Territorial Neighbors Research Articles

Neighbors affect vocal behavior of tropical wrens: a multispeaker density-manipulation experiment.

For territorial animals, the behavior of conspecific neighbors sets the social context of communication. Despite numerous investigations of vocalizations related to territory defense and mate attraction, the effect of neighbor density on animal vocal behavior has received little attention, particularly in tropical animals and animals where both sexes produce complex acoustic signals. In this study, we used an innovative multispeaker playback experiment to manipulate the apparent density of neighbors in rufous-and-white wrens, Thryophilus rufalbus, living in Costa Rica's tropical dry forest. In this tropical songbird, both males and females defend year-round territories and sing complex, learned songs for territory defense. We recorded the singing behavior of 24 subjects (12 pairs), and then we used an array of 6 loudspeakers to simulate the presence of 6 new territorial neighbors (3 simulated pairs) outside each subject pair's breeding territory. The stimuli persisted for 3 consecutive days, with both male and female songs broadcast at a natural rate from dawn to dusk. We found that the mean male song rate increased by almost 50% in response to the simulated increase in local density. Females showed less frequent song-type switching rates following the simulated increase in local density, although it was a marginal increase. These findings reveal that male and female songbirds' vocal behavior varies with the local density of territorial neighbors. We conclude that birds are sensitive to acoustic signals of conspecific density arising from sounds beyond their territory boundaries, and that they use this public information to guide their vocal behavior.

Effects of age, breeding strategy, population density, and number of neighbors on territory size and shape in Passerculus sandwichensis (Savannah Sparrow)

Abstract The size and shape of an animal’s breeding territory are dynamic features influenced by multiple intrinsic and extrinsic factors and can have important implications for survival and reproduction. Quantitative studies of variation in these territory features can generate deeper insights into animal ecology and behavior. We explored the effect of age, breeding strategy, population density, and number of neighbors on the size and shape of breeding territories in an island population of Passerculus sandwichensis (Savannah Sparrow). Our dataset consisted of 407 breeding territories belonging to 225 males sampled over 11 years. We compared territory sizes to the age of the male territorial holder, the male’s reproductive strategy (monogamy vs. polygyny), the number of birds in the study population (population density), and the number of immediate territorial neighbors (local density). We found substantial variation in territory size, with territories ranging over two orders of magnitude from 57 to 5727 m2 (0.0057–0.57 ha). Older males had larger territories, polygynous males had larger territories, territories were smaller in years with higher population density, and larger territories were associated with more immediate territorial neighbors. We also found substantial variation in territory shape, from near-circular to irregularly-shaped territories. Males with more neighbors had irregularly shaped territories, but shape did not vary with male age, breeding strategy, or population density. For males that lived two years or longer, we found strong consistent individual differences in territory size across years, but weaker individual differences in territory shape, suggesting that size has high repeatability whereas shape has low repeatability. Our work provides evidence that songbird territories are highly dynamic, and that their size and shape reflect both intrinsic factors (age and number of breeding partners) and extrinsic factors (population density and number of territorial neighbors).

Song overlapping and matching during low‐arousal singing and their relation to visual ornaments, parental care and breeding success in the great tit (Parus major)

AbstractEavesdropping on interactions between conspecific animals provides a low‐cost method for assessing other individuals. Asymmetries in territorial counter‐singing interactions in songbirds provide a rich source of information for eavesdroppers about differences between the singers. Yet, little is known about the relationship between interactive singing in a natural, low‐arousal context among territorial neighbours and individual traits of males. We used a microphone array to monitor natural counter‐singing interactions in great tits (Parus major) during nest building, at the onset of the breeding season. We quantified song overlapping and song matching for 30 pairs (dyads) of interacting males, singing at their nest, respectively. We then compared these behaviours to five traits for 28 males: body condition, plumage ornamentation, offspring provisioning behaviour, offspring weight and breeding site quality. We found no relationship between a male song overlapping or matching behaviour and any of the measured traits. Therefore, our results do not support the idea that short‐term asymmetries in low‐arousal long‐range singing interactions among neighbours reflect differences in these fitness‐related traits. Instead, our findings suggest that such singing asymmetries have less signal value in the absence of an immediate conflict but instead reflect short‐term motivational differences, as shown in previous investigations.

