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No description available.

During a two-year field study, the ecology and reproduction of mountain hares was investigated to determine which factors are important determinants of the season of production of young. Two approaches were adopted. 1) A live-trapped, marked population of hares was maintained to provide information on the seasonal appearance, growth and survival of leverets. 2) Throughout December 1983 to March 1985 a sample of carcases was obtained in each month to provide information on reproductive performance. Blood samples were obtained from carcases and from the live population to provide information on seasonal changes in hormone levels. A rapid method of ageing mountain hare carcases was developed; this involved polishing mandibular sections by a geological method and counting periosteal growth lines.The photoperiodic control of seasonal reproduction acting through the pineal organ and its secretion of melatonin, was confirmed for the mountain hare. A radio-immunoassay for this hormone has been validated for mountain hares and samples from wild animals indicate that there is a marked circadian pattern of plasma melatonin concentration. This pattern varied with season in a manner consistent with changes in photoperiod and was confirmed by two sets of serial blood samples from captive animals under two widely different natural photoperiods.In 1984 females produced up to 3 litters. Larger females produced more offspring in total because they were successful at the first as well as the second and third litters. Early production of offspring resulted in diminished production in the final litter of the year. Small females were less likely to produce early offspring. Females in their first breeding year suffered heavier pre-natal losses of ova or embryos, especially during the first litter period. Male leverets, especially those born late in the breeding season, grew at faster rates than females. Despite this faster growth rate they reached lower asympototic skeletal sizes and body weights by ceasing growth sooner. Current theory suggests that fast growth rate and longer duration of growth produce increased juvenile mortality. There is no clear sex bias in mortality in mountain hares and it is suggested that the hypothesised mortality-producing agents cancel each other, the former acting on males and the latter on females. Late-born young reached smalled asymptotic body sizes than those born earlier and they were more likely to die after weaning. It is of considerable advantage for mountain hares to successfully breed early rather than late. Early born young are of higher quality than late-born; they reach greater body sizes which are associated with greater post-weaning survival and in females a greater reproductive success.Chemical and botanical analyses of stomach contents showed a clear seasonal switch in utilisation of the two major food types; heather (<i>Calluna vulgaris</i>) and grasses. On average most grasses were ingested in the summer months of April-August but some animals continued to eat them until October. Changes in plant selection could not be explained by selection for protein or against acid detergent fibre. The seasonal pattern of plant selection is commensurate with avoidance of phenolic secondary plant compounds present in heather particularly during the summer. Reproductively active females and to a lesser extent growing leverets, avoided ingesting plants containing these compounds. The season of production of young may be restricted by the availability of forage with low levels of secondary compounds.

Vanadium is present in natural waters predominantly as the orthovanadate anion V03/4- in concentrations of about 10⁻⁸M. Orthovanadate perfused through the gills of fresh water or sea water adapted eels induces vasoconstriction at concentrations as low as 5 x 10⁻⁸M. The pillar cells of the respiratory lamellae and the afferent and efferent blood vessels of the gill filament are affected by orthovanadate. If orthovanadate 5 x 10⁻⁸M is perfused through the gills of sea water adapted eels, the outfluxes of Na+ and Cl- are significantly reduced. Vanadium is taken up by young eels (elvers) in a manner dependent on the concentration of orthovanadate in the environment over the range 10⁻⁸-10⁻⁵M. Vanadium is deposited in the kidney, liver, bone, blood and skeletal muscle. An environmental concentration of 10⁻⁴M orthovanadate is rapidly toxic to elvers causing death within 7-26 days of exposure. Elvers loaded with vanadium through 2 months exposure to 10⁻⁵M orthovanadate show little sign of depleting their vanadium burden after 5 weeks exposure to 10⁻⁸M orthovanadate. The eel intestine is the main site of entry of vanadium into the eel, gill contributes <5% of the total uptake of orthovanadate by the eel. The influx of orthovanadate across eel intestine is dependent on the concentration of orthovanadate in the external environment. The results are discussed in relation to the published literature on the physiological and biochemical actions of vanadium and the extent to which vanadium might be an environmental hazard is assessed.

The ranging patterns and the habitat use of adult European roe deer (<I>Capreolus capreolus</I>) in a mixed wood/agricultural Mediterranean habitat in central Italy were examined by radio-tracking in a high density non-hunted population, between November 1995 and December 1997. Seasonal changes in range size were significant only when considering 100% of locations; males (<I>n</I> = 9) occupied largest ranges in January-February and smallest ones in September-October, whereas females (<I>n</I> = 9) had largest ranges during November-December and minimum ranges during May-June. The two sexes occupied different range sizes only during May-June, when males had larger ranges. For both sexes, there was no seasonal variation in core area size; neither were there differences in core area size between males and females at any time of the year. There was no seasonal change in diurnal inter-fix distance travelled by males or females. Neither were there seasonal changes in crepuscular inter-fix distance travelled by males. Females travelled shorter crepuscular inter-fix distances in May-June than in the winter months. Both sexes showed significant seasonal trends in their inter-fix distances travelled at night, with longest distances travelled in July-August and shortest ones travelled in autumn and spring for males and females, respectively. Males always travelled significantly longer inter-fix distances than does in spring, but did so only at night in summer. Marked deer spent significantly more time than expected in woodland habitat during the day, and in open fields habitat during the night, in any season. Within woodland, both males and females were found significantly more than expected in the interior rather than at the edge during the day, but not during the night. Both sexes preferred wood interior and wood edge during daytime, and avoided wood edge during night-time in any season. The two sexes showed opposite habitat preferences in spring, when males selected wood interior and females selected open fields during the night. Within fields, short herbs were always the preferred habitat of both sexes in any season, except during May-June when males and females showed avoidance during night and daytime, respectively. In daylight, both sexes selected cereals when they provided cover, but only males selected this crop type at night, during May-June. Ploughed fields were always avoided by all marked animals in any season.

