Consumption of natural foods, digestibility, assimilation level, and diurnal energetic requirements were studied in two species of voles (Microtus arvalis, Clethrionomys glareolus) and two species of mice (Apodemus agrarius and Apodemus flavicollis). Eleven concentrated, compound, and bulky diets were examined. For each series 10-15 animals were used. Experiments were carried out in metabolic cages with the aid of the balance method. Coefficients of digestibility for dry matter in concentrated diets (beechmast, acorns, hazel-nuts, oats) reached from 84.3% up to 93.5%, while in compound diets (hazel-nuts and ground vegetation) from 80.9% up to 85.5%. Digestibility of dry matter for bulky food was lower in C. glareolus and M. arvalis and amounted on an average to 73.9%. Energetic losses in faeces when compared with the energy taken in food fluctuated from 7.1 to 22.6, while in urine -from 0.7 to 5.4% depending upon diet. Assimilation level for various foods oscillated within limits from 65.2 to 90.9% of the energy taken with food. Diurnal energetic requirement calculated from assimilated food amounted to 0.432 kcal/g/day in C. glareolus, to 0.462 kcal/g/day in M. arvalis, 0.561 kcal/g/day in A. agrarius, and to 0.387 kcal/g/day in A. flavicollis.

The investigations of the intake and digestibility of natural feeds in the year cycle were carried out by the balance method on 3 individuals of roe-deer, Capreolus capreolus. Season-depending changes in the chemical composition of natural food were ascertained: total protein amounted to 8-9°/o in winter and to 16-19°/o in summer, while the fibre content was the highest in winter feeds (30-47°/o). The food intake ranged from 350 g of dry matter in winter to 600 g d.m. in summer, these values corresponding to 1300-2800 kcal/day. The digestibility of dry matter varied with season and chemical composition of food, being the highest in May (87%>) and the lowest in January (34%). A clear relationship was found to exist between the digestibility and fibre content and food intake. The intake of digestible energy by roe-deer in winter ranged from 70 to 102 kcal/kg 0 -75 day, while the mean intake in the remaining seasons amounted to 197 ± 53 kcal/kg 0 -75 day.

Food with minimum 58% digestibility is required to cover the energetic main tenance costs of the roe-deer. It was found that the food supply of deer in w inter depends not on the amount of browse, but on its digesti bility and the possibility of supplem enting it by easily digestible foodherb layer plants, grass or leaves.-[Jagiellonian Univ., Dept. Anim. Ecol., Karasia 6, 30-060 Kraków] INTRODUCTIONR ational h u n tin g m anagem ent involves definition of w h a t is know n as th e food carry in g capacity of a given h a b ita t , and to define this it is essential to have data on th e population's" consum ption level and food supply (Grodziński, 1975). W hen am ount of production and n a tu ra l food supply, and also consum ption, are known, it is possible to evalu ate th e d irect effect of th e population on the h a b ita t and to a rriv e a t decisions to m ain tain th e optim um n u m b er of individuals in a given area. T he studies m ade up to th e p resen t on the food supply of deer, carried out from th e aspect of am o u n t of biomass, d ry m a tte r or energy of th e food produced per u n it of area (DziQciolowski, 1970;Bobek et al., 1972;Bobek et al., 1975) are insufficient. The n a tu ra l food of d e e r is subject to considerable variations during the y early cycle, both in respect of chem ical com position and n u tritiv e value, and th erefo re intensive studies aim ed a t defining its q u ality a re essential. The n u tri tive value, and not th e am ount of food available, determ ines th e level of consum ption and its utilization by anim als (Nagy et al., 1969; M orris&Kovner, 1970; A m m a n n et al., 1973). The q u a lity of food also determ ines ra te of grow th (Newsome et al., 1968; U 11 r e y et al., 1967;Nordan et al., 1970), breeding success (N o r d a n et al., 1968), the an im al's condition, length of life, and ability to survive th rough u nfavourable w in ter conditions (U r n e s s et al., 1971).N u tritiv e value should therefore, in addition to estim ation of th e n a tu ra l food supply, be th e basic criterion for evaluating the food carrying capacity of the h a b ita t for deer. A m easure of th e n u tritiv e value of food is, according to Barnes (1965), its chem ical com position and digestibility. These tw o p a ram eters also e x e rt a decisive influence on th e an im als' food preferences in relation to d iffe re n t p lan ts (Van Dyne & Heady, 1965) and also of p arts of such plants .D eterm ination of th e digestibility of n a tu ra l food over th e y early cycle perm its of estim ating th e food supply for anim als in th e given area in categories of th e sum total of total digestible n u trie n ts (TDN), digestible energy (DE), or d ry m a tte r digestibility (DMD), w hile a know ledge of th e relatio n betw een food digestibility and its v o lu n tary intake (VI) p erm its of evaluating th e possibility of supplying th e energetic cost of th e an im als' m aintenance, depending on th e food c u rre n tly available.T he classic tim e-consum ing m ethod, invol...

IWith 7 Tables & 7 Figs.]Oxygen consumption was determined in the fat dormouse, forest dormouse and common dormouse in late spring and early summer, and in autumn. Since 24-hr measurements were obtained the activity of these animals could be also evaluated. Moreover, food consumption of the fat dormouse was determined in spring. Considerable seasonal differences metabolic rate were observed. Cost of maintenance as estimated from food consumption is slightly higher than -that calculated from oxygen consumption. The daily energy budget (DEB) was computed for all 3 species. DEB of hibernating rodents in the period of their active life appears identical with that of non-hibernating animals. In an attempt to estimate annual cost of maintenance it was calculated that in the half-year hibernation period, these species consume less than 10% of their total annual energy budget. CONTENTS

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