The social role of scent marking in beaver (Castor Canadensis)

Beaver colonies with close neighbors constructed more scent mounds than did isolated colonies, and the number of scent mounds at each active lodge is correlated with the distance to the nearest occupied lodge. The scent mounds were typically located at trails, also on lodges and dams. The beaver rebuilt experimentally removed scent mounds. Experimentally scent-marked unoccupied lodges were less often visited or inhabited than unscented control lodges. Resident beaver responded to artificial scent marks near their lodges with aggressive behavior and increased activity. We conclude that scent mounds serve in delineating family territories and are effective in deterring transient beaver from utilizing existing but uninhabited lodges.     

Odorant Source Used in Eurasian Beaver Territory Marking

Mammals use urine, feces, or the secretion of specialized skin glands to mark their territories. These sources can carry different information and, thus, have different functions. Presently it is not known if beavers (Castor spp.) deposit castoreum (primarily a mixture of secondary metabolites from urine) from the castor sacs and secretion from the anal glands (AGS) together or alone when scent marking their territories. We hypothesized that castoreum would be the main scent signal used in the defense of beaver territories during winter and predicted that castoreum would be deposited more often than AGS. A total of 96 scent marks on snow were collected from January 1 to March 31, 1997–1999 in the Bø River, Telemark County, Norway. In order to obtain control material, we chemically analyzed AGS and castoreum from 60 dead beavers collected during January–May 1997–1999. We compared the compounds found in the dead beavers with compounds found in the scent marks on snow. Samples were analyzed by using gas chromatography–mass spectrometry (GC-MS). All 96 scent marks contained compounds from castoreum, whereas compounds from AGS were found in only four scent marks. This suggests that beavers do not specifically deposit AGS on scent mounds as they do with castoreum and that the AGS compounds we found probably were remnants of AGS from the feet or fur following pelt lubrication or coprophagy behavior. We conclude that castoreum is the main scent signal used in the defense of beaver territories during winter.     

Sexual Dimorphism in Territorial Scent Marking by Adult Eurasian Beavers (Castor fiber)

Mammalian scent marking is often associated with territorial defense. However, males and females may demonstrate different activity patterns and play different roles. Female mammals nurture the young during lactation, while males purportedly perform other tasks more frequently, such as territorial maintenance and defense. This paper investigates the contribution made by mated pairs of adult males and females to territorial scent-marking in the obligate monogamous Eurasian beavers (Castor fiber). We hypothesized that both sexes should show territorial behavior, and predicted that they deposit a higher proportion of scent marks at borders. We also hypothesized that a sexual dimorphism exists due to reproductive constraints on the females, and predicted that males should invest significantly more in scent-marking behavior than females during summer. We obtained behavioral data by radio tracking six mated pairs of Eurasian beavers during spring and summer 2000–2001 on two rivers in southeastern Norway. Our results showed that both males and females clustered their scent marks near territorial borders, but males deposited a larger number of scent marks than females and spent more time at borders. Males were also found to have a higher scent marking rate and scent marks per night than females during summer, but not during spring. Overall, scent marks per night were higher in males than females. We conclude that both males and females Eurasian beavers carry out territorial behavior by scent marking, but males carry a larger part of the territorial defense during summer when females lactate. Our results are discussed in the light of the codefense hypothesis.     

Phenolic compounds from male castoreum of the North American beaver,Castor canadensis

North American beaver (Castor canadensis) mark their territories with castoreum, the contents of their castor sacs. In their territories, beaver respond with scent marking to experimental scent marks consisting of castoreum, or selected single components. In part, the unique odor of castoreum is due to large amounts of phenolic compounds. Purified phenolic components were analyzed by GC, GC-MS, and NMR; identifications were confirmed by comparing the spectra of synthetic phenols with those of the isolated phenols. Of the 15 phenols reported elsewhere, only five were confirmed in our analysis; the other 10 phenolic compounds are either absent or are not volatile enough to be detected by our methods. In addition, 10 phenolic compounds have been identified in this study that were not reported in the previous papers concerning the constitution of castoreum.     

