Abundance Of Insect Prey Research Articles

The Consumption and Diversity Variation Responses of Agricultural Pests and Their Dietary Niche Differentiation in Insectivorous Bats.

Insectivorous bats are generalist predators and can flexibly respond to fluctuations in the distribution and abundance of insect prey. To better understand the effects of bats on arthropod pests, the types of pests eaten by bats and the response of bats to insect prey need to be determined. In this study, we performed DNA metabarcoding to examine prey composition and pest diversity in the diets of four insectivorous species of bats (Hipposideros armiger, Taphozous melanopogon, Aselliscus stoliczkanus, and Miniopterus fuliginosus). We evaluated the correlation between bat activity and insect resources and assessed dietary niche similarity and niche breadth among species and factors that influence prey consumption in bats. We found that the diets of these bats included arthropods from 23 orders and 200 families, dominated by Lepidoptera, Coleoptera, and Diptera. The proportion of agricultural pests in the diet of each of the four species of bats exceeded 40% and comprised 713 agricultural pests, including those that caused severe economic losses. Bats responded to the availability of insects. For example, a higher abundance of insects, especially Lepidoptera, and a higher insect diversity led to an increase in the duration of bat activity. In areas with more abundant insects, the number of bat passes also increased. The dietary composition, diversity, and niches differed among species and were particularly significant between H. armiger and T. melanopogon; the dietary niche width was the greatest in A. stoliczkanus and the narrowest in H. armiger. The diet of bats was correlated with their morphological and echolocation traits. Larger bats preyed more on insects in the order Coleoptera, whereas the proportion of bats consuming insects in the order Lepidoptera increased as the body size decreased. Bats that emitted echolocation calls with a high peak frequency and duration preyed more on insects in the order Mantodea. Our results suggest that dietary niche differentiation promotes the coexistence of different bat species and increases the ability of bats to consume insect prey and agricultural pests. Our findings provide greater insights into the role of bats that prey on agricultural pests and highlight the importance of combining bat conservation with integrated pest management.

Decomposing an elevational gradient in predation by insectivorous birds

AbstractInsectivorous birds have ecologically important effects on prey abundance, behavior, and evolution, and through top‐down control, birds indirectly reduce herbivory and promote plant growth. While several studies sought to characterize biogeographic patterns in top‐down control by birds, variation in bird predation along elevational gradients is not well characterized in terms of both its commonness and the mechanisms underlying such variation. Here, we characterized variation in bird predation along a 700‐m montane elevation gradient using artificial clay caterpillars, assessing the roles of variation in aridity, other elevational effects not associated with aridity (e.g., most notably growing season length), and bird abundance and diversity. Multivariate models revealed increasing attack rates with aridity (when controlling for the effects of elevation) and elevation (when controlling for aridity). Because aridity declines with elevation, elevational patterns were not detectable in a univariate analysis. Bird abundance (but not diversity) decreased with elevation (but not aridity) and did not provide an explanation for our results, suggesting that the underlying mechanisms were behaviorally based. We speculate that the declining abundance of insect prey with elevation and aridity leads to increased bird foraging efforts and thus the likelihood of attacking clay caterpillars. If widespread, these dynamics have important consequences for both the interpretation of predation bioassays generally and our understanding of the multivariate drivers of variation in top‐down control by predators and predation risks experienced by prey.

Ants offset bottom-up control of spiders in Amazonian savanna trees

Community trophic structure is shaped by concurrent bottom-up (resources) and top-down effects (predators), but the extent to which they interact remains uncertain. The Exploitation Ecosystems Hypothesis predicts that predators should offset increases in herbivore abundance with plant productivity, which is supported by data. However, the extent to which interactions within trophic levels (e.g. competition, intraguild predation) have similar effects is less clear. Ants and spiders are abundant in vegetation and consume similar arthropod prey (occasionally each other) and plant exudates, with ants generally showing competitive dominance over spiders. We tested whether ants could shape the trophic structure of tree-dwelling macroarthropod communities by offsetting increases in spider abundance with insect prey. We performed three surveys of the macroarthropod community of 97 trees from two sites in the savanna of Northern Amazonia. Together, ants and spiders represented 74% of the sampled individuals per tree. Insect prey abundance increased with tree crown volume and crown flower cover, consistent with bottom-up limitation. Likewise, both ants and spiders increased with insect prey abundance, with ant abundance also varying with tree species, suggesting reliance on both animal and plant resources. However, as predicted, the positive relationship between spider abundance and insect prey abundance disappeared as ant abundance increased. Our results suggest that agonistic interactions within trophic levels can strongly shape community structure and size by modifying bottom-up effects as much as interactions across trophic levels.

