Promiscuous Mating System Research Articles

Thermal constraints and gender-related differences in the activity patterns of the monomorphic rodent Clyomys laticeps

Abstract The daily activity pattern of animals can be classified as diurnal, nocturnal, crepuscular, and cathemeral reflecting strategic decisions to maximize mating and foraging while reducing predation risks and thermal constraints. Among monomorphic mammals, competition for resources and gender-related differences in physiology and reproductive strategies may translate into different activity patterns of males and females. Therefore, to understand the daily activity pattern both aboveground and belowground of the semifossorial rodent Clyomys laticeps, we tested the following hypotheses: (1) males and females differ in their diel activity patterns; (2) males are active for longer periods than females due to a promiscuous mating system and female site fidelity; and (3) higher maximum temperatures restrain C. laticeps activity. The study was carried out in the Serra de Caldas Novas State Park (Goiás, Brazil) in the Cerrado biome. The activity of C. laticeps was recorded using the telemetry technique over 5 days and nights (twice in each season, rainy and dry, between 2019 and 2021). Clyomys laticeps activity was bimodal, with 2 peaks around dawn and dusk, resembling a crepuscular pattern. Temporal segregation in male and female activity patterns was restricted to the dry season, when female activity was more diurnal than males who were mainly nocturnal. Intersexual competition for resources or male-avoidance behavior by females during the dry food scarcity season could contribute to this pattern, although it may also be explained by gender-related differences in thermal tolerances. Overall, males were active for longer periods than females, probably as a strategy to increase mating opportunities among the former and site fidelity in the latter. Finally, temperature imposed major constraints on C. laticeps activities who preferred milder temperatures and avoided being active in temperatures above their thermoneutral zone.

Male consort behavior is driven by female mate choice and receptive synchrony in Tibetan macaques (Macaca thibetana)

In group-living animals, males’ fighting abilities were usually mediated via dominance rank to sort males into a queue to access fertile females, especially in non-human primates. However, the correlation between male reproductive success and consortship, an alternative high-ranking male reproductive strategy, varies across species, obscuring the adaptive significance of male consort behavior. The priority of access (PoA) model is commonly used to predict male mating/reproductive success based on male dominance rank and female reproductive synchrony. In this study, we aimed to assess the applicability of the PoA model in predicting the distribution of male mating success and consortship, while also identifying the main factors influencing these outcomes in a group of free-ranging Tibetan macaques (Macaca thibetana) at Huangshan, China. Our results showed that (1) the male mating was significantly skewed towards the highest-ranking males, deviating from the expectations set by the PoA model. This departure was attributed to both female mate choice and male consort behavior. Notably, the influence of male rank on mating success decreased as the number of receptive females increased. Additionally, female mate choice became less significant when consorted by males compared to situations when they were not consorted; (2) the observed consort behavior among males was lower than what the PoA model predicted for available receptive days, while high-ranking males exhibited a gradual increase in their consort behavior with the rising number of receptive females. Our results suggests that, in Tibetan macaques, male consort behavior imposed limitations on female mate choice, and mitigated the impact of male dominance rank on male mating success as the number of receptive females grew. We propose that male consort behavior could be driven by female counter-monopoly strategies, and the simultaneous occurrence of consort behavior and opportunistic mating may represent the most effective mating tactic in this promiscuous mating system.

