Nestmate recognition of the stingless beeTrigona (Tetragonula) minangkabau (Apidae: Meliponinae)

Nestmate recognition was studied in the Southeast Asian stingless beeTrigona (Tetragonula) minangkabau, a species in which worker oviposition has not been observed in queenright or queenless colonies. When conspecific non-nestmate foragers from queenright and queenless colonies were introduced to the observed colony, they were all rejected by guards. Foragers of a different species (Trigona (Tetragonisca) angustula) were also completely rejected. However, conspecific non-nestmate callows were accepted as often as were nestmate callows, although guards recognized the difference. Accepted non-nestmate callows exchanged food with guards equally as much as nestmate callows did.     

Combined effect of ENSO and SAM on the population dynamics of the invasive yellowjacket wasp in central Chile

The population dynamics of the yellowjacket wasp (Vespula germanica Fabricus) in central Chile were analyzed for the first time. Using a simple Ricker logistic model and adding the effects of local weather variables (temperature and precipitation) and large-scale climate phenomena as El Niño Southern Oscillation (ENSO) and the Southern Annular Mode (SAM), we modeled the interannual fluctuations in nest density. The best model according to the Bayesian information criterion (BIC) included 1-year-lag negative feedback combined with the positive additive effects of ENSO and SAM. According to this model, yellowjacket nest density was favored by warm and dry winters, which probably influenced the survival of overwintering queens. Large-scale climatic variables [Southern Oscillation Index (SOI) and SAM] described the effect of exogenous factors in wasp fluctuations better than local weather variables did. Our results emphasize the usefulness of climate indices and simple theoretical-based models in insect ecological research.     

Diversity and Phenology of Wild Bees in a Highly Disturbed Tropical Dry Forest “Desierto de la Tatacoa”, Huila–Colombia

Colombian tropical dry forest is considered the most endangered tropical biome due to anthropic activities. Desierto de la Tatacoa (DsT) is an example of high disturbed tropical dry forest which still maintains a high biodiversity. The objective of the study was to record the diversity and phenology of wild bees in this place by monthly sampling between December 2014 and December 2016 in a 9-km² area. During the study, there was a prolonged El Niño–Southern Oscillation period. Bees were collected by entomological nets, malaise traps, eugenol scent trapping, and nest traps. Shannon index was calculated to estimate diversity and Simpson index to determine dominance of a species. The effect of environmental conditions (wet and dry season) in richness and abundance was analyzed by paired T tests. A total of 3004 bee specimens were collected, belonging to 80 species from Apidae, Megachilidae, Halictidae, and Colletidae. Apidae was the most diverse. Shannon index value was 2.973 (discarding Apis mellifera Linnaeus 1758 data); thus, DsT can be considered as a zone of high wild bee diversity. Dry and rainy season showed differences in diversity (p?<?0.05). Rainy season showed larger blooming periods and higher bee diversity than dry season. In both seasons, social species were dominant (e.g., A. mellifera or Trigona fulviventris Guérin 1844). Although DsT is a highly disturbed ecosystem, this study found it has the second highest number of genera and the fourth highest number of species reported in Colombia.     

Preliminary Evidence of the Importance of ENSO in Modifying Food Availability for White‐tailed Deer in a Mexican Tropical Dry Forest1

The influence of El Niño/Southern Oscillation (ENSO) on rainfall and its possible effect on availability of food for white‐tailed deer (Odocoileus virginianus) in a tropical dry forest in the Pacific coast of Mexico was studied. From 1977 to 2003 there were three significant El Niño and La Niña events. During El Niño years rainfall decreased during the wet season ( June to October) and increased during the dry season (November to May), with the opposite effect during La Niña years. Plant diversity was monitored in permanent plots during the wet and dry seasons of 1989–1993. The results provide evidence that ENSO events affect deer food availability, particularly in the dry season.     

Nest site selection by fire ant queens

Summary We examined nest site selection by foundresses of the polygyne form ofSolenopsis invicta. In the laboratory, foundresses were allowed to nest in control soil vs. soil inoculated with refuse from a colony ofPheidole dentata, a natural enemy. In a second experiment foundresses chose between control andS. invicta soil. More foundresses (100%) avoided the soil of a natural enemy than the soil of a conspecific colony (79%) that may accept them into the nest. Foundresses from this polygyne ant appear to avoid other colonies in general, but avoid heterospecific colonies more.     