Bat Activity in Organic Rice Fields Is Higher Than in Conventional Fields in Landscapes of Intermediate Complexity

The extent to which organic farming can support biodiversity has been extensively studied. However, most of the research has been conducted on organic farms in temperate regions, with the focus mainly being on birds, insects, and plants and rarely on insectivorous bats, especially in Southeast Asia. We studied pairs of matched organic and conventional rice fields along a gradient of landscape complexity in the Songkhla Lake Basin and conducted acoustic surveys using bat detectors to analyze the influence of farming system and landscape characteristics on bat activity and prey availability. We also tested the “intermediate landscape complexity” hypothesis, which states that local conservation efforts are most effective in landscapes of intermediate complexity compared to extremely simple or extremely complex landscapes. We detected no difference in bat species richness, total bat activity, feeding activity, and insect prey abundance between organic fields and conventional fields. Even though organic farming did not increase bat activity on its own, it was most beneficial to bat activity in landscapes of intermediate complexity. Our findings suggest that landscape traits contribute more to bat activity than farm management and that insectivorous bats have species- and guild-specific responses to various landscape contexts. We also found that disturbance caused by tropical storms negatively impacts the activity of insectivorous bat.

The importance of grassland patches and their associated rainforest ecotones to insectivorous bats in a fire-managed tropical landscape

Abstract ContextEcotones are recognised globally as areas of high biodiversity, yet relatively little is known about how fauna use different types of ecotone. Tropical rainforest–grassland ecotones are shaped through particular fire regimes, creating both gradual and abrupt ecotones. Insectivorous bats contribute considerably to mammalian diversity, and their capacity for flight allows them to use ecotones in a three-dimensional way, making them an informative faunal group for evaluating ecotone use. AimsTo critically evaluate how insectivorous bats use gradual and abrupt ecotones between rainforest and grassland habitats. MethodsBat detectors were placed every 50m, along 200-m transects, through five gradual and five abrupt rainforest–grassland ecotones. The activity of all insectivorous bats, as well as open, edge–open and closed foraging guilds (defined by echolocation call type), was compared among grassland and rainforest habitats, gradual and abrupt ecotones and positions across the ecotones. Key resultsMean total bat activity, mean open and edge–open foraging guild activity were significantly higher in grassland positions, followed by the edge, and were lowest in the rainforest. Closed foraging guild bats showed no preference for either habitats, but had significantly higher activity in gradual compared with abrupt ecotones. Mean activity of edge–open foraging guild bats was affected strongly by the interaction between ecotone type and position along the ecotone. Gradual ecotones had a more even proportion of all three bat foraging guilds along the ecotone compared with abrupt ecotones. Most of these findings were likely driven by the structural complexity of gradual ecotones that fulfilled microhabitat requirements for all three foraging guilds, but may also have been influenced by insect prey abundance. ConclusionsThe present study demonstrated the importance of grassland patches in a tropical, rainforest landscape, and of gradual rainforest–grassland ecotones for insectivorous bats. Gradual ecotones promote complex habitat mosaics to allow closed foraging guild species to take advantage of food resources provided by grasslands, and provide all bats proximity to potential roosting and foraging sites. ImplicationsThe data clearly suggest that a suitable fire regime should be used to maintain current grassland patches within a rainforest landscape, and to promote gradual ecotones for use by insectivorous bats.

