Biomass and population structure of Constrictotermes cyphergaster (Silvestri) (Isoptera: termitidae) in the dry forest of caatinga, northeastern Brazil

Biomass and population structure of Constrictotermes cyphergaster (Silvestri) were studied in an area of dry forest of caatinga in the State of Paraiba, northeastern Brazil. Twelve nests of different sizes were randomly collected, being six during the dry season (November 2004 and 2005) and six during the wet season (March 2004). Soldier and worker populations varied between 4880 and 118800 individuals per nest. The ratio between soldiers and workers did not significantly vary between seasons. Biomass (measured as fresh weight) of individuals varied between 13.9 and 408.8 g per nest, and soldiers and workers had significantly greater biomass during the wet season. The estimated density of nests of C. cyphergaster was 59.0 +/- 22.53 active nests/ha. Quantitative data of the study colonies and data on the nest abundance showed that C. cyphergaster encompassed some 278.2 individuals/m(2), with approximately 0.9 g (fresh weight)/m(2). These data suggest that C. cyphergaster is an important consumer of vegetal matter and, therefore, an important species affecting the nutrient cycling and energy flow in the caatinga vegetation.     

Testing the importance of nest concealment: does timing matter?

ABSTRACT.   Nest concealment by vegetation is considered an important factor affecting predation rates for many passerines and, therefore, is frequently measured in studies examining nest predation. However, the time when concealment measurements are made may affect the results of such studies, particularly in highly seasonal ecosystems where characteristics of the vegetation later in the breeding period may differ considerably from those at the time of nest-site selection. We used artificial nests baited with quail ( Coturnix sp.) eggs in a highly seasonal tropical dry forest in Jalisco, western Mexico, to test the effects of seasonal change in concealment on nest predation. We placed 40 open-cup, artificial nests in shrubs at the end of the dry season and again at the beginning of the rainy season in 2007, and monitored the fate of the nests and the degree of concealment by vegetation during both periods. Nest concealment was significantly greater during the wet season than during the dry season. The percentage of nests predated was marginally higher during the dry (100%) than the wet (72.5%) season, and daily nest survival was lower during the dry than the wet season. Our results suggest that, in highly seasonal environments such as tropical dry forests, delayed measurement of nest concealment after nest completion rather than during nesting may constitute a significant source of error.     

Breeding ecology of the Clay-coloured Robin Turdus grayi in lowland Panama

The breeding ecology of Clay-coloured Robins Turdus grayi was studied in 1979 in the former Canal Zone of lowland Panama. Two study areas were chosen close together, Summit Gardens (27-3 ha), an ecological island of habitat suitable for Clay-coloured Robin surrounded by forest, and Morgan's Gardens (3–6 ha), a similar island surrounded by deforested areas and settlements. Eighty-three active nests were found and checked. The breeding season lasted from 2 March to 21 June. In Morgan's Gardens the first broods were raised in the dry season and second broods in the rainy season; in Summit Gardens most broods started at the beginning of the rainy season. In comparison to the closely related Blackbird T. merula in Poland, Clay-coloured Robins build nests on isolated trees or bushes, usually in more conspicuous sites (interpreted as an anti-predator adaptation) and on flexible, horizontal branches off the main trunk. Over 45% of broods were destroyed by predators but other factors causing brood loss were negligible. Nests built on palms were considerably safer. In the dry season the predation rate was low (5%) and increased during the course of the rainy season. Unlike Blackbirds, Clay-coloured Robin nestlings were given a lot of fruit; their diet was diversified. Starvation occurred in 60% of nests although usually only the youngest nestling died. Breeding density in Morgan's Gardens at 50 pairs per 10 ha was much higher than in Summit Gardens at 15>8 pairs per 10 ha. Breeding losses were lower, the nestlings were fed more fruit, the average nestling weight was lower and the production of fledglings per breeding pair was twice as high in Morgan's Gardens. It was concluded that a strategy of settling in a rather overpopulated place with hard foraging conditions but lower predation was better than settling in a area with a better food supply but higher predation.     

