Communal Nesting Research Articles

Father nose best

Olfaction is the main sensory modality for many animals, but the importance of smell to humans is not so clear. However, a number of researchers have demonstrated that the human sense of smell, similar to that of many animals, might form part of the individual recognition and mate choice processes, albeit at a subconscious level. The mechanism by which the distinct odour of an individual arises is due in part to the highly polymorphic human leukocyte antigen (HLA) loci. The HLA are the human equivalent of the major histocompatibility complex (MHC), which influence a number of olfactory-related behaviours in rodents, including nesting, pregnancy block, individual recognition and mate choice.It is generally thought that most animals, including humans, base much of their odour preference on their own odour and those odours to which they were exposed as infants. However, there is some evidence for a heritable component to odour preference, although a genetic effect is difficult to prove owing to the many environmental variables that not only influence the preference, but also the odour production. In addition, the high level of variation at the HLA loci in the general population also adds complications to a genetic analysis in humans. However, a recent study [1xPaternally inherited HLA alleles are associated with women's choice of male odor. Jacob, S et al. Nat. Genet. 2002; 30: 175–179Crossref | PubMed | Scopus (273)See all References][1] demonstrates that there is indeed a genetic influence on odour preference in humans and, by using members of an isolated community of German–Austrian descent, the researchers were able to investigate how this choice varied with a limited number of HLA alleles.Females were asked to report on the ‘familiarity’, ‘intensity’, ‘pleasantness’ and ‘spiciness’ of the odours from males from a wide-range of ethnic backgrounds. What was evident was that the women preferred the odours of those males whose HLA most closely matched their own (although they did not perceive these as familiar). However, in a subtle twist, the preference was not just for similar HLA to their own, but for odours that came from individuals with similar HLA alleles to those that the women had inherited from their fathers; that is, a paternal effect. Additionally, the authors show that this effect has a genetic basis, as the preference co-varies only with those HLA alleles the women inherited from their father, rather than all the HLA alleles their fathers possess.This indicates a genetic parent-of-origin effect (POE) on odour preference, a phenomenon that can most readily be explained by genomic imprinting. Interestingly a study using mice [2xUrinary odour preferences in mice. Isles, A.R et al. Nature. 2001; 409: 783–784Crossref | PubMedSee all References][2] produced results that are strikingly similar to those of Jacob et al. In this investigation both male and female mice were shown to prefer paternal odour cues and this preference was also subject to a genetic POE. Although it is difficult to determine a mode of action for these POEs, what is germane is that this phenomenon could be an underlying mechanism behind kin-biased behaviour, such as mate choice, communal nesting and social behaviour in species as diverse as mouse and man.

Maximizing survivorship in cold: thermogenic profiles of non-hibernating mammals

Winter-active small mammals residing in seasonal environments employ many different behavioral, anatomical and physiological mechanisms to cope with cold. Herein we review research on survival mechanisms in cold employed by small mammals with emphasis on the families Soricidae, Muridae and Sciuridae. The focus of this review is on research delineating the role of seasonal changes in resting metabolic rate (RMR), nonshivering thermogenesis (NST), body mass, and communal nesting in enhancing winter survivorship of six species of small mammals (masked shrewSorex cinereus, short-tailed shrewBlarina brevicauda, southern red-backed voleClethrionomys gapperi, white-footed mousePeromyscus leucopus, deer mouseP. maniculatus, and southern flying squirrelGlaucomys volans) residing in the Appalachian Mountains of Pennsylvania, USA. Each species shows good over-winter survivorship but exhibits a different suite of mechanisms to maximize survival in cold.B. brevicauda, S. cinereus, andG. volans show slight increases in RMR during winter, whereasPeromyscus andC. gapperi exhibit decreased RMR overwinter. All six species experience elevated NST in winter. The comparatively low RMR and NST ofG. volans during winter was attributable to a decreased energy expenditure due to a larger body mass, coupled with communal nesting in cavities of trees that provided insulation from low ambient temperatures. Squirrels nesting singly experienced a longer period of elevated NST in winter and higher mean NST year-round than did squirrels nesting communally. Energy conservation in the form of growth retardation in winter was exhibited byC. gapperi andS. cinereus but not the other species.

