Supplemented howler monkeys eat less wild fruits,but do not change their activity budgets

Research on the influence of food supplementation on primate behavior has focused on terrestrial and semiterrestrial species. Its effects on highly arboreal species are poorly known. We assessed the influence of food supplementation on the feeding behavior and activity budget of four adult female and two adult male brown howler monkeys (Alouatta guariba clamitans) belonging to two groups (JA and RO) that inhabited periurban forest fragments in southern Brazil. We used the “focal‐animal” method during 6–8 full days per month from March to August 2017 (916 h of observation) to record the behavior of the study subjects. The feeding events of the focal individual were recorded using the “all occurrences” method. The supplementation was unevenly distributed during the day and accounted for 5–6% of all feeding events of male and female howlers, respectively. JA always received fruit in a platform, whereas RO had access to fruits and processed foods on roofs and directly from humans. The mean biomass of wild foods ingested by each adult per day was >300% higher than the ingested biomass of supplemented foods (females: 395 vs. 109 g/day; males: 377 vs. 120 g/day), but the ingestion rate of supplemented foods was ca. 400% higher than that of wild foods (females: 17 vs. 4 g/min; males: 19 vs. 5 g/min). The activity budgets of females and males were dominated by resting (66–72%) followed by feeding (18–14%), moving (12–11%), and socializing (2%). We found that food supplementation reduced the ingestion of wild fruits, but it did not affect the howlers’ need to ingest a given amount of leaves per day and the time spent resting, feeding, moving, and socializing.     

Limb use and preferences in wild orang-utans during feeding and locomotor behavior

Limited data are available on hemispheric lateralization in wild orang-utans. There has been only one previous investigation of limb preferences in wild orang-utans [Yeager, 1991]. We examined the lateralization of limb use in wild Bornean orang-utans (Pongo pygmaeus pygmaeus) with the aim of providing more insight into possible hemispheric specialization in wild nonhuman primates. Here, we report in detail on limb use and preference during arboreal locomotion between trees (N=6) and on feeding involving one limb (N=8) and two limbs (N=6). We distinguished between locomotion between overlapping trees (Type I) and locomotion involving gap crossing (Types II and III). For locomotion Type I, the six orang-utans showed no leading hand preference, however for locomotion Types II and III, all six showed significant right-hand preferences. All eight orang-utans showed individual hand preferences for reaching for food, but no significant group bias was found. Limb preferences for feeding involving two limbs (hand-hand or hand-foot) differed between juveniles (right hand-right foot), adult females (left hand-right hand) and adult males (right hand-left hand). Although not present for all tasks, the results indicate that orang-utans do show evidence of hemispheric specialization, but the use of the hands is not under a strong lateralized hemispheric control and is adaptable.     

Sex Differences in Feeding,Height, and Space Use in Hapalemur griseus

I investigated sex differences in feeding ecology in a wild group of Hapalemur griseus, gray bamboo lemur, in southeastern Madagascar. Males and females differed in daily dietary diversity, height use while feeding, and spatial position within the group. Based on all-occurrences of feeding bouts and 15-min point samples, the adult female had significantly higher daily dietary diversity indices than those of males. The female also fed at significantly lower heights than the males did. There are also significant differences between age classes with the subadult male exhibiting the lowest dietary diversity and feeding at the greatest heights. During feeding, the female stayed in closest proximity to both juveniles, whereas adult males were peripheral. In contrast, the males moved closer in proximity to the female when resting and traveling. These sex differences could be explained 1) by the metabolic cost of reproduction for females, 2) as strategies to mitigate the cost of feeding competition between males and females, 3) by male role performance as a predator detector, and 4) by different social priorities of males and females.     

Monitoring adult populations of the screwworm (Diptera: Calliphoridae) with feeding stations baited with liver.

