Airborne differences in odors emitted byRattus norvegicus in response to reward and nonreward

To test the hypothesis that rats (Rattus norvegicus) emit airborne, differential odors in response to reward and nonreward, donor rats received random sequences of rewarded and nonrewarded placements in small compartments and an airstream transported odors from these compartments to test rats in a separate chamber. When donors remained in the compartments during, or were removed just prior to, air transport, test rats utilized transported odors as discriminative cues signaling their own reward and nonreward for a lever-press response. When the airstream was passed through a clean compartment containing paper flooring extracted from donor compartments, test rats were not able to discriminate. Test trials to assess for control by food odors suggest that donor-produced odors, rather than food odors per se, provided the discriminative signals for test rats. Results confirm the existence of somewhat volatile, although apparently stable, odors emitted in response to reward and nonreward, and implicate a differential in amount and/or type of odor produced by donors to these two events as the source of discriminative control.     

Morphology and chemistry of brown rat,Rattus norvegicus,preputial and clitoral glands

In contrast to previous results from laboratory rats, when sexual dimorphism occurred, clitoral glands from wild female rats were heavier and accounted for a greater proportion of body mass than preputial glands from wild males. Gland length and weight increased with body weight, but gland weight as a proportion of body weight did not. Preputial and clitoral glands showed seasonal differences in size: at one site glands were smaller in December than in April. Maturity, estrus, and pregnancy had no significant effect on clitoral gland size, but immature males had proportionally smaller preputial glands than mature males, and the absolute gland weight, but not gland weight as a proportion of body weight, increased with testes weight. There were no differences between the sexes in lipid production, which increased with preputial or clitoral gland weight. An homologous series of aliphatic acids and their methyl and ethyl esters, plus squalene, cholesterol and lanosterol, was revealed by GC-MS study of the trimethyl silyl derivatized lipid extract. Males and females could be distinguished by principal component analysis of chromatogram peaks.     

Exposure to Urine of Canids and Felids, but not of Herbivores, Induces Defensive Behavior in Laboratory Rats

Predator odors induce defensive behavior in many prey species. For various reasons, studies carried out up to now have been unable to establish whether predator odor recognition is innate or not. Mostly, only particular odors or wild-living (i.e., experienced) test animals have been used in these studies, restricting the conclusiveness of the observations. In the present study, the behavioral effects of exposure to different predator odors on predator odor-naive laboratory male rats were compared with the effects of different nonpredator odors and of a no-odor control stimulus. Results show that exposure to urine of canids and felids, but not of herbivores or conspecifics, induce defensive behaviors. Taken together, the study provides support for the hypothesis that there is an innate recognition of predator odors in laboratory rats.     

Taxon-specific differences in responsiveness to capsaicin and several analogues: Correlates between chemical structure and behavioral aversiveness

The present set of experiments was designed to explore avian insensitivity to capsaicin. Based upon a molecular model of avian chemosensory repellency, we hypothesized that structural modifications of the basic capsaicin molecule, which is itself not aversive to birds, might produce aversive analogues. To this end, European starlings (Sturnus vulgaris) and Norway rats (Rattus norvegicus) were given varied concentrations of synthetic capsaicin and four analogues (methyl capsaicin, veratryl amine, veratryl acetamide, vanillyl acetamide) in feeding and drinking tests. The results agreed with a model that we are developing to describe the chemical nature of avian repellents. Synthetic capsaicin and vanillyl acetamide were not repellent to birds, owing to the presence of an acidic phenolic OH group. Conversely, veratryl acetamide was aversive, due to the basic nature of this compound. For rats, repellent effectiveness among compounds was reversed: synthetic capsaicin was the best repellent while veratryl acetamide was the worst. We speculate that this taxonomic reversal may reflect basic differences in trigeminal chemoreception. In any case, it is clear that chemical correlates of mammalian repellents are opposite to those that predict avian repellency.     

