Male-female interactions across the female estrous cycle: A comparison of two species of dwarf hamster (Phodopus campbelli and Phodopus sungorus).

Recent studies in our laboratory have suggested that monogamy may be the preferred mating system in the Djungarian hamster (Phodopus campbelli), whereas the available evidence for the closely related Siberian hamster (P. sungorus) does not show the same pattern. Here we examine the behavior of male–female dyads of both species interacting during 1-hr tests in large, familiar habitats containing defensible nest boxes, food, and water. Levels of aggression within pairs were low, compared with those seen during brief intrasexual encounters, whereas affiliative behaviors, such as sniffs, were high. P. campbelli scent marked more than twice as frequently as P. sungorus. Females of both species scent marked at a constant rate irrespective of their location in the habitat, whereas males scent marked at a higher rate in the female's home area. Two major features of the copulatory pattern differed between the two species: (a) The duration of the ejaculatory lock was five times longer in P. sungorus than in P. campbelli. (b) Both species had approximately the same number of mounts in each ejaculatory series, but the intromission/mount ratio was significantly higher in P. sungorus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social cues influence foraging in dwarf hamsters (Phodopus campbelli).

In 2 experiments, dwarf hamsters (Phodopus campbelli) were trained to find palatable foods in an open field. The location of each food patch remained the same throughout each experiment, and only 1 food was available per day. Once subjects had been trained to find each food in its unique location, they progressed to a testing phase in which subjects’ mates were allowed to eat and hoard the food that was available in the open field each day. The foods that subjects’ mates brought back to the home cages then served as discriminative stimuli signaling which food could be obtained in the open field. Subjects generally approached the patch containing the food hoarded by their mates, suggesting that dwarf hamster burrows could function as information centers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enduring effects of photoperiod on affective behaviors in Siberian hamsters (Phodopus sungorus).

The effects of perinatal and postweaning photoperiods on subsequent affective behaviors were examined in adult Siberian hamsters (Phodopus sungorus). Hamsters exposed perinatally to short days (8 hr light/day) exhibited mixed results for adult anxiety-like behaviors and increased some depressive-like behaviors compared with hamsters exposed to long days (16 hr light/day). Postweaning exposure to short days increased depressive- and anxiety-like behaviors compared with long days. Sex differences in affective behaviors were observed. These results suggest that anxiety-like behaviors are organized early in life and endure throughout adulthood, and anxiety- and depressive-like behaviors are modified by postweaning photoperiod. The persistence of photoperiod-induced affective behaviors in rodents supports the hypothesis that symptoms of human affective disorders may reflect ancestral adaptations to seasonal environments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social Transmission of Flavor Preferences in Two Species of Hamsters (Mesocricetus auratus and Phodopus campbelli).

Golden hamsters (Mesocricetus auratus) and dwarf hamsters (Phodopus campbelli) interacted with a conspecific demonstrator that had recently consumed a flavored food. When given a choice between their demonstrator's flavor and another flavor, the dwarf hamsters preferred the flavor their demonstrator had eaten. Golden hamsters did not prefer their demonstrators' diets when the demonstrators were unrelated adults or littermates, but they did when the demonstrator was their mother. Videotaping the interactions between demonstrators and observers revealed that adult golden hamsters did not investigate foods hoarded by their demonstrators whereas dwarf hamsters did. These results are interpreted in terms of the stimuli that activate feeding behavior systems in these 2 hamster species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of postweaning social experience on response of Siberian hamsters (Phodopus sungorus sungorus) toward young.

Between 18 and 50 days of age, 83 male and 66 female Siberian hamsters were housed either with (a) same-sex littermates; (b) opposite-sex littermates; (c) opposite-sex littermates and parents; or (d) opposite-sex littermates, parents, and a younger litter. When adults, Ss were presented with 2 3–8 day old pups for 8 hrs, and their responses were recorded. Rearing conditions did not affect behavior of females. Males housed with female littermates in the absence of a younger litter showed fewer pup attacks and more nesting with pups than did males housed only with other males. Thus, housing with females in the early postweaning period may influence males' adult responses toward pups. Only among Ss housed with same-sex littermates did males and females differ in their response to pups, a result emphasizing that sex differences in behavior may depend on early social rearing. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in affiliative behavior, pair bonding, and vaginal cytology in two species of vole (Microtus ochrogaster and M. montanus).

