Rival recognition in the territorial tawny dragon (Ctenophorus decresii)

The ability to discriminate between familiar and unfamiliar conspecifics is important in territorial animals as it allows animals to distinguish neighbours from non-neighbours. This prevents wasting time and energy in unnecessary aggressive interactions. I investigated the ability of adult males of a territorial lizard, the tawny dragon (Ctenophorus decresii), to distinguish familiar from unfamiliar rivals in a laboratory setting. Males significantly reduced their aggression levels in repeat interactions with familiar rivals and increased their aggression levels towards unfamiliar males. The time taken for interactions to be settled was also significantly lower towards familiar than unfamiliar males. The results of this study suggest that adult male tawny dragons can discriminate familiar from unfamiliar conspecifics. Furthermore, animals were presented with three new rivals in succession and showed a robust ability to discriminate between familiar and unfamiliar males.     

Krieg der Korallen

Clash of the corals As sessile cnidarians, corals have developed numerous strategies to survive the battle for limited settlement area. In addition to employing non‐confrontational strategies like rapid growth and pronounced height growth, their behaviour includes aggression, in which the opponent's body tissue is not only destroyed, but even digested and absorbed in order to gain nutritional benefit from its demise.     

Assortative aggression among males in a sympatric pair of Labeotropheus from Lake Malaŵi,Africa

Female mate choice has strong experimental support as a diversifying force in the speciation of the haplochromine cichlid fishes of Lake Malaŵi, Africa. Somewhat less understood is the role that male–male aggression might have played in the evolution of new species of these fishes. In the rock-dwelling haplochromines of Lake Malaŵi, primarily territory-holding males successfully court females; by determining which males gain territories, male–male aggression could support speciation by excluding less-fit males from the breeding population. To test the hypothesis that males should direct more aggression towards conspecific rivals, the aggression directed towards conspecific and heterospecific opponents was compared in a sympatric pair of cichlids of the genus Labeotropheus Ahl 1927 (Labeotropheus fuelleborni Ahl 1927 and Labeotropheus trewavasae Fryer 1956). It was found that when presented with a pair of rivals, males of both species did direct more aggression towards the conspecific opponent, and the amount of aggression increased when the conspecific opponent was larger than the heterospecific opponent. In addition, this study found a difference in the behavioural repertoire of the species: L. fuelleborni tends to rely on displays to intimidate opponents, whereas L. trewavasae employs more physical attacks to drive away opponents. Males of both species can thus recognize conspecifics and assess an opponent's relative threat to their ability to successfully reproduce, and use species-specific strategies to intimidate opponents.     

The behaviour of the pukeko,Porphyrio porphyrio melanotus

Displays of the pukeko, Porphyrio porphyrio melanotus Temminck (Gruiformes: Rallidae) are described and analysed quantitatively. Aggressive displays centre around the beak, which is presented to the opponent in a position from which a peck can be given. Submissive or escape displays centre around the white undertail coverts, which appear to have evolved as a distinct submissive signal since they are in sharp contrast to the aggressive releaser, both in location and colour. Raising the wings serves to expose the undertail and to provide a contrasting frame. The development of the white undertail as a submissive signal may have paralleled the development of the large frontal shield, which serves to maximise the aggressive releaser. Most displays are ambivalent, signalling both aggression and escape. With increasing escape tendency the bill and frontal shield are so placed that pecking is decreasingly likely, and the wings are increasingly raised. In postures with high escape tendency the beak is placed on the ground or removed from the opponent's view, but only in pure escape postures are the white undertail coverts prominent. Displays which involve rapid removal of the beak and shield from the opponent's view are more common in close contact situations, such as hierarchical interactions between pukeko of the same group. A brief comparison is made with other published reports on gallinules.     

Post-conflict Behaviour of Wild Olive Baboons. II. Stress and Self-directed Behaviour

Previous studies indicate that the proximate function of post-conflict affiliative interaction among primates is to reduce a victim's uncertainty about its opponent's future behaviour: the ‘uncertainty reduction hypothesis’ (Aureli & van Schaik 1991; Ethology, 89 , 101–114). This study confirms and extends these results, demonstrating that they are neither a product of captivity nor specific to macaques: both victims and initiators of aggression in a large group of wild olive baboons exhibited elevated rates of self-directed behaviour (SDB) - scratching, autogrooming, body-shaking and yawning - in a 10-min post-conflict period. During this period, they were more likely to receive further aggression. Reconciliation reduced both SDB and the incidence of further aggression. However, reconciliation only reduced SDB among individuals involved in conflicts in which both parties exchanged aggression. It is suggested that aggressors in unilateral conflicts were aroused rather than uncertain and that their victims' lack of control over post-conflict interactions (which tended to be initiated by their opponents) prevented them from benefiting from reconciliation in the same fashion as longtailed macaque victims, which frequently initiated reconciliation.     