Variation in a sparrow's reproductive success with rainfall: food and predator-mediated processes

From 1997 to 1999, we monitored the reproductive success of individual rufous-crowned sparrows (Aimophila ruficeps) in coastal sage scrub habitat of southern California, USA. Annual reproductive output of this ground-nesting species varied strongly with annual variation in rainfall, attributed to the El Niño-Southern Oscillation. Birds fledged 3.0 young per breeding pair in 1997, when rainfall was near the long-term mean, 5.1 offspring per pair in 1998, a wet El Niño year, and 0.8 fledglings per pair in 1999, a dry La Niña year. Variation in many components of reproductive output was consistent with the hypothesis that food availability was positively correlated with rainfall. However, the factor most responsible for the high reproductive output in 1998 was low early season nest predation which, combined with favorable nesting conditions, enabled more pairs to multiple-brood. Cool, rainy El Niño conditions may have altered the activity of snakes, the main predator of these nests, in the early season of 1998. Overall, more of the annual variation in fecundity was attributable to variation in within-season components of reproductive output (mean number of nests fledged per pair) than to within-nest components (mean brood size). Annual variation in rufous-crowned sparrow fecundity appears to be driven primarily by food resource-mediated processes in La Niña years and by predator-mediated processes in El Niño years.     

Ecological studies ofRoparidia fasciata in Okinawa island I. Distribution of single- and multiple-foundress colonies

To compare between a single-foundress colony and a multiple-foundress colony at the pre-emergence state of a social wasp, R. fasciata, nest distributions and colony terminations were investigated in 8 sites with different environmental conditions. Marking experiments were also conducted in two sites at high wasp density.

1. Foundress populations were composed of single-foundress colonies in sites C, D and E, new environments where have recently suited for inhaviting, at low wasp density. In sites like A and B which were used year after year, at high wasp density, coexistence of multiple-and single-foundress colonies was observed.
2. From the marking experiment, nests initiated by a single foundress were more distant away from the nest where the original foundress emerged the fall before, compared to multiple-foundress nests which were initiated by multiple foundress.
3. Greater percentage of colony termination was observed in single-foundress nests than in multiple-foundress nests, and the colony termination in single-foundress colonies increased with the nest density.
4. Ant predation was the key factor causing the variation of the percentage of colony termination.

     

Collective control of nest climate parameters in bumblebee colonies

We examined two aspects of the social control of nest climate in bumblebee colonies: which parameters of nest climate bumblebees actively down-regulate by fanning and the dynamics of the colony response as colony size increased. Colonies of Bombus terrestris were exposed to an increase in carbon dioxide, temperature or relative humidity. We performed 70 temperature trials (six colonies), 58 CO₂ trials (four colonies) and four humidity trials (two colonies). An increase in CO₂ concentration and temperature elicited a fanning response whereas an increase in relative humidity did not. This is the first report of fanning in bumblebee colonies to control respiratory gases. The number of fanning bees increased with stimulus intensity. The colony response to a CO₂ concentration of 3.2% was comparable to the colony response to a temperature of 30°C. A marked fanning response occurred at 1.6% CO₂, a concentration never exceeded in a large field nest during a pilot measurement of 10 days. We investigated the colony response over a wide range of colony sizes (between 10 and 119 workers). The proportion of the total workforce invested by colonies in nest ventilation did not change significantly; thus, the number of fanning workers increased with colony size. Furthermore, as colony size increased, the dynamics of the colony response changed: colonies responded faster to perturbations of their environment when they were large (60 or more individuals) than when they were small. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Colony size and not nest density drives reproductive output in the Common Tern Sterna hirundo

Density is known to be an important factor in population size regulation. Several mechanisms of density limitation have been identified in colonial birds. We studied competition in Common Terns Sterna hirundo to assess whether the factor limiting reproductive output was competition for nest‐sites, which is dependent on local nest density, or density‐dependent competition for food resources, which is dependent on overall colony size using the same foraging area. We found strong associations of both colony size and nest density with reproductive output in five colonies of Common Terns in three different habitats (one marine, two freshwater). Based on detailed long‐term datasets of six separate sub‐colonies of the Banter See colony that differed in nest density, we found that reproductive success was not related to nest density but to overall colony size, possibly a result of resource depletion and food competition. We also found carry‐over effects of colony size during rearing on post‐fledging return rate. These results have important implications for the conservation management plans aimed at recovering declining populations of Common Terns.     

