Kinship,dear enemies,and costly combat: The effects of relatedness on territorial overlap and aggression in a cooperative breeder

Many species maintain territories, but the degree of overlap between territories and the level of aggression displayed in territorial conflicts can vary widely, even within species. Greater territorial overlap may occur when neighboring territory holders are close relatives. Animals may also differentiate neighbors from strangers, with more familiar neighbors eliciting less‐aggressive responses during territorial conflicts (the “dear enemy” effect). However, research is lacking in how both kinship and overlap affect territorial conflicts, especially in group‐living species. Here, we investigate kinship, territorial overlap, and territorial conflict in a habituated wild population of group‐living cooperatively breeding birds, the southern pied babbler Turdoides bicolor. We find that close kin neighbors are beneficial. Territories overlap more when neighboring groups are close kin, and these larger overlaps with kin confer larger territories (an effect not seen for overlaps with unrelated groups). Overall, territorial conflict is costly, causing significant decreases in body mass, but conflicts with kin are shorter than those conducted with nonkin. Conflicts with more familiar unrelated neighbors are also shorter, indicating these neighbors are “dear enemies.” However, kinship modulates the “dear enemy” effect; even when kin are encountered less frequently, kin elicit less‐aggressive responses, similar to the “dear enemy” effect. Kin selection appears to be a main influence on territorial behavior in this species. Groups derive kin‐selected benefits from decreased conflicts and maintain larger territories when overlapping with kin, though not when overlapping with nonkin. More generally, it is possible that kinship extends the “dear enemy” effect in animal societies.     

Behavioral response to familiar and unfamiliar neighbors in a territorial cichlid, <Emphasis Type="Italic">Neolamprologus pulcher</Emphasis>

Some territorial species have been shown to react more aggressively toward unfamiliar conspecifics than established neighbors, a behavior referred to as the dear enemy phenomenon. Laboratory experiments were conducted to determine whether males of a territorial African cichlid, Neolamprologus pulcher, can discriminate between size-matched familiar and unfamiliar male neighbors and whether they respond more aggressively toward unfamiliar males. It was found that males spent significantly more time near the territorial boundary that they shared with unfamiliar neighbors and directed significantly more aggressive behavior toward these individuals.     

Effects of age and experience on the responses of territorial and floater male Red‐winged Blackbirds to models of receptive females

The ability of sexually mature non‐territorial floaters to sire offspring affects the success of floating as a breeding strategy. Red‐winged Blackbirds (Agelaius phoeniceus) have second‐year (SY) and after‐second‐year (ASY) floater males, and genetic studies suggest that floaters may gain paternity. Despite these studies, we still know little about the fitness costs and benefits of floating in this species. By presenting taxidermic models of females in soliciting, precopulatory postures in territories of experienced (previously attracted at least one mate in the study area) and inexperienced (did not previously defend a territory in the study area) males, I was able to examine the copulation behavior and success of floater male Red‐winged Blackbirds as well as the effect of experience for territorial males. Floaters trespassed during 66.1% of presentations and 85.4% of trespassers were SY males. Experienced territorial males (92.5%) and neighbors (87.5%) were most successful in attempts to copulate with models, inexperienced territorial males (62.5%) and ASY floaters (50.0%) had intermediate success, and SY floaters (6.9%) were least successful. Experienced territorial males were more likely to approach models than inexperienced males, and floaters were more likely to approach models in territories of experienced than inexperienced males. These results provide further evidence that floaters trespass frequently, suggest that floaters sire offspring, and demonstrate that prior breeding experience affects the behavior and reproductive success of territorial male Red‐winged Blackbirds. Floating appears to be a conditional strategy for ASY male Red‐winged Blackbirds, but, because it is still not known if SY floaters sire offspring, these males may be trespassing to gain information or experience.     

Behavior pattern (innate action) of individuals in fish schools generating efficient collective evasion from predation

The schooling of fishes is one typical animal social behavior. One primary function of fish school is to protect members when attacked by predators. One main way that the school reduces the predator's chance of making a successful kill is to confuse the predator as it makes its strike. This may be accomplished by collective evasion behaviors organized through integration of motions of individual fish made based on their innate actions (behavior patterns). In order to investigate what kind of behavior pattern of individuals can generate the efficient collective evasion of a school, we present a model of evasion behavior pattern which consists of three component behavior patterns, schooling, cooperative escape, and selfish escape behavior patterns and the rule for choice of one among them with proper timing. Each fish determines its movement direction taking into account simultaneously three kinds of elemental motions, mimicking its neighbors, avoiding collisions with its nearest neighbors, and escaping from an approaching predator. The weights of three elemental motions are changed depending on which component behavior pattern the fish carries out. The values of the weights for three component behavior patterns can be definitively determined under the condition that the collective evasion of the school becomes the most efficient, that is, the probability that any member is eaten by the predator becomes minimum.     

