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

To demonstrate that the inguinal gland odor conveys information on the identity of individuals, 60 male, wild-type rabbits,Oryctolagus cuniculus, living in groups of three in outdoor pens, were used in 120 tests. Members of the groups smeared with the inguinal gland secretion from unfamiliar rabbits were attacked by their penmates. In contrast the odors of chin gland secretions and urine of strange rabbits and of a commercial perfume did not cause serious disruption to the social relationships within the groups.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Anal gland secretion of European mole: Volatile constituents and significance in territorial maintenance

The chemical composition of the volatile components of the anal gland secretion of mature and immature moles of both sexes was examined by gas chromatography and mass spectrometry. The compounds in the secretion of adult males appear to vary little throughout the year and are similar to those from the adult female outside the breeding season. The secretions are dominated by C₅-C₁₀ carboxylic acids. Female glands regress as they enter proestrus, accompanied by profound changes in the chemical composition of the secretion with early disappearance of the carboxylic acids. In juvenile moles, the composition of the secretion changes as the animal matures, with carboxylic acids becoming dominant only as the animal reaches maturity. Anal gland secretion probably plays an important role in territorial maintenance.     

Identification of odors from overripe mango that attract vinegar flies,Drosophila melanogaster

Bioassays with a variety of overripe fruits, including mango, plum, pear, and grape, and their extracts showed that odors from overripe mango were most attractive to adult vinegar flies, Drosophila melanogaster. Combined gas chromatography–electroantennographic detection (GC-EAD) analyses of solid-phase microextraction (SPME) and Tenax extracts of overripe mango odors showed that several volatile compounds, including ethanol, acetic acid, amyl acetate, 2-phenylethanol, and phenylethyl acetate elicited significant EAG responses from antennae of female flies. Most of the volatile compounds in the extracts were identified by mass spectral and retention index comparisons with synthetic standards. In cage bioassays, lures with a blend of ethanol, acetic acid, and 2-phenylethanol in a ratio of 1:22:5 attracted six times more flies than any single EAG-active compound. This blend also attracted four times more flies than traps baited with overripe mango or unripe mango. However, in field trials, the blend was not as attractive as suggested by the laboratory bioassay.     

Castor sacs and anal glands of the north american beaver (Castor canadensis): their histology,development, and relationship to scent communication

Both sexes of beavers possess a pair of castor sacs and a pair of anal glands located in paired subcutaneous cavities between the pelvis and the base of the tail. The castor sacs are not glandular in the histological sense, hence references to these structures as preputial glands or castor glands are misnomers. The wall of the castor sacs is plicate and comprised of three distinct zones: an outer layer of vascular connective tissue, a two-to five-cell-thick layer of mitotic epithelial cells, and several densely packed layers of cornified epithelium which grade into more widely separated sheets toward the lumen. Monocultures of a gram-positive facultatively anaerobic bacterium were present in the lumen of all castor sac preparations. Differences in the frequency of castoreum deposition were not attributable to differences in the structure of the castor sacs. The anal glands of beavers are holocrine sebaceous glands. These glands develop more rapidly than the castor sacs. Anal gland tissue from embryos exhibited cellular characteristics associated with the production of sebum. Secretory activity was evident in all preparations. The relationship of castoreum and anal gland secretion to scent communication among beavers is discussed.     

Ability of honeybee,Apis mellifera,to detect and discriminate odors of varieties of canola (Brassica rapa and Brassica napus) and snapdragon flowers (Antirrhinum majus)

