Female Prairie Deer Mice Prefer Conspecific Flesh Over Contraspecific Flesh

Hungry adult female deer mice were presented with freshly asphyxiated conspecifics and house mice. The deer mice showed a reliable preference for the conspecific flesh during the first 2 hr of testing, but this preference was attenuated during the following 20 hr of testing. Previous research has shown that male deer mice prefer contraspecific flesh. The preference of female deer mice for conspecific flesh is attributed to their tendency to be more aggressive toward living conspecifics than are male deer mice and their tendency to avoid living contraspecifics more than do male deer mice.     

Studies of Emotional Reactions VI. Cardiac Responses

Wild-strain male house mice were fostered at birth onto conspecifics, deer mice, or domestic Norway rats. In adulthood, their flesh-eating preferences were tested by allowing them to feed from freshly asphyxiated conspecifics and either deer mice or rats. The mice ate significantly more conspecific flesh than contraspecific flesh, except when the flesh offered was that of the contraspecies upon which the mouse had been fostered at birth. The failure of cross-species-fostered mice to discriminate between their own species and their foster species in flesh-preference tests is attributed to their having learned early in life to respond to the foster species in the same way they normally respond to conspecifics, that is, by approaching them, investigating them, and, when finding them dead, feeding upon them.     

Opposite strain-dependent differences for intermale aggressive behavior elicited by individual housing and housing with a female in the mouse

Male mice of the C57BL/6 strain show a significant increase in aggression toward a nonaggressive male conspecific following 72 hr of individual housing. However, this increase was no longer evident following 2 weeks of individual housing. When housed with a female, C57BL/6 mice show significantly more aggression than singly housed mice of the same strain after 72 hr as well as 2, 4, 8 weeks of differential housing. Male C57BL/6 mice housed with a female also show significantly higher levels of aggression than DBA/2 mice living in the same housing condition after 4 or 8 weeks of differential housing. Finally, male DBA/2 mice individually housed for 8 weeks are significantly more aggressive than mice of the same strain housed with a female for the same time. These results indicate that the increase in aggressive behavior observed following isolation and cohabitation with a female in the mouse is not the same phenomenon. © 1994 Wiley-Liss, Inc.     

Scent marking by male dwarf hamsters (Phodopus sungorus campbelli) in response to conspecific odors

Male hamsters (Phodopus sungorus campbelli) scent marked at greater frequencies in the presence of conspecific odor, either male or female, than in clean areas. Marking rates were not different between male and female odor conditions. In contrast, the pattern of investigation in response to conspecific odor did differ between the male and the female odor conditions. When male odors were used as stimuli, investigative sniffing increased at the scent marking sites but when female odors were used as stimuli investigative sniffing increased throughout the arena. Thus, male dwarf hamsters direct their scent marks at both male and female conspecifics, discriminate between male and female odor, and investigate in a different manner areas scent marked by males and females.     

Further Evidence that Social Interaction Reduces Conditioned Taste Aversions in Mice

Social interactions with other conspecifics affect food selection in mammals. A previous study suggested that male mice attenuate conditioned taste aversion (CTA) by lithium chloride after interacting with an unfamiliar male conspecific. The present study was designed to (a) examine whether interactions with a familiar conspecific would attenuate CTA and (b) investigate sex differences in the social attenuation of CTA in mice. Results indicated that interacting with a familiar conspecific of the same sex following poisoning attenuated conditioned taste aversions only in male mice. The results suggest that the familiarity of conspecifics was not a critical factor in the social attenuation of CTA. Discrepancies between present and previous findings are discussed.     

