Fitness costs of neighborhood disruption in translocations of a solitary mammal

Translocation is used to reestablish wild populations of animals, but translocation projects often do not meet their objectives because postrelease mortality of animals is high. One reason for translocation failure is that the behavioral or ecological requirements of released animals are unmet. Maintaining founder-group social relationships during release can affect reestablishment of social species. Solitary territorial species with stable neighbors (restricted dispersal and lifetime occupation of a home range) of the same species may also benefit from the maintenance of these social relationships during translocation. We translocated Stephens' kangaroo rats (Dipodomys stephensi), a solitary species listed as endangered under the U.S. Endangered Species Act, with and without neighboring kangaroo rats. We compared the settlement (establishment of a stable home range) decisions and fitness of kangaroo rats between the 2 treatments. Kangaroo rats translocated with neighbors traveled shorter distances before establishing territories, had higher survival rates, and had significantly higher reproductive success than kangaroo rats translocated without neighbors. Number of offspring was 24-fold higher for kangaroo rats translocated with neighbors than those translocated without neighbors. Differences in behavior following release may partially explain differences in survival between the 2 groups. Immediately following release, animals translocated with neighbors fought less and spent significantly more time foraging and digging burrows than animals translocated without neighbors. Our results indicate that even for solitary species, maintaining relationships among members of a translocated group of animals can influence translocation success. This study is the first empirical demonstration of the fitness consequences of disrupting social relationships among territorial neighbors.     

‘Optimal’ pollution abatement—whose benefits matter, and how much?

We examine the determinants of environmental regulatory activity (inspections and enforcement actions) and levels of air and water pollution for 409 US pulp and paper mills, using data for 1985–1997. We focus on the benefits to the surrounding population from pollution abatement. Plants with larger benefits emit less pollution, as do those with more kids and elders nearby. Plants in poor areas emit more pollution, though (surprisingly) we find less pollution in minority areas. Out-of-state neighbors seem to count less than in-state ones, although this effect diminishes if the bordering state's Congressional delegation is strongly pro-environment. We use ‘spatially lagged’ instrumental variables to control for the potential endogeneity of which individuals choose to locate near the plant. The results for regulatory activity are noticeably less significant than the emissions results.     

Social monitoring in a multilevel society: a playback study with male Guinea baboons

Keeping track of social interactions among conspecifics is a driving force for the evolution of social cognition. How social cognition, such as social knowledge, ties in with a species' social organization is, however, largely unexplored. We investigated the social knowledge of wild Guinea baboons (Papio papio) ranging in Senegal, a species that lives in a fluid multilevel society with overlapping habitat use. Using playback experiments, we tested how adult males differentiate between subjects from their own vs. a neighboring or a stranger social unit (“gang”) and assessed ranging patterns with Global Positioning System (GPS) data. While territorial species usually differentiate between group and nongroup members and often respond more strongly to strangers than neighbors (the “dear enemy” effect), subjects in this highly tolerant species should largely ignore other unit members and mainly attend to subjects from their own unit. Males responded strongly after playback of calls recorded from members of their own gang, while they attended only briefly to neighbor or stranger calls. Apparently, males benefit from monitoring the social maneuvers in their own social unit, while it remains to be resolved whether they are unmotivated or unable to keep track of the identities and actions of individuals outside their own gang. The study highlights how the allocation of social attention is tuned to the specifics of a species' social organization, while a complex social organization does not necessarily translate into the need for more elaborate social knowledge.     

Cuticular hydrocarbons correlate with fertility, not dominance, in a paper wasp, Polistes dominulus