Nest relocation in the slavemaking ants Formica subintegra and Formica pergandei: a response to host nest availability that increases raiding success

Social insects typically occupy spatially fixed nests which may thus constrain their mobility. Nevertheless, colony movements are a frequent component of the life cycle of many social insects, particularly ants. Nest relocation in ants may be driven by a variety of factors, including nest deterioration, seasonality, disturbances, changes in microclimate, and local depletion of resources. The colony movements of slavemaking ants have been noted anecdotally, and in recent studies such relocations were primarily attributed to nest deterioration or shifts to overwintering locations. In this study we explore nest relocations in large colonies of formicine slavemakers which occupy stable and persistent earthen nest mounds. We investigate the hypothesis that colony relocations of these slavemakers are best explained by efforts to improve raiding success by seeking areas of higher host availability. Five summers of monitoring the raiding behavior of 11–14 colonies of the slavemakers Formica subintegra and Formica pergandei revealed relatively frequent nest relocations: of 14 colonies that have been tracked for at least three of 5 years, all but one moved at least once by invading existing host nests. Movements tended to occur in the middle of the raiding season and were typically followed by continued raiding of nearby host colonies. Spatial patterns of movements suggest that their purpose is to gain access to more host colonies to raid: the distance moved is typically farther than the mean raiding distance before the move, which may indicate an effort to escape their local neighborhood. Furthermore, the mean distance of raids after relocation is shorter than the distance before relocation. For many slavemaking ant colonies, particularly those on the verge of relocating, raiding distance increased as the raiding season progressed. In addition, movements tended to be toward areas of higher local host density. Nest relocation is likely an important component of the ecology of slavemaking ants that contributes to the dynamic nature of their interaction with the host ant population.     

Breeding success and chronology of Wood Storks Mycteria americana in northern and central Florida, U.S.A.

The breeding success and chronology of Wood Storks Mycteria americana were studied at eight colonies in northern and central Florida during 1981–1985. Mean ± s.d. clutch size for all colony-years was 3.07 ± 0.56 (n = 2694 nests), with three-egg clutches (72%) most frequent. Mean clutch size among all colonies and years ranged from 2.73 ± 0.55 to 3.41 ± 0.61. Many colonies exhibited significant negative trends in clutch size with, hatching date because of a proportional decrease in four-egg clutches later in the season. Mean colony clutch size was not correlated with nest numbers, nesting density or mean hatching date within most years. Mean ± s.d. number of fledglings for all colonies and years was 1.29 ± 1.16 fledglings per nest (n = 2812 nests). Mean annual fledging rates in colonies ranged from 0 (colony failed) to 2.66 fledglings per nest. Most breeding failure occurred prior to egg hatching, and the second highest mortality occurred between hatching and 2 weeks of age. Four-egg clutches fledged more storks than three-egg clutches, which in turn were more successful than two-egg clutches. However, all clutch sizes showed similar fledgling per egg rates. The seasonal decline in productivity was associated proportionally with smaller clutch sizes later in the breeding season. An increase in mean hatching date was correlated with an increase in latitude. There was greater within-year breeding synchrony among colonies than interyear breeding synchrony within each colony. Breeding synchrony was not correlated with mean hatching date, latitude, longitude, nest numbers or nesting density.     

