Interactions between Males of the Lizard Liolaemus tenuis: Roles of Familiarity and Memory

For territorial organisms, recognition of familiar individuals can reduce the frequency and intensity of aggressive encounters (‘dear enemy’ phenomenon), stabilize social systems, and reduce the cost of territory maintenance. Here, we investigated the behavioural events displayed during contests between familiar and unfamiliar individuals in the lizard Liolaemus tenuis (Liolaemidae), a species in which males are territorial. The behaviours recorded were attack, warning, evasion, and submission, and the latencies to the first aggressive (attack or warning) behaviour. Additionally, we assessed the ability of individuals to remember a familiar conspecific after a period without social interaction. Individual males reduced and delayed aggressive behaviour directed towards socially familiar individuals compared with unfamiliar ones. These results suggest that males distinguished between familiar and unfamiliar conspecific males and are in agreement with the ‘dear enemy’ phenomenon. Other behaviours were similar in the contests between familiar and unfamiliar individuals. Recognition of familiar conspecifics was lost after 20 d without social interactions. This may be relevant for interactions with floater males or with neighbours that lose their territory and subsequently attempt to fight for their ex‐neighbour's territory.     

Dispersal behaviour of individuals in metapopulations of two British butterflies

Dispersal patterns are important in metapopulation ecology because they affect the dynamics and survival of populations. However, because little empirical information exists on dispersal behaviour of individuals, theoretical models usually assume random dispersal. Recent empirical evidence, by contrast, suggests that the butterfly Maniola jurtina uses a non‐random, systematic dispersal strategy, can detect and orient towards habitat from distances of 100–150 m, and prefers a familiar habitat patch over a non‐familiar one (‘homing behaviour’). The present study (1) investigated whether these results generalise to another butterfly species, Pyronia tithonus; and (2) examined the cause of the observed ‘homing behaviour’ in M. jurtina. P. tithonus used a similar non‐random, systematic dispersal strategy to M. jurtina, had a similar perceptual range for habitat detection and preferred a familiar habitat patch over a non‐familiar one. The ‘homing behaviour’ of M. jurtina was found to be context‐dependent: individual M. jurtina translocated within habitat did not return towards their capture point, whereas individuals translocated similar distances out of habitat did return to their ‘home’ patch. We conclude that butterfly ‘homing behaviour’ is not based on an inherent preference for a familiar location, but that familiarity with an area facilitates the recognition of suitable habitat, towards which individuals orient if they find themselves in unsuitable habitat. Contrary to conventional wisdom, we suggest that frequent, short ‘excursions’ over habitat patch boundaries are evolutionarily advantageous to individuals, because increased familiarity with the surrounding environment is likely to increase the ability of a straying animal to return to its natural habitat, and to reduce the rate of mortality experienced by individuals attempting to disperse between habitat patches. We discuss the implications of the non‐random dispersal for existing metapopulation models, including models of the evolution of dispersal rates.     

Individual Recognition Affects Aggression and Dominance Relations in Rainbow Trout,Oncorhynchus mykiss

In this study, the hypothesis that individual recognition is used as a cue to reduce the cost of contesting resources in rainbow trout Oncorhynchus mykiss, was addressed. The predictions were that the second contest between familiar individuals should be settled with less aggression, and lower probability of status reversal, than a contest between strangers. To test these predictions, similar-sized juvenile rainbow trout were subjected to two dyadic dominance contests in one of four treatment groups: in half of the pairs, the initially subordinate and dominant individuals were staged against an unfamiliar opponent (of opposite rank to their own) in a second contest, while in the other the initial pair was reunited for the second contest. Further, in half of the pairs, contestants were separated for 3 d between contests, while in the other the second contest was staged immediately after the first. Levels of aggression in contests between familiar individuals were lower than in contests between strangers, which supports the hypothesis that individual recognition reduces aggression. Dominance status was reversed in 31% of the 62 tested pairs. Although the probability of status reversal was not significantly affected by individual recognition, the degree of change in competitive success appeared to be lower in familiar pairs. Separation interacted with familiarity so that the effect of individual recognition generally was less pronounced when pairs were separated between contests, suggesting that the ability to remember opponents is time/limited. In natural streams, salmonids may use individual recognition to reduce the cost of contesting resources within groups, to reduce aggression between territory neighbours and to distinguish ‘cheaters’ from honest signallers.     

