Use of olfaction for sexual recognition in the subterranean rodent<Emphasis Type="Italic">Ctenomys talarum</Emphasis>

The ability of the tuco-tucoCtenomys talarum Thomas, 1898 to recognize sex by olfactory cues contained in urine, faeces and soiled shavings was tested by using preference tests. Nonbreeding tuco-tucos selected odours from opposite-sex rather than same-sex conspecifics. This pattern differed between sexes: females spent more time sniffing male than female odours for all scent sources whereas males did not show any difference in the time they spent investigating odours of each sex for each tested odour sources. Dissimilarities in odour selections between sexes may be attributed to a different combination of factors involved in olfactory interest for each sex. The function of gender cues recognition is discussed.     

Behavioural development of conspecific odour preferences in bank voles,Clethrionomys glareolus

Biological odours of conspecifics are known to have strong influences on behavioural interaction in bank voles Clethrionomys glareolus. This experiment tested two hypotheses. (1) Olfactory cues from familiar and unfamiliar mature opposite-sex conspecifics differ in their attractiveness to males and females, and their behavioural reactions change with age. (2) A genetically based mechanism is involved in female recognition of kin.In a two-choice preference test, prepubertal males and females were more attracted to familiar than to unfamiliar odours of opposite-sex conspecifics, as manifested by more time spent sniffing familiar voles. As the young reached sexual maturity they shifted their odour preferences. Mature males and females preferred the novel odour of unrelated opposite-sex conspecifics to that of relatives. The results of experiments testing the second hypothesis indicate that females use a genetically based mechanism to recognise their kin. Young and mature females were able to recognise the odour of their biological but socially unknown fathers, and showed the same pattern of behaviour as females in previous experiments.The possible biological functions of kin recognition in bank voles are discussed.     

鳄蜥对熟悉和陌生个体气味的辨别

个体辨别对于减少同种争斗以及配偶选择具有重要意义。我们用棉棒粘取鳄蜥(Shinisaurus crocodilurus)尿液作为气味源,以香水作为对照,测定鳄蜥对熟悉个体气味、陌生个体气味以及香水的舔舌次数和舔舌潜伏期,来探讨鳄蜥通过化学信息辨别熟悉和陌生个体的能力。结果显示,不论是雌性还是雄性,对不同个体尿液的舔舌次数均显著高于对香水的,舔舌潜伏期显著短于香水的;尽管雄性对陌生同性个体气味与熟悉同性个体气味的舔舌次数无显著差异,但对前者的舔舌潜伏期显著短于后者;雄性对陌生雌性气味的舔舌次数显著多于熟悉雌性气味的,对前者的舔舌潜伏期显著短于后者;雌性对陌生雄性气味的舔舌潜伏期显著短于对熟悉雄性气味的;雄鳄蜥对陌生雌性气味的舔舌次数显著多于雌鳄蜥对陌生雄性的。结果表明,鳄蜥能辨别同种个体的化学信息,并能通过化学信息来辨别熟悉和陌生个体,推测鳄蜥的这种辨别能力对其领域分配以及繁殖交配有重要作用。     

Scent-marking behaviour in response to conspecific odours by the rat, Rattus norvegicus

The scent-marking behaviour of male and female rats in response to conspecific odours was investigated in two experiments. The results of the first experiment indicated that exposure to conspecific odours generally led to an increase in marking rates. However, no sex differences were found, and large differences in marking responses according to the sex of the odour donor were only found for dioestrous females. These results do not suggest that the primary function of scent-marking in this species is sexual. In the second experiment, odour sources differed not only in the sex of the donor, but also in their relative familiarity to the animal being tested. This experiment showed that males marked more in response to odours from familiar (non-related) females. Females did not differ significantly on measures of marking but did display greater interest in odours from unfamiliar males. The results are discussed in relation to possible functions of marking in this species.     