Populations of the screwworm, Cochliomyia hominivorax (Coquerel), were monitored by capturing adults with hand nets and rooted liver set on the ground. Adults were marked and released. During the 61-d study conducted in a tropical dry forest in the dry season (January to March 1989), 2,640 individual females and 460 individual males were recorded at the four liver-baited stations. The total number of visits by females was 5,769 and by males 510. The mean number of unmarked adults per day was 44.1 females and 7.6 males in an area of approximately 2.59 km2. The mean percentage of marked flies that were recovered was 64.3%. The mean number of feeding stations visited, times recaptured, and days in the study area by individual females was 2.1, 2.4, and 4.5, respectively. Daily visitational patterns by both sexes at the feeding stations were bimodal with peaks occurring between the hours of 0730 to 0859 and 1500 to 1629. Flies were most active when the mean temperature was 29.9 degrees C; the majority of the visits occurred when air temperatures were between 26 and 33 degrees C. Most females attracted to feeding stations were nulliparous (70.7%) and mated (69.7%). Our results suggest that observing adults at feeding stations is a reliable method of obtaining data on the behaviour and population dynamics of indigenous populations of screwworm adults in tropical habitats. Although this method was labor intensive, the amount of data gleaned from the manipulation of wild populations more than compensated for such costs.     

Gender-specific orexigenic and anorexigenic mechanisms in rats

Feeding dysregulation may manifest as either under-nourishment (e.g., anorexia) or excessive eating leading to obesity. Recent studies have suggested a gender-related variance in weight maintenance in response to chronic disease or obesity-related dietary regimens. However it is unclear whether these gender differences in weight management are secondary to appetite-mediated food intake or alternative mechanisms (e.g., exercise, metabolism). In this study, we explored gender-dependent feeding and hormonal responses to dietary restriction (12-h fast) or to an inflammatory stimulus (LPS, 100 microg/kg b.w.; i.p.) in rats. In response to a 12 h fast, female rats increased (p<0.05) total daily food intake above that of male rats by primarily increasing nighttime feeding by 40%, as compared to 10% in males. Consistent with the increased food intake, fasting induced a greater percent increase in female as compared to male plasma ghrelin (141 vs. 65%, p<0.001). In response to LPS, both male and female rats showed similar reductions in total daily food consumption. However LPS (6 h) induced a greater percent increase in plasma leptin in female than male rats (230 vs. 33%, p<0.01), whereas ghrelin was similarly decreased in both females and males (66 vs. 44%). These findings demonstrate sexual dimorphic responses in feeding and appetite-associated hormonal responses to fasting or LPS treatment. Our findings suggest that therapeutic interventions with ghrelin or leptin must be modified according to gender in order to optimally achieve either weight loss for obesity or weight gain/maintenance for chronic illness-associated anorexia.     

Behavior, Diet, and Movements of the Sulawesi Crested Black Macaque (Macaca nigra)

We present the first field study of activity budgets, diet and ranging patterns of the Sulawesi crested black macaque, Macaca nigra, one of seven macaque species endemic to Sulawesi, Indonesia. We studied three crested macaque groups, ranging in size from 50 to 97 individuals, for 18 months in the Tangkoko-DuaSudara Nature Reserve, North Sulawesi. They spent 59% of the day moving and procuring food, especially fruits, and 41% of the day resting and socializing. Their diet is composed of more than 145 species of fruit (66% of observed feeding bouts), vegetative material (2.5%), invertebrates (31.5%), and occasional vertebrate prey. Group differences were more pronounced than seasonal or diurnal differences. Specifically, the largest group moved farther during the day, moved at a faster and more uniform rate, ate less fruit, rested more, and socialized less than the smaller groups did. The largest group had the largest home range, but it included less primary forest and more disturbed habitat than the ranges of smaller groups. There are individual differences in activity budgets of adult males and females in time spent moving, resting, feeding, and socializing that may reflect differences in reproductive strategies of males versus females. The behavior of large juveniles is more similar to that of adults than to that of small juveniles. Daily movements and use of home range are correlated with diet. Macaques moved shorter distances as the proportion of time spent feeding on fruit increased, and the top four dietary items accounted for most of the variance in entry into hectare blocks of home range.     

Studies of the metabolism,food consumption and assimilation efficiency of a small carnivore,the weasel (Mustela nivalis L.)

