Territory Owners Research Articles

Territory owners discriminate between aggressive and nonaggressive neighbours

In a territorial system where males vary in fighting ability or attractiveness to females, not all neighbours should be equally threatening to a territory owner. Selection should act on territory owners to recognize consistent individual differences between neighbours, assess which neighbours represent greater threats, and respond appropriately when challenged. In this study, we examined whether male song sparrows, Melospiza melodia, assess the level of threat posed by individual neighbours and respond differently to neighbours that differ in their level of aggressiveness. Aggressive males should represent a greater threat because they are more likely to engage in fights over territorial boundaries, and may also be preferred by females as extrapair mates. We used playback experiments to assay male territorial aggression, and then to test whether males responded differently to their aggressive and nonaggressive neighbours. We found that male song sparrows respond more strongly to their aggressive neighbours than to their nonaggressive neighbours. Thus, male song sparrows differentiate between neighbours that differ in aggressive response and appear to respond adaptively towards the individual that poses the greatest threat.

From Hawks and Doves to Self‐Consistent Games of Territorial Behavior

Explaining the "prior-residence effect" (automatic owner status of individuals who arrived first in an area) was one of the very first applications of game theory in animal behavior. These models, however, predict paradoxical solutions where intruders always win, with no satisfactory explanation for the absence of such cases in nature. We propose a solution based on new developments in evolutionary game theory. A self-consistent model with feedbacks between individual behavior and population dynamics produces qualitatively different frequency-dependent selection on intruders (floaters) than on territory owners. Starting with an ancestral population with no respect for ownership, the most likely evolutionary end point is complete or partial respect. Conventional rules of conflict resolution thus can rely on "uncorrelated asymmetries" without differences in resource-holding power or territory value, although they will be strengthened by such differences. We also review the empirical literature on animal contests, testing whether asymmetries in resource-holding power are required to explain the observations. Despite much empirical effort, results remain inconclusive, because experiments are often unable to distinguish between the motivation of individuals to fight and the behavioral outcome of a contest. To help arrive at conclusive answers, we suggest a standardized empirical approach to quantify prior-residence effects.

Vocal performance influences male receiver response in the banded wren

In a variety of songbirds the production of trilled song elements is constrained by a performance tradeoff between how fast a bird can repeat trill units (trill rate) and the range of frequencies each unit can span (frequency bandwidth). High-performance trills serve as an assessment signal for females, but little is known about the signal value of vocal performance for male receivers. We investigated the relationship between trill rate and frequency bandwidth in banded wren (Thryothorus pleurostictus) songs. Trilled song elements showed the same performance tradeoff found in other passerines and individuals differed in performance of some trill types. We tested the hypothesis that males of this species assess each other based on trill performance with a two-speaker experiment, in which territory owners were presented with alternating renditions of the same song type manipulated to differ in trill rate. Subjects were significantly more likely to approach the faster trill stimulus first. However, subjects that received trill types closer to the performance limit spent less time close to the fast speaker. Our results show that male banded wrens discriminate and respond differently to songs based on their vocal performance. Thus, performance of physically challenging songs may be important in intra- as well as inter-sexual assessment.

Context Dependent Territory Defense: The Importance of Habitat Structure in Anolis sagrei

AbstractTerritoriality is a potentially costly endeavor, and several mechanisms for mitigating the costs of territoriality have been investigated in the wild. For example, territory owners can reduce the costs of defending territory boundaries by prioritizing defense of the most valuable areas within territories, investing less energy in low quality areas. We staged pairwise encounters between adult male lizards on natural territories in the wild, to test whether male brown anoles, Anolis sagrei, would differentially defend certain regions of their territories over others. Based on our observations that male A. sagrei spend most of their time on elevated perches on tree trunks or branches compared with sites on the ground, we predicted that territory residents would respond more aggressively to territory invasions that took place on elevated perches than to invasions on the ground. We measured significant differences in the behavior of residents following invasion on the ground vs. on the elevated perches, and results partially supported our hypothesis. Males performed more displays and approached intruders more often when territory invasion took place on the ground, but were quicker to attack intruders that entered territories on elevated perches. Our hypothesis was only partially supported, potentially indicating that elevated perches are preferred as outposts to monitor valuable sites on the ground. Our study provides evidence that territory defense varies not just among individuals, but also within individuals at different locations in a territory.

Matching and Symmetry in the Frequency Recognition Curve of the Poison Frog Epipedobates trivittatus

AbstractIn territorial species, males use signals to advertise territory ownership to other males. In species with acoustic communication, masking interference by heterospecific signals may impede male–male communication and affect the reproductive success of males. Frogs are thought to minimize masking interference by using species‐specific frequency channels for communication. For this strategy to work, a frequency match is expected between the advertisement call and the auditory sensitivity. A previous field study on the Amazonian frog Epipedobates femoralis supported this prediction, but also revealed an asymmetric decrease in the probability of male reaction towards synthetic calls. That males of E. femoralis reacted less towards low‐frequency (compared with high‐frequency) calls was interpreted as a mechanism that reduces masking interference by E. trivittatus, a species calling within a lower, partially overlapping, frequency range. If this hypothesis holds, then males of E. trivittatus should exhibit the opposite asymmetry pattern, i.e. react less towards high‐frequency (compared with low‐frequency) calls. We tested this prediction by conducting 25 playback experiments on 22 males of E. trivittatus. Male phonotactic reaction towards synthetic calls of various frequency values was evaluated as a binary variable (the male either approached or not the loudspeaker), by measuring the latency until first jump, and by calculating the linear approaching speed. As in E. femoralis, the maximum probability of positive reaction was matched to the call frequency. Against our expectations, the response curve was symmetric. We discuss whether these results reflect a lack of selective pressures, or a compromise between natural selection and physiological constraints on the shape of the frequency recognition curves.

Year-long stability and individual differences of male long calls in Japanese pikas Ochotona hyperborea yesoensis (Lagomorpha) / Stabilité annuelle et differences individuelles des cris d'appels longs des mâles de pikas du Japon Ochotona hyperborea yesoensis (Lagomorpha)

Abstract Long calls of three adult male Japanese pikas were tape-recorded in the Taisetsuzan National Park, Hokkaido, Japan, from July 1996 to July 1998. A long call consisted of 3–13 elements, each with a characteristic W-shaped wave. There was apparent individual variation in sonographic patterns and the fundamental frequencies. Such individual variation did not differ with animal age, or through the reproductive and non-reproductive seasons. The complicated structure of W-shaped waves may involve much information concerning individual difference, and the repetition of elements in the long call may advertise sexual activity, location, and territorial ownership to opponents and mates, based on individual identification only by hearing calls.

From Hawks and Doves to Self-Consistent Games of Territorial Behavior

Explaining the “prior‐residence effect” (automatic owner status of individuals who arrived first in an area) was one of the very first applications of game theory in animal behavior. These models, however, predict paradoxical solutions where intruders always win, with no satisfactory explanation for the absence of such cases in nature. We propose a solution based on new developments in evolutionary game theory. A self‐consistent model with feedbacks between individual behavior and population dynamics produces qualitatively different frequency‐dependent selection on intruders (floaters) than on territory owners. Starting with an ancestral population with no respect for ownership, the most likely evolutionary end point is complete or partial respect. Conventional rules of conflict resolution thus can rely on “uncorrelated asymmetries” without differences in resource‐holding power or territory value, although they will be strengthened by such differences. We also review the empirical literature on animal contests, testing whether asymmetries in resource‐holding power are required to explain the observations. Despite much empirical effort, results remain inconclusive, because experiments are often unable to distinguish between the motivation of individuals to fight and the behavioral outcome of a contest. To help arrive at conclusive answers, we suggest a standardized empirical approach to quantify prior‐residence effects.

Year-long stability and individual differences of male long calls in Japanese pikas Ochotona hyperborea yesoensis (Lagomorpha) / Stabilité annuelle et differences individuelles des cris d'appels longs des mâles de pikas du Japon Ochotona hyperborea yesoensis (Lagomorpha)

AbstractLong calls of three adult male Japanese pikas were tape-recorded in the Taisetsuzan National Park, Hokkaido, Japan, from July 1996 to July 1998. A long call consisted of 3–13 elements, each with a characteristic W-shaped wave. There was apparent individual variation in sonographic patterns and the fundamental frequencies. Such individual variation did not differ with animal age, or through the reproductive and non-reproductive seasons. The complicated structure of W-shaped waves may involve much information concerning individual difference, and the repetition of elements in the long call may advertise sexual activity, location, and territorial ownership to opponents and mates, based on individual identification only by hearing calls.

Loud calling, spacing, and cohesiveness in a nocturnal primate, the Milne Edwards' sportive lemur (Lepilemur edwardsi)

Dispersed pair-living primates provide a unique model for illuminating the evolution of mechanisms regulating spacing and cohesiveness in permanently cohesive groups. We present for the first time data on the spatiotemporal distribution and loud-calling behavior of the Milne Edwards' sportive lemur, known to forage solitarily during the night, but to form stable male-female sleeping groups during the day. Data include radio-tracking observations of sleeping associations, and focal follows of pair partners during dispersal in the evenings and reunions in the mornings. Male-female pairs forming stable sleeping associations during the day were pair-bonded. They used sleeping sites and home ranges exclusively, and exchanged loud calls at potentially restricted resources during dispersal in the evenings and during reunion in the mornings. Direct agonistic conflicts between pairs and others were rare. The acoustic analysis of loud calls revealed nine major call types. They carry signatures for sex and pair identity, and provide the substrate for signaling and the potential for recognizing pair ownership. Thus, pairs use loud call exchanges as a vocal display for signaling territory ownership, thus limiting direct aggressive encounters between neighbors and strangers. Altogether, our findings provide the first empirical evidence for the hypothesis that loud calling has evolved as a key mechanism for regulating space use and cohesiveness in dispersed pair-living primates.

Territory revisits reduce intrusion during spawning trips by female yellowtail damselfish, Microspathodon chrysurus

When territory owners temporarily leave their territories, intrusion often increases. Periodic returns (revisits) may reduce intrusion, but not necessarily, because this tactic might increase total time away from the territory. The effectiveness of revisits also depends on a subsequent delay in the return of intruders. Adult female yellowtail damselfish briefly leave their territories in the early morning every 3 days to spawn. Some females make a single trip; others return to their territory several times before they finish spawning. To determine how much time females spent on revisits and whether it reduced intrusion, we observed revisits by multiple-trip females and compared intrusion on the territories of spawning and experimentally caged single-trip and multiple-trip females. If revisits reduce intrusions, multiple-trip females should have higher intrusions when caged than when spawning. If revisits show adaptive plasticity, caged single-trip females should have lower intrusion rates than caged multiple-trip females. Not counting the first trip to the male's nest and the final return trip, we estimated that spawning multiple-trip females averaged 86% of their time at the male's nest, 11% back in the territory and 3% travelling. When owners were spawning, territories of both single- and multiple-trip fish received about 5–7 min of intrusion. When owners were caged, intrusion increased significantly only on territories of multiple-trip females. We consider this the first direct evidence that revisits during temporary absences reduce intrusion on territories, suggesting that revisiting is a plastic trait that females may vary in response to intruder pressure.

Territorial responses of male blue tits to simulated dynamic intrusions: effects of song overlap and intruder location

Territorial songbirds frequently challenge each other with intrusions and close-range singing interactions. The timing of songs in such interactions may signal aggressive intentions and experiments have shown that song overlapping may indicate a higher willingness to escalate an interaction than song alternating. A territory owner should therefore perceive an intruder overlapping its songs and staying inside its territory as a greater threat than one alternating and exiting the territory quickly. To test this hypothesis we used playback to interact with territorial male blue tits, Parus caeruleus, by varying the amount of overlap of a subject's song; we also used multiple loudspeakers to simulate an intruder changing song posts. The territory owners approached and followed simulated intruders that changed song post inside their territories more slowly when more of their songs had been overlapped at the first loudspeaker, and they did not follow an intruder outside their territory. Nevertheless their responses remained high throughout playback and interaction terms between proportion of songs overlapped and loudspeaker position inside or outside the territory indicated that male blue tits combined and used information from both singing and intrusion patterns.

Group-specific vocal signatures and neighbour–stranger discrimination in the cooperatively breeding green woodhoopoe

Group displays involving vocal choruses are a prominent feature of many avian cooperative-breeding systems. The existence of group-specific vocal signatures within these choruses could assist territory owners when assessing the threat posed by different intruding groups. To investigate the possible presence of such signatures, I examined the choruses (‘rallies’) given by 22 green woodhoopoe, Phoeniculus purpureus, groups over two consecutive seasons. A rally involved the combined cackling of adult group members. Statistical analysis of midrally vocalizations, when all group members were calling, revealed that samples from the same group clustered in principal coordinate space, and the group clusters segregated from each other to a significant degree. This segregation might theoretically arise from differences in group size and sex ratio, especially since the vocalizations are sexually dimorphic. However, groups containing the same numbers of males and females had rallies that were significantly different acoustically. Groups that maintained the same composition of individuals produced acoustically similar rallies across seasons, while those that changed membership produced significantly different rallies. The group signature is therefore most likely to result from group members producing their own individual vocal programmes, but participating in a similar way for every rally. In a playback experiment, groups responded significantly more rapidly to strangers and to neighbours on the wrong boundary than to neighbours in their expected place. Woodhoopoes therefore appeared capable of distinguishing between groups on the basis of their vocal signatures, representing the first evidence of the ‘dear-enemy’ phenomenon in a group-living species.

