Over-marking

Fig. 8.2 Mean response frequency or duration by (a-c) female, F, and (d-f) male, M, L. catta to conspecific glandular secretions, (a) F sniffing all odorants as a function of her reproductive state (breed > non F 3 =28.57, P =0.013 ). (b) F licking labial odorant as a function of the donors reproductive state (breed > non t =3.00, P= 0.58, n.s.). (c) F frequency and site-specificity of scent marking as a function of odorant type Fs counter marked the unscented dowel in response to scrotal scent, but over-marked scented dowels in response to labial scent (ti = 3.87, P =0.030 ). (d) M response as a function of odorant type (antebrachial was sniffed least = 6.75, P = 0.011 brachial was wrist marked most Fs = 7.16, P = 0.009 ). (e) M...

Johnston, R.E., Chiang, G. and Tung, C. (1994) The information in scent over-marks of golden hamsters. Anim. Behav. 48, 323-330. 

Cohen, A.B., Johnston, R. and Kwon, A. (2001) How golden hamsters (Mesocricetus auratus) discriminate top from bottom flank scents in over marks. J. Comp. Psychol. 115, 241-247. 

Domestic female rabbits mark more when in estrus and prefer to over-mark scent marks by males. They also prefer to mark over chin marks, as opposed to urine and control odors, and prefer to over-mark chin marks from donors living in a long daylight cycle over those from short-day animals (Hudson and Vodermayer, 1992). 

Johnston, R.E., Sorokin, E.S. Ferkin, M.H. 1997b. Female voles discriminate males over-marks and prefer top-scent males. Anim. Behav., 54, 679—690. 

Scent over-marking is a specialized type of marking behavior in which one individual places its scent so that it covers or partially covers previously deposited scents of conspeci-fics. In this chapter I first review our research that shows that golden hamsters have amazing abilities to analyze such over-marks to determine which individual s scent is on top. Next I present experiments in which we examine how they do this. Finally, I briefly discuss the functions of over-marking and of the abilities to determine the top-scent individual. 

One especially interesting type of scent marking is over-marking, in which one animal marks on top of a scent deposited previously by another individual of the same spe-... 

I first review experiments showing that hamsters and voles have the previously unsuspected ability to determine which of two individual s scent marks is on top in an overmark and then present experiments that investigate how they do this. At the end I speculate on the functions of these abilities and of over-marking. 

SPECIALIZED MECHANISMS FOR EVALUATION OF SCENT OVER-MARKS... 

Several years ago, in an attempt to develop a theoretical and experimental approach to scent over-marking, I distinguished three types of information that conspecifics might... 

The first set of experiments with hamsters suggested that scent masking had occurred. After hamsters investigated (on 5 separate trials) a scent over-mark in which the top scent of one individual covered the bottom scent of another individual, they investigated the top scent of the mark less than a novel scent, indicating memory for the top scent, but they investigated the bottom scent the same amount as a novel scent, suggesting that they did not remember the bottom scent (Johnston et al., 1994). That is, these results supported the hypothesis that the top scent masks information in the bottom scent. 

Because we observed that hamsters rarely completely covered the scent of another, we then examined what perceivers remembered after investigation of partially overlapping scent marks of two individuals (which we presented in a crossed pattern). To our surprise, we found the same effect as in the first set of experiments that is, subjects showed evidence of remembering just the top scent of the over-mark, even though they did investigate the uncovered parts of the bottom individual s odor (Johnston et al., 1995). These... 

SENSORY EVALUATION OF SCENT OVER-MARKS HOW DO HAMSTERS TELL WHICH SCENT IS ON TOP ... 

If one individual deposits a scent mark on top of the mark of another individual, then the top scent is necessarily fresher (more recent) than the scent that was deposited first. Thus, relative scent age is one way that mammals (or other species) could evaluate scent over-marks to determine which animal had marked most recently. The hypothesis that mammals use scent age as the relevant cue is attractive because it is already known that changes in odor quality may provide information about scent age. Although there has been little research that demonstrates how individuals of any species perceive or use this information, it is clear that some rodents respond differently to fresher versus older scents (Johnston Lee, 1976 Johnston Schmidt, 1979 Wellington et al., 1981 Ferkin et al., 1995a). There is also evidence suggesting that dogs may be able to determine the direction of a human scent trail by differences in scent quality due to differences in age of footprints along the trail (Steen Wilsson, 1990). 

Does the Spatial Configuration of Scent Over-Marks Provide Cues That Result in Preferential Memory for the Top Scent ... 

One of the cues used by the visual system for perception of depth or relative distance of two objects from the observer is occlusion. That is, if one object occludes a second object, it is perceived as being in front of that second object. Many vaginal marks of hamsters are deposited as linear streaks or lines, and we hypothesized that hamsters might be able to use olfactory occlusion to determine which scent was on top. That is, in an over-mark the top scent is a continuous streak if it masks the bottom mark in the region of overlap, the underlying scent mark will appear to be discontinuous (interrupted). If hamsters can keep track of the spatial layout of the two scents they could potentially use this continuous versus interrupted information as a means to determine which individual s scent is on top, and thus preferentially remember the top scent. 

Our approach to this question was to design configurations of scent over-marks that would provide an area of overlap of two scents but that would not provide relevant spatial information about which scent mark was deposited first. One such experiment is summa-... 

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