Neural mechanisms of auditory species recognition in birds

Auditory communication in humans and other animals frequently takes place in noisy environments with many co‐occurring signallers. Receivers are thus challenged to rapidly recognize salient auditory signals and filter out irrelevant sounds. Most bird species produce a variety of complex vocalizations that function to communicate with other members of their own species and behavioural evidence broadly supports preferences for conspecific over heterospecific sounds (auditory species recognition). However, it remains unclear whether such auditory signals are categorically recognized by the sensory and central nervous system. Here, we review 53 published studies that compare avian neural responses between conspecific versus heterospecific vocalizations. Irrespective of the techniques used to characterize neural activity, distinct nuclei of the auditory forebrain are consistently shown to be repeatedly conspecific selective across taxa, even in response to unfamiliar individuals with distinct acoustic properties. Yet, species‐specific neural discrimination is not a stereotyped auditory response, but is modulated according to its salience depending, for example, on ontogenetic exposure to conspecific versus heterospecific stimuli. Neuromodulators, in particular norepinephrine, may mediate species recognition by regulating the accuracy of neuronal coding for salient conspecific stimuli. Our review lends strong support for neural structures that categorically recognize conspecific signals despite the highly variable physical properties of the stimulus. The available data are in support of a ‘perceptual filter’‐based mechanism to determine the saliency of the signal, in that species identity and social experience combine to influence the neural processing of species‐specific auditory stimuli. Finally, we present hypotheses and their testable predictions, to propose next steps in species‐recognition research into the emerging model of the neural conceptual construct in avian auditory recognition.     

Kin discrimination in sticklebacks is mediated by social learning rather than innate recognition

Theory predicts several advantages for animals to recognize kin. These include inbreeding avoidance and an increase in inclusive fitness. In shoaling species, kin recognition may lead to an increased amount of altruism among shoal members. Adult, non‐reproductive three‐spined sticklebacks, Gasterosteus aculeatus, prefer to shoal with kin. This preference was shown for familiar as well as for unfamiliar individuals. However, whether it is based on learned cues of familiar individuals or on innate mechanisms like self‐referent phenotype matching or ‘true’ kin recognition through recognition alleles remains unknown. In our experiments, juvenile fish were given the choice between shoals that differed in relatedness and familiarity. The number of testfish who joined each group indicated that sticklebacks prefer to shoal with familiar kin when the alternative shoal was composed of unfamiliar non‐kin. When one shoal consisted of familiar kin while the second consisted of familiar non‐kin testfish did not show any preference. Kin recognition in sticklebacks is thus most likely mediated by social learning.     

Social context predicts recognition systems in ant queens

Recognition of group‐members is a key feature of sociality. Ants use chemical communication to discriminate nestmates from intruders, enhancing kin cooperation and preventing parasitism. The recognition code is embedded in their cuticular chemical profile, which typically varies between colonies. We predicted that ants might be capable of accurate recognition in unusual situations when few individuals interact repeatedly, as new colonies started by two to three queens. Individual recognition would be favoured by selection when queens establish dominance hierarchies, because repeated fights for dominance are costly; but it would not evolve in absence of hierarchies. We previously showed that Pachycondyla co‐founding queens, which form dominance hierarchies, have accurate individual recognition based on chemical cues. Here, we used the ant Lasius niger to test the null hypothesis that individual recognition does not occur when co‐founding queens do not establish dominance hierarchies. Indeed, L. niger queens show a similar level of aggression towards both co‐foundresses and intruders, indicating that they are unable of individual recognition, contrary to Pachycondyla. Additionally, the variation in chemical profiles of Lasius and Pachycondyla queens is comparable, thus informational constraints are unlikely to apply. We conclude that selection pressure from the social context is of crucial significance for the sophistication of recognition systems.     

Dominance and effects of strange conspecifics on aggressive interactions in the hermit crab Pagurus longicarpus (say)

Dominance orders in the hermit crab Pagurus longicarpus were observed in the laboratory. Groups of four crabs formed loose dominance hierarchies as determined by repeated display and retreat behaviour. Stronger dominance orders were inversely correlated with the frequency of aggressive interactions. Recognition of individuals, as measured by frequency and intensity of aggressive encounters between familiar crabs and introduced strangers, was not important in maintaining dominance orders. Rather, P. longicarpus recognized the aggressive state of conspecifics, as shown by frequencies of aggressive encounters after individuals of different dominance rankings were exchanged between established hierarchies.     