Intraspecific variation in size and density of Avocet colonies: effects of nest-distances on hatching and breeding success

In many colonial bird species there is considerable intraspecific variation in colony size and inter‐nest distance (colony density). Possible causes of this variation and its effects on hatching success (survival of eggs) and breeding success (probability of a pair raising chicks) were studied in 48 Avocet Recurvirostra avosetta colonies in Schleswig‐Holstein (Germany) between 1991 and 1996. Colony density was influenced by time of year and habitat (categories: island or mainland, close to or far from feeding grounds). Colonies on islands had the highest densities. When all available space at a colony site was used, colonies became very dense (mean nearest‐neighbour nest distance less than 1 m). Colony size (number of clutches) was influenced by time of year, but not by habitat. Hatching success was low in high density colonies and in very low density ‘colonies’ (single nests) and high over a broad range of intermediate nest densities. The low success rate of single nests was caused by a very high predation rate, whereas the low success rate in very dense colonies was caused by a high rate of nest abandonment. Nest abandonment in very dense colonies was associated with a high level of aggressiveness among Avocets during the egg‐laying period. Due to territorial behaviour, Avocets seemed to be expelled from the densest breeding sites. In very dense colonies, high frequencies of clutches of unusual size occurred due to conspecific nest parasitism. The number of Avocets taking part in attacks on potential egg predators was small and (in colonies of more than one clutch) depended neither on colony size nor on colony density. Despite a low hatching success in very dense colonies, individuals breeding in the densest colonies had significantly better chances of raising chicks than Avocets breeding in less dense colonies. Coloniality seemed to be obligatory for Avocets in order to ensure hatching success. The size and density of colonies seemed to be associated with the availability of suitable nesting habitats (islands).     

Foraging behavior of individual workers and foraging dynamics of colonies of three Sumatran stingless bees

The foraging behavior of three stingless bees, Trigona (Tetragonula) minangkabau, T. (Trigonella) moorei and T. (Heterotrigona) itama, was studied to describe patterns of resource harvest in disturbed forest areas in Sumatra, Indonesia.

1. Average daily total number of foraging flights per colony was 1200 in T. minangkabau, 2400 in T. moorei and 7000 in T. itama and it was proportional to colony population size. Foragers collecting nectar, pollen or plant resin were respectively 70–80%, 10–20% and <10% in the three species. Pollen was collected most in the morning. Nectar collection peaked in midday in T. itama but continued almost evenly until dusk in T. minangkabau and T. moorei. Resin was collected evenly throughout day.
2. In all the three species the volume of a nectar load carried by a returning forager did not decrease until 1600, followed by slight decline. In the morning the sugar concentration of nectar was almost constantly 30%, and in the afternoon its maximum value reached 60% although some remained 30%. As a result, the mean sugar weight in a nectar load gradually increased until dusk.
3. In T. minangkabau, resin was collected by specialized foragers. Nectar foragers switched to collect pollen and vice versa. There were two types of foraging: “exploitatory” flights, the repitition of short, rather constant flights bringing back full resource loads, and “exploratory” flights, prolonged flight and/or reduction in amount of resources carried. Exploitatory flights followed the exploratory flights which led to discovery of rich sources. Mean duration of exploitatory flights was 7 min during nectar collection, 12 min for pollen and 23 min for resin. Sites of exploited flowers were estimated to be 84–434 m distant from the nest site. Mean duration of flights for nectar collection was 13 min in the morning and 6 min in the late afternoon.

     

The effects of interspecific interactions on resource use and behavior in a desert ant

We examined how interspecific competition in ants affects resource use and behavior. To test how neighboring Myrmecocystus colonies influence the desert ant Aphaenogaster cockerelli, we placed temporary enclosures around Myrmecocystus spp. colonies and recorded the resources collected by A. cockerelli and the numbers of A. cockerelli ants engaged in various tasks outside the nest. When neighbors were enclosed, A. cockerelli colonies collected a significantly higher proportion of termites and significantly less plant matter than when neighbors were active. The numbers of A. cockerelli ants engaged in foraging behavior and nest maintenance work increased when Myrmecocystus colonies were enclosed. Interspecific interactions thus can affect the behavior and resource use of A. cockerelli colonies and may influence colony fitness.     

