Estrus cycle asynchrony in wild female chimpanzees, Pan troglodytes schweinfurthii

Although estrous synchrony has been reported in a number of mammalian species, most often among primates, methodological and analytical problems make it difficult to interpret these results. We developed a novel estrous synchrony index and employed a randomization procedure to analyze long-term observations of female chimpanzee (Pan troglodytes schweinfurthii) estrous cycles at the Mahale Mountains National Park, Tanzania. Our results revealed that female chimpanzees at Mahale avoid synchronizing their estrous periods with each other. We also found that birthrates decreased as the breeding sex ratio increased. We suggest that estrous asynchrony decreases female–female competition for mates. Asynchrony may also reduce the potential for male sexual coercion by nonpreferred mating partners.     

Accounting for variation in prey selectivity by zooplankton

An ingestion-based prey selectivity function (IS) is described specifically to aid the simulation of zooplankton activity in circumstances in which selectivity varies, for example, as functions of prey palatability or abundance. In IS, the ultimate control of the rate of predation is not the external concentration of prey but the total rate of prey capture relative to predator demand. Further, “preference” is not an input (as it is for most prey selection functions) so that the selection or deselection of any or all prey can be freely altered. Hence, if required, all prey could be deselected, or the impact of inert materials or turbulence adversely affecting capture rates of any or all prey can be considered. Capture kinetics are not fixed at a common value for all items. In its basic form IS contains no more variables than other selectivity functions. The construction and use of switches to vary grazing in response to changes in abundance of alternative prey types or in prey nutritional (stoichiometric) quality is demonstrated. The advantages of using IS instead of the widely used ratio-based selectivity function is demonstrated with reference to model fits to experimental datasets for microzooplankton activity.     

Estimating percentiles from composite environmental samples when all observations are nondetectable

Many environmental sampling problems involve some specified regulatory or contractual limit (RL). Often the interest is in estimating the percentile of the underlying contaminant concentration distribution corresponding to RL. The focus of this paper is on obtaining a point estimate and a lower confidence limit for that percentile when all observations are nondetectable, with the ith observation known to be less than some detection limit DLI, where DLi RL. Since composite samples are being considered, it is not unreasonable to assume an underlying normal distribution.     

Genetic Variation and the Immune Response in Natural Populations of Pocket Gophers

It is thought that genetic variation can affect the persistence of a population through its influence on disease susceptibility. We assessed genome-wide genetic variation, variation at a locus involved in the immune system, and acceptance or rejection of skin grafts in three natural populations of the pocket gopher ( Thomomys bottae ). Multilocus DNA fingerprints confirmed previous allozyme data, revealing high levels of variation among Hastings Reserve pocket gophers and almost complete within-population identity for individuals from the two Patricks Point populations (Patricks J and Patricks F), although Patricks J animals were dissimilar to animals from Patricks F despite their proximity. Individuals from the high-variation population consistently rejected within-population reciprocal skin grafts, whereas Patricks J and Patricks F individuals accepted within-population grafts. Patricks J and Patricks F individuals were found to be immunocompetent, however, as revealed by the ability of all individuals to reject between-population grafts, including those that previously accepted within-population grafts. A DNA heteroduplex analysis was then used to directly characterize variability at DQα, a locus of the immune system's major histocompatability complex. Both populations low in genetic variation were fixed for unique DQα alleles, whereas observed heterozygosity in the Hastings population was 0.43, ascribable to at least three unique alleles. These data are in accord with previous cheetah skin-graft results and confirm that skin grafts can be used to assess genetic similarity. We suggest that although many animal populations can persist with extremely low levels of genetic variation in the wild, such populations may be at a greater risk of extinction from particular pathogens because of their genetic uniformity.     

An experimental study of competition for food between male and female nestlings of the red-winged blackbird

Summary Ten experimental broods of red-winged black-bird (Agelaius phoeniceus) nestlings, experimentally manipulated to contain two males and two females of similar age, were observed with the aid of video cameras to determine (a) which nestling characteristics were most important in influencing its chances of being fed and (b) if males and females differed with respect to these characteristics. Nestlings that could reach highest while begging were most successful at obtaining food from parents during individual feeding bouts. However, while there was a tendency for nestlings that begged earlier to be offered food first, a nestling's position in the nest during these bouts did not influence its feeding success. Males begged more than often females and were offered more food by parents. Males were also more likely to be fed when they begged. This was most likely because males, being larger than females, were able to reach higher while begging. Neither sex was more likely to beg sooner or occupy certain positions in the nest. However, while males that had been transferred from other nests received less food than natal males, there were no differences in food acquisition between transferred and natal females. Differences in the relative success of males and females under different conditions may help explain differences in fledgling sex ratios observed in many dimorphic species.     

