The pathogenic chytrid fungus, Batrachochytrium dendrobatidis, causes population decline and extinction of numerous species of tropical, principally montane, amphibians. Is B. dendrobatidis an enzootic pathogen emerging as a disease, or rather a novel invasive pathogen infecting naïve amphibians? Are only high-elevation amphibians susceptible to the pathogen? If the chytrid is enzootic, then it may be in the environment before or after epidemic decline and may infect both montane and lowland amphibians as well as other organisms. To determine distribution of the pathogen and corresponding anuran abundance, I established eight research sites of varying elevations and stages of epidemic infection from west to east, ranging from 45 m to 1215 m elevation throughout Panama west of the Canal. Differential infection susceptibility among anurans was addressed in relation to three ecological factors: anuran body size, season and habitat. Prevalence and infection intensity of the chytrid were determined at all sites and for all factors using sensitive DNA-based RT-qPCR amplification. Amphibian populations at all elevations and stages of decline showed at least some degree of chytrid infection, and the chytrid was found on reptiles. In addition to presence of the pathogen, effects of the disease chytridiomycosis were variably seen at all elevations. Habitat and season did not seem to have a strong effect on infection prevalence and/or intensity, but frogs did appear to show greater infection at smaller anuran body sizes. All of the above results are suggestive of an enzootic pathogen and perhaps only the current epidemic of chytridiomycosis disease is novel. Since the infection / Le champignon pathogène chytrid, Batrachochytrium dendrobatidis, cause la diminution et l'extinction de nombreuses populations d'amphibiens tropicaux, principalement dans les regions à haute altitude. Si le champignon est endémique, il peut rester dans l'environnement après le passage d'une épidémie, contaminant les amphibiens des hautes et basses terres, ainsi que les autres organismes. Les sites de recherche étaient établis à diverses élévations et à différents stades de l'épidémie, à l'ouest du canal de Panama, où l'état des populations d'amphibiens pouvait être examiné. L'hypersensibilité différentielle des grenouilles à la maladie était adressée pour trois facteurs: la taille des grenouilles, la saison et l'habitat. La prévalence et l'intensité de l'infection étaient déterminées pour chaque facteur à tous les sites en utilisant la technique du RT-qPCR. Les amphibiens de toutes les élévations et de tous les stades de l'épidémie ont montré au moins un niveau d'infection, indiquant la présence d'un pathogène endémique. Le chytrid a aussi été trouvé sur les reptiles. En plus de la présense du champignon, les symptômes de la maladie chytridiomycosis ont même été remarqués sur les grenouilles des terres basses. La prévalence de l'infection est restée similaire pour les forêts et les ruisseaux, et aussi pour les deux saisons, et plus élevée pour les petites grenouilles que pour les plus grosses. Puisque l'infection peut rester dans les communautés amphibiennes à toutes altitudes, habitats et saisons, qu'elle peut persister pour longtemps (jusqu'à 11 ans), et qu'elle peut survivre sur d'autres organismes, la réintro

The distributions of Sanderling and Turnstone were determined for the south side of the Tees Estuary. Location of roosting sites and the movement of the tide were the major factors affecting movement patterns of these two species. The invertebrate species Nerine, Bathyporeia and Eurydice, were observed to comprise virtually all of the Sanderling's open-beach diet. Extensive sampling of these three prey species showed a predictable occurrence along the beach with each species; most common at particular transect and distance below the High Water Mark, (e.g. Nerine was most abundant at 50 to 90 metres below the HWM). The times when these bands became available to 'foraging Sanderling helped to determine the movement patterns of the birds. Detailed studies of the feeding behaviour of Sanderling showed three main foraging techniques: probe feeding, water-column feeding and stitch feeding. The first two of these techniques have a visual component, (the Pause position). Switching occurred between these two techniques but was uncommon between the water column and stitch technique (which was a tactile feeding method). When feeding, Sanderling oriented themselves so that they could watch the progress of the waves. Colour-marked individuals of both Sanderling and Turnstone helped to determine movement, patterns, fidelity to site within a season and survival and fidelity between seasons. Mortality rates for Turnstone were especially low; fidelity was high for both species. Feeding observations on winter Turnstone showed both dispersed and concentrated situations. While aggression was seldom observed for Sanderling, it was common for Turnstone. Two main types of aggressive encounters were observed for the Turnstone and were determined mainly by the potential payoff of the encounter. The suggestion is advanced that aggressive patterns may help determine the dispersion of the Turnstone. Aggression may also help to determine the feeding location of the juveniles. Observations of breeding Turnstone (Finland) present, a picture of communal feeding (aiding in, predator awareness), high; nesting concentrations and numerous, interactions with the lafid species present. The latter include extensile robbing of larid eggs by Turnstone. Although the summer and winter Turnstone populations have different Wintering grounds, there are valuable comparisons to be made

