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A Comparison of Spontaneous and Odor‐induced Chin Marking in Male and Female Domestic Rabbits (Oryctolagus cuniculus domestica)
Abstract
Chin marking by the European rabbit (Oryctolagus cuniculus) is one of the classic but still little understood examples of mammalian chemical communication. To investigate whether the sexes differ in performance of this behavior, we compared the frequency of spontaneous chinning and chinning in response to the chin marks of conspecifics in 20 intact male and 20 intact female chinchilla-breed rabbits, and in five gonadectomized animals of each sex. Contrary to the expectation of greater chinning activity in males, no significant sex differences were found. Frequencies of spontaneous chinning were similar in the two sexes, large and stable individual differences were observed in both, chinning increased in both when marks from unfamiliar conspecifics were present, and both directed chin marks to objects marked by conspecifics more than to unmarked objects. Individual chinning frequencies correlated positively with urination but not defecation in both sexes, and spontaneous and odor-induced chinning were significantly reduced both in castrated and ovariectomized animals. The findings suggest that chinning is an equally significant part of the communication system of male and female rabbits and that its expression may be regulated by similar olfactory, hormonal, and social mechanisms.
... enhanced by naturally circulating levels or by the administration of these (González-Mariscal et al., 1992Hudson et al., 1990;Melo et al., 2008) and is reduced or eliminated in both sexes following gonadectomy González-Mariscal et al., 1992;Hudson et al., 1990Hudson et al., , 1994Hudson & Vodermeyer, 1992;Martínez-Gómez et al., 1997). Particularly relevant to this study, consistent individual differences have been reported in the frequency of chinning in both sexes in a range of studies (Arteaga et al., 2008;González-Mariscal et al., 1992;Hudson & Vodermeyer, 1992;Martínez-Gómez et al., 1997). ...
... enhanced by naturally circulating levels or by the administration of these (González-Mariscal et al., 1992Hudson et al., 1990;Melo et al., 2008) and is reduced or eliminated in both sexes following gonadectomy González-Mariscal et al., 1992;Hudson et al., 1990Hudson et al., , 1994Hudson & Vodermeyer, 1992;Martínez-Gómez et al., 1997). Particularly relevant to this study, consistent individual differences have been reported in the frequency of chinning in both sexes in a range of studies (Arteaga et al., 2008;González-Mariscal et al., 1992;Hudson & Vodermeyer, 1992;Martínez-Gómez et al., 1997). ...
... This dissociation between the development of individual differences in chinning frequency and other measures of early development was the case despite the results of chinning frequency corresponding well in several respects to previous studies.González-Mariscal et al. (1992) also reported the early emergence of chinning in juveniles and obtained similar values for males and females at sexual maturity. Large and stable individual differences in adults were also found byArteaga et al. (2008),González-Mariscal et al. (1990),Hudson and Vodermeyer (1992), andMartínez-Gómez et al. (1997). ...
Individual differences in behavior (“personality”) are of considerable interest to behavioral biologists. Important questions include how early in life such differences emerge, what factors influence their emergence, and whether they remain stable across development and into adult life. Given the demanding nature of longitudinal studies, there is a lack of information regarding these questions in mammals. Our aim in this study was to investigate the development of individual differences in chin‐marking behavior (chinning) in the domestic rabbit, a notable part of this species’ system of chemical communication, and to relate this to individual differences in growth and behavior among littermates during the early postnatal period. We tested repeatedly the frequency of chinning movements from weaning to sexual maturity in 63 chinchilla‐strain rabbits (35 females, 28 males) from 14 litters. Within litters, we found significant consistencies over time in this behavior, that is, in both sexes inter‐individual differences among litter siblings in the frequency of chinning movements remained stable across the postweaning period until sexual maturity. Unexpectedly, however, we found no significant associations with the morphological, physiological, or behavioral variables known to form a well‐correlated early developmental complex in this species. We tentatively conclude that in the rabbit, individual differences in the frequency of chinning have little relation to other previously studied aspects of individual developmental trajectories. The origin and functional significance of individual differences in chinning frequency, whether in reproductive or other social contexts is largely unknown and requires further investigation. In this study, we investigate the development of individual differences in chin‐marking behavior (chinning) in the domestic rabbit and relate this to individual differences in growth and behavior among littermates during the early postnatal period. Individual differences among litter siblings in the frequency of chinning remained stable across the postweaning period until sexual maturity. However, we found no significant associations between individual differences in chinning and individual differences in the morphological, physiological, or behavioral variables known to form a well‐correlated early developmental complex in this species.
