Tactics of care for young infants by forest-living ruffed lemurs (Varecia variegata variegata): Ground nests, parking, and biparental guarding

Nest construction in mammals: a review of the patterns of construction and functional roles

Nesting behaviour in mammals has been investigated in a wide variety of species but to date there has not been any scholarly review of the incidence and roles of these nests. Not all mammals build nests but, while some large species regularly build nests, nest-building behaviour is more commonly associated with small mammals weighing less than a kilogram. Quantitative data for the amounts of different materials used in a nest are rarely reported but mammal nests are typically constructed from fresh (rather than dead) plant materials. Animal-derived materials seem to be rare in nests, but anthropogenic materials are reported. Few studies have examined the roles these different materials play but more physically robust materials provide support for the structure. Many mammal nests have maternity roles, but a variety of other roles were recognized. A wide range of mammalian orders use nests for resting and environmental protection. Less common roles were as sites for torpor or hibernation, or as a refuge from predation, or the materials may have anti-parasite properties. These different roles were often not mutually exclusive. It is hoped that this review will stimulate interest in the functional properties of mammalian nests. It also suggests various themes that would be interesting areas for future research. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'.

Forest access restores foraging and ranging behavior in captive sifakas

Captive wildlife benefit from ecologically informed management strategies that promote natural behaviors. The Duke Lemur Center has pioneered husbandry programs rooted in species' ecology for a diversity of lemurs, including housing social groups in multiacre forest enclosures. We systematically document the foraging and ranging patterns of Coquerel's sifakas (Propithecus coquereli) living in these forest enclosures. Coquerel's sifakas are seasonal frugo-folivores that exhibit striking feeding flexibility in the wild. They are also one of the few members of the Indriidae family to persist in captivity. During all-day follows in the spring and summer of 2 consecutive years, we tracked the behavior of 14 sifakas in six forest enclosures. The sifakas' ranging and foraging patterns reflected those of wild sifakas in western Madagascar: On average, DLC sifakas occupied 3-day home ranges of 1.2 ha, traveled 473 m/day, and spent 26% of their time foraging for wild foodstuffs. The sifakas foraged most for young and mature leaves, fruits, nuts, and flowers from 39 plant species, especially red maple (Acer rubrum), tulip poplar (Liriodendron tulipifera), black locust (Robinia pseudoacacia), grapevine (Vitis rotundifolia), hickory (Carya spp.), and white oak (Quercus alba). Foraging patterns varied across seasons, enclosure areas, and groups, potentially reflecting differences in phenology, microhabitats, and individual preferences. While demonstrating that captive-bred primates express wild-like behaviors under ecologically relevant conditions, our results underscore the feeding flexibility of the Coquerel's sifaka. Captive wildlife exhibiting the range of species-specific behaviors are key resources for ecological research and might be best suited for future reintroductions.

Enriched sleep environments lengthen lemur sleep duration

Characteristics of the sleep-site are thought to influence the quality and duration of primate sleep, yet only a handful of studies have investigated these links experimentally. Using actigraphy and infrared videography, we quantified sleep in four lemur species (Eulemur coronatus, Lemur catta, Propithecus coquereli, and Varecia rubra) under two different experimental conditions at the Duke Lemur Center (DLC) in Durham, NC, USA. Individuals from each species underwent three weeks of simultaneous testing to investigate the hypothesis that comfort level of the sleep-site influences sleep. We obtained baseline data on normal sleep, and then, in a pair-wise study design, we compared the daily sleep times, inter-daily activity stability, and intra-daily activity variability of individuals in simultaneous experiments of sleep-site enrichment and sleep-site impoverishment. Over 164 24-hour periods from 8 individuals (2 of each species), we found evidence that enriched sleep-sites increased daily sleep times of lemurs, with an average increase of thirty-two minutes. The effect of sleep-site impoverishment was small and not statistically significant. Though our experimental manipulations altered inter-daily stability and intra-daily variability in activity patterns relative to baseline, the changes did not differ significantly between enriched and impoverished conditions. We conclude that properties of a sleep-site enhancing softness or insulation, more than the factors of surface area or stability, influence lemur sleep, with implications regarding the importance of nest building in primate evolution and the welfare and management of captive lemurs.