Responses of Wild Norway Rats (Rattus norvegicus) to Predator Odors

If rats could be shown to avoid the odors of predators, then conservation managers could manipulate this behavior to exclude rats from important conservation sites. We evaluated the ability of six predator odors to elicit avoidance responses by wild-caught Norway rats (Rattus norvegicus) from two New Zealand populations (Kapiti Island and North Island). Kapiti Island is free of mammalian predators, while the North Island has established populations of felids, canids, and mustelids. Three of the predator odors were real and three were synthesized volatile ingredients of real animal feces or urine. We compared the rats' responses to predator odors with their responses to three natural herbivore odors. We used a Y maze, and rats were offered the choice of an odor in one arm of the maze and distilled water in the other arm. Each choice arm was ducted at the entrance to remove air and the odor. We recorded: (1) the time until the rat left the first arm of the maze, (2) the time until the rat visited each arm, (3) the number of visits to each arm, (4) the amount of time spent in each arm, and (5) a total activity score for each rat. Kapiti rats showed an aversion to five of the six predator odors, despite never having encountered them before. Kapiti rats visited herbivore odors more often than carnivore odors and were less active in the presence of carnivore odors than they were when tested with herbivore odors. In addition, Kapiti rats approached some herbivore odors more quickly than they approached carnivore odors. North Island rats appeared to avoid cat urine, but despite being predator experienced, did not show a consistent aversion to the carnivore odors we tested. Both samples of rats, but particularly the North Island group, showed high individual variation. We conclude that predator odors are unlikely to be an effective management tool for all populations of this species of rat because of this high individual variability and the likelihood that each island population will differ in its responses to a given odor.     

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.     

Identity and Function of Scent Marks Deposited by Foraging Bumblebees

Foraging bumblebees can detect scents left on flowers by previous bumblebee visitors and hence avoid flowers that have been depleted of nectar. Tarsal secretions are probably responsible for this repellent effect. The chemical components of the tarsal glands were analyzed by combined gas chromatography–mass spectrometry for three species of bumblebee, Bombus terrestris, B. lapidarius, and B. pascuorum. The hydrocarbons identified were similar for each species, although there were interspecific differences in the relative amounts of each compound present. The tarsal extracts of all three species comprised complex mixtures of long-chain alkanes and alkenes with between 21 and 29 carbon atoms. When B. terrestris tarsal extracts were applied to flowers and offered to foraging bumblebees of the three species, each exhibited a similar response; concentrated solutions produced a repellent effect, which decreased as the concentration declined. We bioassayed synthetic tricosane (one of the compounds found in the tarsal extracts) at a range of doses to determine whether it gave a similar response. Doses 10^–12 ng/flower resulted in rejection by foraging B. lapidarius. Only when 10^–14 ng was applied did the repellent effect fade. We bioassayed four other synthetic compounds found in tarsal extracts and a mixture of all five compounds to determine which were important in inducing a repellent effect in B. lapidarius workers. All induced repellency but the strength of the response varied; heneicosane was most repellent while tricosene was least repellent. These findings are discussed in relation to previous studies that found that tarsal scent marks were attractive rather than repellent.     

Structure-activity relationship of stress-inducing odorants in the rat

The stress for 12 sulfur-containing synthetized volatiles was evaluated in male Wistar rats and compared to that for fox-dropping extract concentrate. Stress behavior was analyzed by quantifying various stress responses in a standard open field and measuring the increase in plasma corticosterone concentration. Nine compounds induced stress—a dihydrothiazole, two cyclic polysulfides, five mercaptoketones, and a mercaptan. For the mercaptoketones, the following structure-activity relationships were observed. Size can vary considerably; the mercapto group can be either alpha or beta and either secondary or tertiary. The keto group is not essential, since a structurally related mercaptan remains active. The mercapto group is essential for activity in mercaptoketones, since conversion to a methyl sulfide resulted in a neutral response. This type of odorant could function as an allomone and may have potential in rat control as an area repellent.     

Urine-marking and the response to fresh vs. aged urine in wild and domestic Norway rats

Wild and domestic Norway rats (Rattus norvegiens) were compared in regard to their tendency to investigate the odors of fresh vs. aged rat urine and to urine-mark metal rods and wooden blocks placed in their home cages. Castration, sex, and domestication had no effect on the tendency to investigate sources of fresh vs. aged urine odors, but the odor of aged urine was more attractive than fresh urine for most subjects tested. The frequency of urine marking was lower for females and castrated males but generally did not differ between wild and domestic stocks. The implications of these findings for the ecology of the species are discussed.     

Behavioral Foraging Responses by the Butterfly Heliconius melpomene to Lantana camara Floral Scent

Floral color has been shown to influence flower selection by butterflies, but few studies have investigated the role of floral scent. In this study, adults of Heliconius melpomene L. (Lepidoptera: Nymphalidae: Heliconiinae) were tested in two-choice bioassays to investigate their ability to distinguish floral scent of the butterfly pollinated plant Lantana camara L. (Verbenaceae) from other plant scents. The relative importance of floral scent vs. color was also studied. Butterfly foraging behavior was measured as probing with proboscis. This probing, on floral models varying in scent and color, was timed. When given a choice of floral and vegetative scents of L. camara, newly emerged butterflies preferred floral scent, indicating an innate response to floral scents. When butterflies were conditioned to L. camara floral scent by offering the scent with yellow color and sugar water, yellow color elicited stronger feeding responses than did the floral scent. However, the floral scent of L. camara was preferred to that of the novel species Philadelphus coronarius L. (Hydrangiaceae). The floral scent of L. camara was dominated by tepenoid compounds, while that of P. coronarius by fatty acid derivatives, thus demonstrating totally different compositions. It is concluded that, while H. melpomene butterflies often use visual floral traits when selecting which flowers to visit, floral scents elicit behavioral responses that initiate and maintain foraging on flowers.     

