摘要:

AbstractThe Mammal Society has co‐ordinated a population survey of Wood MiceApodemus sylvaticusand Bank VolesClethrionomys glareolusin 13 0.81 ‐hectare sites in Britain. Numbers of mice and voles live‐trapped using standard methods were collated every May/June and November/December from 1982 to 1987. The data were analysed with results from four independent studies in England and the corresponding assessments of tree seed crop size. Wood Mouse numbers are usually higher in winter than in summer but Bank Vole fluctuations are less regular. In deciduous woodland, Wood Mouse mean relative densities are significantly greater in the winter and the following summer after a good seed crop than after a poor one; rates of population change from summer to winter are significantly higher when a good seed crop falls. Bank Vole relative densities are significantly greater in the summer following a good seed crop than after a poor one, and rates of change from winter to summer are significantly higher. In Wood Mouse populations, tests for density dependence suggest that it is strong from summer to winter but absent from winter to summer; in Bank Voles weaker density dependence is present in both halves of the year. Thus, Wood Mouse numbers are regulated in autumn but are also influenced by seed crop size in winter and the following summer; Bank Vole numbers are less strongly regulated during both autumn and spring and are influenced by seed crop size in the following summer. Evidence is presented suggesting that populations of each species in deciduous woodlands are synchronized over the country in summer and that Wood Mice are also synchronized in winter; highs and lows tend to coincide between different sites. The yield of tree seed is shown to vary significantly from year to year and may be the cause of the synchrony, but weather effects may also be inv

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1994.tb00131.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractUltradian activity rhythms are a peculiar behavioural pattern, in which the 24‐h day is divided into several short‐term activity cycles. Such patterns are particularly prominent in microtine rodents. In this paper we review experimental findings and proposed hypotheses on the proximate triggering mechanism of ultradian rhythmicity. Eight different mechanisms (classified as homeostatic, pacemaker and stochastic hypotheses) were analysed within the same theoretical model‐framework, considering feeding, food processing, energy turnover and activity behaviour.Ultradian activity patterns could consistently be generated by each of the analysed models. None of the models, however, resulted in frequency dependencies in respect to body weight, metabolic rate, food quality and food deprivation, unless additional assumptions were introduced.From our model evaluations we concluded that the stochastic model does not represent an independent hypothesis. Hence, only homeostatic and pacemaker hypotheses remained as alternative approaches to the triggering mechanism. Although the pacemaker hypothesis appeared more reasonable, a combination with some feedback mechanism to metabolism seemed even more likely. Some key experiments are suggested, which could give insight into the complex mech

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1994.tb00132.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA Rabbit survey of Scotland was carried out in 1991 following the methods used for previous surveys in 1969, 1970, 1973 and 1974. The survey was split into direct field and postal questionnaire sections, and the results from the two were compared. Rabbit infestations were categorized as slight and serious. Slight infestation proved to be an inconsistent indicator of Rabbits, but the percentage of serious infestations was highly correlated across sampling areas, and was also related to the average loss estimated by farmers. The pattern of recovery of Rabbit populations after myxomatosis varied between different parts of the country. In the East, Northeast and eastern Highlands the percentage of serious infestations was 26.5% in 1991, as compared to previous survey estimates of 55.9% before 1954 and 1.5% in 1969/70. In the Central, West, South and South‐west serious Rabbit problems disappeared after 1954 and are now only at the level of 5 %. It is estimated that Rabbits caused £11,790,000 worth of damage to agriculture in Scotland during 1990/

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1994.tb00133.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY