Analysis of a model for wolf territories

 A mechanism for territorial pattern formation in wolves is analysed using a spatially explicit mathematical model which incorporates wolf movement and scent marking. Model results reflect field observations: buffer zones where wolves are scarce arise between adjacent packs and near these buffer zones there are increased levels of scent marking. It is shown how the precise behavioral response of wolves to foreign scent-marks determines the qualitative form of the spatial territories. Realistic territories in two spatial dimensions require ‘switching’ of the movement and scent marking behavior in response to foreign scent marks. Received 20 October 1995; received in revised form 17 May 1996     

Animal interactions and the emergence of territoriality

Inferring the role of interactions in territorial animals relies upon accurate recordings of the behaviour of neighbouring individuals. Such accurate recordings are rarely available from field studies. As a result, quantification of the interaction mechanisms has often relied upon theoretical approaches, which hitherto have been limited to comparisons of macroscopic population-level predictions from un-tested interaction models. Here we present a quantitative framework that possesses a microscopic testable hypothesis on the mechanism of conspecific avoidance mediated by olfactory signals in the form of scent marks. We find that the key parameters controlling territoriality are two: the average territory size, i.e. the inverse of the population density, and the time span during which animal scent marks remain active. Since permanent monitoring of a territorial border is not possible, scent marks need to function in the temporary absence of the resident. As chemical signals carried by the scent only last a finite amount of time, each animal needs to revisit territorial boundaries frequently and refresh its own scent marks in order to deter possible intruders. The size of the territory an animal can maintain is thus proportional to the time necessary for an animal to move between its own territorial boundaries. By using an agent-based model to take into account the possible spatio-temporal movement trajectories of individual animals, we show that the emerging territories are the result of a form of collective animal movement where, different to shoaling, flocking or herding, interactions are highly heterogeneous in space and time. The applicability of our hypothesis has been tested with a prototypical territorial animal, the red fox (Vulpes vulpes).     

Territorial dynamics and stable home range formation for central place foragers

Uncovering the mechanisms behind territory formation is a fundamental problem in behavioural ecology. The broad nature of the underlying conspecific avoidance processes are well documented across a wide range of taxa. Scent marking in particular is common to a large range of terrestrial mammals and is known to be fundamental for communication. However, despite its importance, exact quantification of the time-scales over which scent cues and messages persist remains elusive. Recent work by the present authors has begun to shed light on this problem by modelling animals as random walkers with scent-mediated interaction processes. Territories emerge as dynamic objects that continually change shape and slowly move without settling to a fixed location. As a consequence, the utilisation distribution of such an animal results in a slowly increasing home range, as shown for urban foxes (Vulpes vulpes). For certain other species, however, home ranges reach a stable state. The present work shows that stable home ranges arise when, in addition to scent-mediated conspecific avoidance, each animal moves as a central place forager. That is, the animal's movement has a random aspect but is also biased towards a fixed location, such as a den or nest site. Dynamic territories emerge but the probability distribution of the territory border locations reaches a steady state, causing stable home ranges to emerge from the territorial dynamics. Approximate analytic expressions for the animal's probability density function are derived. A programme is given for using these expressions to quantify both the strength of the animal's movement bias towards the central place and the time-scale over which scent messages persist. Comparisons are made with previous theoretical work modelling central place foragers with conspecific avoidance. Some insights into the mechanisms behind allometric scaling laws of animal space use are also given.     

The Equivocal Relationship Between Territoriality and Scent Marking in Wild Saddleback Tamarins (<Emphasis Type="Italic">Saguinus fuscicollis</Emphasis>)

Researchers have often assumed that scent marking serves a territorial function in callitrichines, although some controversy exists. To fulfill such a function, scent marks should 1) prevent intrusions, 2) ensure access to feeding resources, 3) enable avoidance of intergroup encounters, or 4) play an important role in the aggressive encounters between groups. We studied 13 saddleback tamarins (Saguinus fuscicollis) belonging to 3 free-ranging groups, which formed mixed-species troops with moustached tamarins (S. mystax) in the Amazonian rain forest of Peru. None of the predictions were confirmed. The tamarins used a border-marking strategy, marking more on the periphery of their territory. However, feeding trees in overlap and encounter areas received more scent marking but were still visited by neighboring groups. Intergroup encounters occurred more often than expected, and scent-marking frequency was not higher during them than when no other group was present. It appears that instead of defending a territory in the classic sense, the tamarins are optimizing signal transmission by depositing their scents where the probability of detection by neighbors is higher. Saddleback tamarins may use shared areas of their home ranges to exchange information with neighboring groups, perhaps regarding reproductive opportunities.     