Agroecological farming practices promote bats

Intensive agriculture is a major driver of biodiversity loss, and a critical part of creating sustainable food systems is finding ways to balance production and conservation. While practices characteristic of agricultural intensification tend to erode biodiversity, agroecological farming practices can potentially support biodiversity and enhance pest suppression services. Bats are important predators of agricultural pests, yet little is known about how prescriptive management practices can be used to support bats and their associated pest-suppression services. We investigate how bats use natural habitat and conventional and organic farms in an agricultural landscape, ask which on-farm management practices may benefit bats, and examine how these management practices influence bats by mediating changes in habitat quality. We conducted acoustic surveys at 54 sites in the California Central Coast Region, a productive region with high ecological and economic value. We found higher bat activity in natural habitat compared to farms for total bat activity and clutter-adapted, but not open space bats, and slightly higher bat diversity in natural habitat compared to conventional farms. We found no effect of habitat type on species richness and a weak effect of habitat type on bat diversity, although bat community composition differed significantly between natural habitat and farms. Crop diversification increased the activity of all bat species and clutter-adapted, but not open space bats, regardless of the amount of semi-natural habitat surrounding farms. Both crop diversification and less frequent pesticide applications increased prey biomass, and the activity of clutter-adapted bats was positively correlated with greater Lepidoptera biomass. We suggest that improving habitat quality (increasing abundance of insect prey) through vegetative diversification and/or less frequent pesticide applications offers flexible management options to growers by considering both bat ecology and the constraints of regional agricultural management practices.

Early Cretaceous greenhouse pumped higher taxa diversification in spiders

The Cretaceous experienced one of the most remarkable greenhouse periods in geological history. During this time, ecosystem reorganization significantly impacted the diversification of many groups of organisms. The rise of angiosperms marked a major biome turnover. Notwithstanding, relatively little remains known about how the Cretaceous global ecosystem impacted the evolution of spiders, which constitute one of the most abundant groups of predators. Herein, we evaluate the transcriptomes of 91 taxa representing more than half of the spider families. We add 23 newly sequenced taxa to the existing database to obtain a robust phylogenomic assessment. Phylogenetic reconstructions using different datasets and methods obtain novel placements of some groups, especially in the Synspermiata and the group having a retrolateral tibial apophysis (RTA). Molecular analyses indicate an expansion of the RTA clade at the Early Cretaceous with a hunting predatory strategy shift. Fossil analyses show a 7-fold increase of diversification rate at the same period, but this likely owes to the first occurrence of spiders in amber deposit. Additional analyses of fossil abundance show an accumulation of spider lineages in the Early Cretaceous. We speculate that the establishment of a warm greenhouse climate pumped the diversification of spiders, in particular among webless forms tracking the abundance of insect prey. Our study offers a new pathway for future investigations of spider phylogeny and diversification.

Bat activity in rice paddies: Organic and conventional farms compared to unmanaged habitat

Many bat species in Europe have suffered severe population declines during the 20th century, and the main drivers of this decline is likely the loss of foraging habitats at local and landscape levels due to farmland intensification, which also poses a serious threat to biodiversity and affects species interactions and ecosystem functions. Several studies reported positive effects of organic compared to conventional farming on bat populations and on nocturnal insect prey abundance. We registered the flight and feeding activity of 12 bat species in rice paddies in Northwestern Italy to test the effect of wetland farm management and agricultural intensification on bats habitat use. Our study evaluated the different ecological roles of organic vs conventional rice farms and natural wetlands in conservation of bat species. For the 12 species under study, flying activity was recorded in all three land management types. Only the genus Pipistrellus hunted in conventional and organic farms. Myotis sp, Eptesicus serotinus and Hypsugo savii were recorded hunting only in natural wetlands. Rinolophus ferrumequinum was detected only in natural wetlands. Bats fed in organic farms as well as in natural wetlands, whereas they were unlikely to forage in conventional farms. Conventional rice paddies do not provide ideal foraging sites for bats, likely due to the widespread use of pesticides, water management, and intensive weed control on embankments. Organic rice paddies, due to the less aggressive management, appear to have a higher habitat quality compared to conventional ones, and are therefore more suitable for feeding activities, possibly due to the greater availability of prey. Furthermore, while the limited ecological value of conventional farms for bat conservation is confirmed in this research for rice paddies, further effort should be made to preserve natural wetlands. We argued that farmland practices that maximise organic farming and ensure the conservation of natural wetlands, in accordance with the recent reform of the Common Agricultural Policy, are essential for bat conservation in agricultural environments and, more generally, to preserve biodiversity.