Vocal behavior and risk assessment in wild chimpanzees

If, as theory predicts, animal communication is designed to manipulate the behavior of others to personal advantage, then there will be certain contexts in which vocal behavior is profitable and other cases where silence is favored. Studies conducted in Kibale National Park, Uganda investigated whether chimpanzees modified their vocal behavior according to different levels of risk from intergroup aggression, including relative numerical strength and location in range. Playback experiments tested numerical assessment, and observations of chimpanzees throughout their range tested whether they called less frequently to avoid detection in border areas. Chimpanzees were more likely to call to playback of a stranger’s call if they greatly outnumbered the stranger. Chimpanzees tended to reduce calling in border areas, but not in all locations. Chimpanzees most consistently remained silent when raiding crops: they almost never gave loud pant-hoot calls when raiding banana plantations outside the park, even though they normally give many pant-hoots on arrival at high-quality food resources. These findings indicate that chimpanzees have the capacity to reduce loud call production when appropriate, but that additional factors, such as advertising territory ownership, contribute to the costs and benefits of calling in border zones.

Nest use by territorial males in a shell-brooding cichlid: the effect of reproductive parasitism

Male Telmatochromis vittatus, a substrate-brooding Tanganyikan cichlid, exhibit two parasitic reproductive tactics: takeover of spawning by larger males (“pirates”) and sneaking by smaller males (“sneakers”). Medium-sized males are territorial and pair-spawn within nests of clumped shells that harbor several resident females that are potential mates of the territory owner. To study nest use by territorial males, we analyzed the relationship between the body size of territorial males and nest quality, the number of females per nest, the distance between nests, and the frequency and intensity of reproductive parasitism. The size of males was not correlated with nest quality, the number of females, or the number of sneakers, but was negatively correlated with the frequency of intrusion by pirates and was positively correlated with the distance between nests. Territorial males effectively defended nests against sneakers but failed to defend against pirates. These results suggest that larger territorial males selected nests that have a lower risk of usurpation of spawning. We hypothesize that the risk of intrusion by pirate males affects the selection of nests by territorial males in this species.

Direct and Indirect Mate Choice on Leks

Indirect mate choice is any behavior that restricts the individual's set of potential mates without discrimination of mate attributes directly, for example, by having preferences about where to mate. We analyzed a 14-year data set from great snipe (Gallinago media) leks for evidence of indirect mate choice based on relative and absolute position of lek territories. We found little or no effect of the centrality of territories on mating and no between-year consistency in the spatial distribution of matings within leks. Instead, the probability of matings occurring at a particular site increased if the current territory owner had mated the previous year. Furthermore, individual females returned in later seasons to mate with the same male as previously rather than at the same site. Previous work found that male interactions and dominance do not control matings and that females are very choosy about which territory they mate in. Here we show that this is because of the male occupying the territory rather than its position. We therefore conclude that direct female mate choice is the main behavioral process affecting variation in mating success among great snipe males, unlike in some lekking mammals where male competition and/or indirect mate choice appears more important.

Tests of spatial and temporal factors influencing extra‐pair paternity in red‐winged blackbirds

Extra-pair paternity (EPP) is a widespread and highly variable reproductive phenomenon in birds. We tested the effects of habitat, spatial factors, and timing of breeding on the occurrence of EPP in red-winged blackbirds (Agelaius phoeniceus). We used PCR-amplified microsatellites to assess the paternity of 1479 nestlings from 537 broods on 235 territories over four breeding seasons. Over 4 years, 40% of nestlings were extra-pair. At least 27% of actual sires were non-neighbours, suggesting that males or females interacted over longer distances than in other populations of red-winged blackbirds. The level of EPP was significantly clumped within broods and males but not within females across broods. EPP was negatively related to the area of a male's territory. The spatial proximity of a female's nest to the territory boundary had no effect on total EPP, but tended to increase the probability of an EPP by a nearby male. We found no influence on EPP of the type of habitat on the territory or the level of nesting activity nearby. The time in the season when a nest was started and the synchrony of breeding also had no significant effect on the level of EPP. The age of the male, the age of his neighbours, and the interaction between the two had no effect on total EPP. However, older males were less likely to have an offspring sired by a neighbour on their territory. Males with older neighbours were also less likely to have offspring sired by a neighbour, particularly if they were new territory owners. The high variability in who gained and lost paternity, and the limited impact of spatial and temporal factors influencing it, have some interesting implications for theories seeking to explain mating patterns.

