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.     

Increased scent marking in male Mongolian gerbils by urinary polypeptides of female conspecifics

Male Mongolian gerbils scent mark during a standardized openfield test on an individually different but more-or-less constant level in the absence of females. The presence of females in the same room but without direct contact to the males increases the marking frequencies of the males to an individually different higher level. A similar increase in marking frequency is obtained by application of female urine directly to the nostrils of the males, but not by male gerbil urine or female laboratory mouse urine. This indicates that substances present in female gerbil urine are responsible for the increase in male marking behavior. Using this bioassay, various fractions of female urine were tested for their influence on marking behavior. Our results to date show that the component increasing male scent-marking behavior is hydrophilic and nonvolatile and is contained in the nondialyzable, high-molecular-weight polypeptide fraction of female gerbil urine.     

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.     

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.     

White adipose tissue fatty acids of alpine marmots during their yearly cycle

Alpine marmots (Marmota marmota) were maintained on a laboratory diet, and the fatty acid composition of gonadal and subcutaneous whilte adipose tissues (WAT) was studied during a yearly cycle. Fatty acids (FA) released from isolated adipocytes were also identified after stimulation of in vitro lipolysis. Analysis of the FA composition of WAT depots showed that marmot WAT mainly contained monounsaturated FA(65%, mostly oleic, acid, 18:1n-9) although laboratory food contained 45% of linoleic acid (18:2n-6) and only 21% of 18:1n-9. During stimulated lipolysis, saturated FA were preferentially released from isolated adipocytes whereas unsaturated FAs were retained. Despite this selective release of FA from isolated WAT cells in vitro, and despite the FA composition of the food, marmots maintained a constant FA composition in both WAT depots throughout the year. Six months of hibernation and fasting as well as an intense feeding period did not affect this composition. The potential adaptive benefit of such regulation of WAT composition, based on a high level of monounsaturated FA, might be to maintain fat with appropriate physical properties allowing animals to accommodate to and survive the wide range of body temperatures experienced during hibernation.     

Chemical Characterization of Urinary Pheromones in Brown Antechinus, Antechinus stuartii

In the small dasyurid marsupial, Antechinus stuartii, males exhibit scent-marking in the form of cloacal marking of nesting areas during the breeding season. Females of this species show no such behavior. To characterize the potential male pheromonal scent signal, urine-derived volatiles from sexually active males were analyzed by GC-MS and compared to that of females and a castrated male. More than 10 urinary compounds were identified. A series of homologous methylketones was observed in both males and females, whereas aldehydes were present only in female urine. Urine from the castrate was virtually compound-free except for minute concentrations of a compound tentatively identified as 2,4-dithiapentane. This compound was also found in one of the sexually active males. The GC profiles of the sexually active males contained high concentrations of two pyrazine derivatives and four methylketones that were not detected in the profiles of either females or the castrate. These compounds may influence social communication in the brown antechinus, Antechinus stuartii.     

A Selfish Function of a “Social” Gland? A Postpharyngeal Gland Functions as a Sex Pheromone Reservoir in Males of the Solitary Wasp Philanthus triangulum

The postpharyngeal gland (PPG) has long been assumed to be restricted to ants, where it mainly functions in the maintenance of social integrity. Recently, a PPG has been described in both sexes of a solitary digger wasp, the European beewolf, Philanthus triangulum (Hymenoptera, Crabronidae). Female beewolves use the contents of their PPG to embalm their honeybee prey to delay microbial growth. Here we show that in male beewolves, the PPG serves as a reservoir of the pheromone used to scent-mark their territories. Gas chromatography-mass spectrometry (GC-MS) analysis of PPG contents identified 55 substances including long-chain aliphatic hydrocarbons, and 13 substances with functional groups. The composition was consistent with the composition of the marking pheromone of male European beewolves described earlier. Comparisons of the PPG contents, and total-head extracts showed a strong congruency, suggesting that total-head extracts can be used for the analysis of marking secretion in beewolves. Furthermore, we found a dimorphism in the composition of the PPG contents, based on significant differences in the proportions of seven compounds between the two morphs.     

Behavioral evidence for multicomponent trail pheromone in the termite,Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae)

Evidence is presented for a multicomponent trail pheromone in the eastern subterranean termiteReticulitermes flavipes (Kollar). Choice tests were used to compare strength and persistency of trails made by termites in glass tubes. Tubes connected to termite nests for 24 hr were marked by termites with an extremely long-lasting chemical that persisted for at least one year, and a highly volatile substance that decayed in 15 min. Individual termites varied the trail they deposited under different circumstances. When removed from the nest and placed in a clean tube, they deposited a highly volatile substance. They left stronger and more persistent trails when exploring clean tubes attached to the nest. When they discovered a new food source, they left trails that were more attractive and far more persistent than trails made by exploring or displaced termites. A food trail made by 15 workers was still effective after 24 hr, whereas a trail made by 50 displaced workers, walking one after another through a tube, lasted only 5 min.     