Can information sharing explain recruitment to food from communal roosts?

The debate over whether communal nests and roosts function primarily as information centers (they facilitate the sharing of foraging information) remains unresolved. Here I use evolutionary game theory to investigate the relative importance of this influential hypothesis and an alternative: that roosts, in particular, function as recruitment centers (they facilitate aggregation at food patches). Basing my model on juvenile common raven (Corvus corax) behavior, I assume there is no net cost to being at food patches in groups, and foragers roost communally. Moreover, one strategic outcome is the observed raven behavior: individuals search independently and recruit from the roost once a patch is found (they play Search-and-Recruit, or SR). I investigate the stability of this in two scenarios that differ in the magnitude of the lost opportunity costs to mutants playing SR in populations of other strategies. When these costs only involve a chance of not being in a group at a located carcass, SR is the only evolutionarily stable strategy under all conditions. However, when these costs also include missing opportunities to be socially dominant, SR no longer enjoys exclusive dominance in the strategy set. Nevertheless, in both cases, there are conditions where group foraging benefits have no effect on the evolutionary stability of SR. Thus, contrary to assertions in the literature, the opportunity to share foraging information can be sufficient to drive the evolution and maintenance of recruitment to food from communal roosts. However, I conclude that both information and grouping benefits are likely to underlie communal roosting behavior in my focal system. Copyright 2002.

LACK OF TASK DIFFERENTIATION DURING PREY CAPTURE IN THE GROUP LIVING SPIDER STEGODYPHUS MIMOSARUM (ARANEAE, ERESIDAE)

Stegodyphus mimosarumof the African savanna form communal nests consisting of few to several hundred individuals and co-operate in nest construction and maintenance, brood care and prey capture. We tested large and small individuals for differential responses to different prey risk types. To date, there has been no conclusive evidence of tasking in these or other social spiders. If tasking occurs, small spiders should approach and attempt to subdue less dangerous prey items such as flies more often than the more dangerous prey items such as bees. Hungry individuals were significantly more willing to venture out of the nest refuge and thus accept the costs associated with prey capture than were satiated spiders. Apparent depletion of poison in previous prey captures did not significantly affect an individual's response to a prey item. Spiders treated more dangerous prey (bees) more carefully than less dangerous prey (flies), but there was no difference in the response of large versus small spiders to prey. The two- way interaction between spider size and prey type was never statistically significant, indicating a lack of tasking in this species.

Regular Spatial Patterns of Bank Swallow (Riparia riparia) Tunnel Entrances, with Some Possible Evolutionary Implications

Abstract Tunnel entrance distributions at six bank swallow sand-pit colonies showed consistently nonrandom, too-regular patterns, supporting the hypothesis that the distance between tunnel entrances is determined by territorial disputes at the tunnel mouths. Average nearest neighbor distances, and numbers of burrows per unit area of pit face, were both consistently greater than their random expectations, a paradox that is explained algebraically. Evidence of tunnel coalescence and communal nesting was found in a completely evacuated colony of 30 tunnels. It is argued that bank swallow colonial behaviors evolved to maximize populations on small exposed bank faces along streams and rivers, and that they are still behaving as if only small fractions of large sand pit banks are available. On small areas, regular spacings help to avoid too close tunneling and concomitant bank collapse. It is argued that a tolerance for communal nesting, once coalescence has occurred, involves less tunneling than the forced eva...

Parentage assignment and extra-group paternity in a cooperative breeder: the Seychelles warbler (Acrocephalus sechellensis).