Lifespan decreases with proportion of sons in males but not females of zoo-housed tigers and lemurs

Several studies have shown higher costs of rearing sons than daughters in mammals where males are larger than females. These studies typically focus on females by examining how the offspring sex ratio during a single reproductive event affected mothers' subsequent reproduction or survival probability. Here, we examine relationships between offspring sex ratio during single or multiple reproductive events and several survival metrics in mothers and fathers, using data from zoo-housed tigers (Panthera tigris) and ruffed lemurs (Varecia sp.). Our analyses failed to reveal an overall cost of reproduction or a higher cost of sons to mothers. In male ruffed lemurs, the proportion of sons produced during early life (before 10 years old) was negatively correlated with lifespan later in life. In tigers, males with a higher proportion of sons during their lifetime had shorter lifespans. One likely mechanism is the difference in testosterone levels between males: a high concentration of testosterone can increase the proportion of sons and compromise immune function. Our results suggest studies in wild populations should address the outstanding challenge of understanding consequences of sex allocation for males, and open an opportunity to predict lifespan in an applied conservation context.

A description of nesting behaviors, including factors impacting nest site selection, in black-and-white ruffed lemurs (Varecia variegata)

Nest site selection is at once fundamental to reproduction and a poorly understood component of many organisms' reproductive investment. This study investigates the nesting behaviors of black-and-white ruffed lemurs, Varecia variegata, a litter-bearing primate from the southeastern rainforests of Madagascar. Using a combination of behavioral, geospatial, and demographic data, I test the hypotheses that environmental and social cues influence nest site selection and that these decisions ultimately impact maternal reproductive success. Gestating females built multiple large nests throughout their territories. Of these, females used only a fraction of the originally constructed nests, as well as several parking locations as infants aged. Nest construction was best predicted by environmental cues, including the size of the nesting tree and density of feeding trees within a 75 m radius of the nest, whereas nest use depended largely on the size and average distance to feeding trees within that same area. Microhabitat characteristics were unrelated to whether females built or used nests. Although unrelated to nest site selection, social cues, specifically the average distance to conspecifics' nest and park sites, were related to maternal reproductive success; mothers whose litters were parked in closer proximity to others' nests experienced higher infant survival than those whose nests were more isolated. This is likely because nesting proximity facilitated communal crèche use by neighboring females. Together, these results suggest a complex pattern of nesting behaviors that involves females strategically building nests in areas with high potential resource abundance, using nests in areas according to their realized productivity, and communally rearing infants within a network of nests distributed throughout the larger communal territory.

Maternal reproductive senescence shapes the fitness consequences of the parental age difference in ruffed lemurs

In humans, pronounced age differences between parents have deleterious fitness consequences. In particular, the number of children is lower when mothers are much older than fathers. However, previous analyses failed to disentangle the influence of differential parental age per se from a direct age effect of each parent. In this study, we analyse the fitness consequences of both parental age and parental age differences on litter size and offspring survival in two closely related species of lemurs living in captivity. As captive lemurs do not choose their reproductive partner, we were able to measure litter size and offspring survival across breeding pairs showing a wide range of parental age differences. However, we demonstrated that the effect of the parental age difference on litter size was fully accounted for by female reproductive senescence because females mating with much younger males were old females. On the other hand, both parental age difference and female reproductive senescence influenced offspring survival. Our results emphasize the importance of teasing apart the effect of parental reproductive senescence when investigating the health and fitness consequences of parental age differences and also provide new insights for conservation programmes of endangered species.

Infant nest and stash sites of variegated lemurs (Varecia rubra): The extended phenotype

Very few primate species give birth to litters and build nests in which to care for them. Those that do are small-bodied, nocturnal, and solitary. Variegated lemurs are exceptional in that they bear litters in arboreal nests, yet are relatively large-bodied, day-active, and gregarious. Furthermore, they raise their young cooperatively and practice absentee parenting; non-clinging young are transported orally and periodically stashed in arboreal spots that are supportive, sheltered, and usually concealed. Following birth, infant nest and stash trees were mapped, measured, and taxonomically identified in a population of red variegated lemurs in Masoala National Park. About 40 trees were used per litter for nesting and stashing young in adjacent, non-overlapping core areas within the community. These were the largest trees in the forest, even larger than those used for feeding. Furthermore, most occur in valleys and are laced with lianas, creating sites that buffer young from predation, accidental falls, and to some degree, thermal stress. In combination, the number of nest and stash trees used per litter, their characteristics, and their geo-spatial arrangement indicate that such sites are both select and limited in the landscape, exposing the dependence of red variegated lemurs on intact forest canopies for raising non-clinging young within the context of an absentee parenting system. Nest and stash sites are in effect Varecia's extended phenotype. Logging of large trees in Madagascar's eastern rain forests is considered a major factor resulting in local extinctions of variegated lemurs because they rely heavily upon large, mature trees for fruit. However, this study suggests that removal of large trees may more directly precipitate local extinctions by impeding their ability to reproduce. Long-term survival of red variegated lemurs will depend upon efforts to end harmful timber extraction in its remaining stronghold, the Masoala Peninsula.