Spatial patterns of scent marking in wild moustached tamarins, Saguinus mystax: no evidence for a territorial function

I investigated whether scent marking has a territorial function in wild moustached tamarins. I examined the spatial distribution of scent marking within the home ranges of four groups of this neotropical primate and tested predictions from Gorman & Mills' (1984, Journal of Zoology,202, 535-547) model for border and 'hinterland' marking. Although home ranges were economically defensible, no evidence was found for increased marking along the territorial boundary or in areas of home range overlap, but there was also no evidence for hinterland marking. Observed distributions of scent marking in exclusively used and overlapping areas of the home range did not deviate from distributions that would be expected if scent marking occurred at random (expectation based both on size of area and on frequency of quadrat occupation), and there was a strong correlation between frequency of quadrat occupation and frequency of scent marking per quadrat. These results indicate that scent marking has no territorial function in moustached tamarins. This is in line with mainly qualitative findings from the majority of other studies on wild marmosets and tamarins. These and other findings on scent marking in moustached tamarins suggest that this behaviour functions mainly in intersexual communication. Copyright 2000 The Association for the Study of Animal Behaviour.     

An Observational Study of Coyote (Canis latrans) Scent-marking and Territoriality in Yellowstone National Park

Free-ranging coyotes ( Canis latrans ) living in neighboring packs were observed in the Lamar Valley of Yellowstone National Park, Wyoming, from Jan. to May 1997. Through direct observation, we recorded the location of coyote scent marks and information regarding the identity of the marking animal. Patterns of scent-marking were then analyzed spatially and demographically. All of the evidence from the present study supports a strong relationship between scent-marking and territoriality in these coyotes, and all predictions were met. A preponderance of scent marks was found in the periphery of territories. Most of those marks were raised-leg urinations (RLUs) and forward-lean urinations (FLUs), postures associated very strongly with males, particularly dominant individuals. Ground-scratching was also closely associated with these types of marks and was performed more on the periphery of territories than in the interior. A complete lack of overlap of adjacent territories and very limited overlap of movements into territories fits classic definitions of territory and home range. Scent-marking seems to be strongly associated with the establishment and maintenance of these boundaries between packs of coyotes competing for the same resources in a limited space.     

Scent marking within and between groups of wild banded mongooses

Scent marking is commonly described as a territorial behaviour, and scent marks might deter potential intruders from entering occupied areas. Conspecific neighbours present both a reproductive and a territorial threat, thus, determining which, if any, of these threats shapes scent-marking behaviour is difficult. Banded mongooses Mungos mungo provide a rare clear separation between reproductive rivals (found within groups) and territorial rivals (neighbouring groups), because immigration into social groups is extremely rare, and mating occurs almost exclusively within groups. This situation offers an opportunity to assess the relative importance of territorial defence and intra-group competition for mates in shaping scent-marking behaviour. We combined detailed behavioural observations of scent marking, chemical analyses of scent composition and discrimination experiments in the field, and found little evidence for higher rates of scent marking in overlapping areas, a lack of group specificity of scents and a failure of individuals to discriminate between the scents of different groups. Although scent may fulfill some role in territorial demarcation and defence, these results suggest that scent marks and scent-marking patterns are also involved in communicating within social groups.     

Territory surveillance and prey management: Wolves keep track of space and time

Identifying behavioral mechanisms that underlie observed movement patterns is difficult when animals employ sophisticated cognitive‐based strategies. Such strategies may arise when timing of return visits is important, for instance to allow for resource renewal or territorial patrolling. We fitted spatially explicit random‐walk models to GPS movement data of six wolves (Canis lupus; Linnaeus, 1758) from Alberta, Canada to investigate the importance of the following: (1) territorial surveillance likely related to renewal of scent marks along territorial edges, to reduce intraspecific risk among packs, and (2) delay in return to recently hunted areas, which may be related to anti‐predator responses of prey under varying prey densities. The movement models incorporated the spatiotemporal variable “time since last visit,” which acts as a wolf's memory index of its travel history and is integrated into the movement decision along with its position in relation to territory boundaries and information on local prey densities. We used a model selection framework to test hypotheses about the combined importance of these variables in wolf movement strategies. Time‐dependent movement for territory surveillance was supported by all wolf movement tracks. Wolves generally avoided territory edges, but this avoidance was reduced as time since last visit increased. Time‐dependent prey management was weak except in one wolf. This wolf selected locations with longer time since last visit and lower prey density, which led to a longer delay in revisiting high prey density sites. Our study shows that we can use spatially explicit random walks to identify behavioral strategies that merge environmental information and explicit spatiotemporal information on past movements (i.e., “when” and “where”) to make movement decisions. The approach allows us to better understand cognition‐based movement in relation to dynamic environments and resources.     

