Mother-Young Feeding Synchrony and Early Food Selection Differences in Eulemur fulvus

I tested the hypothesis that mother-young cofeeding correlates with a systematic similar food selection in wild Mayotte brown lemurs (Eulemur fulvus). I simultaneously recorded the feeding behavior of 4 maternal dyad members, from infant birth to weaning, and 10–12 mo of juvenile age, during 10-min focal periods, each separated by 5-min intervals over 10 mo. I recorded the solid food items selected for each feeding behavior at the level of specific plant part, along with the distance between the 2 individuals. I considered feeding behaviors simultaneous (between the young lemurs and their mothers) when the young began to eat a food item while the mother was already eating, regardless of the separation distance. During their first year, most of the feeding events of the young brown lemurs were initiated by their mothers. However, infants also selected different food items from those chosen by their mothers in almost one-third of cases, and the food selection dissimilarity was not attributable to an increase in the distance of separation. For juveniles, dissimilar food selection was significantly lower and linked to an increase in mother-juvenile separation distance. Thus, the substantial proportion of dissimilarity in solid foods selected by the infant during the synchronized feeding behaviors strongly suggests that social influences were not food-specific and might instead drive the acquisition of group feeding activity rhythm rather than food selection habits.     

Observations on the ontogeny of feeding behavior in mountain gorillas (Gorilla gorilla beringei)

This report describes observations on the ontogeny of food choice in mountain gorillas (Gorilla gorilla beringei), made during a 17-month field study of mountain gorilla feeding ecology in the Parc National des Volcans, Rwanda. Data are presented on the feeding behavior of two infants observed from birth to the age of 8 months and on older infants and juveniles. This information is compared with data on the composition and diversity of the diets of young adults and adults in the same social group. Initial feeding by infants is usually synchronized with the mother's behavior: infants ingest the same food, or a different part of the same plant species, currently being eaten by the mother or just eaten by her. This suggests that observational learning is largely responsible for the transmission of food preferences. Most feeding by young infants, whether or not synchronized with the mother's, is on those foods eaten most frequently by adults. Infants also independently sample potential foods, some of which are apparently not consumed by adults. The frequency of sampling declines with age, although even adults occasionally ingest foods not observed to be eaten by other adults. By the age of 3 years, young mountain gorillas have developed the basic dietary patterns of adults, in terms of the number of foods eaten, the proportions in which specific foods are consumed, and diet diversity and equitability. There is a strong possibility that chemical cues influence food choice, but their role remains unclear.     

Female-infant interactions among free-ranging stumptail macaques (Macaca arctoides)

The friendly and aggressive behaviors directed by females other than the mother to the troop's infants were recorded during a six-month long study of stumptail macaques living on an island. A great deal of friendly contacts were directed by the females toward the troop's infants. Juvenile females interacted with infants mainly through social play while adult females directed passive contacts (e.g., touch-hand) to them. While the adult females displayed more care contacts toward male infants the juvenile females preferred the female infants. The social position of the infant's mother in the troop and the attention it received from the males regulated the caring behavior an infant received from the females.     

Sensorimotor cognition in young feral orangutans (Pongo pygmaeus)

The goal of this study was to describe object manipulation in wild orangutan infants and juveniles. Object manipulation is an important subsistence activity that also reflects cognitive functioning. Orangutans were studied in the field, at the Tanjung Puting Reserve, Kalimantan Tengah, Indonesia. Fourteen orangutans, grouped by age (infants 2.5 to 4.6 years; juveniles 5 to 8.5 years), were observed over a total of 555 hr and for an average of three full dawn-to-dusk “follows” each. Young orangutan’s manipulations were categorized along a hierarchy of complexity. The least complex manipulations were single sensorimotor actions such as grasping, mouthing, and waving. The most complex manipulations were combinations and coordinations of actions, such as experimentation with objects, tool use, and planning. Manipulative behavior occurred mainly when foraging, i.e. when obtaining and processing food items. Interestingly, complex behavior occurred most often when locomoting. The most complex object manipulations, however, occurred rarely. Infants and juveniles exhibited equivalent levels of complexity. Several aspects of this study point to the importance of social assistance provided by competent mothers for the development of young orangutans’ ability to locomote and to locate, obtain, and process food items. This study also highlights the cognitive abilities of young wild orangutans regarding tool use.     