We describe the development and initial application of a semiautomated parentage testing system in the Seychelles warbler (Acrocephalus sechellensis). This system used fluorescently labelled primers for 14 polymorphic microsatellite loci in two multiplex loading groups to genotype efficiently over 96% of the warbler population on Cousin island. When used in conjunction with the program CERVUS, this system provided sufficient power to assign maternity and paternity within the Seychelles warbler, despite the complications associated with its cooperative breeding system and a relatively low level of genetic variation. Parentage analyses showed that subordinate 'helper' females as well as the dominant 'primary' females laid eggs in communal nests, indicating that the Seychelles warbler has an intermediate level of female reproductive skew, in between the alternative extremes of helper-at-the-nest and joint nesting systems. Forty-four per cent of helpers bred successfully, accounting for 15% of all offspring. Forty per cent of young resulted from extra-group paternity.

Inbreeding in nature: brothers and sisters, do not unite!

Inbreeding, or mating among related individuals, causes problems with viability and fertility in small captive populations. Young inbred ungulates often die in zoos, and the eggs of inbred fruit flies frequently fail to hatch in the laboratory. But what is the role of inbreeding in nature? Does it really affect patterns of population change in the wild, and could it even cause extinctions? These questions were the subject of hot debate in the 1970s. By the late 1980s, many ecologists seemed to agree that other ecological factors were more important than inbreeding in reducing population size and in extinguishing populations. However, we could now be witnessing the revival of interest in inbreeding as a factor to contend with. Whereas theoretical studies have demonstrated how the accumulation of mildly deleterious alleles can lower the fitness of small populations, experiments, both in the laboratory and in the wild, have demonstrated significant effects of inbreeding on the density of several animal and plant species.Observations in 1998 suggested that inbreeding increases the risk of population extinction in the butterfly Melitaea cinxia.1xInbreeding and extinction in a butterfly metapopulation. Saccheri, I et al. Nature. 1998; 392: 491–494Crossref | Scopus (1008)See all References1 Some of the same authors now report experimental evidence2xExperimental confirmation that inbreeding depression increases extinction risk in butterfly populations. Nieminen, M et al. Am. Nat. 2001; 157: 237–244Crossref | PubMed | Scopus (106)See all References2 that not only confirms the earlier results, but also demonstrates when and how inbreeding exerts its harmful effect. Working on small populations of Melitaea cinxia in the laboratory, Nieminen et al. found that inbreeding lowered the proportion of eggs hatched and decreased the survival of over-wintering larvae. The larvae of this butterfly spin communal winter nests, but inbreeding made them spin nests full of holes, which failed to protect them from the elements. And when Nieminen et al. introduced in- and outbred populations into the field, they found that inbred populations had a much higher risk of extinction than did outbred ones.This study suggests that inbreeding in Melitaea cinxia may reduce local survival to the point of local extinction. And as the species occurs as a set of classical metapopulations, where the extinction of small local populations is counterbalanced by the colonization of empty sites, an increased risk of local extinction might ultimately threaten the survival of the species at a landscape level.The work of Nieminen et al. is clearly a case study on a single species with many special features. In their study region, Melitaea cinxia typically occurs as very small local populations, where inbreeding between close relatives is more the rule than an exception. This should keep us from generalizing the current results too broadly. But by identifying inbreeding as a key agent in the dynamics of at least this species, Nieminen et al. do offer an eye opener. With more and more species being split into smaller and more fragmented populations, perhaps inbreeding might soon be a threat to the survival of many wild populations?

An experimental test of kin association in the house mouse

Studies of genetic markers have suggested that female house mice (Mus musculus domesticus) prefer spatial association and nest sharing with close kin. Further, observations of mothers in single and communal nests suggest a potential advantage of association with kin, namely, improved reproductive success through cooperative defense of young against infanticide. In semi-natural enclosures, we tested for spatial association of female mice in small groups of sisters versus small groups of virtually unrelated females. We also examined success in producing and weaning litters by sisters versus mothers that were not close kin. Sisters exhibited greater spatial association than expected, although some groups of nonsisters showed close associations as well. All 14 sisters in the enclosures produced and weaned young in communal nests. Among 15 mothers that did not have sisters available, 4 did not produce litters, 2 shared a nest, and only 3 weaned young. Although infanticide occurred for both kinds of mothers, it was significantly more common in the single nests of nonsister mothers than for sisters. Thus, sisters were more successful at weaning young, probably owing to advantages of communal nesting. These results suggest that close female kin may associate spatially, and that there are distinct reproductive advantages due to the presence of close kin. The society of house mice is generally described as male dominated, but association of female kin may constitute the basis of social grouping in house mice.