Behavioral responses to own and other species' scent marks inLemur fulvus andLemur macaco

Behavioral responses (duration and frequencies of sniffing, scent marking activity) were studied in one captive group each ofL. fulvus andL. macaco when confronted with their own and other species' scent marks. Both species showed less interest in neutral objects or objects carrying their own group's odor than odors from an unfamiliar group of the same species or from another lemur species. The persistence of scent marks was also investigated.L. fulvus scent appeared to possess greater longevity thanL. macaco scent. Olfactory long-term memory was analyzed inL. fulvus. The results showed that familiar rejected group members could be discriminated from an unfamiliar conspecific through odor cues 10 months after their eviction from the group.     

Do Eurasian beavers smear their pelage with castoreum and anal gland secretion?

The scent-matching hypothesis postulates that scent marks provide an olfactory link between a resident owner and his territory, and that this enables intruding animals to recognize the chance of escalated conflicts. However, it is unclear if Eurasian beavers (Castor fiber) mark their own pelage with castoreum from their castor sacs (i.e., the same material used in territorial marking); and/or if beavers mark their pelage with anal gland secretion (AGS) from the anal glands to waterproof the pelage and to act as a living-scent mark. Chemical analysis (gas chromatography and mass spectrometry) of hair samples from 22 live-trapped beavers revealed that castoreum compounds were not present in any samples, AGS compounds were found from 3 animals (13.6%) around the cloaca, and the compound squalene was found in all the samples. Beavers may release castoreum directly into the water when it meets an intruder. Thereby, the scent mark in the water can provide an olfactory link between a resident owner and his territory. Squalene, in contrast to AGS, may be essential for keeping beaver pelts water-repellant.     

Antennal Responses to Floral Scents in the Butterfly Heliconius melpomene

Floral scent, together with visual floral cues, are important signals to adult butterflies searching for food-rewarding plants. To identify which compounds in a floral scent are more attractive and, thus, of biological importance to foraging butterflies, we applied electrophysiological methods. Antennal responses of male and female adults of the tropical butterfly Heliconius melpomene L. (Lepidoptera: Nymphalidae: Heliconiinae) to individual compounds of natural floral scents and synthetic floral scent mixtures were investigated using gas chromatography–electroantennographic detection (GC-EAD). The natural floral scents included those of two tropical plant species, Lantana camaraL. (Verbenaceae) and Warszewiczia coccinea (Vahl) Kl. (Rubiaceae), and two temperate species, Buddleja davidii Franchet (Loganiaceae) and Cirsium arvense (L.) Scop. (Asteraceae). The two synthetic floral scent mixtures contained many of the compounds found in the natural scents, but all in equal quantities. Compounds both present in relatively high abundance in the floral scents and detected exclusively in the floral parts of the plant, such as linalool, linalool oxide (furanoid) I and II, oxoisophoroneoxide, and phenylacetaldehyde, elicited the strongest antennal responses, suggesting that they may reflect adaptations by the plant to attract butterfly pollinators. However, other compounds also present in high abundance in the floral scent, but detected in the vegetative as well as floral plant parts, either elicited strong antennal responses, such as trans--ocimene and benzaldehyde, or failed to elicit antennal responses, such as the sesquiterpenes -caryophyllene and -humulene from L. camara. The most volatile monoterpene alkenes in the synthetic scent mixtures elicited only low or no responses. Furthermore, the overall antennal responses were stronger in females than in males. The findings suggest that several floral scent volatiles, especially those of exclusively floral origin, are of high biological significance to H. melpomene butterflies. These include compounds of different biosynthetic origins belonging to the benzenoids, monoterpenoids, and irregular terpenoids.     