Tree Swallow (Tachycineta bicolor) foraging responses to agricultural land use and abundance of insect prey

Throughout North America, many species of aerial insectivorous birds have exhibited steep declines. The timing of these declines coincides with changes in agriculture, perhaps signaling a causal link. Increased agrochemical use, wetland drainage, and cropping intensity may indirectly influence insectivores by reducing the abundance of insect prey. Our objective was to determine whether changes in insect abundance and biomass on agricultural landscapes in the Canadian Prairies influence the foraging behaviour of breeding Tree Swallows (Tachycineta bicolor (Vieillot, 1808)). Swallows were studied at five sites with varying levels of agricultural intensity in Saskatchewan, where insect abundance and biomass were monitored daily with passive aerial samplers. Radio-frequency identification (RFID) technology was employed at Tree Swallow nest boxes to investigate adult foraging behaviour. Foraging rates (number of nest visits/h) were slightly higher on agricultural sites than at grassland sites, and were positively related to daily insect biomass and nestling age. Tree Swallows, especially males, breeding at agricultural sites spent more time away from the nest box, presumably foraging, resulting in reduced nest attentiveness. RFID technology provides an effective technique to measure behaviour in birds and these findings suggest mechanisms by which prey abundance and agricultural land use may affect declining aerial insectivorous bird populations.

Polychlorinated biphenyls (PCBs): impact on bat activity and foraging behaviour along the upper Hudson River, New York

Sediments of the upper Hudson River, New York, USA, contain polychlorinated biphenyls (PCBs). Consequently, elevated levels of PCBs have been found in the tissues of bats and their insect prey along this region. However, it is not clear whether bat activity and foraging behaviour have been affected. To assess possible effects of PCBs on bat activity and foraging behaviour, we measured the activity of little brown bats (Myotis lucifugus (LeConte, 1831)) and hoary bats (Lasiurus cinereus (Palisot de Beauvois, 1796)) along the upper Hudson River, as well as abundance of insect prey at the same locations. We also measured foraging duration and distances travelled by radio-tagged M. lucifugus. We found that bat activity and insect abundance did not differ with PCB concentration. We did, however, find that foraging behaviour along the Hudson River differed from a control site. Specifically, M. lucifugus foraging along PCB-contaminated areas of the Hudson River travelled shorter distances from their roosts and spent less time foraging than bats at an uncontaminated site. Our results show that while bats roost and forage in areas historically exposed to PCBs, this exposure has not adversely affected bat activity, foraging behaviour, or abundance of insect prey.

Bat response to prescribed fire and overstory thinning in hardwood forest on the Cumberland Plateau, Tennessee

Across the Southeastern U.S., including the Cumberland Plateau of Tennessee, prescribed fire and overstory thinning are being used to restore areas of closed-canopy hardwood forest to open woodland and savanna. We used acoustic recording of bat echolocation call sequences to examine bat activity (relative use of an area for foraging) in hardwood forest stands subject to 4 prescribed fire and residual basal area treatments (spring prescribed fire with woodland [SpW] and savanna [SpS] residual basal areas, and fall prescribed fire with woodland [FaW] and savanna [FaS]) basal areas, as well as untreated controls, during summer of 2013 and 2014. When possible, we classified recorded echolocation call sequences to species using automated identification software (Sonobat™ 3.1.4, SonoBat™ Inc., Arcata, California). To minimize errors in species classification of recorded bat passes, we combined similar species in groups based on call characteristics prior to conducting analyses. Total bat activity (P⩽0.001), as well as LABO/NYHU (eastern red bat [Lasiurus borealis] and evening bat [Nycticeius humeralis]; P=0.001), EPFU/LANO (big brown bat [Eptesicus fuscus] and silver-haired bat [Lasionycteris noctivagans]; P⩽0.001), PESU (tricolored bat [Perimyotis subflavus]; P=0.001), and LACI (hoary bat [Lasiurus cinereus]; P=0.005) activity was generally higher in SpS and FaS stands, where overstory basal area was lower, than in control, SpW, and FaW stands, where overstory basal area was higher (P⩽0.001). Our results suggest these treatments reduce clutter (physical obstructions to flight and foraging including foliage, branches, and stems), leading to improved foraging conditions for bats, particularly larger bodied species with lower call frequencies that are adapted to fly and forage in open conditions. We found no evidence nocturnal flying insect prey abundance or biomass influenced activity of bats in treatment stands, indicating clutter is more important than prey availability in determining habitat use by bats in this system. Our study provides support for continued use of prescribed fire and overstory thinning to restore hardwood forest to woodland and savanna and as a strategy to maintain and enhance habitat for forest bats in the Southeastern U.S.

