Optimal patterns of scent marks in klipspringer (Oreotragus oreotragus) territories

The distribution of preorbital gland scent marks and dung middens within three territories of wild klipspringers in Zimbabwe are described. Nearest-neighbour analyses revealed that scent marks were distributed non-randomly and in a rough ring some distance within the territory boundary. Marking densities were greatest at about half the territory radius. In two territories, marking densities were shown to be sensitive to intrusion pressure at the periphery, being higher along contested boundaries than where territories were not contiguous. Marks were placed on branches facing neighbouring territories, where they are more likely to be detected, along contested boundaries but not in other areas. An analytical model is developed which tests the efficacy of scent-marking strategies along the continuum between extreme hinterland and extreme perimeter marking. This shows that the optimal position for a ring of scent marks is at 0.78 of the territory radius and is the product of a trade-off between maximizing the probability of mark detection by intruders and minimizing the cost of intrusion.     

Behavioural mechanisms of information transmission and reception by badgers, Meles meles, at latrines

We investigated the behavioural mechanisms by which European badgers receive and transmit information at shared defecation sites (latrines). We surveyed locations of 143 latrines to establish factors influencing latrine position, and monitored the behaviour of badgers at latrines. Badger latrines were significantly closer to tree trunks than were random samples, and were more likely to be associated with conifers than broadleafs. This may serve to protect scent marks from erosion. Latrines were also placed more closely to linear features than expected; linear features may channel the movements of badgers, promoting discovery of latrines. Within latrines, badgers differed in their placement of faeces and subcaudal scent marks. Faeces were placed in a subset of pits, which were used for several consecutive nights, then abandoned for another subset of pits. Subcaudal scent (squat) marks were positioned in prominent places, and there was no consistent tendency to overmark. Meetings were rare at latrines. Sniffing was the most common behaviour, and was focused on defecation sites. At least three distinct behaviours that appear to serve an information transfer function were observed: squat marking; defecation; and digging and scuffing. Squat marking and defecation were performed by all age and sex classes, and may have a role in cross-territorial communication. Digging and scuffing were associated with mating, and may communicate breeding condition. The wide range of marking behaviours, compounded by the lack of any clearly sex-limited behaviour at latrines, suggests a multiplicity of roles in the social lives of all age and sex classes of badgers. Copyright 2002 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour     

Self-Discrimination in Meadow Voles, Microtus pennsylvanicus

Particular features of the signaling characteristics of the scent marks of temperate zone, seasonally breeding mammals may reflect differences in their reproductive state and, hence, be variable. Consequently, an individual's perception of self may depend more on the condition independent than on the condition-dependent signaling characteristics of the scent marks. Yet, we do not know whether an individual responds to changes in the signaling characteristics of its own scent marks, such as those associated with changes in an individual's reproductive state. Such changes may affect how and where an animal scent marks. Here we report on a series of experiments designed to test the hypothesis that individual meadow voles, Microtus pennsylvanicus , distinguish between scent marks they deposited when they were in different reproductive states. Results showed that voles discriminated their own scent marks from those of unfamiliar, same-sex conspecifics, and the scent marks of siblings. Voles did not behave as if they could distinguish between their own scent marks if the marks were deposited when the voles were in the same reproductive state, although the two scent marks used as stimuli differed in age by 30 d. However, they did so distinguish if they were exposed to scent marks taken when they were in different reproductive states. Overall, these findings suggest that voles behave as if their novel and familiar scent marks shared the similar signaling features. If, however, the reproductive condition of the voles differed when it provided the two scent marks, they behaved as if their own scent marks had different signal characteristics, which may have induced voles to treat the two scent marks as not being the same or having been deposited by two different donors. We speculate that the scent marks of individuals may have unique signaling characteristics that may be associated with that individual's 'current template for self'.     