Social Dependence of Infant Slow Lorises to Learn Diet

Nocturnal lorises and pottos (Lorisinae) are among the least gregarious of primates. Mothers start to leave their infants alone during the night as early as the day of birth. However, captive studies also indicate that weaning young lorisines closely follow their mothers nearly all the time and obtain their first solid food via scrounging. Accordingly, it has been suggested that young lorisines depend on their mothers to obtain dietary information and to achieve dietary independence by watching their mothers feeding or interacting directly with their mothers over food. We tested for a social dependence on dietary learning by infants in a social network of wild slow lorises (Nycticebus coucang). The social network included one male infant, his mother, and two subadult females. The infant only took to mouth food items that were also part of the females' diet and showed concordance in the frequency of use of food patches with the females. These results contradict dietary learning by trial and error. They indicate that dietary learning by infants depends on information obtained from older conspecifics. However, the infant was never involved in direct interactions with conspecifics over food and fed mostly alone. He was not within a distance where he could see the females feeding more often than expected from the configuration and utilization of home ranges. The infant never looked at conspecifics feeding in his vicinity, which suggests that visual observation or direct interaction over food may not be the mechanisms by which information about food resources is passed from older individuals to young, but that other ways of obtaining such information are used.     

Begging for information: mother-offspring food sharing among wild Bornean orangutans

Transfer of solid food from mothers or other adults to dependent offspring is commonly observed in various primate species and both nutritional and informational benefits have been proposed to explain the function of such food sharing. Predictions from these hypotheses are tested using observational data on wild orangutans (Pongo pygmaeus wurmbii) at Tuanan, Central Borneo, Indonesia. In 1,145 hr of focal observation and 458 recorded food interactions between four pairs of females with offspring it was found that virtually all transfers were initiated by the offspring and that younger infants solicited food more often and did so for a greater variety of items than older offspring. All offspring primarily solicited food that was difficult to process, i.e., inaccessible to them. Furthermore, the amount of food solicitation was negatively correlated with ecological competence. Hence food sharing seemed to be related to an offspring's skill level, as suggested by the informational hypothesis. In contrast, offspring did not solicit high-quality items more than low-quality items and food sharing did not peak around the age of weaning, as predicted by the nutritional hypothesis. Mothers were usually passively tolerant, allowing offspring to take food but hardly ever provisioned. Parent-offspring conflict concerning food sharing was only observed well after weaning. Thus, by taking food directly from the mother, young orangutans were able to obtain information about the affordances and nutritional value of food items that were otherwise out of their reach and could familiarize themselves with the mother's diet. In species such as orangutans or other apes, characterized by a broad diet that requires extractive foraging, informational food transfer may be vital for an immature to acquire complex feeding skills and adult diet.     

Vigilance during play in squirrel monkeys

Play by young squirrel monkeys (Saimiri boliviensis) may put them and other troop members at risk for predation because youngsters are noisy, separated from adults, and not vigilant when at play. In a study using separated groups of adults and 1-year-old juveniles caged outdoors, we found that adult female squirrel monkeys become more vigilant during periods of spontaneous play among juveniles. This behavioral response could be obtained with auditory cues (play vocalizations) alone. Five times as much vigilance activity was directed toward an area from which threat or disturbance was likely to come as was directed toward the juveniles themselves. These results suggest both an adaptive, compensatory increase in adult vigilance during play and a function for play vocalizations. Additional functions for play vocalizations remain to be investigated.     

