Do pigs find a familiar odourant attractive in novel surroundings?

Sixty-four DurocxLandrace pigs (Sus scrofa) of both sexes were reared from birth to 6 weeks of age in either fresh air or an atmosphere containing an artificial odourant (Ambi-Pur). Their behavioural responses to a novel environment (a modified open field) were then observed over 1h when the test arena contained either the familiar Ambi-Pur odourant or ammonia gas at 45ppm. Although members of other mammalian and avian species are attracted to familiar odours in otherwise novel surroundings, the presence of Ambi-Pur had no effect on the pigs' readiness to enter the novel arena from a sheltered area or on other fear-related behaviours following entry (p>0.05). Pigs kept in fresh air from weaning until test were generally less active and spent less time at the centre of the open field if the test was carried out in an ammoniated atmosphere rather than fresh air; this suggests that they found ammonia aversive. On the other hand, the presence of ammonia at test accelerated approach to the centre of the open field and increased the number of entries into that area and the percentage of time spent there as well as overall activity in pigs that had also been exposed chronically to this gas at 43ppm from weaning until testing at 6 weeks (p<0.05). Thus, after chronic exposure to either ammonia gas or an artificial odourant, ammonia was the only stimulus that appeared to act as an attractive agent for pigs placed in an otherwise novel environment.     

Kin recognition in Bufo scaber tadpoles: ontogenetic changes and mechanism

Ontogenetic changes in kin-recognition behavior, effect of social environment on kin-recognition ability, and use of visual and chemical cues in kin recognition have been studied in tadpoles of Bufo scaber after rearing them with kin, in mixed groups, or in isolation from Gosner stage 12 (gastrula). By use of a rectangular choice tank the tadpoles were tested for their ability to choose between (a) familiar siblings and unfamiliar non-siblings, (b) unfamiliar siblings and familiar non-siblings, and (c) unfamiliar siblings and unfamiliar non-siblings. When tested without any stimulus groups in the end compartments of the tank, random distribution was observed for the tadpoles and no bias for the apparatus or the procedure. In the presence of kin and non-kin in the end compartments, significantly more tadpoles spent most of their time near kin (familiar or unfamiliar) rather than near non-kin during early larval stages, up to stage 37. After stage 37 (characterized by the differentiation of toes), test tadpoles showed no preference to associate with kin, suggesting an ontogenetic shift in the kin-recognition ability in B. scaber. In experiments involving selective blockade of visual or chemical cues the test tadpoles preferentially associated near their kin on the basis of chemical rather than visual cues. These findings suggest that familiarity with siblings is not necessary for kin recognition and that kin-recognition ability is not modified after exposure to non-kin by mixed rearing. The findings for B. scaber indicate a self referent phenotype matching mechanism of kin recognition which is predominantly aided by chemical rather than visual cues.     

The ontogeny of kin recognition in tadpoles of the toadBufo melanostictus (Anura; Bufonidae)

The ontogeny of kin recognition and influence of social environment on the development of kin recognition behaviour was experimentally investigated in tadpoles of Bufo melanostictus that lived in aggregations and showed low larval dispersion. Embryos and tadpoles of the toad were reared as (i) kin only, (ii) with kin and non-kin (separated by a mesh screen), and (iii) in isolation. They were tested for the ability to discriminate between (i) familiar siblings and unfamiliar non-siblings, (ii) familiar siblings and familiar non-siblings and, (iii) unfamiliar siblings and unfamiliar non-siblings. All tadpoles were fed on boiled spinach before conducting trials. Preference of test tadpoles to associate near the end compartments whether empty or containing members of specific stimulus groups was assessed using a rectangular choice tank. When tested in tanks with empty end compartments, the test tadpoles showed random distribution and thus no bias for the apparatus or the procedure. In the presence of kin/non-kin in the end compartments a significantly greater number of test tadpoles spent the majority of the time near familiar or unfamiliar kin rather than near familiar or unfamiliar non-kin. Kin discrimination ability persisted throughout larval development. Familiarity with siblings is not required for discriminating kin from non-kin, and kin discrimination ability is not modified following exposure to non-kin. Also, involvement of dietary cues is unlikely to be the prime mechanism of kin recognition inB. melanostictus unlike in some other anurans.     

