Mating System and Sleeping Behaviour of the Male and Female <Emphasis Type="Italic">Centris</Emphasis> (<Emphasis Type="Italic">Paracentris</Emphasis>) <Emphasis Type="Italic">burgdorfi</Emphasis> Friese (Apidae,Centridini)

We describe the mating behaviour of males of Centris (Paracentris) burgdorfi, a solitary, univoltine bee, with a wide distribution in Brazil. We also describe the unusual sleeping sites of males and females. The study was performed during two breeding seasons, in northeastern Brazil, where the species nests in aggregations in petrified dunes. Data on mating behaviour were collected through direct observations of the bees at the nesting-emergence site. Males compete intensely for virgin females in the morning, sometimes killing rivals. The high competition for females near the nesting site makes that the male has to take the female to another place to get genital contact. In the evening, males do not use plants to spend the night, instead they aggregate in sleeping clusters inside old burrows in the nesting-emergence area while females sleep in groups on plants that provide the floral oil used in nest construction.     

Nocturnal sleeping habits of the Yunnan snub‐nosed monkey in Xiangguqing,China

Weather, predation, and social organization are hypothesized to influence sleeping habits of nonhuman primates at night. To investigate how the Yunnan snub‐nosed monkey (Rhinopithecus bieti) prepares for and behaves during cold nights in their harsh alpine forest habitat (above 3,000 m), we studied the sleeping habits of the 171 one‐male units (OMU) in one group for 12 months at Xiangguqing in the Baimaxueshan Nature Reserve, China. It took 20.2 min from the time the study group entered a sleeping site until they fell asleep. This duration was consistent over seasons. On average, sleeping time was 11.5 hr per night over the year. Seasonal mean lengths of sleeping time varied significantly, however, and ranged from 10 to 13 hr per night, correlating with night length. Two sleeping styles were distinguishable: solitary sleeping and huddled sleeping. That adult males in OMUs principally slept alone. This is likely to reflect night‐time guarding behavior. Female–juvenile and female–infant dyadic huddles were the most prevalent sleeping unit (42% of all observed data), and the monkeys employed female‐biased huddling during nocturnal sleep. Huddled sleeping group size showed significant seasonal variation, with the largest huddle (eight individuals) occurring in winter. Climate and social organization profoundly influence the nocturnal sleeping habits of R. bieti, while huddling behavior may help shield animals from cold nights and provide additional protection against predators. Am. J. Primatol. 72:1092–1099, 2010. © 2010 Wiley‐Liss, Inc.     

Communal roosting and formation of sleeping clusters in barbary macaques (Macaca sylvanus)

Sleeping cluster composition and distribution were studied in a semi-free-ranging population of 174 Barbary macaques (Macaca sylvanus) in Rocamadour/France. Over a period of 2 months 341 sleeping clusters comprising 754 animals were recorded as animals left the sleeping trees. To control for nocturnal activities five observation periods were conducted, each of which covered a complete night. Sleeping partners were selected from a particular set of individuals. From night to night there was considerable fluctuation among the individuals, which finally formed a sleeping cluster. Preferred size of sleeping clusters was two and three individuals per cluster. The majority of females spent the nights in body contact to infants or female juveniles; whereas males either slept alone or with older male juveniles. Adult males and females never shared a sleeping cluster. During the night the animals showed hardly any locomotive and vocal activity. Sleeping clusters remained stable until dissociation the next morning. © 1992 Wiley-Liss, Inc.     

Communal Roost Site Selection in a Neotropical Harvestman: Habitat Limitation vs. Tradition

