Flexible foraging strategies in a diving seabird with high flight cost

How central-place foragers change search strategy in response to environmental conditions is poorly known. Foragers may vary the total distance travelled and how far they range from the central place in response to variation in the distribution of their prey. One potential reason as to why they would extend the length of their foraging trip and its distance from the colony would be to increase prey quality or quantity, despite incurring higher transit costs. To test this trade-off hypothesis in a species with high flight costs, we recorded the foraging behaviour of razorbills (Alca torca) using state-of-the-art techniques that log both individual horizontal (flight activity) and vertical (dive activity) movements. We show that the distance that razorbills travelled to foraging locations increased with sea-surface temperature, which may relate to higher prey quality or quantity. This relation is supported by an indirect index of patch quality, based on dive profiles, which also increased with travel distance from the colony. Furthermore, we show that this index was highest during the daily peak in diving activity, around midday. Taken together, these results suggest that razorbills are capable of adjusting their search strategies sensitively in response to proximate environmental cues.     

Making sense of predator scents: investigating the sophistication of predator assessment abilities of fathead minnows

According to the threat-sensitive predator avoidance hypothesis, selection favors prey that accurately assess the degree of threat posed by a predator and adjust their anti-predator response to match the level of risk. Many species of animals rely on chemical cues to estimate predation risk; however, the information content conveyed in these chemical signatures is not well understood. We tested the threat-sensitive predator avoidance hypothesis by determining the specificity of the information conveyed to prey in the chemical signature of their predator. We found that fathead minnows (Pimephales promelas) could determine the degree of threat posed by northern pike (Esox lucius) based on the concentration of chemical cues used. The proportion of minnows that exhibited an anti-predator response when exposed to a predator cue increased as the concentration of the pike cue used increased. More surprisingly, the prey could also distinguish large pike from small pike based on their odor alone. The minnows responded more intensely to cues of small pike than to cues of large pike. In this predator–prey system small pike likely represent a greater threat than large pike.Communicated by A. Mathis     

Protection of biota on nonpark public lands: Examples from the US Department of Energy Oak Ridge Reservation

Security buffers of Department of Defense (DoD) and Department of Energy (DOE) reservations provide long-term habitat protection for many rare and endangered species. The importance of these government-owned reservations as nationally valuable resources has been relatively unrecognized. During the last 50 years, the DOE Oak Ridge Reservation (ORR) has been a relatively protected island in a region of rapidly expanding urbanization and land clearing. Consisting of the Oak Ridge National Environmental Research Park and associated lands surrounding DOE facilities at Oak Ridge Tennessee, the unique nature of the ORR in the surrounding landscape is clearly visible from the air and has been documented using remote sensing data. Although forests dominate much of other regions of eastern Tennessee, this 15,000-ha tract of mostly natural forest habitat is unique in the southern Ridge and Valley physiographic province, which is otherwise widely developed for pasture, marginal cropland, woodlot, and urban uses. Twenty state-listed and federal-candidate plant species are known to be present on the ORR. This richness of species, which are provided protection by state and federal laws, exceeds that of the Great Smoky Mountains National Park on a species area basis and is an index of the value of the ORR both regionally and nationally in conserving biodiversity. With the end of the Cold War, changing DoD and DOE missions combined with increasing development pressure contribute to uncertainty in the future management of security reservations.     

Field efficacy and baseline toxicities of pyriproxifen, acetamiprid, and diafenthiuron against Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) in Burkina Faso (West Africa)

Bioassays were conducted in 2001 and 2002 to estimate toxicities and dose-response relationships of 24 Bemisica tabaci Gennadius populations to pyriproxifen, acemitaprid, and diafenthiuron. LC50s ranging from 0.014 to 0.096 mgL(-1), 0.60 to 1.3 mgL(-1), and 3.5 to 6.7 mgL(-1) were observed respectively for pyriproxifen, acemitaprid, and diafenthiuron. These LC50s much lower than the field doses recommended for each compound. A fast increase in rates of mortality within a narrow range of lethal concentrations was observed for each compound. indicating that all three compounds were highly effective at killing whiteflies. In a separate experiment, pyriproxifen, acemitaprid, and diafenthiuron were tested in 2001 and 2002 to compare their effectiveness and assess their impact on parasitism in the field. In both years all three compounds significantly prevented B. tabaci populations from reaching economic injury levels in cotton and minimized adverse effects on parasitism. Our results provide for the first time baseline toxicological, field efficacy, and effect on parasitism data for pyriproxifen, acemitaprid, and diafenthiuron against B. tabaci in West Africa. These compounds should be included in a resistance management program of the cotton pest complex and their use should be restricted to prevent the building of resistance in B. tabaci populations.     

