Solitary Nests Research Articles

Colony disturbance and solitary nest initiation by workers in the obligately eusocial sweat bee, Halictus ligatus

Sweat bees are one of the most socially polymorphic lineages on the planet. In obligately eusocial species, newly enclosed females may become either queens or workers, depending on the environmental and social circumstances of the nest into which they emerge. In socially polymorphic species, females also have the option of nesting solitarily, founding a nest and raising future reproductives alone, without the help of other adult females. Halictus ligatus is a widespread Nearctic, ground-nesting sweat bee. It has been particularly well studied in Ontario, where detailed studies have described it as obligately eusocial. Here we report evidence that the flexibility of female H. ligatus actually extends to expressing behaviour more typical of socially polymorphic species, those in which some individuals reproduce solitarily. In a population in southern Ontario, black wasps (Astata sp.) emerged from the soil beneath the nesting aggregation and proceeded to excavate their own nesting tunnels, dislocating many H. ligatus nest entrances. Young workers whose natal nests were destroyed by the wasp activity constructed new nests, so under very specific circumstances, it is possible for potential altruists to nest solitarily.

Virgin wasps develop ovaries on par with mated females, but lay fewer eggs

In the primitively eusocial wasp Ropalidia marginata, mating is not necessary for a female wasp to develop her ovaries, lay eggs, and even to become the sole egg layer of her colony despite the presence of other mated nestmates. Here, we show that virgin wasps do not differ from their mated counterparts in the extent and rapidity of their ovarian development, in the proportion of individuals that build a nest and laid eggs, and in the time taken to do so. However, a significantly larger proportion of virgin females showed resorbing oocytes, and laid fewer eggs as compared to mated individuals. Thus, virgin females have the ability to develop ovaries and lay eggs but also to refrain from necessarily laying all mature eggs produced, before mating opportunities arise. This dual ability would be adaptive in haplodiploid, tropical species with perennial nesting cycles and frequent opportunities for workers to become replacement queens or solitary nest foundresses throughout the year.

Does coloniality improve foraging efficiency and nestling provisioning? A field experiment in the wild Zebra Finch

The foraging benefits of coloniality, whereby colony members exchange information about food location, have been suggested as a primary factor influencing the evolution of coloniality. However, despite its longstanding popularity, this hypothesis has rarely been tested experimentally. Here, we conducted a field experiment in the wild Zebra Finch Taeniopygia guttata to test whether colonial birds are better at finding food than solitary individuals. We manipulated food patch location and directly measured foraging activity of many colonial and solitary parents at those patches using an electronic monitoring system. We provided nesting sites in excess to alleviate nest site competition and manipulated brood size to eliminate the possible correlation between brood size, nesting density, and individual quality (including foraging activity). We found that solitary birds found experimental food patches first, closely followed by colonial birds. Moreover, solitary parents adjusted the amount of food per nestling to experimental brood size, whereas colonial parents did not, although overall, nestlings were fed more per capita in colonial than in solitary nests. In addition, brood size and, to a lesser extent, nesting density negatively affected nestling growth. Therefore, with the effect of provisioning rate, sibling competition, and cost of coloniality combined, nestling mass was not affected by the brood manipulation in solitary nests, whereas nestlings were lighter in enlarged than in reduced broods in colonies. Our resultstherefore suggest that individuals settling in solitary nests were intrinsically better foragers and more optimal parents. While they do not invalidate the possibility of information transfer at colonies, our findings highlight the importance of considering settlement bias in future studies and add to the existing evidence that the effects of nesting density on fitness are both complex and multiple.