Many species have been reported to form roosting (resting, sleeping) aggregations at ‘traditional’ sites, but the alternative hypothesis that specific sites are used repeatedly because of habitat limitation is rarely tested. We studied the roosting behavior of a species of harvestman (Opiliones, Prionostemma sp.) at a lowland rainforest site in Nicaragua. Both sexes roosted by day in spiny palm trees, dispersed at dusk to forage, and rejoined aggregations just before dawn. The distribution of harvestmen among spiny palms was significantly clumped, and harvestman density did not correlate with spiny palm density. Aggregations formed repeatedly in a small subset of the available spiny palms and the same sites were used in two different years (2001, 2003). Nevertheless, the membership of aggregations was fluid; individual harvestmen were found at multiple roosts and moved up to 0.2 km per night. Translocated animals often returned to the roost where they had been released or nearby roosts but were never found at previously unused sites. The high consistency of site use but low site fidelity of individuals suggests that roost sites differed conspicuously (to the harvestmen) from sites that were not used. We found no univariate or multivariate differences between used and unused sites, however, in the characteristics of the trees or microclimate. These results conflict with the habitat limitation hypothesis but are consistent with the traditional site use hypothesis. The tradition may be mediated by a site‐labeling chemical, a mechanism that does not require individual site fidelity. We discuss these results in relation to the proposed functions of roosting aggregations.     

Huddling relationships in night sleeping groups among wild Japanese macaques in Kinkazan Island during winter

Huddling groups at sleeping sites, and allogrooming and proximity in the daytime during winter, were examined in a wild Japanese macaque (Macaca fuscata) troop on Kinkazan Island in the non-snowy district of northern Japan. All sleeping groups, defined as a cluster in which individuals huddle at sleeping sites, were formed on the ground. Their sizes tended to increase when the temperature was lower. The number of adults with mutual physical contact in sleeping groups increased when the size of sleeping groups increased. These results suggest that the physiological function of huddling is protection from low temperatures, and that macaques select the ground as sleeping sites to form large sized groups. Huddling was performed most frequently among kin dyads. Non-related dyads which appeared to be affiliative in the daytime also huddled frequently at sleeping sites. Even non-related dyads which showed affiliative behavior less frequently in the daytime exhibited huddling, at night, however, they did so less often than those of kin dyads and affiliated dyads. It appears that huddling at night by pairs that did not normally affiliate in the daytime was made possible by the increased tolerance of individuals responding to colder temperatures at night in winter. Furthermore, huddling, grooming, and proximity were exhibited at greater frequency between kin dyads, and between high-ranking males and specific females of kin groups, although the dyads of individuals older than 15 years often were involved only in huddling. These results suggest that two types of social bonds exist at sleeping sites in winter. One is the social bond common to both the daytime and nighttime, the other is peculiar to nighttime. Consequently, the social function of huddling is that, troop integration might increase at sleeping sites in winter as close social relationships among adults are extended more widely than those in daytime.     

Female clustering in cockroach aggregations—A case of social niche construction?

Individuals in groups can suffer costs through interactions with adversarial or unknown conspecifics. Social niche construction allows individuals to buffer such potential costs by only engaging in preferred associations. This may be particularly beneficial in insect aggregations, which are often large and highly fluid. However, little is known regarding the structuring of such aggregations. Here we use social network analyses to test for fine‐scale social structure in resting aggregations of the sub‐social cockroach Diploptera punctata and to explore the social pressures that contribute towards such structure. We showed that females were significantly more gregarious than males and formed the core of the proximity network, thus demonstrating a higher level of social integration. This fine‐scale structure is likely to result from females displacing males; females initiated most displacements whilst males received the majority. We explain this behaviour in terms of social niche construction by showing that females received significantly fewer approaches and investigations at more female‐biased local sex ratios. We therefore suggest that female social clustering occurs in this, and presumably other, species to reduce potential costs associated with male harassment. This demonstrates how social niche construction can lead to higher level social structure; we suggest this approach could be used across a range of species in order to improve our understanding of the evolution of sociality.     

Female odours promote the activation of sheltered kissing bug Rhodnius prolixus males and modulate their orientation

The existence of a pheromone emitted during copulation has been reported for Rhodnius prolixus (Hemiptera: Reduviidae) Stål. Adults possess one pair of metasternal glands (MGs) from which female R. prolixus release volatiles mainly at night. We investigated whether these volatiles emitted by adult R. prolixus can modulate sexual‐related behaviours of opposite and/or same sex individuals. We first used a shelter bioassay to test if adult activity patterns can be affected by chemical signals emitted by opposite sex conspecifics. We observed that males left the shelter more frequently in the presence of females, showing higher activity and an increase of intrasexual copulation attempts. Females showed no shelter‐related activation in the presence of male odours. Second, we used a locomotion compensator device to investigate whether females or males show oriented responses to odours emitted by adults. We found that males oriented towards air currents carrying female odours but females did not orient towards odours emitted by adults. Finally, we observed that males oriented towards the female MG compounds. Thus, a volatile chemical signal emitted by females from their MGs promoted the activation of sheltered males and modulated orientation to air currents.     