Over-marking and Adjacent Marking are Influenced by Sibship in Male Prairie Voles,Microtus ochrogaster

Scent over-marking occurs when an animal deposits its scent mark on top of the scent mark of a conspecific. Over-marking may provide advantages in the transfer of information to the individual whose scent is on top but not to the individual whose scent is on the bottom. We tested the hypothesis that over-marking is a competitive form of olfactory communication and that male prairie voles would over-mark the scent marks of same-sex conspecifics more than those of same-sex siblings. Two age-matched male voles (first male and second male) were placed successively into an arena in which they were allowed to explore freely and scent mark for 15 min at age 12, 20, 28, 36, 44, and 52 d. The first male was placed into a clean arena, whereas the second male was placed into an arena containing either the scent marks of an age-matched male sibling or nonsibling. Age affected the total number of scent marks deposited by the voles; 12-20-d-old voles deposited fewer scent marks, over-marks and adjacent marks than did 28-52-d-old voles. Sibship did not affect the total number of scent marks deposited by the first and second voles but did affect the number of over-marks and adjacent marks deposited by the second vole. Siblings received significantly fewer over-marks and adjacent marks than did nonsiblings; this effect was most dramatic after the voles reached 28 d of age, a time coincident with the onset of puberty. Males separated from siblings and housed singly at 44-d-old and tested at 52-d-old, deposited significantly more over-marks and adjacent marks in arenas if the first vole was a nonsibling than if it was a sibling. This differential scent-marking supports the hypothesis that over-marking and adjacent marking are used as competitive forms of olfactory communication by male prairie voles.     

Female marmoset monkeys (Callithrix jacchus) can be identified from the chemical composition of their scent marks.

The present study analyzed 42 organic solvent extracts of scent mark pools from five dominant female common marmosets by gas chromatography (GC) and combined GC and mass spectrometry. We determined whether there were qualitative or quantitative differences between the chemical composition of scent marks from individual females. Gas chromatography and mass spectral analysis detected the same 162 chemicals in 86% (36/42) of scent mark pools from five dominant females. This near identical chemical composition of scent marks suggested there were few, if any, qualitative differences between the chemical composition of scent marks from individual females. Instead, quantitative differences in scent may provide the key factor distinguishing individual females. Using the relative concentration of highly volatile chemicals detected by GC in scent marks, linear discriminant analysis classified scent mark pools to their correct donor approximately 91% of the time. Such highly reliable statistical matching of scent to donor suggested that each individual female common marmoset has a unique ratio of highly volatile chemicals in their scent marks which may permit individual identification of females from odors in their scent alone.     

Scent Marking in Voles: A Reassessment of Over Marking, Counter Marking, and Self-Advertisement

We conducted a series of experiments to discern among the counter-marking, over-marking, and self-advertisement hypotheses for secondary marking in male prairie voles, Microtus ochrogaster , and meadow voles, M. pennsylvanicus . Secondary scent marks (those placed in an area that has already been marked by a conspecific) were not significantly greater than initial marks placed on clean substrate (a substrate without any previous scent marks) for either species and thus did not support a counter-marking hypothesis. Similarly, overlapping of initial scent marks with secondary marks occurred less often than expected by chance and did not support an over-marking hypothesis. Secondary marks tended to avoid overlap with scent marks previously deposited by a potential competitor. Our results suggest that secondary scent marking functions to self-advertise by maximizing individual identity and avoiding masking or blending with previous donors. Future studies on secondary marking should be designed to quantify the observed and expected frequency and placement of original and secondary marks to discern among alternative hypotheses for the adaptive significance of secondary marking.     

UV reflecting vole scent marks attract a passerine, the great grey shrike Lanius excubitor

Diurnal raptors have been shown to use ultraviolet vision and UV-reflecting vole scent marks to find suitable hunting areas. We studied if a passerine species, the great grey shrike Lanius excubitor that uses voles as its primary food, may also detect prey-patches in the same way. We conducted a laboratory experiment with ten shrikes. Each individual shrike had four options to choose from: (1) scent marks with UV light, (2) scent marks without UV light, (3) clean arena with UV light, and (4) clean arena without UV light. The birds preferred the scent-marked arena with UV light as measured by the number of scans and the time spent above it. Therefore, we suggest that great grey shrike probably uses UV cues to gain information on vole locations and abundance.     