雌性布氏田鼠对雄鼠气味的辨别

通过雌性布氏田导其配偶和陌生雄鼠气味的辨别实验,以及无交配经历的成年雌鼠对社会等级不同的陌生雄鼠气的辨别实验发现,有生育经历的雌鼠对陌生雄鼠气味的探究行为明显多于对配偶气味的控究,但雌鼠在配偶雄鼠气味周围的停留时间、自身修饰行为和何处行为的发生频次和持续地陌生雄鼠,没有交配经历的雌鼠对处于从鼠地位的雄性个体气味探究行为多于对优势雄性的控究,而其他行为表现没有明显差异。表明,雌性布氏田鼠可以利用气味     

Olfactory Discrimination of Individual Scents in the Subterranean Rodent Ctenomys talarum (tuco-tuco)

Biological odours that convey cues regarding individual identity can provide valuable information mediating many aspects of mammalian social relationships such us dominance hierarchies, group memberships, territorial and mating activities. The ability of the subterranean rodent, tuco‐tuco (Ctenomys talarum), to discriminate between soiled shavings, urine and faeces from different individuals was investigated using the habituation–discrimination paradigm. Discrimination by both males and females was tested using scents obtained from same‐ and opposite‐sex individuals. Each test subject was habituated for three consecutive days to odour samples from the same individual; on the fourth day a scent from a novel individual was provided. For all odour sources, animals spent significantly less time investigating the habituation scent over successive trials, indicating that animals perceived the stimulus as familiar. For all stimuli, test subjects spent more time investigating the novel odour, rather than the familiar one. Animals spent more time investigating soiled shavings than urine or faeces. Both males and females discriminated novel from familiar odours in shavings and urine regardless of the gender of the odour donors. In contrast, test animals discriminated between familiar and novel odours in feces only when the fecal donors were of different sex from subjects. Possible territorial and reproductive functions of individual scent discrimination are discussed.     

Persistence of the Attractiveness of Two Sex-specific Scents in Meadow Voles,Microtus pennsylvanicus

The function of an odour may be reflected in its fade-out time in the environment. In this study, we investigated fade-out times of two specific odours, the anogenital area scent and that of the posterolateral region. These two odours support opposite-sex preferences in male and female meadow voles, Microtus pennsylvanicus, but convey nonidentical information to conspecifics during the breeding season. The first experiment tested whether meadow voles respond preferentially to scents that were aged for 15 min (fresh) to 30 d. Males preferred female anogenital area scent to male anogenital area scent if both scents were ≤ 10 d old. By comparison, females preferred male anogenital area scent to female anogenital area scent if the scents were ≤ 25 d old. However, male and female voles preferred the posterolateral scent of males to that of females if the scents were ≤ 1 d old. Thus, fade-out times for these two scents differ for males and females, suggesting different functions. In the second experiment, male and female voles preferred fresh anogenital area scent and fresh posterolateral region scent compared with those same scents that were older. This result suggests that older scents may have lost information over time about the sex of the donor. Overall, data from both experiments indicate that voles may use specific scents for communication in different social contexts.     

Chemosensory Recognition of Familiar and Unfamiliar Conspecifics by the Scincid Lizard Eumeces laticeps

The ability of broad-headed skinks (Eumeces laticeps) to distinguish familiar from unfamiliar individuals of the opposite sex and themselves from other individuals of the same sex using only chemical stimuli was examined experimentally. Cloacal chemical stimuli were presented to lizards on moistened cotton swabs and numbers of tongue-flicks performed in 60 s were recorded. Males emitted significantly greater numbers of tongue-flicks in response to chemical cues from unfamiliar females than of female cagemates. Response rates of males housed with females and males housed alone to chemical stimuli from unfamiliar females did not differ. Chemical stimuli from unfamiliar males elicited significantly more tongue flicks from males than their own or deionized water, but their own stimuli elicited no more than the odourless control. Females tongue-flicked significantly more in response to cloacal chemical stimuli from unfamiliar males than from male cagemates. The findings indicate that both sexes of broad-headed skinks can discriminate between chemical stimuli of familiar and unfamiliar individuals of the opposite sex and that males can distinguish their own cloacal chemicals from those of unfamiliar males. The possible functions of these chemosensory capacities, including location of mates by scent-trailing and assessment of the presence of sexual competitors, are discussed in relation to the social behaviour of E. laticeps.     