Determinants of the Mating Success of Polyterritorial Pied Flycatcher Males

Much attention has been paid to the polyterritorial mating system of some passerine birds. Here we report how a male's mating success is related to the behavioral traits of polyterritorial pied flycatcher (Ficedula hypoleuca) males. We found no evidence that the timing of polyterritoriality in relation to egg laying in the primary nest or the singing behavior of males have any influence on mating success. However, results show clearly that male mating success was improved with an increase in the distance between territories up to a distance of about 200–300 m whereupon there was no further enhancement of mating success. This finding is crucial for both the deception hypothesis and female-female aggression hypothesis which have been put forward to explain polyterritorial polygyny. Males who establish a distant second territory seemed to allocate more time to singing there. The association, although weak, between singing activity and distance between territories makes it more difficult for females to use song rate as a cue to discriminate males with a secondary territory far from the primary territory, and these are the males that are least likely to feed the young of a second female. Males who established a second territory late in relation to egg laying in the primary nest did not take over a close second territory as might be predicted from female-female aggression hypothesis.     

Prey or predator: 0+ perch (Perca fluviatilis) in the trade-off between food and shelter

The 0+ cohort of perch can split into a slow-growing planktivorous and a fast-growing piscivorous cohort during their first months of life. Both cohorts are, however, vulnerable to predation by piscivorous fish. Laboratory experiments were performed to test the behavior of 0+ perch as a predator of cyprinids, and in the trade-off between food and shelter from the threat of predators. In the foraging trials, 0+ perch attacked bream faster than they did carp, and vegetation hampered the aggression against bream. In the second experiment, the habitat selection of two size classes of 0+ perch under the threat of predation was monitored. Overall, vegetation structures were preferred by both size classes of 0+ perch. When small fish were offered to the 0+ perch as food, the open water becomes more attractive. The results of the habitat use trials further show that the two size cohorts of 0+ perch may also differ in their behavior, in that the availability of fish as food becomes more important than the shelter of vegetation structures for the larger perch.     

Disruption of Dear Enemy Recognition Among Neighboring Males by Female Leon Springs pupfish, Cyprinodon bovinus

Males defending territories often settle into adjacent areas, sharing a common border that is maintained by a reduced level of aggression known as dear enemy recognition. While social conditions may affect the dear enemy relationship among males, what role females play, if any, is unclear. In a field study of the highly promiscuous Leon Springs pupfish, Cyprinodon bovinus, we asked whether females influenced this relationship of neighbors to their advantage. We observed 16 territorial residents, mapping the precise location of each male's behaviors within its territory. Resident males engaged in less aggression against neighbors compared with intruders, and neighbors intruded less deeply into the residents’ territories than intruders. Despite this locality restriction, neighbors were responsible for as many spawning interruptions as intruders. Females did not spawn randomly in the males’ territories, nor did they spawn near territory centers where aggression was low. Rather, females were more likely to settle and spawn in the outer half of the territories where competition among males was highest. When a neighbor entered a resident's territory to interrupt a spawn, the female was more likely to leave the resident's territory for the neighbor's than to remain. These observations suggest that the female used the intrusion by the neighbor to engage the resident and interrupt the spawn as a measure of this male's quality and that, while neighboring males benefit from the presence of dear enemy recognition, females benefit from its disruption.     

BEHAVIORAL CONVERGENCE AND ADAPTIVE RADIATION: EFFECTS OF HABITAT USE ON TERRITORIAL BEHAVIOR IN ANOLIS LIZARDS

Most studies of adaptive radiations focus on morphological aspects of differentiation, yet behavior is also an important component of evolutionary diversification, often mediating the relationship between animal ecology and morphology. In species within radiations that are convergent in ecology and morphology, we then also expect convergence in behavior. Here, we examined 13 Anolis lizard species to determine whether territorial strategies have evolved convergently with morphology and habitat use. We evaluated two aspects of territoriality: behavioral defense of space via territorial displays, and territory overlap within and between sexes. Controlling for the phylogenetic relationships of the taxa in our study, we found that species similar in perch height and diameter convergently evolved patterns of territory overlap, whereas species similar in habitat visibility (the proportion of space that can be seen from a perch) convergently evolved display behavior. We also found that species with greater display time have more extensive male–male territory overlap. This study provides strong evidence for the role of habitat in the evolution of territoriality and suggests that the social structure of a species ultimately evolves in concert with habitat use and morphology.     

