Behavioral Ecology and Sociobiology最新文献

Parental brood care greatly affects offspring’s fitness, but the specific effects of care on the collective behaviour of independent offspring are less well understood. It has been suggested that the loss of care induces increased sibling cooperation to compensate parental contributions. However, the empirical evidence is ambiguous. Here, we examined how the loss of early parental care affects the collective behaviour, i.e. shoaling performance of independent juveniles in a genetically heterogeneous lab-population of the biparental cichlid fish Pelvicachromis pulcher. Applying a split-clutch design, we reared in- and outbred offspring with or without parents. In the experiment, we examined shoal density (inter-individual distance) in relation to body size of the shoaling fish. Dense shoaling reduces predation risk and small fish may benefit strongest because they are particularly vulnerable to predation by gape-limited predators. Juveniles reared without parents formed denser shoals and they adjusted shoaling behaviour depending on own body size compared to juveniles reared with parents; especially smaller fish formed dense shoals. Inbreeding did not significantly affect shoaling performance. This indicates that juveniles compensate missing parental care by adjusting their shoaling behaviour depending on own vulnerability. Our study contributes to the understanding of the co-evolution of brood care and sibling cooperation.

Animals compete for limited resources such as food, mating partners, and territory. The outcome of this intraspecific competition should be determined by individual variation in behavioral traits, such as aggressiveness and dominance status. Consistent among-individual differences in behavior likely contribute to competitiveness and predispose individuals to acquire specific dominance ranks during parts of their adult life. Nevertheless, how dominance rank is correlated with animal personality traits remains largely unclear. In a first step towards better understanding these functional links, we studied trait integration into behavioral syndromes, using 26 captive male bank voles (Myodes glareolus). We repeatedly assessed boldness in an emergence test, exploration in an open-field test, aggressiveness in staged dyadic encounters, and the among-individual correlations between these behaviors. We further related these personality traits to dominance rank, from quantifying urine marking value (UMV), as marking in bank voles is related to dominance rank. We found repeatable variations in boldness, exploration, aggressiveness, and UMV, which were correlated at the among-individual level. Aggressiveness tended to be negatively correlated with body condition, a proxy for fitness. Thus, key personality traits and social rank are functionally integrated into a behavioral syndrome of intraspecific competitiveness. By joining social and non-social aspects of personality, our findings contribute to the ecological validation of personality traits and suggest how they contribute to higher-order component traits, such as dominance which directly affect fitness components.

Multiple within individual and non-redundant signals can convey complementary information about individual quality in lizards. This visual information is commonly provided by colour patches of different hues (red, yellow, blue). However, whether different within-individual colour patches of a single hue can contain non-redundant information remains understudied. To test this idea, we investigated the spectrophotometric reflectance of three colour patches in adult males of Acanthodactylus erythrurus, a lizard of the family Lacertidae that has colour patches that look similarly yellow to the human eye. We modelled the spectral variables of these patches using model averaging and cross-validation as a function of head volume and body length (proxies of resource allocation to somatic growth), escape behaviour (proxy of quality to cope with stress), body condition (proxy of nutritional state), leukocytic profiles (proxy of immune state), and faecal testosterone metabolites (proxy of reproductive state and aggression). The different relationships of the three “yellow” patches with the independent predictors analysed suggested that they can provide complementary information about the males’ quality in the context of the sexual selection theory.

Abstract

Human-induced disturbance is perceived by avian species as a predation risk. However, the anti-predatory behaviour triggered by these non-lethal events can have negative impacts on reproduction and offspring survival. Research on breeding birds often involves visits to their nests and is likely to disrupt parental behaviour, but nest visits that do not involve direct handling of females have been overlooked as important disturbance events. This study focuses on the impacts of short visits to the nest of incubating Great tit (Parus major) females. We investigated how long they stay away from the nest (off-bout) after a disturbance, their possible compensatory behaviour once they resume incubation (on-bout), and the effects on daily incubation rhythms. We used three years of data from two breeding populations to assess the consequences of disturbances in two scenarios: when the female is present in the nest and flushed, and when the female is absent. We found that after a disturbance, the immediate off-bout was longer when the female was either present or absent, with the magnitude of the disturbance being greater when females were flushed. Females did not compensate with longer on-bouts afterwards, i.e. the research disturbance altered daily incubation behaviour by reducing the total time spent on the nest in relation to the number of daily disturbance events. Females that alter their behaviour in response to perceived predation risk would perform longer incubation periods, resulting in lower hatching rates. These effects of research on female behaviour should be considered when planning field experiments.

