The lack of female dominance in golden‐brown mouse lemurs suggests alternative routes in lemur social evolution

Female dominance is a well‐known trait of lemurs, although it has not been reported from all species and is still often unexplored, especially in the nocturnal species. We examined the intersexual dominance relationships in Microcebus ravelobensis, a congener of M. murinus who is well known for its female dominance. Given the many similarities in biology, it was predicted that M. ravelobensis should also possess female dominance. Seventeen unfamiliar male–female pairs were formed with animals captured in northwestern Madagascar and kept in a two‐cage setting (one cage for each animal) for up to 1 week. Four encounter experiments were conducted with each pair. In contrast to the expectations, females were not consistently dominant over their male partners. Only 3 of 17 dyads developed a clear agonistic asymmetry, among which were two cases of male dominance and only one case of female dominance. Because body mass differences did not explain the findings, various other possible explanations are discussed. It is suggested that food may not be the driving factor of female dominance in mouse lemurs. Instead, it is hypothesized that species‐specific differences in the quality of sleeping sites (i.e., tree holes) and in social grouping patterns may better explain why some mouse lemur species have female dominance, whereas others like the golden‐brown mouse lemur do not. It is concluded thatthese arguments and hypotheses may even hold true for other solitary foragers and may thereby lead to a better understanding of the variable social evolution in lemurs and primates in general. Am J Phys Anthropol, 2013. © 2012 Wiley Periodicals, Inc.     

Different competitive potential in two coexisting mouse lemur species in northwestern Madagascar

Interspecific competition has been suggested to influence the biogeographic distribution patterns of species. A high competitive potential could entail species-specific advantages during resource acquisition that could translate into a higher potential for range expansion. We investigated whether differences in the competitive potential of the morphologically similar and partially sympatric gray mouse lemur (Microcebus murinus) and golden-brown mouse lemur (Microcebus ravelobensis) may help to explain differences in their geographic range sizes. We carried out encounter experiments with 14 pairs of captured female mouse lemurs of both species. The experimental dyads were tested in a two-cage arrangement, with individuals being separated from each other outside the experiments. Two days of habituation and four subsequent days of 1-h encounter experiments were conducted, before releasing the animals again in the wild. In general, the M. murinus individuals won significantly more conflicts than their partners. In eight of 14 tested pairs, there was a significant species bias in winning conflicts, and in 87.5% of these dyads, M. murinus was the "dyad winner". A high competitive potential did not depend on body mass. Furthermore, "dyad winners" spent more time feeding (P < 0.05) and were less spatially restricted than "dyad losers". To conclude, our results suggest that the widely distributed M. murinus may indeed have a higher competitive potential than the regional endemic M. ravelobensis, which may, among other possible factors, have enabled this species to expand geographically, despite the presence of other competing congeners.     

Molecular phylogeny of the lemur family cheirogaleidae (primates) based on mitochondrial DNA sequences

Cheirogaleidae currently comprises five genera whose relationships remain contentious. The taxonomic status and phylogenetic position of both Mirza coquereli and Allocebus trichotis are still unclear. The taxonomic status of the recently discovered Microcebus ravelobensis (a sympatric sibling species of Microcebus murinus) and its phylogenetic position also require further examination. A approximately 2.4-kb mitochondrial DNA sequence including part of the COIII gene, complete ND3, ND4L, and ND4 genes, and 5 tRNAs was used to clarify relationships among cheirogaleids. Mirza and Microcebus form a clade representing the sister group of Allocebus, with a clade containing Cheirogaleus major and Cheirogaleus medius diverging first. M. ravelobensis and Microcebus rufus form a subclade within Microcebus, with M. murinus as its sister group. The molecular data support the generic status of Mirza coquereli and species-level divergence of M. ravelobensis. Furthermore, "M. rufus" may well represent more than one species.     

