Mother-offspring Interactions Research Articles

Development of juvenile goitered gazelle social behavior during the hiding period

In many ungulate species, social organization of adults is based on a linear dominance hierarchy, which in turn often positively correlates with age, body mass, and horn/antler size. In contrast to the social behavior of adults and specific mother-offspring interactions, the process of ungulate socialization in juveniles through contacts with other conspecifics is poorly understood, especially for hider species during their initial hiding period. Therefore, we investigated this process in goitered gazelle (Gazella subgutturosa), which is a typical hiding species, and analyzed all contacts between fawns and other conspecifics, omitting mother-young interactions, which are different by nature from other contacts and demands separate consideration. We found that apart from mothers, fawns interacted most often with nonmaternal adult females, less with other fawns and least with adult males and sub-adults. The frequency of the fawns’ contacts with conspecifics other than their mother increased during May and early-June, reaching a maximum in late-June, when fawns had the most mobility and independence from their mothers. This frequency decreased in July, when fawns spent more time with their mothers and when they mostly followed the mother’s behavior. The interactions of adult males and sub-adults of both sexes with fawns were the most aggressive in character, involving frequent displays of butting and chasing. Aggressive interactions were fewer between adult females and fawns, while fawn-fawn interactions had least aggressive displays. The main cause of interactions between fawns and other conspecifics were attempts of these young gazelles to suckle from other adults and sub-adults, especially frequently from nonmaternal females. Only fawn-fawn contacts were not linked to suckling and seemed to relate mostly to the development of social behavior and dominance hierarchies.

Influence of morning maternal care on the behavioural responses of 8-week-old Beagle puppies to new environmental and social stimuli

In mammals, maternal care represents a major constituent of the early-life environment and its influence on individual development has been documented in rodents, non-human primates, humans and recently in adult dogs. The quality and quantity of mother-offspring interactions exerts a multilevel regulation upon the physiological, cognitive, and behavioural development of the offspring. For example, in rats variations in maternal behaviour, such as mother-pup body contact and the amount of licking towards pups in the nest during the early days after parturition, influences the endocrine, emotional, and behavioural responses to stress in the offspring. This produces long-term consequences, which may remain into adulthood and can be transmitted to subsequent generations. Literature about maternal care in dogs and its effect on puppy behaviour is still scarce, although the topic is receiving a growing interest. The aim of the present study was to determine the effects of morning maternal care on behavioural responses of puppies to new environmental and social stimuli. In order to achieve this, maternal care (licking, ano-genital licking, nursing and mother-puppy contact) was assessed in eight litters of domestic dogs living in standard rearing conditions during the first three weeks post-partum. Puppies were subjected to two behavioural tests (arena and isolation tests) at 58–60 days of age, and their behavioural responses were video recorded and analysed. Data was analysed using multivariate analyses (PCA, PLS).During the isolation test, a higher level of maternal care was associated with more exploration and a higher latency to emit the first yelp; on the contrary, a lower level of maternal care was associated with increased locomotion, distress vocalisations and destructive behaviours directed at the enclosure.These results, comparable to those reported in laboratory rat models and to some extent to those recently reported in dog literature, highlight the importance of maternal care on the behavioural development of domestic dog puppies.

Levels of maternal care in dogs affect adult offspring temperament.

Dog puppies are born in a state of large neural immaturity; therefore, the nervous system is sensitive to environmental influences early in life. In primates and rodents, early experiences, such as maternal care, have been shown to have profound and lasting effects on the later behaviour and physiology of offspring. We hypothesised that this would also be the case for dogs with important implications for the breeding of working dogs. In the present study, variation in the mother-offspring interactions of German Shepherd dogs within the Swedish breeding program for military working dogs was studied by video recording 22 mothers with their litters during the first three weeks postpartum. The aim was to classify mothers with respect to their level of maternal care and to investigate the effect of this care on pup behaviour in a standardised temperament test carried out at approximately 18 months of age. The results show that females differed consistently in their level of maternal care, which significantly affected the adult behaviour of the offspring, mainly with respect to behaviours classified as Physical and Social Engagement, as well as Aggression. Taking maternal quality into account in breeding programs may therefore improve the process of selecting working dogs.