Neutral compounds from male castoreum of North American beaver,Castor canadensis

North American beavers (Castor canadensis) mark their territories with castoreum, the strong-smelling paste in their castor sacs. In their own territories, beavers respond with scent marking to experimental scent marks that consist of strange castoreum (or selected components). In part, the unique odor of castoreum is due to large amounts of phenolic compounds and neutral compounds. Purified neutral compounds were analyzed by GC. GC-MS, and NMR; identities of the neutral compounds were confirmed by comparing the properties of authentic compounds with those of the isolated compounds. We identified 13 neutral compounds that had not been reported before for castoreum. Most of these are oxygen-containing monoterpenes. Of the nine neutral compounds reported by Lederer (1949), only three are confirmed in our analysis; the other six neutral compounds are either absent or are not volatile enough to be detected by our methods. Eight compounds—6-methyl-l-heptanol, 4,6-dimethyl-l-heptanol, isopinocamphone, pinocamphone, two linalool oxides, and their acetates—were synthesized for structure identification and bioassays.     

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.     

Responses to inter- and intraspecific scent marks in pine martens (Martes martes)

In order to analyze intra and interspecific olfactory discrimination, behavioral responses (sniffing and marking) towards various odors were observed in pine martens (Manes martes). Two adult males and two adult females were tested for intraspecific discrimination of abdominal gland odors and urine. Both sexes sniffed and marked objects carrying their own scent less than unscented objects. There were no differences in sniffing or marking objects impregnated with odors from known and unknown conspecifics of the opposite sex or objects carrying the odor of an unknown male or female. A second experiment with two adult females gave no evidence for interspecific discrimination: no differences emerged when comparing reactions towards marks of pine martens, stone martens (a closely related species), or genets. The most obvious result of this study is the reduced response of pine martens towards their own mark. It is suggested that scent marking in martens may reflect autocommunication, the primary effect being to familiarize an animal with its environment.     

Sex pheromone scent marking by females ofPectinophora gossypiella (Lepidoptera: Gelechiidae)

Females of the pink bollworm moth,Pectinophora gossypiella (Saunders), scent marked the substrate to which they were clinging with the extended pheromone gland during nocturnal pheromonereleasing periods. Scent marks were deposited on both natural (cotton leaf) and atypical (glass) substrates. In both situations, the scent marks elicited attraction responses from conspecific males.     

Comparison of release devices for stoat (Mustela ermined) semiochemicals used as montane vole (Microtus montanus) repellents

Fenced enclosures were used to simulate peak populations of montane voles (Microtus montanus) for field bioassays of a stoat (Mustela erminea) scent mixture in various controlled-release devices. A 1 1 mixture of 2-propylthietane and 3-propyl-1,2-dithiolane was dispensed in capillary tubes, clay pellets (activated alumina), rubber septa, and plastic rope. Release devices were placed near, or attached to, young apple trees planted in blocks in two enclosures containing high populations of voles. The stoat scent mixture in rubber septa and plastic rope significantly reduced vole attack of trees compared with a control, pellets, and capillary tubes. In terms of complete girdling (tree mortality), this odor in septa and rope also significantly reduced feeding compared with the control, and the rubber septa formulation was more effective than either the pellets or capillary tubes. Fenced populations of voles may be used effectively to conduct field bioassays during low years in vole cycles. Variations of release devices (with this stoat scent mixture) based on rubber septa for broadcast application to depress vole population density and survival, and plastic rope attached to individual trees to generate an avoidance response, should be used for forest and agricultural crop protection.     

Electroantennogram responses ofHyles lineata (Sphingidae: Lepidoptera) to volatile compounds fromClarkia breweri (Onagraceae) and other moth-pollinated flowers