Significance statement

Incubating birds react to human activity near their nests by changing their behaviour. This may also apply to basic research activities, but we have no data on how a visit, e.g., to check clutch size, affects them. To find out, we classified data from routine research visits to great tit nests, which are often used for research in the wild, into long and short visits. We also considered whether a female was incubating or foraging outside the nest during the visit. We found that females tended to stay away from the nest longer after they encounter a researcher, and after longer visits. Our results show that even slight research activities in the nest alters female incubation behaviour. They flee and leave the clutch unattended for longer, changing the thermal environment of the nest, which is crucial for proper embryo development.

Ants often face injuries during foraging, or interspecific competition, elevating infection risk and mortality among the wounded. To avoid this, ants engage in wound care on injured nestmates as a form of social immunity. In this study, we show that Cataglyphis nodus desert ants perform differentiated wound care behavior, depending on wound location and state. Leg-injured ants received significantly more wound care than antenna-injured ants. However, leg wounds with induced infections received barely any wound care from nestmates, leading to similar levels of mortality in isolation and inside the nest. Instead, such leg-infected ants were mainly found outside of the nest. Infections of antennal wounds showed no change in the level of wound care, nor increased mortality. Our results suggest that the level of wound care in ants can be flexibly adjusted to the perceived mortality risk of injuries. Leg injuries pose a greater risk of infection and mortality compared to antennal injuries, likely because of the larger wound area and increased vascular circulation, necessitating intensive prophylactic care to prevent infection. This study is the first to show wound care in Cataglyphis ants, despite their short lifespan, and offers significant insights into social immunity mechanisms.

Diving behavior is common among lizards for predator avoidance and foraging purposes. Understanding the factors influencing the maximum dive duration of diving lizards is crucial for comprehending their ecological strategies and survival mechanisms. This study aims to investigate the relationship between the maximum dive duration of diving lizards and their life history traits and environmental factors. The study collected diving data from a total of 52 lizard species, employed phylogenetic generalized least squares models, Markov chain Monte Carlo generalized linear mixed models, and phylogenetic path analysis methods. Our findings revealed significant correlations between maximum dive duration and key life history traits, including body weight, snout-vent length, longevity, tail length, and clutch size. Notably, after controlling for snout-vent length, tail length showed a significant negative correlation, while clutch size showed a significant positive correlation with maximum dive duration. In conclusion, our study sheds light on the crucial role of life history traits in shaping the maximum dive duration of diving lizards, offering valuable insights into their ecological adaptations and survival strategies.

Why do animals display sexual ornaments – to attract mates, to compete for access to them, or both? In the broad-nosed pipefish (Syngnathus typhle), ornamented females commonly compete for access to males, whereas choosy males provide uniparental care. During courtship, females show a dynamic ornament, consisting of a row of dark B-shaped signs along the sides of their trunk. Here, we focus on the social context of female ornamentation and mating success (egg transfer) under experimentally female and male biased adult sex ratios. We found that the duration of female B-sign displays was not explained by adult sex ratios alone, but rather by sex ratios in combination with female body length and the number of female interactions. In detail, duration of B-sign display increased more steeply with the number of female-female interactions under the male biased adult sex ratio: that is, when more mating opportunities were available. Similarly, display duration increased with female body length, but only under the male biased adult sex ratio. In addition, successful egg transfer occurred more often in the male biased treatment and correlated significantly with female display duration in the same treatment. Taken together, these results suggest that in the context of the broad-nosed pipefish, the ornamental B-signs in females primarily serve as a sexually selected attractive signal. Our results highlight the importance of an interactive mating environment, male availability, and female size.