Cuticular hydrocarbons (CHCs) are information-rich signals in social insects that coordinate behaviors within nests. However, in some taxa, the precise information conveyed by CHCs is poorly understood. In particular, there is a debate over whether CHCs convey information about their bearer's dominance or fertility. Distinguishing between dominance and fertility signaling is difficult because fertility and rank are frequently correlated within social insect colonies. This study disentangles those relationships by examining CHCs of Polistes dominulus paper wasps during the early nest-founding stage before dominance and fertility become correlated. First, we confirm that dominance and fertility are not associated in early spring foundresses. Then we show that CHCs are more strongly associated with fertility than dominance. There was no relationship between cuticular hydrocarbon profiles and a wasp’s ability to dominate rivals through aggression, suggesting that CHCs are unlikely to provide information about dominance. However, there was a significant correlation between ovarian development and the CHC profile, suggesting that CHCs could convey valuable information about their bearer's fertility. Furthermore, our data provide a potential mechanism for chemical signaling of fecundity, as there is a relationship between endogenous juvenile hormone titer (a gonadotropin), degree of ovarian development, and the CHC profile. Hormonal regulation of CHC profile expression offers a physiological mechanism to coordinate behavior, physical state, and signal expression.     

Proximate mechanisms of contest competition among female Bwindi mountain gorillas (Gorilla beringei beringei)

Socioecological models provide a framework for predicting how animals respond competitively to the abundance and distribution of food resources. Testing predictions of socioecological models requires analysis of relationships among food resource characteristics, competitive behaviors, and measures of rank-related skew in energy balance or reproductive success. A positive relationship between dominance rank and energy balance has been observed among female mountain gorillas in Bwindi Impenetrable National Park, Uganda. This study examines the proximate mechanisms underlying feeding competition among those females. To assess the contestability of food resources, we measured the time a female spent feeding at a food site (food site residence time). We also examined the relationship between dominance rank and the access to resources, as well as the rate, context, and direction of aggression, and the number of neighbors in close proximity. As predicted, females had longer food site residence times and higher aggression rates with fruit and decaying wood than with herbaceous vegetation, suggesting that those resources may be contestable. Aggression was predominantly directed down the dominance hierarchy, although against expectation, rank was not significantly correlated with aggression rates or the time spent feeding on contestable foods. Higher-ranking females had significantly fewer neighbors, suggesting that lower-ranking females avoid higher-ranking ones. This study provides additional support for the claim that there is variability in how primates respond to the quality and distribution of food resources and that avoidance as a strategy to cope with feeding competition may result in similar skew in energy balance as rank-related aggression.     

Determining the role of eudaimonic values in conservation behavior

Values are the fundamental reasons why people engage in conservation behaviors. Recent research has called for a more refined approach to studying values in a way that accounts for the concept of eudaimonia. However, the empirical properties for a eudaimonic value scale have not been tested given that previous investigations have remained at the theoretical level. Drawing from an on-site survey of visitors to Denali National Park and Preserve, Alaska, we used a latent profile analysis to better understand the expression of multiple values of nature. Specifically, we segmented respondents by their value orientations with a particular focus on evaluating eudaimonic and hedonic values, alongside the established dimensions of altruistic, biospheric, and egoistic values. We identified 4 distinct subgroups defined by value orientations and validated these subgroups based on measures of conservation behavior and sociodemographic characteristics (e.g., age). These results indicated campaign messaging should harness a combination of eudaimonic, biospheric, and altruistic values to propel individual behavior. We also observed that hedonic and egoistic values defined how people related to nature and played a role, albeit less pronounced, in motivating them to take action. Our study is one of the first efforts to operationalize eudaimonia in a conservation context; thus, we have opened a new avenue for protected-area managers to align their strategies with the underlying values of stakeholders.     

Social networks and models for collective motion in animals

The theory of collective motion and the study of animal social networks have, each individually, received much attention. Currently, most models of collective motion do not consider social network structure. The implications for considering collective motion and social networks together are likely to be important. Social networks could determine how populations move in, split up into and form separate groups (social networks affecting collective motion). Conversely, collective movement could change the structure of social networks by creating social ties that did not exist previously and maintaining existing ties (collective motion affecting social networks). Thus, there is a need to combine the two areas of research and examine the relationship between network structure and collective motion. Here, we review different modelling approaches that combine social network structures and collective motion. Although many of these models have not been developed with ecology in mind, they present a current context in which a biologically relevant theory can be developed. We argue that future models in ecology should take inspiration from empirical observations and consider different mechanisms of how social preferences could be expressed in collectively moving animal groups.     

