Robert B. Fischer

EVIDENCE OF LATERALITY IN THE LOWLAND GORILLA

The description of hand preference in the primates is at present sadly incomplete. In the lowland gorilla the consistency of the dextral preference across all tests is amazing and comparable to the human data. Similar analysis of the behavior of the orang-utan and a reexamination of the chimpanzee might present a coherent picture of homologous behaviours for the hominoidea.

Female discrimination of male dominance by urine odor cues in hamsters.

Female hamsters have been found to differentially respond to the odors of dominant as opposed to subordinate males. This study reexamined these responses in an olfactometer allowing the females to choose between urinary odors obtained from males differing in dominance status and clean air source. The behavior of the estrous females was consistent with previous research which indicated that such females exhibit a preference for stimuli obtained from dominant males. Contrary to previous findings in a two-choice apparatus, diestrous females failed to prefer the odors of subordinates. These females spent significantly more time in the area infused with unscented air. These data emphasize the importance of odor cues as they relate to male attractivity and possibly mate choice. They also underscore the need to allow animals to avoid conspecific odors in order to reduce the possibility of forcing animals into an unrealistic choice situation.

The ability of females to predict male status via urinary odors

In an earlier study, estrous female hamsters were found to prefer the urinary odors of dominant males. This study investigated whether estrous females would exhibit preferential responding to randomly chosen, socially naive males before dominance testing occurred. Estrous females were indeed found to exhibit such preferences. Such discriminative abilities are discussed with reference to adaptive mating strategies for females.

Responses to conspecifics' urine by the degu (Octodon degus)

In nature the degu has been observed to deposit and to investigate scents. This study employed a captive group of these animals to investigate their responses to conspecific urinary marks in a neutral arena. Both sex classes served as subjects. They were presented with urine obtained from males, from females and a saline control. The females were found to be more active in responding. On the basis of sniffing frequency, they exhibited greater discriminative abilities than did the males. The urine from female donors was sniffed more frequently by all subjects. The frequency of approaching a mark and the time spent in the vicinity of a stimulus are interpreted as being investigatory responses. It seems that the marks deposited by females have a greater salience and that females are more sensitive to olfactory stimuli.

Preferences for salivary odor cues by female hamsters

There is a growing body of data which indicates that saliva may function as a chemosignal in mammals. The salience of this cue in hamsters is investigated. Twelve females were tested in a four-choice olfactorium to determine whether the subjects could differentiate and demonstrate a preference for salivary cues as a function of the dominance status of the stimulus donors and the subjects estrous state. Clear differences in responding were found for estrous as opposed to diestrous females. Estrous females detected and exhibited a preference for male stimuli on the basis of entry and approach measures. Subjects were also found to exhibit sniffing preferences for male odors and possible an avoidance of female odors relative to the saline control. Estrous females appeared to be unable to distinguish between dominant and subordinate males.

The influence of a male's dominance status on female choice in Syrian hamsters

This study evaluated the importance of dominance status on mate selection in Syrian hamsters. In one experiment, sexually receptive females were allowed to choose between tethered males which differed in status. The choice was consistently in favor of the dominant male. The female spent more time in lordosis in the presence of the dominant male. The dominant also obtained a significantly greater number of intromissions. A second experiment investigated whether prior familiarization was essential to permit a female to express mating preferences in a situation where she was free to interact with three males. Again, the dominants were most often preferred and obtained greater sexual access to the female. Prior familiarization or extensive contact with the males was not necessary to support the females selection of the dominant as a mating partner. The choice occurred quickly, generally within 5 min after contacting the males. Although females did mate with the subordinates, this typically occurred late in the tests. The significance of these data with respect to mate choice and probable paternity effects are discussed.

Sex differences during initial social contact in the degu (Octodon degus ).