... Thus, within natural social groups, the frequency of chinning was often acutely increased in the aggressor of an aggressive chase between two males [2]. Both male and female rabbits of the chinchilla strain were observed to preferentially chin-mark objects that had been previously marked by unfamiliar conspecifics compared to objects having the individual's own chin-marks [17,20]. In order to further investigate the acute modulation of this stereotyped behavior, in the present study we first characterized the expression of chinning and ambulation across a 90 min observation period while the rabbit explored an open field arena containing markable objects, and found that both chinning and ambulation were initially stimulated, then gradually decreased ( " habituated " ), across the first 30 min. ...
... Indeed, the results of other studies indicate that olfactory characteristics of objects can modulate the expression of this behavior. Thus, chinning in male and female rabbits of the chinchilla strain increased in response to bricks previously chin-marked by another individual (male or female), and these bricks were marked preferentially when they were presented together with bricks having the rabbit's own marks [17,20]. These results indicate that the rabbit can distinguish between its own marks and those made by another individual, and can respond by " over-marking " or " counter-marking " the other individual's marks. ...
... Similarly, in nature, dominant male rabbits scent mark more than subordinate ones [1] , and in controlled laboratory conditions a male rabbit is more likely to dominate in its social interaction with another male if the test enclosure in which the interaction takes place contains his own scent gland secretions [26]. Methodological differences between the previous studies in the rabbit [i.e., 17, 20] and the present one, such as the strain of rabbit used (chinchilla in the previous ones, and New Zealand white in the present study), could account for the observed differences in sensitivity of the chinning response to olfactory stimuli. In contrast to those previous studies, the present study used a habituation–dishabituation paradigm that was carried out during a single extended test period lasting 1 h. ...
"Chinning" is a stereotyped scent marking behavior of domestic rabbits, in which the animal rubs the underside of its chin against objects in order to deposit scent gland secretions. Although the long-term maintenance of chinning requires circulating gonadal steroids, little is known about the acute regulation of this behavior. To define specific environmental stimuli that engage the chinning motor pattern, male rabbits were placed into an open field arena containing markable objects ("standard" bricks, "tall" bricks, or polished onyx spheres), observed for 30 min, returned to the home cage for 5 min, and then placed in the open field arena for another 30 min. During the 5 min interim: (1) the location of the open field or the spatial orientation of the objects within it were changed, (2) the olfactory or (3) visual characteristics of the objects were changed; or (4) no changes were made. Chinning and ambulation habituated to each type of object across the first 30 min, and bricks elicited more chinning than polished onyx spheres. In the second 30 min test, chinning was re-stimulated only when the original objects were replaced by visually different ones that had preferred characteristics. Ambulatory behavior was increased by changing the location of the open field arena, while modifying the olfactory characteristics of the objects had no effect on chinning or ambulation. These results indicate that scent marking is stimulated by object novelty and by the visual and/or tactile characteristics of the objects being marked.
... Flehmen in male horses is involved in the monitoring of the estrous cycle of mares (Stahlbaum and Houpt, 1989). Interestingly, in this respect, males can discriminate among particular females independently of their reproductive status (Marinier et al., 1988). On the other hand, males may also display flehmen in response to the urine of other males, or even to their own urine (Guillaume et al., 2018), suggesting a nonreproductive function of this behavior. ...
... Another phenomenon that remains to be explored is the response of the mother and the stallion to the odor of their foal and of other foals. Importantly, future studies will face the challenge of designing methods that allow convenient manipulation of the chemical stimuli used, including the presentation, change, and removal of odorant cues, as has been performed in other species, including rabbits (González-Mariscal et al., 1990;Martínez-Gómez et al., 1997;Hudson et al., 2008), cats (Raihani et al., 2009;Arteaga et al., 2013), and mice (Beynon and Hurst, 2004). ...
