Misidentification by wild rabbits,Oryctolagus cuniculus,of group members carrying the odor of foreign inguinal gland secretion

The results of experiments designed to clarify the behavioral function of the odor of the secretion from the inguinal glands of rabbits,Oryctolagus cuniculus, are presented. Members of groups of female rabbits were smeared with odoriferous materials, and the behavior of their penmates towards them was recorded. Eight sources of natural rabbit odors and a commercial perfume were used in 180 tests involving 120 adult female wild-type rabbits. A high proportion of the animals smeared with the inguinal gland secretions from unfamiliar females were attacked by their pen-mates. In contrast, treatment with inguinal gland secretions from unfamiliar male rabbits; macerated inguinal gland materials from unfamiliar males and females, respectively; urine from unfamiliar females; and macerated anal gland material from unfamiliar females resulted in only minor disruption to the normal social relationships between the group members which was not significantly different to that caused by treatment with a commercial perfume.     

Misidentification by wild rabbits,Oryctolagus cuniculus,of group members carrying the odor of foreign inguinal gland secretion

The experiments described in this paper are part of a series designed to clarify the behavioral function of the odor of the secretion from the inguinal glands of rabbits,Oryctolagus cuniculus. Results are presented of tests carried out on 48 mixed-sex groups consisting of 162 adult wild-type rabbits, 48 males and 114 females. The subordinate females of the groups were smeared with various odorous materials and the reactions of their pen-mates towards them recorded. Eight sources of natural rabbit odors and a commercial perfume were used in 198 tests. A high proportion (60%) of the subordinate females smeared with the inguinal gland secretions from unfamiliar males were attacked, mainly by the males, which were generally the most dominant individuals within the groups. The paper also presents statistical analyses of behavioral data collected during two earlier related experiments with single-sex groups involving 258 rabbits in 300 tests which have not previously been evaluated. The results throughout the whole study indicate clearly that the odor of the inguinal gland secretion of rabbits carries information which affects the acceptance of individuals by their companions in organized groups. Other sources of unfamiliar rabbit odor did not influence the attitude of groupmates toward the individuals smeared with them, or if they did, their effects were only marginal.     

A comparison of the effectiveness of the odors of rabbits,Oryctolagus cuniculus,in enhancing territorial confidence

In 14 series, each of 100 tests, involving 350 individual animals it has been shown that odors derived from the anal, inguinal and chin glands and urine strengthen to different degrees the confidence of European wild rabbits,Oryctolagus cuniculus. In the tests, two rabbits were put together on otherwise neutral ground previously treated with the odor from one of the contestants. The confidence of the rabbits was determined from an assessment of the record of the time to first physical contact, the frequencies of approaches and aggression, the number of attempts to escape, and also by making a subjective assessment of their general deportment. The results confirm earlier conclusions on the territorial functions of the anal and chin glands, the role of inguinal glands in individual identification, and the behavioral role of urine. On otherwise neutral ground the rabbits' own chin secretions were found to be the most effective in stimulating the confidence of males and that of their female partners. The odor of the anal gland secretions of males stimulated a similar but slightly weaker effect. The anal gland secretions of females influenced their own confidence but not that of males. Urine seemed to play a more important role in affecting the confidence of females than of males. Inguinal gland secretions had least effect. Odor from this source generally did not influence the confidence of the experimental animals; secretion from the inguinal glands of males had a slight effect on the behavior of their female partners.     

Microflora and volatile fatty acids present in inguinal pouches of the wild rabbit,Oryctolagus cuniculus,in Australia

Contents of inguinal pouches of the wild rabbit,Oryctolagus cuniculus, have been examined for the presence of microorganisms and volatile fatty acids. A total of 245 isolates were made from 167 samples taken from 75 rabbits, and microorganisms were obtained from 93% of individuals. The most common microorganism encountered wasStaphylococcus aureus, followed by the yeastCandida kruzei. Other organisms isolated wereBacillus subtilis,Escherichia coli, andStreptococcus faecalis. Quantitative analysis of volatile fatty acids in scrapings from pouches showed considerable variation between individuals. Of the acids identified, acetic acid and isovaleric acid were the most abundant. In a liquid medium containing one of these acids, the growth of microorganisms was only slightly affected. However, growth became inhibited when these fatty acids were used in combination.     