Summary The average respiratory quotient of weasels was 0.73. There were significant differences in average daily metabolic rate (ADMR) between the sexes and six experimental temperatures. As temperature decreased the mean ADMR increased, with a relatively greater rise for females. Regression equations of ADMR on temperature were Y=483.2–9.6X kcal/kg/day for males, and Y=625.3–15.0X kcal/kg/day for females. The minimum metabolic rate measured for males was 6.6 kcal/kg/h, and the maximum 25.7 kcal/kg/h. The relationship between ADMR and body weight varied with different temperatures, but was consistent with the hypothesis that ADMR was proportional to metabolic weight. The energetic costs of activity for my captive weasels were more than 20% of their daily total energy expenditure. Data on metabolism supported the conclusion that long, thin mustelids lose heat faster than normally-shaped mammals of the same weight.The calorific contents of foods, faeces and urine from feeding trials were determined. There were significant differences in the calorific content of faeces between the sexes, and of faeces and urine between diets.Four natural foods (Microtus, Apodemus, rabbit, starling) were offered during feeding trials. Daily food consumption varied between the diets, but small weasels always ate relatively more than large ones. Mean consumption was 0.33 g/g/day for males, and 0.36 g/g/day for females. Weasels on low-bulk diets (rabbit, starling) lost at least as much energy in urine as in faeces. There were significant differences in assimilation efficiency between the sexes and diets. The average efficiency for males was 78.2%, and 79.8% for females. Bulky foods lowered assimilation efficiencies by up to 9%.Daily energy requirements for maintenance calculated from ADMR data were compared with those from feeding trials. On the Microtus diet weasels expended 18.6–30.1% more energy on maintenance than predicted by the ADMR results, whereas on the other diets they expended 2.7–31.4% less energy. Estimates from ADMR data were probably more accurate.     

Tree structure and sex differences in arboreality among western lowland gorillas (Gorilla gorilla gorilla) at Bai Hokou, Central African Republic

The aim of six months of research in 1995 on the gorillas (Gorilla gorilla gorilla) at Bai Hokou, Central African Republic, was to study the effects of tree structure, relative numbers of arboreal feeding sites, and sex differences in body size on arboreal foraging. The analysis presented here also documents inter-annual variation in fruit availability and climbing by silverback gorillas by comparing the 1995 results to those from earlier research, 1990–1992. This analysis suggests that female gorillas maintain similar levels of arboreality in fruit-rich and fruit-poor seasons and years, but silverbacks may be more terrestrial when fruit is scarce or difficult to access. Trees of different shapes present different numbers of feeding sites to bigger males and smaller females. Male climbing is affected by the availability of fruit, and small trees with narrow crowns that lend easy access to fruit from the core. This study suggests that the energetics of vertical climbing and biomechanical constraints imposed by small branch feeding sites in the periphery of trees may constrain the arboreal behavior of male gorillas. Fine-tuned comparisons of food availability, tree structure, and variation in social context of behavior across habitats, will assist efforts to understand differences in ecology among populations and species of African apes.     

Feeding ecology of mandrills (Mandrillus sphinx) in campo animal reserve,Cameroon

A field study on the ecology of mandrills (Mandrillus sphinx) was carried out for 28 months in Cameroon. Fresh food remnants and large quantities of fresh feces were collected by following the groups. Analyses of these products indicated that fruit (including seeds), monocotyledonous plant leaves and insects (especially ants and termites), were frequently eaten. Mandrills mostly ate the plant and animal foods in the lower forest stratum and on the ground. Fallen seeds and monocotyledonous plant leaves were eaten more frequently in the minor fruiting season than in the major fruiting season presumably to compensate for the shortage of fresh fruit during the former. Daily travel distances were shorter during the minor fruiting season than during the major fruiting season, because in the minor fruiting season mandrills forage for small food items, such as the new leaves and piths of monocotyledons and fallen seeds which are sparsely distributed on the ground, while in the major fruiting season they search for widely distributed food such as fruit. The daily pattern of group movement and a food intake experiment suggest that mandrills move and feed continuously throughout the day. Use of fallen seeds and monocotyledonous plant leaves appears to enable mandrills to maintain a terrestrial life in the tropical rain forest. The feeding and ranging characteristics of mandrills are basically similar to those of other baboon species in open land, though their environments differ extremely.     