Sex difference in the communicatory significance of localized defecation sites in Arabian gazelles (Gazella arabica)

Mammalian scent marking in localized defecation sites (latrines) has often been interpreted in the context of (male) territory defense. However, latrines could have different functions in males and females, especially where territorial males monopolize groups of females with stable social alliances and pronounced home range overlap. We investigated the communicatory significance of latrines in wild Arabian gazelles (Gazella arabica) and assessed the spatial distribution of latrines within home ranges. Latrine density and utilization was highest in the center of female group home ranges, and less frequent in peripheral home range sections, pointing towards communication within groups rather than towards territoriality. When considering male home ranges, latrine densities and utilization were higher in non-overlap zones, contradicting a territorial function. This pattern appears to be caused by more females than territorial males per given area establishing latrines. A subsequent survey of latrine utilization, based on camera trapping, suggests that males use latrines for territory defense: males visited latrines in overlap zones disproportionally more often than females, and successions of two males prevailed. Our study thus highlights that male territorial marking can be masked when males and females use the same marking system for different purposes.     

Temporal and Spatial Distribution of Male Scent Marks in the Polygynous Greater Sac-Winged Bat

Scent marks are relatively long-lived signals that can be perceived by conspecifics when the producer is absent. Therefore, it is often not obvious to whom the signal is directed. In daytime roosts of the polygynous greater sac-winged bat, males scent mark territories with facial gland secretions. Territories are a valuable resource for males, as they offer exclusive courtship opportunities, which results in increased male reproductive success and, consequently, increased male–male competition over territories. The information encoded in male scent marks could, therefore, be either directed at females as part of an olfactory courtship display or at male competitors as part of territorial behaviour. We expected territorial males to scent mark in the morning, shortly before females return to the territory and close to female roosting sites, if scent marks are directed at females as part of the courtship display. And we expected harem males to scent mark at the territory boundaries, where male–male encounters are most likely to occur, if scent marks are directed at male competitors. We found that males marked more frequently in the afternoon, at a time when all females have already left the territory, and harem males marked at the territory boundaries and not inside their territory in the area where females roost. At boundaries males fan volatiles from specialised wing sacs towards competitors outside the territory. Scent marking of male Saccopteryx bilineata might therefore be congruent with the assessment-hypothesis, which states that scent marks offer intruders the possibility to make an olfactory assessment of the territory owner without direct physical interaction. Thus, scent marks of male S. bilineata are most likely influenced by male–male competition and not by female choice.     

Potential risks of olfactory signaling: the effect of predators on scent marking by beavers

Mammals scent mark their territories to advertise occupancyand ownership. However, signaling with scent for territorialdefense can have a negative effect by advertising an individual'spresence and location to predators. In this study, we measuredresponses to a simulated territorial intrusion by conspecificadult male Eurasian beavers (Castor fiber) either in the localizedpresence or in the absence of odor of a predator to test thehypothesis that the territorial defense of free-living beaverswould be disrupted by the presence of predation risk in theirnatural environment. We predicted that beavers would significantlyreduce their willingness to countermark intruder's scent inthe presence of the scent of predators (wolf [Canis lupus] andlynx [Lynx lynx]), compared with a control (no odor), as responsesare in general stronger to predator scent marks than nonpredatorscent. Therefore, we also predicted that the effects of nonpredatorymammal scent (neophobic control) (eland [Taurotragus oryx] andhorse [Equus cabalus]) are to be expected somewhere in betweenthe effects of the predator odor and a control. Our resultssuggest that both predator and nonpredator scents reduce beaversresponse to a simulated intruder's scent mounds and thereforedisrupt their territorial defense. However, predator scent hada stronger effect than nonpredator scent. Beavers may thereforebe at great risk on territories with predators present becauseof the trade-off between predator avoidance and territorialdefense. Our study demonstrates the potential of predation riskas a powerful agent of counterselection on olfactory signalingbehavior.     