Behavioral and cardiac responses of the rabbit,Oryctolagus cuniculus,to chemical fractions from anal gland

Unrestrained rabbits, 2–3 months old and nestlings, were exposed to the odors of the acid-neutral, acid, neutral, and basic fractions of the anal gland of male rabbits. The acid-neutral, acid, and neutral fractions elicited the strongest response in the form of avoidance. The heart rates of the nestlings were monitored using a radio telemetry technique. Statistically significant lowering of the heart rate and an increase in variability occurred on exposure to the fractions. The extent of the changes varied consistently in relation to a given odor, being greatest for the acid and neutral fractions. The results indicate the usefulness of heart-rate monitoring as a tool in the study of the perception of odors by animals.     

Identification of behaviorally significant volatile compounds in the anal gland of the rabbit,Oryctolagus cuniculus

An investigation of the anal gland volatiles of the male wild rabbitOryctolagus cuniculus has been made in which the heart rate of adult male rabbits, positioned to sniff the effluent from a gas chromatographie capillary column, has been employed as an indicator for the presence of constituents of likely behavioral significance. The examination by this means of the headspace volatiles of homogenized anal glands using gas chromatography and gas chromatography—mass spectrometry has implicated a number of saturated and monounsaturated normal and methyl-branched aldehydes in the C₉–C₁₂ range.     

To fix or not to fix: the role of 2-phenoxyethanol in rabbit,Oryctolagus cuniculus,chin gland secretion

The European rabbit (Oryctolagus cuniculus) uses the secretion of the chin gland to maintain dominance hierarchies in the wild. Recent work has investigated changes in the secretion when social status is manipulated in the rabbit. When a rabbit becomes dominant, a new compound appears in his secretion, 2-phenoxyethanol. This compound is used as a fixative in the perfume industry. This study investigates whether the compound performs a similar function in the secretion of the rabbit. 2-Phenoxyethanol is not detected olfactorially by rabbits, and slows the release rate of some of the compounds that occur naturally in rabbit chin gland secretion. We suggest that when a rabbit becomes dominant, he adds a fixative to his secretion so that his scent will persist in the environment and not dissipate. He will thus come to dominate the olfactory environment, in much the same way as he does the physical environment.     

Effect of odor derived from lion faeces on behavior of wild rabbits

A synthetic repellent derived from lion feces was tested in both pen and field bioassay trials. The chemical suppressed the feeding of rabbits on carrots for approximately one month. The application of the chemical to rabbit burrows under field conditions showed that it decreased rabbit numbers in the treated warrens and that this effect could still be detected after five months. It is suggested that this chemical could be a timely environmentally acceptable addition to the armamentarium of control measures required to reduce the recent increase in rabbit numbers occurring in Britain.     

Identification of some volatile compounds in the odor of fecal pellets of the rabbit,Oryctolagus cuniculus

A study has been made of the volatile constituents in the vapors collected from fecal pellets of wild rabbits,Oryctolagus cuniculus. Measurements of changes in the heart rates of adult male rabbits exposed to the effluent of a gas chromatographic capillary column were used to indicate the presence of compounds which may be of behavioral significance. Combined with the use of high-resolution columns in gas chromatography and gas chromatography-mass spectrometry, this approach has implicated several classes of compounds, including volatile fatty acids and phenols, which in certain absolute or relative concentrations may be involved in the formation of signals of territorial importance.     

Effect of volatiles collected above fecal pellets on behavior of the rabbit,Oryctolagus cuniculus,tested in an experimental chamber

The fecal pellets of rabbits,Oryctolagus cuniculus, are coated with secretion from the anal gland, the odor from which functions as a territorial marker. The total volatiles collected from above fecal pellets and three different fractions prepared by washing the volatiles through either distilled water, 1 M sodium hydroxide, or 1 M hydrochloric acid were tested for their effect on the territorial confidence of individual animals. Tests were based on the neutral pen paradigm used in previous studies but employed a specially designed test chamber, the internal odor environment of which could be fully controlled. In the four series of bioassays a total of 140 separate tests were performed and 64 adult male rabbits were used. The results showed that the presence of the total volatiles influences the outcome of territorial competitions in pairs of male rabbits in favor of the individual from which they were derived. They were comparable with those obtained in earlier studies when fecal pellets were presented in the test pen. The effects of the different washing reagents on the total odor are illustrated by gas chromatograms, and the components most likely to be removed by the different treatments are suggested. The volatiles remaining after passing through distilled water had less effect on the rabbit's behavior than the total odor. Since the washing process not only removed water-soluble compounds but also led to a reduction in the concentrations of water-insoluble components introduced into the test chamber, either of these factors could have been responsible for the weakened effect. Fractions of the odor obtained by washing with either sodium hydroxide or hydrochloric acid did not influence the results of the tests. This suggests that the essential components of the olfactory signal include both basic and acidic compounds.     