Children of divorce: effects of adult replacements on previous offspring in Argentinean owl monkeys

According to the Evolutionary Theory of the Family, the replacement of one pair-member by an intruder may have profound consequences for the existing offspring. Step-parents are expected to provide less care towards unrelated immatures than to genetic offspring, unless caring also serves as a mating strategy. Furthermore, because an intruder will be a potential mate for opposite-sexed offspring, relationships between offspring and same-sex parents are predicted to deteriorate. To test these predictions, we studied an Azara’s owl monkey (Aotus azarai) population in Argentina exhibiting serial monogamy and bi-parental care. Since 1997, we have collected demographic data from ca. 25 groups and inter-individual distance data from ca. 150 marked individuals. First, we compared survival and dispersal age of immatures in groups with and without replacements to investigate whether parental care serves as a mating strategy. Second, we compared sex-specific age at dispersal for groups with replacement of opposite-sex parents, same-sex parents, or in stable groups in order to test whether relationships between offspring and same-sex parents deteriorated after the replacement of the other parent. Survival and dispersal ages were not negatively associated with replacements, suggesting that male care might serve, at least partly, as a mating strategy. The time lag between a replacement and the subsequent dispersal of female offspring was greater if the intruder was a male, while the offspring and same-sex parents were less often nearest neighbors after replacements than before. Our results suggest that family disruption through the replacement of a parent is not associated with decreased offspring survival or early dispersion of juveniles, but deteriorates parent–offspring relationships.     

Individual energetic state can prevail over social regulation of foraging in honeybees

The energetic state of an individual is a fundamental driver of its behavior. However, an individual in a eusocial group such as the honeybees is subject to the influence of both the individual and the colony energetic states. As these two states are normally coupled, it has led to the predominant view that behaviors, such as foraging, are dictated by the colony state acting through social regulatory mechanisms. Uncoupling the energetic state of an individual honeybee from its colony by feeding it with a non-nutritious sugar, we show that energetically stressed bees in a colony with full food stores do not consume this food to meet their energetic shortfall but instead compensate by first reducing their activity level and then by increasing their foraging rate. This suggests that foraging in eusocial groups is still partly under the regulatory control of the energetic state of the individual and supports the notion that regulatory mechanisms in solitary insects have been co-opted to drive altruistic behavior in eusocial insects. The observation that energetically stressed bees also experience higher mortality during foraging also suggests that energetic stress mediated by a variety of factors can be a common mechanism that underlies the recent observation of bees disappearing from their colonies. We also discuss how nutritional imbalance in a social insect individual can alter its behavior to influence colony life history.     

Male mating competitiveness and age-dependent relationship between testosterone and social rank in bighorn sheep

In males, the acquisition and development of behavioral and morphological secondary sexual traits typically depends on testosterone and correlates with mating success. Testosterone level could affect competition for mates and thus be a target of sexual selection. We sought to relate testosterone levels to male mating competitiveness, by teasing apart the relationships between testosterone, behavior, and growth before the mating period. We monitored 24 adult bighorn rams (Ovis canadensis) at Ram Mountain, Alberta, from 2008 to 2011. Using linear mixed models, we tested the relationships between testosterone metabolites in feces, social rank, and both growth and size of two sexually selected traits: horns and body mass. The correlation between testosterone and social rank varied with age. Testosterone and rank were weakly and negatively correlated for young rams, positively correlated for prime-aged rams, and negatively correlated for older rams. Although testosterone had an increasingly positive effect on total horn length until 8 years of age, we could not detect any effects on annual growth rate of horns or body mass. Testosterone may be related to male’s ability to compete for mates through its relationship with behaviors determining social rank, rather than by influencing the development of morphological traits. Differences in testosterone levels among competitors may be a proximate cause of variance in fitness.     

