Evaluating Global Positioning System Telemetry Techniques for Estimating Cougar Predation Parameters

ABSTRACT Using clusters of locations obtained from Global Positioning System (GPS) telemetry collars to identify predation events may allow more efficient estimation of behavioral predation parameters for the study and management of large carnivore predator-prey systems. Applications of field- and model-based GPS telemetry cluster techniques, however, have met with mixed success. To further evaluate and refine these techniques for cougars (Puma concolor), we used data from visits to 1,735 GPS telemetry clusters, 637 of which were locations where cougars killed prey >8 kg in a multi-prey system in west-central Alberta. We tested 1) whether clusters were reliably created at kill locations, 2) the ability of logistic regression models to identify kill occurrence (prey >8 kg) and multinomial regression models to identify the prey species at a kill cluster, and 3) the duration of monitoring required to accurately estimate kill rate and prey composition. We found that GPS collars programmed to attempt location fixes every 3 hours consistently identified locations where prey >8 kg were handled, and cluster creation was robust to GPS location acquisition failures (poor collar fix success). The logistic regression model was capable of estimating cougar kill rate with a mean 5-fold cross validation error of <10%, provided the appropriate probability cutoff distinguishing kill clusters from non-kill clusters was selected. Logistic models also can be used to direct visits to clusters, reducing field efforts by as much as 25%, while still locating >95% of all kills. The multinomial model overpredicted occurrence of primary prey (deer) in the diet and underpredicted consumption of alternate prey (e.g., elk and moose) by as much as 100%. We conclude that a purely model-based approach should be used cautiously and that field visitation is required to obtain reliable information on species, sex, age, or condition of prey. Ultimately, we recommend a combined approach that involves using models to direct field visitation when estimating behavioral predation parameters. Regardless of the monitoring approach, long continuous monitoring periods (i.e., >100 days of a 180-day period) were necessary to reduce bias and imprecision in kill rate and prey composition estimates.     

The U.K. Acid Waters Monitoring Network: an assessment of chemistry data, 1988–93

1. The current extent and distribution of acidified surface waters in the U.K. is assessed using data collected between 1988 and 1993 as part of the U.K. Acid Waters Monitoring Network (AWMN). The data have been collected against a background of constant S deposition across the U.K. throughout the monitoring period. 2. Surface waters with mean pH < 5.0 occur in south-west Scotland, south-east Northern Ireland, the Lake District and south-east England. In addition, sites with mean pH < 5.5 are found in central and north-east Scotland, the Pennines and north Wales. These areas receive, and have historically received, high levels of S deposition and xSO₄ is identified as the main contribution to non-marine acid anion concentrations. 3. Mean total oxidized nitrogen (TON) concentrations are > 10 μeq l^–1 at ten of the twenty-two sites which are found in areas broadly corresponding to areas of high N deposition. The mean contribution of TON to total non-marine acid anion concentration is > 10% at sixteen sites and > 20% at six sites. Most sites, except for those with TON < 10 μeq l^–1 and mainly located in north-west Scotland and Northern Ireland, demonstrate strong seasonality in TON concentrations and during autumn and winter instantaneous contributions of TON to total non-marine acid anions is up to 60%. This confirms the importance of N with respect to surface water acidification and strengthens the case for implementation of controls on future N emissions. 4. The data period is currently too short for rigorous trend analysis given the monthly/quarterly sampling frequency in streams/lakes, respectively. Nevertheless, increased SO₄ and xSO₄ can be observed in the time series at sites in south-west Scotland and north Wales despite constant deposition to these areas. Similar trends are evident in longer-term more frequent data at two sites and may reflect hydrometeorological influences, especially the duration and intensity of hot and dry weather in summer which promotes mineralization of organic S.     