Prairie voles (Microtus ochrogaster) and montane voles (M. montanus) display marked differences in social organization in the field. Trios of 1 male and 2 females were studied in a large enclosure for a 10-day period. Prairie voles spent 59% of the observation time in side-by-side contact, whereas montane voles spent only 7% of the time in contact. Vaginal smears indicated female–female suppression of estrus in prairie voles; female montane voles appeared to cycle in the presence of males. Male prairie voles preferentially paired and nested with 1 of the females, and vaginal estrus generally followed pair formation by 2 days. Male montane voles did not spend time preferentially with either female, even after mating. These results suggest that the contrasting mating systems of these species result from differences in the propensity for affiliative behavior and social bonding rather than from mate availability or female receptivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Configural learning in two species of marsupial (Setonix brachyurus and Sminthopsis crassicaudata).

Four experiments examined the ability of quokkas (Setonix brachyurus) and fat-tailed dunnarts (Sminthopsis crassicaudata) to solve 2 configural tasks: transverse and negative patterning. Transverse patterning requires the simultaneous solution of 3 overlapping discrimination problems (A+B-, B+C-, C+A-). Both species could solve the nonoverlapping (elemental) version of this task (U+V-, W+X-, Y+Z-), but only dunnarts solved the transverse patterning task. Negative patterning requires conditioned responses to 2 stimuli when presented separately but not together (A+, B+, AB-). Both species formed a selective conditioned response to A+ and B+ stimuli and inhibited responding to a simple nonreinforced stimulus (C-), but only dunnarts successfully inhibited responding to the AB- compound to solve the negative patterning task. These experiments are the first to demonstrate configural learning in a marsupial. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in spatial ability and activity in two vole species (Microtus ochrogaster and M. pennsylvanicus).

The hypothesis that sex differences in maze learning result from sex differences in activity was tested with wild-caught prairie (Microtus ochrogaster) and meadow (M. pennsylvanicus) voles. For 38 voles error production and activity were simultaneously measured in a series of 7 symmetrical mazes. Repeated-measures analyses of variance (ANOVAs) examined species, sex, maze, and interaction effects for 3 dependent variables: errors, activity, and errors/activity. The pattern of significant effects was very different for the errors and activity ANOVAs, which suggests that differential activity cannot explain differential error rates. In contrast, the pattern of effects was very similar for errors and errors/activity ANOVAs, which suggests that controls for activity do not remove differences in error production. These results fail to support the activity hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of the physical characteristics of grooming in two species of macaques (Macaca nemestrina and M. radiata).

Examined social grooming in groups of bonnet and pigtail macaques to test the hypothesis that the physical aspects of grooming (body sites, postures, methods) evolved in more aggressive species of primates to serve social functions (proximity maintenance and tension reduction). Both species used social presents to direct grooming to particular sites, and used grooming to other sites to terminate interactions, thus regulating proximity with grooming to certain body sites. The 2 species differed in method of grooming: Pigtails primarily stroked (method used for tension reduction); bonnets picked or pick-stroked (method used for hygiene). Pigtail but not bonnet grooming method regulates tension reduction. Pigtails groomed in a social context, whereas bonnets groomed in solitary context. The pigtail results are similar to those found with rhesus monkeys. Different aspects of grooming serve different functions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of maternal proximity on behavioral and physiological responses to separation in infant rhesus monkeys (Macaca mulatta).

The effects of maternal proximity on the behavioral and physiological responses of infant rhesus macaques during 4 days of total or adjacent separations from the mother were studied. The 6 infants tested showed behavioral responses that differentiated the two separation conditions. Major differences were found in the quantity and quality of vocalizations, the occurrence of cage-biting and cage-shaking behavior, object exploration, and hunched and freezing postures. In particular, the structure of coo vocalizations clearly discriminated between the presence or the absence of the mother during separation. Cerebrospinal fluid (CSF) concentrations of dopamine and serotonin metabolites did not discriminate between the two separation conditions but showed a transient elevation at 24 hr after separation and were not different from baseline by 96 hr after separation. In contrast, both the plasma cortisol and the CSF norepinephrine metabolite responses tended to be greater and to persist for a longer period of time when infants were totally isolated. The results are discussed within the context of attachment and coping theories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Male preferences for unmated versus mated females in two species of voles (Micotus ochrogaster and M. montanus).