41. Expansion of Ross’s gull nesting range in the north of Yakutia in the 20th century

The nesting sites of Ross’s gull – the North’s legendary bird, first discovered on the northern shores of Canada in 1823 and frequently encountered by Polar researchers in different areas of the Arctic Ocean from the Canadian shores and East-Siberian and Chukchi Seas, were first discovered in 1905 by S.A. Buturlin in the Kolyma River lower stream. Subsequent researchers identified the nesting range of this beautiful bird from the Yana River delta to the Lower Kolyma and Alazeya Rivers (Vorobyov, 1963). In the 1970–1980s the range of the species expanded further to the west. Ross’s gull nesting in the Lena River delta was registered in 1982, 1983, 1984, 1988, 1990 and 1994. Local inhabitants noticed Ross’s gull even farther westward on the Olenyok River and its tributary Bur River (Labutin et al., 1985). Pavlov and Dorogov (1976) write about the Ross’s gull propagation in Taimyr, in the Big Balakhnya River estuary. In early June 1994 we visited Sagystyr Island located in the Big Tumatskaya Channel estuary on the northernmost tip of the Lena River delta, where we found three solitary nests of Ross’s gull. The first two nests were made on a tussock among small lakes. They were made as cavities on the tussocks’ tops where soft moss was mixed with thinly laid dry grass and dwarf willow leaves. The third nest was arranged on the dry place near a geodesic tower and could be easily seen because of a white gull sitting in a neighboring nest and well outlined against the brownish tundra. When the bird left the nest, the nest seemed to disappear as it melted into the surroundings becoming absolutely unnoticeable. Each nest contained three well set eggs and the birds were sitting tightly. They flew up from the nest when a human came within 6–8 m, but they did not fly away and actively attacked the stranger. Ross’s gulls winter in the areas of the Arctic Ocean, the Okhotsk and Bering Seas of the Pacific Ocean. In the last decades the Ross’s gull population has grown considerably in number. However, it still needs human protection. It is necessary to conduct permanent monitoring of the population of this amazing endemic of the North and take all necessary protective measures.

Nesting biology and life cycle of Nomia (Acunomia) chalybeata Smith on Iriomote Island, southernmost Archipelago of Japan, with notes on the simultaneous occurrence of diapausing and non-diapausing prepupae within the same nests (Hymenoptera: Halictidae)

Nesting biology of the nomiine bee, Nomia (Acunomia) chalybeata Smith, was studied in Iriomote Island, Japan (N24°15–25′) in 2003 and 2004. Its nesting period extended for 6months from around the end of April to October. The nest aggregation was found in clay soil under shady conditions. Twenty nests/m2 were present at the highest density spot. Brood numbers in solitary nests were 5–20 (mean±SD: 11.8±4.7, n=14), and in communal nests 12–101 (43.0±41.0, n=3). Each brood cluster in communal nests contained 0–32 brood cells (10.1±8.0, n=13), suggesting that each cohabitant provisioned independently own brood cells. At least 2 and partially 3 generations were estimated to occur in the year; however each nest produced simultaneously non-diapausing and diapausing prepupae. The percent rate of diapausing prepupae differed seasonally, and was 20.0–37.5% (30.3±7.5%, n=3) in overwintered generation and 0–100% (50.0±39.8%, n=9) in first generation, suggesting that the rate of production of dormant prepupae increased toward the later activity season. Production of the diapausing prepupae may function potentially to inhabit widely throughout different climatic zones. Female ratio (females/females+males) in overwintered generation was 0.347 (50/144). Nest architecture, occurrence of communal nests and breaking of prepupal diapause are also mentioned.

Genetic Relatedness of Low Solitary Nests of Apis dorsata from Marang, Terengganu, Malaysia

Knowledge on the population of genetic structure and ecological behaviour of Apis dorsata from Peninsular Malaysia is needed for effective management and conservation of this species since unsustainable whole solitary low nest cutting for product harvesting is the current common practice here. The analysis of 15 single locus DNA microsatellite markers on samples from 20 solitary nests of A. dorsata showed that while these markers were polymorphic, high intracolonial relatedness existed. Furthermore, in general, slightly negative values of intercolony relatedness (R) among the nests of A. dorsata were found. However, positive values of mean intercolony relatedness were observed between 54 pairs of nests out of 190 possible combinations. The R values among nest pairs 3–4 and 3–5 was higher than 0.50 showing that their queens were half siblings, whereas nest pair 19–20 showed relatedness of 0.95 indicating that the same queen was sampled. The results that we obtained could not conclusively support the hypothesis of this study that the honey hunters in Marang district of Malaysia repeatedly harvest the same nest located at a different site and at a different time during the same honey harvesting season. However, our finding of an appreciable level of intercolonial relatedness between several pairs of nests in this pioneer study indicated that a comprehensive study with a larger sample size of solitary nests found throughout the region would be necessary to provide concrete proof for this novel idea.