Sleeping site ecology in a rain-forest dwelling nocturnal lemur (Lepilemur mustelinus): implications for sociality and conservation

Suitable sleeping sites as potentially restricted resources are suggested to shape sociality in primates. We investigated sleeping site ecology of a rain-forest dwelling sportive lemur in eastern Madagascar for the first time. Using radiotelemetry, we characterized the type, quality and usage of sleeping sites as well as social sleeping habits of 11 focal individuals of the weasel sportive lemur (Lepilemur mustelinus) during the dry and the onset of the rainy season. Morphometric measurements provided additional information. The sexes showed an unusual sexual dimorphism for primates. Males and females did not differ in body length, but females surpassed males in body mass suggesting female dominance. Both sexes used dense vegetation and holes in hollow trees high above the ground as shelters for sleeping during the day. No sex difference in the quality of tree holes was found, but focal individuals used tree holes more often than open sleeping sites in dense vegetation. Both sexes showed high sleeping site fidelity limited to two to six different sites that they used primarily solitarily. The results imply that suitable sleeping sites are limited and survival of this species will strongly depend on the availability of mature rain forests with suitable hollow trees. Furthermore, these findings provide evidence of a solitary sleeping and ranging system in this rain-forest dwelling sportive lemur with suitable sleeping sites as defendable resources.     

Wild mouse lemurs revisit artificial feeding platforms: implications for field experiments on sensory and cognitive abilities in small primates

Dealing effectively with space to find important resources in a natural environment is a fundamental ability necessary for survival. Evidence has already been provided that wild gray mouse lemurs revisit stationary feeding sites regularly. In this study, we explore to what extent two sympatric mouse lemur species, Microcebus murinus and M. ravelobensis, revisited artificial feeding sites during a period of food scarcity. As the tested populations are marked with individual transponders, we built up artificial feeding platforms equipped with a transponder reader at nine different locations where mouse lemurs had been previously caught. We baited them with a liquid reward and recorded the visitors' ID, the time and frequency of their visits, as well as all encounters that occurred on the platforms. Only mouse lemurs visited platforms and a total of sixteen individuals across both species were identified. Mouse lemurs visited a platform with a frequency of 2.02 (+/-0.95, range: 1-3.4) times in a night and they revisited it on several consecutive nights following their first visit (percentage of revisits 90.6%+/-11.7, range: 73.3-100%). First visits on a platform occurred on average 44 min (+/-35; range: 13-131) after sunset. We identified encounters between mouse lemurs on platforms: all of them were agonistic and within a species. Within a dyad, chasers were significantly heavier than chasees (N=7 dyads). Our design of platform experiments offers the advantage of observing wild individually known small primates in their natural environment and of setting up controlled experiments to gain insight into their sensory and cognitive abilities.     

Sleeping and Ranging Behavior of the Sambirano Mouse Lemur, <Emphasis Type="Italic">Microcebus sambiranensis</Emphasis>

Primates require secure sleeping sites for periods of rest, but despite their importance, the characteristics of desired sleeping sites are poorly known. Here we investigated the sleeping ecology of a radio-collared population of the Sambirano mouse lemur, Microcebus sambiranensis, during the nonreproductive season in the Anabohazo forest, northwestern Madagascar. We also investigated their ranging behavior and examined the spatial distribution of sleeping sites within the home ranges of the collared individuals. We took measurements of the sleeping tree’s physical characteristics and recorded the number of collared individuals using each sleeping site. We found that M. sambiranensis generally use foliage sleeping sites more frequently than tree holes and individuals slept more frequently in densely foliated trees than in sparsely foliated trees, often alone. We observed no significant differences in home range size or nightly travel distance between males and females; however, home ranges were smaller than those described for other mouse lemur species. Finally, we found that M. sambiranensis sleep peripherally and forage centrally within their home ranges, a behavior not previously described for mouse lemurs. Our results indicate profound differences in the social organization between M. sambiranensis and other mouse lemur species described in the literature, suggesting species-specificity in mouse lemur ecology. Understanding the sleeping ecology and ranging behavior of mouse lemurs is of great importance to their conservation, as these data facilitate the planning of long-term reforestation, habitat management, and population assessment.     

Sociality in the gray mouse lemur (Microcebus murinus) in northwestern Madagascar

The mating system and social organization of the gray mouse lemur (Microcebus murinus) was investigated in two three-month field studies (covering a period before, during, and after the first mating season) in Ampijoroa, northwestern Madagascar. The spatial and temporal distribution of the sexes within a population was studied using mark/recapture techniques and radiotelemetry to assess possible contest or scramble competition between the males. Sociality was inferred from the occurrence and probability of nocturnal social encounters, the temporal stability of daily sleeping groups, and nocturnal ranging patterns of co-sleepers. Males and females were evenly distributed in the study area within a network of highly overlapping home ranges. No indications were found for the spatial monopolization of the females by certain dominant males. Males and females had spatial access to several potential mates; the mating system is therefore characterized as a multi-male/multi-female system. Male home range sizes increased during the first mating season, which was interpreted as an indicator for scramble competition between the males. Competitive mate searching, sperm competition, and temporary mate guarding as well as female mate choice are suggested as the most probable reproductive strategies. Over the course of the study the animals lived continually within the study area, and most females formed stable individualized sleeping associations. Females that slept together shared a higher percentage of their home range than did females that slept at different sites. It is suggested that this network of social relationships should be described as a dispersed but individualized neighborhood.     