The Global International Waters Assessment for the Pacific Islands: aspects of transboundary, water shortage, and coastal fisheries issues

Aspects of transboundary, water shortage, and fisheries issues are discussed in the context of the recently completed Global International Waters Assessment (GIWA) for the Pacific Islands. The region encompasses some 30 million km2 and approximately 12% of the world's ocean space, and features great geographic, demographic and developmental diversity. Global change, especially sea level rise and sea surface temperature increases, is the dominant transboundary concern as it impacts all aspects of life. Water shortage and unsustainable fishing issues are selected for discussion, as they will dominate the region into the foreseeable future, and they are illustrated with examples from Fiji, Kiribati, and Tonga. The environmental impacts are exacerbated by socioeconomic issues such as high population growth rates, urban drift, the breakdown of traditional life styles and the rapid adoption of the cash economy. Policy options that may assist in addressing these issues are proposed.     

Mating flights select for symmetry in honeybee drones (Apis mellifera)

Males of the honeybee (Apis mellifera) fly to specific drone congregation areas (DCAs), which virgin queens visit in order to mate. From the thousands of drones that are reared in a single colony, only very few succeed in copulating with a queen, and therefore, a strong selection is expected to act on adult drones during their mating flights. In consequence, the gathering of drones at DCAs may serve as an indirect mate selection mechanism, assuring that queens only mate with those individuals having a better flight ability and a higher responsiveness to the queen’s visual and chemical cues. Here, we tested this idea relying on wing fluctuating asymmetry (FA) as a measure of phenotypic quality. By recapturing marked drones at a natural DCA and comparing their size and FA with a control sample of drones collected at their maternal hives, we were able to detect any selection on wing size and wing FA occurring during the mating flights. Although we found no solid evidence for selection on wing size, wing FA was found to be significantly lower in the drones collected at the DCA than in those collected at the hives. Our results demonstrate the action of selection during drone mating flights for the first time, showing that developmental stability can influence the mating ability of honeybee drones. We therefore conclude that selection during honeybee drone mating flights may confer some fitness advantages to the queens.     

Regulation of reproduction by dominant workers in bumblebee (Bombus terrestris) queenright colonies

The mechanisms of regulating worker reproduction in bumblebees were studied by direct behavioral observations and by measuring ovarian development and juvenile hormone (JH) biosynthesis rates in workers under different social conditions. Workers in the last stage of Bombus terrestris colony development (the competition phase) had the lowest ovarian development and JH biosynthesis rates. Callows introduced into colonies immediately after queen removal (dequeened colonies) demonstrated a significant increase in ovarian development before, but not during, the competition phase. These findings differ from the higher ovarian development in colonies during the competition phase predicted by the prevailing hypothesis that worker reproduction starts in response to a decrease in queen inhibition. Reproduction of callows housed with dominant workers in small queenless groups was inhibited as in queenright colonies. This suggests that the reduced ovarian development and JH biosynthesis rates observed in dequeened and normally developing colonies during the competition phase also reflect inhibition by dominant workers. Thus, two distinct stages of inhibition of reproduction seem to exist: (1) before the competition phase, when the queen slows down worker ovarian development and prevents oviposition; (2) during the competition phase, when dominant workers inhibit ovarian development of other workers. Between these stages there seems to be a temporal “window” of enhanced worker reproductive development. The queen's typical switch to haploid egg production was not associated with changes in worker ovarian development or JH biosynthesis rates. These findings suggest that regulation of worker reproduction in B. terrestris is not determined by simple changes in the queen's inhibition capacity or by the sex of offspring and that the worker's role is more important than previously believed. Received: 18 March 1998 / Accepted after revision: 18 July 1998     

Ethnobotany of Woody Species in Second-Growth, Old-Growth, and Selectively Logged Forests of Northeastern Costa Rica

Abstract: We assessed quantitatively the woody species used for timber, medicine, and other products in 10 tropical wet-forest stands with different land-use histories in the Atlantic lowlands of northeastern Costa Rica. Species were classified into 20 use categories based on regional ethnobotanical studies. Three size classes of woody vegetation were sampled in nested, contiguous plots along transects: trees (≥5 cm diameter at breast height [dbh]), saplings (>1 m high, <5 cm dbh), and seedlings (>20 cm high, <1 m high). Our study included five second-growth stands, three old-growth stands, and two selectively logged stands. Of the 459 woody species surveyed, 70% of the species and 86% of the total number of individuals had at least one use. Overall, species richness was highest for medicinal species (167 species). Absolute and relative abundance of medicinal and timber trees was significantly higher in second-growth stands than in old-growth and selectively logged stands. For 8 of the 15 use categories examined statistically, stem density showed no significant differences across forest types for any stem size class. Young, tropical, second-growth forests and selectively logged forests have high utilitarian as well as conservation value and will likely become important sources of forest products. The success of secondary forest regeneration, however, depends critically upon conservation of genetically diverse source populations in forest fragments and protected old-growth stands.