Influence of Meadow Mouse Populations on California Grassland
TL;DR: The influence of meadow mouse populations on grass—land ecosystems was studied at two sites with similar densities of Microtus, but in different types of grassland–a coastal prairie and an inland valley grassland.
Abstract: The influence of meadow mouse (Microtus californicus) populations on grass—land ecosystems was studied at two sites with similar densities of Microtus, but in different types of grassland–a coastal prairie and an inland valley grassland. Height of vegetation, volume of standing crop, and percentage cover were greater at the dry inland site where the annual grass Bromus rigidus was dominant. At the milder coastal site the annual grass Lolium multiflorum and the perennial bunchgrass Danthonia californica were dominant; forbs and other perennial grasses were more important. During a year with high rainfall and moderate densities of Microtus (1967) total standing crop, average height of vegetation, and weight of seed crop at the coastal site increased. Although 1966 and 1968 were both dry years, standing crop, seed production, and volume and cover of vegetation were less in 1968, when the meadow mouse population was high, than in 1966, when it was low. Exclosure studies demonstrated that these vegetation chan...
Citations
More filters
TL;DR: This chapter summarizes the current information on population cycles in small rodents, and first looks at the general questions about cycles, and then discusses the demographic machinery which drives the changes in numbers.
Abstract: Publisher Summary This chapter summarizes the current information on population cycles in small rodents It first looks at the general questions about cycles, and then discusses the demographic machinery which drives the changes in numbers And finally, analyzes the current theories which explain population cycles in rodents Population cycles in voles and lemmings are accompanied by a series of changes A few of them include fluctuations occurring in a variety of genera and species from arctic to temperate areas, from Mediterranean to continental climates, from snowy areas to snow-free areas Populations living in a wide variety of plant communities in a small geographic area all fluctuate in the same way, often in phase Survival of adult males fluctuates independently of that of adult females, when viewed on a weekly time scale Males may suffer heavy losses in the decline for a few weeks when females are surviving very well, and vice versa
856 citations
TL;DR: Herbivores are taxonomically and ecologically diverse, ranging in size from microscopic zooplankton to the largest of land vertebrates, and affect plant communities in many ways.
Abstract: Herbivores are taxonomically and ecologically diverse, ranging in size from microscopic zooplankton to the largest of land vertebrates. Aquatic grazers include zooplankton (28 , 182) , larger invertebrates such as snails, insects, and crayfish, and vertebrates such as waterfowl, tadpoles, fish, muskrats, and moose ( 1 1 , 27, 73, 1 15, 162, 1 63). Insects and mammals are the most conspicuous terrestrial herbivores (2, 46-49, 125) , but nematodes (20), crustaceans ( 152), molluscs (78) , birds, and reptiles (69) can also be signifi cant. Marine ecosystems are grazed primarily by crustaceans (57, 79, 1 12 , 143), molluscs (15 , 126), fish (83 , 84, 92), echinoderms (24, 25 , 65), and a few insects ( 170) , reptiles and mammals ( 123, 185). These herbivores affect plant communities in many ways. Feeding selectiv ity and feeding modes are highly varied; the terrestrial insect herbivores alone include phloem and xylem feeders, root grazers, gall formers, and folivores that mine, chew, roll, rasp, or pit leaves ( 1 94). Herbivores may select among plant parts, individuals, species, patches, and portions of landscapes (7 , 55 , 83 , 95 , 120, 126 , 137, 138 , 140). Many herbivores also clip or tear loose much plant biomass that is not consumed (5 , 70, 104, 105 , 122, 169). Herbivores change the environment by their trails, burrows, wallows, den building, foraging, social behavior, and other activities ( 1 , 4, 15, 40 , 50, 53 , 94, 96, 98 , 138, 148 , 165 , 167, 177). They convert plants into dung, frass,
756 citations
TL;DR: The chapter introduces the most important currently applied methods in assessing stress levels in animals and the focal points of the chapter are the sympathetico–adrenomedullary and pituitary-adrenocortical systems, the pituitsary–gonadal axis, and the immune system.