Use of different signaling modalities to communicate status by dominant and subordinate Heermann’s kangaroo rats (<Emphasis Type="Italic">Dipodomys heermanni</Emphasis>)

Dominance relationships in solitary species may be an important factor in the maintenance of long-term, stable relationships among territorial neighbors. We examined the mediation of intraspecific interactions in a solitary, territorial kangaroo rat, Dipodomys heermanni, and tested whether unfamiliar kangaroo rats establish a dominance hierarchy and then decrease aggression and increase communication (via footdrumming and sandbathing) after initial interactions and the establishment of a social structure. Results revealed that both dominance hierarchies and familiarization with particular individuals are likely to mediate social interactions. After only one pairing per dyad, an almost linear dominance hierarchy emerged, which became perfectly linear after a 90-min familiarization period. During the course of subsequent interactions between dyad partners, fighting decreased and non-agonistic communication increased. Dominant kangaroo rats sandbathed at higher rates than subordinates, possibly to deposit scent to advertise competitive ability, whereas subordinate kangaroo rats footdrummed from inside the burrow, which seemed to indicate an unwillingness to interact. We suggest the kangaroo rats use a conditional strategy when deciding to fight (be dominant) or withdraw (be subordinate) by employing different modes to communicate status and minimize the potential risk of injury during unnecessarily prolonged fights.     

Measuring diversity: the importance of species similarity

Realistic measures of biodiversity should reflect not only the relative abundances of species, but also the differences between them. We present a natural family of diversity measures taking both factors into account. This is not just another addition to the already long list of diversity indices. Instead, a single formula subsumes many of the most popular indices, including Shannon's, Simpson's, species richness, and Rao's quadratic entropy. These popular indices can then be used and understood in a unified way, and the relationships between them are made plain. The new measures are, moreover, effective numbers, so that percentage changes and ratio comparisons of diversity value are meaningful. We advocate the use of diversity profiles, which provide a faithful graphical representation of the shape of a community; they show how the perceived diversity changes as the emphasis shifts from rare to common species. Communities can usefully be compared by comparing their diversity profiles. We show by example that this is a far more subtle method than any relying on a single statistic. Some ecologists view diversity indices with suspicion, questioning whether they are biologically meaningful. By dropping the naive assumption that distinct species have nothing in common, working with effective numbers, and using diversity profiles, we arrive at a system of diversity measurement that should lay much of this suspicion to rest.     

Complex social structure of southern flying squirrels is related to spatial proximity but not kinship

Social individuals have organized relationships that affect fitness and so a species' tendency to be social has important implications for its population ecology, gene flow, and its distribution in space and time. We quantitatively examined the social structure of southern flying squirrels (Glaucomys volans) and tested for a role of kinship and prior familiarity in predicting social structure. To quantify social structure, we monitored nest group composition of southern flying squirrels. All squirrels at the study site were marked with passive integrated transponder (PIT) tags and nest cavity entrances were monitored with automated PIT tag recorders for a period of 28 months. Squirrels were genotyped at eight microsatellite loci. Permutation tests of associations suggested that individuals nested with other specific individuals more often than expected by chance. The lagged association rate indicated that relationships were stable and persisted across seasons and years. Multiple summer nest associates came together in winter to form larger nest groups which were likely important for social thermoregulation. A measure of prior familiarity, but not kinship, was related to the proportion of time individuals nested together during winter. We suggest that the evolution of sociality in southern flying squirrels is driven largely by mutually beneficial behaviors related to social thermoregulation although other, as of yet, unidentified mechanisms are needed to explain sociality in the warm season. We hypothesize that minimum group size requirements associated with social thermoregulation could explain the absence of this species in patchy landscapes and aspects of range boundary dynamics near their northern range boundary.     

On the social structure of offspring rearing in the burrower bug,<Emphasis Type="Italic"> Sehirus cinctus</Emphasis> (Hemiptera: Cydnidae)