Handedness in nature: first evidence on manual laterality on bimanual coordinated tube task in wild primates

Handedness is a defining feature of human manual skill and understanding the origin of manual specialization remains a central topic of inquiry in anthropology and other sciences. In this study, we examined hand preference in a sample of wild primates on a task that requires bimanual coordinated actions (tube task) that has been widely used in captive primates. The Sichuan snub-nosed monkey (Rhinopithecus roxellana) is an arboreal Old World monkey species that is endemic to China, and 24 adult individuals from the Qinling Mountains of China were included for the analysis of hand preference in the tube task. All subjects showed strong individual hand preferences and significant group-level left-handedness was found. There were no significant differences between males and females for either direction or strength of hand preference. Strength of hand preferences of adults was significantly greater than juveniles. Use of the index finger to extract the food was the dominant extractive-act. Our findings represent the first evidence of population-level left-handedness in wild Old World monkeys and broaden our knowledge on evaluating primate hand preference via experimental manipulation in natural conditions.     

Age differences in food intake and dietary selection of wild male Japanese macaques

Age differences in food intake and dietary selection were studied for 8 months among wild male Japanese macaques (Macaca fuscata) under non-predatory situations. Juveniles' feeding time was longer than adult males' in some months, in particular in mating seasons, but did not differ in the other months. Juveniles' feeding speed was slower than that of adult males. However, the age difference in average feeding speed was smaller (90%) than that in expected daily energy expenditure (62–58%). The extent of age difference in feeding speed varied with the food type: the difference was large for fibrous foods, but small for fruits or seeds. As a consequence of the age differences in time spent feeding and feeding speed, the age difference in daily food intake was smaller than expected from metabolic demands. Thus, the hypothesis that juveniles are more vulnerable to starvation than adults was not supported among male Japanese macaques in predator-free Yakushima. Juveniles ate more animal matter, while adult males ate more fibrous foods.     

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.     

Raiders of the lost bark: orangutan foraging strategies in a degraded landscape

Deforestation is rapidly transforming primary forests across the tropics into human-dominated landscapes. Consequently, conservationists need to understand how different taxa respond and adapt to these changes in order to develop appropriate management strategies. Our two year study seeks to determine how wild Sumatran orangutans (Pongo abelii) adapt to living in an isolated agroforest landscape by investigating the sex of crop-raiders related to population demographics, and their temporal variations in feeding behaviour and dietary composition. From focal animal sampling we found that nine identified females raided cultivated fruits more than the four males. Seasonal adaptations were shown through orangutan feeding habits that shifted from being predominantly fruit-based (56% of the total feeding time, then 22% on bark) to the fallback food of bark (44%, then 35% on fruits), when key cultivated resources such as jackfruit (Artocarpus integer), were unavailable. Cultivated fruits were mostly consumed in the afternoon and evening, when farmers had returned home. The finding that females take greater crop-raiding risks than males differs from previous human-primate conflict studies, probably because of the low risks associated (as farmers rarely retaliated) and low intraspecific competition between males. Thus, the behavioral ecology of orangutans living in this human-dominated landscape differs markedly from that in primary forest, where orangutans have a strictly wild food diet, even where primary rainforests directly borders farmland. The importance of wild food availability was clearly illustrated in this study with 21% of the total orangutan feeding time being allocated to feeding on cultivated fruits. As forests are increasingly converted to cultivation, humans and orangutans are predicted to come into conflict more frequently. This study reveals orangutan adaptations for coexisting with humans, e.g. changes in temporal foraging patterns, which should be used for guiding the development of specific human-wildlife conflict mitigation strategies to lessen future crop-raiding and conflicts.     