Allonursing in white-faced capuchins (Cebus capucinus) provides evidence for cooperative care of infants

Allonursing is a highly cooperative behaviour that may have important fitness consequences for the infant while the benefits to the allomother are less clear. To investigate the function of this behaviour, we compared patterns of allonursing and nursing exhibited by white-faced capuchin monkeys (Cebus capucinus). We used a linear mixed model approach to analyse data collected on 21 infants from six social groups in Sector Santa Rosa, Costa Rica. Infants nursed at higher rates and for longer durations from their mothers than from allonurses. They also allonursed at higher rates from lactating and non-lactating parous females than from nulliparous females and at higher rates from maternally related female allonurses than other females. We found no observed effect of adult female rank or infant sex. We conclude that infant white-faced capuchins engage in allonursing as a means to acquire additional milk, and that participating allonurses may benefit from increased inclusive fitness.

Leaf nest use and construction in the golden-brown mouse lemur (Microcebus ravelobensis) in the Ankarafantsika National Park

The use of leaf nests has been documented in several mouse lemur species over the last few decades, including the golden-brown mouse lemur. Nest construction, however, has only rarely been observed and detailed descriptions of this process are lacking so far. We aim to determine the relative importance of leaf nests as shelters for the golden-brown mouse lemur, and to test predictions concerning the role of thermoregulation, safety (i.e., protection of infants), and of interspecific competition with the sympatric gray mouse lemurs in regulating nest use. Finally, we intend to clarify whether and how Microcebus ravelobensis constructs the nests, and we provide physical descriptions of seven leaf nests. Nocturnal focal observations were carried out from May 2007 to January 2008 on 18 females, and sleeping sites were regularly monitored during a six-month period. Data were collected from two study sites, one with exclusive presence of M. ravelobensis, and one with co-existence of the two mouse lemur species. Sixty-five out of 379 identified daily sleeping sites were leaf nests. These represented a total of 35 different leaf nests, used by 15 out of 18 females. The relative leaf nest use differed between sites during five out of six months, but without a consistent pattern. Interspecific competition can therefore not explain leaf nest use. Leaf nest use differed seasonally and may be partly explained by thermoregulatory advantages in the site with lower minimum temperatures. Nest use was furthermore higher than expected in both sites during the rearing season that indicates the role of nests in infant protection. For the first time, we could confirm that golden-brown mouse lemurs build leaf nests themselves. Nest building lasted between 46 and 68 min, which shows that this task is time consuming and therefore probably costly.

Morphometrics of wild black-and-white ruffed lemurs [Varecia variegata; Kerr, 1792]

This study presents the first detailed morphometric measurements of wild caught black-and-white ruffed lemurs (Varecia variegata) from the eastern rainforests of Madagascar and aims to quantify the morphological variation present throughout their recognized range. One hundred and forty-four adult and juvenile individuals from 15 sites were sampled for 20 cranial, dental and postcranial morphometric and body mass measurements. Data were collected from an equal number of male and female individuals sampled across seasons over a 7-year period (1999-2002, 2004-2006). Results indicate that adult body mass and morphometric measurements varied between sexes across sites; however, the only significant intersexual difference found was that females possessed, on average, longer tails than males. Contrary to previous studies, significant seasonal variation could not be detected in either male or female body mass or testicular volume (i.e., breeding vs. nonbreeding, food-scarce vs. food-abundant seasons). Measurements did, however, vary significantly by site and subspecies, though clinal variation could not explain these differences. The introduced population from Nosy Mangabe exhibited significantly lower body mass and overall body length than all other populations; however, this distinction may not have been attributable to natural variation, and may have instead resulted from the ecologically restrictive habitat (e.g., unusually high lemur population densities, limited food resources, ecological isolation) of this introduced population. Finally, although fore-to-hindlimb, brachium-to-thigh and hindlimb indices were comparable to previous values, forelimb indices calculated here deviate significantly from previous reports, placing V. variegata within the upper range of lemurid taxa. It is currently unknown whether this is an artifact of sampling methods (i.e., live vs. skeletal specimens) or whether this is an avenue that warrants further investigation.

