Pheromonal activity of single castoreum constituents in beaver,Castor canadensis

Behavioral activity of single components of beaver castoreum was demonstrated for the first time. In four experiments samples were presented to free-ranging beaver in their family territories. First, responses to whole castoreum and anal gland secretion (AGS) from males and females were tested. Second, 24 compounds, known to be constituents of beaver castoreum, were individually screened for activity. Four of these consistently released immediate responses during the observation periods. These are the phenols 4-ethylphenol and 1,2-dihydroxybenzene and the ketones acetophenone and 3-hydroxyacetophenone. In the most complete responses, the beaver sniffed from the water, were attracted to the odor, swam toward its source, went on land, and then approached, sniffed, pawed, and scent-marked the artificial scent mound. 4-Ethoxyphenol, a compound not yet found in castoreum, also released these responses. Five additional compounds resulted in a few delayed visits to the samples during the night following the observations, as evidenced by destroyed scent mounds. These are 4-methyl-1,2-dihydroxybenzene, 4-methoxyacetophenone, 5-methoxysalicylic acid, salicylaldehyde, and 3-hydroxybenzoic acid. Third, mixtures of 24 and six compounds were tested. Responses to these mixtures could be as strong as those to whole castoreum. Fourth, the four regularly active compounds were tested in two additional beaver populations and proved to be active there, too. The response was strongest in the densest beaver population.     

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.     

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.     

Red maple (Acer rubrum) inhibits feeding by beaver (Castor canadensis)

At many beaver (Castor canadensis) sites at Allegany State Park in New York State, red maple (Acer rubrum) is the only or one of the few tree species left standing at the ponds' edges. The relative palatability of red maple (RM) was studied in three ways. (1) At seven beaver sites, the available and utilized trees were recorded and an electivity index (E) computed. Of 15 tree species, RM ranked second or fourth lowest. (2) In experiment I, RM, sugar maple (A. saccharum, SM), and quaking aspen (Populus tremuloides) logs were presented cafeteria style at 10 colonies. RM was the least preferred. (3) Bark of RM was extracted with solvents. Aspen logs were painted (experiment II) or soaked (experiment III) with this RM extract and presented to beaver cafeteria-style, along with aspen and RM controls. This treatment rendered aspen logs less palatable, indicating that a chemical factor had been transferred.     

Patterns of scent-mounding in a population of beaver (Castor canadensis)

The frequency and pattern of distribution of scent-mound construction were studied in a population of beaver in southeast Ohio from 1975 through 1977. The study addressed the questions of whether or not the frequency of scent-mound construction varied with season, site, year, and degree of contact with other family groups, and whether the pattern of scent-mounding activity was parsimonious with the idea of territorial marking. The number of scent-mounds constructed was determined weekly for each site throughout the ice-free season. Scent-mounding activity was highest in spring and declined and remained low during summer and fall. Significant differences were found amoung sites and over years. Contact with other resident family groups altered both frequency and pattern of scent-mound construction. Scent-mounds did not conform to a scent-fence model. The most parsimonious interpretation of function of odor cues deposited on scent-mounds is the effect on the motivational state of residents and nonresidents, increasing the confidence and reducing anxiety in residents smelling their own scent-mound and decreasing the confidence and increasing the readiness to flee in trespassers encountering a strange scent-mound.     

Responses of beaver (Castor canadensis Kuhl) to predator chemicals

Free-ranging beaver (Castor canadensis) in two different beaver populations in New York State were exposed to predator chemicals to test feeding inhibition. Solvent extracts of feces were applied to stem sections of aspen, the preferred food tree of beavers, permitting smelling and tasting the samples. Predator odors were from wolf (Canis lupus), coyote (Canis latrans), dog (Canis familiaris), black bear (Ursus americanus), river otter (Lutra canadensis), lynx (Lynx canadensis), and African lion (Panthera leo). The experiment was repeated. The predator odors reduced feeding compared to untreated or solvent-treated controls. One population consumed 17.0% of the samples with predator odor and 27.0% of the controls in summer, and 48.4% and 60.0%, respectively, in autumn. The other population accepted 3.15% of the predator odor samples and 11.05% of the controls in summer. Coyote, lynx, and river otter odors had the strongest effects. Diesel oil and bitter-tasting neem extract had weaker effects. Predator odors are promising as feeding repellents for beaver.     