Mutual mate choice in a female-dominant and sexually monomorphic primate

Sexual dimorphism is common in polygynous species, where intrasexual competition is often thought to drive the evolution of large male body size, and in turn, male behavioral dominance over females. In Madagascar, the entire lemur radiation, which embraces diverse mating systems, lacks sexual dimorphism and exhibits frequent female dominance over males. The evolution of such morphological and behavioral peculiarities, often referred to as "the lemur syndrome," has proven difficult to understand. Among other hypotheses, a potential role of intersexual selection has been repeatedly proposed but hardly ever tested. Here, we investigate whether female choice favors small and compliant males, and whether male choice favors large females in captive gray mouse lemurs (Microcebus murinus). Detailed analysis of a combination of behavioral observations and hormonal data available for both sexes shows that (1) females accept more matings from males with higher fighting abilities, (2) males adjust their investment in intrasexual competition to female fertility, and (3) both male and female strategies are weakly influenced by the body mass of potential partners, in directions contradicting our predictions. These results do not suggest a prominent role of intersexual selection in the evolution and maintenance of the lemur syndrome but rather point to alternative mechanisms relating to male-male competition, specifically highlighting an absence of relationship between male body mass and fighting ability. Finally, our findings add to the growing body of evidence suggesting flexible sex roles, by showing the expression of mutual mate choice in a female-dominant, sexually monomorphic and promiscuous primate.     

Parasite burden and constitution of major histocompatibility complex in the Malagasy mouse lemur, Microcebus murinus

We investigated the importance of the major histocompatibility complex (MHC) constitution on the parasite burden of free-ranging mouse lemurs (Microcebus murinus) in four littoral forest fragments in southeastern Madagascar. Fourteen different MHC class II DRB-exon 2 alleles were found in 228 individuals with high levels of sequence divergence between alleles. More nonsynonymous than synonymous substitutions in the functional important antigen recognition and binding sites indicated selection processes maintaining MHC polymorphism. Animals from the four forest fragments differed in their infection status (being infected or not), in the number of different nematode morphotypes per individual (NNI) as well as in the fecal egg counts (FEC) values. Heterozygosity in general was uncorrelated with any of these measures of infection. However, a positive relationship was found between specific alleles and parasite load. Whereas the common allele Mimu-DRB*1 was more frequently found in infected individuals and in individuals with high NNI and FEC values (high parasite load), the rare alleles Mimu-DRB*6 and 10 were more prevalent in uninfected individuals and in individuals with low NNI and FEC values (low parasite load). These three alleles associated with parasite load had unique amino acid motifs in the antigen binding sites. This distinguished them from the remaining 11 Mimu-DRB alleles. Our results support the hypothesis that MHC polymorphism in M. murinus is maintained through pathogen-driven selection acting by frequency-dependent selection. This is the first study of the association of MHC variation and parasite burden in a free-ranging primate.     

Antipredation Sleeping Behavior of Skywalker Hoolock Gibbons (<Emphasis Type="Italic">Hoolock tianxing</Emphasis>) in Mt. Gaoligong,Yunnan, China

Studying sleeping behavior can provide key information for understanding the ecology of a species. Antipredation is an important factor that affects primate sleeping behavior. We studied antipredation sleeping behavior in skywalker hoolock gibbons (Hoolock tianxing). We studied one group (NA) and a solitary female (NB) at Nankang from July 2010 to September 2011, and another group (BB) at Banchang from May 2013 to December 2014 in Mt. Gaoligong, Yunnan, China. Over the study period, we recorded 67 sleeping trees for members of group NA over 92 days, 17 trees for the solitary female NB over 22 days, and 159 trees for members of group BB over 186 days. Skywalker hoolock gibbons at both sites rarely used the same tree on consecutive days (N = 3 at both sites). They traveled fast to enter sleeping tree a mean of 160 ± SD 43 min before sunset at Nankang, and a mean of 192 ± SD 40 min before sunset at Banchang. They seldom (Nankang: 14%, N = 183 observations; Banchang: 25%, N = 548 observations) defecated in sleeping trees. They slept at sites with more tall and large trees and preferred to sleep on tall trees in the site. They slept on branches of small diameter and closer to tree tops. Our study suggests that antipredation plays an important role in skywalker hoolock gibbons’ sleeping tree selection and sleeping behavior. In addition, our data suggest potential effects of habitat degradation on gibbons’ sleeping behavior. Tall trees are especially important for gibbons in degraded forest and should be protected.     