Comparison of hind limb muscle mass in neonate and adult prosimian primates

Little ontogenetic data exist to indicate whether muscular organization of neonates reflects adult locomotion (e.g., leaping) or infant activities like clinging or the initial quadrupedal phase of locomotion that typifies most infant primates. In the present study, five species of primates with contrasting modes of locomotion were examined. Twenty-eight preserved neonatal and adult cadavers were studied by careful dissection of the hip, thigh, and leg muscles. Wet weights were taken of limb muscles after removal, and the muscles were combined into major functional groups (e.g., flexors, extensors) of each limb segment. Results demonstrate that the distribution of muscle mass within the thigh and within the leg are similar between neonates and adults for all species, with major groups varying by 5% or less in all but two age comparisons. Crural indices of the neonates are nearly identical to those of the adults, but leg/thigh muscle mass ratios were higher in the neonates. Species vary greatly in the percentage of adult limb segment muscle mass present in neonates, with Tarsius syrichta having the greatest percentage for all segments and two lemurids showing the least. These results primarily track differences in relative body mass at birth rather than developmental differences. The adaptive distribution of muscle, as discussed previously for adult prosimians, appears to be established at birth. Neonates of leaping species already have much larger quadriceps muscles than quadrupeds. Differences between large- and small-bodied leapers (e.g., pronounced superficial plantarflexor masses in tarsiers and pronounced deep plantarflexor masses in sifakas) also are present in neonates. Ratios of muscle mass over body mass are smaller in all neonates than in their adult counterparts, suggesting that the neonates are relatively poorly muscled, and that muscle mass must increase with positive allometry during growth.

The breeding system of wild red ruffed lemurs (Varecia rubra): a preliminary report

Captive studies have shown that ruffed lemurs (Varecia) have an unusual suite of reproductive traits combined with extremely high maternal reproductive costs. These traits include the bearing of litters, nesting of altricial young, and absentee parenting. To characterize the breeding system of this enigmatic lemur, reproductive traits must be contextualized in the wild. Here, I provide a preliminary report of mating and infant care in one community of wild red ruffed lemurs (Varecia rubra). Observations span a 15-month period covering two birth seasons and one mating season on the Masoala Peninsula, Madagascar. Factors that are not possible to replicate in captivity are reported, such as mating pattern, natality and mortality rates, the location of nests within the home range, and the structuring of infant care within a natural community. V. rubra at Andranobe have a fission-fusion, multifemale-multimale grouping pattern and a polygamous mating system. They do not mate monogamously or live strictly in family-based groups as suggested by previous workers. During the first 2 months of life, nests and infant stashing localities are situated within each mother's respective core area, and inhabitants of each core area within the communal home range provide care for young. As part of their absentee parenting system, infants are left in concealed, protected, and supportive spots high in the canopy, while mothers travel distantly. This practice is termed 'infant stashing'. Alloparenting appears to be an integral part of V. rubra's overall reproductive strategy in the wild, as it was performed by all age-sex classes. Among the alloparental behaviors observed were infant guarding, co-stashing, infant transport, and allonursing. Alloparenting and absentee parenting may mitigate high maternal reproductive costs. Furthermore, V. rubra may have a breeding system in which genetic partners (i.e., mating partners) do not always correspond to infant care-providers. Combined with recently available information on the behavioral ecology of wild ruffed lemurs, this preliminary report suggests directions for in-depth studies on Varecia's breeding system.

New developments in the behavioral ecology and conservation of ruffed lemurs (Varecia)

The papers in this issue were presented at a symposium during the 25th Annual Meeting of the American Society of Primatologists held in Oklahoma City, Oklahoma, in June 2002. This symposium brought together many of the scientists who have contributed to our knowledge of ruffed lemur ecology, behavior, and conservation in the past decade. One objective was to share and compare key findings about ruffed lemurs (Varecia) resulting from long-term field studies at various sites in Madagascar. A second objective was to cross-fertilize work being done in the wild with that being done in captivity, with the aim of advancing a common conservation mission for this critically endangered genus. Varecia is a prime candidate for synthetic assessments such as these because it has now been studied in both the northern and southern reaches of its geographic range, and has also been the focus of a captive-to-wild reinforcement project. The papers in this issue contribute to 1) the establishment of reference ranges for a suite of physiological parameters in healthy wild Varecia populations; 2) environmental enrichment aimed at preserving species-typical behaviors in captivity; 3) an understanding of how forest structure, floristic composition, and fruiting phenology in areas with differing disturbance histories correlate with the natural occurrence and abundance of Varecia; 4) primary knowledge concerning dominance relations between the sexes and group leadership in wild Varecia; and 5) primary knowledge concerning how wild Varecia, with their unusual reproductive pattern and heavy reliance on fruit, modulate their activity budgets seasonally and in tandem with reproductive stages.