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.     

Bacterial contents of the anal and castor glands of beaver (Castor canadensis)

Bacterial contents of both the anal gland and castor gland of the beaver (Castor canadensis) were determined. Using our culture methods, no bacteria were isolated from the castor glands, but the anal gland contained high numbers of the aerobeEscherichia coli and the anaerobeBacteroides fragilis. The latter may be represented by several variants but facilities were not available for advanced anaerobic analysis. The relative numbers of each bacterial group and the group present were constant regardless of sex, age class, or colony of beaver. The bacterial fermentation hypothesis is rejected for castor gland section but remains possible for anal gland secretions based on variations seen inB. fragilis. The role of the products of both the castor gland and anal gland are discussed in relationship to scent communication in beaver.     

Beaver (Castor canadensis) responses to major phenolic and neutral compounds in castoreum

North American beaver (Castor canadensis) mark their territories with castoreum, a chemically complex secretion from their castor sacs. The phenolic and neutral fractions of castoreum have been shown to elicit specific behavioral responses from beavers in a field setting. Our objective was to identify compounds/mixtures that evoked responses similar to those stimulated by castoreum. We assayed recently identified phenolic compounds, some phenolics that had been determined to be biologically active in previous studies, the neutral compound borneol, and combinations of phenolic compounds, neutral compounds, and the two combined. Biological activity was measured by the elicitation and extent of specific responses and their strength (duration, frequency, and proportion of beavers responding). Generally, single compounds stimulated fewer responses than mixtures. A 26-compound mixture of phenolic and neutral compounds elicited responses in a similar proportion of trials as castoreum. However, responses to castoreum were stronger than to any synthetic sample. Further investigation of different measures of response, namely, elicitation, completeness, and strength, are deemed necessary to fully decipher the design of social odors.     

Bioactivity of beaver castoreum constituents using principal components analysis

North American beaver (Castor canadensis) were observed to sniff from the water and make land visits to some synthetic chemical components of castoreum placed on experimental scent mounds (ESM). In previous analysis, the elicitation (presence/absence), completeness, and/or strength (number, duration) of these key responses served as separate measures of biological activity. In this paper, we used principal components analysis (PCA) to combine linearly six related measures of observed response and one index of overnight visitation calculated over all trials. The first principal component accounted for a majority of the variation and allowed ranking of the samples based on their composite bioactivity. A second PCA, based only on response trials (excluding trials with no responses), showed that responses to the synthetic samples, once elicited, did not vary greatly in completeness or strength. None of the samples evoked responses as complete or strong as the castoreum control. Castoreum also elicited more multiple land visits (repeated visits to the ESM by the same individual or by more than one family member) than the synthetic samples, indicating that an understanding of the castoreum chemosignal requires consideration of responses by the family unit, and not just the land visit by the initial responder.     

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.     

Scent-Marking in the Eurasian Beaver (Castor fiber) as a Means of Territory Defense

Beaver (Castor spp.) normally scent-mark by depositing castoreum and/or anal gland secretion on scent mounds close to the water's edge. The aim of this study was to investigate the hypothesis that the Eurasian beaver (C. fiber) scent-marks as a means of territory defense. Scent-marking behavior was studied during an entire year (April 1, 1995–March 31, 1996) in seven adjacent territories along 9.2 km of the B River in Telemark County, Norway. The number and location of fresh scent marks were recorded biweekly. The main results showed that: (1) the number of scent marks in territories was significantly higher in spring, when dispersal of subadults normally occurs than during the rest of the year; (2) the number of scent marks was clumped near territorial borders; and (3) the number of scent marks was significantly greater upstream than downstream of the lodge.     

Olfactory recognition of individuals by male cavies (Cavia aperea)

In one study, using a habituation procedure, male South American cavies,Cavia aperea, distinguished individual differences in odors collected from three sources: perineal gland secretions, urine, and supracaudal gland secretions. In a second study, male cavies spent more noninvestigatory time and rested more on the side of a cage containing the odor of a familiar subordinate male as compared to the cage side containing the odor of a familiar dominant male. Since the odor source was a glass plate which had been left in the home cage of the donor males for three days, the actual odorous cue to which the test males responded is not known. These studies demonstrate that male cavies distinguish odors of individuals, that individual differences in odors are found in at least three different sources, and that cavies use chemical cues to distinguish between known individuals.     

