Many animals assess their risk of predation by listening to and evaluating predators' vocalizations. We reviewed the literature to draw generalizations about predator discrimination abilities, the ...retention of these abilities over evolutionary time, and the potential underlying proximate mechanisms responsible for discrimination. Broadly, we found that some prey possess an ability to respond to a predator after having been evolutionarily isolated from a specific predator (i.e., predators are allopatric) and that some prey are predisposed to respond to certain types of predators that they coevolved with but without having ecological experience. However, these types of studies are lacking, and relatively, few studies have examined predator discrimination abilities in ungulates. To begin addressing these knowledge gaps, we performed field experiments on Mule deer (Odocoileus hemionus) in which we investigated the ability of deer to discriminate among familiar predators coyotes (Canis latrans) and mountain lions (Puma concolor) and an evolutionary relevant predator with which deer have had no recent exposure locally extinct wolves (Canis lupus). We found that Mule deer respond to and discriminate among predators based on predator vocalizations and have retained an ability to respond to wolves that have been extinct from the study area since the early 20th century. Previous playback studies have shown that responses vary among human‐habituated and non‐habituated populations and differ according to human proximity. Deer greater than 0.5 km from human residences allocated more time to heightened responses both before and after stimulus playback. Our findings may help predict how prey–predator interactions may change as a result of the recovering wolf population with a basis in ecological and evolutionary experience in predator discrimination and desensitization.
The activity rhythm of a species is ruled by internal signals as well as external factors. Among them, ambient temperature strongly influences the amount, duration, and distribution of an organism's ...activities throughout the day. The result is a pattern of activity that, between certain limits, can be flexible to deal with seasonal and spatial thermal heterogeneity. The range of behavioral plasticity increases with environmental variability and could be beneficial for a species' persistence under novel conditions. Thus, the goal of this study was to experimentally explore the behavioral plasticity in Phyllotis xanthopygus, a rodent species inhabiting an altitudinal gradient in the Central Andes Mountains of Argentina. In the laboratory, we assessed activity rate and pattern under different temperatures by comparing groups of individuals collected at different altitudes. All animals were acclimated to subsequent thermal treatments in a paired design. As expected, P. xanthophygus showed changes in activity under different temperatures, and animals from diverse altitudes were differently affected. In particular, animals from mid‐altitudes and high altitudes reduced their activity under high temperatures. Intraspecific differences across the altitudinal gradient suggest that animals from mid‐altitudes and high altitudes are less heat tolerant than those from lower sites, in spite of acclimation to equal conditions. We propose that climate ranges experienced in the field possibly promote this different response. Our results are discussed in light of recent forecasts of temperature rises in the region, which could constrain P. xanthophygus activity in space and time.
Behavioral ecologists are increasingly interested in patterns of repeatable variation in behaviors. The study of this variation, under the label ‘animal personality’, frequently makes assumptions ...both in regards to what the ecological significance of particular behavioral responses might be and whether different methodologies in fact test the same behavior. Here, using house crickets (Acheta domesticus), we tested whether stereotypical approaches to quantifying repeatable variation in exploratory behavior measured the same behaviors. We found that house cricket exploratory behavior was highly repeatable in two populations (repeatability: 0.37–0.51). However, exploratory behavior across two different testing methods was not strongly correlated (r = −0.17 to 0.14). This suggests that either different behaviors or distinct components of exploratory behavior were being measured. Our results also support recent criticisms that care needs to be taken in describing personality traits.