Antagonistic fungal interactions influence carbon dioxide evolution from decomposing wood

Fungal species vary in the rate and way in which they decay wood. Thus, understanding fungal community dynamics within dead wood is crucial to understanding decomposition and carbon cycling. Mycelia compete for wood territory, by employing antagonistic mechanisms involving changes in morphology, and production of volatile and diffusible chemicals. This is metabolically costly, and may affect the rate of use of the resource. The metabolic rate during pairwise interactions between wood decay ascomycetes and basidiomycetes was determined by measuring CO₂ production. CO₂ evolution altered over time, but changes were combination-specific. In only two combinations – when the dominant competitor overgrew the opponent's territory as mycelia cords – did CO₂ evolution increase over the course of the whole interaction. In most interactions, CO₂ evolution increased only after complete replacement of one competitor, suggesting utilisation of the predecessor mycelium or differences in decay ability due to alteration of the resource by the predecessor. There was no relationship between rate of CO₂ evolution and combative ability nor outcome of interaction.     

Environmental influences on territoriality of juvenile brook charr,Salvelinus fontinalis,in a stream environment

Synopsis Juvenile brook charr, Salvelinus fontinalis, defending territories in a laboratory stream channel changed their defensive tactics when fish numbers or water current velocity were increased. The associated increase in energy costs of territorial defense were apparently reduced by using relatively more lateral displays and fewer chases to repel intruders, and by decreasing territory size. Territory size tended to increase with food ration, although levels of aggression were not affected. These results emphasize the importance of energetic considerations in territoral defense in these fish, and are discussed in terms of current hypotheses regarding the resource base for territoriality.     

Sex-specific territorial responses in Tawny Owls Strix aluco

A territorial intruder often poses more of a threat to the territory holder of the same sex as itself. As territorial aggression is associated with costs, aggression shown by birds towards territorial intruders of the opposite sex deserves investigation. This behaviour could arise due to the reproductive value of a mate or through mutualism between members of a pair. We investigated these hypotheses by presenting mated pairs of Tawny Owls Strix aluco with playback of male calls, female calls and a male and female duetting, and recording the number and intensity of responses by the male and female territory holders. Females responded significantly more often to female than to male calls. Males responded equally often to male and female playback. Males which had previously bred successfully with their mate were significantly more likely to respond to female playback in the spring, which suggested males were responding to female playback due to the reproductive value of their mate. There was no evidence of mutualism between members of a pair.     

Male song sparrows have elevated testosterone in response to neighbors versus strangers

Upon hearing a conspecific signal, animals must assess their relationship with the signaller and respond appropriately. Territorial animals usually respond more aggressively to strangers than neighbors in a phenomenon known as the “dear enemy effect”. This phenomenon likely evolved because strangers represent a threat to an animal's territory tenure and parentage, whereas neighbors only represent a threat to an animal's parentage because they already possess a territory (providing territory boundaries are established and stable). Although the dear enemy effect has been widely documented using behavioral response variables, little research has been conducted on the physiological responses of animals to neighbors versus strangers. We sought to investigate whether the dear enemy effect is observed physiologically by exposing territorial male song sparrows (Melospiza melodia) to playback simulating a neighbor or a stranger, and then collecting blood samples to measure plasma testosterone levels. We predicted that song sparrows would exhibit increased testosterone levels after exposure to stranger playback compared to neighbor playback, due to the role testosterone plays in regulating aggression. Contrary to our prediction, we found that song sparrows had higher testosterone levels after exposure to neighbor playback compared to stranger playback. We discuss several explanations for our result, notably that corticosterone may regulate the dear enemy effect in male song sparrows and this may inhibit plasma testosterone. Future studies will benefit from examining corticosterone in addition to testosterone, to better understand the hormonal underpinnings of the dear enemy effect.     

Cooperative nest‐defence behaviour and territory quality in a resident and socially monogamous passerine

Nest defence is a fundamental aspect of parental care in secondary cavity‐nesting birds, and predation or competition for nesting sites can involve different defensive behaviours. Because habitat quality determines breeding success, we were interested in whether breeding pairs of the Eurasian nuthatch, Sitta europaea, established in more favourable environment also manifest higher probability of cooperative behaviour during their nest‐site defence. To explore this relationship, we quantified behavioural displays of both parents and analysed activity budget ethogram data from simulated territorial intrusions performed in the chick‐feeding phase with one conspecific and two different heterospecific stimuli (dummies of nuthatch, starling and woodpecker). We found that paired individuals shared their roles during nest‐site defence to a considerable extent. Males had a significantly higher number of attacks on intruders than females, and females performed more threat displays and controls of the brood than males. Multinomial analysis of the cooperative behaviour suggested that pairs in a high‐quality territory had higher probability of reciprocal substitution of different roles towards a balance between attacks, threat displays and nest controls. Contrary to this, pairs in a low‐quality territory had less likely pairwise combinations of simultaneous behavioural states that are associated with effective nest‐site defence. The difference in response probability according to territory quality was, however, highly variable in view of the stimulus that was used in simulated territorial intrusion. Because individual roles and the complex behavioural repertoire of pairs altered in response to territory quality and potential nest‐site competitor or brood predator, our results suggest that the cooperative nest‐defence behaviour could be linked to the breeding success of this year‐round territorial species living in a heterogeneous forest habitat.     