Sensory cues that elicit ultrasonic vocalizations in female rats (Rattus norvegicus)

Female rats emit ultrasonic vocalizations during copulation. Female vocalizations are associated with darting and other proceptive behavior. In addition, females frequently call while approaching the male. A series of experiments was undertaken to determine whether female rats emit ultrasonic vocalizations in response to other rats or to their odors. Females were exposed either to bedding soiled by males or females or to devocalized conspecifics separated from the subject by a barrier. Females vocalized more to male cues than to female cues, regardless of whether the odor cues were from soiled bedding or from a devocalized conspecific. In addition, subjects vocalized more when presented with a devocalized female rather than a neutral stimulus. Furthermore, devocalized adult males, separated by a barrier, were more effective than either devocalized castrated or juvenile males in eliciting vocalizations; in turn, castrates and juveniles were more effective than neutral stimuli. Female calling was likely induced by odors from the male. In one experiment, the female subject was positioned in such a way that she could neither see or touch the stimulus male. Presentation of tape-recorded male vocalizations did not affect calling by the female. Vocalizations emitted by females in response to male odors may attract males or may facilitate subsequent copulatory behavior by the male.     

Naloxone differentially alters parental aggression by female mice towards conspecific intruders of differing sex

Lactating mice respond differently to male and female conspecific intruders, displaying defensive attack towards the former and offensive attack towards the latter. Two studies are reported in which the effects of naloxone on this differential response pattern were assessed. In the first study, lactating residents were pretreated with saline or naloxone (0.5, 2.5 mg/kg) and consecutively confronted with intruders of differing sex. Results suggested that attack (offensive) against female conspecifics is more sensitive to the inhibitory effects of opiate-receptor blockade than attack (defensive) on males. This conclusion was strengthened in a follow-up study, in which independent groups of lactating residents were used to further examine the effects of naloxone (0.5 mg/kg) on response to male and female intrusion. Analysis indicated that this low dose of naloxone significantly inhibited attack on female, but not on male, intruders. Indeed, in response to male, but not to female, intrusion, naloxone-treated residents showed a significant increase in fear-related behaviour. Findings are discussed in relation to the motivational differences in the response of lactating mice to intruders of differing sex and to possible mechanisms underlying the reported differential effects of opiate-receptor blockade.     

Dissociation of sexual arousal and sexual proclivity in the garden snail, Helix aspersa

Sexual arousal (intensity of courtship) and sexual proclivity (tendency to court) in Helix aspersa can be reliably measured using externally observable correlates. Snails with sexual proclivity are significantly more likely to turn toward an anesthetized conspecific after contacting it than are sexually unreceptive snails. Sexual arousal can be inferred from the stage of a snail's genital eversion, which appears only during courtship. The higher the stage of the eversion, the shorter the time required to complete introductory courtship behavior and the higher the rate of successful copulation, the fewer the number of breaks and pauses during courtship, and the longer the time a snail will spend in contact with an anesthetized conspecific. Sexual proclivity has no effect on feeding or locomotory behavior; however, sexual arousal inhibits feeding and increases locomotor activity. Snails that were allowed daily contact with conspecifics required less time to complete introductory courtship behavior relative to snails that were isolated from conspecifics for 1 week. This suggests that daily contact increases sexual arousal. A greater percentage of isolated snails exhibited courtship behavior than did snails which had experienced daily conspecific contact. This suggests that isolation increases sexual proclivity. These differences indicate that sexual arousal is not merely due to an increase in sexual proclivity.     

Eye as a key element of conspecific image eliciting lateralized response in fish

Visual lateralization in different aspects of social behaviour has been found for numerous species of vertebrates ranging from fish to mammals. For inspection of a shoal mate, many fishes show a left eye–right hemisphere preference. Here, we tested the hypothesis that in fish, there is a key cue in the conspecific appearance, which elicits lateralized response to the whole image of the conspecific. In a series of eight experiments, we explored eye preferences in cryptic-coloured Amur sleeper, Perccottus glenii, fry. Fish displayed left-eye preferences at the population level for inspection of a group of conspecifics, their own mirror image, and a motionless flat model of a conspecific. In contrast, no population bias was found for scrutinizing an empty environment or a moving cylinder. When fry were showed a model of a conspecific in a lateral view with the eye displaced from the head to the tail, they again showed a significant preference for left-eye use. On the other hand, ‘eyeless’ conspecific model elicited no lateralized viewing in fry. Finally, the left-eye preference was revealed for scrutiny of the image of a conspecific eye alone. We argue that in Amur sleeper fry, eye is the element of the conspecific image, which can serve as a ‘key’ for the initiation of lateralized social response. This key element may serve as a trigger for the rapid recognition of conspecifics in the left eye–right hemisphere system. Possible causes and advantages of lateralized perception of social stimuli and their key elements are discussed in the context of current theories of brain lateralization.     