Maternal condition determines offspring behavior toward family members in the European earwig

Parental care confers benefits to juveniles but is usually associated with substantial costs for parents. These costs often depend on parental condition, which is thus considered as a key determinant of the level of parental care expressed during family life. However, how parental condition affects the behaviors that juveniles express toward their siblings and parents remains poorly explored. Here, we investigated these questions in the European earwig Forficula auricularia, an insect in which mothers provide extensive forms of care to their juveniles. We measured maternal body condition at egg hatching, subsequently manipulated maternal nutritional state, and finally assessed both food transfer among siblings and the nature of mother–offspring interactions. We also considered variation in brood size, an important parameter in family interactions. We found that food transfer among siblings increased with brood size when the tending mothers were in a deteriorated nutritional state. This effect was masked when the nutritional state of mothers was enhanced. The frequency of care-related behaviors that juveniles expressed toward their mother was higher when she was in a deteriorated rather than an enhanced nutritional state, while it overall increased with brood size. Finally, increasing values of maternal body condition entailed a shift from a positive to a negative association between maternal care behaviors and brood size, but only when the mothers’ nutritional state was deteriorated. Overall, our results demonstrate that parental condition and brood size do not only affect parental behaviors but can also be important and entangled drivers of offspring behaviors during family life.

Feces production as a form of social immunity in an insect with facultative maternal care.

BackgroundSocial animals have the unique capability of mounting social defenses against pathogens. Over the last decades, social immunity has been extensively studied in species with obligatory and permanent forms of social life. However, its occurrence in less derived social systems and thus its role in the early evolution of group-living remains unclear. Here, we investigated whether lining nests with feces is a form of social immunity against microbial growth in the European earwig Forficula auricularia, an insect with temporary family life and facultative maternal care.ResultsUsing a total of 415 inhibition zone assays, we showed that earwig feces inhibit the growth of two GRAM+ bacteria, two fungi, but not of a GRAM- bacteria. These inhibitions did not result from the consumed food or the nesting environment. We then demonstrated that the antimicrobial activity against fungus was higher in offspring than maternal feces, but that this difference was absent against bacteria. Finally, we showed that family interactions inhibited the antibacterial activity of maternal feces against one of the two GRAM+ bacteria, whereas it had no effect on the one of nymphal feces. By contrast, antifungal activities of the feces were independent of mother-offspring interactions.ConclusionThese results demonstrate that social immunity occurs in a species with simple and facultative social life, and thus shed light on the general importance of this process in the evolution of group-living. These results also emphasize that defecation can be under selection for other life-history traits than simple waste disposal.

Role of sensory, social, and hormonal signals from the mother on the development of offspring.

For mammals, sensory, social, and hormonal experience early in life is essential for the continuity of the infant's development. These experiences come from the mother through maternal care, and have enduring effects on the physiology and behavior of the adult organism. Disturbing the mother-offspring interaction by maternal deprivation (neglect) or exposure to adverse events as chronic stress, maltreatment, or sexual abuse has negative effects on the mental, psychological, physiological, and behavioral health. Indeed, these kinds of negative experiences can be the source of some neuropsychiatric diseases as depression, anxiety, impulsive aggression, and antisocial behavior. The purpose of this chapter is to review the most relevant evidence that supports the participation of cues from the mother and/or littermates during the postnatal preweaning period for the development of nervous system of the offspring. These findings come from the most frequently utilized experimental paradigms used in animal models, such as natural variations in maternal behavior, handling, partial maternal deprivation, and total maternal deprivation and artificial rearing. Through the use of these experimental procedures, it is possible to positively (handling paradigm), or negatively (maternal deprivation paradigms), affect the offspring's development. Finally, this chapter reviews the importance of the hormones that pups ingest through the maternal milk during early lactation on the development of several physiological systems, including the immune, endocrine systems, as well as on the adult behavior of the offspring.

Influence of the climatic environment and duration of labor on the mother-offspring interaction in Morada Nova sheep

Influence of the climatic environment and duration of labor on the mother-offspring interaction in Morada Nova sheep

Cadm1-Expressing Synapses on Purkinje Cell Dendrites Are Involved in Mouse Ultrasonic Vocalization Activity