This work provides an overview of the role of chemical communication in horse behavior, and addresses the potential usefulness of this knowledge for management practices and animal welfare. First, we present an outline of the social organization of horses under natural conditions, and the problems that may emerge due to domestication. Second, we briefly describe the mammalian olfactory system, noting the peculiarities of horses. Third, we describe some behaviors in which horses use chemical communication, including sexual behavior, and mother-young relationship. Finally, the article focuses on the gaps in information on the chemical communication of the horse, and the underexplored possible advantages of using chemical signals to reduce the stress response of foals and horses in the context of domestication.
... In rabbits, serum levels of T are positively correlated with postnatal growth (Hudson et al., 2011) and are positively associated with agonistic behavior and social dominance in adults (von Holst, 1998). Dominance, in turn, is positively correlated with chin gland size and chin-marking activity (Arteaga et al., 2008;Black-Cleworth and Verberne, 1975;Farabollini, 1987;Girolami et al., 1998;Mykytowycz, 1965), and administration of T increases chin-marking in males whereas castration reduces or eliminates it (Briganti et al., 2003;Chirino et al., 1993;González-Mariscal et al., 1993;Martínez-Gómez et al., 1997). ...
It is well established that in mammals prenatal exposure to exogenous testosterone has a masculinizing effect on female morphology and behavior. Fewer studies, however, have been conducted in males on this subject, and the results are controversial. In the present study we investigated the long-term effect of administering extra prenatal testosterone (testosterone proprionate; TP) on adult male domestic rabbits' morphology and behavior using two different control groups, non-treated and vehicle injected mothers. Unexpectedly, administering the vehicle alone had a clear under-masculinizing effect on all morphological and behavioral measures; lower body mass, smaller anogenital distance and smaller chin glands, lower chin-marking activity and greater timidity. Administration of TP counteracted this effect in a dose-dependent manner such that animals exposed to the highest dose prenatally showed values on the morphological and behavioral measures equivalent to but not greater than the non-treated control group. We conclude 1) that additional testosterone beyond what male fetuses produce in utero does not result in increased masculinization, and thus that male fetuses are less susceptible prenatally to hormonal effects than females, and 2) that presumably stress-related effects of administering the vehicle alone resulted in under-masculinization, which could be recovered by the prenatal administration of TP. These results may partly account for the contradictory findings of previous studies, and indicate the importance of including both non-treated and sham- (vehicle) treated controls in future experiments.
Copyright © 2015. Published by Elsevier B.V.
... Hudson and Vodermayer [76] also found that does marked bricks more frequently if they had been marked by a buck before. In contrast, Martinez-Gomez et al. [77] found both male and female rabbits preferentially chin-mark objects having been marked by an unfamiliar rabbit regardless of its sex. Although the functional significance of over-marking is unclear, it may have a role in establishing and maintaining group identity, territory, and/or the individual's dominancy. ...
In the case of some mammalian species, females with larger anogenital distance (AGD) have smaller litters, where the sex ratio is male-biased. The first aim of the present study was to test whether this phenomenon exists in the Lagomorph group, especially in rabbits. The results revealed that does with large AGD have significantly smaller and lighter litters with a male biased sex ratio; with fewer females but not more males. The second aim of the present study was to test whether males differentiate between females differing in their AGD and are thus capable of choosing the more fertile and fecund does. Males showed a stronger response to the chin marks of females with small AGD than to the marks of females with large AGD. Our results suggest that variation in the prenatal hormonal environment, reflected through variation in AGD, could have long-term consequences on mate choice and population dynamics.
Background
Despite the importance of the rabbit (Oryctolagus cuniculus) in reproductive research, no comprehensive account of the anatomical organization of the female reproductive tract is presently available.Methods
Based on gross dissection and on the electrical stimulation of striated muscles in 10 domestic female rabbits, it was the aim of this study to help fill this gap by describing the origin, insertion, and general action of muscles associated with the vaginal tract and with associated scent glands.ResultsCompared with the better-studied rat or cat, the long vaginal tract of the rabbit is characterized by a well-developed and complex musculature. The bulbospongiosus, ischiocavernosus, constrictor vestibuli, and constrictor vulvae muscles, poorly developed or absent in the female rat or cat, were particularly conspicuous. Scent glands, including the newly identified preputial glands, were also a distinctive feature.Conclusion
These structures may represent specializations underlying the rapid copulation, rapid parturition, and well-developed chemical communication characteristic of the reproductive efficiency of the rabbit. Anat. Rec. 247:486–495, 1997. © 1997 Wiley-Liss, Inc.