Ontogeny of Feeding Behavior of Eulemur fulvus in the Dry Forest of Mayotte

Captive data show that juvenile mammals usually reproduce the diet of the adult. However, it is not known whether, in natural environments, the process of feeding maturation varies according to available foods and to adult choices. I examined the feeding ontogeny of Mayotte brown lemurs (Eulemur fulvus), a presumed introduced species, from birth to 12 mo old in the southern dry forest of Mayotte. The study focused on activities and diets of 4 mothers and their juveniles from 2 groups in 1999 and 2000. In 2001, we also observed 2 other dyads from each group for 2 mo (March/April). I assessed plant phenology in each group's home range. There are 4 phases of feeding ontogeny: (1) the 3 mo following birth are characterized by lactation, early bouts of exploration, and consumption; (2) the next 2 mo are characterized by feeding and social weaning; (3) during the sixth and seventh mo, the daily feeding activity rhythms of the mother and her juvenile are synchronized and diets largely overlap; (4) at 10–12 mo of age, the feeding juvenile is closer to other group members than to its mother. During their first year of life, especially before being weaned, juveniles eat several food items that are not ingested by their mothers. It appeared that the progressive overlap in dietary items and feeding synchrony between mother and juvenile depends on several types of leaming. There is a correlation between the availability of particular food resources with high nutritional quality and timing of reproduction and infant maturation.     

Social learning and mother's behavior in manipulative tasks in infant marmosets

High levels of social tolerance are considered to promote social learning, as they allow direct observation of a manipulating conspecific and facilitate scrounging. Owing to tolerance toward infants, infancy is thought to be especially suited for learning socially transmitted behaviors. Despite this, few studies have investigated social learning of infants, particularly in manipulative tasks where observation might be most helpful. Here, we investigated (1) the influence of social learning on task acquisition in infant marmosets, and (2) whether the mother augments her behavior in a way that may enhance social learning by her infants. We tested infant and juvenile marmosets in four different complex foraging‐related tasks, featuring large living insects (two tasks) or artificially embedded prey (two tasks). Each individual observed the mother solving two of the tasks and served as a control in the other two tasks. Observers manipulated more and succeeded sooner than control animals, suggesting that observing the mother promoted learning either directly or by decreasing neophobia. Moreover, the data suggest that learning in 11–15 week‐old infants might be promoted actively by the mother. She solved the tasks, consumed less food, and consumed it later than when foraging with older offspring or alone. Furthermore, the results indicate the possible importance of the third and fourth month of infancy as the crucial ontogenetic period for social learning in marmosets, corroborating recent observations of free‐living common marmosets. Am. J. Primatol. 71:503–509, 2009. © 2009 Wiley‐Liss, Inc.     

Influence of some interactions between fledglings and adults on the food choice in young canaries (Serinus canarius)

The influence of interactions between young canaries (Serinus canarius) and adults on the onset latency of detection, picking up, husking, and eating of seeds was studied in 90 juveniles canaries, aged 28 days, and fed no seeds after their first flight from the nest. The following factors were studied: the ability to cat with the adults, the observation of adult feeding behavior, and the attraction that the adults exert on the young, in 6 experimental treatments, allowing for the isolation or combination of the above factors. The conclusion was made that an attraction for the adults is expressed as a preferential orientation toward them. This attraction accelerates the detection, husking and eating of seeds by the young. Social facilitation and local enhancement resulting from the juvenile observation of adult eating preferences accelerate their picking up and husking seed. Social facilitation is evident only if the attraction toward the adults is not precluded. Social transmission of food preferences which favors the autonomy and emancipation of the young appears to exist in this bird. U.M.R. au C.N.R.S. n°5550     

Aunts and Mothers: Adaptive Implications of Allomaternal Behavior of Nonhuman Primates

Explanations of the function of behavior directed toward young primates by conspecifc females other than the mother have emphasized variow outcomes beneficial to "aunts, I' mothers, infants, or some combination thereof. There is little evidence, however, that allomothering benefits mothers or infants to any signifcant degree; allomothering is selfish behavior with highly variable consequences roughly predzctable on the basis of genealogical ties between participants. Selective consequences of infant kidnapping and aunting-to-death are examined, and a hypothesis is suggested concerning the adaptive significance for mothering of allomothering. [adoption, infant-stealing, behavioral selection]     

Intended Receivers and Functional Significance of Grunt and Girney Vocalizations in Free-Ranging Female Rhesus Macaques