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.     

Investigation of Scents on Cheeks and Foreheads of Large Felines in Connection to the Facial Marking Behavior

We investigated head- and cheek-rubbing behavior in four species of large felines, lions (Leo panther), leopards (Panthera pardus), tigers (Panthera tigris), and cougars (Puma concolor), in captivity. Preliminary behavioral observations found that lions and tigers, but not leopards and cougars, showed behavioral responses to cardboard rubbing samples from head and cheek areas from conspecific felines, compared to the blank cardboard controls. In this context, surface samples on the facial areas of each species were collected to analyze volatile organic compounds that could be involved in the facial marking of felines. Previously developed stir bar surface sampling methodology was used. From all cheek and forehead samples, 100 volatile organic compounds were identified or tentatively identified. Among these, 41 have been previously reported to be present in feline urine and marking secretions. Several new compounds were identified on facial surfaces. Some of the compounds showed substantial quantitative differences among the species. One compound, that has not been reported previously in mammals, 3-acetamidofuran, was found in all investigated species. It was synthesized and tested for behavioral responses. No responses were elicited in a preliminary test. Future research will test other potential signaling compounds and their mixtures for ability to elicit behavioral responses.     

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.     

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.     

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.     

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.     

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.     

Scent Marking, Scent Origin, and Species Specificity in Male Premating Behavior of Two Scandinavian Bumblebees

The marking behavior and the scent-marking compounds in males of two Scandinavian bumblebee species Bombus pratorum and Bombus lapidarius were studied. There are characteristic differences in the behavior and in the chemistry of the two species. Males of B. pratorum scent marked small areas of the edges of birch leaves in a quick and unpredictable manner, depositing farnesol, geranylgeranyl acetate, farnesyl acetate, (Z)-11-octadecanol, hexadecanol, and a pentacosadiene. In B. lapidarius, scent marking on birch leaves was much slower and the entire edge of the leaf was marked with (Z)-9-hexadecenol and hexadecanol. These compounds were also detected in the cephalic portion of the labial gland in males. Thus, males of B. lapidarius produce a blend of fatty acid derivatives while B. pratorum males, in addition to fatty acid derivatives, also produce sesqui- and diterpenes. The total amount of scent compounds per milligram of labial glands was 0.2 μg in B. pratorum and 40 μg in B. lapidarius. Farnesol and farnesyl acetate were detected via headspace collection in the air around leaves marked by B. pratorum and (Z)-9-hexadecenol was detected around leaves marked by B. lapidarius.     

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.     

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.     

扭曲扁管在蒸发器中的运行特性实验研究

对扭曲扁管与普通直管在蒸发器工况下的传热、流动阻力和污垢特性进行了对比实验研究。实验采用45 mm×3 mm的普通直管和由同种直管制成的扭曲扁管,扭曲扁管导程St分别为450,550,650 mm。通过实验,研究了Re和St对各特性的影响。结果表明,在实验Re数条件下,管壁污垢热阻增长呈渐近线型特性,扭曲扁管渐近污垢热阻为直管的0.15—0.29倍,流动阻力系数为直管的1.48—1.63倍。实验还得出,实验扭曲扁管的强化传热作用随着St减小而增大,扭曲扁管的传热系数在洁净状态下为直管的1.29—1.51倍,在运行8 h后,由于扭曲扁管具有较强的抑垢作用,传热系数趋近为直管的1.96—2.79倍。     

Volatile communication substances in Dufour's gland of virgin females and old queens of the antFormica polyctena

Dufour's gland, which is present in worker ants ofFormica polyctena as a tiny gland emptying into the short duct from the poison reservoir, was found to be very enlarged in virgin females. In egg-laying queens the gland lobes were reduced in size to slender tubes. The glandular secretion was analyzed by capillary gas chromatography and mass spectrometry. Seventy-four percent of the gland secretion from virgin females consisted of undecane, but this compound was less than 1% in queens. Decane and nonane, making up 3.5% in virgin females, were not found in queens. About 74% of their secretion consisted of the lower hydrocarbons: tridecane, pentadecane, heptadecane, and a nonadecene with tridecane dominating to 50%. Apart from these characteristic differences, almost the same compounds were present in virgin females and queens. Thirty-three compounds were identified from the secretion of virgin females and 38 from queens. An additional compound present in trace amounts in the secretion from queens has not been identified. All the compounds were hydro-carbons with the exception of dodecanol, present in trace amounts in virgin females. The compounds are homologous series of saturated, aliphatic hydrocarbons from nonane to tricosane and corresponding series of monounsaturated and methyl-branched hydrocarbons. Geranylgeraniol and geranyl-geranyl acetate, present in worker ants together with some other alcohols and acetates, were absent in females.