Tasa de ingestión y conducta alimenticia de reproductores de L. vannamei: Efecto de atractantes/estimulantes alimenticios sintéticos en dietas La presente investigación evaluó en un primer experimento mediante el empleo de discos de agar (30 mm de diámetro) el potencial atractante de varias moléculas sintéticas como son taurina, betaína, ácido glutámico, glicina y sus mezclas binarias frente a un extracto de calamar y al agua destilada como controles positivo (CP) y negativo (CN), respectivamente.
The European rabbit, both in its wild and domesticated forms, has been a pioneer species in the study of mammalian chemical communication, and illustrates well the difficulty of understanding the functional significance of these often complex signals. Here we investigate the performance of one of the rabbit's most conspicuous chemical signaling behaviors, chin marking (chinning), and the hypothesis that this expresses social dominance. In tests of 21 chinchilla-strain sexually mature males we predicted 1) that animals would show marked and stable individual differences in the frequency of chinning, 2) that these differences would correlate with behaviors associated with dominance such as intrasexual mounting, and 3) that individual differences in the frequency of chinning and dominance-related behaviors would correlate with individual differences in a commonly used physiological indicator of dominance, concentration of serum testosterone. Supporting these predictions and consistent with previous reports, animals showed large and stable individual differences in the frequency of chinning which correlated with the behavioral indicators of dominance and less strongly, with serum testosterone. As our animals had been kept in single cages and without direct contact with other males since weaning, these findings raise the question as to how and when during development such differences among individuals arise. We are currently investigating the possible relation between pups' intrauterine position, postnatal competition among littermates for milk and thermally advantageous positions in the litter huddle, and later differences in indicators of dominance such as those reported here.
It was the purpose of this study to test whether inhibition of estrus in the rabbit by short photoperiod could be simulated by subcutaneous implants of the pineal hormone melatonin. By measuring two non-invasive and readily quantifiable correlates of estrus, emission of the so-called nipple-search pheromone and scent-marking behavior (chinning), it was found that:1.
In intact does kept in stimulatory long photoperiod, melatonin suppressed chinning but had no effect on emission of nipple-search pheromone.
2.
In intact, melatonin-treated does which were returned from inhibitory short day to stimulatory long day, chinning remained suppressed, whereas pheromone emission increased as for the vehicle-treated, control does.
3.
In ovariectomized does, estradiol administration stimulated both pheromone emission and chinning whereas melatonin failed to suppress these effects.
Thus, although the administration of melatonin had an inhibitory effect on chinning it failed to suppress emission of the nipple-search pheromone and therefore failed to fully simulate the effect of short photoperiod on these two correlates of estrus. Several explanations for this discrepancy are considered, including the possibility that melatonin is not the sole mediary of the photoperiodic response, and that at least in female rabbits, other pineal products may also play a significant role.
Chin-marking behavior (chinning) was evaluated daily in nine intact adult male rabbits. All subjects (Ss) displayed chinning (mean of means +/- SE = 61 +/- 7 marks/10 min) but the frequency of this behavior varied largely across them (range of mean chinning frequency = 19-84 marks/10 min). Chinning frequency showed abrupt variations at intervals of 2-3 days, but periodogram analysis did not reveal the existence of an endogenous rhythm in this behavior. Castration significantly decreased (mean of means +/- SE = 29 +/- 9 marks/10 min; p < 0.01). but did not suppress chinning. Testosterone propionate (TP; 1 mg/day for 16 days) restored chinning in castrated Ss to slightly below precastration levels (mean +/- S.E. V 53 +/- 13 marks/10 min). The daily administration of 1 microgram estradiol benzoate (EB) plus 1 mg dihydrotestosterone propionate (DHTP) stimulated chinning within 2 days (mean increase = 147%; p < 0.005). DHTP (1 mg/day) given alone stimulated chinning only after 11 days of treatment (mean increase = 475%; p < 0.01). At higher doses, both DHTP (10 mg/day) and EB (10 or 50 micrograms/day) stimulated chinning by 450%, 80%, and 100%, respectively, over baseline values. Results indicate that chinning largely depends on testicular steroids. Androgen receptor occupation by T or DHT, which is enhanced by E, optimally activates chinning.
