Scent mound, beaver

FIGURE 6.10 A giant beaver scent mound. (Vertical kitchen knife, center, for scale). (Photograph D. Muller-Schwarze.)... 

In our study, the seasonality of beavers scent mounding behavior did not significantly affect the response of the subject. This is most likely due to the fact that we started the experiment in June and successfully avoided the peak of the scent mounding activity. Hence, between-trial habituation did not occur, although within-trial habituation may be likely, especially for castoreum (Sun and Miiller-Schwaize, 1998a). Thus, it is legitimate to use ta from the first night of each trial in the analysis for the main effects of taxon and secretion type. 

Houlihan, P. W. (1989). Scent mounding by beaver (Castor canadensis) functional and semiochemical aspects. M. Sc. Thesis, State University of New York, College of Environmental Science and Eorestry, Syracuse, New York. 

Svendsen., G. E. (1980). Patterns of scent-mounding in a population of beaver [Castor canadensis). Journal of Chemical Ecology 6,133-148. 

Left an unusually large scent mound buUt by beavers. Right Application of a scent sample to the cork on an experimental scent mound... 

Beaver scent marking. Top Beaver approaches, then sniffs the experimental scent mound. Middle Beaver scratches experimental scent mound with forepaws, then straddles and marks it. Bottom Beaver leaves the scent mound and swims away... 

Carefully walk around a pond, especially near lodge and dam. Look for scent mounds. These are little piles of mud at the water s edge that smell more or less strongly like beaver castoreum, depending on the time since marking. 

Does the number of scent mounds support the notion of a correlation of marking frequency and population density Population density here means nnmber of other beaver colonies within a 5 km radius, or within 5 km upstream and downstream. 

We can observe their behavior directly or check later for any changes at the scent mounds made by the beavers. The first can be difficult because the animals are very sensitive to disturbances such as the presence of humans especially in groups. 

In the afternoon or early evening before the beavers emerge from their lodge, build a scent mound from mud, scooped up from the pond, just as the beavers do. Use a little garden trowel, or in a pinch, a plastic tub. Wear rubber or plastic gloves to avoid contamination with human scent. About 1 1 of mud suffices. Place the scent sample on top of the scent mound. If you use commercial, dried, and ground beaver castoreum, sprinkle a teaspoon full over the mud. For dissolved scent samples, place a large cork or bottle cap on scent mound. 

On the next day, check for changes at scent mounds cork removed mud mound disturbed (scratched apart) new mud added fresh, strong smell additional nearby scent mounds built by beavers overnight. 

If a wildlife trail camera (camera trap) is available, set it up near the experimental scent mounds to record visits by beavers during the night. 

In this study, we mimicked beavers natural scent mound building behavior to examine whether beavers can discriminate between species or subspecies through an olfactory playback experiment. If this discrimination does occur, we predict that beavers should respond more strongly toward individuals of sympatric conspecifics than those of allopatric conspecifics or heterospecifics. 

Beavers live in family units that are usually composed of a mated pair, yearlings, and kits. They occupy and defend territories (Schulte, 1993). Beavers rely heavily on chemical signals for social interaction and recognition. They use anal gland secretion (AGS) and castoreum to communicate many types of information, including family membership, kinship, sex, individuality, and territoriality (Svendsen, 1980 Sun and Miiller-Schwarze, 1997 Schulte, 1998). To do these, they build scent mounds on the bank, within 2 meters from the water, in areas of high activity around their territory, and then apply castoreum and/or AGS to the top (Svendsen, 1978, 1980 Rosell and Nolet, 1997 Rosell and Sundsdal, 2001). 

Scent mound construction in beavers shows a seasonal pattern. Because it is most intense from April to June, and gradually tapers off (Svendsen 1980), our study started in June to avoid this seasonal effect in beaver mound construction and response. A total of 108 nights of data were collected from June to November in 1998. Five of the families were tested with two to three (6-night) trials and three of the families were used in one trial. Because of this inconsistency, we included only data from the first trial for each family. Because there were many nights that beavers did not respond, we only include data with a minimal response frequency of 40% as measured by the category ESM Responded for data analysis to avoid these blanks. Families that were used in more than one trial were given at least three weeks off between trials to avoid possible habituation from repeated use (Sun and Muller-Schwarze, 1997). 

The total number of observation nights was 162 (castoreum 78 anal gland secretion 84). Beavers responded (any kind of alteration to the experimental scent mounds) to male castoreum in 31 % of the cases, and to female castoreum in 26 %. The difference was not significant = 0.205, d.f. = 1, P > 0.50). Nor did we find that beavers showed any difference in response to male and female anal gland secretion samples (male 46% female 39%, = 0.347, d.f. = 1, P > 0.50). To examine any likely subtle differences in... 

In the second phase of the odor response, the beaver left the water, walked slowly to the scent pile, and sniffed it, with its nose 5 cm or less from the sample. After sniffing, the beaver pawed the mudpile with its front feet, usually flattening it, then stepped forward, straddled the mud-pile, and rubbed its cloacal area over the mud. During this movement, secretions of the castor sacs and anal glands are applied to the substrate. Having thus scent marked the experimental mudpile, the beaver walked from the pile toward the water, slid into the pond, and swam away. With many samples, the beaver did not return after one bout of activity at the experimental scent mound, but other samples attracted several beaver or the same beaver several times. The most intense response consisted of 19 land visits by various members of the colony. 

Recently, Rosell and Sundsdal [78] tentatively identified 21 of the 43 constituents present in 96 scent marks deposited directly on snow or ice mounds by the Eurasian beaver, C. fiber. In this study, a higher final oven temperature was employed and several steroids were eluted from the capillary column. Because the main focus of this study was to determine whether the beaver uses castoreum and/or anal gland secretion for scent marking and not the full chem-... 

Within the chemical modality, conspicuousness of a signal increases by an expanding the active space or by placing it in the path of, and/or at the level of the sniffing animal, as in the hippopotamus. In contrast to the previous examples, no specially evolved visual or auditory components need be involved. For instance, beavers increase the active space of their scent marks by elevating them on mounds they construct from mud dug up from the bottom of their pond. Muskrats and river otter place their fecal marks at prominent spots along trails where encounters with conspecifics are likely. 

Animal responses to artificial scent marks created by the investigator also can be monitored. Svendsen and Huntsman (1988) treated mounds of mud and debris along a stream with fractions of beaver castoreum. Only beavers that swam within 10 m of these mounds were included in the study. Stimuli were considered active if a beaver made a detectable change in direction or altered its behavior in relation to it. A similar approach has been used to assess woodchuck responses to oral-gland scents (Meier 1991). Scents were applied to cotton balls affixed to stakes near the entrance of an occupied burrow. 

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