Foveal glands,source of sex pheromone production in the ixodid tickDermacentor andersoni stiles

The foveal glands of the Rocky Mountain wood tick,Dermacentor andersoni Stiles, are the sex pheromone glands from which the sex pheromone is released via the foveae dorsales. The sex pheromone, 2,6-dichlorophenol, was recovered from extracts of these glands by GLC. Other evidence of the role of these glands in sex pheromone production is described. A³⁶Cl-labelled volatile compound (or compounds) was (were) collected from partially engorged femaleD. andersoni fed in³⁶Cl-labelled hosts, but no labelled compounds were collected when the foveae dorsales were blocked. X-ray analysis revealed unusual concentrations of chlorine in the foveal glands compared to other tissues. Autoradiography also revealed significant accumulations of radiochlorine in the vicinity of these glands.Presumably, the foveal glands of the American dog tick,Dermacentor variabilis (Say), are the sex pheromone glands of that species also, since a³⁶Cl-labelled volatile was collected from female ticks fed on a³⁶Cl-labelled host. However, attempts to recover 2,6-dichlorophenol from gland extracts or volatile emissions fromD. variabilis were unsuccessful.Supported by grants AI 10,986 and AI 10,987 from the National Institute of Allergy and Infectious Diseases, U.S. Public Health Service, U.S. Department of Health, Education and Welfare, Bethesda, Maryland, 20014.     

Chemical Profiles of Scent Gland Secretions in the Cyphophthalmid Opilionid Harvestmen, <Emphasis Type="Italic">Siro duricorius</Emphasis> and <Emphasis Type="Italic">S. exilis</Emphasis>

Gas chromatographic–mass spectrometric analyses of the scent gland secretions of Siro duricorius and S. exilis (Opiliones, Cyphophthalmi, Sironidae) revealed a set of 24 components, comprising a series of saturated and unsaturated methyl ketones (C11–C15) and four naphthoquinones. Whereas the scent gland secretions of S. duricorius, collected in Austria, and S. exilis from USA were qualitatively nearly indistinguishable (with the exception of acetophenone that was specific to S. duricorius), they distinctly differed in their relative quantitative compositions: major components of the secretion of S. duricorius were 7-tridecen-2-one, tridecan-2-one, undecan-2-one, 1,4-naphthoquinone, 6-methyl-1,4-naphthoquinone (tentatively identified only), and 4-chloro-1,2-naphthoquinone. In contrast, in S. exilis a compound tentatively identified as 6-methyl-4-chloro-1,2-naphthoquinone was present in large amounts (in S. duricorius a trace component), whereas undecan-2-one only occurred in minor quantities. Secretion profiles of juveniles and adults (both sexes) of each species showed high correspondence.This is the first report on the chemistry of scent gland secretions of the opilionid suborder Cyphophthalmi. 4-Chloro-1,2-naphthoquinone was identified as a new exocrine product of arthropods, whereas 1,4-naphthoquinone and the tentatively identified 6-methyl-1,4-naphthoquinone are known constituents of exocrine secretions from one species of palpatorid opilionids, Phalangium opilio. In contrast, all ketones identified were new for opilionid scent glands, although similar ketones are characteristic of scent gland secretions of palpatorid genera Leiobunum and Hadrobunus. With regard to the near-basic position of Cyphophthalmi in currently proposed phylogenetic trees of Opiliones, naphthoquinones and ketones from Siro may represent the condition ancestral to the (derived) naphthoquinone- and ketone-rich secretions in phalangid Palpatores.     

Scent marks as social signals inGalago crassicaudatus II. Discrimination between individuals by scent

Thick-tailed galagos,Galago crassicaudatus argentatus, which had been habituated to the scent marks of a conspecific through repeated presentations, increased their sniffing when presented with scent marks from a second conspecific of the same sex. Thus, they discriminated between the scents of individual conspecifics. This result was obtained using naturally scent-marked perches and perches carrying only chest gland scent—the latter even two weeks after the marking. When urine, the prevalent scent signal among most other galago species, was tested, it elicited little interest and discriminations were not clearly made. It is suggested that the use of more specialized scents is related to the social characteristics ofGalago crassicaudatus.     