Poļu izcelsmes vārdi Latvijas baltkrievu presē 20. gs. sākumā

This article is a continuation of the research that the author has carried out analysing the contacts between Belarusian and Latvian languages in Belarusian periodicals published in the 20th century. This study analyses the influence of Polish in the Belarusian language of Latvia, as reflected in the periodicals of the 20th century. The aim of this article is to present some aspects of the influence of Polish in the local Belarusian language. The importance of Polish and Belarusian as contact languages in Latvia is mainly determined by the historical and areal aspects of language contact. Poles and Belarusians are territorial neighbours with close genetic ties and long-standing economic, cultural, and political relations. Poles and Belarusians are Latvian minorities whose history is linked to Latgale. Polish was, for a long time, the dominant language in the religious sphere (Catholicism) and culture, so in the local Belarusian periodicals, it is possible to observe the influence of Polish in the Latvian Belarusian language, which was reflected in the use of some Polish words and word components. As languages come into contact, it can lead to borrowing from one language into another. Interference occurs when linguistic norms are mixed and other linguistic norms are picked up so that deviations from the norms of the mother tongue can occur under the influence of the contact language.

Why does the complexity of functionally equivalent signals vary across closely related species?

Abstract Animal signals are observed to vary widely in complexity among species, but why this should be the case—especially among closely related taxa—is unclear. Identifying the selective forces that drive these differences is important for understanding signal evolution, as well as the origins of communication more generally. We used a measure derived from information theory to quantify the complexity of visual territorial advertisement displays performed by males of closely related taxa of Puerto Rican Anolis lizard. In general, the information potential of visual displays appeared to be high compared with signals of other taxonomic groups (e.g., other lizards, birds). Nevertheless, there was still considerable variation in signal complexity among the Anolis taxa studied. We found a strong relationship between signal complexity and phylogeny for some aspects of the advertisement display traditionally thought to be important in species recognition. Other aspects of the display tended to vary independently of phylogeny, with differences in signal complexity among taxa reflecting the distance over which displays were typically viewed by territorial neighbors, and to some extent the number of sympatric congeners present in the environment. More generally, we highlight a little used, but tractable means of quantifying complexity in different species—and in different aspects of the same signal (the number, timing, and type of components)—that can reveal the evolutionary processes generating increases (or decreases) in communicative complexity.

Intruder familiarity and not duet similarity influences the territory defense in a year-round territorial bird species

To avoid unnecessary energy expenditures in territorial defense, many species (e.g., insects, amphibians, birds, and mammals) have developed the capability to distinguish between different intruder types using visual, acoustic, and/or chemical signals. Determining the mechanism used for intruder recognition is key to understanding the dynamics of territorial behaviors. In birds that use vocalizations for territorial defense, the frequency and duration of vocalizations or the familiarity with the intruder may be the main mechanism used for intruder recognition. Here, we conducted a playback experiment with territorial White-eared Ground-sparrows (Melozone leucotis), to analyze if territorial pairs recognize intruders using frequency and duration characteristics (a bird's response is based on how structurally similar the intruders' duets are to their own) or by familiarity with the intruders (neighbors vs. non-neighbors). We focused on duets because this species uses duets exclusively for territorial defense. We broadcasted a duet from a territorial neighbor, two duets from non-neighbors (with different frequency and duration characteristics), and a duet from a control species in 39 territorial pair from three populations. During playback we measured five behavioral responses: latency of the first vocalization, latency of the approach to the speaker, time spent close the speaker (within 5 ​m), number of individuals that approached the speaker, and the number of vocalizations. We found that territorial White-eared Ground-sparrow pairs responded stronger to neighbors than non-neighbors, and this response is not influenced by duet duration or frequency characteristics. This result suggests that neighbors represent a greater territorial threat for White-eared Ground-sparrows than non-neighbors. Further work is necessary to understand how common this observation is for tropical species that defend small territories year-round.