Strategies used by bonnet macaques (Macaca radiata) to reduce predation risk while sleeping

Sleep results in a decrease in alertness, which increases an animal’s vulnerability to predation. Therefore, choice of sleeping sites would be predicted to incorporate predator-avoidance strategies. The current study, conducted in two national parks in southern India, examined the behaviors adopted by bonnet macaques (Macaca radiata) to reduce the risk of being preyed upon while sleeping. Bonnet macaques from an urban setting with a low predatory risk were included for comparison. The physical characteristics of the sleeping sites in the forest corresponded with features that were most difficult for predators to access; bonnet macaques selected emergent trees with high boles near human settlements. These trees typically overhung water. Within the canopy, individuals slept in huddled subgroups near the terminal ends of branches, preferentially selecting branches over water. Subgroups were generally composed of members of the same age and sex, which likely promoted social bonding. Adult males and females with infants selected branches higher than members of other age and sex categories. The lateral distances of individuals along branches from the main trunk were similar across demographic categories. The size of a subgroup appeared to be limited by the weight a branch could support; lateral distances were maintained by regulation of mean subgroup weight, with heavier individuals forming smaller subgroups. The urban troop slept on the top of a building. Subgroup compositions at the urban site were similar to those at the forest sites. However, subgroup size, not restricted by branch fragility, resulted in larger subgroups than those found in the forest. Our results indicate that bonnet macaques adopted a suite of behaviors that reduced their risk of being preyed upon at night by selecting sleeping sites that minimized predator encounters and by selecting the safest locations within the canopy.     

Fine‐scale group structure and demography of African savanna elephants recolonizing lands outside protected areas

Aim Dispersal is a critical component of animal ecology that is poorly understood for most species. In particular, savanna elephants (Loxodonta africana) have been studied for decades in national parks across Africa, but little is known about their dispersal into new or unused habitats or their population dynamics in human‐dominated landscapes. We capitalized on a natural dispersal event of savanna elephants recolonizing communal land in southern Kenya to document their demographic characteristics and genetic relationships. Location Rift Valley province of Kenya. Methods We collected faecal samples and used genetic methods to identify individuals, estimate the sex ratio and evaluate the patterns of relatedness within the female groups and male aggregations. We also measured dung bolus circumference to assign age classes to individuals and estimate the age structure. Results We identified 112 individuals with a sex ratio not different from one (1.32:1.00). The age structure was skewed towards younger elephants (71%), suggesting the potential for rapid growth from reproduction. We detected significantly higher kinship levels within female groups (R = 0.124 ± 0.023), suggesting that family groups colonized the site, but found little support for higher‐order genetic relationships among female groups. Males detected together were unrelated (R = 0.003 ± 0.030). Main conclusions Our results suggest that highly social mammals, such as savanna elephants, disperse into unoccupied habitat as family groups and that a young demographic structure and a large number of males might be expected in establishing populations. These findings highlight the potential value of indirect, non‐invasive methods for assessing elephant herd and demographic characteristics when direct observations are difficult.     

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.     