Maternal-offspring interactions are important in a variety of animals. Understanding the evolution of these interactions requires that we also study the broader social context in which they occur. To date, behavioral studies on burrower bugs, Sehirus cinctus, have focused exclusively on interactions between mothers and offspring. Here we ask whether these interactions occur in a social context that extends beyond the family unit of a mother and her own genetic offspring. Such social structure can arise from behaviors that occur before eggs are laid, or from actions of individuals that occur post-hatching. We present field data showing that lay sites of mothers are spatially aggregated on a scale that would lead to behavioral interactions among families. Microsatellite markers suggest neighboring mothers are unrelated. Laboratory experiments do not support the hypothesis that spatial aggregation results from a direct attraction of females to one another. Other laboratory studies reported here indicate that, after hatching, unrelated clutches sometimes join together to form multifamily groups. Experiments reveal that mothers are not necessary for these joining events to occur. In sum, these data suggest that both mothers and offspring play active, but different, roles in generating the social environment in which offspring rearing occurs.Communicated by N. Wedell     

Behavioural trait assortment in a social network: patterns and implications

The social fine structure of a population plays a central role in ecological and evolutionary processes. Whilst many studies have investigated how morphological traits such as size affect social structure of populations, comparatively little is known about the influence of behaviours such as boldness and shyness. Using information on social interactions in a wild population of Trinidadian guppies (Poecilia reticulata), we construct a social network. For each individual in the network, we quantify its behavioural phenotype using two measures of boldness, predator inspection tendency, a repeatable and reliably measured behaviour well studied in the context of co-operation, and shoaling tendency. We observe striking heterogeneity in contact patterns, with strong ties being positively assorted and weak ties negatively assorted by our measured behavioural traits. Moreover, shy fish had more network connections than bold fish and these were on average stronger. In other words, social fine structure is strongly influenced by behavioural trait. We assert that such structure will have implications for the outcome of selection on behavioural traits and we speculate that the observed positive assortment may act as an amplifier of selection contributing to the maintenance of co-operation during predator inspection.     

Recognition of individual neighbors by song in the song sparrow,a species with song repertoires

Summary Previous theory and research have suggested that bird species with song repertoires in general, and song sparrows (Melospiza melodia) in particular, cannot readily discriminate between the songs of neighbors and strangers. In a recent study (Stoddard et al. 1991) we showed that song sparrows can in fact discriminate neighbors from strangers on the basis of song. In this study we sought to demonstrate that song sparrows can make the finer discrimination between individual neighbors and that they can do so on the basis of a single song type. We compared the response of territorial males to song playback of neighbors and strangers at three locations: the neighbor's regular boundary, the opposite boundary, and the center of the territory. The birds showed strong neighbor-stranger discrimination at the regular boundary but not at the opposite boundary, nor in the center of the territory. The differences in song discrimination between different boundary locations indicate that song sparrows associate particular songs with particular territories, effectively discriminating between individual neighbors on the basis of song. Song repertoires themselves do not interfere with neighbor recognition to the extent originally postulated. As speakers are moved inside the territory from the border, however, the degree of discrimination diminishes. We believe that differences in speaker placement may have contributed to the variability in neighbor-stranger discrimination observed in previous studies of the song sparrow and perhaps other repertoire species as well. This interpretation is consistent with data from another song sparrow population showing that half the territory takeovers are by immediate neighbors.     

A quantitative genetic model of altruistic selection

Summary A quantitative genetic model for evolution by altruistic selection based on family selection models used in agricultural genetics is presented. A quantitative genetic version of Hamilton's rule is derived which indicates that evolution will proceed in an altruistic direction whenever the ratic of between-to within-family (or group) heritability exceeds the absolute value of the within-to between-family selection differential ratio. This ratio of heritabilities is equal to a ratio which includes only the phenotypic and genetic intraclass correlation coefficients, thus no heritabilities actually need to be estimated in determining the possibility of altruistic evolution. The phenotypic intraclass correlation can be estimated with standard analysis of variance methods. The genetic intraclass correlation may be estimated by the average within-group coefficient of relationship using genealogical data, by Wright's F-statistics using allele frequency data, or by a theoretical model based on a knowledge of interaction and mating patterns. Selection differentials may be measured by the regression of relative fitness, or one of its major components, on the phenotype of interest. Selection can be considered altruistic only if within-and between-family selection differentials have opposite signs. Consideration of empirical data on genetic and phenotypic intraclass correlations indicates that evolution may proceed in an altruistic direction even if the within-family selection differential exceeds the one between families, especially in situations in which pertinent environmental factors are randomly distributed among families.     

