Jeffrey R. Alberts

The biparental care system of the California mouse, Peromyscus californicus.

Most knowledge of parent-offspring relations in mammals is derived from studies of mother-infant interactions. Male parental care has been less well studied. We explored maternal and paternal behavior of the California mouse, Peromyscus californicus. Six pairs of parents and their young were videotaped continuously for 12 hours/day, on alternate days from Days 1 to 31 postpartum. Males exhibit all parental activities and to the same extent as displayed by mothers, except lactation. Male parental behavior begins on the day of birth. Mothers and fathers spend substantial and equivalent amounts of time in the nest and in physical contact with pups throughout lactation. Males devote more time than females to licking pups, although females engage in more pup anogenital licking. Mothers nurse for at least 4 weeks, and fathers and mothers both build nests and carry young. The biparental care system of Peromyscus californicus affords an opportunity to develop a broader, more complete view of parent-offspring relations.

Ultrasonic vocalizations by rat pups in the cold : an acoustic by-product of laryngeal braking ?

Isolated rat pups respond to cold exposure physiologically by increasing metabolic heat production and behaviorally by emitting ultrasound. The relationship between these 2 responses was investigated by monitoring oxygen consumption, heat production by brown adipose tissue, respiratory rate, and ultrasound production during cold exposure in pups 10-12 days of age. All 3 physiological measures increased contemporaneously with the initiation of ultrasound. Pups also exhibited a respiratory pattern characterized by the prolongation of expiratory duration in relation to inspiratory duration. Ultrasound was often detected during these prolonged expirations, suggesting that pups were using laryngeal braking. Laryngeal braking is thought to enhance oxygen uptake in the lungs. Thus, ultrasound may be an acoustic by-product of a respiratory maneuver that increases oxygen delivery to metabolically active tissues during cold exposure.

Behavioural and endocrine responses of female mice to synthetic analogues of volatile compounds in male urine

Abstract The urine of intact, adult male mice elicits more investigatory sniffing from female mice than does the urine of castrated males. When either of two androgen-dependent urinary compounds, 2- sec -butyl dihydrothiazole or dehydro- exo -brevicomin are added to castrate urine, its relative attractiveness remains the same. When both compounds are added to castrate urine, however, its activity is enhanced and the castrate urine becomes as attractive to females as whole, intact male urine. Females exposed to the reconstituted ‘normal’ urine for 3 min per day, displayed more frequent oestrus cycles. The two synthetic compounds are synergistic in the context of castrate urine, producing an olfactory message that behaviourally and physiologically mimics the activity of the normal biological signal.

Postpartum maintenance of paternal behaviour in the biparental California mouse, Peromyscus californicus..

Abstract Most knowledge of the mechanisms underlying parental behaviour in mammals is derived from studies of maternal behaviour. Male parental care and its proximate causation has been less well studied. The maintenance of paternal and maternal behaviour in the biparental California mouse was investigated by removing the pups and/or mate on the day of birth and testing parents individually on day 3 or day 5 postpartum for 10 min with a 1- to 3-day-old alien pup. Pup presence maintained maternal responsiveness but was not essential for continuation of paternal care. Presence of the father had no effect on maternal care. In contrast, presence of the mother maintained paternal responsiveness. Direct physical contact between mother and father was not necessary for maintenance of paternal behaviour. Maternal excreta were sufficient to keep fathers parental.

On the significance of similarities between ultrasonic vocalizations of infant and adult rats.

The communicatory significance of the 40 kHz vocalization of rat pups and the 22 kHz vocalization of adult rats have been topics of research for over three decades. The 40 kHz vocalization is emitted by pups during cold exposure, whereas the 22 kHz vocalization is emitted by adults following ejaculation, following defeat in aggressive encounters, as well as in other contexts. Recent research suggests that the 40 kHz vocalization is the acoustic by-product of a respiratory mechanism that enhances gas-exchange in the lungs during times of increased oxygen consumption. Furthermore, a reevaluation of research into the physiological basis of the 22 kHz vocalization suggests a similar conclusion. In the present paper, we discuss mechanistic and contextual aspects of ultrasound production. We conclude that these two vocalizations, produced by identical mechanisms and reflecting identical physiological states, are actually the same vocalization, albeit at different frequencies. This alternative view of ultrasound production has implications for our interpretation of the communicatory significance of these vocalizations.