Olfactory Communication and Neighbor Recognition in Giant Kangaroo Rats

We hypothesized that olfactory communication facilitates neighbor recognition in the giant kangaroo rat, Dipodomys ingens , and is therefore influential in coordinating social interactions in this solitary, desert rodent. We tested whether (i) D. ingens can discriminate between odors of same- and opposite-sex conspecifics; and (ii) the kangaroo rats exhibit scent preferences based on familiarity. In habituation-discrimination tests, we found that both genders distinguish differences between the scent of individuals of the same- and opposite-sex. In olfactory preference tests, both males and females spent significantly more time investigating the scent of their familiar cagemate than the scent of an unfamiliar conspecific. Giant kangaroo rats may be able to recognize familiar neighbors from olfactory cues, thus supporting a hypothesis of neighbor recognition. Neighbor recognition may be an important mechanism of social interactions in this endangered species.     

Effects of an acute stressor on fear and on the social reinstatement responses of domestic chicks to cagemates and strangers

Genetic selection for appropriate levels of sociality (motivation to be with conspecifics) could benefit poultry welfare and performance. Runway tests that require chicks to traverse a corridor in order to reach other chicks in a goal box are commonly used to measure this behavioural trait. However, we need to determine if the chicks' responses in such tests are sensitive to certain experiential variables before we can recommend possible selection criteria for future breeding programmes. The present study focused on fear and on the identity of the stimulus birds. Broiler chicks either remained undisturbed or were exposed to an acute stressor (mechanical restraint) before their tonic immobility fear responses were measured 1h later in Experiment 1. Exposure to the stressor significantly prolonged tonic immobility and, hence, presumably, underlying fear levels. In Experiment 2, the responses of stressed chicks and undisturbed controls were assessed when they were tested individually in a runway with a goal box containing either familiar or unfamiliar chicks of the same age. Our finding that stressed chicks emerged from the start box sooner and spent longer near the stimulus birds suggests that exposure to a frightening event increased social reinstatement motivation. Furthermore, social affiliation was more pronounced when the goal box contained familiar cagemates rather than strange chicks, regardless of prior treatment. This finding demonstrates that broiler chicks that were housed in groups of twelve can discriminate between familiar and unfamiliar conspecifics encountered in novel surroundings. Thus, sociality was positively associated with fearfulness and broilers clearly showed social discrimination in runway tests. These findings highlight the dangers of disregarding variables, such as fear and the capacity for social recognition in tests of social motivation. We strongly recommend that exposure to frightening events prior to test should be avoided and that the identity of the birds in the runway goal box should be standardized, i.e. either familiar or unfamiliar, and noted.     

Odor-based recognition of familiar and related conspecifics: a first test conducted on captive Humboldt penguins (Spheniscus humboldti)

Studies of kin recognition in birds have largely focused on parent-offspring recognition using auditory or visual discrimination. Recent studies indicate that birds use odors during social and familial interactions and possibly for mate choice, suggesting olfactory cues may mediate kin recognition as well. Here, we show that Humboldt penguins (Spheniscus humboldti), a natally philopatric species with lifetime monogamy, discriminate between familiar and unfamiliar non-kin odors (using prior association) and between unfamiliar kin and non-kin odors (using phenotype matching). Penguins preferred familiar non-kin odors, which may be associated with the recognition of nest mates and colony mates and with locating burrows at night after foraging. In tests of kin recognition, penguins preferred unfamiliar non-kin odors. Penguins may have perceived non-kin odors as novel because they did not match the birds' recognition templates. Phenotype matching is likely the primary mechanism for kin recognition within the colony to avoid inbreeding. To our knowledge this is the first study to provide evidence of odor-based kin discrimination in a bird.     

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.     

Facial Recognition in a Group-Living Cichlid Fish

The theoretical underpinnings of the mechanisms of sociality, e.g. territoriality, hierarchy, and reciprocity, are based on assumptions of individual recognition. While behavioural evidence suggests individual recognition is widespread, the cues that animals use to recognise individuals are established in only a handful of systems. Here, we use digital models to demonstrate that facial features are the visual cue used for individual recognition in the social fish Neolamprologus pulcher. Focal fish were exposed to digital images showing four different combinations of familiar and unfamiliar face and body colorations. Focal fish attended to digital models with unfamiliar faces longer and from a further distance to the model than to models with familiar faces. These results strongly suggest that fish can distinguish individuals accurately using facial colour patterns. Our observations also suggest that fish are able to rapidly (≤ 0.5 sec) discriminate between familiar and unfamiliar individuals, a speed of recognition comparable to primates including humans.     