Vocal learning in Savannah sparrows: acoustic similarity to neighbours shapes song development and territorial aggression

Vocal learning is a biologically rare adaptation that underpins both human language and the songs of songbirds. The adaptive value of vocal learning in birds is still poorly understood, but a growing body of literature suggests that vocal learning allows songbirds to gain a fitness advantage by adopting songs that are structurally similar to the songs of individuals in neighbouring breeding territories. In this study, we investigate patterns of song development, acoustic similarity, and territorial aggression in Savannah sparrows, Passerculus sandwichensis. Four years of field data reveal that Savannah sparrows routinely overproduce songs during development; more than half of young males sang more than one song type early in their first breeding season, before their repertoire underwent attrition to a single song that males maintained throughout the remainder of their lives. We also found that the attrition of song types is a selective process, with males retaining songs that are similar to the songs of their territorial neighbours. Males that sang songs that were more similar to their neighbours may have faced lower levels of territorial aggression, as indicated by lower numbers of aggressive calls. Our results provide support for the hypothesis that vocal learning in songbirds allows animals to produce songs that match territorial neighbours, possibly providing a benefit in terms of decreased aggression during territorial defence.

Singing in a fragmented landscape: wrens in a tropical dry forest show sex differences in the effects of neighbours, time of day, and time of year

Songbird vocalizations serve diverse functions including territory defence against neighbouring conspecific animals. In tropical and south-temperate regions, it is commonplace for both female and male songbirds to sing solo songs and coordinated vocal duets to defend their territories. The Area de Conservacion Guanacaste in Costa Rica is the site of an ambitious conservation effort to protect and regrow tropical dry forests; it consists of a mosaic of regenerating and mature forest patches, presenting a special opportunity to study the effect of different numbers of neighbours on male and female wrens living in these fragmented forests. We analyzed recordings of Rufous-and-white Wrens (Thryophilus rufalbus) over a 17-year period, focusing on vocal behaviour and variation in the number of territorial neighbours within the fragmented landscape in the conservation area, and on diel and seasonal variation in female and male song. We hypothesized that the number of conspecific neighbours would influence vocal behaviours, including female and male solo song rate, duet responsiveness rate, repertoire use, and song-switching rate. For females, we found that wrens change song-types more often in areas with more neighbours, whereas the other aspects of female vocal behaviour did not vary with the number of neighbours. For males, we found no aspect of vocal behaviour that varied with the number of neighbours. For both sexes, we found variation in vocal behaviours with time of day and time of year, in keeping with previous research. Our results underscore the idea that we must explore female and male birds independently, because the sexes may respond differently to external factors. We did not find strong links between wren vocal behaviour and variation in the number of neighbours, yet we encourage further behavioural studies on vocal behaviour of birds with varying numbers of neighbours in fragmented landscapes.

Machine Learning for Revealing Spatial Dependence among Nanoparticles: Understanding Catalyst Film Dewetting via Gibbs Point Process Models

We combine in situ environmental transmission electron microscopy (E-TEM) with automated image processing and statistical machine learning to uniquely formulate interpretable mathematical models and accurate simulation tools for complex nanoscale phenomena involving coupled physical and chemical processes and interactions that are otherwise hard to model. In particular, there is a need for a better understanding, characterization, and prediction of the proximity effects among dense populations of metal nanocatalysts as they form and evolve over time. Here, we leverage point process theory, a branch of statistical machine learning, to “learn” the spatial dependencies among ensembles of adjacent alumina-supported iron nanoparticles from a time sequence of E-TEM images. We construct a set of point process models to make statistical inferences about the nature of spatial dependencies that govern the rapid formation, or “popping” of nanoparticles during thin film dewetting, concomitant with metal reduction in the presence of acetylene at 750 °C. We show that nanoparticles exhibit strong dispersion behavior, i.e., new nanoparticles pop in dispersed locations at a predictable distance from their existing territorial neighbors. We also show that Gibbs point processes adequately describe the pairwise interactions underlying such time-dependent spatial variations. Further, we build on our machine-learned models to develop a computational simulation tool capable of producing accurate spatiotemporal simulations of nanoparticle formation at finer time resolutions and larger spatial domains than those of experimental observations. This is a much needed capability to overcome current limitations in computational methods supporting the design, analysis, and control of the collective behavior of nanocatalyst populations.