Examined male preference for unmated vs mated females in 2 species of voles, using 73 prairie voles and 78 montane voles in 2 testing situations each. In Exp I, conducted in a tether test situation, prairie voles spent significantly more time and copulated more with unmated than with mated females. In Exp II, male prairie voles spent significantly more time visiting and investigating anesthetized unmated females than anesthetized mated females. In Exp III, male montane voles showed no significant visitation or copulatory preference for unmated vs mated females in the tether situation. In Exp IV, male montane voles spent more time with unmated, anesthetized females than mated females but displayed no other significant differences. In general, male prairie voles appeared more discriminating in their mate choice than male montane voles. These differences are consistent with differences in male parental effort in the field. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determinants of mating success in the golden hamster (Mesocricetus auratus): III. Female acceptance of multiple mating partners.

Four studies with golden hamsters investigated females' acceptance of multiple mating partners. Findings show that females that mated only with a single, recently mated male ran a high risk of pseudopregnancy or reduced litter size. Females paired with males that had mated to satiety 30 min, 8 hrs, or 24 hrs earlier showed a reduced willingness to engage in lordosis than did females paired with a sexually rested (2 wks) male. Females paired with recently mated males were also more likely to mate with additional (fresh) males than were females exposed to rested males. Females presented with 2 anesthetized stimulus males readily discriminated between sexually rested and recently mated individuals. Neither prior sexual experience nor recent copulatory activity was required for this discrimination. It is suggested that multiple-male mating (promiscuity) in female hamsters may be an adaptation against an infertile mating as a consequence of mating with a single, recently mated, sperm-depleted male. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Organization of mating behavior in male hamsters (Mesocricetus auratus).

Factor analysis was applied to standard measures of sexual behavior in 73 male hamsters (Mesocricetus auratus) as they interacted with hormone-primed females. The results suggest that 5 factors, or conceptual mechanisms, function in the organization of the behaviors observed in the first 2 copulatory series. Of these, the 3 that relate to the behaviors in the first copulatory series were compared to those emerging from prior analyses of other rodents. These comparisons revealed similarities and differences in factor structure across species. Whereas all of these analyses identify factors related to the initiation and efficiency of copulatory behavior, hamsters seem to differ from other species in the measures that best define these factors. In addition, the copulatory rate factor that has been prominent in previous analyses of rats seems to be absent in hamsters. These results suggest that male sexual behavior in hamsters is organized differently from that in other rodents. In more general terms, they suggest that even species with generally similar copulatory patterns can show significant differences in behavioral organization, in turn suggesting the need for additional factor analytic studies to better establish the extent of these species differences. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Directional responses to sounds in young gerbils (Meriones unguiculatus).

Conducted 3 experiments to determine the ability of infant gerbils to approach an auditory stimulus. In Exp I, 48 16–23 day old Ss were tested in a circular apparatus with a central start area and a movable sound source located at 1 of 8 positions around the perimeter. Stimuli included high- and low-intensity presentations of a tape-recorded gerbil social call, a broad-band white noise stimulus, and a no-stimulus control condition. Ss showed a strong tendency to approach the low-intensity social call and a less pronounced tendency to approach the white noise. In Exp II, 24 16–23 day old Ss were tested in the same apparatus with or without ear blocks to determine the role of binaural cues in directional approach responding. The tendency to approach a low-intensity vocalization was disrupted by obstruction of one ear but not by blocking both ears. Thus, binaural balance was shown to be important for early sound localization. In Exp III, using 6 12–27 day old Ss, the tendency to approach a social call was compared at 12–25, 16–29, 20–23, and 24–27 days after birth. Approach responses were first seen at 16–29 days of age. The responses continued at 20–23 days of age but began to wane at 24–27 days of age. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Observational learning of a left-right behavioral asymmetry in mice (Mus musculus).

B6D2F? hybrid mice that were allowed to observe a trained female mouse open a pendulum door to the right (or to the left) to enter a food compartment later solved this problem faster than pupils that had been placed behind a visual barrier. Male pupils that had observed a "left-handed" teacher performed sinistrally; males that had observed a "right-handed" model performed dextrally. Female pupils did not exhibit their demonstrator's laterality. Observational learning may provide a means to maintain certain lateralized behaviors. Such social learning may lead to the emergence of local traditions and to the cultural diffusion of behavioral asymmetries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning to learn during visual discrimination in group housed dwarf goats (Capra hircus).