Activity budgets and activity rhythms in red ruffed lemurs (Varecia rubra) on the Masoala Peninsula, Madagascar: seasonality and reproductive energetics

The activity budgets and daily activity rhythms of Varecia rubra were examined over an annual cycle according to season and reproductive stage. Given the relatively high reproductive costs and patchy food resources of this species, I predicted that V. rubra would 1) travel less and feed more during seasonal resource scarcity in an attempt to maintain energy balance, and 2) show sex differences in activity budgets due to differing reproductive investment. Contrary to the first prediction, V. rubra does not increase feeding time during seasonal food scarcity; rather, females feed for a consistent amount of time in every season, whereas males feed most during the resource-rich, hot dry season. The results are consistent with other predictions: V. rubra travels less in the resource-scarce cold rainy season, and there are some pronounced sex differences, with females feeding more and resting less than males in every season and in every reproductive stage except gestation. However, there are also some provocative similarities between the sexes when activity budgets are examined by reproductive stage. During gestation, female and male activity budgets do not differ and appear geared toward energy accumulation: both sexes feed and rest extensively and travel least during this stage. During lactation, activity budgets are geared toward high energy expenditure: both sexes travel most and in equal measure, and rest least, although it remains the case that females feed more and rest less than males. These similarities between female and male activity budgets appear related to cooperative infant care. The high energetic costs of reproduction in V. rubra females may require that they allot more time to feeding year round, and that their overall activity budget be more directly responsive to seasonal climate change, seasonal food distribution, and reproductive schedules.

Ontogenetic correlates of diet in Malagasy lemurs

There is a well-documented relationship between development and other life-history parameters among anthropoid primates. Smaller-bodied anthropoids tend to mature more rapidly than do larger-bodied species. Among anthropoids of similar body sizes, folivorous species tend to grow and mature more quickly than do frugivorous species, thus attaining adult body size at an earlier age. This pattern conforms to the expectations of Janson and van Schaik's "ecological risk aversion hypothesis," which predicts that rates of growth and maturation should vary in inverse relation to the intensity of intraspecific feeding competition. According to the ecological risk aversion hypothesis (RAH), species experiencing high intraspecific feeding competition will grow and mature slowly to reduce the risk of mortality due to food shortages. Species experiencing low levels of intraspecific feeding competition will shorten the juvenile period to reduce the overall duration of this high-risk portion of the life cycle. This paper focuses on development and maturation in lemurs. We show that folivorous lemurs (such as indriids) grow and mature more slowly than like-sized frugivorous lemurs (e.g., most lemurids), but tend to exhibit faster dental development. Their dental developmental schedules are accelerated on an absolute scale, relative to craniofacial growth, and relative to particular life-history landmarks, such as weaning. Dental development has a strong phylogenetic component: even those lemurids that consume substantial amounts of foliage have slower dental development than those indriids that consume substantial amounts of fruit. Implications of these results for the RAH are discussed, and an explanation for this hypothesis' failure to predict lemur growth schedules is offered. We propose that the differing developmental schedules of folivorous and frugivorous lemurs may reflect different solutions to the ecological problem of environmental instability: some rely on a strategy of low maternal input and slow returns, while others rely on a strategy of high maternal input and fast returns.

Circadian rhythms in diet and habitat use in red ruffed lemurs (Varecia rubra) and white-fronted brown lemurs (Eulemur fulvus albifrons)