Nesting Behavior of <Emphasis Type="Italic">Gorilla gorilla diehli</Emphasis> at Kagwene Mountain,Cameroon: Implications for Assessing Group Size and Density

We recorded nesting data at 569 fresh night nest sites, comprising 7032 individual nests, of Cross River gorillas inhabiting the Kagwene Mountain in western Cameroon. The mean night nest group size was 12.4. Overall, 55% of night nests were constructed on the ground and 45% in trees. Significantly more arboreal nests were constructed in the wet season (69%), vs. the dry season (19%). Day nest construction was common at Kagwene (n = 260 nest sites, mean nest group size = 5.98) and we encountered significantly more day nest sites in the wet season. Nest site reuse was also common (35%), though not related to season. Our results of nesting habits concur with those from other western gorilla studies, in which rainfall influences arboreal nesting. However, we encountered wet season arboreal nesting, day nest construction, and overall nest site reuse more frequently than reported for other sites. Our observations have considerable implications when estimating group size and density using traditional nest count data. The gorillas at Kagwene inhabit the highest altitudinal range of all Cross River gorilla subpopulations and rainfall is also high; therefore other subpopulations may demonstrate different nesting characteristics. However, one should consider our findings when attempting to estimate Cross River gorilla density at other localities through nest site data.     

Nutritional function of replete workers in the pharaoh's ant, Monomorium pharaonis (L.)

Summary: Queens of the pharaoh's ant Monomorium pharaonis (L.), like several other ant species, feed on larval secretions as their main nourishment and their fecundity is positively correlated with the number of large larvae present in the nest. The surplus of secretions produced by larvae is stored in a temporary caste of replete workers, which comprises young workers who remain in the nest and store liquid nourishment. Repletes are characterised by a conspicuously large gaster, caused by large amounts of liquid food stored in the crop, from which it may be regurgitated and distributed among colony members. In this study, repletes of pharaoh's ants were demonstrated to be functioning as buffers, smoothing fluctuations in availability of high quality food to the reproductive queens when larvae are scarce or missing, thus temporarily keeping up the egg production of queens.¶In undisturbed two-queen colonies with 20 large worker larvae and 30 workers (15 young and 15 old workers), approximately 10 repletes developed (one replete per two larvae). Development of older workers into repletes, when some or all repletes had been removed from the colonies, demonstrated that their temporal polyethism exhibits great plasticity in this trait.¶This study confirmed that, in pharaoh's ants, the regulation of fecundity depends not only on the food flow to the queen from larvae or from repletes but also on an unknown larval stimulus.¶The term crop repletes is suggested for replete workers which use their crop to store nourishment, as opposed to fat-body repletes, which store nourishment in their fat body.¶The presence of brood tending crop repletes in nests in several European ant species of Leptothorax, Myrmica, and Lasius, show that repletism is a common trait in ants, and that it may play an important role in regulation of nutrition in ant colonies, as demonstrated in Monomorium pharaonis.     

Colony structure and nest characteristics of European wasps, Vespula germanica (F.) (Hymenoptera: Vespidae), in Victoria, Australia

Abstract European wasps, Vespula germanica , are common across southern and south-eastern Australia and have a negative impact upon urban areas, primary industries, and natural ecosystems. Aspects of colony structure and nest characteristics are examined for nests located in the ground and collected from urban and rural sites in Victoria during two summer−autumn field seasons (1996 and 2001). On average, nests were located 28 cm beneath the surface (range 5−58 cm). The average number of combs in the nest and the total area of the nests increased from early February to late May. In addition, the proportion of cells used to produce workers and different life stages (larvae, pupae) also varied throughout the season; being consistent with studies from New Zealand. No differences in colony structure or nest character­istics were detected between urban and rural nests.     

Nest relocation and high mortality rate in a Neotropical social wasp: Impact of an exceptionally rainy La Niña year

After noting the forecast of a La Niña episode, associated with heavy rainfall in French Guiana, we monitored the fate of wasp nests before and during the 2006 short rainy season. The population of the most abundant epiponine wasp species, Polybia bistriata, decreased dramatically during the short rainy season (60.6% of the nests disappeared) then remained low for at least 18 months. Colonies that survived moved from the shelter of large, low leaves (a situation well adapted to the previous dry season) of the most frequent substrate tree, Clusia grandiflora (Clusiaceae), to upper leaves, better ventilated and whose orientation provides good protection from the rain. Therefore, the possibility of moving the nest higher during the first rains following the dry season seems very adaptive as colonies that do not do so are eliminated during the La Niña years, whose frequency will increase with global climate change.     