Eggs of a female Japanese quail are more likely to be fertilized by a male that she prefers

Male Japanese quail (Coturnix japonica) that conspecific females preferred in a 10-min, forced-choice test of affiliative preference were more likely than were males not preferred in such a test to fertilize females' eggs when subsequently mated with them, although preferred and nonpreferred males mated equally often with females. Further, the probability that a nonpreferred male would fertilize a female's eggs was significantly increased if she watched while he courted and mated with another female. The results indicate that in Japanese quail (a) affiliative preference reliably predicts females' choices of fathers for their offspring and (b) females may have some degree of control over whether the males with whom they mate actually fertilize their eggs.     

Effects of the menstrual cycle on looking preferences for faces in female rhesus monkeys

Fluctuations of ovarian hormones across the menstrual cycle influence a variety of social and cognitive behaviors in primates. For example, female rhesus monkeys exhibit heightened interest for males and increased agonistic interactions with other females during periods of high estrogen levels. In the present study, we hypothesized that females’ preference for males during periods of high estrogen levels is also expressed at the level of face perception. We tested four intact females on two face-tasks involving neutral portraits of male and female rhesus monkeys, chimpanzees and humans. In the visual preference task (VP), monkeys had to touch a button to view a face image. The image remained on the screen as long as the button was touched, and the duration of pressing was taken as an index of the monkey's looking time for the face stimulus. In the Face-Delayed Recognition Span Test (Face-DRST), monkeys were rewarded for touching the new face in an increasing number of serially presented faces. Monkeys were tested 5 days a week across one menstrual cycle. Blood was collected every other day for analysis of estradiol and progesterone. Two of the four females were cycling at the time of testing. We did not find an influence of the cycle on Face-DRST, likely due to a floor effect. In the VP however, the two cycling individuals looked longer at conspecific male faces than female faces during the peri-ovulatory period of the cycle. Such effects were absent for human and chimpanzee faces and for the two noncycling subjects. These data suggest that ovarian hormones may influence females’ preferences for specific faces, with heightened preference for male faces during the peri-ovulatory period of the cycle. Heightened interest for stimuli of significant reproductive relevance during periods of high conception risk may help guide social and sexual behavior in the rhesus monkey.     

Ejaculate disruption in two species of voles (Microtus): on the PEI matching law.

We permitted male prairie and montane voles (Microtus ochrogaster and M. montanus) five thrusts, without ejaculation, with a female at variable times after a 1st male ejaculated. In both prairie and montane voles, there were fewer sperm, in relation to control conditions, in the female's tract 1 hr after ejaculation if the female received thrusts immediately or 15 min after the ejaculate. There was no such effect after a 50-min delay. There was no significant decrease in litter production in prairie voles caused by thrusts delivered either immediately or after a 15-min delay. Sperm transport in these species is susceptible to disruption for a longer period than in deer mice or rats. The proposal that the postejaculatory interval protects a male from disrupting its own sperm transport (the PEI matching law) appears not to hold for these species.     