Social factors in bird-song development: Learning to sing with friends and rivals.

Laboratory studies have revealed that social factors are key in bird-song learning. Nevertheless, little is known about how or why birds choose the songs they do learn from the many they will hear under natural conditions. We focus on various theories concerning social song learning that have been offered to date, with special attention paid to two axes of social factors. First, does song learning occur via direct interaction of the young bird with song tutors, or via social eavesdropping by the young bird on interacting singers (social modeling of song)? Social modeling, a hypothesis first proposed by Pepperberg (Zeitschrift für Tierpsychologie, 55(2), 139-160, 1981), and direct interaction are not mutually exclusive hypotheses, and the evidence we review suggests both play a role in song learning. Second, does song learning occur via interactions with rivals (territorial competitors) or with friends (mutually tolerant or even cooperative territorial neighbors). These are largely mutually exclusive hypotheses, and can really only be tested in the field. There is little evidence on this contrast to date. We review our recent study on song sparrows, which indicates that both the young bird and his primary tutor may benefit from song learning/tutoring. If this mutual benefit result is confirmed by further studies, we believe that song "tutoring" in these cases may be more than a term of convenience: that it may qualify as true teaching.

Framing of China Pakistan Economic Corridor (CPEC) in Elite Press of India and Afghanistan (2015-2017)

$1 trillion Belt Road Initiative (BRI)’s China-Pakistan Economic Corridor (CPEC) component is a dimensional shift in Sino-Pak relations and a conception of shared future being heralded as the game changer for Pakistan as well as for the whole region. As a nodal part of the China’s ambitious Belt & Road Initiative that envisage to improve connectivity on transcontinental scale by connecting China to Central and Eastern Europe, the Middle East and Africa, the CPEC has come under attention of international media, policy makers, economists and academicians. This study discusses the framing of CPEC in press of India and China. India being territorial neighbors and China being the investor shares certain interests, reservations and apprehensions related to CPEC. Two English newspapers from China (China Daily & Global Times) and India (Indian Express & The Hindu) were selected and all the news and editorials related to CPEC were analyzed for the period of 2015-2017. Finding reveals that India’s press is covering CPEC more in terms of strategic and conflict perspective rather than infrastructure and connectivity aspects. However, the Chinese press covers CPEC in broader context of BRI and globalization hence connectivity, development, strategic value and economic paybacks are the dominant frames. Moreover, framing of CPEC varies over the time in the press of India and China. Study suggests that policy making is needed to reduce the negative stance and communication differences of international press towards CPEC. Findings imply that Pakistan should made efforts to develop better relations with neighboring countries by engaging them with CPEC as a project of development, mutual benefit and regional integration.

