J. Kamler 1,2,*, M. Homolka 1, M. Heroldová 1 & P. Literáková 2

Transcription

1 Wildl. Biol. Pract., 2011 June 7(1): doi: /wbp ORIGINAL PAPER Feeding Strategy of Wild Herbivores in Habitats of Limited Food Resources J. Kamler 1,2,*, M. Homolka 1, M. Heroldová 1 & P. Literáková 2 1 Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Brno, Czech Republic 2 Mendel University Brno, Faculty of Forestry and Wood Technology, Zemědělská 3, 61300, Brno, Czech Republic * Corresponding author kamler@ivb.cz Correspondence address: Jiří Kamler, Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Brno, Czech Republic. Phone: ; Fax: Keywords Red deer; Chamois; Roe deer; Diet; Diet quality. Abstract In the Jeseníky Mountains, Czech Republic, we studied the composition and quality of diets of red deer, roe deer and chamois as well in relation to the availability of food. The data were collected from two sites of different altitudes and food supply. The locality on ridges was covered mostly with grasses in a herb layer and was inhabited by chamois and red deer. At the valley site, raspberry, forbs and broadleaved trees were abundant and red and roe deer were present. The aim of the study was to analyze the feeding strategies of the three ungulate species in mountain habitats with limited food supply and to deduce implications for their management. (1) Botanic composition of the diets was influenced by the animals foraging specialisation and by food availability. Red deer ate grasses (> 90% by volume) on the ridges in the growing season while forbs and browse were present in substantial amount in their diet at lower altitudes. (2) The diet quality based on nitrogen content was higher in general in roe deer than in the others ungulates but during late winter the roe deer consumed the diet based on spruce needles of very low quality. The quality of red deer diet was lower in the ridge site than at the valley where the food supply was more diverse. (3) Roe deer distribution can be restricted by absence of high quality food resources in ground vegetation while red deer and chamois can use food of lower quality. (4) Winter is a critical period for all of the study species as the food is at lowest quality. The ungulate diets were similar and the possibility of competition for limited resources increased. Introduction In natural communities, in the absence of predation, the numbers of herbivores depend on the food supply and the balance between herbivores and carrying capacity of the environment is secured by autoregulation mechanisms [1]. Specialization of the individual ungulate species in certain components of food supply (concentrate selectors, intermediate feeders and grass and roughage eaters) then enables optimal and economic utilization of all accessible food sources [2]. Copyright 2011 J.Kamler; M.Homolka; M.Heroldová; P.Literáková. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Published by: Portuguese Wildlife Society.

2 Wildlife Biology in Practice 2011, 7(1) 47 However, in cultural landscapes of central Europe, these natural relations are impaired and ruminants often inhabit sites of sub-optimal food supply where some of the important food sources may be limited or even absent; sometimes they share their habitat with one or more of the introduced species and the total population density of herbivores is then close to the carrying capacity of the environment. This results in changes of vegetation structure up to destruction of the shrub layer due to grazing by herbivores and in competition for the most attractive food sources. Under these circumstances the individual ungulate species have to change their feeding strategies otherwise they can survive at lower densities in that particular area. Their diet then contains more low-quality components (especially spruce needles) than usual. Such situation has developed in the Jeseníky Mts. (Czech Republic) where red deer (Cervus elaphus), and chamois (Rupicapra rupicapra) in upper parts and roe deer (Capreolus capreolus) and red deer in lower altitudes concur. The result of the cumulative impact of their grazing is a significant suppression of dicotyledonous plants and broadleaved woody species on subalpine meadows in the summit areas of the mountains, where grazing of chamois as well as of great part of red deer population concentrates during the vegetation growing season [3]. Roe deer are usually not present in these areas, most probably due to the limited suitable food supply and high abundance of red deer, whose negative impact on roe deer has been proven [4]. In lower areas where red deer spend the winter and roe deer are present throughout the whole year, the reduction of the shrub layer is caused particularly by browsing of annual shoots during winter. The three studied ungulate species belong to two groups of feeding specialists with different diet selection. Roe deer graze the highest-quality diet components and prefers herbs and broadleaved woody species, especially in vegetation period, while the diets of red deer and chamois may contain according to food supply more grasses. In winter, particularly if the food supply is limited, the differences in diet composition between all ungulates diminish and the diets contain more and more browse [3, 4]. The objective of this paper is to analyze the feeding strategies of the three ruminant species in two different environments: 1. in the area of subalpine meadows on mountain summits; 2. in the area of secondary spruce stands at the foot of the mountains; and to evaluate their position in mutual competition for food in the habitat with limited food resources. We have tested the following hypotheses: 1) the structure of diet of individual species is in accordance with their expected diet corresponding to the respective feeding type; 2) concentrate selectors (roe deer) will prefer the high-quality components of food supply than intermediate type (red deer, chamois); 3) species that are able to effectively utilize the food sources of lower quality (red deer, chamois) will be better in adapting to habitat with prevalence of grasses than roe deer. Methods The data were collected in the central part of the Jeseníky Mts. (northeast of the Czech Republic) at two localities of different altitude and food supply.