Timing of oviposition and reproductive skew in cobreeding female burying beetles (Nicrophorus vespilloides)

Burying beetles (genus Nicrophorus) are known for their elaborate parental care. Two or more conspecific females may reproduce on the same carcass, especially when the carcass is large. Here we present the results of experiments in which we observed patterns of larval hatching and parental care in unmanipulated cobreeders, manipulated hatching synchrony between cobreeders, and compared patterns of oviposition in cobreeding and single females. Our results show that in these cobreeding associations, one of the females may or may not monopolize the carcass during the period of larval hatching. We present evidence that in either case, infanticide based on temporal cues constitutes an important proximate mechanism underlying the observed reduction in average reproductive success in cobreeding females. Females with higher synchrony (i.e., greater overlap between their oviposition patterns) produce larger broods with lower reproductive skew. Cobreeding females oviposit later and less synchronously than single breeders. Such delayed oviposition may reduce the risk that a female’s larvae fall victim to cannibalistic acts committed by her cobreeder or maximize her own opportunity to selectively kill her cobreeder’s larvae. Key words: burying beetles, cannibalism, communal breeding, infanticide, kin recognition, Nicrophorus, parental care, reproductive competition, reproductive skew. [Behav Ecol 11:357–366 (2000)] R eproductive competition is ubiquitous among communally breeding animals. When several conspecific females share a breeding site, as is the case in some vertebrates (‘‘joint nesting’’ or ‘‘communal breeding’’) as well as in some primitively social or eusocial insects (polygyny), young in the communal nest may compete for food. In this situation, females may increase their individual reproductive success by destroying their cobreeders’ eggs or young while sparing their own. Such selective infanticide requires the perpetrator to discriminate between her own offspring and those of cobreeders. One simple mechanism that can enable such discrimination is a temporal switch (Elwood, 1994), sometimes referred to as a ‘‘change in parental state’’ (Rosenblatt and Siegel, 1983), which is possibly mediated by hormonal changes triggered by important reproductive events (‘‘state-dependent cues’’; Elwood, 1991). Selective infanticide may result if the individual shows infanticidal behavior toward young at a time at which it is likely to encounter unrelated offspring, and parental, non-infanticidal behavior at a time when it is likely to encounter its own (Elwood, 1994). Examples include many bird species with intraspecific brood parasitism or communal breeding, in which females remove eggs from the nest throughout the prelaying period (i.e., until they have laid their first egg) (e.g., Emlen and Wrege, 1986; Macedo and Bianchi, 1997; Moller, 1987; Mumme et al., 1983; Stouffer et al., 1987; Vehrencamp, 1977), and males of many mammalian species that exhibit infanticidal behavior toward the young of females with whom they have not mated or cohabited long enough for the young to be the males’ own offspring (see Hrdy and Hausfater, 1984,

Spawning Behaviors in the Bluehead Chub, Nocomis leptocephalus, River Chub, N. micropogon and Central Stoneroller, Campostoma anomalum

Spawning behaviors were filmed and observed in the nest-building minnows, the bluehead chub, Nocomis leptocephalus, and river chub, N. micropogon. Analysis of videotapes exposed previously unreported behaviors (e.g., female retroflexure) and a precise sequence of male-female interactions that coordinated a successful spawn. Reproductive behaviors were classified into six sequential categories (interim, approach, alignment, run, clasp, dissociation) to facilitate interspecific comparisons. The most conspicuous differences between species involved the intensity of the female's retroflexure and the male's spawning clasp (strong in N. leptocephalus vs. weak in N. micropogon) and reproductive behaviors of subordinate males. In N. leptocephalus, subordinate males spawned concurrently and independently of the resident male over a communal nest, whereas in N. micropogon a subordinate acted like a satellite male and stole spawns from the nest-building male. In addition, heterogeneric spawning clasps involving a male and female N. leptocephalus and a male central stoneroller, Campostoma anomalum, are newly described.