Olfactory Individual Recognition of Mothers by Young Guinea-Pigs (Cavia porcellus)

In mammals, olfactory cues play a major role in individual recognition and urine is one source of potentially individual‐specific olfactory cues. We studied how soon young of the extremely precocial domestic guinea‐pig (Cavia porcellus) establish specific preferences for maternal urine smell by offering 5–30‐d‐old young a simultaneous choice between a urine sample of the mother and urine from an unfamiliar unrelated lactating female. Young showed increasing preference for the smell of maternal urine from day 5 of life onwards. On day 10 of life, they discriminated between maternal urine and that of other lactating females when these were unfamiliar and related, unfamiliar and unrelated or familiar unrelated, but not when the urine of the other female came from a familiar and related lactating animal. The last result is based on fewer litters and, therefore has to be considered as preliminary. As our results are based on spontaneous preferences for just one source of olfactory cues, discrimination of live animals is likely to be even better than demonstrated here. Learning or phenotype matching of individual specific cues enable these precocial young to form a specific bond with their mother soon after birth.     

根田鼠的熟悉性及其自然动情下的配偶选择

报道了在室内雌鼠自然动情条件下根田鼠两性个体配偶选择的3种熟悉性效应的5组实验结果,包括雌性对熟悉和陌生雄鼠、配偶和陌生雄鼠、配偶和熟悉雄鼠的择偶行为实验 , 雄性对熟悉和陌生雌鼠、配偶和陌生雌鼠的择偶行为实验。在实验前, 将1对性成熟的雌雄鼠 (非亲缘关系) 每天关养8 h 共8 d 建立熟悉性; 配对雌雄鼠至少生育1胎则为配偶关系。在 Y 形迷宫内的30 min 实验中, 两个被选择鼠分别以项链拴在横跨选择箱顶端中央的一根铁丝上, 限制它们在各自箱内活动; 而允许异性选择鼠从中立箱自由进入两个选择箱。记录选择鼠对异性被选择鼠的访问、社会探究、攻击、交配和友好行为的频次和时间。经Wilcoxon 关联样本 T 检验发现, 除交配行为不显著外, 雌性根田鼠均选择熟悉性较高的雄鼠; 而雄鼠不具这种选择性。该结果提示雌雄根田鼠的不同择偶行为也许就是反映该种婚配制度特征的直接行为过程。因此, 在择偶行为中, 雌性根田鼠表现的单配性倾向和雄鼠的多配性倾向, 只能以其婚配制度为一雄多雌制的假设来解释。我们的实验还说明在多配制田鼠中, 一雄多雌制与混交制在雌鼠择偶行为上是不同的, 而与单配制的相似或相近, 故简单地比较多配制与单配制则不能反映田鼠亚科动物婚配制度的多样性。     

Impaired social contacts with familiar anesthetized conspecific in CA3‐restricted brain‐derived neurotrophic factor knockout mice

Familiarity is conveyed by social cues and determines behaviors toward conspecifics. Here, we characterize a novel assay for social behaviors in mice—contacts with anesthetized conspecific—which eliminates reciprocal interactions, including intermale aggression and shows behaviors that are independent of the demonstrator's activity. During the initial 10 minutes (phase‐1), the wild‐type (WT) subjects contacted the anesthetized conspecifics vigorously regardless of familiarity. During the subsequent 80 minutes (phase‐2), however, they contacted more with familiar than unfamiliar conspecifics. We then applied this test to highly aggressive mice with a hippocampal CA3‐restricted knockout (KO) of brain‐derived neurotrophic factor (BDNF), in which aggression may mask other social behaviors. The KO mice showed less preference for contacting familiar conspecifics than did WT mice during phase‐2 but no differences during phase‐1. Among nonsocial behaviors, WT mice also spent less time eating in the presence of familiar than with unfamiliar conspecifics, which was not seen in KO mice. In addition, KO mice exhibited reduced pain sensitization. Altogether, these findings suggest that CA3‐specific deletion of BDNF results in deficits in circuits that process social cues from familiar conspecifics as well as pain and may underlie empathy‐like behaviors.     