Male and Female Meadow Voles,Microtus pennsylvanicus,Differ in Their Responses to Heterospecific/Conspecific Over‐Marks

Voles use runways, paths, and trails that may also be used by rabbits and mink. These shared areas could contain the scent marks of conspecifics and heterospecifics. Thus, it is likely that the scent marks of heterospecifics may overlap or be overlapped by those of voles, forming over‐marks. Much is known about how voles respond to over‐marks of two different conspecifics. However, we do not know how they would respond to an opposite‐sex conspecific whose scent marks are in an over‐mark with the scent marks of predator or the scent marks of a non‐predator heterospecifics. We tested the hypothesis that meadow voles, Microtus pennsylvanicus, differ in their response to the scent mark of the opposite‐sex conspecific if the scent mark was overlapped by that of a mink, a vole predator, or rabbit, a vole non‐predator. We found that female but not male voles showed a preference for the scent marks of the opposite‐sex conspecifics that were part of the mink‐vole over‐mark when compared to those of opposite‐sex conspecifics that were not part of the over‐mark. This preference by female voles was independent of whether the male vole was the top‐scent donor or bottom‐scent donor of the over‐mark. Male and female voles showed no preference between the scent marks of the opposite‐sex conspecifics whose marks were part of or not part of the rabbit‐vole over‐mark. Sex differences in the manner that meadow voles respond to rabbit‐vole and mink‐vole over‐marks are discussed.     

Meadow Voles (Microtus pennsylvanicus, Arvicolidae) Over-mark and Adjacent-mark the Scent Marks of Same-sex Conspecifics

Scent over-marking occurs when an animal deposits its scent mark on top of the scent mark of a conspecific; adjacent-marking occurs when an animal deposits its scent mark next to the scent mark of a conspecific. Given that male rodents usually scent mark more than females and that animals spend more time investigating the odor of the top-scent donor of an over-mark, I tested the following three hypotheses. First, male meadow voles deposit more scent marks than female meadow voles. Second, male meadow voles will deposit more over-marks and adjacent-marks in response to the scent marks of a same-sex conspecific than females would. Third, meadow voles spend more time investigating the odor of the second vole placed in the arena than that of the first vole placed in the arena. To test these hypotheses, two age-matched, like-sex conspecifics (first vole and second vole) were placed successively into an arena in which they were allowed to freely explore and scent mark for 15 min. The first hypothesis was not supported. The first and second vole, independently of sex, deposited a similar number of scent marks. The second hypothesis was also not supported by the data: more conspecific scent marks were over-marked by the second female than by the second male. The third hypothesis was supported by the data. After investigating a scented arena, males and females spent more time investigating the odor of the second vole than that of the first vole. Sex differences in scent-marking behaviors of meadow voles are unlike those reported for other species of rodents.     

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.     

Spatial patterns of plant richness across treeline ecotones in the Pyrenees reveal different locations for richness and tree cover boundaries

Aim  To forecast the responses of alpine flora to the expected upward shift of treeline ecotones due to climatic warming, we investigated species richness patterns of vascular plants at small spatial scales across elevational transects.
Location  Richness patterns were assessed at local scales along the elevational gradient in two undisturbed treeline ecotones and one disturbed treeline ecotone in the Spanish Pyrenees.
Methods  We placed a rectangular plot (0.3–0.4 ha) in each treeline ecotone. We estimated and described the spatial patterns of plant richness using the point method and Moran's I correlograms. We delineated boundaries based on plant richness and tree cover using moving split windows and wavelet analysis. Then, to determine if floristic and tree cover boundaries were spatially related, overlap statistics were used.
Results  Plant richness increased above the forest limit and was negatively related to tree cover in the undisturbed sites. The mean size of richness patches in one of these sites was 10–15 m. Moving split windows and wavelets detected the sharpest changes in plant richness above the forest limit at both undisturbed sites. Most tree cover and plant richness boundaries were not spatially related.
Main conclusions  The upslope decrease of tree cover may explain the increase of plant richness across alpine treeline ecotones. However, the detection of abrupt richness boundaries well above the forest limit indicates the importance of local environmental heterogeneity to explain the patterns of plant richness at smaller scales. We found highly diverse microsites dominated by alpine species above the forest limit, which should be monitored to describe their response to the predicted upward shift of forests.     

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.     