Bat Activity at Woodland/Farmland Interfaces in Central Delaware

Abstract Bats vary their activity with different features of habitat, resource availability, predation risk, and other factors. Agricultural fields may provide an abundance of insect prey, but are also risky habitats due to their exposure. How bats use mixed landscapes is important information for biologists, as increasing development affects the amount of suitable habitat and impacts bat populations in the region. Using acoustic recording, we monitored relative bat activity in open areas and edges of the woodland/farmland interface of agricultural fields in Kent County, DE. We examined bat activity among different sites, in openings versus edges, among crop types, relative to nearby forest fragment size and shape, and under different weather conditions. Bat activity was significantly higher along edges than in the open in the agricultural fields for passes/night, but we found no differences among crop types or sites and no interaction effects. We also found no effect of size or amount of edge of a fragme...

Seasonal variation in the trophic structure of a spatial prey subsidy linking aquatic and terrestrial food webs: adult aquatic insects

Research over the past decade has established spatial resource subsidies as important determinants of food web dynamics. However, most empirical studies have considered the role of subsidies only in terms of magnitude, ignoring an important property of subsidies that may affect their impact in recipient food webs: the trophic structure of the subsidy relative to in situ resources. This may be especially important when subsidies are composed of organisms, as opposed to nutrient subsidies, because the trophic position of subsidy organisms may differ from in situ prey. I explored the relative magnitude and trophic structure of a cross-habitat prey subsidy, adult aquatic insects, in terrestrial habitats along three streams in the south–central United States. Overall, adult aquatic insects contributed more than one-third of potential insect prey abundance and biomass to the terrestrial habitat. This contribution peaked along a permanent spring stream, reaching as high as 94% of abundance and 86% of biomass in winter. Trophic structure of adult aquatic and terrestrial insects differed. Nearly all adult aquatic insects were non-consumers as adults, whereas all but one taxon of terrestrial insects were consumers. Such a difference created a strong relationship between the relative contribution of the prey subsidy and the trophic structure of the prey assemblage: as the proportion of adult aquatic insects increased, the proportion of consumers in the prey assemblage declined. Specific effects varied seasonally and with distance from the stream as the taxonomic composition of the subsidy changed, but general patterns were consistent. These findings show that adult aquatic insect subsidies to riparian food webs not only elevate prey availability, but also alter the trophic structure of the entire winged insect prey assemblage.

Influence of Vegetation on Bat Use of Riparian Areas at Multiple Spatial Scales

ABSTRACT Research on habitat use by bats typically occurs at a single fine spatial scale, despite recent work demonstrating the importance of considering multiple spatial scales when investigating vertebrate habitat selection. We assessed bat use of 118 stream reaches located throughout the Oregon Coast Range, USA, and measured vegetation characteristics at 3 spatial scales surrounding each of these locations. We used an information‐theoretic approach to determine vegetation characteristics most closely related to bat activity and a multilevel modeling approach to evaluate variation in bat activity at different spatial scales. Characteristics of vegetation at the finest spatial scale explained more variation in bat activity than did characteristics of vegetation at broader spatial scales, suggesting that fine‐scale anthropogenic or natural disturbance events that alter cover of shrubs or trees in riparian areas are likely to influence bat habitat use. The influence of vegetation on activity varied by species of bat and appeared to operate more strongly through constraints imposed by vegetation architecture than through influences on abundance of insect prey. This diversity of responses to vegetation characteristics among bat species suggests that the best strategy for biodiversity conservation over broad spatial scales is maintenance or creation of a diversity of riparian vegetation conditions. We recommend that land managers planning to manipulate riparian vegetation strive to create diversity in shrub coverage, canopy coverage, and open space above the stream channel to promote foraging habitat for all species.