Orientation and foraging movements in a patchy environment by the ant Serrastruma lujae (formicidae-myrmicinae)

Serrastruma lujae ants individually search for collembolans in the leaf litter of humid tropical forests. During the dry season, collembolans aggregate in wet patches randomly scattered in the dry litter where numerous single workers come hunting from their nest. We simulated this situation in the laboratory, and observed that workers seem to be able to use the humidity gradient direction to efficiently orient themselves towards a wet patch. Once the patch has been reached, they exhibit area-concentrated searching,consisting, in particular, of adopting a high sinuosity and a low speed. After capturing a collembolan, the ants return to their nest along nearly straight paths. This ability may rely on a spatial memory of the nest location by means of a path-integration process. In the absence of prey, however, various behaviours were observed after an unsuccessful search. Comparisons between these data and the results obtained with a homogeneously wet environment simulating the rainy season situation showed that these ants do not simply respond to the humidity level but are also sensitive to the degree of patchiness of their environment. They can therefore be said to be able to adapt suitably to the considerable climatic changes they encounter during the year.     

Leaf-cutting ant nests support less dense and impoverished seed assemblages in a human-modified Caatinga dry forest

Regenerating forests make up an increasingly large portion of tropical landscapes worldwide and regeneration dynamics may be influenced by leaf-cutting ants (LCA), which proliferate in disturbed areas and collect seeds for fungus culturing. Here, we investigate how LCA influences seed fate in human-modified areas of Caatinga dry forest. We evaluate the seed deposition and predation on Atta opaciceps nests, foraging habitat surrounding nest and control habitat away of nest influence of 15 colonies located along a forest cover gradient during the rainy and dry seasons. For each habitat, four 50-cm² plots were established and all seeds on the soil surface were collected along 1 year. We recorded 13,628 seeds distributed among 47 species and 36.57% of the total seeds did not show any sign of predation. Nest mound habitats supported low-density and species-poor seed assemblages, which were taxonomically distinct from the control habitats. These effects only occurred in the rainy season. The proportion of undamaged seeds were similar across the habitats. While forest cover did not influence seed assemblage in terms of species richness or seed predation, it did interact with habitat type via increments in seed abundance as forest cover increased across the nests. Forest cover also affected seed composition, but only in the rainy season. These results indicate that LCA decrease seed deposition in areas under their influence, particularly on the nest mounds. As LCA profit from human disturbance in the Caatinga, their role as seed ‘sinks’ should be enhanced in disturbed Caatinga patches, particularly during the rainy season, when most of the plant recruitment occurs. Our findings reinforce the importance of LCA as drivers of forest dynamics and resilience in human-modified landscapes.     

Size and composition of swarming colonies in Provespa anomala (Hymenoptera, Vespidae), a nocturnal social wasp

Summary: Ninety-eight nests of various growing stages of Provespa anomala were found in the lowlands of Sumatra, Indonesia, from August to January. Its colony cycle is considered to be annual, with nests built throughout the year. There were two types of early nests before the emergence of workers, one with a worker number of less than 63 and the other of more than 231. The former were new nests, each containing a new queen and were built by reproductive swarming, whereas each of the latter was possibly re-built by an old queen and an absconding swarm. Ten swarming colonies were attracted by an oil-lamp light; these consisted of a copulated queen with immature oocytes in the ovary and 55 workers on average. No males, or workers stylopized by Xenos provesparum were observed either in colonies before worker emergence or in swarms coming flying into the light. Differences between swarming in Provespa, polygyny and nest relocation in Vespa, and those in swarm-founding Polistinae are discussed.     

Colony size,density and distribution of the leaf-cutting ant,Acromyrmex octospinosus (Reich) in cultivated fields

• 1 Fields of citrus, cacao and rubber in Trinidad were surveyed to measure the number and density of nests of Acromyrmex octospinosus. The greatest density (=153 nests/ha) was in an undisturbed field of young cacao; in established crops density ranged from 3–36 nests/ha.
• 2 Mounds of new nests appeared throughout the year, but most often 4–10 months after the main nuptial flights. Nests reached maximum size, with up to 17 holes, about three years after foundation.
• 3 The ratio of workers to brood was between 5 and 9: 1 for most of the year but it increased to 27: 1 as the sexuals developed. A medium-large colony produced 200–300 queens and males/year; the largest single nest contained about 14,000 individuals.
• 4 The average intake of leaf fragments into laboratory nests was 1 fragment/6.5 individuals. It increased to 1 fragment/2.1 individuals when sexuals were present. Foragers collecting from fields of established cacao preferred flowers to leaves.
• 5 In fields with crops planted on cambered beds, nests were concentrated on the dry edges of drains in the dry season, but they were moved to drier ground in the wet season. Nests were aggregated in 13 of the 16 fields examined, the remaining three fields were exceptionally well drained.
• 6 In newly planted cacao an estimated 6—17% of plants were defoliated and destroyed. In established cacao ants collected about 3000 flowers/ha each day. Laboratory data suggest that ants could defoliate about 25 three-year old citrus trees in a year.

