Behavioral Ecology最新文献

Environmental conditions and experiences during development can have long-term fitness consequences, including a reduction of adulthood survival and reproduction. These long-term fitness consequences may play an important role in shaping the evolution of life history. We tested two hypotheses on the long-term fitness effects of the developmental environment-the silver spoon hypothesis and the internal predictive adaptive response (PAR) hypothesis. We compared the change in annual survival and annual reproductive output with age for adult birds hatched and/or reared in poor--impacted by anthropogenic noise, and/or high sibling competition--and good--not impacted by anthropogenic noise, and/or low sibling competition--environments. We used a 23-year longitudinal dataset from a wild house sparrow (Passer domesticus) population inhabiting an isolated island, which enabled near-complete monitoring and unusually accurate lifetime fitness estimates. We used a cross-fostering setup to disentangle environmental effects experienced postnatally from those experienced prenatally. We found that adults that, as chicks experienced more within-brood competition had a stronger increase in early-life annual survival, but also a stronger decrease in late-life annual survival. Females that hatched in a noisy environment produced fewer genetic recruits annually, supporting a sex-specific silver spoon hypothesis. Males reared in a noisy environment had accelerated reproductive schedules, supporting a sex-specific internal PAR hypothesis. Our results highlight that anthropogenic noise (∼68 dB from power generators) can have long-term fitness consequences in wild animals, altering their life-history strategies, and that effects may be sex-specific.

During mate choice, choosers are exposed to a variety of sexual signals varying in both magnitude and the environment in which they are experienced. Previous work assumes that choosers evaluate signal variation from potential mates that are simultaneously viewed and compared. However, this is an extreme scenario, and it is important to also consider sequential presentation of mates, as most animals likely experience both scenarios during mate choice. Using green swordtail fish (Xiphophorus hellerii), we assessed whether female preferences for larger males differed when males of different sizes were experienced simultaneously or sequentially. We also investigated the perceptual mechanisms of comparison in both contexts, given recent research suggesting that female preferences are often nonlinear. We found that females consistently preferred larger males, irrespective of whether males were experienced simultaneously or sequentially. However, female preferences were stronger for a male of a given size when viewed under simultaneous, compared with sequential, conditions. During sequential presentation, females compared information from both previously and currently presented males, and interest did not decay with subsequent presentations. Previous research has demonstrated that female green swordtails assessing males simultaneously attend to the relative size difference between males, but we found no evidence of any comparative size assessment. Our study demonstrates that when designing mate choice experiments, it is important to consider how females encounter potential mates in the wild, highlighting that there are clear differences in preferences due to methods of mate presentation and that stochastic adjusting of internal standards of quality frequently occur.

Although defending a territory may benefit individuals by allowing them to retain important resources, the time and energy costs associated with territory defense may lead territory owners to neglect other reproductively important behaviors. In this study, we assessed the potential tradeoff between territory defense and parental care in 4 Darwin's finch species on Floreana Island, Galápagos. Using song playback, we simulated territory intrusions to measure male aggressiveness across multiple stages of the breeding cycle (unpaired, paired, incubating, and chick feeding). To quantify parental care at each nest, we conducted 1-h observations to record the frequency of male food deliveries and the duration of female incubation and brooding. Male aggressiveness toward a perceived intruder did not change across the breeding cycle and was highly repeatable (adjusted R = 0.597), although responses became less vocal across the breeding cycle. A male's aggressiveness did not predict his frequency of food deliveries during incubation or chick feeding, although females paired with more aggressive males spent significantly less time incubating. This finding provides weak evidence for a tradeoff between territory defense and parental care, although the behavioral mechanisms mediating this relationship remain uncertain. Finally, males with aggressive and nonaggressive behavioral phenotypes did not differ in their hatching success, although additional work is needed to assess other measures of individual fitness.

As the global climate changes, temperatures are rising, snow is melting earlier, and rainfall is becoming more variable, and these climatic changes may create an ecological mismatch. While prior work has shown how animals respond to these changes physiologically and behaviorally, few have specifically investigated antipredator behavior, an essential activity. In many species, there are direct fitness tradeoffs between allocating time and energy to antipredator vigilance and foraging. To discover how these tradeoffs are affected by climate change, we studied how temperature, snowmelt date, and rainfall affected the proportion of time yellow-bellied marmots (Marmota flaviventer) allocated to vigilance during bouts of foraging. While snowmelt and temperature did not explain variation in vigilance, rainfall did. Higher rainfall in the week prior to a focal observation was associated with higher vigilance, possibly reflecting more abundant food that affords the luxury of increasing antipredator vigilance while foraging. Such an effect might be consequential at the population level given the importance of foraging and antipredator behaviors for a highly time restrictive hibernating species. Further research is necessary to determine consequences at the population level and whether and how these findings extend to other species.

Humans impact wildlife positively and negatively, and increasing evidence shows that humans potentially play a major role in shaping urban wildlife cognition. However, it remains unclear which, and how specific anthropogenic factors, shape animal cognitive performance. Here, across 15 urban areas in Oulu, Finland, we investigated how varied levels of human presence nearby, types of human activity (walking, dog-walking, cycling, and playground activities), and distance to the nearest footpaths influenced 64 squirrels' innovative problem-solving ability-measured as the proportion of solving success at the site level, solving outcome at the individual level as well as individuals' first-success latency. Higher mean human presence nearby and all measured human activities significantly decreased the proportion of success at the site level. Playground activity showed the highest negative impact on both the first- and subsequent-visit success rate at the site level. Increased mean human presence and walking decreased the likelihood of a squirrel successfully solving the novel food-extraction problem. When examining the problem-solving latency of individual squirrels, increased human presence also decreased squirrels' first-success latency, and dog-walking was the outstanding factor affecting first-success latency. These results show the negative effects of specific human-related factors on an important cognitive trait, problem-solving ability. These factors may also potentially exert selective pressure on shaping urban wildlife cognition.