Food competition in captive female sooty mangabeys (Cercocebus torquatus atys)

We studied the social and foraging behavior of two captive groups of sooty mangabeys under two different spatial food situations. These food conditions were clumped (food was placed in a box) and dispersed (food was dispersed over the entire enclosure). In each group five adult females and two adult males were observed. As a criterion for food competition, individual differences in the relative food intake were used. Adult female mangabeys had a linear, stable, and unidirectional dominance hierarchy. Access to food was rank dependent among females only under clumped food distribution, as current models of the evolution of primate social systems predict. However, feeding success appeared to be mediated not by female but by male agonistic behavior toward females. High-ranking females received relatively less aggression from males and could, therefore, stay and feed longer in the feeding area. Male tolerance of higher-ranking females seems to mediate female feeding success under restricted food resources. The establishment of a special relationship with a high-ranking male might, therefore, be a strategy to get better access to food. This study demonstrates that female competition for access to food should not be analyzed separately from male influences on females and suggests that a more integral role of males in socioecological models of the evolution of primate social systems should be considered.     

Social Structure of a Semi-Free Ranging Group of Mandrills (Mandrillus sphinx): A Social Network Analysis

The difficulty involved in following mandrills in the wild means that very little is known about social structure in this species. Most studies initially considered mandrill groups to be an aggregation of one-male/multifemale units, with males occupying central positions in a structure similar to those observed in the majority of baboon species. However, a recent study hypothesized that mandrills form stable groups with only two or three permanent males, and that females occupy more central positions than males within these groups. We used social network analysis methods to examine how a semi-free ranging group of 19 mandrills is structured. We recorded all dyads of individuals that were in contact as a measure of association. The betweenness and the eigenvector centrality for each individual were calculated and correlated to kinship, age and dominance. Finally, we performed a resilience analysis by simulating the removal of individuals displaying the highest betweenness and eigenvector centrality values. We found that related dyads were more frequently associated than unrelated dyads. Moreover, our results showed that the cumulative distribution of individual betweenness and eigenvector centrality followed a power function, which is characteristic of scale-free networks. This property showed that some group members, mostly females, occupied a highly central position. Finally, the resilience analysis showed that the removal of the two most central females split the network into small subgroups and increased the network diameter. Critically, this study confirms that females appear to occupy more central positions than males in mandrill groups. Consequently, these females appear to be crucial for group cohesion and probably play a pivotal role in this species.     

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.     

Stomach temperature telemetry reveals temporal patterns of foraging success in a free-ranging marine mammal

1. We studied feeding frequency in free-ranging grey seals using stomach temperature telemetry to test if previously reported sex differences in the diving, movement and diet were reflected in the temporal pattern of foraging success. 2. Data were retrieved from 21 of 32 grey seals from 1999 to 2001, totalling 343 days and 555 feeding events, with individual record length varying from 2 to 40 days (mean: 16.33 +/- 2.67 days/seal). 3. Seals fed on 57.8 +/- 6.46% of days sampled and had an average of 1.7 +/- 0.26 meals per day, but individual variability was apparent in the temporal distribution of feeding as evidenced by high coefficients of variation (coefficient of variation = 69.0%). 4. Bout analysis of non-feeding intervals of six grey seals suggests that feeding intervals of individuals were varied and probably reflect differences in prey availability. Grey seals tended to have many single feeding events with long periods separating each event, as would be expected for a large carnivore with a batch-reactor digestive system. 5. We found significant sex differences in the temporal distribution of feeding. The number of feeding events per day was greater in males (2.2 +/- 0.4 vs. 1.0 +/- 0.2), as was time associated with feeding per day (56.6 +/- 5.8 min vs. 43.9 +/- 9.4 min). 6. The number of feeding events varied with time of day with the least number occurring during dawn. Feeding event size differed significantly by time of day, with greater meal sizes during the dawn and the smallest meals during the night. 7. The length of time between meals increased with the size of the previous meal, and was significantly less in males (541.4 +/- 63.5 min) than in females (1092.6 +/- 169.9 min). 8. These results provide new insight into the basis of sex differences in diving and diet in this large size-dimorphic marine predator.     

Sex‐specific food provisioning in a monomorphic seabird,the common guillemot Uria aalge: nest defence,foraging efficiency or parental effort?