Influences of parasites and thermoregulation on grouping tendencies in marine iguanas

I determined whether grouping behavior influences parasite loadand body temperature of Galápagos marine iguanas, reptilesthat rest gregariously. Mobile (or predatory) Ornithodoros ticks(4.7 mm average body length) approached at a ground speed of65 cm/min and parasitized sleeping marine iguanas for 3.7 hper night, drawing about 0.1 ml blood. Contagiously transmittedAmblyomma ticks hang on to iguana hosts for days or weeks. Marineiguanas sleeping alone had 2.0 mobile ticks per night, whileindividuals sleeping in groups had 0.1 to 1.1 mobile ticks pernight. Single iguanas decreased their mobile parasite load to0.2 ticks per night by sleeping on bushes. Experimental nightlytranslocation of iguanas to areas without other sleeping iguanassignificantly increased their mobile parasite burden above levelsencountered by naturally single individuals (n = 4.6 ticks pernight). Creating an experimental group of two animals reducedinfestation with mobile ticks by 59% compared to levels on singleanimals. Over the course of weeks, mobile ectoparasite loadsat grouping sites increased to levels found at single sites,at which point marine iguanas changed sleeping sites. Groupinghad no effect on the prevalence of contagious ticks. Furthermore,grouping did not help to conserve body temperature in Genovesaiguanas, as measured by radiotelemetry. I conclude that marineiguanas group during daytime at microhabitats favored for thermoregulation(predation is absent in this population). Thermoregulation wasnot of prime importance for nightly aggregations, which insteadserved to reduce mobile ectoparasite load. As a minimum costof infestation, I estimate that individuals sleeping alone wouldhave a 5.4% lower annual energy budget due to tissue removal,not including potential internal infections.     

Spider monkey sleeping sites: Use and availability

The behavior of spider monkeys (Ateles geoffroyi) at sleeping sites and the characteristics of these sites were studied in Santa Rosa National Park, Costa Rica. The spider monkeys tended to congregate just prior to dusk at a number of sleeping sites which were repeatedly used (81.6%), but occasionally they slept in trees which were only used once (18.4%). All of the regularly used sleeping trees were not used concurrently, but rather, there was a rotation between sites. In general, males were not encountered at regularly used sleeping sites as often as other age/sex classes, and when they were in all male subgroups, they did not sleep in repeatedly used sites. The trees used as regular sleeping sites tended to be large, but such trees were common in the group's home range. The size of the subgroups attending repeatedly used sleeping trees was large when food was abundant and small when food was scarce. It is suggested that this relationship reflects that the costs of travelling to the sleeping site would be more easily recovered when food was abundant than when food was scarce.     

Factors Affecting Sleep/vigilance Behaviour in Incubating Mallards

Vigilance is a behavioural tactic that allows individuals to control their surroundings and to assess predation risk. In contrast, sleep is unique behavioural state with widely hypothesized restorative and energy‐saving functions, but reducing attentiveness and increasing susceptibility to predation. Sleeping birds resolve this conflict by interrupting sleep with short periods of eye opening (termed ‘scans’) during vigilant sleep. Miscellaneous environmental factors and sleeping postures may affect the perception of risk and corresponding vigilance level. Here, we investigated the influence of nest vegetation concealment, time of day and sleeping postures on the sleep/vigilance trade‐off in incubating Mallards (Anas platyrhynchos). We found that incubating females increased their vigilance with increasing nest vegetation cover facing the vigilant eye during both the day and the night periods; however, mean nest vegetation concealment did not affect female vigilance. Females also reduced their total vigilance along with scan frequency during the night period, while displaying the opposite pattern during the daylight. The rest‐sleeping position was preferred more during the night compared with the daylight period, and females were more vigilant in this position at night. Our data show that the nest vegetation concealment regardless of visual abilities during different light conditions, time of day and sleeping posture play an underlying role in antipredator vigilance during sleep in this cryptic ground‐nesting bird.     

Population status,structure and activity patterns of the Bohor reedbuck Redunca redunca in the north of the Bale Mountains National Park,Ethiopia

