The effect of infant vocalization in alloparental responsiveness of common marmosets (Callithrix jacchus).

Among mammals, alloparental care can be influenced by hormones as well as by previous experience and sensory stimuli from the infants, such as sight and sound, smell, and physical contact with the infant. To determine the responsiveness of common marmoset (Callithrix jacchus) nonreproductive females and males with and without previous experience in caretaking to infant sensory cues, we exposed 12 females and 12 males to vocalization recordings for 10 min under two conditions: (1) exposure to adult conspecific vocalization recordings, and (2) exposure to infant vocalization recordings. We recorded the frequency of approach toward the sound source, the time spent near it and locomotion frequency of males and females in the cage under both conditions. Blood samples were collected after each test for cortisol measuring by EIA method. The infant vocalization affects the behavioral and hormonal responses of males and females of common marmosets. The animals approached and spent more time near the sound source and showed an increase in locomotion during infant vocalization exposure compared to the adult vocalization. However, there was no significant difference in the behavioral response of animals when previous experience and the sex were taken into account. In both sexes, cortisol levels were significantly higher following infant vocalization exposure compared to the adult vocalization. These findings suggest that the infant vocalization appears to be an effective cue that facilitates the approach of the caregiver and maintaining their responsiveness and that the cortisol seems to be important for alertness to sensory stimuli, modulating their motivation to interact with the infant.

Do newborn vocalizations affect the behavioral and hormonal responses of nonreproductive male common marmosets (Callithrix jacchus)?

Parental care in mammals is influenced by sensory stimuli from infants, such as sight and sound, and by changes in the hormone levels of caretakers. To determine the responsiveness of common marmoset (Callithrix jacchus) adult males with and without previous experience in caretaking to newborn sensory cues, we exposed twelve males to infant vocalization recordings and assessed their hormonal and behavioral responses. Males were placed in the testing cage for 10 min under two conditions: (a) control condition (exposure to adult conspecific vocalization recordings), and (b) experimental condition (exposure to infant vocalization recordings). We recorded the frequency of approach towards the sound source, the time spent near it and locomotion frequency of males in the cage under both conditions. Blood samples were collected after each test for cortisol, measured by the enzyme immunoassay method. Infant vocalization affects the behavioral and hormonal responses of non-reproductive male common marmosets. All males approached and spent more time near the sound source and showed an increase in locomotion during infant vocalization exposure compared to the control condition. Successive exposure to infant vocalization increased the responsiveness in inexperienced males. Cortisol levels were significantly higher following infant vocalization exposure compared to the control condition. These findings support the assumption that sound stimuli from the newborn are critical in initiating and maintaining caretaker responsiveness and that cortisol seems to be important for alertness to sensory stimuli, modulating their motivation to interact with infants.

Behavioral and hormonal response of common marmosets, Callithrix jacchus, to two environmental conditions.

Captive animals of several species change their behavioral pattern and hormonal profile in response to physical (for example, cage size and temperature) and social (for example, group size and social isolation) modification of their environment. To evaluate the effect of environmental change in captivity, the affiliative (contact/proximity and allogrooming) and individual (approach, leaving, scent mark, locomotion, and autogrooming) behavior of five family groups of common marmosets, Callithrix jacchus, were recorded on weekdays (non-quiet) and at the weekend (quiet) for two months. In addition, fecal samples were collected for four of these groups to measure their cortisol levels under both conditions. The behavioral pattern and hormonal profile of breeding pairs and their offspring were modified by different management routines used in the experimental conditions. We found that the animals spent more time in affiliative interactions at the weekend, whereas on weekdays, they showed more individual behaviors. Moreover, cortisol levels of breeding pairs and their offspring were higher on weekdays, suggesting that common marmosets living in captivity react to environmental modification by changing their behavioral and hormonal pattern.