Changes in adult body mass during breeding can reveal how parents prepare energetically for care, the stress of care, and the need to terminate care in a state conducive for future reproduction. ...Interpreting changes in parent mass can be difficult, however, because temporal variation in body mass may reflect a constraint imposed by the stress of care, revealing conflict within the family, or a shift to a new body mass optimum adaptive for a different stage of the breeding cycle. Here, we examined the effect of food deprivation and parenting on variation in female body mass of Nicrophorus orbicollis, an insect in which parents and offspring share a common food resource (a prepared carrion ball). Female parents demonstrated a remarkable degree of regulation of body mass: Despite varied periods of food deprivation (0–8 d) prior to discovery of a carcass, females attained a similar body mass (108.3–109.2% of pre‐deprivation mass) at the time of larval hatching. Females attained a greater body mass in anticipation of rearing a greater number of young. Mothers lost mass during active parental care, and mass at the end of caregiving was less in mothers that reared more and heavier young. Body mass at the end of care was less than the preferred mass for females searching for a carcass, indicating that the mothers sacrificed self‐maintenance and future reproductive potential for their current brood. Contrary to prediction, pre‐breeding food deprivation had no effect on offspring size or on female condition at the end of care. We conclude that there is a limited degree of conflict over the sharing of food among N. orbicollis parents and offspring, but that this conflict is not exacerbated by food deprivation prior to breeding.
Antipredator behavioral tactics have evolved in phylogenetically diverse animal clades and often involve prey initiating conspicuous display patterns when encountering potential predators. Using ...detailed behavioral observations in the field, we report the first description of conspicuous tail displays in juvenile collared lizards (Crotaphytus collaris), a species that does not have tail autotomy. When approached in the field, lizards gave four stereotypical displays involving the tail, suggesting that these might function as antipredator signals. To test this hypothesis, we compared the frequency of tail displays given by juveniles during approach experiments relative to control trials involving observation from afar. We then further manipulated the intensity (low threat, high threat) with which we threatened lizards by varying our angle of approach relative to the body‐axis orientation of lizards resting on a perch sloping away from the observer. Our results show that juveniles consistently performed all four types of tail displays in response to our approaches, but subjects never displayed during non‐threat control trials. Moreover, lizards were more likely to remain emergent and give tail displays when we approached them head‐on with their bodies sloping away (low threat), but were more likely to take refuge when approached from the side and behind (high threat). The positive relationship between the frequency of display and risk level suggests that tail displays function to signal that juvenile lizards have detected potential predators, which may deter further pursuit. Together, our results provide the first account of visual displays involving the tail in collared lizards and suggest that these displays function to signal potential predators.
Endocrine disrupting compounds (EDCs) enter aquatic habitats from a variety of anthropogenic sources and can mimic, block, or modulate the synthesis of natural hormones. EDCs affect both reproductive ...and non‐reproductive behaviors because hormones mediate responses associated with aggression and fear. We examined the effects of two EDCs on risk‐taking behaviors in guppies (Poecilia reticulata). We quantified risk‐taking in terms of propensity to forage in a risky location and tendency to join groups in the presence of a predator. We found that male and female guppies responded oppositely to environmentally relevant concentrations of an estrogenic EDC, 17α‐ethinylestradiol (EE2), or an androgenic EDC, 17β‐trenbolone (TB). Males decreased risk‐taking with increasing EE2 concentration (as predicted), but females increased risk‐taking (contrary to prediction). In contrast, females increased risk‐taking with increasing TB concentrations (as predicted), but males decreased risk‐taking (contrary to prediction). These results did not match our expectation that EE2 would reduce risk‐taking and TB would increase risk‐taking in both sexes. We suspect EE2 and TB produced these counterintuitive effects by downregulating their corresponding hormone receptors and thus reducing levels of circulating endogenous hormones in females and males, respectively. These results show that EDCs can alter fish behavior and potentially reduce fitness in unexpected ways.