Sexual behaviour and its olfactory control in the desert woodrat (Neotoma lepida lepida)

In studies 1 and 2 nine pairs of desert woodrats (Neotoma lepida lepida) were observed for copulatory behaviour when the female was in a state of naturally occurring oestrus (study 1) and following ovariectomy and oestrogen and progesterone replacement (study 2). Males and females respond in a similar way under conditions of natural and hormone-induced oestrus. Males show a consummatory pattern involving multiple mounts and ejaculations, with ejaculations occurring after single intromissions. Females show the lordosis reflex accompanied by hop-and-dart and ear-wiggling responses. In addition, both sexes show appetitive precopulatory behaviours; the male emits an audible rasping vocalization as he trails and mounts the female, following a period of intense sniffing of the female's anogenital region. The female also frequently approaches and sniffs the male. In study 3, the role of female odours in the sexual behaviour of the male was examined in eight of the nine pairs used in studies 1 and 2. This was done by applying to the anogenital region of ovariectomized females a combination of urine and vaginal secretions taken from familiar and unfamiliar, and oestrogen-primed or non-oestrogen-primed females. The results show that odours from oestrogen-primed females are not sufficient to elicit male sexual behaviour, if the female is not sexually active. In study 4 the eight males were tested for their preferences for urine and vaginal secretion odours taken from females in different reproductive states and applied to cotton swabs. These males spent more time sniffing unfamiliar oestrous odours than unfamiliar non-oestrous odours and more time sniffing oestrous odours from a familiar female over those taken from an unfamiliar female.In study 5, 12 sexually active males were tested with oestrogen-primed females before and after either olfactory bulb removal or sham-surgery. Bulbectomized animals ceased copulating with females although females showed precopulatory approaches.Taken together, these studies suggest that normal sexual behaviour in the male woodrat requires that the female both possess the attractive odours (of oestrus) and that she engage in appetitive precopulatory behaviour.     

Right-nostril dominance in discrimination of unfamiliar, but not familiar, odours

In a recent PET study on processing of unfamiliar odours we observed that odour discrimination performance was superior during right compared with left nostril presentations, and that mainly the right cerebral hemisphere was activated. In the present study we investigated whether the asymmetric performance is present also during the processing of familiar odours. Seventy-one right-handed healthy subjects (age 21-49 years, 40 females) with normal nasal anatomy and olfactory thresholds participated. Forty pairs of odours (20 familiar and 20 unfamiliar) were presented in the same/different paradigm, alternating nostrils and balancing the order. The number of errors during the discrimination task was compared with respect to nostril and odour familiarity. The overall odour discrimination performance was superior on the right side. However, this difference was valid only for unfamiliar odours, whereas the performance for familiar odours was symmetrical. Familiar odours were easier to discriminate than unfamiliar ones. The present data are congruent with the idea of a semantic influence on odour processing. Odours seem to be processed with a right sided preponderance when not clearly familiar, and symmetrically when language becomes involved. Future studies on odour processing should therefore take into account odour familiarity and side of presentation.     