Molecular sibship reconstruction reveals a promiscuous mating system in brood parasitic little bronze-cuckoos (Chalcites minutillus)

Abstract In theory, emancipation from parental care is expected to favor promiscuous mating systems. However, in avian brood parasites, monogamy is surprisingly widespread, and it has been proposed that this may be favored by factors such as low population density and territoriality. Correspondingly, our previous research revealed that brood parasitic Horsfield’s bronze-cuckoos (Chalcites basalis), which occur at low population densities and defend territories, are monogamous. Here, we contrast this study with the mating system of the congeneric little bronze-cuckoo (C. minutillus), an obligate brood parasite that exploits more concentrated hosts and is, therefore, likely to occur at higher population densities. We use single nucleotide polymorphisms to characterize the reproductive patterns of unsampled adults by inferring sibling relationships among 30 offspring. We show that (1) little bronze-cuckoos occurred at high densities, (2) polygamy was the most common mating pattern found in this study in both sexes, and (3) where multiple cuckoo eggs are laid in the same nest, they were unrelated. These results indicate that females do not defend exclusive territories, and males do not defend multiple females (polygyny). Instead, little bronze-cuckoos appear to have a non-territorial, promiscuous mating system. Our results are consistent with theoretical predictions that polygamy is more likely to evolve in species that are emancipated from parental care, where there are plenty of available mates, and where home ranges are not defended.

Is promiscuity the key? Multiple paternity in the garden dormouse (Eliomys quercinus)

Many mammals have a promiscuous mating system with multiple sired litters. Promiscuity can increase the genetic variability, reduce the risk of inbreeding, and increase the effective population size, and is therefore crucial for preventing genetic loss and maintaining adaptability. This is particularly true for small and threatened populations. The garden dormouse (Eliomys quercinus) is a threatened species, which exhibited a drastic decline over the last 20–30 years. The aim of this study was therefore to investigate the mating system of the garden dormouse in mountain forest habitat by parentage analyses using 5 polymorphic microsatellite markers combined with morphometric data and information about the nesting behavior. Genetic parentage analyses revealed that 64% (9 of 14) of the litters were sired by at least two males, suggesting that garden dormice have a promiscuous mating system. The genetic findings were further supported by indirect indicators of promiscuity, such as testes, that were nearly four times larger than predicted for a rodent of its body mass and only slight male biased sexual size dimorphism. The finding of a promiscuous mating system in garden dormice should be taken into account in future conservation efforts. Due to its habitat preferences and limited dispersal potential garden dormice are vulnerable to forest fragmentation. The connection of suitable habitats facilitates dispersal and promotes access to potential mating partners, which could be especially important for populations colonizing new habitats. Access to potential mates may also reduce inbreeding, loss of genetic variability which is crucial for populations viability and survival.

Male mating season range expansion results from an increase in scale of daily movements for a polygynous-promiscuous bird.

Males of species with promiscuous mating systems are commonly observed to use larger ranges during the mating season relative to non-mating seasons, which is often attributed to a change in movements related to reproductive activities. However, few studies link seasonal range sizes to variation in daily space use patterns to provide insight into the behavioral mechanisms underlying mating season range expansion. We studied 20 GPS-tagged male wild turkeys (Meleagris gallopavo), a large upland gamebird, during the mating and summer non-mating seasons to test the hypothesis that larger mating season ranges resulted from male wild turkeys expanding the scale of daily movement activities to locate and court females. We delineated mating and non-mating seasons based on intensity of gobbling, a vocalization tied to courtship behavior, recorded by autonomous recording units distributed across the study area. Mating season ranges were significantly larger than non-mating season ranges. Daily ranges were larger in the mating season, as were distances between roost sites used on consecutive nights. Variance in daily range size was greater in the mating season, but low temporal autocorrelation suggested considerable daily variability in both seasons. We found no evidence that male wild turkeys changed how they distributed daily movements within seasonal ranges, or differences in habitat use, suggesting larger mating season ranges result from male wild turkeys increasing the scale of their daily movements, rather than a systematic shift to a nomadic movement strategy. Likely, the distribution of females is more dynamic and ephemeral compared to other resources, prompting males to traverse larger daily ranges during the mating season to locate and court females. Our work illustrates the utility of using daily movement to understand the behavioral process underlying larger space use patterns.