Foxp2(R552H) knock-in (KI) mouse pups with a mutation related to human speech–language disorders exhibit poor development of cerebellar Purkinje cells and impaired ultrasonic vocalization (USV), a communication tool for mother-offspring interactions. Thus, human speech and mouse USV appear to have a Foxp2-mediated common molecular basis in the cerebellum. Mutations in the gene encoding the synaptic adhesion molecule CADM1 (RA175/Necl2/SynCAM1/Cadm1) have been identified in people with autism spectrum disorder (ASD) who have impaired speech and language. In the present study, we show that both Cadm1-deficient knockout (KO) pups and Foxp2(R552H) KI pups exhibit impaired USV and smaller cerebellums. Cadm1 was preferentially localized to the apical–distal portion of the dendritic arbor of Purkinje cells in the molecular layer of wild-type pups, and VGluT1 level decreased in the cerebellum of Cadm1 KO mice. In addition, we detected reduced immunoreactivity of Cadm1 and VGluT1 on the poorly developed dendritic arbor of Purkinje cells in the Foxp2(R552H) KI pups. However, Cadm1 mRNA expression was not altered in the Foxp2(R552H) KI pups. These results suggest that although the Foxp2 transcription factor does not target Cadm1, Cadm1 at the synapses of Purkinje cells and parallel fibers is necessary for USV function. The loss of Cadm1-expressing synapses on the dendrites of Purkinje cells may be associated with the USV impairment that Cadm1 KO and Foxp2(R552H) KI mice exhibit.

Parent–offspring conflict theory: An evolutionary framework for understanding conflict within human families.

Decades of research demonstrate that conflict shapes and permeates a broad range of family processes. In the current article, we argue that greater insight, integration of knowledge, and empirical achievement in the study of family conflict can be realized by utilizing a powerful theory from evolutionary biology that is barely known within psychology: parent-offspring conflict theory (POCT). In the current article, we articulate POCT for psychological scientists, extend its scope by connecting it to the broader framework of life history theory, and draw out its implications for understanding conflict within human families. We specifically apply POCT to 2 instances of early mother-offspring interaction (prenatal conflict and weaning conflict); discuss the effects of genetic relatedness on behavioral conflict between parents, children, and their siblings; review the emerging literature on parent-offspring conflict over the choice of mates and spouses; and examine parent-offspring conflict from the perspective of imprinted genes. This review demonstrates the utility of POCT, not only for explaining what is known about conflict within families but also for generating novel hypotheses, suggesting new lines of research, and moving us toward the "big picture" by integrating across biological and psychological domains of knowledge.

Mutual mother–offspring vocal recognition in an ungulate hider species (Capra hircus)

Parent-offspring recognition can be essential for offspring survival and important to avoid misdirected parental care when progeny mingle in large social groups. In ungulates, offspring antipredator strategies (hiding vs. following) result in differences in mother-offspring interactions, and thus different selection pressures acting on the recognition process during the first weeks of life. Hider offspring are isolated and relatively stationary and silent to avoid detection by predators, whereas follower offspring are mobile and rapidly mix in large social groups. For these reasons, hiders have been suggested to show low offspring call individuality leading to unidirectional recognition of mothers by offspring and followers high offspring call individuality and mutual recognition. We hypothesised that similar differences would exist in hider species between the hiding phase (i.e. unidirectional recognition) and the phase when offspring join social groups (i.e. mutual recognition). We tested these predictions with goats (Capra hircus), a hider species characterised by strong mother-offspring attachment. We compared the individuality of kid and mother calls, and the vocal recognition ability, during the early phase of life when kids are usually hidden and later when kids have typically joined social groups. Contrary to our predictions, we found that both kids and mothers had individualised contact calls and that mutual recognition existed even during the hiding phase. The large differences in the duration of the hiding phase and in the rate of mother-offspring interactions (possibly partially driven by domestication in some species) probably cause variations among hider species in the mother-offspring recognition process.

The richness of social stimuli shapes developmental trajectories: Are laboratory mouse pups impoverished?

The early environment is crucial for brain and behavior development. In particular, social experiences involving the mother and the peers are critical in shaping the adult individual. Though animal models of psychiatric disorders have widely investigated the relevance of the mother-offspring interaction, the peer interaction has so far been rarely studied. The communal nest (CN) is an innovative experimental strategy that favors a more comprehensive investigation of the long-term effects of both components. CN is a rearing condition employed by up to 90% of mouse females in naturalistic settings and consists of a single nest where two or more mothers keep their pups together and share care-giving. In a CN, the developing pup is exposed to high levels of both maternal care and interaction with peers. At adulthood, these mice display relevant changes in bran function and behavior, including high levels of neural plasticity markers, such as BDNF, and elaborate adult social competences. Overall, on the one hand, CN is an experimental approach complementary to the ones currently used that allows to investigate how the early environment determines developmental trajectories. On the other, it may represent a strategy to improve the study of animal models of psychiatric disorders characterized by social dysfunction, such as major depression, autism and attention deficit hyperactivity disorder. Indeed, the more elaborate social competences shown by these mice at adulthood may allow to better characterize deficits in the social domain induced by genetic and/or environmental manipulations.