Behavioural specialization in pre-reproductive colonies of the allodapine beeExoneura bicolor (Hymenoptera: Anthophoridae)

Summary Exoneura bicolor is a univoltine allodapine bee common in montane forests of southern Australia, where it exhibits a semisocial/quasisocial colony organization. Within-nest behaviour in postemergence autumn nests ofExoneura bicolor was recorded with the aim of studying behavioural specialization in pre-reproductive colonies. Ten complete colonies were transferred to purpose-built observation nests shortly before brood eclosion in late summer. Behaviour within observation nests was recorded for periods of up to 44 days after establishment, covering a period when colonies are preparing for overwintering. Dispersal of females and brood rearing do not occur at this time, although some females may become inseminated. Analyses of data using multivariate techniques indicated four distinguishable behavioural castes, designated here as Guards, Nest Absenters, Nest Modifiers and Non-recruits. This represents a higher degree of behavioural specialization than recorded to date for other allodapines. Behaviours performed by Guards and Nest Absenters are likely to involve considerable risks, but benefit the colony as a whole, so that some nestmates in prereproductive colonies exhibit altruism that frequently aids adult siblings or cousins. The males in our study were fed by females via trophallaxis and two of the males participated in nest maintenance tasks. Our results suggest that autumn colonies ofE. bicolor form well-integrated behavioural units even though brood rearing does not commence until the following spring.     

Suburban sprawl: environmental features affect colony social and spatial structure in the black carpenter ant,Camponotus pennsylvanicus

1. In social insects, the number of nests that a colony inhabits may have important consequences for colony genetic structure, the number of queens, sex allocation, foraging efficiency, and nestmate recognition. Within the ants, colonies may either occupy a single nest (monodomy) or may be organised into a complex network of nests and trails, a condition known as polydomy. 2. The current study is a large‐scale, long‐term, comprehensive field examination of various features of colony social and spatial structure in the facultatively polydomous black carpenter ant, Camponotus pennsylvanicus (DeGeer). The study examined the density, persistence, and the spatiotemporal distribution of colonies across a gradient of land disturbance associated with urban development. The temporal and spatial pattern of nest use was compared between fragmented landscapes where nesting sites were interspersed among human‐built structures (urban plots) and less disturbed landscapes with higher tree density (suburban plots). In addition, nesting site fidelity and changes in colony spatial structure were monitored over 7 years. 3. Long‐term monitoring and extensive sampling over a large spatial area allowed the first comprehensive insight into the spatiotemporal dynamics of colony and population structure in C. pennsylvanicus. A total of 1113 trees were inspected over 233 ha. Camponotus pennsylvanicus were active on 348 of the 1113 trees (31%) and these represented 182 distinct colonies. The colonisation rate remained relatively stable over 7 years suggesting that an equilibrium point had been reached. Relative to the suburban plots, tree density was 65% lower in the urban plots. The proportion of trees colonised by C. pennsylvanicus was significantly higher in the urban plots suggesting that intraspecific competition for nesting sites may be especially high in areas with lower tree density. Colony spatial structure also differed significantly between habitats and a higher incidence of monodomy was observed in the urban environment. The average number of trees per colony across all subplots was 1.95 (range 1–4) indicating that C. pennsylvanicus are weakly polydomous. 4. The composite picture that emerges for C. pennsylvanicus colonies in the urban habitat is a chain reaction of events: (i) the urban habitat has a lower tree density, (ii) lower tree density results in higher tree colonisation rate, (iii) higher tree colonisation rate results in simpler colony spatial structure (i.e. higher incidence of monodomy), and (iv) simpler colony spatial structure results in numerically smaller colonies. Long‐term monitoring of the spatiotemporal pattern of nest site use in selected colonies revealed a unique trend. While worker counts in selected colonies remained relatively stable throughout the course of the study, colony spatial structure changed considerably with 28% of colonies experiencing a change. Furthermore, the likelihood of detecting a change in colony spatial structure increased with the amount of time passing from the initial inspection. 5. In conclusion, tree density has a significant effect on a number of important colony features in C. pennsylvanicus. Besides tree density, other environmental features such as human‐built structures cause habitat fragmentation and may act as natural barriers to worker dispersal and/or foraging. Such barriers may ultimately affect the social and/or spatial structure at both the colony and the population level.     