3 48 J.Kamler et al. Feeding Strategy of Wild Herbivores in Habitats of Limited Food Resources 1. Ridges with an altitude from 1100 to 1490 m is in an area of subalpine meadows and natural spruce forests. It has a cold climate, average annual temperature 1.1 C, average annual precipitation 1225 mm. Snow cover lasts 167 days per year on average. Vegetation on the subalpine meadows was formed mostly of grasses and rushes (80% of the cover). 18% of the herb layer cover was wavy hair grass (Avenella flexuosa), the main food source of big herbivores. Blueberry (Vaccinium myrtillus) was abundant (15%), cover of dicotyledonous herbs was low (<1%). In the shrub layer there was only spruce. On their lower edge the subalpine meadows verge into natural virgin spruce stands with individuals of various ages up to 270 years, with little admixture of rowan (Sorbus aucuparia) in both tree and shrub layers. The mean cover of the herb layer was 75% with dominant blackberry (Rubus fruticosus) (28%); the cover of grasses was 11% in this locality. 2. Valley with an altitude from 700 to 900 m a.s.l. was covered with secondary spruce stands and remains of beech (Fagus sylvatica) stands with admixture of maple (Acer pseudoplatanus) and was about 3 km from the ridges. Average annual temperature at this locality is 6.3 C, average annual precipitation 698 mm, snow cover lasts 86 days per year on average. The spruce stands of years were mostly without any undergrowth, in older stands there was spruce in the shrub layer, broadleaved species were present only sparsely (less than 5%). The clear-cut areas were mostly covered with grasses from Calamagrostis genus. Wavy hair grass was significantly represented in the herb layer of the old stands (33% of the cover). The area of each of the two localities was about 500 hectares. During the vegetation season, red deer and chamois and sporadically also roe deer were present at the Praděd Mt. In winter, most of the red deer migrated 2-10 km to lower locations, including the valley locality. The chamois and red deer went down from the summit clearings to places under the lower edge of the area on the border of the natural and secondary spruce stands (around 1100 m a.s.l.). At the valley, red and roe deer were present all year round. However, most of the red deer left the area in spring and moved to higher locations [6]. In summer and autumn, red deer was abundant on ridges (20-30 individuals per km2) and its density was less than 5 individuals per km2 in the valley. In winter, ridges locality was without red deer due to high snow cover and a few animals were on slopes (< 5 ind./km 2 ). In the valley were about 25 red deer per km 2 in winter. Density of roe deer was 3-5 ind. per km 2 in the valley area in autumn and winter (unpublished data). Food supply and dietary analysis The vegetation cover was examined at the culmination of the vegetation season; at the valley locality on the clear-cut plots and in the old stands in June, on the subalpine meadows at the ridges locality in July. The cover of the individual plant species in the herb layer was recorded at partial plots of 40 m 2 (N=18 at ridges; N=19 at valley) and the vegetation composition were estimated to categories according to the main types (see Fig. 3). Samples of vegetation and faeces were collected during four seasons (spring = May, summer = July, autumn = September and winter = November to January).

4 Wildlife Biology in Practice 2011, 7(1) 49 From each season, were examined 15 samples of pellet groups from each herbivore species on botanic composition of diets and 5 samples of vegetation (simulation of browsing) of the plant species whose proportion in the diet of ungulates was over 1% of volume (1 percentage cover). Differences in the composition of the vegetation and the diets between localities and between individual ungulate species and seasons were tested by t-test. Evaluation of quality of the diet The samples of vegetation and faeces were dried in a ventilated drying chamber at 60 C and were assessed for the content of crude protein (CP), fat, crude fibre, nitrogen-free-extract and ash [5]. To compare the nutritional quality of the individual diet component was calculated the metabolizable energy (ME) [6]. Five samples of vegetation were used to assess the nutritional value of individual diet component. Differences in content of nutritional items between ungulate species were evaluated by Man-Whitney U-test. The diet composition of ungulates was investigated by microscopic analyses of plant remains in their faeces. The similarity of rumen and faecal analysis has been proved earlier [7]. From each of the faecal samples collected, one pellet was removed and used to prepare a microscopic slide. The representation of various diet components was estimated on the basis of their relative coverage in the microscopic field. In evaluating the overall character of the diet, the components were pooled to form primary forage classes: grasses, Rubus spp., browse (leaves and shoots of broadleaved trees), needles, forbs and ferns. Preferences of the individual plant species in the diet were expressed by Ivlev s electivity index: E i = (r i n i ) / (r i + n i ), where r i = percentage of i species in the diet; n i = percentage of i species in the environment. In general, the diet item with E i = -0.3 and 0,3 we considered as non selectived, items of E i < -0.3 as avoided and items of E i > 0.3 as preferred. The level of the quantitative similarity of diets between two species or between one species in two areas was expressed by means of the similarity index SI = y i where y i is the lower value of an item i jointly consumed by both species under study [8]. The similarity index can be in an interval from 0% (completely different diet) to 100% (identical diet). Results Red and roe deer diet in valley locality The most important component of red deer diet in spring and autumn were grasses; their percentage of volume in summer and winter was lower than in spring and autumm (P < 0.01). Raspberry (Rubus idaeus) supplemented with shoots of broadleaved woody species prevailed in red deer diet in summer, during the rest of the year their volume was lower (P < 0.001). Percentage of volume of forbs, needles and ferns differed significantly between seasons; these components were consumed the most in winter, the least in summer and autumn (P < 0.05 in all cases) (Fig. 1).