Effect of volatiles collected above fecal pellets on behavior of the rabbit,Oryctolagus cuniculus,tested in an experimental chamber

Gas chromatographic techniques were used to trap and fractionate the volatile substances emanating from the fecal pellets of wild rabbits,Oryctolagus cuniculus, which incorporate the odor of the anal gland secretion. The volatiles were bubbled through water, trapped on Chromosorb 105, transferred to Silicone SF96 traps, passed through a GC capillary column, and retrapped on SF96. The behavioral effect of trapped and fractionated volatiles was determined in four series of bioassays involving 51 adult, male, wild-type rabbits in 112, ten-minute tests. The bioassay was based on the demonstration of territorial confidence by the rabbits under the influence of their own odor. In the bioassays of the unfractionated volatiles eluted from Chromosorb 105 and SF96 traps the animals were significantly more confident in the presence of the volatiles from their own fecal pellets. One of the two fractions of the total volatiles was ineffective while the effect of the other was less than that of the unfractionated odor. The results demonstrate that the gas chromatographic techniques can be used to manipulate complex mammalian odors with precision. Combined with a discriminative bioassay, this opens up the possibility of identifying the specific combinations of volatile substances involved in the formation of olfactory signals.     

An investigation of human apocrine gland secretion for axillary odor precursors

Recently completed studies from our laboratories have demonstrated that the characteristic human male axillary odors consist of C₆ to C₁₁ normal, branched, and unsaturated aliphatic acids, with (E)-3-methyl-2-hexenoic acid being the most abundant. To investigate the mechanism by which the odor is formed, it is necessary to determine the nature of the odorless precursor(s) found in the apocrine secretion which is converted by the cutaneous microorganisms to the characteristic axillary odor. Pooled apocrine secretion was obtained from several male volunteers by intracutaneous injection of epinephrine. Partitioning this secretion into aqueous and organic soluble fractions was followed by hydrolysis of each fraction with NaOH or incubation with axillary microorganisms (cutaneous lipophilic corynebacterium). Analysis by gas chromatography/mass spectrometry (GC/MS) revealed the presence of (E)- and (Z)-3-methyl-2-hexenoic acid in the aqueous phase hydrolysate and aqueous phase incubated with bacteria; however, only a trace amount was seen in the resultant organic phase mixtures. These results suggest that a water-soluble precursor(s) is converted by the axillary flora to the characteristic axillary odors.     

Semiochemicals and social signaling in the wild European rabbit in Australia: II. Variations in chemical composition of chin gland secretion across sampling sites

The volatile components of the chin gland secretion of the wild European rabbit, Oryctolagus cuniculus (L.), were investigated with the use of gas chromatography. Studies of the chemical nature of this secretion by previous workers demonstrated that it was important in the maintenance of social structure in this species. This study identified 34 different volatile components that consist primarily of aromatic and aliphatic hydrocarbons. Especially common are a series of alkyl-substituted benzene derivatives that provide most of the compound diversity in the secretion. Samples of chin gland secretion collected from animals at three different geographical locations, separated by more than 100 km, showed significant differences in composition. This work suggests that variation among populations needs to be considered when undertaking semiochemical research. Alternate nonparametric methods are also used for the analysis of chromatographic data.     

Analysis of gular and paracloacal gland secretions of the american alligator (Alligator mississippiensis) by thin-layer chromatography Gland,sex, and individual differences in lipid components

Secretions from the gular and the paracloacal glands of adult male and female American alligators (Alligator mississippiensis) were extracted with chloroform, weighed, and analyzed by thin-layer chromatography. In both sexes, more lipoidal secretions were recovered from the paracloacal glands than from the gular glands. Females produce more lipoidal secretions in both sets of glands than do males. The thin-layer chromatograms of extracts from both glands exhibit bands consistent with aliphatic alcohols, sterols, free fatty acids, and steryl esters. Triglycerides, hydrocarbons, phosphatidylethanolamine, and lysophosphatidylcholine also are indicated in some chromatograms. Gland, sex, and individual differences are suggested in the thinlayer profiles.     