Individual Variation in Behavioural Reactions to Unfamiliar Conspecific Vocalisation and Hormonal Underpinnings in Male Chimpanzees

It has been established that various species exhibit personality, defined as intra‐individual consistency and inter‐individual variation in behavioural phenotypes. For example, certain individuals may demonstrate consistently greater behavioural reactions and elevated stress responses. We conducted playback experiments and hormonal analyses on male chimpanzees (Pan troglodytes) in captivity to investigate the patterns and proximate mediators of individual variations in behavioural reactions. We found intra‐individual consistency and inter‐individual variation in behavioural reactions (intensive vigilance towards the direction of speakers) to vocalisations by unfamiliar chimpanzees. This behavioural reaction was positively correlated with changes in salivary cortisol concentration, suggesting that stress is a proximate factor mediating the variation in behavioural reactions. The males who were highly responsive to the conspecific vocalisation also exhibited high behavioural reactions towards the neutral broadcast stimulus (the jungle crow’s Corvus macrorhynchos ‘ka’ vocalisation). This observation is consistent with the notion that male chimpanzees vary in intrinsic behavioural tendency to different stimuli.     

Olfactory Experience Affects the Response of Meadow Voles to the Opposite‐Sex Scent Donor of Mixed‐Sex Over‐Marks

Scent marking and over‐marking are important forms of communication between the sexes for many terrestrial mammals. Over the course of three experiments, we determined whether the amount of time individuals investigate the scent marks of opposite‐sex conspecifics is affected by 4 d of olfactory experience with those conspecifics. In Experiment 1, female meadow voles, Microtus pennsylvanicus, spent more time investigating the scent mark of the novel male conspecific than that of the familiar male donor, whereas male voles spent similar amounts of time investigating the scent mark of the familiar female and a novel female conspecific. In Experiment 2, voles were exposed to a mixed‐sex over‐mark in which subjects did not have 4 d of olfactory experience with either the top‐scent donor or the bottom‐scent donor. During the test phase, male and female voles spent more time investigating the scent mark of the opposite‐sex conspecific that provided the top‐scent mark than that of a novel, opposite‐sex conspecific. Male and female voles spent similar amounts of time investigating the scent mark of the bottom‐scent donor and that of a novel opposite‐sex conspecific. In Experiment 3, voles were exposed to a mixed‐sex over‐mark that contained the scent mark of an opposite‐sex conspecific with which they had 4 d of olfactory experience. During the test phase, male voles spent more time investigating the mark of the familiar, top‐scent female than the scent mark of a novel female donor but spent similar amounts of time investigating the mark of the familiar, bottom‐scent female and that of a novel female donor. In contrast, female voles spent more time investigating the mark of a novel male donor than that of either the familiar, top‐scent male or that of the familiar, bottom‐scent male. The sex differences in the responses of voles to scent marks and mixed‐sex over‐marks are discussed in relation to the natural history and non‐monogamous mating system of meadow voles.     

Piping as a display of dominance by wintering Oystercatchers Haematopus ostralegus