Metasternal Gland Volatiles and Sexual Communication in the Triatomine Bug, Rhodnius prolixus

Twelve compounds produced by the metasternal glands (MGs) of the triatomine bug Rhodnius prolixus were identified by solid phase microextraction (SPME) combined with coupled gas chromatography-mass spectrometry (GC-MS) using achiral and chiral columns. All substances were ketones or alcohols, and the same compound profile was found in the secretions produced by either sex. The most abundant compounds were 2-methyl-3-buten-2-ol, (2S)-pentanol, (3E)-2-methyl-3-penten-2-ol, and (2R/2S)-4-methyl-3-penten-2-ol. Emission of these compounds was detected more frequently from females than males, and females released them more frequently during the early hours of the scotophase, the period when sexual activity in this species is at its peak. These compounds were also detected in the headspace above mating pairs. Finally, the occlusion of the MG orifices of male or female bugs with paraffin resulted in a significant decrease in copulation frequency compared to sham-operated insects. Together, these data suggest that the MG secretions of R. prolixus may be involved in sexual communication.     

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.     

Scent Marking in Male Premating Behavior of Bombus confusus

Premating behavior in the species Bombus confusus Schenck, 1859 was studied. The marking habits of bumblebee males were revealed and the use of their labial gland secretion in scent marks was proved chemically. Identical compounds were present both in the labial gland secretion and on male-marked objects. This chemical proof is reported for the first time from natural conditions of a B. confusus locality. Males' flight activities, site tenacity, and male–male interactions are described in detail. Contrary to literature reports, male B. confusus behavior does not basically differ from that of already known perching bumblebee species.     

1,4-Dimethoxybenzene,a Floral Scent Compound in Willows that Attracts an Oligolectic Bee

Many bees are oligolectic and collect pollen for their larvae only from one particular plant family or genus. Here, we identified flower scent compounds of two Salix species important for the attraction of the oligolectic bee Andrena vaga, which collects pollen only from Salix. Flower scent was collected by using dynamic-headspace methods from Salix caprea and S. atrocinerea, and the samples were subsequently analyzed by coupled gas chromatographic–electroantennographic detection (GC-EAD) to detect possible attractants of A. vaga. EAD active compounds were identified by gas chromatography coupled to mass spectrometry. Both Salix species had relatively similar scent profiles, and the antennae of male and female bees responded to at least 16 compounds, among them different benzenoids as well as oxygenated monoterpenoids and sesquiterpenoids. The strongest antennal responses were triggered by 1,4-dimethoxybenzene, and in field bioassays, this benzenoid attracted females of A. vaga at the beginning of its flight period, but not at the end.     

Effects of sex pheromone on locomotion in the male American cockroach,Periplaneta americana

The locomotory activities of individual males ofPeriplaneta americana in a circular arena 2.5 m in diameter were investigated during the portion of the photocycle in which the cockroaches are most active. Control animals ran at an average speed of 10.86 cm/sec but remained immobile 68 % of the time. Pauses in locomotion occurred frequently and at fairly regular intervals (x=0.88 sec). Males showed a strong tendency to remain near the sides of the arena. Sex pheromone presented in the center of the arena produced a reduction in immobility time and a slight increase in running speed. The frequency of pauses decreased, and the time between pauses became less regular. The proportion of time spent near the sides of the arena was greatly reduced also.     

Individual, Sexual, Seasonal, and Temporal Variation in the Amount of Sagebrush Lizard Scent Marks

Although many animals deposit scent marks, previous studies have focused almost entirely on rodents or on the chemical structure of the signal. Here, we study the quantity and temporal pattern of chemical deposition by the territorial sagebrush lizard Sceloporus graciosus, measuring both femoral pore and fecal deposits. Specifically, we tested whether variation in deposition is a good cue of individual and sexual identity and/or whether it is more closely associated with body size and reproductive state, indicators of physiological condition. The results support the latter hypothesis. We found that although the amount of fluid deposited on a single perch (rarely quantified in mammals) carries little information on individual or sexual identity, it reflects the physiological condition and reproductive state of individual lizards and is replenished on a roughly weekly cycle, potentially providing additional information on the producer's activity level. The amount of deposition may thus provide important information to chemical receivers making mate choice and territorial defense decisions. The results further suggest that seasonal increases in gland production allow lizards to mark more sites rather than to influence the quality of the signal on a single perch.     

Social behavior and chemical communication in reindeer (Rangifer t. tarandus L.)

The social interactions of captive reindeer were observed for one year. The seasonal changes of agonistic behavior, the social rank order, social affinity during rest, social sniffing and licking, solitary sniffing and licking, hindleg-head contact, and other motor patterns involving head and antlers are described. Social sniffing and licking correlated more with sex than with social rank. Olfactory responses during encounters and tracking were investigated experimentally. Chemical communication is particularly important in sexual and maternal behavior and during encounters.