We studied the effect of a demonstrator on the learning of a novel foraging task in 12 groups of free-living cooperative breeding Arabian babblers (Argya squamiceps). We allowed naïve babblers to forage jointly on a foraging grid with a demonstrator previously trained to solve a task in one of 2 possible methods: lifting covers of 1 color or pecking through covers of another color. We found that most group members learned to solve the task using one of the methods, and persisted with it even when later tested with covers of a third (neutral) color that could be opened by both lifting and pecking. However, the method learned by group members did not necessarily follow the method used by the pre-trained demonstrator. Instead, learners within each group tended to use the same method (significantly more than expected by chance), and the extent to which groups differed from the demonstrator was correlated with the extent to which the demonstrator occasionally (and quite rarely) exhibited also the alternative method. These results, together with further analysis of the sequence of events in each group, suggest that both naïve birds and demonstrators learn socially from each other, as well as through individual trial-and-error learning, which enables naïve individuals to become demonstrators themselves and influence the pattern of social transmission. This process mostly leads to a homogenous group behavior, but one that cannot be predicted by the seeded demonstration.

The three-dimensional (3D) structure of habitats influences how prey detect and respond to predators, but the specific roles of different aspects of structural complexity remain poorly understood, particularly in coral reef ecosystems. We used 3D models of 3 Caribbean reef sites to quantify 3 structural metrics at site level: field of view (the extent of observable area), refuge density (density of holes), and rugosity (reef surface roughness). We then observed the anti-predator behavior of damselfish, parrotfish, and wrasses at each site. Territorial damselfish showed species-specific responses to habitat structure, especially in relation to field of view. Stegastes adustus, for example, exhibited shorter flight initiation distances (FIDs) at the site with the highest field of view, consistent with expectations from optimal escape theory. In contrast, wrasse and parrotfish species showed little variation in behavior across sites, though larger individuals tended to have longer FIDs and flight distances. Refuge density was similar across sites, likely reflecting long-term regional loss of fine-scale complexity in the Caribbean. While rugosity is widely used as a proxy for reef complexity, our results suggest that field of view may be more strongly associated with differences in anti-predator behavior, particularly in damselfish. These findings highlight the need to assess multiple dimensions of habitat structure, as even closely related species may exhibit distinct behavioral adaptations to their 3D environment.

Birds in some species produce 2 broods in a season to maximize reproductive success, but in species such as the northern house wren (Troglodytes aedon), not all individuals produce a second brood even if they have enough time to do so. We investigated whether variation in individual quality, in addition to time-of-season, explains some of the variation in the likelihood of producing a second brood. We examined the effects of individual age, body condition, and territory quality, and estimated the repeatability of producing a second brood using breeding records from a long-term dataset. We also cross-fostered eggs between earlier-nesting females (presumed high quality) and later-nesting females (presumed low quality) to delay or advance the natural nesting date, exposing an effect of quality if present. There was little evidence that the individual traits measured affected the production of a second brood. Cross-fostered, delayed females did not differ from the control in their likelihood of producing a second brood, but advanced females were more likely to produce a second brood compared with the control. However, the production of a second brood was significantly repeatable, and this repeatability was substantially higher after accounting for variation in the timing of the first brood. This suggests that individual characteristics, in addition to time-of-season, have a substantial effect on the likelihood of producing a second brood, but that further studies are needed to identify the specific traits responsible for this effect.

When moving, animals are vulnerable to predation because movement can rapidly attract the attention of a predator. To reduce the risk of predation while moving, animals can use a variety of different strategies (eg erratic movement, coloration). These strategies often work in combination or may be influenced by other prey characteristics (eg size), but few studies have explored these interactions. Here, we investigate how movement trajectory (linear or erratic), prey size (small or large) and prey coloration (glossy or matte) interact to impact the attack behavior of giant rainforest mantids (Hierodula majuscula). We presented mantids with animations of moving targets and filmed their response with a high-speed camera. As expected, mantids were more likely to track large than small targets and targets moving linearly than erratically. Counterintuitively, however, mantids were quicker to strike at erratically moving targets, perhaps because they more closely resembled preferred prey. When mantids attacked the target, their accuracy was influenced by the interaction of target trajectory and glossiness. As predicted, mantids had larger attack errors (ie lower accuracy) toward erratically moving glossy targets compared with linearly moving glossy targets or erratically moving matte targets. However, contrary to our prediction that linearly moving matte targets would be easiest to capture, these targets also elicited large attack errors, similar to those recorded for erratically moving glossy targets. Together, our results demonstrate that anti-predator tactics for prey in motion may interact in complex ways, and simple experimental scenarios may overlook context-dependent effects that emerge when multiple factors interact.

To maximize their reproductive fitness, females of many polyandrous species should display mating status-dependent choice, where they mate relatively indiscriminately once to ensure reproductive output, and then become choosy and mate preferentially with higher-quality males. Despite this potential contrast in choosiness, most mate choice experiments use virgin females. Here, using a panel of 20 isofemale strains that originated from wild-caught flies, we allowed virgin and non-virgin Drosophila melanogaster females to choose among males from the same panel of strains. We used single-male latency trials and a series of male competition trials to help disentangle female "choices" from male-male competitive effects. Most virgin females mated within 2 h of males being introduced, compared with fewer than half of non-virgin females mating over the same period. However, despite mating more rapidly, virgin females did not mate indiscriminately, and their "choices" strongly aligned with those of previously mated females across both the single-male latency and male-male competition trials. Our results challenge the idea that virgin females mate relatively indiscriminately and show that female choice may be more stable than is generally appreciated.