Although Oystercatchers Haematopus ostralegus wintering in the Exe Estuary performed the piping display in any type of aggressive encounter, it was predominantly observed in two contexts. ‘Solitary piping’ occurred when one individual piped without an obvious opponent being in the immediate vicinity. In ‘piping ceremonies’, two or more individuals piped at each other for prolonged periods at close distance. Prolonged contests over mussels were usually won by the individual that had initially started piping. The most aggressive and successful birds (the dominants), engaged most often in solitary piping and piping ceremonies, using up to 10% of their time this way. This suggests that the behaviour was associated with dominance rank. The hypothesis is that the two birds are likely to start piping if their relative status has not already been established, so that a quick end to a dispute over a mussel or feeding site is not achieved. A dominant individual performs solitary piping from a distance to suppress the aggressive activities of other birds within its feeding range. If this signal fails, the dominant may join the ceremony, explaining why three was the most frequent number of birds involved in piping ceremonies. The ‘butterfly’ flight, used mainly by apparently dominant birds as they arrived on the feeding grounds, may signal their high status to birds already there. The outcome of several piping ceremonies involving birds of known dominance was consistent with this explanation. The location of piping ceremonies involving only two birds (interpreted as piping ceremonies not joined by dominants) at the extremities of the feeding ranges of the most dominant individuals is also consistent with this hypothesis, because this is where their dominance would be expected to decline and would therefore be more likely to be contested. This explanation of piping and butterfly displays assumes that individuals can recognize other individuals or quickly assess their dominance. Since dominant individuals were attacked less often than subdominants and attacking birds were rebuffed less than would be expected if recognition did not occur, we suggest that some form of dominance or individual recognition did exist. The width of the white collar did not correlate with dominance, but the individual variations in this feature may enable birds to distinguish each other and thus learn their relative status. It is intriguing that the diplomatist posture, which is typically used to rebuff misguided attackers, seems almost designed to give the opponent a particularly clear view of the white collar.     

Scent of death: Evolution from sea to land of an extreme collective attraction to conspecific death

All living organisms must eventually die, though in some cases their death can bring life‐giving opportunities. Few studies, however, have experimentally tested how animals capitalize on conspecific death and why this specialization would evolve. Here, we conducted experiments on the phylogenetically most closely‐related marine and terrestrial hermit crabs to investigate the evolution of responses to death during the sea‐to‐land transition. In the sea, death of both conspecifics and heterospecifics generates unremodeled shells needed by marine hermit crabs. In contrast, on land, terrestrial hermit crabs are specialized to live in architecturally remodeled shells, and the sole opportunity to acquire these essential resources is conspecific death. We experimentally tested these different species’ responsiveness to the scent of conspecific versus heterospecific death, predicting that conspecific death would have special attractive value for the terrestrial species. We found the terrestrial species was overwhelmingly attracted to conspecific death, rapidly approaching and forming social groupings around conspecific death sites that dwarfed those around heterospecific death sites. This differential responsiveness to conspecific versus heterospecific death was absent in marine species. Our results thus reveal that on land a reliance on resources associated exclusively with conspecifics has favored the evolution of an extreme collective attraction to conspecific death.     

Retention of social recognition after hibernation in Belding's ground squirrels

The retention of social memory during long periods of separation, such as hibernation or migration, has not been well documented, despite evidence for long-term social relationships in migrating species or in long-lived sedentary species. We investigated the ability of captive Belding's ground squirrels, Spermophilus beldingi, to remember previously familiar individuals as well as littermates after 9 months of isolation. Before hibernation, young ground squirrels discriminated between odours of familiar and unfamiliar individuals, as shown by greater investigation of a novel individual's odour. The following spring, these yearlings did not respond differentially to odours of previously familiar and unfamiliar individuals, suggesting that memory for familiar conspecifics was lost during hibernation. In contrast, both female and male yearlings continued to discriminate between odours of littermates and previously familiar nonlittermates. Thus, recognition of close kin was maintained during prolonged social isolation, but recognition of familiar, unrelated individuals was not. If re-establishment of familiarity is not costly or if adults rarely interact with the same individuals in successive years, then selection may not favour retention of individual memories of particular conspecifics over the winter. Even though males rarely encounter kin after dispersal, yearling males did recognize their siblings, suggesting that the relative costs of maintaining kin-recognition abilities year-round may be low. Possible mechanisms underlying the formation and maintenance of individual and kin recognition are discussed. Copyright 2000 The Association for the Study of Animal Behaviour.     

Individuality in Problem Solving: String Pulling in Two Carduelis Species (Aves: Passeriformes)

The research reported here was designed to study the individual peculiarities of birds in solving a problem. Goldfinches Carduelis carduelis and siskins C. spinus were tested with the string‐pulling task: sitting on a perch from which a small food container is suspended by a string the test bird had to lift the container, using the bill to pull the string stepwise up and a foot to hold it, and repeat that until they could reach the food. Fifty‐two goldfinches and 29 siskins raised under controlled conditions were tested individually. Three groups became apparent: ‘inventors’ (23% of goldfinches; 62% of siskins) solved the problem by themselves; ‘imitators’ (25% of goldfinches; 10% of siskins) succeeded after seeing a performing conspecific; ‘duffers’ (52% of goldfinches, 28% of siskins) did not succeed either way. The species – but not the sexes – differed significantly in string‐pulling ability. The results of our experiments indicate that string pulling is an acquired combination of innate behaviour elements. An individual's string‐pulling competence may depend on prior experience of handling branchlets, on trial‐and‐error learning and on social learning (emulation). However, some individuals succeeded without these facilitating factors, while others did not succeed at all despite all of them present. Although functionally and motivationally related to feeding, the learned string pulling is often shown as a playful activity without an obvious reward.     