Electroantennograms (EAGs) from field-collectedHyles lineata moths were recorded in response to 10 individual floral volatiles identified fromClarkia breweri (Onagraceae), to 22 scent compounds produced by other moth-pollinated flowers and to eight ubiquitous green leaf volatiles. Females' EAGs were generally 1.5- to 2-fold greater than those observed for male moths. Female:male EAG rank orders were significantly correlated, but marked differences in order were observed for some compounds (e.g., benzyl alcohol, cinnamic aldehyde, geraniol, and linalool). Linalool, benzyl acetate, methyl salicylate, and pyranoid linalool oxide elicited the largest EAG responses (–1.2 to –0.8 mV) among scent compounds fromC. breweri. EAG responses were significantly lower for monoterpenes as a pooled compound class than for aromatic esters, alcohols and aldehydes, fatty acid derivatives, N-bearing compounds and oxygenated terpenoids. EAG responses to structurally related scent compounds were not significantly different in most cases. Both male and femaleH. lineata were sensitive to mostC. breweri scent compounds at 10^–2 to 10^–4 µg/µl doses, and rank order in potency varied with the dose/concentration tested.H. lineata's olfactory sensitivity to diverse volatile compounds across a range of doses/concentrations suggests that a broad array of volatiles could function as floral attractants for foraging hawkmoths.     

Partial chemical characterization of urinary signaling pheromone in tree shrews (Tupaia belangen)

Tree shrews of both sexes exhibit marking behavior (chinning) in response to scent marks made by the urine of fertile male conspecifics. To isolate the effective odor components, the urine was fractionated by liquid-liquid extraction and TLC, and the fractions were tested by bioassay. The results show that chinning is elicited by several lipophilic urine fractions, which are more effective in combination than alone. To characterize the complex scent signal, the lipophilic extracts from urine of the two sexes were analyzed by GC-MS and compared. The GC profile of the males is distinguished by pyrazine compounds not detected in the profile of the females. The profiles of the sexes also differ with regard to several volatile monocarboxylic acids, which are present at higher concentrations in male than in female urine. More than 30 urine components have been identified. Synthetic equivalents of these urine components were bioassayed for effectiveness in eliciting chinning and compared with one another as well as with scent substances not normally present in tree-shrew urine. Strong chinning responses were elicited by (1) certain pyrazine compounds and (2) some monocarboxylic acids, when presented at the high concentrations specific to male urine. Marking behavior is usually not elicited by scent substances not contained in tree-shrew urine or by urine components common to mammals in general. The data so far available indicate that the male-specific scent signal of tree shrews is based less on a single unique component than on the qualitative and quantitative characteristics of a multicomponent mixture. In the bioassay, tree shrews of both sexes respond equally to the male specific substances by chinning. As the scent signal represented by these substances has a different meaning to males and females (rival or potential mate, respectively), chinning probably serves several different functions.     

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.     

Laboratory Evaluation of Predator Odors for Eliciting an Avoidance Response in Roof Rats (Rattus rattus)

We evaluated eight synthetic predator odors and mongoose (Herpestes auropunctatus) feces for eliciting avoidance responses and/or reduced feeding by wild captured Hawaiian roof rats (Rattus rattus). In a bioassay arena, we recorded: (1) time until each rat entered the arena, (2) time elapsed until first eating bout, (3) time spent in each half of the arena, (4) number of eating bouts, and (5) consumption. Rats displayed a response to the predator odors in terms of increased elapsed time before initial arena entry and initial eating bout, a lower number of eating bouts, and less food consumption than in the respective control groups. The odor that produced the greatest differences in response relative to the control group was 3,3-dimethyl-1,2-dithiolane [from red fox (Vulpes vulpes) feces and mustelid anal scent gland]. Mongoose fecal odor produced different responses in four of the five variables measured while (E,Z)-2,4,5-trimethyl-³-thiazoIine (red fox feces) and 4-mercapto-4-methylpentan-2-one (red fox urine and feces) odors were different from the control group in three of the five variables measured. These laboratory responses suggest that wild Hawaiian roof rats avoid predator odors.     

Can social bees be influenced to choose a specific feeding station by adding the scent of the station to the hive air?

