Ground Roost Resource Selection for Merriam's Wild Turkeys

ABSTRACT Concealment cover is important for ground-roosting wild turkey (Meleagris gallopavo) poults immediately following hatch during the vulnerable, preflight stage. We compared concealment cover resources selected at ground roosts to those of nest sites and available resources for Merriam's turkeys (Meleagris gallopavo merriami) in the Black Hills of South Dakota, USA. Females with preflight poults selected ground roosts that were similar in structure to nest sites. Ground roosts and nests were greater in visual obstruction (unit odds ratios ≥1.19) than random sites. However, ground roosts were closer to meadow-forest edges than either nests or random sites (unit odds ratios ≤0.98). Structure at ground roosts may provide visual protection from predators, and management for shrub vegetation or woody debris along meadow-pine forest ecotones will provide cover for Merriam's turkey broods.     

Changes in haematological parameters in relation to prey switching in a wild population of harbour seals

1. Previous studies have found marked inter-annual variation in winter food availability, diet composition and body condition in a population of harbour seals ( Phoca vitulina L.) in Northeast Scotland. This study aimed to determine whether there were other physiological consequences of prey switching by comparing haematological parameters in years when the clupeids herring and sprat dominated the diet and in years when seals switched to alternative prey.
2. There were significant differences in leukocyte and erythrocyte parameters in relation to diet composition. In contrast, indices of body condition did not explain the variation in haematological parameters, suggesting that the observed changes did not result from differences in the energetic content of the prey.
3. Leukocyte counts were significantly higher after 'good' clupeid years, although the differences in mean counts were small. Such differences could have resulted either from immuno-suppression, for example because of differences in prey nutrient or contaminant levels, or from differences in the pathogen challenge resulting from geographical variations in water quality.
4. The differences in erythrocyte parameters were more marked, and there was evidence of widespread macrocytic anaemia when seals switched from clupeids to alternative prey. Such differences could result either from acclimation, as a result of prey-specific foraging strategies, or from differences in the nutritional quality of prey.
5. These results indicate that generalist predators such as the harbour seal may exhibit physiological responses to changes in the composition of their diet. These data highlight the need to consider the long-term physiological effects of variations in food availability on the population dynamics of generalist marine top predators. In particular, it is hypothesized that fish-induced anaemia may be responsible for declines in certain pinniped populations.     

The effects of temperature and prey density on the development rates and growth of damselfly larvae (Odonata: Zygoptera)

Abstract. 1. The effects of prey density and temperature on the feeding and development rates of several late instars of the larvae of three common European damselflies ( Lestes sponsa (Hansemann), Coenagrion puella (L.) and Ischnura elegans van der Linden) were investigated in a laboratory experiment.
2. Functional responses were used to estimate maximum feeding rates. Maximum feeding rates were compared between species, instars and temperatures by expressing prey consumption in terms of prey biomass consumed per unit predator biomass. Lestes was capable of feeding at almost twice the rate of either Coenagrion or Ischnura.
3. Higher feeding rates led to faster development rates and there was an interaction between species and temperature. With the exception of those with very low feeding rates, larvae maintained at higher temperatures, but similar feeding rates, developed faster. Under similar conditions of temperature and feeding rate, Lestes larvae developed faster than larvae of either Coenagrion or Ischnura.
4. Faster development rates at similar rates of food intake were achieved at the cost of reduced size-increases between instars.
5. The differences in the responses of the three species are discussed in the light of their respective life histories, and with reference to a recent model of population regulation in damselflies.