A novel association between a beetle and a snake: Parasitism of Elaphe obsoleta by Nicrophorus pustulatus

While studying the nesting ecology of black rat snakes (Elaphe obsoleta [Say]; Serpentes: Colubridae) in eastern Ontario, we discovered that their eggs regularly contained larvae of the burying beetle Nicrophorus pustulatus (Herschel) (Coleoptera: Silphidae). The beetle appears to be a parasitoid of the snakes, which may make this the first documented case in which a vertebrate is the host of a parasitoid. Up to 100% of snake eggs in a nest were destroyed by beetles, indicating that N. pustulatus may be a significant, and heretofore unrecognized source of egg mortality for oviparous snakes. Evidence suggests that the association between these two species is well established, and that the beetle may also attack other species of oviparous snakes. Identification of snake eggs as the substrate for reproduction by N. pustulatus solves the mystery of where this species breeds. Also, the large amount of available biomass in communal black rat snake nests may explain why N. pustulatus is so fecund relative to its congeners.

Cooperative Reproduction in Ituri Forest Hunter-Gatherers: Who Cares for Efe Infants?

Cooperative Reproduction in Ituri Forest Hunter-Gatherers: Who Cares for Efe Infants?

Mating in a communal bee, Andrena agilissima (Hymenoptera Andrenidae)

Males of the fossorial, communal bee Andrena agilissima (Scopoli 1770) typically search for mates at flowers from which females collect pollen (WESTRICH 1989). To investigate whether communal nesting also affords mating opportunities for adults freshly eclosed from brood cells, we collected and dissected females that were emerging for the first time in spring from their natal nests and examined the contents of their spermathecae. Circa 97% of females contained spermatozoa in their spermathecae, indicating a high frequency of preemergence intranidal mating. Bees also copulated above ground, both near nest entrances and at flowers. In the latter situation, pollen-collecting females were seen to copulate, suggesting that A. agilissima females mate repeatedly (polyandry) and are sexually receptive across adulthood. The schedules of emergence of males and females from natal nest entrances in spring overlapped to a large extent; the species was neither markedly protandrous nor protogynous on the island of Elba, Italy, in 1998. These emergence patterns are consistent with both pre-emergence intranidal mating and polyandry linked to female receptivity extended across adulthood. The sex ratio at emergence was female biased (numerical proportion of males, M/M + F = 0.38), consistent with the view that pre-emergence intranidal mating generates local mate competition amongst males, and that it is an important component of the mating biology of A. agilissima. The mating opportunities of sons within the nest may potentially provide a selective benefit to communal nesting by females.

Large trees, fertile islands, and birds in arid savanna

LargeAcacia eriolobatrees scattered through the sparse grassy vegetation of arid oligotrophic savanna are focal points for animal activity because they supply nest sites, shade and scarce food resources. Faeces, fallen nest material and carcass remains left below trees elevate levels of nutrients available to plants in the soil beneath large trees. Soil concentrations of N and K were two times greater, and P concentrations 2.055 times greater under canopies ofA. eriolobatrees than in surrounding grassy shrubland.Plant species with fleshy fruits (Boscia, Grewia, LyciumandSolanumspp.) occurred in 8% of treeless plots and beneath 17% ofA. eriolobasaplings, but their frequency increased to 90% beneath large trees. DeadA. eriolobatrees were replaced by matrix vegetation (54%) and large shrubs with fleshy fruits (28%) rather than by conspecifics (17%). The distribution of fleshy-fruited plants in the Kalahari is thus dynamic and tied to the distribution of large trees such asAcacia erioloba.The shade beneath the canopies of large spreading trees was used by birds (particularly Kori BustardsArdeotis kori) and mammals (mainly SpringbokAntidorcas marsupialis, GemsbokOryx gazella, Blue WildebeestConnochaetes taurinusand Bat-eared FoxOtocyon megalotis) as a resting place during the heat of the day. Large raptors (> -031.055 kg) and vultures (> -035 kg) seldom perched on saplings, and more frugivorous bird species and individuals were seen on mature than sapling or dead trees. Nests of raptors, and the large communal nests of Sociable WeaversPhiletarius sociuswere found mainly in large trees, and the nests of the Tree RatThallomys paedulcuswere found in cavities in the stems of large trees.