A mid-cretaceous origin of sociality in xylocopine bees with only two origins of true worker castes indicates severe barriers to eusociality.

The origin of sterile worker castes, resulting in eusociality, represents one of the major evolutionary transitions in the history of life. Understanding how eusociality has evolved is therefore an important issue for understanding life on earth. Here we show that in the large bee subfamily Xylocopinae, a simple form of sociality was present in the ancestral lineage and there have been at least four reversions to purely solitary nesting. The ancestral form of sociality did not involve morphological worker castes and maximum colony sizes were very small. True worker castes, entailing a life-time commitment to non-reproductive roles, have evolved only twice, and only one of these resulted in discrete queen-worker morphologies. Our results indicate extremely high barriers to the evolution of eusociality. Its origins are likely to have required very unusual life-history and ecological circumstances, rather than the amount of time that selection can operate on more simple forms of sociality.

Gregarious nesting—An anti-predator response in laying hens

Gregarious nesting can be defined as a behaviour that occurs when a laying hen (Gallus gallus domesticus) given the choice between an occupied and an unoccupied nest site chooses the occupied nest site. It occurs frequently in flocks of laying hens kept under commercial conditions, contrasting the behaviour displayed by feral hens that isolate themselves from the flock during nesting activities. What motivates laying hens to perform gregarious nesting is unknown. One possibility is that gregarious nesting is an anti-predator response to the risk of nest predation emerging from behavioural flexibility in nesting strategy. The aim of the present experiment was to investigate whether gregarious nesting due to behavioural flexibility in nesting strategy is an anti-predator response. Twelve groups of 14–15 Isa Warren hens age 44 weeks were housed in pens each containing three adjacent roll-out nest boxes. Nesting and spacing behaviour were video recorded for 5 days in each of three distinct periods; (a) pre-predator; a pre-exposure period, (b) predator; a period with daily exposure to a simulated attack by a lifelike flying model of a hooded crow (Corvus cornix, a potential egg-predator), and (c) post-predator; a post-exposure period. Additional data collected were the behaviour of each hen 5min prior to and 10s after the simulated predator attacks. The hens reacted with fear-related behaviour to the simulated predator attacks, e.g. the number of hens engaged in normal non-agitated behaviour decreased from before to after exposure to the predator model (P<0.001), and this did not change with day of exposure (P>0.05). The proportion of gregarious nest box visits of the total number of visits, where the hens had a choice between gregarious or solitary nesting, was found to be higher during the predator period (P<0.01). The general distribution of hens in the pens did not change between periods (P>0.05). In conclusion, evidence was found for the proposed hypothesis that gregarious nesting is an anti-predator response.

Strong site fidelity and longer internesting interval for solitary nesting olive ridley sea turtles in Brazil

Olive ridley sea turtles display two different types of nesting behavior: in arribada (synchronous mass nesting) or solitarily. Contrarily to arribadas, little has been published about solitary nesters. This study aimed to expand the knowledge on internesting interval and site fidelity of solitary nesting olive ridleys and to test a possible development of arribada nesting behavior. Data were collected in Sergipe (Brazil) over 125 km of beach from 10°30′S/36o23′W to 11°26′S/37o19′W, between nesting seasons 2004/2005 and 2006/2007. From 962 tagged females, 173 were seen renesting. The average internesting interval found was longer (22.35 ± 7.01 days) than previously described, which might relate to lower water temperatures during the internesting period. Olive ridleys at Sergipe showed high nesting site fidelity, with consecutive nesting events occurring in close proximity, non-randomly and dependently of previous events. Most of the consecutive nests were separated by 4.06–5.59 km. Development of arribada nesting behavior was not confirmed.