Bat activity in relation to fire and fire surrogate treatments in southern pine stands

Forest managers often use thinning and prescribed burning to reduce the risk of wildfire and insect outbreaks. Because thinning and burning alter the structure of forest stands and may affect insect prey abundance, they may change the suitability of stands for bats. Our objective was to test the effects of thinning and burning on bat foraging and commuting activity in pine stands in the Clemson Experimental Forest in the Piedmont of South Carolina. We also tested whether vertical use of stands varied with treatment and whether activity of three common species varied among treatments. Twelve stands in the Clemson Experimental Forest dominated by loblolly ( Pinus taeda) and shortleaf ( P. echinata) pine and at least 14 ha in size were selected and three replicates of four treatments were installed. The treatments were: (1) prescribed burning (Burn), (2) thinning to 18 m 2/ha (Thin), (3) thinning to 18 m 2/ha followed by prescribed burning (Thin&Burn) and (4) no treatment (Control). Bat activity was sampled with AnabatII bat detectors May–August 2001 and 2002. Big brown bats ( Eptesicus fuscus), eastern red bats ( Lasiurus borealis), and eastern pipistrelles ( Perimyotis subflavus) were the most frequently recorded species and activity was significantly greater in 2001 than in 2002. In 2001, overall activity was significantly greater in the Thin stands than in the Control stands; activity in the Burn and Thin&Burn stands was intermediate. Activity was also greater in treated stands than in the Control stands in 2002, but the difference was not statistically significant ( P = 0.08). In both years we recorded significantly more calls at 9 m than at 0.5 m above ground but the treatments did not affect vertical use of the stands. Activity of big brown bats and red bats was significantly higher in Thin stands than in Control or Burn stands, whereas activity of pipistrelles did not vary among treatments. Our results suggest that treatments that reduce clutter, particularly thinning, increase the suitability of pine stands for bats’ foraging and commuting activity in the Piedmont region. Thus, use of these practices may help to preserve the biodiversity of managed pine forests in the South.

Changes in prey abundance unlikely to explain the demography of a critically endangered Central European bat

Summary Recognizing the factor(s) that caused a demographic crash is a prerequisite to the development of a tailored population restoration plan. While habitat destruction leaves little scope for population persistence, cryptic habitat deterioration (for example through reduction of food resources) may similarly render an area totally inhospitable, while it still appears to have a suitable habitat configuration. Most European bat species have undergone dramatic declines over the past decades. Once among the most widespread and abundant bat species of Central Europe, the lesser horseshoe bat, Rhinolophus hipposideros (Bechstein 1800), is today extinct in many regions. Although changes in the agricultural landscape have been suggested as the major cause of decline, recent studies have shown that this bat forages almost exclusively in woodland, a habitat that has increased in area across continental Europe over the past decades. This suggests that habitat eradication per se is unlikely to be the main cause of decline. But could cryptic habitat deterioration play a harmful role? We looked at the abundance of insect prey in woodland in the vicinity of colonial roosts with diverging demographic status (extinct, declining or recovering populations), both in the Swiss lowlands (Swiss Plateau) and in the Alps. We predicted that population size correlates positively with prey abundance. Diet composition mirrored local insect prey abundance, confirming an opportunistic foraging strategy. Prey abundance showed marked seasonal variation, but did not differ between sites harbouring extinct, declining or recovering populations. There was also no difference in food abundance between extinct populations in the lowlands and recovering populations in the Alps. Synthesis and applications. Cryptic habitat deterioration through a reduction in prey abundance is unlikely to preclude recolonization of abandoned areas by presently recovering populations. However, sufficient areas of natural forest should be preserved or created around potential nursery roosts. Moreover, connectivity between forest patches must be ensured (by creation of hedges and tree lines) to prevent any spatial gap in recolonization within semi‐open agricultural landscapes. Other threatened European forest bats may also benefit from these measures.