Investigating the Effect of Familiarity on Kin Recognition of Three‐Spined Stickleback (Gasterosteus aculeatus)

The ability to discriminate between related and unrelated individuals has been demonstrated in many species. The mechanisms behind this ability might be manifold and depend on the ecological context in which the species lives. In brood‐caring species, both familiarity and phenotype matching are known to be used in kin recognition. However, results of studies disentangling these two phenomena have proved contradictory. We aimed to broaden our knowledge about the mechanisms of kin recognition using shoaling preferences of three‐spined stickleback (Gasterosteus aculeatus) as a model behavior. In our first experiment, focal fish had the choice to shoal either with kin or unfamiliar non‐kin. In half of the trials, kin groups were composed of familiar individuals, while they were unfamiliar in the other half. Focal fish significantly preferred kin as shoaling partner, a result which was not reinforced by familiarity. In our second experiment, focal fish were given the choice between a shoal of familiar kin and a shoal of unfamiliar kin. Here, focal fish did not show any significant preference. These results indicate that familiarity does not impact stickleback's ability to recognize kin. Furthermore, they show that familiarity does not overrule recognition based on phenotype matching or innate recognition, underlining the importance of these mechanisms. Finally, our results lead to the assumption that individual recognition might play a minor role also in non‐kin‐based preferences for familiars.     

Long-term memory of individual identity in ant queens

Remembering individual identities is part of our own everyday social life. Surprisingly, this ability has recently been shown in two social insects. While paper wasps recognize each other individually through their facial markings, the ant, Pachycondyla villosa, uses chemical cues. In both species, individual recognition is adaptive since it facilitates the maintenance of stable dominance hierarchies among individuals, and thus reduces the cost of conflict within these small societies. Here, we investigated individual recognition in Pachycondyla ants by quantifying the level of aggression between pairs of familiar or unfamiliar queens over time. We show that unrelated founding queens of P. villosa and Pachycondyla inversa store information on the individual identity of other queens and can retrieve it from memory after 24h of separation. Thus, we have documented for the first time that long-term memory of individual identity is present and functional in ants. This novel finding represents an advance in our understanding of the mechanism determining the evolution of cooperation among unrelated individuals.     

Mycorrhizal feedback is not associated with the outcome of competition in old‐field perennial plants

The symbiosis between plants and arbuscular mycorrhizal (AM) fungi is hypothesized to be an important contributor to plant–soil feedbacks, which can influence the outcome of inter‐specific competition. Mycorrhizal feedbacks can be conspecific, which affects individuals of the same species, or heterospecific, which affects individuals of a different species. When heterospecific feedbacks are more positive than conspecific feedbacks, heterospecific individuals are expected to outcompete conspecific individuals. To test this hypothesis, we quantified conspecific mycorrhizal feedback for Plantago lanceolata as a focal species, and heterospecific mycorrhizal feedbacks for 21 competitor old‐field species using mycorrhizae cultured with P. lanceolata. We quantified inter‐specific competition against the focal species by growing the 21 old‐field species with and without P. lanceolata in the presence of mycorrhizae cultured with P. lanceolata. Heterospecific and conspecific feedbacks were both positive, and average heterospecific feedbacks exceeded conspecific feedback by 75%. Competition suppressed P. lanceolata biomass by 14% and average competitor biomass was reduced by 44% in the presence of P. lanceolata, and these effects varied with competitor species identity. Contrary to predictions, the magnitude of heterospecific feedbacks did not predict the ability of competitor species to either suppress or resist suppression by P. lanceolata. Instead, the outcome of competition was significantly and positively correlated with intrinsic growth rate, measured as biomass of competitor species five weeks after germination in non‐inoculated conditions. Our findings suggest that species experiencing more positive mycorrhizal feedbacks than a competitor do not necessarily have a competitive advantage. Mycorrhizal mediated soil feedbacks may be less important than intrinsic differences in growth rate in determining competitive outcomes.     