Queen signal should be honest to be involved in maintenance of eusociality: chemical correlates of fertility in Ropalidia marginata

Queens of many social insect species are known to maintain reproductive monopoly by pheromonal signalling of fecundity. Queens of the primitively eusocial wasp Ropalidia marginata appear to do so using secretions from their Dufour’s glands, whose hydrocarbon composition is correlated with fertility. Solitary nest foundresses of R. marginata are without nestmates; hence expressing a queen signal can be redundant, since there is no one to receive the signal. But if queen pheromone is an honest signal inextricably linked with fertility, it should correlate with fertility and be expressed irrespective of the presence or absence of receivers of the signal, by virtue of being a byproduct of the state of fertility. Hence we compared the Dufour’s gland hydrocarbons and ovaries of solitary foundresses with queens and workers of post-emergence nests. Our results suggest that queen pheromone composition in R. marginata is a byproduct of fertility and hence can honestly signal fertility. This provides important new evidence for the honest signalling hypothesis.

Taxonomy and antimicrobial activity of moderately salt-tolerant and alkaliphilic Streptomyces sp. MN 9(V) isolated from solitary wasp mud nest

An actinobacterium strain designated as MN 9(V) was isolated from solitary wasp mud nest obtained from the walls of buildings located in Dehradun, India. MN 9(V) was subjected to polyphasic taxonomic characterization. The organism produced light-grey aerial mycelium with brown-coloured diffusible pigment. This isolate showed growth in medium containing 8% NaCl, at pH 8–10 and at a temperature range of 27–45°C. Micromorphology and chemotaxonomic characteristics were consistent with its assignment to the genus Streptomyces. Analysis of 16S rDNA gene sequences showed that MN 9(V) formed a separate clade with Streptomyces cellulosae NRRLB-2889T and Streptomyces pseudogriseolus NRRL B-3288T being most closely related with a sequence similarity of 99%. However, a number of phenotypic characteristics readily distinguished the strain MN 9(V) from the type strains. The strain MN 9(V) showed strong antimicrobial activity against several test organisms, including multidrug resistant bacteria, as well as against fungal pathogens.

Availability and depletion of fat reserves in halictid foundress queens with a focus on solitary nest founding

Foundress queens of social Hymenoptera require considerable amounts of energy for survival, solitary nest founding, provisioning of the first brood, and egg production. Energy reserves in insects mostly consist of fat. We investigated how hibernation and the subsequent flight season, especially the solitary nest founding phase, influenced the abdominal fat content of gynes in the primitively eusocial sweat bee, Lasioglossum malachurum (Hymenoptera, Halictidae). In our study population, sexuals are produced in both the second and the third broods. Emerging gynes of the third brood had significantly more fat than those of the second brood, whereas there was no such difference in males. As expected, fat reserves in samples of female sexuals caught at emergence, after hibernation, during solitary nest founding, and at the end of the social phase of the nest cycle indicate a severe decrease of reserves that was highest during the 7 weeks of the solitary founding phase. Thus, the amount of fat reserves of foundress queens seems to be crucial, particularly for nest founding. However, investment of energy reserves in the solitary nest founding phase has probably to be balanced with the subsequent social phase in a way that maximizes the queen’s fitness. Possible consequences for the complexity and progress of the nest cycle are discussed.

Fitness consequences of ecological constraints and implications for the evolution of sociality in an incipiently social bee

Ecological constraints such as resource limitation, unfavourable weather conditions, and parasite pressure have long been considered some of the most important selective pressures for the evolution of sociality. In the present study, we assess the fitness consequences of these three ecological factors on reproductive success of solitary nests and social colonies in the socially polymorphic small carpenter bee, Ceratina australensis, based on 982 nests collected over four reproductive periods. Nest site limitation was predicted to decrease opportunities for independent nest initiation and increase the frequency of social nesting. Nest sites were not limiting in this species and the frequency of social nesting was consistent across the four brood-rearing periods studied. Unfavourable weather was predicted to lower the frequency of female dispersal from their natal nests and to limit the brood-rearing season; this would increase the frequency and fitness of social colonies. Daily temperature and precipitation accumulation varied between seasons but were not correlated with reproductive success in this bee. Increased parasite pressure is predicted to increase the frequency and fitness of social colonies because solitary bees must leave the nest unattended during foraging bouts and are less able to defend the nest against parasites. Severe parasitism by a chalcid wasp (Eurytoma sp.) resulted in low reproductive success and total nest failure in solitary nests. Social colonies had higher reproductive success and were never extirpated by parasites. The high frequency of solitary nests suggests that this is the optimal strategy. However, social colonies have a selective advantage over solitary nesting females during periods of extreme parasite pressure, and we suggest that social nesting represents a form of bet-hedging against unpredictable fluctuations in parasite number.