Body size as a factor determining dominance in staged agonistic encounters between male brown anoles (Anolis sagrei)

The results of staged agonistic encounters between males indicate that body size is an important determinant of dominance in male brown anoles (Anolis sagrei). Larger males defended their perch sites more successfully than did smaller males, perched higher than smaller males, and were most often the first male to enter the other male's territory. Larger males also exhibited more challenge displays than did smaller males. Head-nods, a display given by subordinate individuals, were observed only in smaller males.     

The role of territory settlement,individual quality,and nesting initiation on productivity of Bell's vireos Vireo bellii bellii

Variation in habitat quality among territories within a heterogeneous patch should influence reproductive success of territory owners. Further, territory settlement order following an ideal despotic distribution (IDD) should predict the fitness of occupants if territory selection is adaptive. We recorded settlement order and monitored nests in territories occupied by individually marked Bell's vireos Vireo bellii bellii across a range of shrubland habitats in central Missouri, USA. We used an information theoretic approach to evaluate multiple hypotheses regarding the relationship between territory settlement order and seasonal territory productivity (productivity), which we define as the number of young fledged from all nest attempts in a territory. Territory settlement order and arrival date were not analogous and later arriving males displaced early settlers in 13 of 49 territories. Settlement order and lay date together were the best predictors of a territory's productivity; productivity decreased 2.08 young from earliest to latest settlement rank and lay date. Males that defended the same territory in successive years occupied territories with earlier settlement dates, but we found little evidence that age or prior ownership influenced productivity. Territory selection by male Bell's vireos was adaptive because males preferred to settle in territories that had high seasonal offspring production, but even though settlement rank was linked to territory quality, high productivity was only realized on high quality territory when also linked to early nest initiation date. While settlement rank was related to territory quality, obtaining a high quality territory had to be combined with early nest initiation to maximize productivity. We found support for the IDD hypothesis because the highest quality territories, (i.e. most productive), were settled earlier. Research that identifies high quality habitat by linking individual fitness with habitat characteristics may elucidate the importance of habitat quality, individual experience and temporal factors to productivity of Bell's vireos.     

Patterns of territory size and defence level in rural and urban tawny owl (Strix aluco) populations

The effect of different variables on the territory size and defence level of tawny owl ( Strix aluco L.) populations was studied in two habitats: mixed farmland (1976–1978) and town (1986–1988). Territory size was determined by plotting the position of territorial challenges (hoots) of males which were individually recognizable in most cases. No differences were found in size, defence, number of competitors and biomass between territories in farmland and in town, but territories in town were more fragmented and showed a larger nearest neighbour distance. Size of rural territories was adequately predicted both by some structural habitat features and food supplies, while size of urban territories was affected only by habitat structure and by years of territory occupancy. No effect on territory size by competing neighbours was found in either habitat, thus confirming that behavioural interactions between the owners of territories and potential settlers prevent a decrease of territory size.
Defence level of urban territories was affected by 'social'variables (nearest neighbour distance and years of occupancy), structural variables (percentage of poplar grove and diversity), and food supply, while in rural territories only structural variables (fragmentation or natural vegetation) and food supplies affected defence level.
This was due to different settlement tactics in the two areas, depending on the extent and quality of suitable habitat.     

Effectiveness of Avian Predator Perch Deterrents on Electric Transmission Lines

ABSTRACT A new high-voltage transmission line in north-central Nevada, USA, was considered a potential threat to greater sage-grouse (Centrocercus urophasianus) because avian predators are attracted to and hunt from elevated perches. As a mitigation measure, perch deterrents were installed on the transmission line towers at the time of construction; in addition, 2 existing high-voltage transmission lines were retrofitted with deterrents. Previous published studies have investigated the efficacy of perch deterrents in preventing or reducing electrocution of avian predators and fecal contamination of insulators, but none have evaluated deterrents as a means of eradicating perching on towers. We conducted point transect surveys and perching-duration observations of corvids and raptors and determined that although perch deterrents did not prevent perching, the perching duration of raptors on the deterrents was reduced compared to other perching substrates. Perching of raptors indicated that some hunting most likely took place from the towers; therefore, the deterrents did not completely obviate the threat that avian predators posed to greater sage-grouse. Although the deterrents reduced the probability of avian predators perching on the towers, avian predators overcame the deterrents to take advantage of the height of the towers where no other perches of similar height existed. The perch deterrents as designed did not have the desired short-term effect on avian predators, but further monitoring may reveal longer-term effects and distinguish perching behaviors specific to different species of avian predators.