How many queens are there in mature colonies of the green ant, Oecophylla smaragdina (Fabricius)?

AbstractIn an ongoing study of the green ant, Oecophylla smaragdina (Fabricius), to control insect pests, we surveyed newly established ant colonies in a 3‐year‐old mango block in March 1997 at Howard Springs, Northern Territory. We also surveyed 12 established ant colonies from May to July 1997 in Darwin, and six of them were surveyed again in February 1998. the aims were to determine patterns of initial colonisation by dealate queens of O. smaragdina and to locate the queen ant nest in established colonies of the ant. the number of dealate queens in new communal nests varied from one to 15. In a total of 73 nests, 71% of nests contained more than one dealate queen and 12% of nests contained segments or corpses of dealate queens, which were either parasitised by a fungus or killed by predators. This confirms that pleometrosis during the initial establishment of a colony is very common in O. smaragdina, and suggests that natural enemies affect the success of initial colonisation. of 12 established green ant colonies, 10 colonies with two to six queens were all in one nest, and only two colonies had one queen. In those colonies with multiple queens, we found that each queen was almost equally attractive to the major workers. Contrary to previous reports, these data suggest that pleometrosis in O. smaragdina during the initial period of colony establishment can lead to polygyny in mature colonies. This is the first time that polygyny has been documented in mature colonies of O. smaragdina.

Context‐Dependent Behavior and the Benefits of Communal Nesting

We present a model for the behavior of communally nesting insects. Females may forage for food to provision offspring or may remain in the nest, with the option of eating and replacing nest mates' eggs. Orphaned brood are at risk of predation. The optimal behavior of solitary females is determined using stochastic dynamic programming; static and dynamic evolutionarily stable strategies (ESSs) are then calculated for colonies of various sizes. A solitary female should forage if her brood is smaller than a time-dependent threshold. Females in small colonies should forage. In colonies above some threshold size, the static ESS is for one female to forage and the rest to cheat. The dynamic ESS in large colonies is for no females to forage until some time close to the end of the foraging season and for all females to forage thereafter. Mixed dynamic ESSs, with some foragers and some cheats, may arise if individuals differ in their chances of surviving a foraging interval or if females with new offspring vary their guarding behavior, depending on the numbers of cheats and new cells in the nest. We discuss these predictions in the light of published observations and preliminary data on the halictine bee Lasioglossum (Chilalictus) hemichalceum.

COMMUNAL FORAGING BEHAVIOR AND RECRUITMENT COMMUNICATION IN Gloveria sp.

The caterpillars of Gloveria sp. mark trails with a pheromone they deposit by dragging the ventral surface of the tip of the abdomen along branch pathways as they move between their communal nest and distance feeding sites. The threshold sensitivity of the caterpillar for an extract prepared from the secretory site was approximately 0.5 × 10−3 caterpillar equivalents/cm of trail. Bioassays show that Gloveria follows neither authentic trails of Malacosoma americanum nor artificial trails prepared from 5β-cholestane-3-one, a chemical previously reported to elicit trail following from other social caterpillars. Although our observations show that fed caterpillars mark heavily as they return to their nest, we found no evidence that individual caterpillars are able to recruit hungry nestmates to new food finds. In this species, recruitment to food occurs only after many caterpillars have reinforced a trail to a newly discovered food source. In contrast, hungry caterpillars of the confamilial species M. americanum, tested under identical conditions, responded strongly to the postprandial trails of individual caterpillars and rapidly abandoned depleted sites in favor of new food finds. We postulate that the difference in the efficiency with which these two species recruit nestmates to food evolved in response to differences in the spatial distribution of their food supplies.

