The use of sewage treatment works as foraging sites by insectivorous bats

Sewage treatment works with percolating filter beds are known to provide profitable foraging areas for insectivorous birds due to their association with high macroinvertebrate densities. Fly larvae developing on filter beds at sewage treatment works may similarly provide a valuable resource for foraging bats. Over the last two decades, however, there has been a decline in filter beds towards a system of “activated sludge”. Insects and bat activity were surveyed at 30 sites in Scotland employing these two different types of sewage treatment in order to assess the possible implications of these changes for foraging bats. Bat activity (number of passes) recorded from broad-band bat detectors was quantified at three points within each site. The biomass of aerial insects, sampled over the same period as the detector surveys, was measured using a suction trap. The biomass of insects and activity of Pipistrellus spp. was significantly higher at filter beds than at activated sludge sites. In addition, whilst foraging activity of Pipistrellus spp. at filter beds was comparable to that of adjacent “good” foraging habitat, foraging at activated sludge sites was considerably lower. This study indicates the high potential value of an anthropogenic process to foraging bats, particularly in a landscape where their insect prey has undergone a marked decline, and suggests that the current preference for activated sludge systems is likely to reduce the value of treatment works as foraging sites for bats

Changes in milk composition during lactation in three species of insectivorous bats

Changes in milk composition are described for three species of free-ranging insectivorous bats (Myotis lucifugus, M. velifer, and Tadarida brasiliensis) from early to mid (peak) lactation. Dry matter and energy concentrations in milk increased from early to mid-lactation. In M. lucifugus and T. brasiliensis, but not M. velifer, these increases were due largely to a rise in fat concentration, since protein and carbohydrate remained relatively constant. Energy content of milk (kJ·g-1) for each species from early through mid-lactation was related to dry matter (DM) as follows: M. lucifugus (y=0.31 DM-0.32, r 2=0.68), M. velifer (y=0.48 DM-5.08, r 2=0.99), and T. brasiliensis (y=0.37 DM-1.51, r 2=0.61). Comparison of the effect of sampling method on milk composition of T. brasiliensis indicated that fat, dry matter, and energy concentrations increased significantly from pre-dawn to prenoon samples. Relatively high fat and low water levels in T. brasiliensis milk may reflect the limited access that lactating females have to free water, as well as need to minimize mass of stored milk during long foraging trips. Conversely, lower fat concentrations and higher water levels in milk in M. lucifugus and M. velifer may relate to the propensity for colonies of these two species to roost and forage near bodies of water. In addition, differences in milk fat concentrations observed among the three species may correlate to daily suckling schedules. Females of T. brasiliensis, for example, roost apart from and suckle their young on a regular daily schedule, whereas both species of Myotis roost with their pups and appear to suckle them on demand

Vector time and causality among abstract events in distributed computations

An important problem in analyzing distributed computations is the amount of information. In event-based models, even for simple applications, the number of events is large and the causal structure is complex. Event abstraction can be used to reduce the apparent complexity of a distributed computation. This paper discusses one important aspect of event abstraction: causality among abstract events. Following Lamport [24], two causality relations are defined on abstract events, called weak and strong precedence. A general theoretical framework based on logical vector time is developed in which several meaningful timestamps for abstract events are derived. These timestamps can be used to efficiently determine causal relationships between arbitrary abstract events. The class of convex abstract events is identified as a subclass of abstract events that is general enough to be widely applicable and restricted enough to simplify timestamping schemes used for characterizing weak precedence. We explain why such a simplification seems not possible for strong precedence

Reproductive biology and postnatal development in the tent-making bat Artibeus watsoni (Chiroptera: Phyllostomidae)

In this study we investigated the reproductive patterns and postnatal development in the tent‐making bat Artibeus watsoni. We sampled two populations in the Golfito Wildlife Refuge and Corcovado National Park, south‐western Costa Rica, from June 2003 to March 2005. Most females were pregnant during the months of January and June, and most were lactating in March and July, indicating that this species exhibits seasonal bimodal polyoestry, with the first parturition peak occurring in February–March and the second in June–July. Additionally, we observed a postpartum oestrus following the first parturition, but not after the second. Females entered oestrus again in November–December and had a gestation period of c. 3 months. A female‐biased sex ratio of neonates was observed during the second parturition period, and young were born at 32 and 56% of their mothers' body mass and length of forearm, respectively. Adult proportions in length of forearm were attained faster than adult proportions in body mass, and sustained flight was only possible after 35 days of age, when pups had achieved 100 and 80% of adult length of forearm and body mass proportions, respectively. Weaning and roosting independence occurred when young were c. 30–40 days old, and young females appeared to remain close to their place of birth, at least for their first mating period, whereas adult males were never recaptured near their birth site. In addition, sexual maturity was reached in as little as 3 months in females born during the first parturition period, whereas females born during the second birth period in June–July seemed to reach maturity at 6 months of age. Our results show that A. watsoni belongs to the faster lane of the slow–fast continuum of life‐history variation in bats, which may be attributed primarily to its roosting and feeding ecology.Idea Wild/[]//Estados UnidosConsejo Nacional de Ciencia y Tecnología/[]/Conacyt/MéxicoMinisterio de Ciencia, Tecnología y Telecomunicaciones/[]/MICITT/Costa RicaAmerican Society of Mammalogists/[]/ASM/Estados UnidosCleveland Metroparks Zoo/[]//Estados UnidosBat Conservation International/[]/BCI/Estados UnidosConservation, Food and Health Foundation/[]//Estados UnidosBoston University’s Center/[]//Estados UnidosUniversidad de Costa Rica/[]/UCR/Costa RicaUCR::Sedes Regionales::Sede del Su