Sex differences and the effect of various endocrine conditions on the histology of the rabbit (Oryctolagus cuniculus L.) submandibular (chin) gland were investigated. The female gland contained significantly more acini/field than the male gland. The diameter of acini was significantly smaller than those of the male gland. Gonadectomy reduced the number of acini/field and increased their diameter in females but provoked the opposite effect in males. Gonadectomy drastically reduced the percent of acini with crystal bodies in both sexes, and the percent of acini with apocrine secretion only in females. Estrous does showed a significantly higher number of acini/field than pregnant (days 20 and 29) and lactating (day 6) does. Acini containing crystal bodies declined from 22% in estrous females to 8% and 3% in pre-parturient (gestation day 31) and lactating (day 6) does, respectively. By contrast, acini showing apocrine secretion increased from 12% in estrous females to 43% in pre-parturient does and declined to 23% on lactation day 6. In all glands glycoproteins were noted in crystal bodies but not in apocrine secretion. Results show a sexual dimorphism in the rabbit chin gland histology and support the participation of gonadal steroids in its physiological regulation.
For the Australian wild rabbit, Oryctolagus cuniculus (L.), in experimental
enclosures, the weights of submandibular, anal, inguinal, Harder's, lachrymal, and
thyroid glands were analysed statistically in relation to density of population, sex,
sexual activity, social status, and weight of the rabbits.
A statistically significant correlation between the sexual activity of males and
the weight of their anal, iguinal, and submandibular glands was demonstrated. The
same correlation could not be demonstrated for Harder's and thyroid glands. There
were no differences in gland weights in females between populations of different
densities, but in males the inguinal and submandibular glands were significantly heavier
in low-density populations.
A highly significant linear relationship between social status of male rabbits and
the weight of their anal and inguinal glands was found. There was a less significant
relationship in the case of Harder's and thyroid glands and none in the lachrymal.
A linear relationship was not demonstrated for the submandibular gland but there was a
difference between the dominant males and the rest. In females the weights of anal and
inguinal glands were very significantly correlated with the social status of individuals.
In the case of all other glands there was no correlation with social status. Social status
was significantly correlated with body weight in males but not in females.
There were statistically significant differences in the weights of the inguinal,
thyroid, and lachrymal glands of males from enclosures with different densities of
populations.
The results suggest the importance of odoriferous glands in the social and
territorial activities of the wild rabbit.
Chin marking(chinning) frequency was determined daily in 25 male and 24 female New Zealand rabbits aged 31–150 days. Chinning appeared earlier in females (mean ± SD = 41 ± 16 days) than in males (47 ± 13 days). Between days 30–50, females displayed chinning more frequently than males. Thereafter, chinning increased steadily in both sexes up to day 100. Chinning curves levelled on days 100 and 140 in males and females, respectively. Profile analysis of male and female chinning curves showed significant differences in their slopes and in their population means (p < 0.001). At 7 months of age (days 210–224), both sexes displayed adult chinning frequencies: mean of means ± SD = 103 ± 18 and 79 ± 14 marks/10 min in males (n = 8) and females (n = 8), respectively. The administration of testosterone propionate (TP, 1 mg/day) or estradiol benzoate (EB, 1 μg/day) to males and females, respectively, from days 31–50, stimulated higher chinning frequencies than those displayed by untreated animals. Results suggest that chinning frequency increases throughout development largely as a consequence of a concomitant increase in sex steroid secretion.
Embryological, histological, and histochemical features of the chin glands in the rabbit, Oryctolagus cuniculus (L.), are described. The glands are modified sweat glands which develop as appendages of the first hair follicles of the pelage. All the secretory cells are of the merocrine type, although some secrete in the typical apocrine manner. In the adult, the glands are much better developed in males than in females. Two main types of secretory cells were clearly seen in most animals, particularly adult males. Cells which stained heavily with osmium tetroxide (dark cells) were also present. No other mammalian cutaneous gland is so complex. Histochemical techniques to demonstrate enzymes revealed that particular glandular components contained large amounts of alkaline phosphatase and the whole gland was well supplied with nerves containing cholinesterases. The function of the secretion from these glands in marking territories is outlined.