Territory Area as a Determinant of Mating Systems

Territoriality is an integral part of breeding behavior in manyanimals. Because the reproductive success of territorial malesis often limited by access to females, breeding males shouldbehave as "area maximizers" when the basis of female choiceis either the abundance of resources within the territory orterritory area per se. Being reproductively more limited byenergy, territorial females should be "energy maximizers." Aseries of simple analytical models of territory area for suchforagers is developed to explore how changes in local food productionand/or local competitor density affect both the probabilityof a territorial male securing more than one mate (polygyny)and the probability of his and his mates' reproductive successincreasing. Two cases are modeled (only males territorial vs.both sexes territorial), each for various sets of assumptionsregarding interactions between food production, feeding efficiency,and competitor density. Concurrent responses in territory area,territory food reserves, net energy gain, and time budgetingprovide testable sets of predictions for each scenario. Whereonly males are territorial (Case I), changes in food productioncan have different (indeed, opposite) effects upon an individualmale's probability of becoming polygynous, depending upon whetherthe basis of female choice is the abundance of food within theterritory or another factor positively correlated with territoryarea. Increases in competitor density usually decrease the probabilityof polygyny regardless of the basis of female choice. Whereboth sexes are territorial and territories overlap intersexually(Case II), the mating system becomes a function of the numberof female territories within each male's territory, which varieswith the ratio of male to female territory areas. In this case,the probability of polygyny occurring will increase if foodproduction for both sexes increases without concurrent increasesin competitor density, and will decrease if competitor densityfor both sexes increases without concurrent increases in feedingefficiency. Few data are presently available to test eitherthese general predictions or numerous sets of secondary predictionstabulated in the text. Available evidence is largely consistentwith the models, but mostly circumstantial. This is becausethe predictions of these and other models of territory areaare strongly assumption dependent, and few published studieshave investigated these assumptions. These analyses demonstratethat to accurately assess the mechanisms by which environmentalfactors affect territory area, and thus mating systems, testsof the underlying assumptions of models are essential.     

Dawn Singing Intensity of the Male Brownish‐Flanked Bush Warbler: Effects of Territorial Insertions and Number of Neighbors

The dawn chorus is a period of peak singing activity of many songbirds. Numerous studies have sought to understand this widespread phenomenon, and many hypotheses have been proposed to explain the dawn chorus. The social dynamics hypothesis proposes that dawn singing plays an important role in the announcement of territorial occupancy and the regulation of social relationships between males; it predicts that the dawn chorus vocal behavior varies with changes in social relationships. In this study, we tested the influence of territorial insertions and the number of neighbors, on the intensity of the brownish‐flanked bush warbler (Cettia fortipes)'s dawn singing. We found that simulated territorial insertions (playback) caused the males to increase their dawn singing significantly the next day, and males that had many neighbors exhibited more intense dawn singing than did males with few neighbors. Our study provides evidence that dawn singing plays an important role in the announcement of territorial occupancy and the regulation of the social relationships between the males.     

Territorial behavior in the Agile Gibbon

A group of agile gibbons (Hylobates agilis)was studied for 2 years in the Malay Peninsula. The behavior of the gibbons during territorial disputes is described, the relationships with neighbors are investigated, and the frequency and duration of disputes are analyzed. The nature of the territorial boundary and the type of territorial behavior exhibited by the gibbons are discussed. An attempt is made to identify the immediate precursors of disputes, and some suggestions are given to explain why disputes occur so frequently and are of such long duration.     

Simulated evolution of selfish herd behavior

Single species aggregations are a commonly observed phenomenon. One potential explanation for these aggregations is provided by the selfish herd hypothesis, which states that aggregations result from individual efforts to reduce personnel predation risk at the expense of group-mates. Not all movement rules based on the selfish herd hypothesis are consistent with observed animal behavior. Previous work has shown that herd-like aggregations are not generated by movement rules limited to local interactions between nearest neighbors. Instead, rules generating realistic herds appear to require delocalized interactions. To date, it has been an open question whether or not the necessary delocalization can emerge from local interactions under natural selection. To address this question, we study an individual-based model with a single quantitative genetic trait that controls the influence of neighbors as a function of distance. The results indicate that predation-based selection can increase the influence of distant neighbors relative to near neighbors. Our results lend support for the idea that selfish herd behavior can arise from localized movement rules under natural selection.     