Variation in aggressive behavior and anatomo-physiological correlates generated by crowding without physical contact in the house mouse

Behavioral, physiological (i.e., endocrine), and anatomical consequences of crowding in mice were studied in a situation where animals were in auditory, visual, olfactory, and tactile contact but restrained from full physical interactions, to prevent overt aggression. Males that cohabited with females undisturbed by neighboring conspecifics showed greater propensity to attack same-sex intruders and had higher plasma testosterone levels than did their “crowded” counterparts, that is, males cohabiting with females and housed adjacent to other male/female pairs. In this respect, the latter animals resembled submissive males. However, a significant increase in weight of androgen-dependent target organs (i.e., seminal vesicles and preputial glands) was found in crowded males. These data indicate that despite the observed inhibition of social aggression these males are not physiologically comparable (homologous) to male mice that experienced defeat and the stress of submission during fighting. The intriguing possibility that different conversion pathway of testosterone are accelerated, as a result of social communication, in males living in these two environments and the behavioral implications of these possibilities are discussed. Finally, the parental behavior of crowded animals, although not freely interacting with each other, was disrupted, causing a marked decrease in reproductive success. In this situation a high incidence of infanticide of their offspring by both parents was observed, whereas this behavior was virtually absent in non-crowded male/female pairs.     

Sex differences in investigatory and grooming behaviors of laboratory rats (Rattus norvegicus) following exposure to novelty

Prior research suggested that during exposure to novel stimuli, rodent investigation and self-grooming behaviors may be sexually dimorphic and interact with ambient illumination. To test this notion we compared the behavior of adult male and female groups of Long-Evans hooded rats in normal room lighting (860 lx) and in very dim, red light (0.2 lx) following exposure to a novel juvenile conspecific. Illuminance level had little or no effect, but investigatory and subsequent self-grooming behaviors of males were substantially greater than those of females, and females engaged in greater ambulatory activity than did males. In a second experiment adult males and females were exposed to a novel inanimate object. No reliable sex differences were observed. We conclude that social novelty, as provided by exposure to a juvenile conspecific, stimulates greater investigation and postinvestigatory self-grooming than exposure to a novel inanimate object and that exposure to novel conspecifics presents a useful method for the investigation of sex differences, gonadal hormone effects, and interactions of hormones with neurotransmitter systems governing motor control systems.     

Caching at a distance: a cache protection strategy in Eurasian jays

A fundamental question about the complexity of corvid social cognition is whether behaviours exhibited when caching in front of potential pilferers represent specific attempts to prevent cache loss (cache protection hypothesis) or whether they are by-products of other behaviours (by-product hypothesis). Here, we demonstrate that Eurasian jays preferentially cache at a distance when observed by conspecifics. This preference for a ‘far’ location could be either a by-product of a general preference for caching at that specific location regardless of the risk of cache loss or a by-product of a general preference to be far away from conspecifics due to low intra-species tolerance. Critically, we found that neither by-product account explains the jays’ behaviour: the preference for the ‘far’ location was not shown when caching in private or when eating in front of a conspecific. In line with the cache protection hypothesis we found that jays preferred the distant location only when caching in front of a conspecific. Thus, it seems likely that for Eurasian jays, caching at a distance from an observer is a specific cache protection strategy.     

Effects of early exposure to ventral gland odor on physical and behavioral development and adult social behavior in Mongolian gerbils.

Comparisons were made between male and female gerbils reared by ventral gland-excised and intact patents. Repeated measurements before and after puberty failed to reveal an effect of gland odor exposure on body weight, ventral gland size, open-field defecation, and time of vaginal opening. Exposed animals were more attracted than nonexposed animals to a strange male's gland odor during preference tests involving "marked" and "unmarked" paper strips. Opposite-sex pairs of exposed animals engaged in more social behavior than did nonexposed pairs, but there was no difference in fighting frequency or, during extended cohabiitation, in fecundity. While early exposure to gland odor apparently does not affect physical maturation, it may enhance later responsiveness to stimuli (gland odors) that are useful in locating conspecifics and that facilitate social interactions between previously unacquainted gerbils.     