Chemistry of the mandibular gland secretion of the Indian beePithitis smaragdula

The mandibular glands of the stem-nesting Indian beePithitis smaragdula contain a mixture of salicylaldehyde, citronellyl acetate, geranyl acetate, pentadecane, heptadecane, ethyl tetradecanoate, and ethyl hexadecanoate. Salicylaldehyde is reported for the first time from a hymenopterous source. The secretion, emitted when the bee is disturbed, is rubbed with the legs over the bee's body and the disturbing object. The reactivity of some of the components in combination with the bee's behavior make the glandular exudate an effective defensive secretion.     

Seasonal variation of three ketones in the interdigital gland secretion of reindeer (Rangifer tarandus L.)

The seasonal variation of the three ketones, 6-methyl-2-heptanone, 7-methyl-3-octanone, and 7-methyl-1-octen-3-one, in the interdigital gland secretion of reindeer (Rangifer tarandus L.) has been investigated. A group of four adult animals, three females and one male, was used as a test group during a period of two years. Even though the three compounds are monitored in only a small number of test animals, it is evident that the ratios of the secretion's components vary over time. The variations are cyclic and are repeated from year to year.     

Responses by canids to scent gland secretions of the western diamondback rattlesnake (Crotalus atrox)

Many snakes discharge malodorous fluids from paired scent glands in the base of the tail when they are disturbed. A number of authors suggest that these secretions repel predators. Scent gland secretions of the western diamondback rattlesnake (Crotalus atrox), or dichloromethane extracts of them, were presented to coyotes (Canis latrans) in three field tests, and to domestic dogs (Canis familiaris) in two kennel tests, to determine whether responses of possible benefit to snakes are elicited. Free-ranging coyotes visited and rubbed and rolled at stations containing scent gland secretions in perforated plastic capsules more frequently than at those containing untreated or dichloromethane-treated capsules. Responses to dichloromethane extracts of scent gland secretions subjected to rotary evaporation were not significantly different from those to dichloromethane. Pure and mixed breeds of dogs presented with filter papers treated with dichloromethane or a dichloromethane extract of scent gland secretions mouthed (licked, bit, or ate) secretion-treated papers more frequently. Staffordshire terriers presented with filter papers treated with dichloromethane or dichloromethane extracts of snake scent gland and alligator (Alligator mississippiensis) paracloacal gland secretions exhibited urination postures to snake secretion-treated papers more frequently than to dichloromethane-treated papers, but responses to snake- and alligator-treated papers did not differ significantly. There was no indication that canids are repelled by scent gland secretions.     

Leek odor analysis by gas chromatography and identification of the most active substance for the leek moth,Acrolepiopsis assectella

When crushed, the leek,Allium porrum emits propyl propanethiosulfinate. The unstable thiosulfinate decomposes during GC analysis in numerous compounds, except on very short columns. The propyl propanethiosulfmate is the most attractive substance for the leek moth,Acrolepiopsis assectella. This thiosulfinate is not active onPlutella xylostella orPlodia interpunctella and seems to be repulsive onEphestia kuehniella.     

Chemical properties of femoral gland secretions in the desert iguana,Dipsosaurus dorsalis

This study investigates the chemistry of femoral gland secretions in the desert iguana,Dipsosaurus dorsalis (Lacertilia: Iguanidae), and discusses their possible functional significance. Electrophoretic and proton NMR studies indicated that the secretions are composed of approximately 80 % protein and 20% lipid material. Individual differences in polyacrylamide gel banding patterns of femoral gland proteins were found. Reflectance spectroscopy revealed that the secretions strongly absorb longwave ultraviolet light, a feature that may be important in the localization of secretion deposits in the environment.     

Chemical composition of the frontal gland secretion ofSyntermes soldiers (Isoptera,Termitidae)

The defensive secretions from the frontal glands of soldier termites of the genusSyntermes contain similar mixtures of mono- and sesquiterpene hydrocarbons. The major components inS. dirus, S. molestus, S. brevimalatus, S. peruanus, and a new species (Syntermes sp. n), iscis--ocimene. A substantial amount of aristolochene is found inSyntermes sp. n. and is present at lower levels in all the other species;S. brevimalatus contains onlycis--ocimene and aristolochene. The four other species also contain minor amounts of epi--selinene and germacrene A. The latter compound has been identified on the basis of its rearrangement product -elemene. The termiteS. grandis differed markedly from the otherSyntermes species in that no terpenoid components were found in the soldier extract. With the obvious exception ofS. grandis, the same soldier-specific mono- and sesquiterpenes occurred in all species. The total amount of secretion per unit weight of soldiers varies with the species and is inversely proportional to the development of the mandibular apparatus. InS. molestus smaller gland size is compensated for by a greater number of soldiers foraging trails.