No abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. . Wiley and Nordic Society Oikos are collaborating with JSTOR to digitize, preserve and extend access to Oikos. . Energy values of tree-seeds eaten by small mammals. -Oikos 21: 52-58. Copenhagen 1970.Caloric values were determined for 19 European tree-seeds (5 conifers and 14 deciduous), which constitute a potential food for mammals. With respect to weight these seeds may be divided into four groups: very light (birch, alders), light (larch, elm, pine, spruce, black locust, lime), heavy (hornbeam, fir, ash, maples, beech, stone pine), and very heavy (hazel and oaks). The nutritive content (seeds minus coats) varies from 24 to 85 % of the whole seed dry weight.There is no correlation between the seed size and nutritive content. The caloric value of whole seeds ranged from 4.4 to 6.8 kcal/g dry wt, with the highest values for conifers, beech and hazel (6.0-6.8), while the majority of deciduous seeds have a value of 5.0-5.3 kcal/g. The energy value of nutritive material exceeded that of the whole seeds and amounted to 4.4-7.9 kcal/g dry wt. Ash-free caloric values were higher by 1-7 %. Energy values of seeds are directly correlated with the lipid content.Most of these seeds are favorite foods of rodents (voles, mice, dormice, squirrels), although some of them are also eaten by shrews, as well as deer and wild boar.

The aim of investigations was to elaborate an accurate and laboursaving method of estimating the numbers of small rodents. Each of 8 two-week series of captures consisted of: (1) a seven-day period of prebaiting the rodents on an area of 5.76 ha, over which a grid of 256 points with bait was arranged and (2) a seven-day period of intensive removal of rodents by means of snap-traps, two of which were set on each point. No correlation was found between the number of baits consumed and the number of rodents on a given point. From 78-100 per cent of all rodents captured over a seven-day period were removed by the fifth day. Differences were found in the rate of removal of different species of rodents and of marked and unmarked individuals of the same species. Estimate of population numbers was made by the regression method, obtaining satisfactory results in 17 cases out of 18 possibles. This method is recommended, but it is suggested that the prebaiting and removal periods should be shortened to five days each.

Results of quantitative sampling of small mammal populations at different grassland sites for a 3-yr period are compared to evaluate the energy requirements and consumption, according to trophic levels, for total small mammal communities at all seasons in different years. The purpose was to search for patterns of food utilization by these consumers at the different sites. This picture of the bioenergetics of small mammal populations over a wide range of grassland sites was constructed from extensive US/IBP Grassland Biome diet and population data and from physiological information out of the literature. The work represents one step in the process of understanding the role of consumers in the ecosystem.No species occurs at all sites and different trophic strategies predominate among the small mammals at each site: Microtines (herbivores) dominate the tallgrass prairie, sciurids (omnivores) dominate the northern shortgrass prairie, and heteromyids (granivores) dominate the bunchgrass and desert grasslands. Other groups occur at these sites and vary in their importance.At the tallgrass and midgrass sites the small mammal populations are largely dependent on herbage consumption, while at the northern and southern shortgrass prairie sites the rodent fauna is largely dependent on invertebrates. The most uniform distribution of resource utilization by this component of the consumer community occurs at the desert grassland site, where herbage, seeds, and animal matter are all utilized. Relative to the total amount of consumable herbage available (that actually utilized by the small mammal population), this resource is only slightly utilized (from a fraction to a few percent of available). Animal matter, largely invertebrates, is highly utilized at most sites and may in fact be a limiting factor on small mammal populations.The energy consumed by the small mammal population was greatest at the tallgrass prairie site, where the average annual consumption was 172 X 10 3 kcal/ha (= 720 MJ/ha). However, efficiency of biomass support was greatest at the northern shortgrass prairie site, where consumption of 32 X 10 3 kcal/ha (= 134 MJ/ha) supported proportionately more biomass (277 g live wt./ha) of animals than at the tallgrass site (935 g/ha).The estimates of population energy requirements presented here compare well with other available estimates. These results emphasize the great between year and site variability, however. Daily population respiration in summer may be as little as 14 and as large as 1,038 kcal · ha-1 • day-'. Highest small mammal biomass occurred at the tallgrass (3,075 g live wt./ha) and the desert (2,304 g/ha) sites, and lowest at the midgrass (14 g/ha) site. Within the period of study, small mammal biomass was most stable at the southern shortgrass site and most variable at the tallgrass site.The role of small mammal populations in grassland ecosystems remains incompletely defined. A broader view of the total consumer community in relation to resources is required.

The prim ary n et production an d th e n u m b ers of sm all m am m als w ere estim ated in a w h ite spruce forest (Ptcea plauca). D aily m etabolic rates and food h abits w ere stu d ied in th e voles (C lethrionom ys ru tilu s, M icrotus oeconomus), sq u irrels (Tam iasciurus hudsonicus, G laucom ys volans) and shrew s (Sorea: cinereus). P ro d u ctio n of th is taiga fo rest am ounts to only 10.2 m illion k c a l/h a y*ar. Due to d ifferen t food h ab its of sm all m am m als th eir to tal food available in th e fo re st reaches as m uch as 1,320,000 kcal/ha (i . e. 12.EK>/0 of p rim ary production). Daily energy budgets described by functions of body size give th e follow ing m ean values: S. cinereus -8.3 kcal, C. ru tilu s -12.2 kcal, M. oeconom us -15.1 kcal, G. sabrinus -39.6 kcal and T. hudsonicus -58.4 kcal/day. The m ean num bers of sm all m am m als w ere found to be ab o u t 15 voles of b oth species, 2-3 sq u irrels an d 4 shrew s p e r 1 h ectare. T he total an n u a l production of these populations w as estim ated as approx. 2,500 kcal/ha, th e ir assim ilation -143,900 kcal, an d consum ption -178,600 kcal. D uring th e populatio n cycle of voles an d sq u irrels all these values can flu ctu ate w ith in a broad ran g e; production 600-8,000, assim ilation 38,000-400,000, consum ption 47,000-500,000 kcal/ha year. In d ifferen t years sm all m am m als m ay th e re fo re consum e from 3 to 38tyo of the p o te n tia l food supply provided by th e taiga forest. T hese values are considerably higher th a n those found in any other w oodland.