The olfactory exploratory and scent-marking behavior of domestic rabbits were observed in an artificial laboratory enclosure. The rabbits tended to mark certain objects more frequently than others with their chin gland secretion (chinning), apparently guided by visual characteristics; however, they preferred to sniff and chin objects which had been chinned previously over those that had never been chinned. They chinned more frequently when faecal pellets were present. Dominant male rabbits chinned objects more frequently, and subordinate male rabbits less frequently, in a freshly marked environment than in a clean one; similarly dominant males chinned more frequently and subordinates less frequently when urine from another rabbit was present. Rabbits preferentially chinned urine and faecal pellets from other rabbits over their own.
The dominance relations of the rabbits were determined by analyzing the behavior patterns correlated with chasing and fleeing. One of the most characteristic features of encounters between two rabbits was a complete sexual display.
Long periods of sniffing of certain substances, usually urine, by the rabbits were analyzed and found to be basically similar to sniffing and flehmen patterns shown by cats. The data support the hypothesis that the whole flehmen pattern including licking and headshaking is involved with transporting substances in solution to the vomeronasal organ.
Differences in frequency and duration of sniffing and chinning reactions make it feasible that male domestic rabbits are able to discriminate between objects with and without secretion of the submandibular cutaneous chin gland. They also react differently to their own chin gland secretion as compared with that of other males.
Rabbits discriminate clearly between faecal pellets and placebos, own and strange pellets, and fresh and old ones. Pellets produced in the individual home cages appear to be less interesting than those put down in a room simulating a group territory. Reactions to own, strange, old and fresh urine indicate a function in the olfactory communication for urine as well.
Higher values of frequencies for sniffing and chinning pheromone carriers appeared to be due to more repetitions of these alternating behaviours within an encounter with a scent carrier rather than to more returns to it.
Qualitatively different sniffing behaviour with respect to pheromones was also found.
INVESTIGATION of wild rabbits confined in experimental enclosures of approximately 2 acres at Gungahlin, near Canberra, and at Albury has established the existence of discrete social groups, each with its own territory and dominance hierarchy4,5. In the enclosure at Gungahlin, rabbits have been observed to mark objects in their territories with the secretion of the chin gland, as well as with urine and fæces. Features such as the edges of posts, tips of grass blades and branches, edges of burrow entrances, walls and ceilings of cages, and even kittens and does during amatory behaviour, are subjected to `chinning' during which they are smeared with small amounts of secretion.
By using the response of newborn pups to test for the presence of nipple-search pheromone on female rabbits, it could be shown that:1.
In non-breeding does pheromone emission follows a seasonal cycle with the peak in early summer, and this appears to be dependent on daylength.
2.
At all times of year the probability of pheromone being present increases during pregnancy and decreases again during late lactation or following early removal of pups.
3.
Pheromone emission is depressed following ovariectomy but can be stimulated by administration of estradiol.
Chin-marking (chinning) was measured daily in intact New Zealand female rabbits across their whole reproductive cycle. In Experiment 1 does displayed during estrus (48 days studied) three phases, adaptation, growth and plateau, characterized by progressively higher chinning scores (mean±SE=3.6±1.1; 17.7±6.3; 26.6±4.9 marks/10 min, respectively). Despite great quantitative differences among individuals, these 3 phases and the occurrence of chinning “peaks” at 4–6 day intervals were consistently observed in all subjects (Ss). Mating provoked, within one hour, a dramatic decrease in chinning. Both pregnant and pseudopregnant Ss showed low chinning scores for the first 13 days after mating (combined mean±SE=7.3±3.8 marks/10 min). From days 14 to 30 postcoitus chinning gradually rose in the pseudopregnant Ss (mean±SE=12.7±5.4 marks/10 min) while remaining low in the pregnant ones (mean±SE=2.6±1.9 marks/10 min). Parturition allowed a gradual rise in chinning scores. In Experiment 2 the same Ss were explored across a second reproductive cycle that included lactation. In contrast to Experiment 1, no significant variations in chinning were displayed along estrus, Ss showing high chinning scores already on the first day of observation (mean±SE from 12 days=19.2±6.7 marks/10 min). In agreement with Experiment 1, mating drastically reduced chinning scores. Low levels were maintained throughout pregnancy (mean±SE=3.4±2.4 marks/10 min) and lactation (mean±SE=3.3±4.8 marks/10 min). Weaning allowed a gradual increase in chinning scores. The chinning pattern observed across two reproductive cycles closely parallels the sexual receptivity reported to occur in female rabbits under similar reproductive conditions. This coincidence allows us to propose that chin-marking may be a normal component of estrus and that its frequency may be used to assess the reproductive condition of female rabbits.