Experimental evidence for olfactory predator recognition in wild mouse lemurs

Although primates have remarkable olfactory capabilities, their ability for olfactory predator recognition is still understudied. We investigated this cognitive ability in wild gray and golden-brown mouse lemurs (Microcebus murinus and M. ravelobensis) that were confronted with four different olfactory stimuli, derived from two Malagasy predators (fossa and barn owl) and two local nonpredator species (brown lemur and sifaka). The predator response was tested (1) in a systematic cage setup and (2) in a two-way choice experiment with two Sherman traps on platforms in the forest (stimulus trap vs. nonstimulus trap). For part 1, the study animals were housed in cages during habituation and 5 days of experiments. One stimulus was tested per night and was presented underneath a drinking bottle. The changes in the time spent close to the stimulus and the drinking time at the bottle were used as indicators of predator recognition. A timidity score was established by classifying the strength of the antipredator response during the experiment. The study animals spent significantly less time drinking and less time in the stimulus area when confronted with fossa odor compared with the other stimuli. The timidity score was significantly higher during the fossa stimulus compared with the nonpredator and the control stimuli. The two-way choice experiments revealed a complete avoidance of the fossa odor, which was not found with the other stimuli. Thus, wild mouse lemurs showed clear signs of olfactory predator recognition in the case of the fossa in both experiments, but no signs of avoidance to the other presented stimuli. The lack of owl avoidance may be explained by less or no aversive metabolites in the owl stimulus or by lower significance for olfactory recognition of aerial predators. Furthermore, the results showed slight differences between the two mouse lemur species that may be linked to differences in their ecology.     

Use of sleeping trees by ursine colobus monkeys (Colobus vellerosus) demonstrates the importance of nearby food

Examination of the characteristics and locations of sleeping sites helps to document the social and ecological pressures acting on animals. We investigated sleeping tree choice for four groups of Colobus vellerosus, an arboreal folivore, on 298 nights at the Boabeng-Fiema Monkey Sanctuary, Ghana using five non-mutually exclusive hypotheses: predation avoidance, access to food, range and resource defense, thermoregulation, and a null hypothesis of random selection. C. vellerosus utilized 31 tree species as sleeping sites and the species used differed per group depending on their availability. Groups used multiple sleeping sites and minimized their travel costs by selecting trees near feeding areas. The percentage that a food species was fed upon annually was correlated with the use of that species as a sleeping tree. Ninety percent of the sleeping trees were in a phenophase with colobus food items. Entire groups slept in non-food trees on only one night. These data strongly support the access to food hypothesis. Range and resource defense was also important to sleeping site choice. Groups slept in exclusively used areas of their home range more often than expected, but when other groups were spotted on the edge of the core area, focal groups approached the intruders, behaved aggressively, and slept close to them, seemingly to prevent an incursion into their core range. However, by sleeping high in the canopy, in large, emergent trees with dense foliage, positioning themselves away from the main trunk on medium-sized branches, and by showing low rates of site reuse, C. vellerosus also appeared to be avoiding predation in their sleeping site choices. Groups left their sleep sites later after cooler nights but did not show behavioral thermoregulation, such as huddling. This study suggests that access to food, range and resource defense, and predation avoidance were more important considerations in sleeping site selection than thermoregulation for ursine colobus.     

Sleeping site preferences in tufted capuchin monkeys (Cebus apella nigritus)