     

Intra-caste size differences between two social forms of the southern yellowjacket, Vespula squamosa (Hymenoptera, Vespidae)

Summary: Changes in intraspecific social organization are of particular interest to sociobiologists, because an understanding of the genetic and ecological determinants of different social forms bears on the origins of sociality and mating isolation. The Southern Yellowjacket, Vespula squamosa (Drury), occurs as both polygyne and single queen nests. This study examined intra-caste size differences between both social forms of nests. Four polygyne and 13 single queen nests were collected from counties in Florida and Georgia. All single queen nests were one season old, whereas polygyne nests were at least 2 years old. The latter had significantly more workers per nest (p < 0.005), but mean values varied by over 50-fold. Workers and gynes from each social form were compared for six measures of body size: weight, wing length, femur length, thorax length, thorax width and head width. Correlation coefficients for pairs of all traits were highest between head width and both measures of thorax size (r > 0.72), whereas the lowest positive correlations were obtained between weight and all other measures of size (r < 0.64). Gynes of both social forms differed significantly in weight (p < 0.001) and thorax length (p < 0.04), whereas workers differed significantly for all six measures of size (p < 0.04 to p < 0.001).     

Nest architecture of the ant <Emphasis Type="Italic">Formica pallidefulva</Emphasis>: structure,costs and rules of excavation

Summary The architecture of underground ant nests was studied in the ant Formica pallidefulva. These ants build shallow (30–45 cm deep) nests, which consist of more or less vertical shafts that bear chambers. Shafts are modular units of nest growth; nests are enlarged by adding more shafts or extending previously existing ones. The nests are top-heavy, their volume declining exponentially with depth. The total volume of the nest is strongly correlated with the number of worker occupying the nest (R² = 0.87). Some of the rules and templates used by workers for nest construction were determined: (a) chambers are formed in the direction of the tunnels leading up to them, (b) the amount of soil excavated per unit time increases with soil temperature and moisture content. The amount of time and energy required to construct a typical nest were approximated using digging ability parameters determined in the lab. We estimate that if a colony was to move twice a year, it would expend around 20% of its energy intake and at least 6% of its worker time on nest excavation.Received 16 December 2002; revised 10 July 2003; accepted 23 July 2003.     

Breeding ecology of Kori Bustard Ardeotis kori strunthiunculus in the Serengeti National Park

The breeding ecology of the Kori Bustard Ardeotis kori strunthiunculus was studied in the plains of the Serengeti National Park, Tanzania in 2014 and 2015. Random transects were used to search for male courtship displays, nests, chicks and subadults. GPS satellite collars were used to locate nesting females. Linear regression analyses and post hoc tests were used to determine the predictors that contributed most to the variation of the dependent variables (courtship display, nest, chicks and subadults). The results indicate that courtship behaviour peaks during the short dry and short rainy season before the peaks in nests and chicks. The highest nest frequency was found in short grass habitats. Female Kori Bustard may undergo repeated nestings within a single breeding season. The adult sex ratio was female skewed during the breeding season. The Kori Bustard breeding season in the Serengeti plains is relatively long, lasting for almost nine months, and taking place during all seasons except for the long dry season. We recommend that management authorities conduct assessments of Kori Bustard recruitment as well as habitat suitability in the Serengeti ecosystem to develop future conservation strategies.     

Leaf-litter and changing nutrient levels in a seasonally dry tropical hardwood forest,Belize, C.A.

Summary Total above ground plant biomass in a 45 year old seasonally dry tropical hardwood forest was estimated to be approximately 56,000 kg/ha oven dry weight. Nutrients immobilized in the standing vegetation were: N, 203 kg/ha; P, 24 kg/ha; K, 234 kg/ha; Ca, 195 kg/ha; Mg, 47 kg/ha; Na, 9 kg/ha; Mn, 1 kg/ha; Cu, 0.5 kg/ha; Zn, 3 kg/ha; Fe, 4 kg/ha. Total nutrients returned each year through the litter were: N, 156 kg/ha; P, 9 kg/ha; K, 59 kg/ha; Ca, 373 kg/ha; Mg, 32 kg/ha; Na, 5 kg/ha; Mn, 1 kg/ha; Al, 21 kg/ha; Zn, 0.3 kg/ha; Fe, 9 kg/ha. Half of the nutrients immobilized in the standing vegetation were found in the leaves and are returned annually to the soil. Although litter fall is interrupted during the year, the mean nutrient content of the litter was high –5.2%.A decomposition rate of 0.48 percent per day was considered high for a seasonally dry tropical hardwood forest. Fluctuations in soil nutrient levels showed a sharp increase at the start of the rainy season. Later during the dry season nutrient levels decreased to concentrations similar to what they were just prior to the rainy season. Soil organic matter levels were very high –20% in the top 12 cm.     