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.     

Acute and chronic exposure to ammonia and olfactory acuity for n-butanol in the pig

An associative learning method (using a food reward) was developed to measure pigs' olfactory acuity for n-butanol, a standard odourant in human olfactometry. The pig could press two operant paddles but it only received a food reward when it pressed the one over which n-butanol was released. Once each pig had reached a training criterion (10 consecutive roots on the correct paddle on each of two consecutive sessions) this method was used to assess the impact of acute and chronic exposure to an atmosphere containing approximately 40 parts per million (ppm) ammonia gas, compared to fresh air, on its ability to perceive different concentrations of n-butanol. These were presented using a staircase pattern, i.e. if the pig gained or failed to gain a food reward on two consecutive occasions the concentration was reduced or increased, respectively. Acute exposure for approximately 45min to about 40ppm ammonia had no effect (P>0.05) on the lowest detected concentration (LDC) of n-butanol in six pigs. The geometric mean LDC was 1.23 parts per trillion (ppt) in approximately 40ppm ammonia and 2.09ppt in fresh air. The LDC of three pigs increased, i.e. acuity fell, from 5.1 to 175.5ppt over 24 days of exposure to congruent with40ppm ammonia. Ammonia had no effect on one of the other pigs and the high variability in the LDC for the remaining two pigs produced no meaningful assessment of its impact. Subsequent removal to fresh air for a further 24 days led to partial recovery of acuity in one of the three pigs that had shown evidence of olfactory impairment but not in the other two. Collectively our findings suggest that chronic, but not acute, exposure to congruent with40ppm ammonia can interfere with olfactory perception in some pigs (50% of our sample) and that this loss of acuity is not necessarily reversible.     

Effect of kinship on social behaviors in Brandt's voles (<Emphasis Type="Italic">Microtus brandti</Emphasis>)

The roles of kinship in agonistic behavior and mate choice were evaluated in Brandt's voles (Microtus brandti). In chambers bedded with familiar or unfamiliar substrates, the aggressive behavior and social investigation towards adult unfamiliar same-sex siblings and non-siblings were examined, and no significant kin bias was found. Males sniffed and followed unfamiliar unrelated females significantly more than unfamiliar sibling sisters, but males did not show significant preferences in copulatory behavior and agonistic behavior. Females spent significantly more time copulating with unfamiliar unrelated males than with their unfamiliar sibling brothers, while they did not show a significant preference in social investigation between them. Our study shows that kinship might play a role in the inbreeding avoidance based on preweaning familiarity or/and phenotype matching, but the role of kinship in agonistic behavior remains unclear.     

In Ovo Olfactory Experience Influences Post‐hatch Feeding Behaviour in Young Chickens

In several mammalian species, prenatal exposure to odours can elicit later positive consummatory behaviour in response to substrates bearing that odorant. In birds, the sense of smell has been considerably underestimated, and very little is known about the effects of early sensory experience on the regulation of feeding behaviour. We tested the hypothesis that the feeding behaviour of the domestic chicken could be regulated by olfactory learning during the embryonic life. To that end, chicken embryos were exposed to an olfactory stimulus (blend of essential oil of orange and nature identical vanillin) from embryonic day (ED) 12 to ED20, and chicks were tested between 4 and 9 d of age. In short‐term choice tests, at day 4 and 5, chickens previously exposed to a low concentration (LC) of the olfactory stimulus spent a higher proportion of time eating a familiar or an unfamiliar food bearing the olfactory stimulus compared to non‐exposed control chickens. Conversely, chickens previously exposed to a high concentration (HC) of the olfactory stimulus were found to avoid all foods bearing the olfactory stimulus. On a 24‐ h time scale at day 7–8, LC and HC birds, but not controls, ingest significantly less familiar food containing the olfactory stimulus. This result indicated a long‐term effect of the early olfactory experience on feeding preferences. We demonstrated that chickens can utilize information from their pre‐hatch chemosensory environment to guide their later feeding behaviour. A pre‐hatch effect of the intensity of odour signals in the regulation of feeding behaviour is reported here for the first time.     