Workers’ Extra-Nest Behavioral Changes During Colony Fission in Dinoponera quadriceps (Santschi)

Ant colonies can reproduce by two strategies: independent foundation, wherein the queen starts a new colony alone, and dependent foundation, in which workers assist the queen. In the queenless species Dinoponera quadriceps (Santschi), the colony reproduces obligatorily by fission, a type of dependent foundation, but this process is not well understood. This study describes a colony fission event of D. quadriceps in the field and analyzes the influence of the fission process on workers’ extra-nest behavior. Based on observations of workers outside the nest, five distinct stages were identified: monodomic stage, polydomic stage, split stage, conflict stage, and post-conflict stage. The colony was initially monodomic and then occupied a second nest before it split into two independent colonies, indicating a gradual and opportunistic dependent foundation. After the fission event, the daughter colony had aggressive conflicts with the parental colony, resulting in the latter’s disappearance. Colony fission affected workers’ extra-nest behavior by increasing the frequency of rubbing the gaster against the substrate (which probably has a chemical marking function) and by decreasing the frequency of foraging during the split stage. After the fission event, the number of foragers was halved and foragers remained nearer to the nest during extra-nest activity. The spatial closeness of the parental and daughter colonies led to competition that caused the extinction or migration of the parental colony. Intraspecific competition was indicated by foraging directionality at the colony level, whereby areas of neighbor colonies were avoided; this directionality was stronger while both colonies coexisted.     

Excavation and architecture of Argentine ant nests

We used x-ray computed tomography to study the elaboration of nest structures in small sand-filled nest boxes by Argentine ant (Linepithema humile) colonies composed of 10, 100, and 1000 workers. The pattern of nest growth was consistent with a process of density-dependent stimulation of excavation, which subsided as nests grew and the density of digging stimuli declined. Thus, nest excavation would be auto-regulating, and final nest size should be adjusted to colony size. We found that excavation rates and final nest sizes increased with colony size, but were not tenfold greater in 1000-worker colonies than in 100-worker colonies. In the largest colonies, the internal surface area scaled allometrically with volume, so that more surface was obtained relative to volume excavated as the nest grew. Although the gross features of Argentine ant nests, such as total size, seem explicable by a simple, self-organized regulatory process, other features of the nest architecture will require further investigation. Received 3 March 2005; revised 26 April 2005; accepted 3 May 2005.     

Tree-ring based spring precipitation reconstruction in western Nepal Himalaya since AD 1840

Spring (March–June) precipitation has been reconstructed since AD 1840 for the Rara National Park (RNP), western Nepal Himalaya using Abies spectabilis tree-ring width. The reconstruction accounts for 35.8% of the total variance of the instrumental precipitation from 1958 to 2012 and captured distinct wet and dry variability. The longest wet periods occurred during 1850–1862, 1878–1886, 1909–1917, 1971–1984 and 2000–2008 while dry periods were usually shorter and occurred during 1873–1877, 1921–1923, 1925–1929, 1951–1956, 1958–1962 and 1994–1996. Spectral analysis of the reconstruction shows significant peaks at periodicity ranging 2.4–6.5 year, suggesting a covariation in inter-annual variability similar to that of El Niño-Southern Oscillation (ENSO). Spectral analysis of the reconstruction shows significant quasi–cyclic (2.4–3.4 year) and multidecadal (24.8–39.2 year) periodicity, suggesting a potential association with El Niño-Southern Oscillation (ENSO) and Atlantic Multidecadal Oscillation (AMO).     

The role of El Niño–Southern Oscillation in the dynamics of a savanna large herbivore population

Our understanding of large‐scale climatic phenomena and dynamics of large herbivore populations comes principally from research in northern regions with temperate, seasonal climate and animal communities with relatively low species diversity. To assess the generality of that perspective, we investigated effects of El Niño–Southern Oscillation (ENSO) on population dynamics of African buffalo Syncerus caffer inhabiting a semi‐arid savanna with variable rainfall. We used linear and nonlinear‐threshold models to investigate relationships between population parameters and explanatory variables affecting forage conditions (seasonal rainfall, Southern Oscillation Index [SOI]). El Niño‐related droughts in 1982–1983 and 1991–1992 were associated with strongly negative population change, a pattern expected to coincide with a decrease in normally high and constant adult survival. Consistent with that nonlinear pattern, we detected threshold relationships between wet‐season rainfall and population change. Juvenile recruitment was described best by linear relationships with dry‐season. Because ENSO operates primarily through wet‐season rainfall, whereas population dynamics were also related to dry‐season rainfall, SOI did not have the predictive ability of individual weather components.