Parentage of 920 gray‐sided voles (Myodes rufocanus) born in a 3‐ha outdoor enclosure between September 1992 and May 1994

AbstractThis dataset provides the estimated birth location, sex, assigned parents, and estimated birth and death dates of 920 gray‐sided voles (Myodes rufocanus) born in a 3‐ha outdoor enclosure in Sapporo, Japan between September 1992 and May 1994, as well as capture–recapture data for 30 trapping sessions. We introduced 22 males and 25 females from several natural populations into the enclosure in late September 1992. Individuals in the enclosure were captured using live traps every 2 weeks until late April 1994, except for periods with deep snow cover. The location, body weight, and reproductive status of each vole were monitored throughout the study period. Complementary trapping was performed within the home ranges of breeding females to mark juveniles as early as possible. Upon first capture, each individual was marked by toe clipping for subsequent identification, and the clipped toes were used as DNA samples. For each individual, candidate parents were selected based on female reproduction history and capture points. Parentage then was determined using genotypes at 3–5 microsatellite loci with the CERVUS program. The results show that individuals born in the enclosure (N = 920) were derived from 215 litters, among which multiple males sired 51 litters. We used this database to elucidate the promiscuous mating system and inbreeding‐avoidance mechanism of the gray‐sided vole and to develop a new method for estimating the frequency of multiple‐male mating. This dataset will contribute to future behavioral ecological research on this and other small mammal species. The complete data set for this abstract published in the Data Article section of the journal is available in electronic format in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2023-03.1/jalter-en.

Pre-but not post-meiotic senescence affects sperm quality and reproductive success in the North African houbara bustard

Age-dependent reduction in reproductive success can arise due to multiple factors including a deterioration of reproductive physiology. Senescing males have been shown to produce ejaculates with poor sperm quality, which impinges on male reproductive success. In addition to individual age, gamete age can also affect male reproductive success. Accordingly, variance in male reproductive success can be due to pre-meiotic (referring to individual age) and post-meiotic senescence (sperm age). Here, we tested whether male senescence and sperm cell aging have additive or interactive effects on male reproductive success in a bird with a promiscuous mating system, the North African houbara bustard. To assess the effect of pre-meiotic aging, we compared male reproductive success between two age classes (3-6- and 12–16-year-old). To infer the effect of post-meiotic aging, male ejaculates were collected at three-time intervals following a common initial collection (day 1, 5, and 10). Therefore, day 1 ejaculates are supposed to contain younger sperm than day 5 and 10 ejaculates. Following controlled artificial inseminations, reproductive success was assessed using three fitness-linked traits (hatching success, chick growth rate and survival). In addition to reproductive output, we also assessed whether pre- and post-meiotic aging affected a wide range of sperm and ejaculate traits. In agreement with previous reports, we found that males in the older age class produced less sperm with poorer motility compared to young individuals. However, contrary to the prediction, we found that ejaculates collected at day 5 and 10 tended to have better sperm traits such as motility and velocity. The results on sperm traits were generally mirrored in the effect on reproductive success since young males produced offspring that grew faster and had better survival during the first month of life, and eggs fertilized by sperm collected at day 5 had the highest hatching success. In any of the models, there was evidence for interactive effects of male and sperm age. Overall, these results confirm the role of pre-meiotic aging on male reproductive success. The lack of evidence for sperm aging could come from the experimental design but might also reflect the pattern of mating frequency in a species with a lek-based mating system.

Female control of sperm ejection and retention in the cornsilk fly Euxesta eluta (Diptera: Ulidiidae).