Sleeping site selection by savanna chimpanzees in Ugalla,Tanzania

We examined sleeping site selection by chimpanzees (Pan troglodytes) in the Ugalla savanna woodland area, western Tanzania, from 1994 to 2012. We established 488 km of line transects and recorded 379 chimpanzee beds within 30 m perpendicular to the transects. Comparisons between 60 × 60 m² quadrats containing new and recent beds and the remaining quadrats without beds along the transects indicated that evergreen forests accounted for disproportionately more area in quadrats with beds than in those without beds during both the dry and rainy seasons. In Ugalla, chimpanzees coexist with lions (Panthera leo) and leopards (Panthera pardus). They may sleep in forests to reduce predation risk by these carnivores, as trees are dense and the canopy is high and closed. The angle of slope was steeper in quadrats containing beds than in those without beds during the dry season, whereas the angle was less steep in quadrats with beds than in those without beds during the rainy season. Additionally, fewer beds were found further from forests. The distance between beds and forests during the dry season was shorter than that during the rainy season. Chimpanzees may sleep in or near forests and on slopes because of water pools in the valley forests along the slopes during the dry season. Quadrats with beds were at slightly higher altitude than those without beds during the rainy season; however, the difference was not significant during the dry season. The number of beds found in or close to feeding trees was not related to the fruiting period. Sleeping site selection by chimpanzees may be affected by predation pressure and water availability in the savanna woodland area.     

The seasonal pattern and distribution of green turtle (Chelonia mydas) nesting activity on Aldabra Atoll, Indian Ocean

Green turtles nest all year round on Aldabra, but nesting activity was found to be concentrated during the monsoon season (late November-April) rather than the dry season as previously reported. More trial nests and emergences were made during the dry season. This was considered to be the result of difficulties in nesting during this time of the year rather than to more females attempting to nest, because fewer nests were dug during this season. The number of beaches being used by the turtles has apparently increased but no clear reason could be provided for the varying levels of use of different beaches.     

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.     

Nest spacing and architecture, and swarming of males of Dinoponera quadriceps (Hymenoptera, Formicidae) in a remnant of the Atlantic forest in Northeast Brazil.

Dinoponera quadriceps is a queenless neotropical ponerinae ant. Nest spacing and abundance were investigated in a remnant of the Atlantic forest in Northeast Brazil. Males were captured with a light trap between August 1994 and July 1996. Nest density varied from 15 to 40 ha(-1). An overdispersion of nests suggests that the intraspecific competition may be an important factor regulating their spatial arrangement. Territory size was correlated with worker population size of the colonies. The nests had up to 16 chambers, with variations in their architecture closely related to habitat diversification. Populations varied from 12 to 97 adult workers per nest, with a mean density of 1,618 workers ha(-1) and a live biomass of 461 g ha(-1) (n = 13 nests). Males swarm continually throughout almost all months of the year, suggesting that production and swarming are more influenced by mechanisms that regulate the sexual activity of workers than by climatic factors.     

Effect of drought on leaf gland secretion of the mangrove Avicennia germinans L.

This study assessed the effects of salinity changes over space and time upon leaf gland secretion in Avicennia germinans trees growing naturally in an area featuring markedly seasonal rainfall. Soil ? (, soil N MPa) during the wet season was -0.95ǂ.05 and -2.12ǂ.08 at low and high salinity sites, respectively. During the dry season, these values decreased to -3.24ǂ.09 at low salinity and to -5.75ǂ.06 at high salinity. Consequently, predawn and midday plant water potential were lowered during drought at both sites. The rates of secretion (mmol m^-2 h^-1 ) increased during drought from 0.91ǂ.12 during the wet season to 1.93ǂ.12 at low salinity, and from 1.69ǂ.12 during the wet season to 2.81ǂ.15 at high salinity. Conversely, stomatal conductance (g_s) was lowered by both salinity and drought. As xylem osmolality increased during drought, secretion tended to rise exponentially, and g_s decayed hyperbolically. Thus, a trade-off is obtained between enhancement in salt secretion and control of water loss suggested by g_s.