Individual Variation in Advertisement Calls of Territorial Male Green Frogs, Rana clamitans: Implications for Individual Discrimination

Individuals of many territorial species discriminate between familiar territorial neighbors and unfamiliar strangers based on individual differences in acoustic signals. Many anuran amphibians are territorial and use primarily acoustic communication during social interactions, but evidence for acoustically mediated individual discrimination is available only for one species. As a first step in research designed to investigate individual discrimination in a second species of territorial frog, we examined patterns of within-male and among-male variability in 198 advertisement calls of 20 male green frogs, Rana clamitans . The aim was to determine which acoustic properties could be used by males to recognize their territorial neighbors and to estimate limits of reliability afforded by these properties for identifying different neighbors. All of the call properties that we examined exhibited significant inter-individual variation. Discriminant function analyses assigned between 52% and 100% of calls to the correct individual, depending on sample size and the call properties included in the model. This suggests that there is sufficient among-male variability to statistically identify individuals by their advertisement calls. The call properties of fundamental frequency and dominant frequency contributed the most towards discrimination among individuals. Based on their natural history and behavior and the results reported here, we suggest that male green frogs likely discriminate between strangers and adjacently territorial neighbors based on individual variation in advertisement calls.     

Global analysis of dynamical decision-making models through local computation around the hidden saddle

Bistable dynamical switches are frequently encountered in mathematical modeling of biological systems because binary decisions are at the core of many cellular processes. Bistable switches present two stable steady-states, each of them corresponding to a distinct decision. In response to a transient signal, the system can flip back and forth between these two stable steady-states, switching between both decisions. Understanding which parameters and states affect this switch between stable states may shed light on the mechanisms underlying the decision-making process. Yet, answering such a question involves analyzing the global dynamical (i.e., transient) behavior of a nonlinear, possibly high dimensional model. In this paper, we show how a local analysis at a particular equilibrium point of bistable systems is highly relevant to understand the global properties of the switching system. The local analysis is performed at the saddle point, an often disregarded equilibrium point of bistable models but which is shown to be a key ruler of the decision-making process. Results are illustrated on three previously published models of biological switches: two models of apoptosis, the programmed cell death and one model of long-term potentiation, a phenomenon underlying synaptic plasticity.     

Experimental induction of social instability during early breeding does not alter testosterone levels in male black redstarts,a socially monogamous songbird

Testosterone plays an important role in territorial behavior of many male vertebrates and the Challenge Hypothesis has been suggested to explain differences in testosterone concentrations between males. For socially monogamous birds, the challenge hypothesis predicts that testosterone should increase during male–male interactions. To test this, simulated territorial intrusion (STI) experiments have been conducted, but only about a third of all bird species investigated so far show the expected increase in testosterone. Previous studies have shown that male black redstarts (Phoenicurus ochruros) do not increase testosterone during STIs or short-term male–male challenges. The aim of this study was to evaluate whether black redstarts modulate testosterone in an experimentally induced longer-term unstable social situation. We created social instability by removing males from their territories and compared the behavior and testosterone concentrations of replacement males and neighbors with those of control areas. Testosterone levels did not differ among replacement males, neighbors and control males. Injections with GnRH resulted in elevation of testosterone in all groups, suggesting that all males were capable of increasing testosterone. We found no difference in the behavioral response to STIs between control and replacement males. Furthermore, there was no difference in testosterone levels between replacement males that had expanded their territory and new-coming males. In combination with prior work these data suggest that testosterone is not modulated by male–male interactions in black redstarts and that testosterone plays only a minor role in territorial behavior. We suggest that territorial behavior in species that are territorial throughout most of their annual life-cycle may be decoupled from testosterone.     