Promiscuous mating systems provide the opportunity for females to bias fertilization toward particular males. However, distinguishing between male sperm competition and active female sperm choice is difficult for species with internal fertilization. Nevertheless, species that store and use sperm of different males in different storing structures and species where females are able to expel all or part of the ejaculates after copulation may be able to bias fertilization. We report a series of experiments aimed at providing evidence of female sperm choice in Euxesta eluta (Hendel), a species of ulidiid fly that expels and consumes ejaculates after copulation. We found no evidence of greater reproductive success for females mated singly, multiply with the same male, or mated multiply with different males. Female E. eluta possesses two spherical spermathecae and a bursa copulatrix for sperm storage, with a ventral receptacle. There was no significant difference in storing more sperm in spermathecae 24 h after copulation than immediately after copulation. Females mated with protein-fed males had greater reproductive success than similar females mated to protein-deprived males. Protein-fed females prevented to consume the ejaculate, retained more sperm when mated to protein-fed males than when mated to protein-deprived males. Our results suggest that female E. eluta can exert control of sperm retention of higher quality males through ejaculate ejection.

Recognition of visual kinship signals in chimpanzees (Pan troglodytes) by humans (Homo sapiens).

Associating with kin provides individual benefits but requires that these relationships be detectable. In humans, facial phenotype matching might help assess paternity; however, evidence for it is mixed. In chimpanzees, concealing visual cues of paternity may be beneficial due to their promiscuous mating system and the considerable risk of infanticide by males. On the other hand, detecting kin can also aid chimpanzees in avoiding inbreeding and in forming alliances that improve kin-mediated fitness. Although previous studies assessing relatedness based on facial resemblance in chimpanzees exist, they used images of captive populations in whom selection pressures and reproductive opportunities are controlled and only assessed maternity or paternity of adult offspring. In natural populations, the chances of infanticide are highest during early infancy, suggesting that young infants would benefit most from paternity concealment, whereas adults and subadults would benefit from the detection of all types of kin, including half-siblings. In our experiment, we conducted an online study with human participants, in which they had to assess the relatedness of chimpanzees based on facial similarity. To address previous methodological constraints, we used chimpanzee images across all ages, as well as maternal and paternal half-siblings. We found that kin status was detected above chance across all relatedness categories, with easier kin detection of father-offspring pairs, females, and older chimpanzees. Together, these findings support the existence of paternity confusion in infant chimpanzees and provide a possible mechanism for incest avoidance and kin-based social alliances in older individuals. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Strategic intergroup alliances increase access to a contested resource in male bottlenose dolphins

Efforts to understand human social evolution rely largely on comparisons with nonhuman primates. However, a population of bottlenose dolphins in Shark Bay, Western Australia, combines a chimpanzee-like fission-fusion grouping pattern, mating system, and life history with the only nonhuman example of strategic multilevel male alliances. Unrelated male dolphins form three alliance levels, or "orders", in competition over females: both within-group alliances (i.e., first- and second-order) and between-group alliances (third-order), based on cooperation between two or more second-order alliances against other groups. Both sexes navigate an open society with a continuous mosaic of overlapping home ranges. Here, we use comprehensive association and consortship data to examine fine-scale alliance relationships among 121 adult males. This analysis reveals the largest nonhuman alliance network known, with highly differentiated relationships among individuals. Each male is connected, directly or indirectly, to every other male, including direct connections with adult males outside of their three-level alliance network. We further show that the duration with which males consort females is dependent upon being well connected with third-order allies, independently of the effect of their second-order alliance connections, i.e., alliances between groups increase access to a contested resource, thereby increasing reproductive success. Models of human social evolution traditionally link intergroup alliances to other divergent human traits, such as pair bonds, but our study reveals that intergroup male alliances can arise directly from a chimpanzee-like, promiscuous mating system without one-male units, pair bonds, or male parental care.

