Behavioral Ecology最新文献

In birds, rearing multiple broods per season can substantially increase the annual number of fledglings produced. However, the contribution of double-brooding to lifetime fitness is unclear because the number of recruits arising from single- and double-brooded females is rarely measured. Poor estimates of fitness also make it challenging to document potential trade-offs between double-brooding and survival or future reproductive output. To understand the contribution of double-brooding to lifetime fitness and whether double-brooding was associated with life-history trade-offs, we used 30 years of reproductive data on female Savannah sparrows (Passerculus sandwichensis) breeding on Kent Island, New Brunswick. Estimates of fitness included an analysis of recruitment of both F1 (first generation) and F2 (second generation) offspring from females that did and did not raise a second brood. We detected no net costs of double-brooding. Double-brooded females had higher annual apparent survival rates than single-brooded females and F1 offspring from first broods of double-brooded females were more likely to recruit into the population than F1 offspring from single-brooded females. Double-brooding also improved lifetime fitness. Recruitment of F1 offspring was positively related to the number of seasons that a female double-brooded and, as a result, there was a higher number of F2 recruits from F1 offspring arising from double-brooded females than from F1 offspring arising from single-brooded females. Our results provide strong evidence that double-brooding is a beneficial reproductive strategy for Savannah sparrows and suggests that double-brooding females are likely high-quality individuals capable of rearing two broods a season with no net fitness costs.

Parasites often have a large impact on their hosts and can alter host phenotype to increase their own fitness, a phenomenon known as extended phenotype. Studies demonstrating extended phenotype for non-trophically transmitted parasites are scarce. Unionid mussels have a parasitic life stage adapted to parasitize fish which can affect host behavior, habitat use and growth rates, raising the question if parasitic freshwater mussels can also manipulate their host fish to compensate for downstream dispersal and to reach habitats favorable for newly excysted juvenile mussels. Wild-caught, parasite-naïve juvenile brown trout (Salmo trutta) were PIT-tagged, and half of the individuals were infested with parasitic larvae from the freshwater pearl mussel (Margaritifera margaritifera), all individuals were then returned to their home stream. During the following year, trout were tracked to investigate movement and habitat use, and also periodically recaptured to measure growth and body condition factor. The infested trout showed significantly higher upstream movement than non-infested trout and were more often recaptured in stream sections with slow-moving shallow water, particularly during the parasite excystment period (270 d post infestation). These data suggest that the juvenile mussels were successfully transported an average of 170 m upstream from the host trout release points to stream sections favorable for adult mussels. Infested trout survived as well as the non-infested, but had a significantly lower specific growth rate than non-infested trout. These results indicate a first example of extended phenotype in unionid mussels and highlight the importance of understanding glochidia-induced changes to host fish behavioral ecology.

Acoustic communication is vital for many animal taxa. Many songbirds have elaborate communication systems and large vocal repertoires consisting of learned, complex songs, and calls that are usually simpler in structure. While the functions of songs have been well researched, the functions of bird calls are often difficult to deduce from the context. A well-known example is the "rain" call of the common chaffinch (Fringilla coelebs): although chaffinches are very common and "rain" calls are conspicuous and frequent, the function of this call is still a mystery. It has been proposed to serve such diverse functions such as song substitute in territorial contests, predator alarm call, or within-pair coordination. Here, we systematically tested these hypothesized three functions, using a combination of two playback experiments and field observations. We found that chaffinches did not react to "rain" call playbacks with the same aggressive behavior as to song playbacks. Predator vocalizations, however, consistently elicited "rain" calls. In addition, when a female was visible, male chaffinches used "rain" calls more often both during predator simulation and in the actual presence of predators. Since the "rain" call is only uttered during the breeding season and it is associated with the presence of a female and predators, we propose that the "rain" call is a specific alarm call used in the context of defense against nest predators.