Behavioural reactions to unfamiliar conspecifics of both sexes were studied in female domestic rabbits, living in stable unisexual groups. Intrusion caused an abrupt increase in the frequency of social investigation and agonistic behaviours directed to both intruders and group-mates. Reactions depended on the rank of resident females and the sex of the intruder, and were generally more marked in the presence of the male than the female intruder. Dominant and sub-dominant females investigated the male more than the female intruder; the opposite held for subordinate females. In the presence of the female intruder, only dominant and subdominant females were aggressive towards the intruder and group-mates. In the presence of the male intruder, aggression was directed to the intruder and group-mates by dominant females only. They tended to frequently attack sub-dominants, which in turn fled away from them more often than they did from other group-mates.
The effect of daily injections of estradiol benzoate (1 or 10 μg) and of progesterone (10 mg) on chin marking activity, sexual receptivity, and emission of nipple-search pheromone in ovariectomized rabbits was investigated. Both estradiol treatments resulted in a significant increase in all three measures over baseline and control group levels within 1–3 days, and withdrawal in a return to pretreatment levels within 2 weeks (Experiment I). In contrast, the administration of progesterone to such estradiol-primed does resulted in an almost immediate suppression of chin marking and lordosis, but in marked enhancement of pheromone emission and aggressive behavior (Experiment II). However, progesterone given alone to nonprimed does had no effect on any of these measures (Experiment III). The response profiles resulting from these treatments correspond well to patterns reported for intact does during estrus (= estradiol alone), pregnancy (= estradiol plus progesterone), and at parturition (= progesterone withdrawal).
In the European rabbit, Oryctolagus cuniculus, chin marking is one of the most conspicuous forms of olfactory communication. In an investigation of factors influencing the expression of this behaviour in females, the marking frequency of seven intact and three ovariectomized does was tested over a 12-month period by placing them individually for 10 min each day in an arena containing three bricks. In the intact does but not in the ovariectomized ones, the frequency of chinning was increased by experimental long days and suppressed by experimental short days within 1–2 weeks of reversing the light regime. These changes were accompanied by clear alterations in the size and colour of the vulva, indicating that oestrus was also suppressed under the short-day conditions. However, presenting does with bricks marked by donor animals resulted in a significant increase in the frequency of chinning independent of photoperiod. Moreover, does appeared to distinguish between donors, directing marks preferentially to bricks marked by males rather than females, bricks marked by long-day rather than short-day donors, and those marked with chin gland secretion rather than with donors' urine or with carrot or lemon juice. Thus, while the finding that chinning activity was positively correlated with oestrus is consistent with the hypothesis that in females this behaviour is a form of sexual advertisement, the differential response shown to the chin marks of individual donors, even by non-oestrous does, suggests other, non-sexual functions for the chemosignals in chin gland secretion.
Chin marking (chinning) frequency was determined daily in 25 male and 24 female New Zealand rabbits aged 31-150 days. Chinning appeared earlier in females (mean +/- SD = 41 +/- 16 days) than in males (47 +/- 13 days). Between days 30-50, females displayed chinning more frequently than males. Thereafter, chinning increased steadily in both sexes up to day 100. Chinning curves levelled on days 100 and 140 in males and females, respectively. Profile analysis of male and female chinning curves showed significant differences in their slopes and in their population means (p < 0.001). At 7 months of age (days 210-224), both sexes displayed adult chinning frequencies: mean of means +/- SD = 103 +/- 18 and 79 +/- 14 marks/10 min in males (n = 8) and females (n = 8), respectively. The administration of testosterone propionate (TP, 1 mg/day) or estradiol benzoate (EB, 1 microgram/day) to males and females, respectively, from days 31-50, stimulated higher chinning frequencies than those displayed by untreated animals. Results suggest that chinning frequency increases throughout development largely as a consequence of a concomitant increase in sex steroid secretion.