A simple model can unify a broad range of phenomena in retinotectal map development

A paradigm model system for studying the development of patterned connections in the nervous system is the topographic map formed by retinal axons in the optic tectum/superior colliculus. Starting in the 1970s, a series of computational models have been proposed to explain map development in both normal conditions, and perturbed conditions where the retina and/or tectum/superior colliculus are altered. This stands in contrast to more recent models that have often been simpler than older ones, and tend to address more limited data sets, but include more recent genetic manipulations. The original exploration of many of the early models was one-dimensional and limited by the computational resources of the time. This leaves open the ability of these early models to explain both map development in two dimensions, and the genetic manipulation data that have only appeared more recently. In this article, we show that a two-dimensional and updated version of the XBAM model (eXtended Branch Arrow Model), first proposed in 1982, reproduces a range of surgical map manipulations not yet demonstrated by more modern models. A systematic exploration of the parameter space of this model in two dimensions also reveals richer behavior than that apparent from the original one-dimensional versions. Furthermore, we show that including a specific type of axon?Caxon interaction can account for the map collapse recently observed when particular receptor levels are genetically manipulated in a subset of retinal ganglion cells. Together these results demonstrate that balancing multiple influences on map development seems to be necessary to explain many biological phenomena in retinotectal map formation, and suggest important constraints on the underlying biological variables.     

A model of ion channel kinetics using deterministic chaotic rather than stochastic processes.

Models of ion channel kinetics have previously assumed that the switching between the open and closed states is an intrinsically random process. Here, we present an alternative model based on a deterministic process. This model is a piecewise linear iterated map. We calculate the dwell time distributions, autocorrelation function, and power spectrum of this map. We also explore non-linear generalizations of this map. The chaotic nature of our model implies that its long-term behavior mimics the stochastic properties of a random process. In particular, the linear map produces an exponential probability distribution of dwell times in the open and closed states, the same as that produced by the two-state, closed in equilibrium open, Markov model. We show how deterministic and random models can be distinguished by their different phase space portraits. A test of some experimental data seems to favor the deterministic model, but further experimental evidence is needed for an unequivocal decision.     

Evidence for Territorial Behavior in a Burrowing Wolf Spider

Evidence is presented for territorial behavior in a burrowing wolf spider, Geolycosa xera archboldi McCrone (Araneae, Lycosidae). These spiders live in burrows in the scrub habitats of central Florida, USA. Mean nearest-neighbor distances repeatedly approximate 30 cm. The constancy of this mean indicates that social spacing may be occurring. A test for perceptual range showed that G. xera can respond to potential prey at distances greater than 30 cm, indicating that the 30-cm nearest-neighbor distance does not represent a distance within which larger neighboring burrow-holders treat smaller neighboring conspecifics as food. Dyadic encounters in field enclosures showed that the distance at which neighbors would not be tolerated was within the observed mean nearest-neighbor distance. In these experimental tests for territorial behavior, smaller dyad members lost burrows significantly more often than larger dyad members.     

Heritable differences in schooling behavior among threespine stickleback populations revealed by a novel assay

Identifying the proximate and ultimate mechanisms of social behavior remains a major goal of behavioral biology. In particular, the complex social interactions mediating schooling behavior have long fascinated biologists, leading to theoretical and empirical investigations that have focused on schooling as a group-level phenomenon. However, methods to examine the behavior of individual fish within a school are needed in order to investigate the mechanisms that underlie both the performance and the evolution of schooling behavior. We have developed a technique to quantify the schooling behavior of an individual in standardized but easily manipulated social circumstances. Using our model school assay, we show that threespine sticklebacks (Gasterosteus aculeatus) from alternative habitats differ in behavior when tested in identical social circumstances. Not only do marine sticklebacks show increased association with the model school relative to freshwater benthic sticklebacks, they also display a greater degree of parallel swimming with the models. Taken together, these data indicate that marine sticklebacks exhibit a stronger tendency to school than benthic sticklebacks. We demonstrate that these population-level differences in schooling tendency are heritable and are shared by individuals within a population even when they have experienced mixed-population housing conditions. Finally, we begin to explore the stimuli that elicit schooling behavior in these populations. Our data suggest that the difference in schooling tendency between marine and benthic sticklebacks is accompanied by differential preferences for social vs. non-social and moving vs. stationary shelter options. Our study thus provides novel insights into the evolution of schooling behavior, as well as a new experimental approach to investigate the genetic and neural mechanisms that underlie this complex social behavior.     

Dear Enemies and the Prisoner's Dilemma: Why Should Territorial Neighbors Form Defensive Coalitions?