Honeybees (Apis mellifera) use odors to identify and discriminate among flowers during foraging. This series of experiments examined the ability of bees to detect and discriminate among the floral odors of different varieties of two species of canola (Brassica rapa and Brassica napus) and also among three varieties of snapdragons (Antirhinnum majus). Individual worker honeybees were trained using a proboscis extension assay. The ability of bees to distinguish a floral odor from an air stimulus during training increased as the number of flowers used during training increased. Bees conditioned to the odor of one variety of flower were asked to discriminate it from the odors of other flowers in two different training assays. Bees were unable to discriminate among flowers at the level of variety in a randomized presentation of a reinforced floral odor and an unreinforced floral odor. In the second type of assay, bees were trained with one floral variety for 40 trials without reinforcement and then tested with the same variety or with other varieties and species. If a bee had been trained with a variety of canola, it was unable to differentiate the odor of one canola flower from the odor of other canola flowers, but it could differentiate canola from the odor of a snapdragon flower. Bees trained with the odor of snapdragon flowers readily differentiated the odor of one variety of a snapdragon from the odor of other varieties of snapdragons and also canola flowers. Our study suggests that both intensity and odor quality affect the ability of honeybees to differentiate among floral perfumes.     

Elemental Sulfur Identified in Urine of Cheetah, Acinonyx jubatus

The urine of the cheetah, Acinonyx jubatus, is almost odorless, and probably for this reason, it has not attracted much attention from scientists. Using gas chromatography–mass spectrometry, we identified 27 and 37 constituents in the headspace vapor of the urine of male and female cheetah, respectively. These constituents, composed of hydrocarbons, short-chain ethers, aldehydes, saturated and unsaturated cyclic and acyclic ketones, 2-acetylfuran, dimethyl disulfide, dimethyl sulfone, phenol, myristic acid (tetradecanoic acid), urea, and elemental sulfur, are all present in the headspace vapor in very small quantities; dimethyl disulfide is present in such a low concentration that it cannot be detected by the human nose. This is only the second example of elemental sulfur being secreted or excreted by an animal. It is hypothesized that the conversion of sulfur-containing compounds in the cheetah's diet to elemental sulfur and to practically odorless dimethyl sulfone enables this carnivore to operate as if “invisible” to the olfactory world of its predators as well as its prey, which would increase its chances of survival.     

Use of predator odors as repellents to reduce feeding damage by herbivores

This study investigated the influence of the major anal-gland compounds from the stoat (Mustela erminea) and fecal and urine compounds from the red fox (Vulpes vulpes) in generating an avoidance response by montane voles (Microtus montanus), as well as suppressing feeding by montane and meadow (M. pennsylvanicus) voles on apple trees in orchards. In trap bioassays, a 11 mixture of 2-propylthietane and 3-propyl-1,2-dithiolane significantly reduced vole captures. Other mixtures of stoat compounds reduced the number of new voles captured but not total individuals. 2,5-Dihydro-2,4,5-trimethylthiazoline, a component of fox feces, significantly reduced vole captures in one of two bioassays. Deer mice (Peromyscus maniculatus) did not show a negative response to any predator odor. In overwinter field bioassays, mixtures of 2-propylthietane and 3-propyl-1,2-dithiolane clearly reduced vole feeding on apple trees in four test blocks. 2,5-Dihydro-2,4,5-trimethylthiazoline and a synthetic fox urine mixture also significantly reduced vole attack in respective orchard blocks. Similarly, the intensity of vole feeding, in terms of amount of bark and vascular tissues removed from trees, was reduced by 60% to 97% in predator odor treatments compared with the control. Our study reports the first long-term (four to five months) use of synthetic semiochemicals as area repellents for crop protection from vole feeding damage.     

Semiochemicals and Social Signaling in the Wild European Rabbit in Australia: I. Scent Profiles of Chin Gland Secretion from the Field

The European rabbit (Oryctolagus cuniculus) uses the secretion of the chin gland in the maintenance of social status. Previous work has concentrated on secretion collected directly from the animal. In this study, the analysis was conducted by collecting scent marks made by free-ranging animals. Scent marks were found to be concentrated at the center of the area controlled by a social group, and at the boundaries between two adjacent social groups. Only the mark from dominant animals could be identified. Marks were also collected from the skin of rabbits, where they had been placed by the dominant individual. The mark found on the head of a subordinate animal may, in the future, be used to identify the dominant animal of the social group, who placed the mark.     

Actinidine from the defensive secretions of dolichoderine ants

The alkaloid actinidine has been identified as an anal gland product of two species of dolichoderine ants in the genusConomyrma. The biosynthetic implications of this finding are discussed.     

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.