Weather,salience of climate change and congressional voting

Climate change is a complex long-run phenomenon. The speed and severity with which it is occurring is difficult to observe, complicating the formation of beliefs for individuals. We use Google search intensity data as a proxy for the salience of climate change and examine how search patterns vary with unusual local weather. We find that searches for “climate change” and “global warming” increase with extreme temperatures and unusual lack of snow. Furthermore, we demonstrate that effects of abnormal weather extend beyond search behavior to observable action on environmental issues. We examine the voting records of members of the U.S. Congress from 2004 to 2011 and find that members are more likely to take a pro-environment stance on votes when their home state experiences unusual weather.     

Nitrogen niches revealed through species and functional group removal in a boreal shrub community

Most theories attempting to explain the coexistence of species in local communities make fundamental assumptions regarding whether neighbors exhibit competitive, neutral, or positive resource-use interactions; however, few long-term data from naturally assembled plant communities exist to test these assumptions. We utilized a 13-year experiment consisting of factorial removal of three shrub species (Vaccinium myrtillus, V. vitis-idaea, and Empetrum hermaphroditum) and factorial removal of two functional groups (tree roots and feather mosses) to assess how neighbors affect N acquisition and growth of each of the three shrub species. The removal plots were established on each of 30 lake islands in northern Sweden that form a natural gradient of resource availability. We tested the hypotheses that: (1) the presence of functionally similar neighbors would reduce shrub N acquisition through competition for a shared N resource; (2) the removal of functional groups would affect shrub N acquisition by altering the breadth of their niches; and (3) soil fertility would influence the effects of neighbor removals. We found that the removal of functionally similar neighbors (i.e., other shrub species) usually resulted in higher biomass and biomass N, with the strength of these effects varying strongly with site fertility. Shrub species removals never resulted in altered stable N isotope ratios (delta(15)N), suggesting that the niche breadth of the three shrubs was unaffected by the presence of neighboring shrub species. In the functional group removal experiment, we found positive effects of feather moss removal on V. myrtillus biomass and biomass N, and negative effects on E. hermaphrotium N concentration and V. vitis-idaea biomass and biomass N. Tree root removal also caused a significant shift in foliar delta(15)N of V. myrtillus and altered the delta(15)N, biomass, and biomass N of E. hermaphroditum. Collectively, these results show that the resource acquisition and niche breadth of the three shrub species are often affected by neighbors, and further that both the identity of neighbors and site fertility strongly determine whether these interactions are positive, negative, or neutral. These findings have implications for understanding species coexistence and the reciprocal relationships between productivity and species diversity in this ecosystem.     

A test of multiple hypotheses for the function of call sharing in female budgerigars, Melopsittacus undulatus

In many social species group, members share acoustically similar calls. Functional hypotheses have been proposed for call sharing, but previous studies have been limited by an inability to distinguish among these hypotheses. We examined the function of vocal sharing in female budgerigars with a two-part experimental design that allowed us to distinguish between two functional hypotheses. The social association hypothesis proposes that shared calls help animals mediate affiliative and aggressive interactions, while the password hypothesis proposes that shared calls allow animals to distinguish group identity and exclude nonmembers. We also tested the labeling hypothesis, a mechanistic explanation which proposes that shared calls are used to address specific individuals within the sender–receiver relationship. We tested the social association hypothesis by creating four–member flocks of unfamiliar female budgerigars (Melopsittacus undulatus) and then monitoring the birds’ calls, social behaviors, and stress levels via fecal glucocorticoid metabolites. We tested the password hypothesis by moving immigrants into established social groups. To test the labeling hypothesis, we conducted additional recording sessions in which individuals were paired with different group members. The social association hypothesis was supported by the development of multiple shared call types in each cage and a correlation between the number of shared call types and the number of aggressive interactions between pairs of birds. We also found support for calls serving as a labeling mechanism using discriminant function analysis with a permutation procedure. Our results did not support the password hypothesis, as there was no difference in stress or directed behaviors between immigrant and control birds.