Raymond Hock

Bio: Raymond Hock is an academic researcher. The author has contributed to research in topics: Arctic & Thermoregulation. The author has an hindex of 6, co-authored 7 publications receiving 2251 citations.

Heat regulation in some arctic and tropical mammals and birds

Abstract: A series of arctic and tropical mammals and birds at Point Barrow, Alaska (lat. 71° N.) and in Panama (lat. 9° N.) was subjected to various air temperatures in a respiration chamber where the heat production was determined by oxygen consumption or carbon dioxide production. The larger arctic mammals and birds showed no increase in metabolism at — 30° C. and from observations on sleeping animals it is probable that their zone of thermoneutrality extends to — 40° C. or — 50° C. The smaller arctic species show a high critical temperature and the tropical species even higher. Metabolic heat production increases rapidly with lowering of the temperature in a tropical mammal or bird, and slowly in an arctic animal. It can be shown theoretically that in a thermoregulated system with a fixed basal energy level and variable insulation the critical gradient is proportional to the maximal insulation and the basal energy level.In a large series of experiments including our tropical and arctic animals, and all animals ...

Body insulation of some arctic and tropical mammals and birds.

Abstract: Insulation measurements on raw skins from 16 arctic and 16 tropical mammals are given. There is, as would be expected, a good correlation between the thickness of the fur and the insulation. The smaller arctic mammals (weasels, lemmings) have much less insulation than the larger and overlap many of the tropical forms. From the size of a fox to the size of a moose there is no correlation between insulation and body size, they all have about the same insulation per surface area. When submerged in ice water, seal blubber retains about the same good insulation, as compared with measurements taken in 0° C. air. In the polar bear, heat transfer through the fur increases 25-50 times when submerged, because of complete wetting of the skin surface and absence of blubber. The beaver is slightly better off when submerged, as it retains an insulating layer of air in the fur next to the skin.

Adaptation to cold in arctic and tropical mammals and birds in relation to body temperature, insulation, and basal metabolic rate

Abstract: Maintenance of constant body temperature in a homoiothermic animal depends upon a balance between heat production and heat dissipation, and there are consequently three possible main avenues for climatic adaptation, (1) by body-to-air gradient, (2) by heat dissipation, and (3) by metabolic rate. There is no evidence of adaptive low body temperature in arctic mammals and birds, or high body temperature in tropical mammals and birds. The body-to-air gradient can be adapted only by means of behavioral thermoregulation (nest building, avoidance of direct sunshine, etc.). With few exceptions our adult arctic and tropical mammals and birds have a basal metabolic rate that fits the standard mouse to elephant curve, i.e., the basal metabolic rate is determined by an exponential relation to size; evidently fundamental to most animals, warm-blooded or not. The basal metabolic rate is consequently not influenced by such factors as temperature gradient and insulation which largely determine the heat loss, and is henc...

The metabolic rates and body temperatures of bats

Abstract: 1. Oxygen consumption was measured in resting little brown bats, Myotis l. lucifugus, at ambient temperatures from 0.5° to 44.0° C. Body temperature was shown to approximate the ambient level under the conditions of the experiments, so that in effect the metabolic rate was measured over very nearly this range of body temperatures.2. The function relating oxygen consumption to body temperature is not linear; the Q10 is 2.94 from 2° to 10° C., 5.54 from 10° to 20° C., 5.09 from 20° to 30° C., 1.69 from 30° to 37° C., and 2.22 from 37° to 41.5° C. The ratio between highest and lowest resting metabolic rates is 138:1; the temperatures represented are 41.5° and 2° C.3. Some notes on the reaction to temperatures very close to 0° C. are included. Bats increased metabolism over that observed at 2° C. when exposed to near-freezing temperatures. The experiment was not continued long enough to find whether or not they would eventually awake.4. The data are compared with the findings of other investigators using seve...

Pattern and Process in Macroecology

Abstract: © 2000 by Blackwell Science Ltd. All rights reserved. Issues of scale have become increasingly important to ecologists. This book addresses the structure of regional (large-scale) ecological assemblages or communities, and the influence this has at a local (small-scale) level. This macroecological perspective is essential for the broader study of ecology because the structure and function of local communities cannot be properly understood without reference to the region in which they are situated. The book reviews and synthesizes the issues of current importance in macroecology, providing a balanced summary of the field that will be useful for biologists at advanced undergraduate level and above. These general issues are illustrated by frequent reference to specific well-studied local and regional assemblages -- an approach that serves to relate the macroecological perspective (which is perhaps often difficult to comprehend) to the everyday experience of local sites. Macroecology is an expanding and dynamic discipline. The broad aim of the book is to promote an understanding of why it is such an important part of the wider program of research into ecology. Summarises the current macroecological literature. Provides numerous examples of key patterns. Explicitly links local and regional scale processes. Exploits detailed knowledge of one species assemblage to explore broad issues in the structuring of biodiversity.