We investigated the intended receivers and contexts of occurrence of grunt and girney vocalizations in rhesus macaques (Macaca mulatta) to assess whether these calls are best interpreted as signals of benign intent or as calls that may function to attract the attention of other individuals or induce arousal. We focally observed 19 free‐ranging adult female rhesus macaques. Female calls increased dramatically after infants were born, and most were directed toward mother–infant dyads. When infants were physically separated from their mothers, callers visually oriented toward infants in over 90% of the cases, suggesting that infants were the intended receivers of grunts and girneys. Approaches followed by vocalizations were more likely to lead to the caller grooming the mother, less likely to elicit a submissive response, and more likely to result in infant handling than approaches without calls. Infant handling, however, was not necessarily benign. Vocalizations were often emitted from a distance >1 m and were rarely followed by approaches or social interactions. Our results suggest that grunts and girneys are unlikely to have evolved as signals that encode information about the caller's intention or subsequent behavior. Whereas girneys may be acoustically designed to attract infants’ attention and elicit arousal, grunts may have no adaptive communicative function. Mothers, however, may have learned that other females’ grunts and girneys are unlikely to be associated with significant risk and, therefore, are generally tolerant of the caller's proximity and behavior.     

Tutoring in Wild Golden Lion Tamarins

Among most nonhuman primates, juveniles must acquire most of their solid food independently. Information gleaned from adults results from efforts initiated by the juveniles. Donation of food or foraging information by adults to immatures is rare among apes and virtually unknown among monkeys. We report 3 observations in which wild adult golden lion tamarins appear to have directed their immature offspring to a location where a hidden prey item was located. According to the definition of Caro and Hauser (1992), the tamarins were tutoring their young.     

Evidence for social referencing in young chimpanzees (Pan troglodytes)

A captive chimpanzee group was observed in order to determine the extent to which the social interactions of the infants and juveniles (18-50 months) were affected by their mothers' relationships with other adult group members. It was found that the young chimpanzees initiated more interactions with adults who interacted more with their mothers. A vast majority of those interactions occurred at significant distances from the mother. It is argued that these data imply a social-cognitive ability in young chimpanzees closely related to the human infant's ability to use its mother in 'social referencing'.     

Food Sharing in Pied Bare-Faced Tamarins (Saguinus bicolor bicolor): Development and Individual Differences

We investigated food sharing behavior in 5 litters of pied bare-faced tamarins (Saguinus bicolor bicolor)—8 infants, from 3 families—from 5 to 26 weeks of age. The frequency of sharing by parents in response to infant begging increased steadily from the age of 5 weeks to 16 weeks, and then declined. Offering of food by adults without prior infant begging occurred at very low frequencies throughout observations (1.5% of total items transferred). On average, infants received approximately equal amounts of food from transfers from others and by self feeding until about 20 weeks, after which self feeding began to predominate. Begging success—the proportion of infant begs which resulted in food sharing—remained relatively constant over time, at 60–70%. Overall, therefore, the frequency of food sharing seemed to be governed by changes in infant rather than adult behavior. There were individual differences between adults in their response to infant begging, but two of three fathers transferred significantly more food to infants than mothers did. The results of this study emphasize the existence of specific and individual differences in food-sharing behavior, which must be taken into account in explaining its importance in the reproductive strategies of the Callitrichidae.     

Effect of Removal from the Family Group on Feeding Behavior by Captive Callithrix jacchus

Common marmosets are omnivorous primates with a highly diversified diet. There is no study describing if and how the diet is learned. Infants get their first bits of solid food from other monkeys in the group, which suggests that they may need an introduction to food items by older individuals before including them in their diet. We assessed the acceptance of novel and familiar food items by common marmosets, both isolated and in their family groups. We tested adult, subadults and juveniles from 5 captive families while isolated and in their family groups. The test consisted of presenting for 10 min novel and familiar food items to isolated individuals or to the whole family. We recorded the latency to start eating and the number of food items ingested. When isolated, adults ate more novel and familiar food items than juveniles did. They also started eating sooner than juveniles did. When tested alone, all juveniles, except one, never tasted novel food, and juveniles ingested fewer familiar food items than adults did. When tested in their family groups, juveniles ingested more familiar and novel food than when they were isolated. Our results suggest that: 1. juvenile common marmosets show more food neophobia than adults do, especially when alone; 2. the family group may facilitate the acceptance of novel food items by juveniles; 3. the family group, besides promoting the acceptance of novel food, may also increase its ingestion; and 4. dietary acquisition in Callithrix jacchus involves social facilitation.     