Suckling behavior of eland antelopes (Taurotragus spp.) under semi-captive and farm conditions

Mother–offspring interactions soon after parturition play a key role in the survival of mammals. We investigated the suckling behavior of semi-captive Western Derby eland (Taurotragus derbianus derbianus) in a 60-ha enclosure covered by dense savanna vegetation in Senegal and farmed Common eland (T. oryx) on an open 2-ha pasture in the Czech Republic. We hypothesized that the basic pattern of suckling bout duration and mother–offspring interactions would be similar between species, but would vary in response to the environmental conditions and breeding system. During three calving periods, we observed the suckling of 27 and 23 calves of Derby and Common elands, respectively, between the ages of 1–5 months, and the interactions between mother and calf before and during suckling. Suckling bout duration increased with the age of the calves for both elands. However, in Derby elands we recorded longer suckling bouts in male than female calves and shorter suckling bouts in primiparous mothers than multiparous ones; no differences were found in farmed Common elands. The animals’ active approach to mother–offspring contact, for example naso–anal contact, and initiation and termination of suckling, resulted in longer suckling bouts in Derby elands. The results suggest that Derby elands that range over a large enclosure with dense vegetation cover adjust their maternal behavior in compliance with potential predator risk, facing a trade-off between nursing and vigilant behavior in the wild. The suckling behavior of farmed elands, on the other hand, reflects the conditions of captivity without predators and with the small available area enabling permanent visual contact of animals.

Epigenetics and parental effects

Parental effects are a major source of phenotypic plasticity and may influence offspring phenotype in concert with environmental demands. Studies of "environmental epigenetics" suggest that (1) DNA methylation states are variable and that both demethylation and remethylation occur in post-mitotic cells, and (2) that remodeling of DNA methylation can occur in response to environmentally driven intracellular signaling pathways. Studies of mother-offspring interactions in rodents suggest that parental signals influence the DNA methylation, leading to stable changes in gene expression. If parental effects do indeed enhance the "match" between prevailing environmental demands and offspring phenotype, then the potential for variation in environmental conditions over time would suggest a mechanism that requires active maintenance across generations through parental signaling. We suggest that parental regulation of DNA methylation states is thus an ideal candidate mechanism for parental effects on phenotypic variation.

Token transfer between mother and offspring chimpanzees (Pan troglodytes): mother–offspring interaction in a competitive situation

Chimpanzees can flexibly use tokens in cognitive tasks, but it is still unknown if they can share and/or compete over tokens as they do for food. This study aimed to evaluate the interactions spontaneously occurring between mother and offspring chimpanzees when tokens exchangeable for food were provided. Forty tokens were scattered on the floor in an experimental playroom. Three mother and offspring chimpanzee pairs were tested. Each token was exchangeable for a piece of food in a vending machine installed on the wall of the playroom. In the beginning of the study, both mother and offspring took tokens and exchanged them for pieces of food independently. Later, two offspring started to take more tokens than their mothers. At that time, the offspring whimpered or cried more often than during earlier sessions. This behavior compelled the mothers to abstain from taking tokens. The mothers sometimes shared their tokens with their offspring, or were tolerant of their offspring taking their tokens from their hand. For one pair, the offspring sometimes shared tokens with her mother when her mother begged for the tokens. These results suggest that chimpanzees' cognitive abilities enable them not only to use tokens, but also to compete for tokens, as they do for food. The results also suggest that token sharing between mother and offspring may be bidirectional and that transfer of tokens mainly occurs as a result of begging, although on some occasion offspring were able to obtain a token directly from his/her mother through tolerated scrounging.