Social stress in female Columbian ground squirrels: density-independent effects of kin contribute to variation in fecal glucocorticoid metabolites

Social interactions among conspecifics can have marked effects on individual physiology, especially through their modulation of the stress axis by affecting the production of adrenal glucocorticoids (GCs). Previous research has focused on how individual GC levels may be influenced by social status, but few studies have considered how the balance between positive (e.g. cooperation) and negative (e.g. competition) social interactions shape individual GC levels. A lack of association between individual GC levels and social factors may be confounded by opposite effects of social competition on the one hand and social cooperation on the other. We tested for these effects in the Columbian ground squirrel (Urocitellus columbianus), a colonial rodent. During the breeding season, females are exposed to territorial unrelated neighbors and to territorial, but more tolerant, close kin. On one hand, territoriality and competition for resources led us to predict a positive association between local colony density and female GC levels. On the other, higher tolerance of philopatric kin females and known fitness benefits led us to predict a negative association between kin numbers and female GC levels. We compared levels of fecal cortisol metabolites (FCMs) in females at two different spatial scales during lactation: local (a female’s core territory during lactation, 30-m radius about her nest burrow) and colony-wide. At the local scale, female FCM levels were neither related to colony density nor to the number of co-breeding female kin, but FCM levels increased with age. At the colony scale, female FCM levels varied in a quadratic fashion with female kin numbers. FCM levels decreased by 15% from 0 to 1 co-breeding kin present and increased with > 1 kin present. Among females that had only one co-breeding kin present, daughters (and littermate sisters and mothers, but not significantly) led to a 14% reduction in FCM levels compared with females that had no kin. Our results reject the idea that local colony density is associated with increased GC levels this species, but indicate subtle (positive and negative) effects of kin on individual GC secretion. They further call into question the importance of the nature of social relationships in modulating the stress experienced by individuals. Few studies have tested how the balance between positive (e.g. cooperation) and negative (e.g. competition) social interactions shapes individual stress and glucocorticoid (GC) levels in group-living animals. In colonial Columbian ground squirrels, breeding females are exposed to territorial neighbors and to more tolerant close kin. We show that kin numbers have subtle (positive and negative) effects on female GC levels. Compared with breeding females with no kin, female GC levels decrease by 15% with the presence of a single co-breeding close relative, but increase with the presence of more than one co-breeding related female. Among females that have only one co-breeding kin, the presence of daughters (and littermate sisters and mothers, but not significantly) leads to a 14% reduction in female GC levels. Our results highlight how GC levels may be influenced by the specific nature of social relationships in group-living animals.

Territory establishment, song learning strategies and survival in song sparrows

AbstractIn most songbirds, the processes of song learning and territory establishment overlap in the early life and a young bird usually winds up with songs matching those of his territorial neighbors in his first breeding season. In the present study, we examined the relationships among the timing of territory establishment, the pattern of song learning and territorial success in a sedentary population of song sparrows (Melospiza melodia). Males in this population tend to learn their songs from their neighbors and consequently they show high song sharing with neighbors and use these shared songs preferentially in interactions with them. Males also show significant variation in the timing of territory establishment, ranging from their natal summer to the next spring. Using a three‐year dataset, we found that the timing of territory establishment did not systematically affect the composition of the song repertoire of the tutee: early establishers and late establishers learned equally as much from their primary tutors and had a similar number of tutors and similar repertoire sizes, nor did timing of territory establishment affect subsequent survival on territory. Therefore, the song‐learning program of song sparrows seems versatile enough to lead to high song sharing even for birds that establish territories relatively late.

Aggression towards shared enemies by heterospecific and conspecific cichlid fish neighbours

Successful territory defence is a prerequisite for reproduction across many taxa, and often highly sensitive to the actions of territorial neighbours. Nevertheless, to date, assessments of the significance of the behaviour of heterospecific neighbours have been infrequent and taxonomically restricted. In this field study, I examined the importance of both heterospecific and conspecific neighbours in a biparental fish, the convict cichlid, Amatitlania siquia. This was done by assessing the colonisation rates of vacant territories, the rates of aggression by the territory holders, and the overall rates of aggression towards intruders, in treatments that controlled the proximity of both neighbour types. Convict cichlid pairs colonised vacant nesting resources (territory locations) at similar rates independent of the proximity of heterospecific (moga, Hypsophrys nicaraguensis) or conspecific neighbours. However, a model of sympatric cichlid intruder was subjected to considerably higher overall levels of aggression when mogas were nearby. In contrast, the proximity of conspecifics did not have a significant effect on the overall aggression towards the intruder. These results suggest that previously demonstrated higher survival of convict cichlid broods in close proximity of mogas may be driven by aggression towards shared enemies. No conclusive evidence was found regarding whether mogas also influence convict cichlids’ investment into anti-intruder aggression: the results show a marginally non-significant trend, and a moderately large effect size, to the direction of a lower investment in mogas’, but not conspecifics’, proximity. More generally, heterospecific neighbours may provide protective benefits in a wider range of ecological settings than commonly considered.