Mud crabs (Xanthidae) in Chesapeake Bay: claw characteristics and predation on epifaunal bivalves

Abstract. We examined claw characteristics of mud crabs (Eurypanopeus depressus, Rhithropanopeus harrisii) to determine if one crab species was potentially more powerful than the other. We related our findings to the abilities of individuals of each species to open epifaunal mytiliform bivalves (Ischadium recurvum; Mytilopsis leucophaeata) that occur on beds of eastern oysters (Crassostrea virginica) in mesohaline Chesapeake Bay. There were high correlations between claw width or height and claw length, and between claw length and carapace width for both mud crab species. The mechanical advantage or “grip strength’ of the crusher and cutter claws of both species did not change with crab size (carapace width) and did not differ between sexes in each species, nor did the cutter data differ between species. However, individuals of E. depressus had a significantly stronger crusher claw grip than did those of R. harrisii. Data on mechanical advantage for both species were similar to values reported in the literature for members of other xanthid crab species. These values in turn overlapped those reported for calappid, cancrid, majid, and grapsid crabs, and were greater than those of various species of portunid crabs and individual species of fiddler crab, lobster, crayfish, and ghost shrimp. When simultaneously presented with the two species of bivalves, the mud crabs E. depressus chose mussels of M. leucophaeata first and crabs of R. harrisii chose mussels of I. recurvum first about two‐thirds of the time; ultimately, the crabs ate both bivalve species in >50% of the choice experiments. The size range in E. depressus was greater than that in R. harrisii, and crabs of E. depressus opened larger bivalves than did crabs of R. harrisii, although similar‐sized individuals of the two crab species overlapped in their ability to open bivalves of both species. In Mytilopsis leucophaeata, there is probably no size refuge from predation by the mud crabs whereas the larger mussels of I. recurvum do have a refuge in size.     

The influence of some symbionts on the shell-selection behaviour of the hermit crabs, Pagurus pollicarus and Pagurus longicarpus

The influence of some symbionts on the shell-selection by the hermit crabs Pagurus pollicarus and P. longicarpus was examined by placing individual hermit crabs with two similar shells in a choice situation and recording the shell occupied after 12 hr. One shell contained a symbiont species and the other did not. The results indicated that organisms normally found on or in empty shells influence the shell-section by these species of hermit crab. P. pollicarus preferred shells occupied by the sea anemone Calliactis tricolor or by the hydroid Hydractina echinata as opposed to bare shells. P. longicarpus also preferred shells with H. echinata. Both crab species rejected shells with the barnacle Balanus amphitrite. Shells containing the molluscs Crepidula fornicata or C. plana were rejected by the smaller hermit crab P. longicarpus. These molluscs appeared to exert no influence on P. pollicarpus unless they were large or abundant, at which point their weight or occlusion of available space possibly has negative effects on the crab.     

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.     

Individual recognition and odor in rat-like hamsters: behavioral responses and chemical properties

Individual recognition has been studied across a number of taxa and modalities; however, few attempts have been made to combine chemical and biological approaches and arrive at a more complete understanding of the use of secretions as signals. We combined behavioral habituation experiments with gas chromatography-mass spectrometry of glandular secretions from the left and right flank gland and midventral gland of the rat-like hamster, Tscheskia triton. We found that females became habituated to one scent and then could discriminate individuals via another scent source from the same individual only when familiar with the scent donor. However, this prior social interaction was not required for females to discriminate different individuals in single-stimulus habituation-dishabituation tests. Chemical analyses revealed a similarity in volatile compounds between the left and right flank gland and midventral gland scents. It appears that individually distinctive cues are integratively coded by a combination of both flank gland and midventral gland secretions, instead of a single scent, albeit animals show different preferences to the novel scent. Our results suggest that odors from the flank and midventral glands may provide information related to individuality and aid individual recognition in this species and confirm that prior interaction between individuals is a prerequisite for rat-like hamsters to form multi-odor memory of a particular conspecific.