Anomalures (Rodentia, Anomaluridae) in Central Gabon: species composition, population densities and ecology

A population survey of anomalures in the Foret des Abeilles, Central Gabon, was undertaken by exploring hollow trees over 75 ha. Three species were identified: Anomalurus derbianus, A. pusillus, and Idiurus macrotis. Population estimates indicate that a total of about 500 anomalures could be present per km(2). The three species shelter in hollow trees during the day and have a strictly nocturnal activity. Den selection depends mainly on the size and configuration of the cavity; neither tree species nor tree diameter are important. Data on home ranges and nightly movements were obtained by the radio-tracking of two A. derbianus and one I. macrotis. In dens, A. derbianus (about 700 g body weight) were mostly found either alone or in pairs of one female and a young. During the nocturnal activity period, two to three individuals (always including a young) were seen together on several occasions. Communal nesting occurred in I. macrotis (about 30 g body weight) with groups ranging from two to 40 individuals. By contrast, they were always observed alone during the night activity period. Few feeding data were recorded: all involved the consumption of phloem sap after scratching the bark of a small number of tree species. Great quantities of leaves and insects (ants and termites) were found in a stomach of A. derbianus. Comparisons with results obtained from long term studies on gliders in Australasia highlight several convergence points between African flying squirrels and flying phalangers (Phalangeridae), in particular when comparing species with similar body weights. Our data confirm that anomalures occupy the niche of gliders on the African continent.

Context-Dependent Behavior and the Benefits of Communal Nesting

We present a model for the behavior of communally nesting insects. Females may forage for food to provision offspring or may remain in the nest, with the option of eating and replacing nest mates' eggs. Orphaned brood are at risk of predation. The optimal behavior of solitary females is determined using stochastic dynamic programming; static and dynamic evolutionarily stable strategies (ESSs) are then calculated for colonies of various sizes. A solitary female should forage if her brood is smaller than a time‐dependent threshold. Females in small colonies should forage. In colonies above some threshold size, the static ESS is for one female to forage and the rest to cheat. The dynamic ESS in large colonies is for no females to forage until some time close to the end of the foraging season and for all females to forage thereafter. Mixed dynamic ESSs, with some foragers and some cheats, may arise if individuals differ in their chances of surviving a foraging interval or if females with new offspring vary their guarding behavior, depending on the numbers of cheats and new cells in the nest. We discuss these predictions in the light of published observations and preliminary data on the halictine bee Lasioglossum (Chilalictus) hemichalceum.

Social structure of the mound-building mouse Mus spicilegus revealed by genetic analysis with microsatellites.

The Mound-building mouse Mus spicilegus possesses a unique behaviour amongst mice. It constructs large earthen mounds and associated nesting chambers which serve to store food for immature individuals during the winter nesting period. We have used genetic analysis of four autosomal and four X-linked microsatellite loci to determine relationships between individuals inhabiting 40 mounds in Bulgaria. We show that, in almost all cases, individuals in a mound are the product of multiple parentage. We estimate the minimum number of males and female parents contributing offspring to each mound and demonstrate that at least two male and two female parents contribute offspring to a minimum of seven mounds. Analyses of relatedness coefficients and allele sharing values demonstrate that parents of different sibships within mounds are more related than if they had been chosen at random from the population and suggest that it is the female parents that contribute this excess relatedness. These results suggest that the mechanism by which individuals congregate to build mounds is kin-based and that the evolution of mound building and communal nesting in M. spicilegus is due in part to kin selection. This study represents a novel approach to the study of mammalian behavioural ecology. We have used a genetic dataset to construct an outline of social structure in the absence of behavioural data. These inferences can now be used to direct further work on this species.