Sexual differences in food provisioning rates of monomorphic seabirds are well known but poorly understood. Here, we address three hypotheses that attempt to explain female-biased food provisioning in common guillemots Uria aalge : (1) males spend more time in nest defence, (2) females have greater foraging efficiency, and (3) males allocate a greater proportion of foraging effort to self-maintenance. We found that males spent no more time with chicks than females but made longer trips and travelled further from the colony. There was extensive overlap between sexes in core foraging areas, indicating that females were not excluding males from feeding opportunities close to the colony. However, as a result of their longer trips, the total foraging areas of males were much greater than those of females. There was no difference between sexes in overall dive rate per hour at sea, in behaviour during individual dives or in a number of other measures of foraging efficiency including the frequency, depth and duration of dives and the dive: pause ratio during the final dive bout of each trip, which was presumably used by both sexes to obtain prey for the chick. These data strongly suggest that sexes did not differ in their ability to locate and capture prey. Yet males made almost twice as many dives per trip as females, suggesting that males made more dives than females for their own benefit. These results support the hypothesis that female-biased food provisioning arose from a difference between sexes in the allocation of foraging effort between parents and offspring, in anticipation of a prolonged period of male-only post-fledging care of the chick, and not from differences in foraging efficiency or time spent in nest defence.     

The effects of sex,age, season and habitat on diet of the red fox <Emphasis Type="Italic">Vulpes vulpes</Emphasis> in northeastern Poland

The diet of the red fox Vulpes vulpes was investigated in five regions of northeastern Poland by stomach content analysis of 224 foxes collected from hunters. The red fox is expected to show the opportunistic feeding habits. Our study showed that foxes preyed mainly on wild prey, with strong domination of Microtus rodents, regardless of sex, age, month and habitat. Voles Microtus spp. were found in 73% of stomachs and constituted 47% of food volume consumed. Other food items were ungulate carrion (27% of volume), other mammals (11%), birds (9%), and plant material (4%). Sex- and age-specific differences in dietary diversity were found. Adult males and juvenile foxes had larger food niche breadths than adult females and their diets highly overlapped. Proportion of Microtus voles increased from autumn to late winter. Significant habitat differences between studied regions were found. There was a tendency among foxes to decrease consumption of voles with increasing percentage of forest cover. Based on our findings, red foxes in northeastern Poland can be recognized as a generalist predators, consuming easily accessible and abundant prey. However, high percentage of voles consumed regardless of age, sex, month, or habitats may indicate red fox specialization in preying on Microtus rodents.     

Kin Recognition and Maternal Care under Restricted Feeding in House Mice (Mus domesticus)

This study tests the hypothesis that female house mice (F1 generation of wild caught Mus domesticus) should preferentially invest in own offspring if confronted with young of different degrees of relatedness. The maternal behaviour of females with litters of 4 own and 4 unrelated alien young (cross-fostered at day 1 of lactation) was analysed during a lactation period of 22 days both under ad libitum and under restricted feeding (food was restricted by 20%). Cross-fostering and restricted feeding had no effect on the amount of time spent nursing until weaning. Under both feeding conditions the females did not differ in their maternal behaviour towards own and alien young: there were no significant differences either in the amount of time spent nursing own versus alien pups or in the time spent licking own versus alien young. Weight gain of own and alien = wild littermates did not differ significantly in mixed litters and was similar both under ad libitum and under restricted feeding. Such indiscriminate behaviour might be adaptive if female house mice prefer to communally nest with a relative and thus improve their inclusive fitness by investing in own and related offspring in a communal nest. Under moderate restricted feeding females could not wean the entire litter but reduced litter size by cannibalizing on average 2.7 pups (75% of the pups were killed when they were 4–8 days old). Females with cross-fostered litters killed as many own as alien young. This suggests that females cannot discriminate between own and unrelated young if cross-fostering takes place at day 1 of lactation. Besides testing kin recognition abilities, the experiments also allow analysis of the weaning strategy of females under food shortage. Under restricted feeding, body weight of the females was significantly lower during middle lactation than under ad libitum feeding. Weaning weight of young in reduced litters under food restriction (9–10 g) did not differ significantly from weaning weight of young in litters of 7–10 young, but was lower than that of young in similar sized litters (litter size 6), under ad libitum feeding. The maternal behaviour of cannibalizing some young under food shortage can be interpreted as a weaning strategy which results in the largest number of offspring that can be raised to a minimal weaning weight of 9–10 g. Such a weaning strategy might represent a favourable trade-off between number and size of young produced.