The aim of this PhD-thesis is to develop techniques which can be used to analyse spatio-temporal ecological data sets. Central questions are: A. What are the relationships between species abundances and spatial environmental variables in a particular year? What are relationships between species? B. How do these species-environmental relations and species interactions change from year-to-year? What is the effect of global environmental variables on these year-to-year variations? The thesis is divided into two parts. In Part I, we concentrate on the first question. We discuss the state-of-the-art technique <I>canonical correspondence analysis </I>(CCA). Using assumptions which are unlikely to hold in practice, Ter Braak (1986) showed that CCA estimates certain parameters of the 'restricted Gaussian response (RGR) model'. This model describes species abundances as a unimodal, symmetric function along a gradient. The key feature in CCA and RGR is that the gradient is a linear combination of environmental variables. Using numerical optimisation routines, we show that the parameters of the RGR model can easily be estimated. This has considerable advantages over CCA, because <I>all </I>parameters are estimated in a <I>regression </I>context, without making doubtful assumptions. RGR is applied on various data sets. A model validation indicates that for some species the model is inappropriate. For this reason, we develop a smoothing model in which the covariate is a linear combination of environmental variables. It is called restricted generalised additive modelling (RGAM). In Part II, we concentrate on question B. We develop a new technique, called <I>dynamic generalised additive modelling. </I>For each species a smoothing function and a stochastic trend are estimated.

This study described the behavioural ecology of wild boar in a Mediterranean coastal area, with particular reference to its diet, home range, activity patterns and habitat use. Food use, derived from the analysis of faeces, was compared to the availability of the main food resources. The results showed that boar selected energy-rich food items such as acorns, olives and pineseeds, and relied mainly on graminoids when these resources were not available. Olives and acorns were used according to their availability, whilst pine-seeds were heavily searched for even when their production was low. The availability of pine-seeds, acorns and olives was unpredictable; as a consequence, the diet of the wild boar in the MNP showed no seasonal pattern, depending on the temporally available food items. The greater production of energy-rich food items in 1991-92, and the low availability of these foods in the following two years, was likely to have influenced body weights of boar, number of females breeding and litter size. The lack of high-energy food in winter 1992-93, the drought that hardened the soil in the following months and hampered rooting activity, together with the increased population density, were probably the main factors responsible for mortality amongst boar. Radiotelemetry allowed the estimate the home range size, activity patterns and habitat use. The results showed that home range decreased and the amount of activity increased during 1993, characterised by food shortage, high density of boar and high mortality. It was suggested that wild boar adopted strategies to cope with starvation and drought by (i) drastically reducing the size of their home range whilst slightly increasing the amount of activity for foraging in a smaller area, and (ii) shifting to habitat types, like meadows and olive-groves, that provided the only available food i.e. graminoids. No sex-related differences in home range size were found in this study. This finding was attributed to the fact that none of the 10 radiotracked females bred in 1993.

The aim of this study was to document the bird communities of six 'scarce forest habitats' in an upland spruce forest (Kielder, in Northumberland) and to compare them to the bird communities that were associated with its conifer plantations. Features of the scarce forest habitats considered to be important to their bird communities were investigated. The implications of these findings for future forest management are discussed, particularly in relation to the contributions these habitats make to the overall diversity of forest avifauna. Up to 76 study plots were selected randomly from six scarce forest habitat types; broad-leaved woodland, mixed broad-leafed/conifer woodland, windthrown conifer stands, streams with unplanted riparian strips, unplanted land and streams with broad-leaved riparian strips. Five-minute point counts, with up to 60 m radius, were used to estimate the relative abundance of species. Counts were carried out between 1992 and 1994, in winter (November to December), early spring (April to mid May) and late spring (mid May to mid June). Each study plot was visited once in each of these seasons, under similar weather conditions. There were few widespread species amongst the different habitats, only the chaffinch <I>Fringilla coelebs</I> was recorded consistently in more than 50% of spring plots. The commonest species in the scarce forest habitats were the same as those found in the adjacent conifer plantations. The majority of the species recorded occurred in a small proportion of plots such that variation in their numbers could not be analysed statistically. However, these less abundant species were classified arbitrarily into two groups, 'uncommon' species (occurring in only 3-10 plots in any one season) and 'occasional' species (occurring in only 1-2 plots in any one season). Unplanted riparian strips held greater numbers of these species during the spring than did the other scarce forest habitats.

No description available.

No description available.