Abstract: Publisher Summary This chapter discusses the significance of the stress concept in gaining a better understanding of social mechanisms in nonhuman mammals The development of this concept during the past years and the resulting present understanding of different stress reactions are described in the chapter The triggers of stress reactions are mainly psychical processes resulting from the assessment of a situation by an individual Dependent on the coping behavior of the individual, these processes lead to different physiological response patterns, which can result in a number of pathophysiological effects The chapter introduces the most important currently applied methods in assessing stress levels in animals Particular attention is paid to methodological problems, as well as to the limits of interpretation The focal points of the chapter are the sympathetico–adrenomedullary and pituitary–adrenocortical systems, the pituitary–gonadal axis, and the immune system An overview of the relationships between social situations and stress responses is provided, in which the research focuses on the monogamous and territorial tree shrews and the polygamous and territorial European wild rabbits In these cases, the social rank of an individual, its sociopositive interactions with conspecifics, and the stability of the social system are determinants in the effects of a social situation on the individual's vitality and fertility
406 citations
TL;DR: A short review of cellular automata models in ecology is given in this article, where the authors model population dynamics of three plant species on a lawn and compare two STMC models of different order.
307 citations
Cites background from "Influence of Meadow Mouse Populatio..."
...Batzli and Pitelka (1970) exclude small rodents (meadow mice) from grasslands in California and find that, in the two years following exclosure, food plants like Lolium multiflorum and A!ena fatua contribute $60% to the vegetational volume on areas without grazing but &30% on grazed areas....
[...]
TL;DR: A hypothesis is presented that a site-dependent threshold level of vegetative cover is necessary for a population of Microtus to increase in numbers sufficiently to undergo a multi-year cycle.
Abstract: A hypothesis is presented that a site-dependent threshold level of vegetative cover is necessary for a population of Microtus to increase in numbers sufficiently to undergo a multi-year cycle. The hypothesis is supported by results of studies in grassland habitats in the tallgrass prairie of Oklahoma and Minnesota, the mixed grass prairie of South Dakota, and the shortgrass prairie of Colorado. Levels of cover below the threshold sometimes support resident, breeding populations of voles. Levels above the threshold may influence amplitude, duration, and synchrony of Microtus cycles.
278 citations
References
More filters
Book•
01 Jan 1935
TL;DR: Manual of the grasses of the United States as discussed by the authors, Manual of the Grasses of United States, Manual of Grasses, United States of the USA, 1998, Section 7.1.
Abstract: Manual of the grasses of the United States , Manual of the grasses of the United States , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
1,182 citations
05 Jul 2017
TL;DR: In this article, the authors discuss ways of testing the hypothesis that all species of animals have a form of behavior that can prevent unlimited increase in population density, and they suggest that a common class of events is involved.
Abstract: This chapter discusses ways of testing the hypothesis that all species of animals have a form of behavior that can prevent unlimited increase in population density. Selective advantage is measured in terms of relative contribution to the gene pool of later generations; hence a form of behavior that reduces an individual’s absolute contribution would nevertheless be selected for if at the same time it reduced still further the contribution of other individuals. Territorial behavior probably has many functions that are not selected for, and in some instances perhaps its only selective advantage is in excluding other animals from the best breeding places. Although there are many differences between populations, yet where enough data are available they suggest that a common class of events is involved. Not only are these declines recurrent phenomena, but they are attended by characteristic changes in the distribution of body weights and survival rates.
406 citations
TL;DR: The primary objectives of the study were to determine the rate of synthesis of organic matter by the primary producers-the vegetation, the path of this energy from the vegetation through the mouse to the weasel, and the losses of energy at each step in the food chain.
Abstract: In recent years there has been a growing interest in the study of the transfer of energy through natural systems (ecosystems, Tansley 1935) Park (1946) stated that "probably the most important ultimate objective of ecology is an understanding of community structure and function from the viewpoint of its metabolism and energy relationships" Aquatic biologists have taken the initiative in the study of comillunity energetics, and most of the information available today concerns fresh water or marine communities A great need exists for similar studies on terrestrial communities In this study a food chain of the old field comnmunity, from perennial grasses and herbs to the meadow mouse, Microtus pennsylvanicus pennsylvanicus Ord, and to the least weasel, Mustela rixosa allegheniensis Rhoads, was chosen for investigation This food chain included the dominant vertebrate of the conlinunity (Microtus) and one of its main predators (Mustela) but excluded the otherwise important insects, other invertebrates, bacteria, and fungi The primary objectives of the study were to determine (1) the rate of synthesis of organic matter by the primary producers-the vegetation, (2) the path of this energy from the vegetation through the mouse to the weasel, and (3) the losses of energy at each step in the food chain The writer wishes to acknowledge with gratitude the suggestions and guidance of Dr Don W Hayne, Institute of Fisheries Research, Michigan Department of Conservation, especially concerning that portion of the study dealing with the population dynamics and productivity of the Microtus population The writer also thanks Dr John E Cantlon, Department of
244 citations