Using an automated learning device, we investigated "learning to learn" by dwarf goats (Capra hircus) in what was for them a familiar environment and normal social settings. Nine problems, each consisting of four discriminable black symbols, each with one S+ and three different S-, were presented on a computer screen. Mean daily learning success improved over the course of the first four problems, and the improvement was maintained throughout the remaining five problems. The number of trials to reach the learning criterion decreased significantly beginning with problem four. Such results may be interpreted as evidence that the goats were developing a learning set. In the present case, the learning set appeared to have two components. One involved gaining familiarity and apparent understanding of the learning device and the basic requirements of the discrimination task. The second component involved learning potential error factors to be ignored, as well as learning commonalities that carried over from one problem to the next. Among the error factors, evidence of apparent preferences for specific symbols was seen, which had a predictable effect on performances. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determinants of mating success in the golden hamster (Mesocricetus auratus): II. Pregnancy initiation.

Investigated the initiation of pregnancy and the physiological significance of long intromissions (10–30 sec of intravaginal thrusting), in 4 experiments with 425 virgin and 808 multiparous female LVG golden hamsters and 102 stud males. Results show that virgin females required significantly less copulatory stimulation to induce pregnancy and maximize litter size. Ss receiving only long intromissions showed a 100% pseudopregnancy rate, suggesting that long intromissions can initiate the neuroendocrine response necessary to maintain pregnancy. When the male delivered only 1 or a few ejaculations, the inclusion of long intromissions significantly increased the percentage of both virgin and multiparous females that became pregnant. Order of ejaculations did not affect the proportion of multiparous females that delivered litters. However, litter size of females receiving the 1st or 5th ejaculation was significantly larger than that of females receiving the 10th or 15th ejaculation. Multiple-male matings did not augment pregnancy rates or litter sizes compared with matings with a single, rested male. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determinants of mating success in the golden hamster (Mesocricetus auratus): I. Male capacity.

Studied the maximum copulatory capacity of 102 male golden hamsters to determine what effect a steady state of copulatory activity would have on the chronic fertility of the male, and to determine the rate of recovery from copulatory recovery. Rested Ss produced a mean of 13 ejaculations and then showed a modified copulatory pattern consisting of long intromissions (10–30 sec of intravaginal thrusting) during which no sperm transfer occurred. When a 2nd (fresh) female was introduced, 58% of the Ss produced at least 1 more ejaculation, and 17% of the Ss produced 1 further ejaculation when placed with a 3rd female. In similar 3-female tests conducted 24 hrs later, all Ss ejaculated (mean 4 ejaculations); this level of ejaculatory output was maintained over a subsequent 10-day period of daily testing. Four ejaculations ensured a nearly 100% pregnancy rate and maximum litter size in the 1st females. Second and 3rd females, however, received fewer ejaculations and subsequently showed reduced fertility. Two or 8 hrs of rest resulted in fewer than 50% of the Ss being capable of 1 further ejaculation. However, most of these single ejaculations were accompanied by long intromissions and resulted in successful pregnancies. Findings show that the male golden hamster has a higher ejaculatory output and more rapid recovery from sexual exhaustion than other small rodents that have been studied. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The alarm call system of two species of black-and-white colobus monkeys (Colobus polykomos and Colobus guereza).

Vervet monkey alarm calling has long been the paradigmatic example of how primates use vocalizations in response to predators. In vervets, there is a close and direct relationship between the production of distinct alarm vocalizations and the presence of distinct predator types. Recent fieldwork has however revealed the use of several additional alarm calling systems in primates. Here, the authors describe playback studies on the alarm call system of two colobine species, the King colobus (Colobus polykomos) of Ta? Forest, Ivory Coast, and the Guereza colobus (C. guereza) of Budongo Forest, Uganda. Both species produce two basic alarm call types, snorts and acoustically variable roaring phrases, when confronted with leopards or crowned eagles. Neither call type is given exclusively to one predator, but the authors found strong regularities in call sequencing. Leopards typically elicited sequences consisting of a snort followed by few phrases, while eagles typically elicited sequences with no snorts and many phrases. The authors discuss how these call sequences have the potential to encode information at different levels, such as predator type, response-urgency, or the caller’s imminent behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)