Game-theoretic arguments are used to derive two new hypothesesto explain why territorial residents so consistently defeatpotential usurpers. Both hypotheses are based on help from established,familiar neighbors. The first hypothesis follows simply fromKrebs' (1982) assertion that the value of a territory to a usurpermust be decremented by the costs of negotiating dear-enemy relationshipswith the remaining neighbors. An implication is that the remainingneighbors will also have to pay these renegotiation costs ifthe usurper succeeds. The first hypothesis is that it may benefita territorial animal to help its established neighbors defendso it can avoid having to renegotiate territorial boundarieswith a new, unfamiliar neighbor. This hypothesis assumes netpositive benefits to helping without requiring reciprocation. The second hypothesis requires reciprocation to compensate forimmediate net costs of helping. An animal should help its neighborsfight off usurpers only if the neighbors will reciprocate. Thishypothesis is based on the prisoner's dilemma game and buildson Axelrod's (1984) work. Cooperative defense (reciprocal help)can be an evolutionarily stable strategy (ESS) if several conditionsare met. One critical condition is that the relationship betweenneighbors is relatively stable. Cooperative defense should helpestablished neighbors retain their territories, and should thereforebe a cause, as well as a consequence of stability. It is suggestedthat the necessary conditions are not very restrictive, thatthey are often met in nature, and that shared defense is observedbut not recognized as such.     

CADLIVE for constructing a large-scale biochemical network based on a simulation-directed notation and its application to yeast cell cycle

The further understanding of the mechanisms of gene regulatory networks requires comprehensive tools for both the representation of complicated signal transduction pathways and the in silico identification of genomic signals that govern the regulation of gene expression. Consequently, sophisticated notation must be developed to represent the signal transduction pathways in a form that can be readily processed by both computers and humans. We propose the regulator–reaction equations combined with detailed attributes including the associated cellular component, molecular function, and biological process and present the simulation-directed graphical notation that is derived from modification of Kohn’s method. We have developed the software suite, CADLIVE (Computer-Aided Design of LIVing systEms), which features a graphical user interface (GUI) to edit large-scale maps of complicated signal transduction pathways using a conventional XML-based representation. The regulator–reaction equations represent not only mechanistic reactions, but also semantic models containing ambiguous and incomplete processes. In order to demonstrate the feasibility of CADLIVE, we constructed a detailed map of the budding yeast cell cycle, which consists of 184 molecules and 152 reactions, in a really compact space. CADLIVE enables one to look at the whole view of a large-scale map, to integrate postgenomic data into the map, and to computationally simulate the signal transduction pathways, which greatly facilitates exploring novel or unexpected interactions.     

Order and flexibility in the motion of fish schools

The coexistence of order and flexibility in the motion of fish schools was studied by using a simple numerical model and a computer simulation. The numerical model is based on behavioral rules for individuals in the school by considering attraction, repulsion, and parallel-orientation behavior. Each individual follows the same rules and makes school movements. The simulation results show that school order and flexibility are affected by the number of neighbors interacting with an individual in the school and by the randomness of individual motion. Increase in the number of interacting neighbors leads to high order, especially when the number increases from a low value (between one and three). An optimal number of interacting neighbors exists that is relatively low (two or three) for high flexibility, indicating that a fish needs only to pay attention to a few neighbors to realize both order and flexibility. The low randomness of individual motion benefits both order and flexibility. These results indicate that schooling fish have evolved specialized ability for establishing both school order and flexibility.     

The population consequences of territorial behaviour

Many organisms compete for space, or for resource that are linked to space. Territorial behavior in animals is one expression of competition for space. Models of competition for space seek to predict how the arrangement of individuals in a population changes as new individuals appear, others die, and neighbors interact with each other; studies of territorial behaviour examine how neighbor interactions lead animals to establish and maintain their use of space. In recent work on compition for space and on territorial behaviour, there has been a shift from simple, general models to ones that incorporate heterogeneity in the spatial and temporal distribution of resources, and in the ways individuals use resources.     

Toric ideals of phylogenetic invariants.

Statistical models of evolution are algebraic varieties in the space of joint probability distributions on the leaf colorations of a phylogenetic tree. The phylogenetic invariants of a model are the polynomials which vanish on the variety. Several widely used models for biological sequences have transition matrices that can be diagonalized by means of the Fourier transform of an abelian group. Their phylogenetic invariants form a toric ideal in the Fourier coordinates. We determine generators and Gr?bner bases for these toric ideals. For the Jukes-Cantor and Kimura models on a binary tree, our Gr?bner bases consist of certain explicitly constructed polynomials of degree at most four.