Sex differences in olfactory social recognition memory in meadow voles,Microtus pennsylvanicus

Terrestrial mammals, like rodents, use odors, and scent marks to indicate their presence in an area to conspecifics. These odors convey information about the scent donor's genotype, sex, condition, and age. The ability to discriminate among the scent marks of conspecifics and later recollect the identity of the donor is essential for choosing between familiar and unfamiliar mates. We tested the hypothesis that the promiscuous meadow vole (Microtus pennsylvanicus) can recollect the odor of a familiar, opposite-sex conspecific and distinguish it from that of an unfamiliar, opposite-sex conspecific. We also hypothesized that because reproductive success is highly skewed among male meadow voles and competition for mates is intense, males will be more likely than females to recollect the odor of a familiar, opposite-sex conspecific and distinguish it from that of an unfamiliar, opposite-sex conspecific, for a longer period of time. Using a habituation task, we first exposed the voles, 4 times successively, to the anogenital area scent of an opposite-sex conspecific. Then, 1 hr, 24 hrs, 72 hrs, or 96 hrs after the fourth exposure, voles were presented with the odor of the donor from the exposure phase (familiar donor) and that of an unfamiliar, opposite-sex conspecific. Female meadow voles spent similar amounts of time investigating the scent of the familiar male donor and that of an unfamiliar male donor after the 1-hr and 24-hr intervals. Male meadow voles, however, spent more time with the scent of an unfamiliar female donor than that of the familiar female donor after the 1-hr, 24-hr, and 72-hr intervals, suggesting that male voles could recollect the scent mark of a familiar female for at least three days. The implications of these sex differences in social memory may reflect the different strategies male and female meadow voles use in the recognition of previous and potential mates. Recognition of an individual's scents may enhance fitness by allowing animals to direct appropriate behaviors toward those individuals.     

幼小鼠对种内几种化学信息的识别和反应

50年代以来,国际上相继开展了一些关于化学信息在小家鼠繁殖中作用的研究,并在实验室中揭示了一些反应:如集群雌鼠气味使雌鼠性周期延长的Lee-Boot效应,雌鼠气味能解除集群雌鼠对性周期的抑制、并促使它们同期发情的Whitten效应,以及陌生雄鼠气味中断妊娠的Bruce效应等等。但是,在成鼠间起作用的几种化学信息,是否能被幼鼠感受,对幼鼠的发育和性成熟是否产生影响,还是一个未知的问题。 影响小鼠发育的因素很多,除环境因子外,近来还出现了有关社群因素中外激素对小鼠性成熟影响的报道,发现雄鼠或给予雄激素的雌鼠有促进幼雌鼠性成熟的作用,范志勤发现父本气味和陌生雄鼠气味对幼雌鼠性成熟均有促进作用。但是,目前关于种内雌鼠气味、集群雌鼠气味、幼鼠气味影响性成熟的研究尚不多见。有关各种气味对性成熟效应的比较的报道亦少。本文的目的在于通过实验方法,阐明种内的几种化学信息,诸如父本、陌生雄性、雌性、集群雌性、幼雌等几种气味,对幼雌小鼠性成熟的影响,并据此了解幼鼠识别这几种信息的能力。     

Pheromonal Recognition of Females Takes Precedence over the Chromatic Cue in Male Iberian Wall Lizards Podarcis hispanica

Sex recognition is based on colour signals in many species of lizards. However, olfactory stimuli are also clearly involved, and many species might rely more on chemoreception. We aimed to examine whether colour pattern or odours, or both, are used in sex recognition and which cues elicit courtship of females by males of the lizard Podarcis hispanica . We experimentally manipulated the coloration and odour of female P. hispanica , thereby creating groups with all combinations between coloration and odour of males and females. Using data from staged encounters, we compared the responses of resident males to manipulated and unmanipulated individuals (males and females). Responding males reacted significantly more aggressively to female intruders with male odours, independently of their coloration. Nevertheless, coloration seemed to be important in long-distance sex recognition since, in the first minutes, females painted as females received a lower number of aggressive responses. Both colour and odour were important in eliciting male courtship. However, females painted as females and with female odours were preferentially courted. Comparisons with unmanipulated male and female intruders agreed with these expectations. Therefore, at close range, odoriferous cues seem to be more important than colour patterns in sex recognition, but female coloration is also useful at long range to deter the aggressive response of males and to elicit courtship in conjunction with odours.     