Density‐dependent changes of mating system and family structure in Brandt's voles (Lasiopodomys brandtii)

AbstractA mating system is an important life history for animals dealing with changing environments. Population density affects the plasticity of a mating system and subsequently the family structure of animals, but its impacts on mating systems and social structures are rarely investigated by using molecular markers in field conditions. In this study, using microsatellite genetic markers, we examined the changes in the social and genetic mating system and family structure of Brandt's voles in the grassland of Inner Mongolia, China, under low‐, medium‐, and high‐density enclosures (each enclosure 0.48‐ha with 4 replicates.) We found, with the increase in population density of the founder voles introduced into the enclosure in early spring, both sexes increased their number of genetic mating partners, while males increased their social partners, resulting in a more promiscuous mating system. The number of genetic fathers and mothers per family, the number of social offspring per founder male or female, and the proportion of extra‐group offspring increased with increased density, indicating that the response of the family structure to density change, which is consistent with the change in mating system observed in our study. Both male and female voles had multiple mates, but males had a larger number of social and genetic mates, the number of social and genetic offspring, and the number of social and genetic families. Our study highlights the significance of density‐dependent plasticity of a mating system and family structure in affecting the population change of small mammals.

Integrating ecological and molecular data to investigate species maintenance and interspecific hybridization between the redbreast sunfish (Lepomis auritus) and the pumpkinseed sunfish (Lepomis gibbosus)

True sunfishes (genus Lepomis Rafinesque, 1819) of North America are renowned for hybridization, although hybrids often comprise only a fraction of the sunfish population in natural systems. Species boundaries may be maintained through premating mechanisms (e.g., ethological and habitat isolation), which may be facilitated by the promiscuous sunfish mating system; primarily, singular males guard nests that multiple females visit. Natural hybridization occurs between redbreast ( Lepomis auritus (Linnaeus, 1758)) and pumpkinseed ( Lepomis gibbosus (Linnaeus, 1758)) sunfishes, but there is no published research on its extent and causes. In this study, we assessed the relationship between ecological variables and the prevalence of hybridization in a sunfish population in a freshwater lake. Nests of both species were evaluated for differences in substrate, date, water depth, temperature, and dissolved oxygen. Sequencing of one fragment of nuclear DNA (calmodulin intron 4) and one fragment of mitochondrial DNA (12S) was employed on adult males and eight offspring from each nest to determine genetic identity and hybridization direction. Nonparametric tests found a significant difference in substrate between species’ nests ( p < 0.01), warranting further investigation into nest substrate as a mechanism for species maintenance. Furthermore, we observed asymmetrical hybridization with the less abundant species (redbreast sunfish) disproportionately affected.

The evolution of monogamy is associated with reversals from male to female bias in the survival cost of parasitism.

The extent to which parasites reduce host survival should depend upon how hosts balance trade-offs between reproduction and survival. For example, parasites are predicted to impose greater survival costs under polygynous or promiscuous mating systems in which competition for mates favours increased reproductive investment, particularly in males. We provide, to our knowledge, the first comparative test of the hypothesis that the mating system of the host is an important determinant of (i) the extent to which parasites reduce survival, and (ii) the extent to which males and females differ in the survival cost of parasitism. Using meta-analysis of 85 published estimates of the survival cost of parasitism from 72 studies of 64 species representing diverse animal lineages, we show that parasites impose a mean 3.5-fold increase in the odds of mortality on their hosts. Although this survival cost does not differ significantly across monogamous, polygynous and promiscuous mating systems, females incur a greater survival cost than males in monogamous species, whereas males incur a greater survival cost than females in polygynous and promiscuous species. Our results support the idea that mating systems shape the relative extent to which males and females invest in reproduction at the expense of defence against parasites.

Intraspecific variation in testis organisation and sperm head morphology of the delicate mouse (