Support for maternal manipulation of developmental nutrition in a facultatively eusocial bee, Megalopta genalis (Halictidae).

Developmental maternal effects are a potentially important source of phenotypic variation, but they can be difficult to distinguish from other environmental factors. This is an important distinction within the context of social evolution, because if variation in offspring helping behavior is due to maternal manipulation, social selection may act on maternal phenotypes, as well as those of offspring. Factors correlated with social castes have been linked to variation in developmental nutrition, which might provide opportunity for females to manipulate the social behavior of their offspring. Megalopta genalis is a mass-provisioning facultatively eusocial sweat bee for which production of males and females in social and solitary nests is concurrent and asynchronous. Female offspring may become either gynes (reproductive dispersers) or workers (non-reproductive helpers). We predicted that if maternal manipulation plays a role in M. genalis caste determination, investment in daughters should vary more than for sons. The mass and protein content of pollen stores provided to female offspring varied significantly more than those of males, but volume and sugar content did not. Sugar content varied more among female eggs in social nests than in solitary nests. Provisions were larger, with higher nutrient content, for female eggs and in social nests. Adult females and males show different patterns of allometry, and their investment ratio ranged from 1.23 to 1.69. Adult body weight varied more for females than males, possibly reflecting increased variation in maternal investment in female offspring. These differences are consistent with a role for maternal manipulation in the social plasticity observed in M. genalis.

Cryptic Plasticity Underlies a Major Evolutionary Transition

The origin of eusociality is often regarded as a change of macroevolutionary proportions [1, 2]. Its hallmark is a reproductive division of labor between the members of a society: some individuals ("helpers" or "workers") forfeit their own reproduction to rear offspring of others ("queens"). In the Hymenoptera (ants, bees, wasps), there have been many transitions in both directions between solitary nesting and sociality [2-5]. How have such transitions occurred? One possibility is that multiple transitions represent repeated evolutionary gains and losses of the traits underpinning sociality. A second possibility, however, is that once sociality has evolved, subsequent transitions represent selection at just one or a small number of loci controlling developmental switches between preexisting alternative phenotypes [2, 6]. We might then expect transitional populations that can express either sociality or solitary nesting, depending on environmental conditions. Here, we use field transplants to directly induce transitions in British and Irish populations of the sweat bee Halictus rubicundus. Individual variation in social phenotype was linked to time available for offspring production, and to the genetic benefits of sociality, suggesting that helping was not simply misplaced parental care [7]. We thereby demonstrate that sociality itself can be truly plastic in a hymenopteran.

Embryonic mortality as a cost of communal nesting in the delicate skink

Lizards are appropriate organisms to investigate causes and correlates of communal egg laying because their general lack of parental care focuses attention on nest site choice. We field-tested hypotheses associated with nest site choice and communal egg laying in the delicate skink Lampropholis delicata, in south-eastern Australia. Specifically, we predicted that lizards would nest at sites with lower openness and solar radiation than random sites, but within crevices with higher humidity than random crevices. However, we predicted that these environmental factors would not differ between communal and solitary nest sites (based on previous research), but that egg mortality in communal nests would be higher than that in solitary nests due to conspecific interference. Despite being ground dwellers, skinks in this population nested above the ground level in narrow horizontal crevices within vertical faces of sandstone outcrops. At the broadest scale, skinks nested at sites with significantly lower canopy openness and incident (solar) radiation than random sites, while at the smallest scale, skinks nested in crevices with significantly higher relative humidity than potential nest crevices. Humidity averaged 94% in nest sites, and nesting females did not trade-off humidity for temperature, despite an inverse relationship between the two at potential nest sites. Of 60 nests, about half to two-thirds were communal. Communal nest sites did not differ from solitary nest sites with respect to temperature, humidity, rock size, aspect, height of crevice above ground, or crevice dimensions. Eggs from communal nests were three times more likely to desiccate and perish than eggs from solitary nests, a clear cost of communal nesting. Desiccation was caused by eggs being displaced from their original positions within the crevices, possibly by conspecific gravid females.