Defense of a territory is a primary factor determining the fitness of territorial individuals. Thus, territorial animals use a variety of means to lower the cost of territorial defense. Although ...landmarks are known to lower the defense costs of territories, little is known about how they could affect fundamental properties of territories, which could ultimately affect the demography, population regulation, individual behavior, and spatial ecology of a territorial species. This field study examined the effects of natural landmarks on territory size, shape, and defensive costs in Amatitlania siquia, a little‐studied member of the convict cichlid group native to Costa Rica and Nicaragua. We investigated the territorial behavior of 103 breeding pairs in a caldera lake in Nicaragua. During 10‐min focal observations, we recorded the locations at which residents chased intruders and then used these locations to outline the territory boundaries. Landmarks affected both size and shape of A. siquia territories. Territory size decreased as the percentage of the boundary at landmarks increased. Territories with <20% of their boundaries at landmarks were approximately circular in shape, while territories with 20–60% of their boundaries at landmarks were on average more elongated. These variations in territory size and shape significantly affected defense costs, with higher numbers of chases per square meter in small and elongated territories. These effects of landmarks on territory size and shape and defense costs are useful to understand the widely seen size and shape variations in naturally occurring territories.
Communication between social animals is often more effective when signals facilitate individual recognition. Two critical requirements for individual recognition are the occurrence of characteristics ...that are unique to each individual, and the consistency of these characteristics through time. In some animals, characteristics of acoustic signals are known to vary over time due to changes in a variety of factors, including physiological and environmental features. Such temporal variation requires careful evaluation when exploring the individual distinctiveness of animal signals. In this study, we evaluate individual distinctiveness in the songs of male white‐eared ground‐sparrows Melozone leucotis and the persistence of distinctive characteristics over time. We collected focal recordings from populations of banded ground‐sparrows during two consecutive breeding seasons, including multiple recording sessions within each breeding season. We evaluated individual distinctiveness in fine structural acoustic features of songs. We also extended our analysis to repertoire characteristics, focusing on whether the relative frequency of song type use may provide cues to individual identity. We found that each male white‐eared ground‐sparrow sang individually distinctive songs, although their fine structural features varied between recording sessions. We found the frequency with which males sang different song types was also individually distinctive, and this feature varied little between recording sessions. Receivers may be able to use these distinctive characteristics to differentiate individuals over extended time periods; this may be especially important for species that engage in long‐term social interactions, such as tropical birds that defend territories against rival conspecific animals throughout the year.
Whether play occurs in fishes has long been a contentious issue, but recent observations document that social, object, and locomotor play can all be found in some species of teleosts. However, ...quantitative studies and those documenting individual differences are rare. We recorded hundreds of occurrences of an unusual behavior in three male Tropheus duboisi. The target behavior of attacking and deflecting an object that rapidly returned to its upright position not only fit the criteria for play behavior, but differed quantitatively and qualitatively among the individuals. This behavior has not been observed in other species of cichlids and other kinds of fishes. The presence or absence of food or other fish either within the aquarium or visible in an adjacent aquarium had no marked or consistent effect on the occurrence of the behavior. Various explanations for the origin and function of the behavior are discussed.
An increase in habitat complexity is thought to decrease visibility and the territory size of visually oriented animals. Hence, the addition of physical structure has been viewed as a useful ...restoration technique to increase the density of territorial species, particularly in stream fishes. However, a decrease in territory size may have a negative effect on the fitness of individual organisms. We attempted to quantify some of the positive and negative effects of increasing habitat structure on the behaviour and growth rate of wild young‐of‐the‐year (YOY) Atlantic salmon. Fish were exposed to one of two habitat treatments in mesh enclosures in Catamaran Brook, New Brunswick: a gravel substrate (low complexity) or a gravel substrate with boulders added (high complexity). Wild‐caught individuals were tagged, weighed and measured before being stocked at densities of 1·m⁻² for 7‐d trials. While fish from high‐complexity treatments benefited from lower rates of aggression, they also had lower foraging rates and smaller territories compared to those in low‐complexity treatments. Specific growth rate, however, did not differ significantly between treatments. While the addition of structure to a habitat may be beneficial at the population level in terms of an increase in population density, our results suggested that individual fish may pay some short‐term costs in these environments. Further research is needed to evaluate the longer term costs and benefits of adding structure to improve the habitat quality for stream salmonids.