Ranging behavior and foraging ecology of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in Yasuní National Park, Ecuador.

In a year-long study, I investigated the ranging behavior of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in a terra firma rainforest in Yasuní National Park, Ecuador, and examined the relationship between ranging, diet, food availability, and food patch use for this population. In Yasuní the total home range sizes for two social groups were 124 and 108 ha, which are much smaller than has been reported previously for Lagothrix elsewhere in its geographic distribution. The mean yearly day range estimates for these same groups were 1,792 m and 1,878 m, which are well within the range of variation previously reported. Ranging behavior was not correlated with the current habitat-wide abundance of ripe fruit, which comprises 76.3% of the yearly diet for this population, but was associated with one measure of likely insect prey abundance and with the availability of immature fruits, a minimal part of the diet. Specifically, one study group moved significantly greater distances during months of high likely insect prey abundance and when immature fruits were abundant. The second study group also traveled farther when likely insect prey abundance was high and when immature fruits were abundant, although the latter relationship only approached significance. This group also devoted significantly more of its daily activity budget to travel during these times. These results indicate that variation in ripe fruit abundance makes no meaningful contribution to explaining variation in ranging behavior for this population of woolly monkeys. Instead, the results raise the possibility that some aspects of the ranging behavior of frugivorous primates may be related to the availability of alternative food sources, such as animal prey, or to monitoring the phenological status of important fruit trees, rather than simply reflecting the degree of intragroup feeding competition.

Ranging behaviour and habitat preference of a wild marmoset group, Callithrix humeralifer (Callitrichidae, Primates)

The ranging behaviour of a group of marmosets (Callithrix humeralifer) in seasonal Amazonian rain forest was studied during one year. Range sizes (monthly and daily), day range lengths and patterns of range use are examined for correlations with feeding behaviour and the distribution of three forest types within the marmoset's range. Seasonal differences in ranging are associated with changes in the abundance and distribution of plant food sources. The marmosets ranged more widely and used more sources of a greater diversity of plant food species, which were distributed over a wider area, in the wet season than in the dry season. In the dry season, they ranged over a smaller area and, although they used fewer sources of a reduced diversity of plant species overall, they exploited a larger number of sources of the five highest ranked plant species in the diet. Throughout the year, they showed a preference for disturbed primary forest, characterized by dense understoreys and abundant second growth patches. Reasons for this preference are discussed, taking into account their use of fruits of typical pioneer species (particularly in the dry season), insect prey abundance, sleeping site availability and defence against predators.

Observations of social and reproductive biology of the bent‐winged bat Miniopterus australis in northern Borneo

The small bent‐winged bat Miniopterus australis was studied at low tropical latitudes north of the equator, principally in Subis cave, Niah, Sarawak, East Malaysia. During the course of field‐work in 1957–58, most specimens were captured at roost in concavities in the cave ceiling, here termed “cupolas”. At all months of observation, roosting groups varied from one to seven bats. Solitary bats were predominantly males, and multiple groups rarely included more than one male. It is suggested that the sexes differ in their response to a potential or familiar roosting site, depending on the prior occupation by other bats. Roosting behaviour did not vary with the progress of the reproductive cycle and seemed to have no epigamic function.Observations of reproductive biology in 1957–58, supported by specimens captured in 1959–60, demonstrated that the species is monoestrous, with a brief annually recurrent breeding season in November‐December. Copulation was observed in early November and preceded ovulation. In unovulated females taken in early December the right uterine horn was distended with spermatozoa. The single embryo subsequently implanted in the right horn, although in the three females examined the fertilized ovum derived from the left ovary.Parturition occurred in late April and early May after a gestation period of 4 1/2–5 months. This period is considerably longer than the presumed species‐specific minimum, observed at latitude 15d̀ S. The prolonged gestation period is regarded as an adaptation to perennially low and variable food resources in an otherwise favourable environment, and there is evidence that the months of gestation and birth coincide with a period of limited seasonal increase in abundance of insect prey.