Seasonal control of odour preferences of meadow voles (Microtus pennsylvanicus) by photoperiod and ovarian hormones

During the spring-summer breeding season, female meadow voles prefer odours of males over those of females, but in the autumn-winter season of reproductive quiescence this preference is reversed. Females housed in long (14 h light/day) and short (10 h light/day) photoperiods, respectively, had odour preferences comparable to those of spring and autumn voles, respectively. The preference of long-photoperiod voles for male over female odours was reversed by ovariectomy and restored by treatment with oestradiol. By contrast, neither ovariectomy nor oestradiol affected odour preferences of short-photoperiod voles. Long days appear to influence olfactory preferences by altering ovarian hormone secretion. The failure of oestradiol to affect odour preferences in short photoperiods suggests that the neural substrates mediating this behavioural response are refractory to oestrogens during the nonbreeding season.     

Influence of gonadal hormones on odours emitted by male meadow voles (Microtus pennsylvanicus).

Free-living male meadow voles (Microtus pennsylvanicus) emit odours that are attractive to females at the beginning, but not at the end, of the breeding season. The effect of gonadal hormones on female-attractant cues was examined in males born and reared in long (14 h light day-1) and short (10 h light day-1) photoperiods that simulate daylengths in the breeding and nonbreeding seasons, respectively. Gonadectomy affected the attractant properties of odours emitted by long photoperiod, but not short photoperiod, males. Long photoperiod females preferred odours of intact rather than those of gonadectomized long photoperiod males, and odours of gonadectomized long photoperiod males rather than those of intact short photoperiod males. Females did not show a preference between the odours of intact and castrated short photoperiod males. Gonadal hormone replacement in males affected female responses to the odours emitted by long photoperiod, but not short photoperiod, gonadectomized males. Long photoperiod females did not display a preference between odours of intact long photoperiod males and gonadectomized long photoperiod males treated with testosterone or oestradiol. We conclude that in spring and summer gonadal hormones increase attractiveness of male odours; this effect may require aromatization of testosterone to oestradiol. Substrates that control attractiveness of odour cues in male voles appear to be unresponsive to androgens during the nonbreeding season.     

Familiarity and flexible mating strategies of a solitary rodent, Dipodomys ingens

Because mating is a product of individual reproductive strategies that may vary with changing conditions, we predicted variable mating behaviour in an arid-adapted, territorial rodent, the giant kangaroo rat, Dipodomys ingens. We also predicted that familiarity would facilitate nonaggressive courtship and mating in this solitary rodent. Through direct observations in the field, we found that mating varied from exclusive to multiple partners. Where densities were low, and on nights when multiple females were in oestrus, each animal mated with one member of the opposite sex. In conditions where the operational sex ratio was skewed towards multiple males, males footdrummed and competed for females. Males were able to mate with one or two females in adjacent territories, and they successfully competed for these same females throughout the breeding season. Females that mated exclusively with one male had more pups emerge from the burrow compared with females that experienced male competition. Females allowed nearest neighbour males to enter their burrows, and they engaged in more nonaggressive contact with close neighbours than with other males. Paired encounters in the field showed less aggression towards neighbours than strangers. In laboratory tests, females were less aggressive towards and allowed more contact with familiar than unfamiliar males. These results show that D. ingens can alter mating strategies as conditions change. Familiarity is an important factor in nonaggressive interactions between males and females and may be important to mate preferences in females during reproduction. The less aggressive behaviour to neighbours than to strangers (‘dear enemy’ phenomenon) is consistent with other solitary animals that defend multipurpose territories. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Recognition of interspecific familiar versus unfamiliar odours among bank voles and yellow-necked mice

