Development and expression of autogrooming in the Mongolian gerbil, Meriones unguiculatus

Adult gerbils, Meriones unguiculatus, autogroom their body parts in the order: mouth--nose, face, ears, flank, ventrum, and tail. This is the identical order in which the autogroom matures during the first 33 days of life. The parallel sequencing increases our understanding of neurophysiological processes underlying movement patterns and also indicates how movement patterns evolve.     

Mate recognition by urine odors in the Mongolian gerbil (Meriones unguiculatus)

We examined the responses of male and female gerbils housed in opposite- or same-sex pairs to the urine odors from their cage-mate and those of an unfamiliar gerbil of the same sex. Gerbils housed in mated pairs spent more time investigating the odor of their partner. They also emitted more modulated ultrasonic vocalizations in the presence of their partner's odor than in the presence of the unfamiliar odor. Gerbils housed in same-sex pairs did not respond differentially to the odor of their cage-mate. There were sex differences in the frequency of ventral scent-marking and modulated vocalizations, with males showing more of these behaviors than females. The urine odor of the gerbil's mate can thus be discriminated from those of other gerbils. Recognition of individual odors may promote affiliative behavior and reduce aggression, thus playing an important role in pair maintenance in gerbils.     

Harderian gland exudates in the male Meriones unguiculatus regulate female proceptive behavior, aggression, and investigation

Harderian gland secretions exit from the nose of Meriones unguiculatus during an autogroom (Thiessen, 1977). The exudates act as an attractant pheromone and as a thermoregulatory barrier when spread throughout the pelage. A recent study demonstrated that Harderian exudates in the male guide proceptive behavior in the female (Harriman & Thiessen, 1985). The present study replicated this finding by showing that estrous females direct fewer proceptive acts toward males lacking Harderian glands. In addition, it was found that females are more defensively aggressive toward Harderianectomized males and prefer to spend more time in the vicinity of intact males. It is speculated that Harderian spread allows the female to assess the reproductive competence of the male.     

Effects of olfactory bulb ablation and androgen on marking and agonistic behavior in male Mongolian gerbils (Meriones unguiculatus).

Male Mongolian gerbils, selected for high marking frequency, were paired with male opponents, and marking and fighting behavior were recorded. Animals then underwent castration, bilateral bulbectomy, unilateral bulbectomy, the combined operations, or a sham operation; and their behavior was again observed. All operated animals showed drastic reduction in both marking and aggressive encounters. Injections of testosterone propionate (TP) produced complete restoration of marking in castrates, but not in bilaterally or unilaterally bulbectomized animals or combined operates. The exhibition of aggression after injections of TP, however, was enhanced to supernormal levels in bulbectomized or bulbectomized-castrated animals. The results suggest the following: that removal of the olfactory bulbs may eliminate a critical neural input necessary for the normal expression of marking and agonistic; that although marking and fighting are influences by olfactory input and gonadal steroids, their regulatory mechanisms may not be identical; and that removal of the bulbs may sensitize a neural mechanism controlling aggression, thus potentiating its elicitation following administration of exogenous androgen.     

Depth perception in Mongolian gerbils (Meriones unguiculatus) and spiny mice (Acomys russatus and A. cahirinus)

Depth perception in gerbils and spiny mice was studied with a modified visual cliff which varied the height of a platform from 5.08 cm to 25.4 cm and presented animals with an apparent drop-off to a patterned or a white field. Time to descend from the platform and orienting response frequency were recorded. For gerbils neither measure varied significantly between the platforms. Both Acomys species increased descent time and orienting response frequency as platform height increased. The results suggest that both gerbils and spiny mice can perceive depth, though there appears to be a difference between the species' use of sensory cues in descending from a visual cliff. The spiny mice appear to rely more on visual cues than do the gerbils. The data also reveal subtle behavioral differences between the Acomys species that may relate to their successful sympatry. The results are discussed by alluding to ecological differences between these species in their natural habitats.     

The effects of food deprivation,aggression, and isolation on infanticide in the male Mongolian gerbil

Male Mongolian gerbils show an increase in infanticide and pup-cannibalism after 24-hr food deprivation, suggesting that food acquisition is a function of this activity. Dominant animals show high levels of infanticide, but subordinate animals are inhibited from this activity. An increase in infanticide is seen when males from a single sex group are isolated; this increase resembles that observed when a male is separated from his pregnant mate [Elwood, 1980]. These results suggest a mechanism whereby males are normally brought into a noninfanticidal state during cohabitation with their pregnant mates owing to subordination by the latter. In this manner males are able to utilize strange pups as food but avoid harming their own offspring.     

The effect of environment on visual cliff performance in the Mongolian gerbil

Depth perception in the Mongolian gerbil was investigated as a function of age and environment. Thirty-two gerbils were raised in either a cliff or flat environment, and half the gerbils in each condition were tested on the visual cliff from 21 to 57 days of age. All gerbils were tested at 60–61 days on a standard visual cliff, a barrier cliff which prevented movement along the centerboard, and a jumping platform. While the gerbils did not display a preference for the shallow side when tested at 21 days, those living in a cliff environment showed rapid acquisition of such a preference, whereas those living in a flat environment did not. By 60–61 days, however, all gerbils demonstrated a strong preference for the shallow side on both versions of the visual cliff, regardless of environment or pretesting experience.     

The roots of territorial marking in the Mongolian gerbil: A problem of species-common topography

The Mongolian gerbil (Meriones unguiculatus) has recently been introduced into behavioral research. Many features make it an ideal laboratory animal. It is docile, highly exploratory, a good learner, virtually odorless and can be maintained without water; other than that it metabolizes from its food. General characteristics of the gerbil are described, and a brief review of behavioral research is given. The gerbil also possesses unique attributes that can only be studied by matching experimental methodology with species-common responses. Territorial marking is used as example. The gerbil regularly marks objects in an open field by skimming the object with a midventral sebaceous scent gland. The marking and gland are dimorphic, with the male marking about twice as frequently as the female and possessing a gland roughly twice the size. The configuration of the field (object quality) modifies the frequency of the response, as does the time of day the animals are exposed to the field. Androgen levels control the level of marking in the male and female, and the correlations between testis weight, size of the sebaceous gland, secretory output and marking frequency are significant. When a gerbil is introduced into an open field recently contaminated by another gerbil, or when objects are smeared with sebum and placed in the field, the male tends to be more hesitant in several types of behavior. The laboratory measures are internally consistent and congruous with the notion that natural selection has acted to reinforce a hormone-behavior relation of social significance to the gerbil.