Social influences on the development of foraging behavior in free-living common marmosets (Callithrix jacchus)

In this study we investigated the extent and pattern of social influences (i.e., the use of a conspecific as a model) on the foraging behavior of immature, wild common marmosets (Callithrix jacchus) as a function of the age of individuals. We compared the foraging activities and interactions with subadult and adult group members (older than 15 months) of young infants (1-2 months old), older infants (3-4 months old), and juveniles (5-10 months old). In addition to measuring the intensities of model-independent foraging (MIF) and merely paying attention to the model's foraging activities, we examined the frequencies of three types of model-dependent foraging (MDF): "follow the model", "manipulate the same object", and "forage together". We found that older infants were the most attentive and most socially-influenced foragers among the three age categories in absolute terms, but were not more attentive than young infants given their low foraging activity. Juveniles, in contrast, tended to have reduced overall foraging intensity compared to infants, but showed relatively more MDF in cases in which they observed subadult or adult models. Female models appeared to be more attractive than male models. These findings suggest that infants are generally more attentive to the foraging behavior of subadults and adults than juveniles, with the latter being more influenced when they had observed a model before. These subtle age-dependent effects of social foraging not only extend the assumption that young primates seek information from adults, they also suggest a complex interplay among physical and cognitive maturation, independence, and social dynamics.     

Seasonal Effects on Play Behavior in Immature <Emphasis Type="Italic">Saimiri sciureus</Emphasis> in Eastern Amazonia

Play behavior is prevalent among most mammalian young, particularly primates. Though several hypotheses address the function of play, researchers have documented information on the potential costs of play and of environmental effects on the occurrence of primate play less well during long-term field studies. I examine seasonal changes in play behavior of immature squirrel monkeys (Saimiri sciureus) across 4 age classes: infants, young juveniles, mid-juveniles, and late juveniles. I observed individuals during 12 mo in Eastern Brazilian Amazonia, an area characterized by highly seasonal rainfall. Play was strongly tied to seasonality, food availability, and changes in diet. The percentage of time spent playing was reduced in the dry season, a period characterized by low fruit availability and an increase in time spent foraging for prey. I suggest that the decrease in play behavior in the dry season is related both to a higher need for energy conservation and to increased time expended in foraging activities.     

Response to novel food in infant chimpanzees: Do infants refer to mothers before ingesting food on their own?

We investigated infant response toward novel food in captive chimpanzees under the condition in which they can explore such items freely together with their mother. Infants first approached novel foods rather than familiar ones when presented simultaneously. However, they did not ingest novel food immediately, but always sniff-licked it first. Infants tended to pay attention to their mothers before mouthing or ingesting novel foods themselves, but never did so with familiar ones. In response to the infant's activity, mother chimpanzees were tolerant rather than actively interfering. Those results imply that chimpanzee infants respond to novel foods in a neophobic way and refer to their mother for some kind of cue before attempting to ingest them.     

Feeding, foraging, and food sharing behavior of immature chimpanzees.

Observations of chimpanzees under naturalistic conditions show that nutritional autonomy increases as young individuals mature. Substantial proportions of feeding time are spent eating food obtained through solicitation. Food sharing at SOPF occurs among mother and infant pairs most frequently; less frequently between adult males and infants or juveniles, and least frequently between adult females and immature individuals. Mothers tend to share what their offspring cannot obtain independently while others primarily share what is easiest to replace. These patterns of solicitation and distribution of food are consistent with predictions based upon benefits to individuals through kin selection and/or energetic efficiency.