Daily variation in niche use among vertebrates is attributed to a variety of factors, including thermoregulatory, reproductive, and nutritional requirements. Lemuriform primates exhibit many behavioral and physiological adaptations related to thermoregulation and sharp, seasonal reproduction, yet they have rarely been subjects of a quantitative analysis of circadian (or daily) rhythms in niche use. In this study, I document daily rhythms in diet and microhabitat use over an annual cycle in two sympatric, frugivorous lemurs, Varecia rubra and Eulemur fulvus albifrons. Data on diet, forest site, and forest height were recorded at 5-min time points on focal animals and divided into three time blocks for analysis (06:00-10:00 hr, 10:00-14:00 hr, and 14:00-18:00 hr). I employed multivariate tests of independence to examine daily rhythms in diet and microhabitat use according to sex, season, and reproductive stage. Throughout the day, V. rubra is frugivorous and dwells in the upper canopy, with notable departures (especially for females) during the hot seasons, gestation, and lactation. E. f. albifrons has heterogeneous daily rhythms of food choice and microhabitat use, particularly across seasons, and both sexes are equally variable. These daily rhythms in diet and microhabitat use appear related to thermoregulatory and nutritional requirements, seasonal food availability and circadian rhythms of plant (and possibly insect) palatability, predator avoidance tactics, and in the case of Varecia, to reproduction. Daily rhythms of food choice in V. rubra support two previously suggested hypotheses explaining why primates consume more nonfruit items late in the day, whereas those of E. f. albifrons are too variable to lend support to these hypotheses.

Niche separation in Varecia variegata rubra and Eulemur fulvus albifrons: II. Intraspecific patterns

Based on a year-long field study in northeastern Madagascar, I summarize annual patterns of niche use (food patch size, diet, forest height, and forest site) in two sympatric lemurs, Varecia variegata rubra and Eulemur fulvus albifrons. Furthermore, I examine intraspecific patterns of niche use according to sex, season, and reproductive stage in these two lemurs that differ in terms of energetic investment in reproduction. Lemurs as a group provide a special opportunity to test hypotheses concerning sex differences in niche use. Due to their body size monomorphism and seasonal, synchronous pattern of breeding, it is possible to directly evaluate whether sex differences in diet reflect high energetic investment in reproduction by females. Results confirm the hypothesis that intraspecific variation in niche use (e.g., sex differences, seasonal differences) would be more pronounced in V. v. rubra than in E. f. albifrons, due in large measure to the former's relatively high energetic investment in reproduction: 1a) Dietary sex differences in V. v. rubra are most pronounced during costly reproductive stages and involve acquisition of low-fiber, high-protein plant foods. Females of both species consume more seasonally available low-fiber protein (young leaves, flowers) relative to conspecific males during the hot dry season, but only in V. v. rubra females is this pattern also evident during gestation and lactation. 1b) The diets of female V. v. rubra and female E. f. albifrons are more similar to each other than are the diets of conspecific males and females in the case of V. v. rubra. This is not uniformly the case for female E. f. albifrons. This finding confirms a hypothesis put forward in Vasey ([2000] Am J Phys Anthropol 112:411-431) that energetic requirements of reproductive females drive niche separation more than do the energetic requirements of males. 1c) Both species synchronize most or all of lactation with seasonal food abundance and diversity. E. f. albifrons shows a more protracted period of synchrony, and this may contribute to its wide biogeographic distribution in Madagascar. 2) Sex differences and seasonal differences in microhabitat use reflect intraspecific patterns of thermoregulation, predator avoidance, and in the case of V. v. rubra, reproduction. One important factor selecting for body size monomorphism in lemurs appears to be the tight synchrony between lactation and periods of food abundance afforded by annual, seasonal breeding.

Milk composition reflects pattern of maternal care in prosimian primates

Hypothesized relationships between milk composition and life history traits were examined by analyzing mid-lactation milks of seven lemurs (Eulemur fulvus, E. macaco, E. rubriventer, E. mongoz, Varecia variegata, Hapalemur griseus, Lemur catta), three bushbabies (Otolemur crassicaudatus, O. garnettii, Galago moholi), and two lorises (Nycticebus coucang, Loris tardigradus); partial data were also obtained for the lemuroid Cheirogaleus medius. There were no significant differences in milk composition among species within either Eulemur or Otolemur, but the four genera for which multiple samples were available (Eulemur, Varecia, Otolemur, and Nycticebus) exhibited large composition differences. Eulemur milk was, on average, very dilute (9.9% dry matter) and low in energy (0.49 kcal/g). These milks contained 0.9% fat, 1.2% protein, and 8.4% carbohydrate on a fresh weight basis. Protein energy comprised only about 15% of total milk energy. Varecia had significantly higher dry matter (13.5%), fat (3.2%), protein (4.2%), gross energy (0.80 kcal/g), and protein energy:total energy ratio (28%) than Eulemur. Milks of the lorisoid genera Otolemur and Nycticebus were very similar, and both had significantly higher dry matter (18.3, 16.3%), fat (7.6, 7.0%), and gross energy concentration (1.27, 1.13 kcal/g) than either lemuroid genus. Otolemur milk was higher in protein than Nycticebus milk. We conclude that lorises, bushbabies, and perhaps cheirogaleids produce relatively rich, energy-dense milks in comparison with anthropoid primates. However, dilute milks appear to be uniformly found among species of Eulemur and perhaps in Lemur catta. The milk of Varecia (and perhaps Hapalemur) is intermediate in composition. Differences in milk composition among prosimians may be related to differences in maternal care: prosimians that carry their young during lactation produce more dilute milks than do species which leave their young unattended for prolonged periods. When looking at primates as a whole, however, the picture somewhat less clear, since the milks of some "parkers" like Varecia do closely resemble those of large anthropoid primates who carry their young.