North American red squirrels mitigate costs of territory defence through social plasticity

For territorial species, the ability to be behaviourally plastic in response to changes in their social environment may be beneficial by allowing individuals to mitigate conflict with conspecifics and reduce the costs of territoriality. Here we investigated whether North American red squirrels, Tamiasciurus hudsonicus, are able to minimize costs of territory defence by adjusting behaviour in response to the familiarity of neighbouring conspecifics. Since red squirrels living in familiar neighbourhoods face reduced intrusion risk, we predicted that increasing familiarity among territorial neighbours would allow squirrels to spend less time on territorial defence and more time in the nest. Longitudinal behavioural data (1995–2004) collected from the same squirrels across several different social environments indicated that red squirrels reduced rates of territorial vocalizations and increased nest use in response to increasing familiarity with neighbours. In contrast, cross-sectional data (2015–2016), which provided observations from each individual in a single social environment, did not provide evidence of this plasticity. Post hoc analyses revealed that evidence of social plasticity in this system is primarily due to within-individual changes in behaviour, which we were unable to estimate in the cross-sectional data. Our results demonstrate that red squirrels respond to changes in their social environment by adjusting their behaviour in a manner that reduces the costs of territoriality. However, our results also suggest that estimating plasticity by comparing behaviour among individuals (i.e. cross-sectional analyses) may not always be reliable. Our ability to detect these effects may therefore depend on having data with multiple observations from the same individuals across different social environments.

Increasing conservation translocation success by building social functionality in released populations

The importance of animal behavior to successful wildlife translocations has been acknowledged in recent decades, and it has been increasingly considered and more frequently incorporated into translocation management and research. However, explicit consideration of social behavior is often overlooked in this context. Social relationships take a variety of forms (e.g., cooperative partners, members of a dominance hierarchy, territorial neighbors) and play important roles in survival, reproduction, and resource exploitation. We review the ways in which concepts from studies of social behavior in wild populations may be leveraged to increase translocation success. Social structure and cohesion, social roles, social learning, and social competency may all be important to consider in building populations that are resilient and likely to persist. We argue that relevant data collected at all stages of translocation, including candidate selection, and during pre-release, release, and post-release monitoring, may inform the establishment of functional social structure post-release in species dependent on social processes. Integrating knowledge of social behavior into management decisions may be particularly useful when comparing the success of alternative release protocols or release candidate behavioral traits. Complementary datasets on a range of fitness-related metrics post-release will further leverage our understanding of social establishment in translocated populations. We illustrate the potential of these ideas using Asian and African elephants as a model. Both species are particularly challenging to manage but are translocated frequently; thus, evidence-based protocols for conservation translocations of elephants are urgently needed.

Social effects of territorial neighbours on the timing of spring breeding in North American red squirrels.

Organisms can affect one another's phenotypes when they socially interact. Indirect genetic effects occur when an individual's phenotype is affected by genes expressed in another individual. These heritable effects can enhance or reduce adaptive potential, thereby accelerating or reversing evolutionary change. Quantifying these social effects is therefore crucial for our understanding of evolution, yet estimates of indirect genetic effects in wild animals are limited to dyadic interactions. We estimated indirect phenotypic and genetic effects, and their covariance with direct effects, for the date of spring breeding in North American red squirrels (Tamiasciurus hudsonicus) living in an array of territories of varying spatial proximity. Additionally, we estimated indirect effects and the strength of selection at low and high population densities. Social effects of neighbours on the date of spring breeding were different from zero at high population densities but not at low population densities. Indirect phenotypic effects accounted for a larger amount of variation in the date of breeding than differences attributable to the among-individual variance, suggesting social interactions are important for determining breeding dates. The genetic component to these indirect effects was however not statistically significant. We therefore showcase a powerful and flexible method that will allow researchers working in organisms with a range of social systems to estimate indirect phenotypic and genetic effects, and demonstrate the degree to which social interactions can influence phenotypes, even in a solitary species.

