Ultrasonic vocalizations or calls produced by young rodents have been associated with aspects of maternal behavior, in particular retrieving. We reviewed the methods of study used by investigators on each topic, focusing on intrinsic or subject variables and extrinsic or experimental variables. Intrinsic variables included the species studied, genotypes employed, number and sex composition of the litters, and the ages of mothers and pups. Extrinsic variables for studies on ultrasonic calling included: eliciting stimuli, test surroundings, and the length of observation. Extrinsic variables in studies of maternal retrieval included the testing procedure and the length of observation. The methods used in studies within each topic vary greatly. In an effort to facilitate progress in the areas, especially with respect to isolating individual genes with a contribution to ultrasonic call production or studying the effects of pharmaceutical agents on either behavior, we propose some standardization of nomenclature and/or procedure in four areas: (1) the stimuli or situations used to elicit ultrasonic calls, (2) the length of observation in ultrasonic call studies, (3) the number of pups per litter and the sex composition of litters in both ultrasonic call and maternal retrieval studies and finally, (4) the apparatus or testing situation used in studies of pup retrieval.

Ethanol (ETOH)-induced locomotor activation and depression were studied in 23 genotypes of mice. This included a diallel cross of four inbred strains tested with a range of ETOH doses from 0 to 2.75 g/kg. The diversity in shapes of the biphasic ETOH dose-response curves was both qualitative and quantitative, and additive gene action characterized the genetic control of the dose-response curve. Small dominance effects were typically directional in the direction of more activation, or resistance to sedation. No evidence was found for maternal effects, sex linkage, or epistasis. Sex differences were seen in the increased susceptibility of male mice to locomotor sedation at higher ETOH doses. In the diallel cross, there was no correlation between the degree of activation produced by low ETOH doses and sedation produced by higher doses. This indicates that while considerable genetic influences exist for both activational and sedative domains of ETOH effects, these genetic influences are relatively independent.

Infant mice produce ultrasonic calls that may elicit retrieval by adult mice. Age-related differences and genetic effects, such as additivity and directional dominance, have been found for most call characteristics at 3 days of age. Significant maternal effects have been reported for calling rate. However, little is known about how the influence of these genetic effects changes with age. This study explored developmental-genetic patterns of inheritance of seven ultrasonic call characteristics at ages 3-9 days, from groups of mice derived from a complete 4 x 4 diallel cross. The results indicate that additive variance contributes significantly to all characteristics for all ages. Maternal effects have a small effect on call characteristics. Dominance effects decrease with age for rate, range, and length of calls, suggesting less selective pressure toward higher rates, greater range, and longer calls as pups become more competent thermoregulators.

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The genetics of social behavior presents special difficulties because the phenotype is the product of an interaction between two or more individuals. Social interactions are of two kinds: (1) cooperative, in which the probabilities of transmission of the genes of all participants are similarly affected by the outcome, and (2) agonistic, in which the probabilities for the participants are affected in opposite directions. The latter are of particular interest for evolutionary theory. Three major types of designs for measuring social behavior in genetic experiments are available: (1) homogeneous sets, (2) standard tester, and (3) tester panel representing a reference population. The advantages and limitations of each method are discussed. Important areas for future development include the relationship of genetic and experiential factors in early life to social status as an adult and the extension of the genetic analysis of social behavior to natural populations.