Newborn rabbits are completely dependent on a pheromone on the mother's belly for the release of nipple-search behaviour and suckling. Using the stereotyped behavioural response of the pups as a bioassay it could be shown that: 1. In non-breeding does pheromone emission is stimulated by experimental long day and suppressed by experimental short day conditions within 1 to 2 weeks of reversing the light regime. 2. Under constant long day conditions pheromone emission, readiness to mate, conception rate and litter size remain high with no evidence of endogenous seasonal rhythmicity. 3. Experimental changes in daylength of just 1 or 2 h in either direction are sufficient to induce marked alterations in the level of pheromone emission, number of successful matings and average litter size within 2 to 3 weeks. Pheromone emission would thus seem to provide a sensitive test of photoperiodic responsiveness in non-breeding female rabbits, and a convenient, non-invasive indicator of their reproductive state.
The observation that high ranking male rhesus monkeys (Macaca mulatta) mate more frequently than low ranking monkeys in a social group is based on the assumption that all males are equally visible to the human observer. The frequency of mating activity in free ranging social bands of rhesus monkeys in the La Parguera, Puerto Rico colony, when corrected for the observability of males, revealed no significant differences in the performance of sexual behaviour by males of differing social ranks. These results fail to support the conclusion that high ranking male monkeys engage in a disproportionately higher number of sexual acts in a social group.
The rabbit has specialized apocrine glands in the submandibular (chin), inguinal and anal regions. The glands enlarge at puberty and are heavier and more active in mature males than females. Prepubertal castration causes the adult male to have lighter and less active glands than intact mature animals; this effect can be reversed by administration of testosterone (0·6 mg/24 h).
Severe reduction in gland weight and activity below the level of the castrated animals was produced by administration of oestradiol (10–20 μg/24 h) either when given alone to intact males or together with testosterone to castrated males. The degree of depression by oestradiol varied between the three glandular regions.
Progesterone (0·6 mg/24 h) was unable to stimulate the glands of castrated male rabbits but did modify the suppressive action of exogenous oestradiol.
The sebaceous glands of the inguinal complex showed the same fluctuations in weight with hormone treatment as did the inguinal apocrine glands.
Chinning—the deposition of secretion of the submandibular glands—is described and its role in the territorial marking of the free living Australian wild rabbits, Oryctolagus cuniculus (L.), is emphasized.The frequency of chinning and the weight and histology of the submandibular glands of a large number of free-living wild rabbits and of domestic rabbits have been studied experimentally. A small number of chin glands from hares, Lepus europaeus P. have been studied for comparative purposes.The chin glands are larger in males than in females. Sexual dimorphism appears when sexual maturity occurs. Males chin more frequently than females. The size of the gland and the frequency of chinning are correlated with social status. The glands seemed to be largest and most active during the breeding season. Castration during early life inhibited both the development of the glands and chinning in male rabbits, but in castrated females the size of the gland actually increased as compared with non-castrated animals.Histological changes connected with the secretion were studied in rabbits of different ages, of different social status, of known frequency of chinning, in castrated animals, and during the breeding and non-breeding seasons. Vacuolated secretory cells were found to be associated with heavy secretion. They were not seen in immature animals or those which did not chin frequently. In some heavily secreting animals they formed the entire glandular tissue. The vacuolated cells seemed to be secretory cells in a state of intense secretion. Dark cells were more common in males.Chin glands in hares were much smaller than those in rabbits. The vacuolated type of cells was not seen in hares.
Effect of removing the chin gland on chin-marking behavior in male rabbits of the New Zealand race
- R. Chirino
- G. González-Mariscai
- P. Carillo
- P. Pacheco
- R. Hudson
Methodology employed in the studies of odour signals in wild rabbits, Oryctolagus cuniculus
- R. Mykytowycz
- B. S. Goodrich
- E. R. Hesterman
Chemical Signals in Vertebrates VII
- R. Hudson
- H. Distel
Advances in Chemoreception. 1. Communication by Chemical Senses
- R. Mykytowycz
Effect of removing the chin gland on chin-marking behavior in male rabbits of the New Zealand race
- Chirino
Methodology employed in the studies of odour signals in wild rabbits, Oryctolagus cuniculus
- Mykytowycz