Ontogeny of olfaction: Development of the rats' sensitivity to urine and amyl acetate

Abstract Rat pups, 1 to 17 days of age, were tested for sensitivity to two olfactants, amyl acetate and adult rat urine. Biological and non-biological olfactory stimuli were generated by sparging and delivered to subjects via a dilution olfactometer. Unconditioned respiratory responses, odor-induced polypnea and sniffing, were used to measure detection of an odorant injected into a background stream of filtered air. Amyl acetate was presented in an ascending series of concentrations. Pups of all ages detected amyl acetate; chemosensitivity increased with age to all 3 concentrations of this nonbiological stimulus. Two concentrations of adult rat urine odor were equated to the strength of amyl acetate for 9-day-olds. Each normalized urine stimulus was then tested across the full range of age groups. Again, there was a dramatic age-related increase in chemosensitivity. Moreover, there was no indication of differential sensitivity to these biological and non-biological olfactants. These data were discussed within methodological and conceptual frameworks related to analyses of early olfactory and behavioral ontogenesis.

Stimulus control of maternal responsiveness to Norway rat (Rattus norvegicus) pup ultrasonic vocalizations.

Mother rats (Rattus norvegicus; 6 to 8 days postpartum) approach and maintain proximal orientation to a pup that is emitting ultrasonic vocalizations (USVs) far more than do virgin females (W. J. Farrell & J. R. Alberts, 2002). We used a playback regimen to examine the roles of acoustic and nonacoustic cues in regulating maternal proximal orientation toward vocalizing pups. When presented with recorded USVs, mothers of 6- to 8-day-old pups and nulliparous virgin females exhibited equivalent levels of proximal orientation toward the playback speaker. Mothers did show enhanced proximal orientation toward recorded USVs, however, if a silent pup was positioned below the speaker. Pup odors appear to be crucial for the maternal response to vocalizing pups, as peripherally induced anosmia attenuated maternal proximal orientation toward a vocalizing pup. Furthermore, spatial contiguity between olfactory and auditory stimuli was required for a maximal maternal response.

Ontogeny of long-term memory for learned taste aversions.

Eighteen-day-old and adult rats were trained on a learned taste-aversion (illness reinforced) or a lick-suppression (shock reinforced) task and tested for retention after either 1, 28, or 56 days. Young rats showed a retention deficit relative to adults in the lick-suppression task but not for taste-aversion learning. Young rats did, however, show relatively less suppression to the saline solution than adult, but a follow-up experiment showed that changing the poisoned solution to a more-distinctive flavor produced high levels of suppression and no retention deficit in 18-day-old rats. In the final experiment a technique was developed for studying retention of taste aversion in suckling rats. Retention of taste aversion was studied in 10-, 12-, 15-, and 20-day-old rats at retention intervals ranging from 1 to 10 days. Using this procedure the younger (10- and 12-day-old) rats showed more rapid forgetting than 15- or 20-day-olds. These findings were interpreted as (I) evidence for a dissociation of memory for learned taste aversions from other kinds of learning and (2) further support for the general proposition of improved long-term memory during early ontogenesis.

Learning as adaptation of the infant

The present report advocates an adaptive, ecological approach to the study of learning in infants. Concepts of developmental niche and ontogenetic adaptation are applied to early mammalian development. Within this conceptual framework, it is asserted that learning cannot be fully understood separately from a behaving body; that learning is a dimension of behavior and physiology. The role of learning in the development of ingestive behavior, especially suckling and the transition to solid food, is used to illustrate the potential of studying learning in development. These considerations are offered as examples of an alternative approach to the empirical study of learning by infants. The approach advocated herein can be applied to clinical issues: developmental adaptations evolved in contexts that differ from our modern environments. Exposure to contexts or contingencies that are evolutionarily unexpected may inadvertently create pathology.

Maternal contributions to sensory experience in the fetal and newborn rat (Rattus norvegicus).

Using videographic analyses, we identified and quantified maternal contributions to the sensory environment of the perinatal rat (Rattus norvegicus) by analyzing, from the offsprings perspective, the dams activities during gestation, labor, and delivery. Our observations indicate that pregnant females remain highly active during the final week of gestation, as compared with nonpregnant control animals. Exploratory movements, feeding, drinking, self-grooming, and other activities of the rat dam pitch, turn, accelerate, and expose fetuses to mechanical pressures. During parturition uterine contractions and maternal licking and handling provide vigorous tactile and vestibular stimuli to pups. Newly born pups are exposed to intense thermal stimulation, cooling rapidly to the temperature of the postnatal environment. Our results suggest that fetal and newborn rats are exposed during development to a broad range of maternally produced stimuli.