Maternally inherited architecture in tertiary leaf beetles: paleoichnology of cryptocephaline fecal cases in Dominican and Baltic amber

Complex ethological adaptations and intraspecific interactions leave few fossil traces. We document three Dominican (20 million years old [myo]) and Baltic (45 myo) amber fossils that exhibit firm evidence of highly integrated interactions between mothers and offspring in the diverse camptosomate lineage of beetles (Chrysomelidae, leaf beetles). As in contemporary species, these hard cases were initially constructed by mothers, then inherited and retained by offspring, which then elaborate this protective domicile with an unusual but economical building material, their feces. The three fossils are classified in the Subfamily Cryptocephalinae; two are classified in the tribe Chlamisini based on morphological evidence-the flattened head lacking a sharp keel and long legs with simple recurved untoothed claws. These diagnostic features are not clearly visible in the third specimen to permit more refined identification. These fossils provide more precise paleontological dating of tribal nodes within the cryptocephaline radiation of leaf beetles. These fossils are the first and earliest evidence of mother-offspring interaction, building behavior, and fecal recycling in Camptosomata beetles and of inheritance of architectural structures in beetles.

Both maternal care and early peer-to-peer interactions shape adult social behaviour in the mouse

Event Abstract Back to Event Both maternal care and early peer-to-peer interactions shape adult social behaviour in the mouse Ivana D-Andrea1*, Francesca Cirulli1, Igor Branchi1 and Enrico Alleva1 1 Istituto Superiore di Sanita, Section of Behavioural Neurosciences, Department of Cell Biology and Neurosciences, Italy The critical role of early social experiences in shaping brain function and behavior in humans has been widely investigated in animal models exploiting paradigms affecting mother-offspring interaction, such as maternal deprivation and handling. However, these paradigms overlook a second key factor shaping the adult social behavior: peer interactions. In order to investigate the contribution of both factors we developed a new paradigm: Communal Nest(CN), consists in a single nest where three mouse mothers keep their pups together and share care-giving behavior from birth to weaning and mimics the natural ecological niche of the mouse species. According to previous studies, in the CN nest, maternal care and peer interactions are markedly increased compared to mice reared in standard laboratory rearing conditions(SN). In the present study, with the purpose of having several rearing conditions characterized by different levels of maternal care and peer interactions, in each CN nest, the 3 mothers gave birth with an interval between two consecutive deliveries of 3 days. Thus, each CN nest was formed by 3 different groups of animals: oldest, intermediate and youngest pups. We assessed, during the first 14 days of life, maternal behavior and peer interactions and, at adulthood, social behavior in the three CN groups and in SN mice. With regard to maternal behavior, CN-intermediate mice received less care compared to CN-old, CN-young and SN mice. By contrast, SN mice showed lower levels of peer interactions compared to all CN groups. At adulthood, in a social interaction test, CN-oldest and CN-youngest mice appear to have more elaborate social competencies, displaying the behavioural profile of either dominant or subordinate after significantly shorter time compared to CN-intermediate and SN mice. These findings suggest that both maternal care and peer interactions are critical in shaping social competences at adulthood.Contributed by EU project INTELLIMAZE to FC and EA. Conference: 41st European Brain and Behaviour Society Meeting, Rhodes Island, Greece, 13 Sep - 18 Sep, 2009. Presentation Type: Poster Presentation Topic: Poster presentations Citation: D-Andrea I, Cirulli F, Branchi I and Alleva E (2009). Both maternal care and early peer-to-peer interactions shape adult social behaviour in the mouse. Conference Abstract: 41st European Brain and Behaviour Society Meeting. doi: 10.3389/conf.neuro.08.2009.09.127 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 08 Jun 2009; Published Online: 08 Jun 2009. * Correspondence: Ivana D-Andrea, Istituto Superiore di Sanita, Section of Behavioural Neurosciences, Department of Cell Biology and Neurosciences, Rome, Italy, ivana.dandrea@iss.it Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Ivana D-Andrea Francesca Cirulli Igor Branchi Enrico Alleva Google Ivana D-Andrea Francesca Cirulli Igor Branchi Enrico Alleva Google Scholar Ivana D-Andrea Francesca Cirulli Igor Branchi Enrico Alleva PubMed Ivana D-Andrea Francesca Cirulli Igor Branchi Enrico Alleva Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Mother–Offspring Interactions in Zebu Cattle

The knowledge of the interaction between mother and offspring might contribute to enhance the welfare of the offspring and to improve the reproductive efficiency of the cow. However, there is still little information available about such interaction in some cattle breeds. A series of observational studies were set up, addressing the mother-offspring relationships of Nelore, Guzerat and Gyr cattle breeds. Firstly, the behaviour of cows and calves around the time of parturition was described, and then, the underlying factors that affect the calves' survival and development were studied. Special attention was given to the failure or delay in the first suckling. The results together are indicative of genetic variability for some studied variables, indicating the possibility of selection for calf vigour (using latency to stand up and latency to suckle as its indicators) and maternal ability (using percentage of time in contact with the calves), in spite of the estimates of heritability were low and presented high standard deviation for all variables. The individual variability in their suckling behaviour and the efficiency in first suckling cannot be explained by a single isolated underlying factor. By now, there are some results available, although there are many questions without answers. The field is still open for the development of future research.