The behavioral response of honeybees (Apis mellifera L.) and bumblebees (Bombus terrestris L.) to the flower volatiles 2-ethyl-1-hexanol and myrcene isolated in situ from white clover (Trifolium repens L.) and oil seed rape (Brassica napus oleifera), respectively, were investigated on a rotating arena with 12 visually identical, but differently scented, feeding stations. When locating a feeding station, neutral in both shape and color, foragers used scent as orientation cue. Introduction of 2-ethyl-1-hexanol to the honeybee hives induced significantly more visits to sites containing this compound. In contrast, introduction of myrcene to the hives did not influence the foraging choices of honeybees significantly. No effect of hive scent composition on the choices made by bumblebees could be detected. Experienced bumble bees, i.e., bees with more than five visits to the feeding stations, tended to visit a particular position on the arena without discriminating between the two volatiles. In contrast, honeybees showed no positioning behavior on the arena, using primarily odoriferous stimuli. The observed influences of addition of scents to the hives are discussed in relation to the general knowledge on foraging behavior of social bees and the emission of volatiles from leaves and flowers.     

Multichemical defense of plant bugHotea gambiae (Westwood) (Heteroptera: Scutelleridae): (E)-2-hexenol from abdominal gland in adults

The occurrence inHotea gambia adults of a sexual dimorphism in the divided dorsal abdominal scent gland (dg 1)is reported. Counts made of ducted secretory units indicate that female dg 1 regresses at the end of larval development, unlike male dg 1 which undergoes no regression. Other dorsal abdominal scent glands (dg 2, dg 3) which function in the larvae cease to function during the imaginai moult. From gas chromatographic, mass spectrometric and [¹H]NMR data, the identity of the secretion from male adult dg 1 was established as virtually pure (E)-2-hexenol (a 100-mg mature male adult contains 0.5–1 l of secretion). 2-Hexenol was also found in the reduced female adult dg 1. In the sexually monomorphic metathoracic scent gland, (E)-2-alkenals (C₆, C₈) and (E)-4-oxohex-2-enal, together with monoterpenes (-pinene, limonene) but not 2-hexenol, were identified. The vapor of (E)-2-hexenol is repellent to both sexes ofHotea adults and toxic to blowfly (Calliphora) eggs.     

Electrophysiological and behavioral responses of female Helicoverpa armigera to compounds identified in flowers of African marigold, Tagetes erecta

Seven electrophysiologically active compounds were detected in air-entrained headspace samples of live flowers of Tagetes erectaanalyzed by gas chromatography (GC) linked to a female Helicoverpa armigeraelectroantennograph (EAG) using polar and nonpolar capillary columns. These compounds were subsequently identified using GC linked to mass spectrometry as benzaldehyde, (S)-(–)-limonene, (R,S)-(±)-linalool, (E)-myroxide, (Z)--ocimene, phenylacetaldehyde, and (R)-(–)-piperitone. Electrophysiological activity was confirmed by EAG with a 1-g dose of each compound on filter paper eliciting EAG responses that were significantly greater than the solvent control response from female moths. Wind-tunnel bioassays with T. erectaheadspace samples, equivalent to 0.4 flower/hr emission from a live flower, elicited a significant increase in the number of upwind approaches from female H. armigerarelative to a solvent control. Similarly, a seven-component synthetic blend of EAG-active compounds identified from T. erectapresented in the same ratio (1.0 : 1.6 : 0.7 : 1.4 : 0.4 : 5.0 : 2.7, respectively) and concentration (7.2 g) as found in the natural sample elicited a significant increase in the number of upwind approaches relative to a solvent control during a 12-min bioassay that was equivalent to that elicited by the natural T. erectafloral volatiles.     

Major component in male sex pheromone of cereal pestEurygaster integriceps puton (Heteroptera: Scutelleridae) identified as a homosesquiterpenoid

A homosesquiterpenoid, (4Z,4E)-4-(1,5-dimethyl-4-heptenylidene)-1-methylcyclohexene, has been identified as a major component of the scent emitted by calling males ofEurygaster integriceps. Minor components of the scent included vanillin. TheE. integriceps male homosesquiterpenoid is an addition to the list of sesquiterpenoids identified as components of male attractant sex pheromones in pentatomoid Heteroptera.