Conserved evolutionary history for quick detection of threatening faces

Humans quickly recognize threats such as snakes and threatening faces, suggesting that human ancestors evolved specialized visual systems to detect biologically relevant threat stimuli. Although non-human primates also detect snakes quickly, it is unclear whether primates share the efficient visual systems to process the threatening faces of their conspecifics. Primates may not necessarily process conspecific threats by facial expressions, because threats from conspecifics in natural situations are often accompanied by other cues such as threatening actions (or attacks) and vocal calls. Here, we show a similar threat superiority effect in both humans and macaque Japanese monkeys. In visual search tasks, monkeys and humans both responded to pictures of a threatening face of an unfamiliar adult male monkey among neutral faces faster than to pictures of a neutral face among threatening faces. However, the monkeys’ response times to detect deviant pictures of a non-face stimulus were not slower when it was shown among threat faces than when it was shown among neutral faces. These results provide the first evidence that monkeys have an attentional bias toward the threatening faces of conspecifics and suggest that threatening faces are evolutionarily relevant fear stimuli. The subcortical visual systems in primates likely process not only snakes, but also more general biological threat-relevant stimuli, including threatening conspecific faces.     

Odor cue determinants of urine marking in male rats (Rattus norvegicus)

This study examined the spatial distribution of urine marking by sexually inexperienced male rats under six odor conditions: minimum odor (baseline), conspecific male urine, conspecific female urine, an animal's own urine, male gerbil urine, and amyl acetate. The gerbil urine and amyl acetate conditions were included to test the theory that marking, rather than being elicited by and directed as a display to appropriate conspecifics, occurred to the introduction of any novel or disruptive odor. The subject's own urine was used to test the theory that the animal marked to maintain an optimum level of its own odor in the environment. The results showed that marking was directed predominantly at objects in the environment over which the animal could readily pass. All odor conditions except "own odor" sharply increased marking over baseline levels. Marking decreased with repeated exposure to particular stimuli. The results strongly supported the theory that urine marking, at least in sexually inexperienced male rats, is produced by novel odor stimuli introduced into a familiar environment.     

Cattle discriminate between familiar and unfamiliar conspecifics by using only head visual cues

Faces have features characteristic of the identity, age and sex of an individual. In the context of social communication and social recognition in various animal species, facial information is relevant for discriminating between familiar and unfamiliar individuals. Here, we present two experiments aimed at testing the ability of cattle (Bos taurus) to visually discriminate between heads (including face views) of familiar and unfamiliar conspecifics represented as 2D images. In the first experiment, we observed the spontaneous behaviour of heifers when images of familiar and unfamiliar conspecifics were simultaneously presented. Our results show that heifers were more attracted towards the image of a familiar conspecific (i.e., it was chosen first, explored more, and given more attention) than towards the image of an unfamiliar one. In the second experiment, the ability to discriminate between images of familiar and unfamiliar conspecifics was tested using a food-rewarded instrumental conditioning procedure. Eight out of the nine heifers succeeded in discriminating between images of familiar and unfamiliar conspecifics and in generalizing on the first trial to a new pair of images of familiar and unfamiliar conspecifics, suggesting a categorization process of familiar versus unfamiliar conspecifics in cattle. Results of the first experiment and the observation of ear postures during the learning process, which was used as an index of the emotional state, provided information on picture processing in cattle and lead us to conclude that images of conspecifics were treated as representations of real individuals.     

Counselor preference and anticipated comfort ratings for a clinic sample of sexually abused versus non-abused girls

We compared counselor preference and anticipated comfort ratings for sexually abused and non-abused girls. Twenty-five sexually abused and 22 non-sexually abused girls between ages 7 and 17 participated in an initial psychological evaluation at a university outpatient clinic. Results obtained using the Counselor Preference and Comfort Survey revealed no significant difference between sexually abused and non-abused girls' ratings of their preference for male or female counselors and their anticipated comfort with male counselors; non-abused girls expressed significantly higher anticipated comfort with female counselors than did their abused counterparts. It was illustrated that younger girls', abused and non-abused, were more likely to prefer a female counselor and to anticipate being more comfortable with a female counselor. In addition, older non-abused girls were more likely to prefer a male counselor and more likely to anticipate being comfortable with a male counselor. Participants in both groups expressed a higher preference for and anticipated comfort with female counselors as compared with male counselors.