The characteristics and availability of the sleeping sites used by a group of 27 tufted capuchin monkeys (Cebus apella nigritus) were studied during 17 months at the Iguazu National Park, Argentina. We tested different hypotheses regarding possible ultimate causes of sleeping-site selection. Most sleeping sites were located in areas of tall, mature forest. Of the 34 sleeping sites the monkeys used during 203 nights, five were more frequently used than the others (more than 20 times each, constituting 67% of the nights). Four species of tree (Peltophorum dubium, Parapiptadenia rigida, Copaifera langsdorfii and Cordia trichotoma) were the most frequently used. They constituted 82% of all the trees used, though they represent only 12% of the trees within the monkeys' home range which had a diameter at breast height (DBH) > 48.16 cm (1 SD below the mean DBH of sleeping trees). The sleeping trees share a set of characteristics not found in other trees: they are tall emergent (mean height +/- SD = 31.1+/-5.2 m) with large DBH (78.5+/-30.3 cm), they have large crown diameter (14+/-5.5 m), and they have many horizontal branches and forks. Adult females usually slept with their kin and infants, while peripheral adult males sometimes slept alone in nearby trees. We reject parasite avoidance as an adaptive explanation for the pattern of sleeping site use. Our results and those from other studies suggest that predation avoidance is a predominant factor driving sleeping site preferences. The patterns of aggregation at night and the preference for trees with low probability of shedding branches suggest that social preferences and safety from falling during windy nights may also affect sleeping tree selection. The importance of other factors, such as seeking comfort and maintaining group cohesion, was not supported by our results. Other capuchin populations show different sleeping habits which can be explained by differences in forest structure and by demographic differences.     

Insect secretions determine habitat use patterns by a female lesser mouse lemur (Microcebus murinus)

The lesser mouse lemur (Microcebus murinus) is one of six sympatric nocturnal primates found in the Kirindy forest, west-Madagascar. Each of these species is reported to consume a secretion produced during the austral winter by the Homopteran insect Flatidia coccinea. In July and August 1993 a study was conducted to determine the importance of this food resource in the ecology of female M. murinus. At this study site, animals were distributed only along the forest edge where insect secretions are significantly more abundant than in the forest interior. Abundances of arboreal and nocturnal flying insects do not differ between the forest edge and interior. Experimental resource removal from a 25 × 25 m plot in one female's home range caused a significant shift in the animals' pattern of habitat use while no change occurred in a control plot. Thus, at this study site and time of year, the ranging behavior of a female M. murinus was strongly influenced by the presence of Homopteran secretions. © 1995 Wiley-Liss, Inc.     

Sleeping Sites of <Emphasis Type="Italic">Rhinopithecus brelichi</Emphasis> at Yangaoping,Guizhou

Arboreal primates spend about half of their lives at sleeping sites; hence, selection of sleeping sites is crucial for individual survival, and data concerning them is important for conservation efforts. We collected data on sleeping sites for a group of the endangered snub-nosed monkey (Rhinopithecus brelichi) at Yangaoping (27°58′N, 108°45′E) from January 2006 to December 2007. All sleeping sites were located in the mid-slope and in the shadow of ridges facing the northeast and southeast. The monkeys remained quiet while entering and occupying sleeping sites, and slept in evergreen species during the cold season (December–March). Trees in sleeping sites were similar in height and girth at breast height to those elsewhere, but some trees in lower areas were larger. The monkeys usually slept in close proximity to the last feeding spot, and their daily activities usually occurred around the sleeping site. Areas adjacent to sleeping sites were used more intensively than those not adjacent. Monkeys left the sleeping sites later in the morning in the cold season. These behavioral responses suggested that predation risk, thermoregulation, and climate stresses are the main determining factors in the selection of sleeping sites for this temperate monkey.     

Female‐biased sleeping aggregations of Amegilla florea urens (Hymenoptera: Apidae)

Although male bees and wasps aggregate in specific sites overnight, few studies have addressed the behaviors of female hymenopterans during the night. It is generally understood that they spend the night in a burrow or nest structure. We found female‐biased sleeping aggregations of Amegilla florea urens in populations on Iriomote Island. The sex ratio and number of sleeping individuals in the sex‐mixed aggregations changed daily. This species used dead branches as its main sleeping places, and the maximum number of individuals observed per place was 15. Females arrived at the aggregation place later and left it earlier in the morning than did males. Our result suggests that females used the sleeping place regularly but avoided a long stay with males. The use of the same sleeping place by the two sexes may be due to a limited number of sites suitable for sleeping in the forest.     