Lake sediment microlaminae and annual mortalities of photosynthetic bacteria in an oligomictic lake

SUMMARY 1. A novel mechanism of microlamina formation in oligomictic lakes is proposed. During spring and summer in Zaca Lake, an oligomictic lake in Santa Barbara, California, a light-coloured microlamina is formed. During winter, a mass mortality of sulphur-rich phototrophic bacteria occurs following the ventilation of the chemocline or the overturn of the lake. When this occurs, oxygen is introduced into the chemocline killing most of the anaerobic bacteria. When these sulphur-laden bacteria die and settle to the bottom of the lake, they form a black microlamina which is rich in ferrous monosulphides.
2. The varved stratigraphy of the Zaca Lake sediment core presents an opportunity to correlate stratigraphic events in the lake's varved sediments with events reported for its catchment over the last 200 years.
3. Colonization by Europeans dates back to the 1760s, making this one of the best-documented histories for a small lake in North America. A number of events have been correlated with stratigraphic information from the lake's varved cores.
4. Eutrophic diatom indicator species disappear downcore, where they are replaced by meso- and oligotrophic indicators. In addition, pollen from exotic trees planted in the lake's catchment appears at specific core depths associated with their pollen production stage.     

The Genus Leptotheca (Protozoa: Myxosporida) in Macrourid fishes and Sablefish,Anoplopoma fimbria*

SYNOPSIS. Five species of Leptotheca, one new, were found in the macrourid fishes and the sablefish, Anoplopoma fimbria. Those species which were geographically widespread in numerous host species showed little variation. Two Leptotheca species were found both in the gall bladder and urinary bladder/kidney.     

Atmospheric nitrogen deposition explains patterns of plant species loss

Atmospheric nitrogen (N) deposition across Europe increased substantially from the 1950s to the 1990s. Targeted surveys suggest a negative correlation between N deposition and species richness within quadrats in sensitive habitats. However, it remains unclear whether plant species losses at national recording scales are correlated with nitrogen deposition. We relate plant species losses before 1987 in Great Britain to reduced and oxidized N deposition, land use change and climate change. The mean Ellenberg fertility (N) indices of plant species lost in each 100 km² cell before 1987 was compared with those of species that were recorded between 1987 and 1999. In 45% of squares, indices of species lost were significantly lower than those for species present after 1986. For 17%, primarily upland, squares, the opposite effect was found. A generalized least squares regression model, with difference in the mean Ellenberg N index between samples as the dependent variable, showed that higher deposition of reduced N was significantly associated with selective loss of species with a lower index. Arable land use and change in arable land use also demonstrated this positive relationship. Rough grazing, change in rough grazing, change in pasture and change in annual precipitation showed negative effects. Difference in Ellenberg R index was highly correlated with difference in Ellenberg N and was negatively correlated with oxidized N deposition, suggesting that the lack of a significant effect of oxidized N deposition on Ellenberg N was because it had effects through both acidification and eutrophication, while the effect of reduced N deposition was primarily through eutrophication. Our results suggest that N deposition, along with land use and precipitation changes, has been a significant driver of local plant extinctions. With N deposition increasing in many parts of the world, local extinctions of plant species may be experienced in other regions.     

Selection of aphid prey by a generalist predator: do prey chemical defences matter?

1. For predators, prey selection should maximise nutrition and minimise fitness costs. In the present study, it was investigated whether a generalist predator [Chrysoperla carnea (Stephens) lacewing larvae] rejected harmful, chemically‐defended prey [Brevicoryne brassicae (Linnaeus) aphids] when non‐defended prey [Myzus persicae (Sulzer) aphids] were available. 2. It was tested: (i) whether consuming different prey species affects predator mortality; (ii) whether naïve predators reject chemically‐defended prey while foraging when non‐defended prey are available; (iii) whether the relative abundance of each prey affects the predator's prey choice; and (iv) whether predators learn to avoid consuming chemically‐defended prey after exposure to both prey species. 3. Consumption of B. brassicae yielded greater C. carnea mortality than M. persicae consumption, but naïve C. carnea did not reject B. brassicae in favour of M. persicae during foraging. When presented at unequal abundances, naïve predators generally consumed each aphid species according to their initial relative abundance, although, predation of non‐defended prey was less than expected when defended prey were initially more abundant, indicating a high consumption of B. brassicae impeded M. persicae consumption. With experience, C. carnea maintained predation of both aphid species but consumed more M. persicae than B. brassicae, indicating a change in behaviour. 4. Although prey choice by C. carnea may change with experience of available prey, prey chemical defences do not appear to influence prey choice by naïve predators. This inability to avoid harmful prey could facilitate wider, indirect interactions. Myzus persicae may benefit where high consumption of B. brassicae hinders predators in the short term, and in the long term, increases predator mortality.