized high-resolution GPS tracking data from adult Rollers breeding in Italy and Croatia, tracked on their intercontinental seasonal journeys between 2018 and 2022 and modelled the variation of migratory components both at individual and population levels. Rollers from the Central Mediterranean exhibited a clockwise spring migration loop, following a Central African migration route and wintering across a wide longitudinal belt spanning from Namibia to Mozambique. Northern savannah zones were used as long stopovers, both in autumn (Chad/Sudan) and spring (Central African Republic/Cameroon). The probability of movement was significantly higher during the night and in spring. Migration speed varied according to season (> in spring) and the habitat crossed (sea > desert > rainforest > savannah). Individuals tracked in successive years showed high consistency of key migratory parameters and partial winter home ranges overlap, in contrast with the large variability of migratory parameters at the population level. This work bridges the current geographical gap of Roller migration ecology at the European level and helps meet conservation needs at the scale of the species’ flyway, with new ecological information valuable for the implementation of International Single Species Action Plans (ISSAP) dedicated to the Roller.

Significance statement

Tracking studies help to disentangle intraspecific variation in migratory strategies and wintering destinations among populations, as well as investigate individual-level decisions taken en route across seasonal journeys. By GPS tracking the intercontinental migration of adult Rollers we found that spatio-temporal components of migratory and flight strategy largely depend on extrinsic factors such as daytime, season and the habitat they traversed, and vary at population level. In contrast, within-individual consistency in migratory and wintering patterns emerged across years. Our findings emphasize the need for effective conservation strategies at the flyway scale.

Abstract

Sexually cannibalized males incur a significant fitness cost due to the loss of future mating opportunities and are expected to evolve behaviors to avoid or compensate for such costs. For example, partially cannibalized males may exhibit mate guarding, in which they accompany the female to prevent her from mating with another male. In some species, cannibalized males prolong the duration of copulation. However, little is known about the adaptive significance of the mating behavior of sexually cannibalized males. We hypothesized that mating itself serves a mate guarding function, and that behavioral change caused by cannibalism enhances the mate guarding function. We tested these hypotheses using the polyandrous and sexually cannibalistic praying mantid Tenodera angustipennis, with decapitation as a model of sexual cannibalism. We compared latencies to female mating with a rival male among three experimental treatments: unmated treatment, noncannibalistic mating treatment, and cannibalistic mating treatment. Mating itself delayed female remating, revealing its function in mate guarding. Decapitated males exhibited a higher guarding efficiency against rival males via firmer genital coupling. In addition, spermatophore attached to the female genital opening also delayed female remating, revealing an additional function in postmating mate guarding. Although copulation was prolonged due to decapitation, mating by a rival male was not delayed compared to noncannibalistic mating, probably because of weaker postcopulatory guarding. These findings suggest that greater mate guarding by decapitated males during copulation was offset by processes after copulation.

Significance statement

Sexually cannibalized males die and lose the chance for future mating. This means that males that can avoid or compensate for this fitness loss may be favored. We examined this possibility by focusing on the postmating behavior of sexually cannibalized male mantises. Experimental analysis revealed that cannibalized males grasped the female more firmly during copulation to avoid disruption by other males, and prolonged copulation duration compared with noncannibalized males. These behavioral changes by cannibalized males contributed to delaying female remating with other males to the same extent as noncannibalized males. This suggests that sexually cannibalized males did not fully compensate for the loss of future mating opportunities. Stronger mate guarding via firm genital coupling and prolonged copulation duration in cannibalized males may be offset by weaker postcopulatory guarding such as shorter duration of copulatory plug attachment.

Symptoms of illness offer insights into an organism’s condition, altering social signals that affect others’ behavior. Nestling birds employ begging signals to solicit parental care, but the extent to which begging reflects nestling health beyond hunger remains controversial. We investigated how experimentally induced changes in health affect begging signals in spotless starling (Sturnus unicolor) nestlings. To alter health status, we challenged nestlings by injecting lipopolysaccharide (LPS) -an antigen that elicits an immune response- or a control substance (PBS) and observed begging behavior under controlled food deprivation conditions. LPS-treated nestlings exhibited delayed gaping, reduced stretching, and less begging time compared to control nestlings. Moreover, LPS-treated nestlings produced calls with higher spectral entropy, particularly when deprived of food for longer. Our findings indicate that begging signals are sensitive to induced sickness. However, addressing mechanistic issues is crucial for effectively testing whether begging reflects nestling condition as a signal of quality in future experimental setups.

Abstract

Variation among resource patches can structure spatial patterns of social behavior. Individual preferences and requirements for heterogeneous resources can lead to differences in where behaviors take place and which kinds of individuals interact. In this study we examined whether properties of habitat patches predict presence of and interactions among wild forked fungus beetles (Bolitotherus cornutus). B. cornutus use shelf-like fruiting bodies of wood decaying fungi (brackets) as social arenas, courtship and mating sites, oviposition locations, and food sources. Brackets on a single log vary in size and condition and represent a dynamic resource as individual brackets decay over the years that they persist on a subpopulation. We found that size and condition significantly predicted how a bracket was used by B. cornutus. Both males and females were found more often on larger, living brackets. Larger brackets hosted proportionally more social interactions and mating behaviors relative to the overall visitation by individuals. The relationship between these resource properties and frequencies of behaviors was stronger for reproductive, between-sex social interactions. Live brackets also attracted more oviposition events by females, but bracket size had no effect on this behavior. Our results indicate that the dynamics of growth and aging of a critical resource can impact how social and reproductive behaviors are distributed in time and space, which in turn could affect the social structure of subpopulations.

Significance statement

Species that depend on critical host resources are often faced with a patchy landscape of resource quality. Those patches represent the infrastructure within which social behaviors take place, and can have formative effects on where, when, and how social interactions occur. We demonstrated that the size and condition of a fungal resource predicted male and female forked fungus beetle presence and behavior. Larger, living brackets hosted more beetles overall, while larger brackets in any condition hosted more social interactions and mating behaviors. Female beetles were more likely to lay eggs on living brackets, regardless of size. This study demonstrates how ecological dynamics of aging resource patches can indirectly structure social landscapes by influencing where and how individuals interact.