Scent-marking displays provide honest signals of health and infection

Males of many species produce scent marks and other olfactorysignals that function to intimidate rivals and attract females.It has been suggested that scent marks provide an honest, cheat-proofdisplay of an individual's health and condition. Here we reportseveral findings that address this hypothesis in wild-derivedhouse mice (Mus musculus domesticus). (1) We exposed males tofemale odor, which induces an increase in testosterone, andfound that sexual stimulation significantly increased the males'scent-marking and the attractiveness of their scent marks tofemales. (2) We challenged sexually stimulated males with anonreplicating strain of bacteria (Salmonella enterica C5TS)to activate immunity and found that this significantly decreasedthe males' scent-marking and the attractiveness of their scentmarks to females. (3) We collected scent marks from infectedand sham-infected males when they were sexually stimulated ornot, and we found that females could significantly discriminatethe scent marks of infected versus control males, but only whenthe males were sexually stimulated. Taken together, our resultsindicate that male mice modulate their scent-marking displaydepending on their health and perceived mating opportunities.Increased scent marking enhances males' attractiveness to females,scent marks provide an honest indicator of bacterial infection(and perhaps immune activation), and females are able to assessthe health of males more easily when males mark at a high rate.     

Meadow Voles (Microtus pennsylvanicus) and Prairie Voles (M. ochrogaster) Differ in Their Responses to Over-Marks from Opposite- and Same-Sex Conspecifics

Over‐marking occurs when one individual deposits its scent mark on the scent mark of a conspecific. Previous studies have shown that meadow voles (Microtus pennsylvanicus) and prairie voles (M. ochrogaster) that were exposed to an over‐mark of two same‐sex conspecifics, later responded similarly to the top‐scent mark but differed in their response to the bottom‐scent mark. In the present study, we examined the responses of meadow voles and prairie voles to same‐sex and mixed‐sex over‐marks to ascertain whether their responses reflect the different tactics which males and females in promiscuous (meadow voles) and monogamous (prairie voles) species use to attract opposite‐sex conspecifics and to compete with same‐sex conspecifics. Males and females of both species spent more time investigating the mark of the top‐scent donor than that of the bottom‐scent donor of an over‐mark. Meadow voles exposed to a mixed‐sex over‐mark spent more time investigating the mark of the opposite‐sex conspecific independently of whether it was from the top‐ or bottom‐scent donor. In contrast, prairie voles spent more time investigating the mark of the opposite‐sex donor if it was from the top‐scent donor. These results suggest that: (i) over‐marking serves a competitive function; (ii) the scent marks of individuals attract multiple mates in promiscuous species such as the meadow vole; and (iii) the scent marks of individuals establish and maintain pair bonds between familiar opposite‐sex conspecifics in monogamous species such as the prairie vole.     

The ownership signature in mouse scent marks is involatile

Male house mice advertise their territory ownership through urinary scent marks and use individual-specific patterns of major urinary proteins (MUPs) to discriminate between their own scent and that of other males. It is not clear whether recognition occurs through discrimination of the non-volatile proteins or protein-ligand complexes (direct model), or by the detection of volatile ligands that are released from MUPs (indirect model). To examine the mechanism underlying individual scent mark signatures, we compared investigatory and countermarking responses of male laboratory mice presented with male scent marks from a strain with a different MUP pattern, when they could contact the scent or when contact was prevented by a porous nitrocellulose sheet to which proteins bind. Mice investigated scent marks from other males whether these were covered or not, and biochemical analysis confirmed that the porous cover did not prevent the release of volatiles from scent marks. Having gained information through investigation, mice increased their own scent marking only if they had direct contact with another male's urine, failing to do this when contact was prevented. Individual signatures in scent marks thus appear to be carried by non-volatile proteins or by non-volatile protein-ligand complexes, rather than by volatiles emanating from the scent.     