The degu is a hystricomorph rodent endemic to South America. Initial social interactions between like-sexed pairs in a neutral area were found to be heavily influenced by sex-class membership. Twelve of fifteen behavioral categories were differentiated on the basis of sex-class. Descriptive factor loadings indicated that social contact was facilitated in females via olfactory investigation. In males, social avoidance or spacing behaviors were characteristic. In both sexes, scent marking and olfactory investigation was prevalent. These data serve to expand our knowledge of the behavior of this social rodent, and to document the sexual dimorphism evident in early social activities.Robert B. Fischer, Sandra L. Smith, Pamela J. White, and Gary F. Meunier, 1986. Sex differences durina initial social contact in the degu (Octodon degus). --Behav.Processes 12: 67-76. The degu is a hystricomorph rodent endemic to South America. Initial social interactions between like-sexed pairs in a neutral area were found to be heavily influenced by sex-class membership. Twelve of fifteen behavicral categories were differentiated on the basis of sex-class. Descriptive factor loadings indicated that social contact was facilitated in females via olfactory investigation. In males, social avoidance or spacing behdviors were characteristic. In both sexes, scent marking and olfactory investigation was prevalent. These data serve to expand our knowledge of the behavior of this social rodent, and to document the sexual dimorphism evident in early social activities. INTRODUCTION The hystricomorphs appear to exhibit a nigh degree of variability in their social behaviors (Rood, 1972; Kleiman, 1974; Lather, 1981). Some species (e.g., Kerodon) appear to be extremely social whereas others (e.g., Galela) -appear to be much more intolerant of social contact. Substantial sex differences in social behaviors have been documented between and, in some cases, within species (Rood, 1972; Fulk, 1976; Lather, 1981). The degu (Figure 1. An adult degu) is a moderately sized (200 to 300 g) hystricomorph rodent endemic to central Chile and southern Peru (Cendrero cited in Woods & Boraker, 1975; Walker, 1968). The species lives in colonies, forms extended family groups (Wilson & Kleiman, 1974), exhibits little sexual dimorphism, and may on occasion share its rather extensive burrow system with nonconspecifics (e.g., Abrocoma the Chinchilla rats; Walker, 1968; Fulk, 1976). Degus are primarily terrestrial and employ scent mounds and chemosignallicg extensively in their social communication (Fulk, 1976). They have a rather long gestation period (90 days), no regular estrous cycle and give birth to precocial offspring (Weir, 1970). There are indications that captive degu males may be more likely to respond to social interactions with agonism (Kleiman, 1975), whereas females may be more 0376-6357/86/

DISCRIMINATION OF SALIVARY OLFACTANTS BY MALE MESOCRICETUS AURATUS

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A possible role for Syrian hamster, Mesocricetus auratus, vaginal secretion in inter-female competition

Salivary secretions of rodents have been observed to play an important role during various developmental periods. The present study examined the nature of adult salivary olfactants in regard to behavioral interactions. The ability of 12 adult male hamsters to detect and respond differentially to salivary stimuli from dominant and submissive males and a diestrous female was assessed. Air-borne stimuli were injected into an open-field, free-choice arena. Male hamsters responded differentially to stimuli as a function of their relative dominant status. Dominants responded to the odors of other males, particularly dominants. Submissives showed no specific preference, though like the dominant animals discriminated conspecific saliva from a saline control. The specificity of responding by dominant versus submissive animals as well as the possible roles of saliva in rodent behavior is discussed.

Vaginal secretions increase the likelihood of intermale aggression in Syrian hamsters

Abstract The ability of the vaginal secretions of hamsters to facilitate spacing among conspecific females was examined in three experiments. In the first study, vaginal substances were applied to one half of a testing arena. Naive females placed into this apparatus spent significantly more time on the clean side and tended to deposit vaginal secretions in this area more often. In the second experiment, vaginal odours were again applied to the testing arena. The donor of the secretion and a second female were then introduced into the arena and allowed to interact. The females whose odours had been applied in the arena were significantly more aggressive. The third study evaluated the effectiveness of vaginal odours to reverse a recently established dominance relationship between female pairs. In eight of 12 pairs, a reversal was observed if the previously subordinate hamsters odours were present in the testing enclosure during the second dominance determination. The results of these studies indicate that vaginal marks could serve to space females in the native habitat. These substances are capable of inducing avoidance of a scented area and influencing the outcome of dominance contests.