Nests, tree holes, and the evolution of primate life histories

In contrast to the majority of primates, many prosimians, some New World monkeys, and the great apes rest in tree holes or self-constructed nests during their inactive periods. The goal of this comparative study was to examine possible functions of this interspecific variation. Information on resting behavior, maternal behavior, and basic life-history traits was gleaned from the literature and mapped onto a phylogenetic tree of primates for various comparative tests. Parsimony-based reconstructions revealed that only the use of nests or tree holes as shelters for young infants can be unequivocally reconstructed for various higher taxa, suggesting that it is functionally different from the use of shelters by adults (who may be accompanied by infants). Further reconstructions revealed that the ancestral primate was most likely nocturnal and solitary and produced a single infant that was initially left in a shelter and later carried orally to a parking place in the vegetation--a combination of traits exhibited by many living galagos. Evolutionary losses of the use of nests were concentrated among diurnal and nonsolitary taxa and weakly associated with evolutionary increases in body size. Thus, protective functions of nests or tree holes used by prosimians are either secondary or there are alternative ways of obtaining protection. Because the evolution of larger litters was significantly associated with the presence of shelters, the presence of relatively altricial young among prosimians best explains the use of nests and tree holes, which are in most but not all cases also used by adults. These shelters therefore play an integral part in the life-history strategies of primitive primates and their ancestors and evolved secondarily among anthropoids for other purposes.

Part-Time Fostering by a Pair of Black and White Ruffed Lemurs (Varecia Variegata Variegata)

Twin infant black and white ruffed lemurs, male and female, were fostered on a part-time basis, in conjunction with hand-rearing, with an adult pair who were highly related to them. The adult female showed allomaternal behaviour towards the twins, although she did not attempt to suckle them. The adult male ignored the twins for the first few weeks but as they became more mobile and playful he frequently initiated play with one or both. Growth rates showed a significant trend when compared with parentally raised and hand-reared infants, with the fostered twins growing at rates intermediate between those found under the two other rearing methods. Fostering of rejected infants as a captive management strategy is advocated as an alternative to traditional hand-rearing techniques because of the welfare advantages to both infants and foster parents.

Nests, tree holes, and the evolution of primate life histories

In contrast to the majority of primates, many prosimians, some New World monkeys, and the great apes rest in tree holes or self-constructed nests during their inactive periods. The goal of this comparative study was to examine possible functions of this interspecific variation. Information on resting behavior, maternal behavior, and basic life-history traits was gleaned from the literature and mapped onto a phylogenetic tree of primates for various comparative tests. Parsimony-based reconstructions revealed that only the use of nests or tree holes as shelters for young infants can be unequivocally reconstructed for various higher taxa, suggesting that it is functionally different from the use of shelters by adults (who may be accompanied by infants). Further reconstructions revealed that the ancestral primate was most likely nocturnal and solitary and produced a single infant that was initially left in a shelter and later carried orally to a parking place in the vegetation--a combination of traits exhibited by many living galagos. Evolutionary losses of the use of nests were concentrated among diurnal and nonsolitary taxa and weakly associated with evolutionary increases in body size. Thus, protective functions of nests or tree holes used by prosimians are either secondary or there are alternative ways of obtaining protection. Because the evolution of larger litters was significantly associated with the presence of shelters, the presence of relatively altricial young among prosimians best explains the use of nests and tree holes, which are in most but not all cases also used by adults. These shelters therefore play an integral part in the life-history strategies of primitive primates and their ancestors and evolved secondarily among anthropoids for other purposes.

