Deciding when to explore and when to persist: a comparison of honeybees and bumblebees in their response to downshifts in reward

As the distribution of food resources shifts over time, central place foragers are likely to be repeatedly faced with the question of when to abandon a forage site that is declining in value and to subsequently search elsewhere. Although there has been a great deal of investigation into how individual foragers allocate time between exploration and exploitation, few studies have sought to explore this issue within a larger functional context. We take a comparative approach to this problem by examining decision making in individual honeybees and bumblebees as they responded to a downshift in food reward. Our results show not only that honeybees and bumblebees have significantly divergent strategies with regards to abandoning a food source that is declining in value but also in terms of the subsequent tendency to seek an alternative food source. We interpret these results in terms of both biological and social distinctions between these species and highlight how group-level characteristics are likely to shape the evolutionarily derived foraging strategies of individual animals.     

Business value of toxics reduction and pollution prevention planning

As part of Ontario's Toxics Reduction Strategy, the Ontario Ministry of the Environment provided funding for two years to a partnership of the Ontario Centre for Environmental Technology Advancement (OCETA) and the Canadian Manufacturers & Exporters (CME) to deliver a Cleaner and Greener Manufacturing Program, which will include the development and delivery of training and technical assistance programs on toxics reduction and pollution prevention (P2). Over the next two years, OCETA and CME will be working with small-to-medium sized manufacturers to demonstrate the business value of toxics reduction and pollution prevention planning to help motivate businesses to move into a greener economy.     

DETERMINING THE SOURCE OF STREAM CONTAMINATION IN A KARST‐WATER SYSTEM,SOUTHWEST VIRGINIA,USA1

ABSTRACT: Karst terrane provides a linkage between surface water and ground water regimes by means of caves, sinkholes and swallets, and sinking streams, and facilitates the inter‐watershed transfer of water and contaminants through these subsurface systems. The goal of this study was to develop procedures to identify the sources of degradation of a creek situated in a complex karst‐water system. The study approach consisted of using dye tracing technique to determine subsurface flow paths through the karst system, a water‐sampling network to identify and characterize pollution sources within the surface watershed and subsurface flow regime, and evaluation of analytical data for several water quality parameters. The results of this study provide an interesting perspective of water and contaminant movement in karst‐water systems and pinpoint the sources of stream contamination for a case study site in southwest Virginia where two springs supply water to a contaminated freshwater stream.     

Allowable levels of take for the trade in Nearctic songbirds

The take of Nearctic songbirds for the caged-bird trade is an important cultural and economic activity in Mexico, but its sustainability has been questioned. We relied on the theta-logistic population model to explore options for setting allowable levels of take for 11 species of passerines that were subject to legal take in Mexico in 2010. Because estimates of population size necessary for making-periodic adjustments to levels of take are not routinely available, we examined the conditions under which a constant level of take might contribute to population depletion (i.e., a population below its level of maximum net productivity). The chance of depleting a population is highest when levels of take are based on population sizes that happen to be much lower or higher than the level of maximum net productivity, when environmental variation is relatively high and serially correlated, and when the interval between estimation of population size is relatively long (> or = 5 years). To estimate demographic rates of songbirds involved in the Mexican trade we relied on published information and allometric relationships to develop probability distributions for key rates, and then sampled from those distributions to characterize the uncertainty in potential levels of take. Estimates of the intrinsic rate of growth (r) were highly variable, but median estimates were consistent with those expected for relatively short-lived, highly fecund species. Allowing for the possibility of nonlinear density dependence generally resulted in allowable levels of take that were lower than would have been the case under an assumption of linearity. Levels of take authorized by the Mexican government in 2010 for the 11 species we examined were small in comparison to relatively conservative allowable levels of take (i.e., those intended to achieve 50% of maximum sustainable yield). However, the actual levels of take in Mexico are unknown and almost certainly exceed the authorized take. Also, the take of Nearctic songbirds in other Latin American and Caribbean countries ultimately must be considered in assessing population-level impacts.     

Trap mortality in mark-recapture studies

When animals die in traps in a mark-recapture study, straightforward likelihood inferences are possible in a class of models. The class includes M₀, M_t, and M_b as reported by White et al. (Los Alamos National Laboratory, LA-8787-NERP, pp 235, 1982), those that do not involve heterogeneity. We include three Markov chain “persistence” models and show that they provide good fits in a trapping study of deer mice in the Cascade-Siskiyou National Monument of Southern Oregon where trapping mortality was high.

Prioritizing Pacific Salmon Stocks for Conservation

Over 300 native stocks of Pacific salmon, steelhead, and coastal cutthroat trout (Oncorhynchus spp.) are at risk of extinction in the Pacific Northwest. With only limited resources available for conservation and recovery, prioritization of these stocks may become necessary if meaningful measures are to be implemented. We propose criteria by which prioritization may be guided. First, we rank stocks for risk of extinction, either by population viability analysis or by a set of surrogate measures. Then we rank stocks for biological consequences of extinction, using sets of questions designed to establish the genetic and evolutionary consequences and the ecological consequences if a stock were to become extinct. Together, these rankings allow stocks to be prioritized for a range of possible actions, with those stocks at highest risk and bearing the greatest biological consequences of extinction receiving attention first. Application of the prioritization process to 20 Pacific anadromous salmonid stocks worked as intended, although data limitations are considerable. The process is most likely to work successfully when applied to many stocks on which data exist, when several experts carry out the prioritization, and when the results are peer reviewed.