Susana Sánchez

Mate choice differences according to sex and age

We used 7,415 advertisements published in Spain to analyze traits sought/offered by men and women from different age groups. Findings regarding age, socioeconomic status, and physical attractiveness requirements support evolutionary predictions about mate preferences. However, changes in trait preferences among women under 40 appear to be contingent on Spain’s socioeconomic transformation. Women under 40 seek mainly physical attractiveness in men, whereas those over 40 seek mainly socioeconomic status. The trait most sought by men in all age groups is physical attractiveness. Traits sought and offered by advertisers may be conditioned by the personal situation of the advertiser. Mean age of advertisers (around their forties) and Spain’s social indicators suggest that the majority of advertisers have been unsuccessful in the mating arena at the conventional age.

Both parents respond equally to infant cues in the cooperatively breeding common marmoset, Callithrix jacchus

Although there has been great interest in the evolutionary approach to cooperative breeding species, few studies actually directly compare fathers and mothers on their motivation to parent offspring. We tested the responsiveness of common marmoset mothers and fathers to vocal and olfactory cues from their own and other infants using a two-chamber test apparatus designed to evaluate responses in the absence of competition from other caregivers within the family. We tested parentally experienced mothers and fathers living with young infants and former parents with no current offspring to address the following questions: (1) do mothers and fathers respond equally to sensory cues of infants; (2) do parents discriminate cues of their own offspring when the infants are highly dependent and when the infants are more independent; and (3) are parents responsive to both auditory and olfactory cues? Mothers and fathers reacted similarly in all tests. Parents responded equally to isolation calls from their own and unfamiliar dependent infants and there was minimal response to olfactory cues. Responses to infant vocal cues were significantly stronger when infants were dependent upon direct parental care. There was no difference in response between parents whose infants were no longer dependent and former parents with no current offspring. The results show that both parents are highly responsive to infant vocal cues when their own infants are dependent on parental care, supporting an effect of hormonal priming. However, parents only showed behavioural discrimination between vocalizations from their own and unfamiliar infants when their infants were mostly independent.

Feeding tactics in juvenile rhesus monkeys (Macaca mulatta).

In a group of rhesus monkeys, feeding tactics of juveniles were studied in a competitive situation in which food presentation had been modified, and where food was supplied in a feeding trough six times a day. Juvenile offspring of high‐ranking mothers remained longer in the feeding area gathering food. In contrast, juvenile offspring of low‐ranking mothers went less often to the feeding area, primarily to collect food. Low‐ranking juveniles also gathered the food faster than did dominants and used longer feeding bouts. High‐ranking juveniles interrupted their feeding more spontaneously than did subordinate ones. Low‐ranking juveniles did so more often as a result of avoiding and being startled. Juvenile males entered the feeding area to satisfy their food requirements more often than females, but were also aggressively expelled more than females. No relation was found between age in months of juveniles and any feeding parameters or causes of interruption. Nor were significant differences found between young and old juveniles. Juvenile rhesus appear to use different tactics in accessing food according to their sex and to their mothers’ dominance rank. Am. J. Primatol. 51:147–152, 2000.

Reconciliation in captive cotton-top tamarins (Saguinus oedipus), a cooperative breeding primate.

Reconciliation has been demonstrated in all primate species in which the phenomenon has been studied. However, reconciliation has been studied in only two species of callitrichids, and conclusions remain controversial. The first aim of this study has been to find out whether captive cotton‐top tamarins (Saguinus oedipus) reconcile, since this is the first such study on this species. We examined 227 conflicts in three family groups (N=19). Instances in which individuals remained together in t=0 (29; 12.8%) were not analyzed. The cotton‐top tamarins showed heightened affiliation between opponents in the postconflict periods (PC) compared with matched control (MC) periods (39.88±5.12% and 3.18±1.27%, respectively), with a corrected conciliatory tendency of 37.17±5.37%, and a “time window” that included the first 180 sec of the PC period. Former opponents were the most likely recipient of affiliative behaviors during the PC periods: 39.83±4.26% vs. 11.36±5.33% during MC periods. The proportion of attracted pairs (47.13±6.25%) was significantly higher than those of dispersed pairs for male–male conflicts (3.79±1.79), but not for male–female conflicts (27.31±9.32 and 4.82±2.9, respectively). In cooperative‐breeding species, specific sex‐class dyads might differ in how they resolve conflicts. Am. J. Primatol. 71:895–900, 2009.

Changes in Body Mass of Expectant Male Cotton-Top Tamarins (Saguinus oedipus)

It has been noted that expectant cotton-top tamarin males in captivity experience a body mass increase during the last months of their mates’ pregnancies, and this has been explained as being a male physiological response. We studied the body mass of 4 inexperienced and 4 experienced expectant males, and we expected to observe a larger body mass increase among the experienced ones since they undergo multiple hormonal changes in comparison to inexperienced expectant males. However, while inexperienced expectant males gained body mass during months 4–6 of the pregnancy period by a mean ±SD of 5.4 ± 3.1% (i.e. 29 ± 17 g), the experienced ones did not (mean ± SD of months 4–6, 0.5 ± 1.7%, i.e. 5 ± 12 g). The results suggest that other factors, such as behavioural communication between pairs and feeding and resting behaviour, should be studied in order to clarify the basis of this body mass increase.