The predation risks of interspecific eavesdropping: weasel–vole interactions

Competing species benefit from eavesdropping on each other's signals by learning about shared resources or predators. But conspicuous signals are also open to exploitation by eavesdropping predators and should also pose a threat to other sympatric prey species. In western Finland, sibling voles Microtus rossiameridionalis and field voles M. agrestis compete for food and space, and both species rely upon scent marks for intraspecific communication. Both vole species are prey to a range of terrestrial scent hunting predators such as least weasels, however, the competitively superior sibling voles are taken preferentially. We tested in large out‐door enclosures whether field voles eavesdrop on the signals of its competitor, and whether they behave as though this eavesdropping carries a risk of predation. We presented field voles with scent marks from unknown conspecifics and sibling voles and measured their visitation, activity and scent marking behaviours at these scents under high (weasel present) and low (weasel absent) predation risk. Field voles readily visited both field and sibling vole scents under both high and low predation risk; however their activity at sibling vole scent marks declined significantly under increased predation risk. In contrast, predation risk did not affect field voles’ activity at conspecific scents. Thus, field voles were compelled to maintain eavesdropping on heterospecific scents under an increased risk of predation, however they compensated for this additional risk by reducing their activity at these risky scents. Scent marking rates declined significantly under high predation risk. Our results therefore reveal a hidden complexity in the use of social signals within multi‐species assemblages that is clearly sensitive to the potential for increased predation risk. The predation risks of interspecific eavesdropping demonstrated here represents a significant generalisation of the concept of associational susceptibility.     

Increased temperature disrupts chemical communication in some species but not others: The importance of local adaptation and distribution

Environmental conditions experienced by a species during its evolutionary history may shape the signals it uses for communication. Consequently, rapid environmental changes may lead to less effective signals, which interfere with communication between individuals, altering life history traits such as predator detection and mate searching. Increased temperature can reduce the efficacy of scent marks released by male lizards, but the extent to which this negative effect is related to specific biological traits and evolutionary histories across species and populations have not been explored. We experimentally tested how increased temperature affects the efficacy of chemical signals of high‐ and low‐altitude populations of three lizard species that differ in their ecological requirements and altitudinal distributions. We tested the behavioral chemosensory responses of males from each species and population to male scent marks that had been incubated at one of two temperatures (cold 16°C or hot 20°C). In high‐altitude populations of a mountain species (Iberolacerta monticola), the efficacy of chemical signals (i.e., latency time and number of tongue flicks) was lower after scent marks had been exposed to a hot temperature. The temperature that scent marks were incubated at did not affect the efficacy of chemical signals in a ubiquitous species (Podarcis muralis) or another mountain species (I. bonalli). Our results suggest that specific ecological traits arising through local adaptation to restricted distributions may be important in determining species vulnerability to climatic change.     

Meadow voles and prairie voles differ in the percentage of conspecific marks they over-mark

Many terrestrial mammals scent mark in areas containing the scent marks of conspecifics, and thus, may deposit their own scent marks on top of those that were deposited previously by conspecifics. This phenomenon, known as over-marking appears to play a role in same-sex competition or mate attraction. The present study determines whether meadow and prairie voles avoid over-marking the scent marks of conspecifics, target the scent marks of conspecifics and over-mark them, or randomly over-mark the scent marks of conspecifics. The data show that meadow and prairie voles adjust the number and location of scent marks that they deposit in areas marked previously by particular conspecifics. Male and female meadow and prairie voles target the scent marks of opposite-sex conspecifics and over-mark them. Female meadow and prairie voles also target the scent marks of female conspecifics. In contrast, male meadow and prairie voles over-mark the scent marks of male conspecifics in a random manner. By differentially over-marking the scent marks of conspecifics, voles may be able to communicate particular information to a variety of conspecifics.     

Pygmy owl Glaucidium passerinum and the usage of ultraviolet cues of prey

Birds rely mainly on their vision when foraging. Many diurnal raptors use ultraviolet (UV) vision and ultraviolet‐reflecting vole scent marks to find suitable hunting areas, whereas nocturnal owls seem to lack this ability. We studied if the diurnal pygmy owl Glaucidium passerinum that uses voles and birds as its food can detect vole scent marks using UV‐vision. We conducted a laboratory experiment with eleven owls. Each individual owl had four options to choose from: (1) scent marks with UV light, (2) scent marks without UV light, (3) clean arena with UV light and (4) clean arena without UV light. The owls scanned the scent mark arena more often in the presence of UV light than other arenas. However, owls did not spend more time above the UV arena. We suggest that pygmy owls can detect near UV and use UV to gain information about prey like other diurnal raptors.     

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.