The Bohor reedbucks Redunca redunca (Pallas, 1767) were studied in the Bale Mountains National Park (BMNP), Ethiopia to assess their population ecology and activity patterns. The total count method was used to assess population size. Activity patterns of a herd were studied with five minutes recording intervals. There were 406 Bohor reedbucks in the study area of which 96.8% (n = 393) was confined to the Gaysay‐Adelay area. The population was female‐biased. Excluding juveniles, 57.1% (n = 232) was females and 33.5% (n = 136) was males. More adults (71.7%, n = 291) were observed than sub‐adults (18.9%, n = 77) and juveniles (9.4%, n = 38). The herd size of Bohor reedbucks varied from 3 to 5. Herds were seen in aggregations of up to 59 individuals during the dry season in swamp grassland habitat. The maximum number observed in such aggregations during the wet season was 38. The diurnal activity pattern showed feeding peaks early in the morning and late in the afternoon, with resting during the mid‐day. Two feeding peaks were observed in the nocturnal activity phase: one during dusk and the other around midnight. In contradiction to the general concept of occurrence of smaller herds during the dry season, the Bohor reedbucks aggregate in swamps during the dry season. They were also active during night and day time.     

Body mass and sex‐biased parasitism in wood mice Apodemus sylvaticus

Male sex‐biased parasitism (SBP) occurs across a range of mammalian taxa and two contrasting sets of hypotheses have been suggested for its establishment. The first invokes body size per se and suggests that larger individuals are either a larger target for parasites, trade off growth at the expense of immunity or cope better with parasitism than smaller individuals. The second suggests a sex‐specific handicap whereby males have reduced immunocompetence compared to females due to the immunodepressive effects of testosterone. The current study investigated whether sex‐biased parasitism is driven by host ‘body size’ or ‘sex’ using a rodent–tick (Apodemus sylvaticus–Ixodes ricinus) system. Moreover, the presence or absence of large mammals at study sites were used to control the presence of immature ticks infesting wood mice, allowing the impacts of parasitism on host body mass and female reproduction to be assessed. As expected, male mice had greater tick loads than females and analyses suggested this sex‐bias was driven by body mass as opposed to sex. It is therefore likely that larger individuals are a larger target for parasites, trade off growth at the expense of immunity or adapt behavioural responses to parasitism based on their body size. Parasite load had no effect on host body mass or female reproductive output suggesting individuals may alter behaviour or life history strategies to compensate for costs incurred through parasitism. Overall, this study lends support to the ‘body size’ hypothesis for the formation of sex‐biased parasitism.     

Dynamics of Aggregation Formation in Japanese Beetles, <Emphasis Type="Italic">Popillia japonica</Emphasis>

For most insect aggregations to form, they need to be started by an initial individual (the pioneer) and joined by later individuals (the joiners). Pioneers and joiners may differ with regard to characteristics such as sex and body size. We carried out three field experiments to examine the characteristics of Japanese beetles, Popillia japonica, pioneering and joining aggregations on host plants. Individual beetles were captured as they arrived on uninhabited grape plants, as well as plants designed to simulate aggregations with model beetles and feeding damage. For all experiments and treatments, the beetles arriving were significantly female-biased. Females pioneering later in the day had higher egg loads than those arriving earlier, and the results of two experiments suggested that females arriving at existing aggregations tend to have lower egg loads than females pioneering elsewhere. Male beetles found on uninhabited plants were smaller and arrived earlier in the day than males in the aggregation area of the experiment. Overall, these results indicate that female Japanese beetles may be the initiators of aggregations (i.e. the pioneers) with males joining later in the process, and suggest that females with fewer eggs and males with larger body sizes are more likely to join aggregations. We use these patterns to hypothesize on the different functions of aggregations for male and female Japanese beetles.     

Distribution and spacing of Drosophila mycetophaga flies on bracket fungi used as mating arenas

Abstract.

• 1 To understand the nature of male aggregations in Drosophila mycetophaga, data were collected on male and female distribution and male spacing on bracket fungi used as mating arenas in cool rainforests of south-eastern Australia.
• 2 Both males and females appeared to be aggregated among bracket fungi that were used as mating arenas. Females were associated with large male aggregations. The probability of a fungus being occupied increased with its area. However, a multiple Poisson regression analysis suggested that fungus area did not affect female distribution when male number was controlled.
• 3 The presence of female breeding and feeding resources did not determine where aggregations were formed, because there were aggregations on fungi without resources, and fungi with resources were not used more often than those without them.
• 4 D.mycetophaga males did not select and defend territories within bracket fungi, and did not determine female access to areas. However, males were more evenly spaced than expected on the basis of a random distribution, suggesting that males kept apart from each other.
• 5 The distribution of the different sexes and male spacing pattern supports the interpretation that D.mycetophaga has a lek mating system.