Cognition is a complex trait with multiple components that may vary independently or in concert. Thus far, we know little about how geographic differences in behavior are linked with different aspects of cognition. Behavioral differences could be linked with cognition in three ways: with multiple aspects of cognition, some but not other aspects of cognition, or no cognitive differences. Here, we compare cognitive performance in two populations of Polistes fuscatus wasps that differ in their capacity for individual face recognition. Individual recognition involves keeping track of multiple individual relationships and responding appropriately, so it is thought to increase social complexity. As a result, we predicted Michigan wasps that use individual recognition may have better cognitive performance than Pennsylvania wasps that are not able to individually recognize conspecifics. We find that Michigan wasps are more adept at individual face learning than Pennsylvania wasps. However, the populations perform similarly on other cognitive tasks, including color learning and memory, reversal learning, and odor learning and memory. Therefore, population differences in social behavior affect individual face learning, but are not linked with generalized differences in cognition. These findings suggest that socially complex societies may influence the evolution of social cognition specifically.

Floaters are non-breeding individuals that lack a territory or a breeding site. In many species, they can be seen visiting the territories of conspecifics before obtaining their own breeding site. Prospecting behavior is hypothesized to benefit floaters through information acquisition, enhanced site familiarity and dominance over other floaters. Here, we used detections of PIT-tagged male floaters in a population of spotless starlings (Sturnus unicolor). We investigated how floater activity varied across breeding stages and how their visits influenced subsequent nest site selection. We also tested whether distance, reproductive success, and phenotype and fate of the former owner influenced final settlement. We found that floater activity increased during the nestling-rearing period as nestling age increased. Floaters were more likely to breed near the area where they had been detected the previous year, suggesting that prospecting allows males to secure a foothold in their future settlement area. Although prospecting was higher in nests with a higher number of nestlings, neither breeding success, phenotype, nor provisioning rate of the last owner were related to nest choice, suggesting that public information is not used by males to decide where to settle. However, we found that floaters were more likely to breed in nest boxes where the previous owner had disappeared from the colony, suggesting that visits by male floaters in this species allow them to detect new vacancies. Our results suggest that prospecting might serve several non-mutually exclusive functions. Further studies in non-saturated colonies could shed light on the functional aspects of prospecting.

In variable environments, animals can change their reproductive behaviors and physiology to maximize reproductive returns. Natural environments vary in multifaceted ways, and animals may need to integrate multiple social or physical cues to adopt the most effective behavioral strategy. In a fully factorial 2 × 2 × 2 experiment, we exposed males to three factors: the number of rivals (10 or 30), food availability (present/absent) and mechanical shaking (present/absent). After 60 min of exposure, we recorded the male's mating latency, copulation duration and the number of offspring produced after a single mating. We also noted the latency of the males partner to remate with a stock male 24 h later. When rival number was increased from 10 per vial to 30 per vial, males sired more offspring. Males also varied their copulation duration and mating latency in response to the number of rivals, but in a condition-dependent manner. In the absence of vortexing, males mated for a shorter time when kept with 30 rivals, but the opposite was observed when males were vortexed. When males were fed and held in groups of 30, they took longer to begin mating compared to the other treatments. Our findings are consistent with the idea that male Drosophila integrate social cues to respond to levels of sperm competition and plastically allocate their ejaculate, but we have demonstrated that they can occur more rapidly (1 h) than previously thought (>24 h). Overall, our data highlight that combinatorial approaches can reveal new relationships between environment and behavior.

Color polymorphisms in natural populations often reflect the interplay between various selective pressures, such as natural and sexual selection. In this study, we investigate the dynamics of sexual selection operating on color polymorphism in wood tiger moths under different ecological contexts. Wood tiger moths exhibit polymorphism in male hindwing coloration, with individuals possessing one or two dominant W alleles displaying two forms of white coloration that differ in their UV reflectance (WW, Wy), while those with two recessive y alleles exhibit yellow coloration (yy). Females carry the color alleles, but do not express them phenotypically. We performed two mate choice experiments that simulated two ecological conditions: one with limited morph availability and low male encounter rates and the other with all morphs present and high potential for male encounters. We demonstrate that WW males experience higher overall mating success compared to yy males, irrespective of the presence of Wy males and male encounter rates. Surprisingly, mating with a WW male does not confer direct reproductive benefits to females in terms of lifetime reproductive success; instead, Wy females exhibit overall higher reproductive success regardless of their mating partner. Although the precise mechanism driving the higher mating success of WW males remains unclear, a temporal decline in mating success of WW males indicates potential differences in male mating strategies. Our findings suggest that despite the higher mating success of homozygote white males over homozygote yellow males, polymorphism likely persists due to the reproductive advantage of heterozygous individuals or other balancing selective forces.