Prenatal and early sucking influences on dietary preference in newborn, weaning, and young adult cats

Early experiences are of potential importance in shaping long-term behavior. This study examined the relative influence of prenatal and/or early postnatal experience of chemosensory stimuli on subsequent olfactory and dietary preferences of cats as newborns, at 9-10 weeks, and at 6 months. Cats were exposed to vanillin or 4-ethylguaiacol via their mother's diet either prenatally, postnatally, perinatally (prenatal and postnatal), or experienced no exposure to the stimuli (control). Newborns were given a two-choice olfactory test between the familiar "odor" and no odor; 9-10 week olds were tested for their preference between two food treats, one flavored with the familiar stimulus and the other unflavored; at 6 months, cats were given a choice of two bowls of food, one flavored with the familiar stimulus and the other unflavored. At all ages, cats preferred the familiar, and avoided the unfamiliar, stimulus. Perinatal exposure exerted the strongest influence on preference. Prenatal exposure influenced preference at all ages and postnatal exposure exerted a stronger effect as the cat aged. We conclude that long-term chemosensory and dietary preferences of cats are influenced by prenatal and early (nursing) postnatal experience, supporting a natural and biologically relevant mechanism for the safe transmission of diet from mother to young.     

Factor of familiarity in sibling recognition in golden hamsters

Male hamsters, reared with their siblings and non-siblings, were tested for their exploratory behavior of conspecific in the 4th and 8th week after their birth. During the tests, a familiar sibling, an unfamiliar sibling, a familiar non-sibling and an unfamiliar non-siblings was presented in a choice box. Subjective distance among these testing animals was measured using the caseV of Thurston's paired-comparison test. The hamsters spent more time with the unfamiliar animals than with the familiar ones. Although biological relation (sibling or non-sibling) had a significant effect in the 4th-week test, only the familiarity determined the investigatory behavior in the 8th-week test. These results suggest sibling recognition based on learning in hamsters.     

棕色田鼠两个地域野生种群的行为比较

小型哺乳动物能够通过行为策略的进化适应周围的环境。其中,种内社会组织也可随环境参数的变化而变化。河南灵宝程村气候干燥、海拔高,而新郑则气候湿润、海拔低。来自河南灵宝程村的棕色田鼠种群和来自新郑的种群是否在社会行为、情绪、以及性二型上有所差别,目前还不清楚。本研究中,我们通过旷场实验
和熟悉选择试验比较了两个种群的情绪、运动能力以及对熟悉鼠和陌生鼠的选择。统计结果表明,程村种群的雌性个体比雄性个体重,而新郑种群的雄性体重比程村种群的重。在旷场实验中,程村种群比新郑种群表现出较多的焦虑样行为。配偶选择实验中,新郑种群不论雌雄都表现出了对陌生异性的喜好。程村种群雄性则更愿意选择熟悉的个体。而且,程村的雌性待在陌生箱攻击陌生鼠的时间远大于熟悉鼠。以上结果表明,两个野生种群在体重、情绪以及对熟悉鼠和陌生鼠选择上都表现出了明显的种群间差异。     

Social preferences in farmed silver fox females (Vulpes vulpes): Does it change with age?

Determining foxes’ social preference, and how this influences their social behaviour towards different conspecifics at different ages may give us a better understanding of how to prevent foxes from exposure of possible social stressors when housed in groups. Here, we investigated the effect of familiarity on social preferences in silver fox females and their motives for seeking social contact at two different ages. Fourteen silver fox females conducted two preference tests, first at the age of 9 weeks and the second at the age of 24 weeks, where they could choose between an empty cage, a familiar female or an unfamiliar female at their own age. The position and behaviour of the females were recorded using instantaneous sampling every tenth minute for 26 h. There was a clear preference to seek contact with a conspecific at 9 weeks of age (p < 0.01). The cubs did not differentiate between a familiar or unfamiliar stimulus animal (p > 0.05), however there was a tendency to play more in front of the unfamiliar stimulus animal (p = 0.07). No preference was seen for either the familiar, unfamiliar or empty cage stimulus when the females were 24 weeks old (p > 0.05), however they were more aggressive towards the unfamiliar stimulus animal (p < 0.01). Thus, there was no effect of familiarity in time spent with a social stimulus at either age, however these results suggest that the motives for seeking contact as cubs were non-aggressive and possibly play related, whereas the aggressive behaviour displayed by juveniles towards the unfamiliar female indicates an increased competitive motivation.     

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.