The delicate mouse (Pseudomys delicatulus) ranges from Queensland to northern Western Australia. In this study the morphology of the cellular organisation of the testis and cauda epididymal spermatozoa are compared. Individuals from the mainland of the Northern Territory and Western Australia invariably have only 60–70% of the testes composed of seminiferous tubules with the interstitial tissue between the tubules containing abundant lipid rich Leydig cells, whereas the cauda epididymal sperm have highly polymorphic, often pear-shaped, heads and basally attached tails. In individuals from Queensland the seminiferous tubules make up approximately 80% of the testis, whereas in the cauda epididymides the sperm populations are generally less variable and have bilaterally flattened heads with the tail attached to the lower concave surface. These differences in the morphology of the delicate mouse testis and spermatozoa in these two geographic regions suggest differences in intensity of intermale sperm competition, with individuals from northern Western Australia and the mainland of the Northern Territory exhibiting monogamy whereas those from Queensland may exhibit some degree of intermale sperm competition and hence possibly have a polyandrous or promiscuous mating system. These findings support the suggestion that P. delicatulus, as currently recognised, contains at least one cryptic species.

Consistently high multiple paternity rates in five wild boar populations despite varying hunting pressures

Intraspecific variations in mating systems have been reported in numerous species, especially when they live in varying ecological contexts. This leads to variability between populations with regard to the proportion of females engaging in multiple male mating, which depends on the number of males available. For hunted ungulate species, hunting is known to influence population structure, especially when males are preferentially targeted for trophy hunting. Here, we investigated how variations in hunting pressure and the yearly proportion of heavy males removed have impacted multiple paternity rates in five wild boar (Sus scrofa scrofa) populations located in similar ecological contexts. We found high rates of multiple paternity in all studied populations, confirming the recently reported promiscuous mating system of wild boar. However, variations in hunting pressure and removal of heavy males did not significantly influence multiple paternity rates, contrary to our expectation. Nonetheless, a slight tendency for a decreasing multiple paternity rate with increasing hunting pressure and for increasing multiple paternity rate with increasing removal of heavy males from the population was detected. Based on these results, we discuss an alternative hypothesis on the ecological processes sustaining the influence of hunting regimes on the mating system. Overall, hunting pressure and management rules might be sufficient to disrupt the mating system in any of the populations, so it is important to continue the sampling of wild boar populations at the European scale, especially in populations with little hunting pressure.

Resource selection of a montane endemic: Sex-specific differences in white-bellied voles (Microtus longicaudus leucophaeus).

Resources that an individual selects contrasted against what is available can provide valuable information regarding species-specific behavior and ecological relationships. Small mammals represent excellent study organisms to assess such relationships. Isolated populations that exist on the edge of a species' distribution often exhibit behavioral adaptations to the extremes experienced by a species and can provide meaningful insight into the resource requirements of the species. We deployed radio transmitters in a peripheral population of the long-tailed vole (Microtus longicaudus) during the mating season. We developed models of resource selection at multiple scales (within home range and patch). We found voles generally selected areas close to water and roads and consisting of high understory vegetation primarily composed of grasses. Resource selection varied between sexes suggesting different resource needs during the breeding season. The differential resource needs of voles might be a result of the energetic requirements for reproduction and are representative of a promiscuous or polygynous mating system.

Ecology and social biology of the southern three-banded armadillo (Tolypeutes matacus; Cingulata: Chlamyphoridae)

Abstract Basic knowledge of species biology and ecology is essential for the assessment of species conservation status and planning for efficient conservation strategies; however, this information is not always readily available. Here we use movement behavior to understand the ecology and social biology of the poorly known southern three-banded armadillo (Tolypeutes matacus). We used VHF and GPS telemetry to monitor 26 individuals from two sites in the Pantanal wetlands of Brazil. We characterized armadillo activity patterns, evaluated the relationship between sex and body mass with home range size and mean daily distance traveled, and examined home and core range overlap. Three-banded armadillos were active on average for 5.5 ± 2.8 h/day, with most of their activity concentrated in the first half of the night. Adult males were heavier and had larger home ranges than adult females. Home range size scaled positively with body mass for males, but not for females. Core ranges for females overlapped little (< 1%) regardless of age, but home ranges for males overlapped both with other males (12%) and females (18%). Our data suggest that three-banded armadillos are mainly a nocturnal species. Home range and spacing patterns point to a generally asocial behavior and a polygynous or promiscuous mating system. We hope that the data generated as a result of this project will contribute to this species’ conservation in Brazil and elsewhere by guiding future management and research efforts.