To maximize their fitness, animals must often discriminate between stimuli differing in magnitude (such as size, intensity, or number). Weber's Law of proportional processing states that stimuli are compared based on the proportional difference in magnitude, rather than the absolute difference. Weber's Law implies that when stimulus magnitudes are higher, it becomes harder to discriminate small differences between stimuli, leading to more discrimination errors. More generally, we can refer to a correlation between stimulus magnitude and discrimination error frequency as a magnitude effect, with Weber's law being a special case of the magnitude effect. However, the strength and prevalence of the magnitude effect across species have never previously been examined. Here, we conducted a meta-analysis to quantify the strength of the magnitude effect across studies, finding that, on average, perception followed Weber's Law. However, the strength of the magnitude effect varied widely, and this variation was not explained by any biological or methodological differences between studies that we examined. Our findings suggest that although its strength varies considerably, the magnitude effect is commonplace, and this sensory bias is therefore likely to affect signal evolution across diverse systems. Better discrimination at lower magnitudes might result in signalers evolving lower magnitude signals when being discriminated is beneficial, and higher magnitude signals when being discriminated is costly. Furthermore, selection for higher magnitude signals (eg sexual ornaments) may be weakened, because receivers are less able to discriminate as signal magnitudes increase.

Long-lived species must balance allocation between reproduction and self-maintenance, and such a trade-off is expected to affect their foraging behavior. A bimodal foraging strategy, where individuals alternate between long trips for self-maintenance and short trips for offspring provisioning, may reflect this compromise. Using tracking data collected over three breeding seasons, we investigated the occurrence of a bimodal foraging strategy and inter-annual variation in foraging decisions among black-legged kittiwakes (Rissa tridactyla) breeding in Kongsfjorden, Svalbard. Kongsfjorden, a glacial fjord with six tidewater glacier fronts, provides close foraging opportunities to breeding sites. The continental shelf break outside the fjord offers another foraging area but involves higher commuting costs. We tested the hypothesis that breeding adults perform foraging trips outside the fjord for self-maintenance. We predicted that (1) adults were more likely to undertake foraging trips outside the fjord when their body condition was low and that (2) individuals foraging outside the fjord were likelier to improve their body condition than those foraging within. Our results indicate that kittiwakes in Kongsfjorden may adopt a bimodal foraging strategy during chick-rearing, but not every year. Contrary to our first prediction, we found no evidence that adult body condition affected the probability of foraging at distant sites. However, adults were more likely to maintain or improve body condition during outside-fjord foraging trips, supporting the hypothesis that long-distance trips can be used for self-maintenance. Overall, our results suggest that bimodal foraging is not a fixed characteristic of kittiwake foraging behavior and may be influenced by environmental conditions.

In many animals, a phenomenon is often observed in which behavior depends on population density and many individuals within the group synchronize their state of behavior to some extent, and theoretical studies have suggested that this synchronization phenomenon is adaptive for predation avoidance. Moreover, death-feigning behavior (DF) has been observed as an anti-predator strategy in many animals. There are large individual differences in the duration of DF, and the optimal duration of DF often varies depending on the situation. Therefore, although it is expected that prey may synchronize with others around them for an optimal DF duration, there are few experimental studies testing this hypothesis. This study investigated whether DF duration varies with and without other individuals, and whether it synchronized with the DF duration of other individuals, in the red flour beetle Tribolium castaneum. This study used populations with genetically longer (L-population) and shorter (S-population) DF duration and measured DF duration when maintained alone and cohabitated with individuals from the L- and S-populations, respectively. The results showed that the DF duration of individuals living alone increased significantly compared to pretreatment. Moreover, individuals that cohabitated with S populations were significantly shorter after cohabitation, but the presence of the L population did not cause any changes in how individuals synchronized their activities. When many individuals had shorter DF durations, DF was synchronized towards shorter durations. This is the first study to illustrate the synchronization of anti-predator behavior in terms of DF behavior.