Opponent recognition in male green anoles, Anolis carolinensis

Male green anoles convey territorial ownership to rivals through use of stereotyped aggressive displays, with intrasexual interactions often escalating to physical combat. In the laboratory, losers of such interactions significantly reduce their aggressive behaviour when interacting with the same opponent 7 days later. In the current study, we examined whether this behavioural modification is a function of opponent recognition. Pairs of size-matched male A. carolinensis were allowed to interact for 2 h. Following this, subjects were separated for varying intervals, and then participated in a second interaction with either the same or an unfamiliar opponent. Losers of the first interaction significantly reduced their total aggressive behaviour when re-paired with the same opponent after a 3-day interval but not after a 10-day interval between the first and second interaction. However, losers of the first interaction failed to show reduced aggression during their second interaction when paired 3 or 10 days later with an unfamiliar opponent. Therefore, A. carolinensis appear to learn information specific to their opponent during an initial agonistic interaction, with the salience of this information declining when the interval between interactions increases. Males also showed low levels of chemosensory taste behaviour during agonistic interactions, suggesting that opponent recognition does not rely on chemoreception. Similarities between our results and findings from other vertebrate species suggest that the motivation to behave aggressively during social interactions can be influenced by opponent recognition rather than by previous experience of social defeat alone.

Territorial behavior of Favonius taxila (Lycaenidae): territory size and persistency

Territorial behavior of the hairstreak, Favonius taxila Bremer 1861, was investigated in Aomori Prefecture, Japan. Males were active in the morning hours, during which they showed territorial behavior. Territorial males persistently perched on almost the same leaf or a shoot and occasionally flew around a limited area, here referred to as inspection area. When another male intruded into this area, the resident and the intruder engaged in a circling flight. The flight occasionally strayed to outside of the inspection area, where it was terminated. The resident returned to his territory in most cases, but in a few cases, exchange of the territory owner occurred. In one case, a single butterfly occupied his territory throughout the observation period of 5 days, whereas in another, several times of exchanges occurred.

The Advancement of Japanese to the Senkaku Islands and Tatsushiro Koga in the Meiji Era

The Senkaku Islands are made up of five uninhabited islands scattered about 170km north of the Yaeyama Islands of Okinawa Prefecture. In recent years the territorial claims on these islands made by China and Taiwan have increased since it was found that under that area there is a lot of petroleum and natural gas. No one has ever sufficiently examined why Japanese people in the Meiji Era started going to these islands made only of rocks. This study discusses the Japanese advance into and the development of the Senkaku Islands. The following is its summary;The territorial possession of the uninhabited Senkaku Islands started with the exploration by the Okinawa Prefectural Government in 1885, and the exploration report says that a large flock of albatross was found there. In the 1890's, the Japanese advance into the Senkaku Islands was accelerated in order to get the albatross plumage and the great green turban. In those days the Okinawa Prefectural Government had to plead with the Meiji Central Government again and again to put national landmarks on the islands because it was not clear whether the islands were actually Japanese or Chinese territory. Finally in 1894, the Meiji Government permitted to put the national landmarks. In 1895 the Senkaku Islands were placed under the jurisdiction of Okinawa Prefecture. In the same year, Tatsushiro Koga, who was a powerful and wealthy shellfish merchant, asked the Meiji Government to lease Kuba Island for the purpose of catching albatross because of the rapid decrease of the great green turban. His business changed from shellfish to albatross. In 1896, the Government not only leased Kuba Island to him but also granted him the lease of another four Senkaku Islands for 30 years.In 1897 Koga started his business in the Senkaku Islands, but albatross, his main resource of business, decreased devastatingly in only three years. Therefore, he diversified his business into stuffed birds, bonito fishing, guano, and phosphate rocks and managed to make an immense profit. But his business didn't last long because he mismanaged the natural resources on the islands. Koga Village, founded in Uotsuri Island with a huge investment of money, disappeared in about 30 years and around 1937 the Senkaku Islands again became uninhabited with no change since then.

Scent wars: the chemobiology of competitive signalling in mice

Many mammals use scent marks to advertise territory ownership, but only recently have we started to understand the complexity of these scent signals and the types of information that they convey. Whilst attention has generally focused on volatile odorants as the main information molecules in scents, studies of the house mouse have now defined a role for a family of proteins termed major urinary proteins (MUPs) which are, of course, involatile. MUPs bind male signalling volatiles and control their release from scent marks. These proteins are also highly polymorphic and the pattern of polymorphic variants provides a stable ownership signal that communicates genome-derived information on the individual identity of the scent owner. Here we review the interaction between the chemical basis of mouse scents and the dynamics of their competitive scent marking behaviour, demonstrating how it is possible to provide reliable signals of the competitive ability and identity of individual males.