     

Formation and maintenance of mating aggregations in a stink bug,Megacopta punctissimum (Montandon) (Heteroptera: Plataspidae)

Adults of a stink bug,Megacopta punctissimum, formed mating aggregations on their host plants: a few pairs in copula and a few bachelor males (males not in copula) stayed in the aggregation and the bachelor males waited for arriving females to mate with. The processes of formation and maintenance of the aggregations were observed using the individual marking technique. Aggregations initiated by 2 males or by 1 male and 1 female were usually joined by 1 or more individuals and lasted for several days, but aggregations initiated by 2 females broke up within 1 h. Aggregations were not maintained by the same members. The residence time (time from joining an aggregation to leaving the aggregation without copulating) of males was longer than that of females. There was a negative correlation between the residence time of males and the number of bachelor males in an aggregation when bugs joined it, while the residence time of females was positively correlated with the number of bachelor males in the aggregation. When bugs copulated after joining an aggregation, the postcopulatory residence time (time from completing copulation to leaving the aggregation) was longer in males than in females. Thus, males had a stronger tendency to initiate and maintain aggregations than females.     

Novel genetic sex markers reveal high frequency of sex reversal in wild populations of the agile frog (Rana dalmatina) associated with anthropogenic land use

Populations of ectothermic vertebrates are vulnerable to environmental pollution and climate change because certain chemicals and extreme temperatures can cause sex reversal during early ontogeny (i.e. genetically female individuals develop male phenotype or vice versa), which may distort population sex ratios. However, we have troublingly little information on sex reversals in natural populations, due to unavailability of genetic sex markers. Here, we developed a genetic sexing method based on sex‐linked single nucleotide polymorphism loci to study the prevalence and fitness consequences of sex reversal in agile frogs (Rana dalmatina). Out of 125 juveniles raised in laboratory without exposure to sex‐reversing stimuli, 6 showed male phenotype but female genotype according to our markers. These individuals exhibited several signs of poor physiological condition, suggesting stress‐induced sex reversal and inferior fitness prospects. Among 162 adults from 11 wild populations in North‐Central Hungary, 20% of phenotypic males had female genotype according to our markers. These individuals occurred more frequently in areas of anthropogenic land use; this association was attributable to agriculture and less strongly to urban land use. Female‐to‐male sex‐reversed adults had similar body mass as normal males. We recorded no events of male‐to‐female sex reversal either in the laboratory or in the wild. These results support recent suspicions that sex reversal is widespread in nature, and suggest that human‐induced environmental changes may contribute to its pervasiveness. Furthermore, our findings indicate that sex reversal is associated with stress and poor health in early life, but sex‐reversed individuals surviving to adulthood may participate in breeding.     

Species composition and nocturnal activity of phlebotomine sand flies (Diptera: Psychodidae) inhabiting a limestone cave in Thailand

We investigated the nocturnal activity of cave‐dwelling sand flies at different time intervals and determined their species composition and seasonal variation. Sand flies were captured on one night each month using CDC light traps from 18:00–06:00 with the collecting bag being changed every two h between February, 2010 and January, 2011. A total of 18,709 individuals, including 10,740 males and 7,969 females, was collected. The overall ratio between male and female specimens was 1:0.74. The collected specimens included 14 species from four genera, Chinius, Idiophlebotomus, Phlebotomus, and Sergentomyia. Sergentomyia phadangensis was the most abundant species (comprising 31.9% of the collected individuals), followed by Se. anodontis (22.8%) and Ph. mascomai (18.2%). The highest number of specimens was collected in July (15.6%), followed by May (15.5%) with the peak of collection recorded at the time interval of 00:01–02:00, followed by 22:01–00:00. However, there were no significant differences observed among time intervals of sand fly collections (p=0.154). Observations of the nocturnal activity of male and female sand flies throughout the night suggest that phlebotomine sand flies show the greatest activity level after midnight.