Two experiments (laboratory and field-laboratory) were designed to determine whether individual bank volesClethrionomys glareolus (Schreber, 1780) and yellow--necked miceApodemus flavicollis (Melchior, 1834) could distinguish heterospecific odour cues from familiar and unfamiliar individuals. In the laboratory experiment each male bank vole was familiarized for 24 h with odour (cotton wool impregnated with urine and faeces) of male yellow-necked mice and yellow-necked mice were familiarized with odour of male bank voles. In the field-laboratory experiment the individual bank voles and yellow-necked mice captured at the same point were considered familiar and transfered to the laboratory. In laboratory, these individuals were tested in a box (for 5 h) affording them the choice between the odours of familiar and unfamiliar heterospecific males. Bank voles discriminated between familiar and unfamiliar yellow--necked mouse odours. Male yellow-necked mice seemed to have a similar ability to recognise odours of familiar bank voles. It is proposed that interactions between these two species occur not only on the species level, but also on the level of individual. This phenomenon (probably asymmetric) can play an important role in spatial orientation, and influence direct contacts between individuals of these species.     

Odour-genes eovariance and differential investigation of individual odours in the Mus species complex

Previous research using habituation techniques has demonstrated that greater genetic similarity between two individuals is associated with more similarity in the qualities of their individual odours ('odour-genes eovariance'). We assessed odour similarities across species in two pairs of genetically close species within the Mus species complex (M. musculus and M. domesticus; M. spicilegus and M. macedonicus). Subjects treated odours within each species pair as similar compared with an odour from the other species pair. Subjects also treated odours of M. spicilegus males from the same population as similar compared with the odour of M. spicilegus males from a different population. This confirms odour-genes eovariance across species and within populations and also supports previous findings that odour similarities are more salient than specific odour markers. When adult males were presented with odours of females from two different heterospecific species, subjects spent more time investigating the odour from his own species pair than the other species pair, indicating greater interest in the odour of the closer heterospecific and demonstrating that odour-genes eovariance is reflected in behavioural responses to odours. Implications of odour-genes eovariance as a basis for identifying degrees of genetic relatedness of unfamiliar individuals through similarities in individual odours are discussed.     

Foraging and mate-finding in the silver Y moth, Autographa gamma (Lepidoptera: Noctuidae) under the risk of predation

Animal foraging and reproductive behaviour is influenced by other simultaneous demands such as predator avoidance. The trade-offs between these demands may depend on sex or mating experience. This study demonstrates that the olfactory-mediated foraging and mate-seeking behaviours in the silver Y moths, Autographa gamma , are affected by auditory cues mimicking their bat predators. Both males and females changed their foraging behaviour under simulated predation risk. Fewer moths reached the odour source following sound stimulation and the time to find the odour source increased by up to 250%. However, there were no significant differences between male and female ability to reach the plant odour source or the duration of the flight towards the source when stimulated with ultrasound. Hence females are not more cautious than males when observed in the same behavioural context. Risk-taking in males was independent of whether they were flying toward a flower odour or sex pheromones having equal attractive value. This indicates that the trade-off between olfactory and acoustic cues is independent the type of odour. Mated females were not as strongly affected by sound as non-mated, indicating that flower odours have a higher adaptive value for mated females, suggesting that some processes following mating experience influence the trade-off between flower odours and simulated bat sounds.     

Olfactory cues in discrimination among individuals in dominance hierarchies in the cockroach, Nauphoeta cinerea

ABSTRACT. The purpose of this study was to explore the olfactory recognition mechanisms used by individual subordinate male cockroaches, Nauphoeta cinerea (Olivier), in a dominance hierarchy. Results of two independent sets of experiments, one using an olfactometer and the other using an arena, suggest that olfactory cues are important to males. Subordinate males did not avoid dominant male odour in an olfactometer but could discriminate between the odours of familiar and unfamiliar individual dominant males, preferring the odour of the dominant male with which they had previous social contact. Since test subordinates did not avoid dominant male odours in the olfactometer, it is possible that the distance an individual remains from a dominant is important. To test this, individual dominant and subordinate males were tethered in the centre of an arena. Subordinate males were introduced into the arena and allowed to approach the tethered male. They approached tethered dominants and subordinates differently, and tended to keep away from the dominants. Tethered males unfamiliar to the test animals were avoided as well.