Despite the wide distribution and abundance of the freshwater crayfish Austropotcmobius pallipes in Britain, little is known of its population biology. The dynamics and growth of a Northumbrian population of A. pallipes were studied using an intensive-mark- recapture programme. The seasonal timing of moulting and reproduction was found to be predictable and probably related to water temperature. Stomach contents showed crayfish to be omnivorous, with plant material forming the bulk of the diet. Population size, survival and recruitment were estimated from mark- recapture data at frequent intervals. Two principal types of mortality were identified: moult-associated mortality, which was relatively intense and of short (2-3 weeks) duration, and overwinter mortality, which operated at a much lower estimated weekly rate over a period of some 30 weeks. Mortality was shown to be highly variable throughout the year. Population size generally showed a midsummer peak as recruitment into the catchable size classes occurred. Thereafter numbers declined slightly towards the end of the growth season, followed by an overwinter decline of some 50% of total numbers. Longevity was estimated to be at least eleven years. The relationship between size, age and weight was established and males shown to have faster growth rates than females after the size of sexual maturity. Growth increments and moult frequency were shown to differ between the sexes and according to body size. Reproductive females omitted one moult while carrying eggs. Growth rates were depressed by the parasite Thelohania oonteoeani and by the regeneration of a major chela. The fecundity of females and the probability of being reproductive increased with body size. The annual production of the study population was estimated at 196.49 kg ha(^-1) in 1977, 116.80 kg ha(^-1) in 1978 and 87.79 kg ha(^-1) in 1979. Detailed life histories of many marked individuals were collected which support the conclusions drawn at the population level.

The frugivory and seed dispersal by carnivores were studied using a combination of vegetation surveys, fruit production counts and analysis of faeces distribution and content. The study site is situated close to the Greek-Bulgarian border within a protected area. The habitat comprises of a mixed forest of beech, pine, oak and spruce which is occasionally interrupted by patches of fruiting trees. Faecal samples were collected on five permanent transects which were sampled monthly between May and October of 1993 and 1994.Fruiting plant density was found to be slightly higher in the forest than along forest roads, however the species diversity was much higher on the latter. In some cases, immature fruiting plants were found on transects with no mature plants in the vicinity. Availability of ripe fruit was found to increase steadily between May and September. There was a significant difference between the numbers of faeces deposited by the carnivores, with fox being the most numerous, followed by marten, bear and wolf. There was spatial and temporal variation in the number of faeces deposited. Nevertheless, there was no variation between different altitudinal zones. Martens were found to defecate more often on stones when compared with the other carnivores. The analysis of fruit consumption revealed that bears were the most frugivorous carnivores followed by foxes, wolves and martens on the basis of frequency of consumption. The temporal availability of each ripe fruit species coincided with their consumption by the carnivores in most of the cases. A number of seed species were deposited at altitudes where the plants do not normally grow. Foxes dispersed the highest numbers of seeds in the study area and bears were second as they deposited large-size faeces which contained many seeds. Of the dispersed seeds, those of Rubus sp., Rosa sp. and Fragaria vesca were deposited in the highest numbers. Only a small number fraction of seeds were damaged through handling by carnivores.

Red grouse populations were monitored for three years on study areas in Speyside and Perthshire (Scotland), where numbers have generally been declining since the mid 1970's. These low density populations are thought to be especially vulnerable to extrinsic factors, such as predation. The aim of this research was to discover what effect predators were having on grouse populations throughout the year. Adult grouse mortality, examined by searching for corpses on six 1km study sites, was concentrated in the winter months. Birds killed were in good condition and a greater proportion were found dead than in any other similar study. Peregrine falcons and red foxes were the main predators involved. Initial evidence suggested that the grouse killed were, at least partly, territorial birds and not surplus individuals. Both the number of raptors and the percentage of grouse killed was inversely related to density. Low density populations were maintained by net immigration. In the slimmer, the behaviour of the hen harrier, both at the nest, and whilst hunting was examined. Harriers exhibited a type II functional response to grouse chicks, which appeared to be their preferred prey. Moors with breeding harriers produced fewer young grouse, and on those moors where harrier predation was examined, it could account for the bulk of the losses. On the study areas, it was estimated that harriers took up to 32% of the grouse chicks in 8 weeks. A simulation model was produced which suggested that harriers can reduce the numbers of grouse shot, although there was a high degree of variation in shooting levels. The impact of harriers on subsequent grouse spring numbers was dependent on the level of overwinter losses, variation in harriers and possibly alternative prey densities. Further research is necessary to clarify some issues, but it was apparent that the effects of predators would be greatest on low density grouse populations. At these low densities, their impact will depend upon grouse breeding success and the degree of overwinter mortality relative to movement between estates. The importance of conserving heather moorland, to protect both raptors and grouse, was stressed.

<p> Large boreal peatland complexes are at the southern extent of their range in New York State and contribute considerably to regional biodiversity with their distinctive flora and fauna. The goal of this study is to inform conservation management of peatland ecosystems by providing information on the composition and structure of vegetation across environmental gradients; information that is lacking for the region. I sampled vegetation along gradients of water chemistry, canopy openness, microtopography, coarse woody debris and forest structure in 50 plots within a large boreal peatland complex in the Adirondack region of New York State. I classified ecological communities based on the most important gradients to emerge from an ordination of understory vegetation - pH and canopy openness- and I describe the composition and structure of the vegetation of those classifications. This work presents empirical data on vegetation, environmental gradients and disturbance history of a large Adirondack peatland complex, all of which is important to conservation management efforts.</p>

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