Infanticide risk and the evolution of male-female association in primates

Year-round association between adult males and females is common in primates, even though internal gestation and lactation predispose males to mate-desertion in the majority of mammals. Because there is little a priori support for alternative explanations, we hypothesized that permanent male-female association in primates serves to reduce the risk of infanticide by strange males whenever females and infants are closely associated. For a phylogenetic test of this hypothesis, we reconstructed the evolution of male-female and female-infant association among primates. The results of Maddison's concentrated changes test confirmed the prediction that mother-infant association, as opposed to infant parking, and female-male association did not evolve independently. Changes in litter size and activity, in contrast, were not significantly associated with evolutionary changes in male-female association. Thus, we demonstrate a fundamental link between primate life history and social behaviour, explain the most basic type of variation in primate social organization, and propose an additional determinant of social organization that may also operate in other mammals.

Primate natal coats: a preliminary analysis of distribution and function

Pelage coloration of infants was compiled for 138 species of primates. Three functional hypotheses--alloparental, infant defense, and paternity cloak--for primate natal coats are tested. Neonatal pelage contrasted with adult pelage in over half of the species examined. Subtle or inconspicuous contrast was more common than flamboyant contrast. Natal coats began to change at 5.7 weeks and disappeared by 18.0 weeks postpartum on average. The first body part to lose natal coloration was the head and/or dorsum in the majority of species. Functional analyses provided no support for the only published hypothesis--alloparental--while providing partial support for two new hypotheses--infant defense and paternity cloak. A significant association between testes weight and natal coat contrast supports a link between mating system and infant contrast. This is discussed in terms of infanticide avoidance. Natal coats are proposed to be categorically differentiated into inconspicuous and flamboyant types, not differentiated by a continuous gradation, such as color. Subspecific differentiation and patterns of shared ancestry are assessed.

Group Formation and Behavioural Changes with Release to Free-Ranging in Red Ruffed Lemurs, Varecia Variegata Rubra

The social behaviour, ranging, and stereotypic behaviours of four red ruffed lemurs (one female, three males) was observed during group formation and release into a 2.25ha natural habitat enclosure at the Duke University Primate Center (DUPC). The female was immediately dominant to all males and there was no female-male affiliation during the initial stages of group formation. The group became identifiable as a unit after release to free-ranging when affiliation and group vocalizations began. Affiliation and vocalizations continued during subsequent recagings. Male dominance rank reflected relative age, but was subject to reversals. The stresses involved in release and group formation, however, can temporarily produce new aberrant behaviours which are soon replaced by normal behaviours. Once released into the large enclosure, stereotypic behaviours became infrequent but did not disappear. Other novel behaviours such as catatonic huddle and all male huddles were observed during release. Natural habitat enclosures can be important tools in the psychological well-being of captive primates.

Reproductive activity of ruffed lemurs (Varecia variegata variegata) in a Madagascar rain forest

Mating activity was observed during four breeding seasons in two groups of black and white ruffed lemurs (Varecia variegata variegata) living in lowland rain forest on Nosy Mangabe island, Madagascar. The onset of the May-July breeding season was signalled by behavioral changes in adult males. Males made forays outside their usual home ranges, were more aggressive to other males, and performed appetitive and other sex-specific behaviors more frequently. Females showed receptive and proceptive behaviors during a 1-2 day behavioral estrus. Ruffed lemurs mated monogamously, polyandrously, and polygynously. These observations do not support previous assertions that they live only in monogamous families. Limited evidence suggests females exercised mate choice and may have preferred familiar males.

Parental behavior and infant development in ruffed lemurs (Varecia variegata) in a northeast Madagascar rain forest

Parental behavior and infant development of black and white ruffed lemurs (Varecia variegata) were studied on Nosy Mangabe Island in northeast Madagascar. Ruffed lemur females produced twins, prepared nests for neonates in the trees, transported infants by mouth, and parked them in the trees. During two consecutive birth seasons, the average birth rate for nine females was 0.58. Two females reproduced in one social group. Lactating females spent most of their time resting with their infants or foraging for food. Infants developed rapidly and were fully mobile by 3-4 months. No female reproduced successfully in 2 consecutive years. In 1988, infant mortality within 3 months of birth was very high (64%). Accidental falls may have been one major cause. Adults of both sexes, including a reproductive female, exhibited alloparental behavior such as guarding infants and nonmaternal nursing. Alloparental care may increase the likelihood of infant survival. Some of these observations are not compatible with the idea that ruffed lemurs live in small pair-bonded groups, as other researchers have suggested.