Reproductive success in a socially polymorphic spider: social individuals experience depressed reproductive success in isolation

1. Correlated individual differences in behaviour across ecological contexts, or behavioural syndromes, can theoretically constrain individuals' ability to optimally adjust their behaviour for specific contexts. 2. Female Anelosimus studiosus exhibit a unique behavioural polymorphism: ‘social’ females are tolerant of conspecifics and aggregate in multi-female colonies, while ‘solitary’ females aggressively defend their singleton webs from intrusion by adult female conspecifics. Previous work found that social females are also less aggressive toward prey and are more fearful of predators. 3. In this study we quantify potential fitness consequences of these correlated behaviours by examining the potential and realised fecundities of the two phenotypes in naturally occurring colonies, and by quantifying their ability to rear offspring as singleton individuals. 4. There were no differences in the fecundities of laboratory-reared females between the phenotypes, nor were there differences in field-collected brooding females from naturally occurring solitary and social nests. 5. Brooding females from solitary and social colonies that were isolated in new nests for the growing season were both capable of rearing their broods; however, females from solitary nests had significantly greater success. 6. These results suggest a fitness consequence to the reduced-aggression syndrome of social females that may represent a general impediment to the evolution of sociality in spiders.

A new material for old solutions—the case of plastic string used in Great Grey Shrike nests

Innovative behaviours are defined as new behaviour patterns derived by the modification of pre-existing ones. To date, studies of animal innovation have focussed mainly on foraging activity. In this paper, we focussed on the innovative use of a new material—man-made plastic (polypropylene) string—in nest construction by a solitary nesting, territorial species, the Great Grey Shrike Lanius excubitor. An analysis of field data collected during the years 1999–2006 during intensive shrike research in Poland, as well as of nest record cards since 1964, suggests that plastic string has been a very popular nest material since the 1980s. Recently, plastic string was used significantly more often by shrikes living in intensive farmland habitats than by those in more natural meadows. We discuss the possible benefits of the use of plastic string, such as strengthening the nest structure and therefore helping to protect eggs and nestlings from inclement weather conditions, such as strong winds. On the other hand, the use of plastic string has a real cost for breeding Great Grey Shrikes because both adult birds and nestlings may get tangled in it.

Social polymorphism in the Australian small carpenter bee, Ceratina (Neoceratina) australensis

The bee tribe Ceratinini provides important insights into the early stages of sociality. Many arthropods exhibit behaviours precursory to social life, including adult longevity, parental care, nest loyalty and mutual tolerance, yet the origins of social behaviour are few. Here we describe the biology of a facultatively social bee, Ceratina (Neoceratina) australensis, which exhibits all of the preadaptations for successful group living, yet presents ecological and behavioural characteristics that seemingly disfavour frequent colony formation. This species is socially polymorphic with both solitary and social nests collected in sympatry. Social colonies consist of two foundresses, one contributing both foraging and reproductive effort and the second which remains at the nest as a passive guard. Cooperative nesting provides no overt reproductive benefits over solitary nesting in this population, although brood survival tends to be greater in social colonies. Maternal longevity, subsociality and bivoltine nesting phenology in this species favour colony formation, while dispersal habits and offspring longevity may inhibit more frequent social nesting in this and other ceratinines.

Reproductive Success of Burrowing Owls in Urban and Grassland Habitats in Southern New Mexico

Abstract We examined Burrowing Owl (Athene cunicuaria) reproductive success at 144 nests in urban (n = 80) and grassland (n = 64) habitats in southern New Mexico in 2000 and 2001. Nest success was higher in grassland compared to urban areas (81 vs. 68%) but urban landscapes fledged more young per successful nest (3.85 vs. 3.07). Mean fledging success per nest was similar between habitats with 2.60 and 2.50 fledglings in urban and grassland habitats, respectively. Fledging success was categorized as failure, low, and high. Reproductive success in both habitats was associated with measures of owl density. High success in urban landscapes was associated with fewer surrounding nests, an index of larger nesting territories, and open space. Failure was associated with solitary nests. This suggests owls benefit from the presence of other nesting pairs as long as the density is not too high. High success in grassland habitats was associated with fewer surrounding nests, index of larger nesting territories, ed...