Prey naiveté has been implicated in the global decline and reintroduction failure of many threatened species. A number of tools have been developed to combat prey naiveté including in situ predator exposure using live predators. However, determining the effectiveness and persistence of these interventions can be difficult, and requires comparisons of individual responses from predator-naïve and predator-trained populations. Even when this occurs, interpreting behavioural responses can be challenging because of the constraints of experimental design in large scale population manipulations. We used a common environment experiment and placed burrowing bettongs (Bettongia lesueur) from predator-free and predator-exposed populations together in an 8 ha fenced paddock. The predator-exposed population had been previously exposed to feral cats (Felis catus) under controlled wild conditions for up to six years and initial work suggested this exposure had led to physical and behavioural changes. Within our common environment experiment we compared a range of anti-predator behaviours including trap and feeding behaviour and response to predator scent and models. We found evidence for persistent trait changes up to 7 months, the latest time behaviours were tested, after bettongs were moved to the predator-free common environment and isolated from predators. These behaviours include reduced alarm rates, preference for open areas, and responses to predator scent and model stimuli. Additionally, high risk predator cues were more likely to elicit anti-predator responses than passive measures of anti-predator behaviour. Our design shows that predator exposure leads to persistent shifts in some, but not all, anti-predator behaviours. Identifying the proximate basis of anti-predator traits is important to develop successful tools to combat prey naiveté.

Experimental research and theoretical models question the Darwin-Bateman paradigm that male reproductive success is just limited by the number of mates. Males have evolved tactics to tailor ejaculates among their mates to maximise fitness. Males are expected to be choosy and to bias ejaculate investment depending on the perceived quality of females (cryptic male choice) and/or the reproductive social context. We investigated ejaculate allocation strategy in Lobesia botrana, a mostly monandrous moth, depending on male size, female size, and their interaction, the latter effect being usually overlooked in most studies. The explained variables were absolute ejaculate size (spermatophore volume) and relative ejaculate size (ejaculate size to lifetime ejaculate expenditure ratio). Absolute ejaculate allocation analysis showed that: (1) ejaculate expenditure increases with male size; (2) males tailor greater ejaculates to larger than smaller females; and (3) there was no interaction between male size and female size, so small and large males tailored equivalent increases in ejaculate volume per female weight unit. Quite differently, relative ejaculate allocation analysis showed that: (1) small males invest comparatively more than large males in females of similar size; and (2) there was an interaction between female size and male size, so small males invest comparatively more than large males when mated with large females. Results are discussed in the framework of strategic ejaculate allocation from an evolutionary perspective, as ecological variables, including the current climate change scenario, may promote coexistence in the field of quite different-sized adults in this moth species.

In mammals, birth mass is an important predictor of early growth and survival. Within litters, heavier siblings are usually able to outcompete smaller siblings and gain more resources, thereby often permanently shaping phenotypic development. Early body size and growth are particularly important for later fitness. Only few studies investigated if and how differences within the early family environment contribute to long-term variation in fitness among individuals. We quantified if initial differences in size translate to size differences in adulthood and whether birth mass, relative size within the litter, litter size or the litter sex-ratio affect maturation and reproductive output of female wild cavies (Cavia aperea). Initial differences in mass were maintained until animals reached maximum adult mass at two years of age. Heavier sisters matured earlier and invested more into their first litter than smaller sisters, presumably because smaller sisters invested more into their own growth during the first pregnancy. Growing up in mixed-sexed litters in comparison to female-only litters slowed down maturation in smaller but not the heaviest female within a litter and had no effect on female reproductive effort. Variation in reproduction of multiparous females was to a lesser extent explained by the initial relative size of siblings. Offspring survival to independence was high but slightly lower when mothers had been born as smaller sisters. Our results demonstrate that factors of the early family environment not only affect immediate offspring development but lead to long-term fitness consequences.