Varied tastes: home range implications of foraging‐patch selection

Despite evidence of home range behaviour across many taxa, the mechanisms underlying the development of home ranges are still unknown. Recently, models have been developed to explore these mechanisms for both territorial and non‐ territorial species. One such model for a generic forager suggests animal memory and optimal foraging theory as underlying mechanisms driving forager movement and the development of stable home ranges. Although this is a promising model for ungulate home range development, assumptions of the model have yet to be evaluated. Using GPS relocation data from two populations of elk, we explored how foraging patch selection might influence the structure and development of home ranges in elk Cervus elaphus. During the summer growing season, we identified and sampled foraging patches used by elk. Points along elk paths not used for foraging were sampled identically for comparison. We contrasted ‘patch’ and ‘nonpatch’ data points, to identify foraging selection differences across herd, sex and season using a combination of directly sampled and remotely sensed covariates. In general, elk selected patches with higher biomass, cover, slope and lower traffic on the nearest road. These patch‐selection results speak directly to differences between foraging areas and other areas used by elk and demonstrate that both physiographic and anthropocentric features influence foraging patch selection. Our results offer insight as to what defines a valuable foraging patch for elk and how these patches might influence the development and structure of home ranges in a free‐ranging ungulate.     

Detection of the Sexual Identity of Conspecifics through Volatile Chemical Signals in a Territorial Salamander

Territorial red‐backed salamanders (Plethodon cinereus) have been shown to use nonvolatile chemical signals in both territorial defense and to convey a variety of information to conspecifics. We investigated whether or not red‐backed salamanders could determine the sexual identity of conspecifics through volatile chemical signals, and we explored their use in the context of territorial defense. We exposed male and female red‐backed salamanders to four experimental treatments (i.e. filter papers that had been scent marked by male or female conspecifics for 1 and 5 d) and two control treatments (i.e. unscented filter papers for 1 and 5 d tests). The focal salamanders were prevented from physically accessing the scent marked filter papers and, presumably, some of the substrate scent marks had volatile components that were detected and interpreted by the focal salamanders. Both male and female red‐backed salamanders spent significantly more time in threat displays when they were exposed to volatile chemical signals from same‐sex conspecifics than they did toward similar signals from opposite‐sex conspecifics. A similar statistical pattern was observed for the amount of chemosensory sampling exhibited by focal red‐backed salamanders. From these results, we infer that red‐backed salamanders can determine the sexual identity of conspecifics through volatile chemical signals, some of which may be used in territorial defense. Further, such airborne pheromones may influence the spatial organization of salamander territories on the forest floor.     

Tradition in Lemur catta Behavior at Berenty Reserve,Madagascar

Lemur catta Troop D at Berenty Reserve has been studied intermittently for 35 years. During 90 hours of continuous sampling in August 1998, I observed and mapped troop movement and scent marking. I compared these observations with data from June, 1975. The core of Troop D1's 1998 home range is the same as for Troop D in 1975. Sixty-two percent of Troop D1's time in 1998 was spent in the 1975 home range, and 52% of their scent marks were placed in that 1975 home range. The remainder of their time was spent in an extension of their home range, which is now an area of confrontation with an adjacent troop. They used the same sleeping trees in the 2 years, and all of the 1998 scent marks deposited in the 1975 home range were placed in the same locations marked in 1975. The similarities in their use of space in 1975 and 1998 were remarkable.     

Olfactory demarcation of territorial but not home range boundaries by Lemur catta

Over 350 h of observations were collected using focal animal sampling of scent-marking behavior by 2 troops of ring-tailed lemurs (Lemur catta) in the field in Madagascar. Although they did not mark any branch species preferentially, they did have preferred marking sites. Significantly more scent marks were deposited in the area of home range overlap between troops than in the area of exclusive use. However, few marks were deposited at the periphery of the area of overlap. Instead, the majority of the marks were in a narrow band within the area of overlap that coincided with the positions of intertroop confrontations. Female genital marks and male arm marks, as well as the accompanying male shoulder rubs thus appear to demarcate territorial borders.     

The scent-marking behaviour of the spotted hyaena Crocuta crocuta in the southern Kalahari

All hyaenas scent mark their territories by smearing grass stems with paste from their subcaudal scent glands and by depositing faeces at latrines, but they adopt different strategies in terms of how they disperse these scent marks in their territories. For example, brown hyaenas living in the southern Kalahari deposit pastes and latrines throughout the whole of their territory, while spotted hyaenas living in the Ngorongoro Crater of East Africa place their scent marks strictly along the territorial borders. We have argued elsewhere (Gorman & Mills, 1984) that these different strategies are not species-specific but are instead adaptive responses to local conditions. Here, we use data from a population of spotted hyaenas, living in small clans and large territories in the Kalahari, to test the hypothesis that hinterland marking is a response to the problem of marking a very large territory with a limited amount of scent and within a limited time budget.     