Brilliant-thighed poison frogs do not use acoustic identity information to treat territorial neighbours as dear enemies

Some territorial animals recognize familiar neighbours and are less aggressive to established neighbours than they are to strangers. This form of social recognition produces a ‘dear enemy’ effect, which may allow animals to reduce the costs of territory defence. The dear enemy effect is thought to reflect either the decreased threat posed by neighbours relative to strangers (the relative threat hypothesis) or the decreased need for escalation with increasing familiarity between neighbours (the familiarity hypothesis). We tested for a vocally mediated dear enemy effect in male brilliant-thighed poison frogs, Allobates femoralis. In this species, the familiarity hypothesis predicts a dear enemy effect, because males defend long-term stable territories and should be familiar with the calls of their neighbours. In contrast, the relative threat hypothesis does not predict a dear enemy effect, because neighbours and strangers both represent competitors for mates and likely pose equivalent threats. Acoustic analyses showed that males produce individually distinctive advertisement calls. Two playback experiments were conducted to determine whether territorial males respond less aggressively to neighbours' calls than to strangers' calls based on this acoustic identity information. In the first experiment, males pursued acoustically simulated neighbours and strangers to similar distances when calls were played both from the direction of the neighbour's territory and from a direction with no neighbours. In the second experiment, males responded aggressively to neighbours' and strangers' calls at similar threshold amplitudes and pursued these calls to similar distances. Hence, two different playback experiments failed to find evidence of a vocally mediated dear enemy effect. Our results support the hypothesis that territorial animals respond to the relative threat posed by neighbours and strangers regardless of their level of familiarity with neighbours.

Individual variation in the dear enemy phenomenon via territorial vocalizations in red squirrels

Abstract Territoriality arises when the benefits of resources exceed the costs of defending them. The dear enemy phenomenon, where familiar territorial neighbours refrain from intruding on one another and mutually reduce their defensive efforts, allows for reduction of these costs but requires discrimination between conspecifics. We hypothesized that territorial vocalizations in red squirrels (Tamiasciurus hudsonicus) are used for this discrimination. We performed a speaker replacement experiment where red squirrels () were temporarily removed from their territories and replaced with a speaker broadcasting their own call, an unfamiliar call, or silence. Contrary to our prediction, there were no differences in overall intrusion risk among our three playbacks, but the identity of intruders did vary. Existing variation in familiarity within territorial neighbourhoods should be considered, rather than the binary classification of familiar or stranger, when studying dear enemy effects. We also discuss the variable importance of silence in acoustic territorial populations.

The Diffusion of Inclusion: An Open-Polity Model of Ethnic Power Sharing

While there is a growing consensus that ethnic inclusion produces peace, less is known about what causes transitions to power sharing between ethnic groups in central governments in multiethnic states. The few studies that have addressed this question have proposed explanations stressing exclusively domestic factors. Yet, power sharing is spatially clustered, which suggests that diffusion may be at play. Inspired by studies of democratic diffusion, we study the spread of inclusive policies with an “open-polity model” that explicitly traces diffusion from inclusion in other states. Our findings indicate that the relevant diffusion processes operate primarily at the level of world regions rather than globally or between territorial neighbors. Thus, the more inclusive the region, the more likely a shift to power sharing becomes. Shifts away from inclusion to dominance are less common since World War II, but they are more likely in regional settings characterized by ethnic exclusion.