An evaluation of the UAM-V predicted concentrations of carbon monoxide and reactive nitrogen compounds over the eastern United States during summer 1995

While there is a clear need to evaluate a photochemical model's ability in predicting not only the concentrations of O3, but also precursors and other trace species, many previous studies have focused only on the assessment of During the 1995 summer season, in addition to the routine monitoring of criteria pollutants, several research-oriented monitoring campaigns were conducted over the eastern United States, providing an extensive database of reactive nitrogen compounds, CO, and speciated hydrocarbon data. In this study, we examine the ability of a photochemical modeling system, RAMS/ UAM-V, to reproduce the measured concentrations of CO, NO2, and NOy over the region during the summer of 1995. The results demonstrate that there is agreement between modeled and measured seasonal average concentrations of NO2, both at the routine and research monitors. The same is true for NOy, but to a lesser degree. However, the model is found to significantly underpredict CO for the routine monitors in comparison to the research monitors.     

Quantification of PCDD/F concentrations in animal manure and comparison of the effects of the application of cattle manure and sewage sludge to agricultural land on human exposure to PCDD/Fs

PCDD/Fs were quantified in samples of cattle, pig, sheep and chicken manure. TEQs ranged from 0.19 ng TEQ/kg dw for the pig manure to 20 ng TEQ/kg dw for one cattle manure sample. Exposure assessments were carried out to compare the effect of various sewage sludge and cattle manure land application scenarios on human PCDD/F exposure. Background exposure was estimated at 4.9 pg TEQ/kg bw/day and it was found that land application of sewage sludge and cattle manure at contemporary rates did not increase PCDD/F TEQ background exposure. It was concluded that the application of sewage sludge, under the new UK guidelines, and cattle manure to agricultural land, do not make a significant contribution to human exposure to PCDD/Fs.     

Polychlorinated biphenyls in digested UK sewage sludges

Twelve sewage sludges from rural, urban and industrial waste water treatment works in north west England were analysed for polychlorinated biphenyls by capillary GC-ECD. The total polychlorinated biphenyl content ranged between 106 to 712 μg/kg, with a mean of 292 μg/kg. Di- and penta-chlorinated congeners made the greatest contribution to the ΣPCB concentrations at most sites. The 6 IUPAC congeners were found in the following order of abundance, 101>180>153>138>52>28. Industrial inputs would appear to influence levels of ΣPCB in the sludge.

If these sludges were ploughed into arable land at typical rates only a slight elevation in soil ΣPCB levels would result. Alternatively, if the same quantity of sludge were applied to the surface of pasture grassland, significant elevations in the potential transfer of PCBs to grazing livestock may result.     

The global re-cycling of persistent organic pollutants is strongly retarded by soils

'Persistent organic pollutants' (POPs) are semi-volatile, mobile in the environment and bioaccumulate. Their toxicity and propensity for long-range atmospheric transport (LRAT) has led to international bans/restrictions on their use/release. LRAT of POPs may occur by a 'single hop' or repeated temperature-driven air-surface exchange. It has been hypothesised that this will result in global fractionation and distillation-with condensation and accumulation in polar regions. Polychlorinated biphenyls (PCBs)--industrial chemicals banned/restricted in the 1970s--provide a classic illustration of POP behaviour. A latitudinally-segmented global PCB inventory has been produced, which shows that approximately 86% of the 1.3 x 10(6) tonnes produced was used in the temperate industrial zone of the northern hemisphere. A global survey of background surface soils gives evidence for 'fractionation' of PCBs. More significantly, however, very little of the total inventory has 'made the journey' via primary emission and/or air-surface exchange and LRAT out of the heavily populated source regions, in the 70 years since PCBs were first produced. Soils generally occlude PCBs, especially soils with dynamic turnover of C/bioturbation/burial mechanisms. This limits the fraction of PCBs available for repeated air-soil exchange. The forested soils of the northern hemisphere, and other C-rich soils, appear to be playing an important role in 'protecting' the Arctic from the advective supply of POPs. Whilst investigations on POPs in remote environments are important, it is imperative that researchers also seek to better understand their release from sources, persistence in source regions, and the significant loss mechanisms/global sinks of these compounds, if they wish to predict future trends.