Prolonged and variable copulation durations in a promiscuous insect species: No evidence of reproductive benefits for females

Within promiscuous mating systems, copulation often functions as more than a means of fertilization, and copulation durations can vary widely. Copulating for prolonged durations can enhance both female and male reproductive success, but can also result in costs: females of some insect species experience increased fecundity and fertility through male-provided nutrition during prolonged copulations, but also decreased longevity due to male-driven mechanisms. Here, for a common, promiscuous insect species (the squash bug, Anasa tristis), we first describe the range of copulation duration, which spans from 2 min to over 23 h. To investigate whether female A. tristis benefit from prolonged copulation, we next manipulated copulation duration and female diet, and we documented the resulting fecundity, fertility, and longevity of each female. We found no evidence that prolonged copulation durations affect female reproductive success. Females produced fertile eggs after a single 30 min copulation, and they subsequently produced fertile eggs for an additional 4 weeks. Our findings suggest that females do not benefit from prolonged copulations, that sperm transfer occurs very early during copulations, and that females can store sperm for long durations. Consequently, we suggest that female harassment avoidance and male mate-guarding may explain prolonged copulations in this species.

Mating system of Thrichomys fosteri in the Brazilian Pantanal: spatial patterns indicate promiscuity

Animal mating systems provide key insights into the relationship between evolutionary processes and ecological factors such as the spatio-temporal fluctuation of resource abundance. Characteristics of mating systems can be inferred from the spatial distribution of conspecifics and the arrangement of reproductive pairs. Here we used home-range size and overlap for Thrichomys fosteri in the Brazilian Pantanal to infer the mating system on this echimyid rodent. Our aims were to verify the existence of sexual dimorphism, to test whether home-range size varied with the sex and body weight of the individuals, to evaluate the degree of home-range overlap, to estimate mean population density, and to infer individuals’ mating system. Twenty one individuals (15 males and six females) were radio tracked from 14 to 349 days, with the number of locations by individuals ranging from 19 to 193 locations. There was a male-biased sexual dimorphism in body weight where males were 1.36 times heavier than females. Males’ home-range size increased with their body weight, while for females there was no relationship. There was extensive home-range overlap between both sexes, and no evidence of territoriality. Mean population density ranged from 0.9 to 3.03 individuals/ha. Our results indicate that multiple mates were available for both sexes, characterizing a promiscuous mating system.

Patterns of nest box sharing in woodland dormice (Graphiurus murinus): Evidence for intra-sexual tolerance and communal nesting

Nest sharing in rodents and other vertebrates is believed to be promoted by the gain of thermoregulatory advantages, reproductive imperatives or to be a by-product of other benefits to group living. Here, we studied the patterns of nest box sharing over a yearly cycle in a wild population of the arboreal, nocturnal and heterothermic woodland dormouse (Graphiurus murinus). We evaluated whether the timing of dormouse aggregations and group composition were compatible with thermoregulatory or reproductive imperatives. Nest box sharing between two or more dormice was observed throughout the year and was not correlated with monthly minimum temperatures. Therefore, the observed aggregations could not be exclusively related to the gain of a thermoregulatory advantage. All-male and all-female aggregations were more frequent during the mating season, following which some females seemed to engage in communal nesting and continued to share nests with some of their offspring well beyond the weaning period. Our data suggest that nest sharing was only partly affected by basic reproductive needs. We hypothesize that dormouse aggregations were ultimately favoured by a high level of intra-sexual tolerance elicited by the presence of numerous kin-related and familiar individuals in the population. This seems to stem from the high inter-individual spatial overlaps and the promiscuous mating system previously reported in this species. Further studies focusing on natural resting sites and genetic relatedness between individuals are needed to confirm our findings and test our hypothesis.