Spatial Dispersion and Nonmigratory Spawning in the Bluehead Wrasse (Thalassoma bifasciatum)

Earlier studies of the behavior of the bluehead wrasse Thalassoma bifasciatum have shown it to be a migratory spawner with large terminal-phase males defending temporary spawning territories. We describe a variant social structure where fish occupy permanent home ranges, spawn within or near these home ranges, and are not territorial. Movements of identified terminal-phase and intermediate males and females were mapped in the backreef areas of three coral reefs in Puerto Rico. Locations of spawns were then compared with these home-range maps. All fish used most or all of their morning home range during the afternoon spawning period. Both terminal-phase males and females spawned within or near their home ranges. Males were relatively tolerant of other males during the afternoon spawning period: only one in five encounters between large males resulted in aggressive chases. The location of chases bore no relation to spawning sites, areas of morning foraging, or to home-range borders. A Monte Carlo computer simulation was used to measure home-range dispersion of terminal-phase and intermediate males at our main site. If males were territorial, we should expect their home ranges to be significantly overdispersed within the cumulative area they occupied. During the first year male home ranges were overdispersed but during the second year they were randomly dispersed, even though the same number of terminal-phase males occupied the same study site both years. Differences in social behavior between backreef areas and other areas reported in the literature, and found in other portions of our reefs, may be related to differences in feeding ecology between populations and between different portions of the same reef.     

Home ranges in red fox: territoriality diminishes with increasing area

Red foxVulpes vulpes (Linnaeus, 1758) are generally regarded as strictly territorial animals, inhabiting distinct and well-separated ranges. The home ranges of these predators can vary in size from a few dozen hectares to as much as 20–30 km². Because it seemed impossible that foxes could defend areas so different in size with the same intensity, the published data were analysed in order to see how changes in home range size could affect the following parameters: home range overlap, the area visited daily and the distance travelled by animals during 24 h. It was found that the overlap between fox families (groups) occupying large ranges was much greater than between foxes living in small ranges. The ratio of the area visited daily to the seasonal home range size was greater in small ranges than in large ones. No significant correlation was found between the mean distance moved daily and home range size (r = −0.118,p = 0.75). These results suggest different patterns of the use of space and differences in territorial defence by red foxes inhabiting large and small ranges. The implications of home range overlap and intensity of contacts between foxes occupying neighbouring ranges for the spread of disease are discussed. The significant overlap between large ranges found in this paper is discussed in the light of Andrzejewski’s (2002) home range concept.

     

Species and subspecies specificity in urine and scent marks of saddle-back tamarins (Saguinus fuscicollis)

Saguinus fuscicollisproduces scent marks which consist mainly of a mixture of urine and the secretions of circumgenital scent glands. The present study investigates the ability of saddle-back tamarins to discriminate between scent material from conspecifics and corresponding material from other species and to differentiate material from two subspecies of Saguinus fuscicollis.When choices between urine samples from conspecifics and from guinea pigs and choices between urine samples from conspecifics and from common marmosets were offered, the tamarins investigated samples from conspecifics more frequently. Similar responses were obtained when choices between scent marks from saddle-back tamarins and from common marmosets and between scent marks from saddle-back and red-chested moustached tamarins were offered. The tamarins also discriminated between scent marks and between extracts of scent marks from Saguinus f. fuscicollisand Saguinus f. illigeri.In these choice tests, subjects of both subspecies tended preferentially to investigate material from Saguinus f. fuscicollis.The results of these studies show that urine and scent marks contain chemical cues on which recognition of conspecifics can be based. Moreover, the scent marks of closely related subspecies also offer cues which could enable the tamarins to discriminate between them.     

Scent‐marking behavior by subordinate Eurasian beavers

Chemical communication by scent‐marking is widespread among mammals and can serve different purposes, such as territory demarcation, mate attraction and self‐advertisement. In this study, we examined scent‐marking behavior by subordinate Eurasian beavers (Castor fiber) in a population in southeast Norway. We conducted scent experiments in 18 family groups, simulating a territory intruder using experimental scent mounds (ESM). In total, we recorded 196 territorial reactions (destroying and/or overmarking of scent mounds). Subordinates contributed 14% of all territorial reactions and first overmarked 12% of the ESM, and the number of subordinates in the family group did not increase the total number of territorial reactions. This suggests that the contribution by subordinates plays a minor role in territorial defense. The number of territorial reactions by subordinates was positively related to the age of their parents, suggesting that subordinates might take over territorial duties with increasing parental senescence, likely because they have increased chances of inheriting the territory. Increased experience in territorial activities possibly helps subordinates to successfully gain and defend a territory of their own.