Changing supply and demand by cross-fostering: effects on the behaviour of pups and mothers in guinea pigs, Cavia aperea f. porcellus, and cavies, Cavia aperea

The regulation of parental supply and offspring demand was modelled for altricial birds. The situation might differ for precocial species, where offspring can also feed themselves. We investigated the effect of supply and demand on mother–offspring interaction in precocials by cross-fostering pups between the domestic guinea pig and its ancestor, the cavy. The two are closely related, yet guinea pigs are heavier and produce more milk than cavies. We thus created a low-supply situation for pups raised by cavy mothers and a high-supply situation for pups raised by guinea pigs. Females nursing cavy pups confront low demand; those nursing guinea pig pups confront high demand. Pups in a high-supply situation showed more sucking attempts than pups in a low-supply situation, indicating a positive effect of supply on demand. High-demand pups showed more sucking attempts than low-demand pups. Mothers with high-demand pups nursed more frequently and spent more time nursing than mothers with low-demand pups. Milk production remained unaffected and timing of weaning was only slightly adjusted to the kind of pup fostered. Weaning was marked by decreasing of sucking attempts and maternal responsiveness and by increasing aggression. Mothers apparently received information about pup demand, but maternal state seemed to induce the weaning process largely independent of pup demands. The effect of supply on demand differed from predictions of current models. Differences in parent–offspring interaction in altricials and precocials deserve more research attention.

Mother–offspring competition promotes colonization success

Colonization is the crucial process underlying range expansions, biological invasions, and metapopulation dynamics. Which individuals leave their natal population to colonize empty habitats is a crucial question and is presently unresolved. Dispersal is the first step in colonization. However, not all dispersing individuals are necessarily good colonizers. Indeed, in some species, the phenotype of dispersers differs depending on the selective pressures that induce dispersal. In particular, kin-based interactions, a factor driving social evolution, should induce different social response profiles in nondispersing and dispersing individuals. Kin competition (defined here as between the mother and offspring) has been proven to produce dispersers with a particular phenotype that may enhance their colonizing ability. By using the common lizard (Lacerta vivipara), we conducted a multipopulation experiment to study the effect of kin competition on dispersal and colonization success. We manipulated mother-offspring interactions, which are the most important component of kin competition in the studied species, at the family and population levels and measured the consequences on colonization success. We demonstrate that mother-offspring competition at the population level significantly influences colonization success. Increased competition at the population level enhanced the colonization rate of the largest juveniles as well as the growth and survival of the colonizers. Based on these results, we calculated that kin-induced colonization halves the extinction probability of a newly initiated population. Because interactions between relatives are likely to affect the ability of a species to track habitat modifications, kin-based dispersal should be considered in the study of invasion dynamics and metapopulation functioning.

Development of Independence from the Mother in Gorilla gorilla gorilla

In gorillas, the mother takes full responsibility for carrying and feeding offspring, and lactational amenorrhea prevents her from investing in another offspring while suckling. Therefore, mothers should encourage immature gorillas to become gradually more independent until they are physically able to acquire sufficient resources, travel independently, and manage social relationships unaided. We investigated the development of independence in a population of wild western gorillas (Gorilla gorilla gorilla) at Mbeli Bai, Nouabale-Ndoki National Park, Republic of Congo. We observed the spatial proximity, the development of travel, patterns of suckling and weaning, and the nature of mother-offspring interactions for 42 immature gorillas to investigate the nature of the relationship between mother and offspring. Though mother-offspring distance and independent travel increased during immaturity, with few active interactions between the dyads, offspring still continued to suckle until a median age of 4.6 yr, longer than in mountain gorillas. The tolerance of the mother toward suckling by older offspring may reflect the importance of continued nutritional investment: the temporal nature of the diet of western gorillas means that succulent fruits—likely to be preferred weaning foods—are not always available. We propose that to buffer against potential fruit shortage, mothers continue to nurse their offspring to decrease the likelihood of death from care-dependent factors and to improve an offspring’s chances of survival.