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.     

Scent trailing by virgin females ofPseudococcm calceolariae

Virgin females of the citrophilous mealybugPseudococcus calceolariae (Mask.) deposit scent marks as trails on the substrate on which they rest or move. These substances elicit attraction and sexual behavior by conspecific males. The same responses were obtained when males were bioassayed on extracts from filter paper disks on which females had rested. The significance of scent trailing in mealybugs is discussed.Homoptera, Coccoidea, Pseudococcidae.This work was supported by the Italian National Research Council (CNR).     

Aversive responses of white-tailed deer,Odocoileus virginianus,to predator urines

We tested whether predator odors could reduce winter browsing of woody plants by white-tailed deer (Odocoileus virginianus). Urine from bobcats (Lyra rufus) and coyotes (Canis latrans) significantly reduced browsing of Japanese yews (Taxus cuspidata), and repellency was enhanced when urine was reapplied weekly as a topical spray. Urine of cottontail rabbits (Sylvilagus floridanus) and humans did not reduce damage, suggesting that deer do not respond aversively to odors of nonpredatory mammals or occasional predators with which they lack a long evolutionary association. Bobcat and coyote urine were more effective in tests conducted with eastern hemlock (Tsuga canadensis), which is less palatable to white-tailed deer than Japanese yew. A dichloromethane extract of bobcat urine was as effective as unextracted urine in reducing damage to hemlocks. Testing of the organic components of bobcat urine, particularly the volatile components, may enable identification of the compounds responsible for the repellency we observed.     

Volatile compounds released by disturbed and calm adults of the tarnished plant bug,Lygus lineolaris

Volatile compounds released by disturbed and calm female and male Lygus lineolaris were collected and analyzed. Six major compounds were present in samples from disturbed bugs and from calm females: (E)-2-hexenal, 1-hexanol, (E)-2-hexenol, hexyl butyrate, (E)-2-hexenyl butyrate, and (E)-2,4-oxohexenal. (E)-2-hexenal was lacking in volatiles collected from calm males. Hexyl butyrate accounted for approximately 68% and 66% of volatiles released by agitated and calm females, and 87% and 88% of volatiles released by agitated and calm males, respectively. Blends released by disturbed insects differed quantitatively from blends released by calm insects, with amounts of compounds increasing 75–350 times in samples from disturbed insects. In static air bioassays, both females and males were repelled by natural volatiles collected from females and by five-component [(E)-2,4-oxohexenal excluded] and six-component synthetic blends at doses of 1 and 10 bug-hours, indicating that these volatiles may serve an alarm or epideictic function, as well as a possible role as defensive allomones. Adults also avoided hexyl butyrate, (E)-2-hexenyl butyrate, (E)-2-hexenol, and (E)-2,4-oxohexenal, but not 1-hexanol and (E)-2-hexenal when compounds were assayed individually in static air bioassays at doses equal to 1 bug-hour. When tested over 1 day in two-choice cage trials, adults did not prefer untreated bean plants over bean plants surrounded by vials releasing up to 8.1 mg/hr (=234 bug-hours) of the five-component synthetic blend. Therefore, the volatiles produced by disturbed adults would not be useful as a repellent for L. lineolaris.     

(S)-2,3-Dihydrofarnesoic Acid, a New Component in Cephalic Glands of Male European Beewolves Philanthus triangulum

The chemical composition and functional significance of pheromones of solitary Hymenoptera is much less well known compared to social species. Males of the genus Philanthus (Sphecidae) are territorial and scent mark their territories to attract females. Because of inconsistent results of earlier studies, we reanalyzed the content of the cephalic glands of male European beewolves, Philanthus triangulum F. Besides a variety of alkanes and alkenes, four major compounds were found. Two of these, (Z)-11-eicosen-1-ol and (Z)-10-nonadecen-2-one, had been previously described as constituents of the cephalic glands. We identified 1-octadecanol as a new component of the cephalic gland, and a fourth compound, enantiopure (S)-2,3-dihydrofarnesoic acid, was identified for the first time in nature. Structural elucidation and enantiomeric analysis were performed by HRGC-MS and HRGC-FTIR as well as enantioselective gas chromatography and by means of authentic reference compounds. Occurrence and