Long-term patterns of sleeping site use in wild saddleback (Saguinus fuscicollis) and mustached tamarins (S. mystax): effects of foraging, thermoregulation, predation, and resource defense constraints

Sleeping sites are an important aspect of an animal's ecology given the length of time that they spend in them. The sleep ecology of wild saddleback and mustached tamarins is examined using a long-term data set covering three mixed-species troops and 1,300+ tamarin nights. Seasonal changes in photoperiod accounted for a significant amount of variation in sleeping site entry and exit times. Time of exit was more closely correlated with sunrise than time of entry was with sunset. Both species entered their sleeping sites when light levels were significantly higher than when they left them in the morning. Troops of both species used >80 individual sites, the majority being used once. Mustached tamarins never used the same site for more than two consecutive nights, but saddlebacks reused the same site for up to four consecutive nights. Mustached tamarins slept at significantly greater heights than saddleback tamarins. There were consistent interspecific differences in the types of sites used. Neither the presence of infants, season, nor rainfall affected the types or heights of sites chosen. Sleeping sites were located in the central area of exclusive use more often than expected, and their position with respect to fruiting trees indicated a strategy closer to that of a multiple central place forager than a central place forager. These findings are discussed in light of species ecology, with particular reference to predation risk, which is indicated as the major factor influencing the pattern of sleeping site use in these species.     

Pair-specific usage of sleeping sites and their implications for social organization in a nocturnal Malagasy primate, the Milne Edwards' sportive lemur (Lepilemur edwardsi)

Safe sleeping sites may be a limited resource crucial for survival. In order to investigate their potential significance for social organization in nocturnal primates, we analyzed the spatial distribution of daily sleeping sites, their characteristics, their usage, and sleeping group compositions in the nocturnal Milne Edwards' sportive lemur during a 6-month field study in the dry deciduous forest of northwestern Madagascar. Sexes did not differ either in body size or in body mass. Sleeping sites were used almost exclusively by adult male-female pairs. Individuals showed a high sleeping-site fidelity limited to 2-3 different sleeping sites in close vicinity during the whole study period. Most females showed a higher fidelity to one distinct sleeping site than their male partners. Sleeping groups consisted of one adult male and one adult female and remained stable in composition over the whole study period. Exclusive pair-specific usage of sleeping sites suggests sleeping site related territoriality of male-female pairs, perhaps influenced by inter- and intrasexual resource competition. Results give first insights into the distribution patterns and social organization of this species. They imply dispersed monogamy for the Milne Edwards' sportive lemur, with sleeping sites as a potentially restricted and defendable resource.     

Social organization of Galagos in Kenyan coastal forests: I. Galago zanzibaricus

The social organization of Galago zanzibaricus was studied for the first time and the study included data from two different sites in the coastal forests of Kenya. A combination of mark-recapture and radio-tracking techniques was used to investigate patterns of inter- and intrasexual home range overlap. Associations in sleeping groups indicated social ties between individuals. Patterns of range use were established by radio-tracking focal individuals. Adult males generally had nonoverlapping ranges, shared with one or two females and their offspring with which the male regularly slept. Young females remained longer in their natal ranges than males and reproduced within their natal ranges. Range size and distance traveled per night were similar between the sexes; both sexes probably defended territories. None of the other galago (bushbaby) species studied to date show the degree of close male-female association found in G. zanzibaricus. This study thus extends the variety of social organization documented in nocturnal prosimians.     

A preliminary study of spatial distribution and mating system of pygmy mouse lemurs (Microcebus cf. myoxinus)

According to current hypotheses on the evolution of life history traits and social systems of Malagasy lemurs, nocturnality is associated with a solitary lifestyle and a polygynous or promiscuous mating system. Recent studies, however, have indicated that this may not be true of all lemurs. The goal of this study was to investigate the sociality and the mating system of pygmy mouse lemurs (Microcebus cf myoxinus), which are the smallest known primates, and which retain characteristics of the most primitive primates. I compared my findings with data on the sympatric Microcebus murinus and Cheirogaleus medius. Observational, morphometric and spatial distribution data were obtained by a radiotracking study in 1994, and from a capture-recapture study conducted during 1995/96. Pygmy mouse lemurs usually slept alone in a tangle of vegetation. During the mating season, sleeping sites of males were distributed over a much broader area than were female sites, indicating that male home ranges are larger than those of females. The home ranges of males overlapped during the mating season, and males occasionally roamed over long distances during a single night. Pygmy mouse lemurs forage primarily alone. Analysis of estrus stages indicate that female cycles are unsynchronized during the mating season. There was a lack of sexual dimorphism in body size but not in body mass. Males were heavier than females during the reproductive season but lighter than females the rest of the year. Testes of males varied in size seasonally and enlarged significantly during the mating season. The presence of a vaginal sperm plug in a female indicated the importance of preventing additional matings in this species. Thus pygmy mouse lemurs follow the predictions derived from sexual selection theory for multi-male mating systems with promiscuous matings and male sperm competition.