5 50 J.Kamler et al. Feeding Strategy of Wild Herbivores in Habitats of Limited Food Resources Roe deer consumed mostly Rubus spp. and broadleaved species from spring to autumn (> 80% of food volume), the consumption of this component was lower in winter (P < 0.01). Needles prevailed in winter and spring, although in summer and autumn they were present in trace amount only (< 1% of volume). Forbs (together with ferns) were consumed equally throughout the year, but their amount never exceeded 10% of food items (Fig. 1). The diets of red and roe deer at the valley locality differed. Red deer consumed more grasses during all seasons (P < in all cases). In winter, roe deer consumed more needles (P < 0.05), while the diet of red deer contained higher volume of ferns (included in the item forbs ; P < 0.01). In spring, roe deer consumed more browse and needles (P < 0.05). In summer, the content of the main components in the diets of both species did not differ, with the exception of grasses. In autumn, roe deer consumed more forbs (P < 0.03) and browse (P < 0.001). Fig. 1: Main components of the red (CE), roe deer (CC) and chamois (RR) diet in spring (sp), summer (su), autumn (au) and winter (wi) in ridge and valley locality in the Jeseníky Mts. The similarity of red and roe deer diet (judged by the similarity index) fluctuated greatly between individual seasons. In spring and autumn it was low (SI < 32%); in this period, the main component of red deer diet were grasses that were grazed by roe deer in only minute amounts. Both species has similar diets in summer (SI = 87%) when both red and roe deer ate mostly raspberry. Relatively close similarity was found also in winter (SI = 52%) when the common diet components of both species were shoots of broadleaved and coniferous woody species (Fig. 1). Red deer and chamois diet at ridge locality The main diet component of red deer and chamois were grasses; their volume dropped under 90% only in winter, when it was lower than for the rest of the year (P < 0.001). Another significant diet component of red deer and chamois in winter were needles (29-32%) and Blackberry (4-7%). Both species consumed these components more in winter than in any other season of the year (P < 0.001). Forbs and other components formed less than 1% of volume of red deer and chamois diet and their percentage did not vary significantly throughout the year. The volume of the main components of red deer and chamois diet in the individual seasons was similar except for browse in winter (Fig. 1).

6 Wildlife Biology in Practice 2011, 7(1) 51 Comparison of red deer diet at both sites The main red deer diet component in ridge and valley were grasses (in average 84.5 and 42.8% of volume). The similarity of the red deer diet in both areas (ridge and valley) was high mostly in autumn (SI = 85.7%) when grasses were abundant in the food supply and there was lack browse in the valley area. The smallest similarity was in summer (SI = 15.9%) when red deer eat grasses in ridges (lack of high nutrient components) and browse (the most nutrient component) in the valley. Red deer was able to change its diet by the food supply and to feed as grazer or browser in extreme situations. Nutritional value of diet The simulated diet varied in nutritional values in herbivore species and in seasons (Fig.2). In the growing season, the content of ME in the consumed plants ranged from 8.9 to 10.9 MJ/kg of dry matter and the content of CP from 117 to 250 g/ kg of dry matter. The most valuable were leaves of woody species, while the least valuable were grasses. In winter the content of ME ranged from 7.8 to 10.8 MJ/kg of dry matter and content of CP from 69 to 123 g/kg of dry matter. In this period, the highest-quality component was Bramble (Rubus fruticosus) and the component of the lowest quality was spruce. Fig. 2: The content of the metabolizable energy (ME) and crude protein (CP) in the diet of red and roe deer and chamois in locality ridges (rid) and valley (val) in the Jeseníky Mts. in spring (sp), summer (su), autumn (au) and winter (wi). The nutritional value of consumed diets of studied species differed between species, seasons and localities. Generally: 1. the highest quality diet consumed roe deer than other species; 2. roe deer and red deer consumed more quality diet in valley locality in comparison to red deer and chamois in ridge locality and 3. all species consumed the best diet in spring and summer and the worst in winter. The diet quality of red deer and chamois at the ridge locality was very similar. It differed only in winter, when the diet of chamois contained less CP and ME than that of red deer (P < 0.05). The diet quality of red deer at the valley locality was higher than in ridge locality in summer and autumn. In winter the differences were not significant and in spring was higher quality at ridge locality (P < 0.05 for all cases). Roe deer at the valley locality consumed the diet of higher quality in autumn and winter in comparison to other species (P < 0.05 for all cases). In summer its diet quality was similar to red deer at valley (P > 0.05) and

7 52 J.Kamler et al. Feeding Strategy of Wild Herbivores in Habitats of Limited Food Resources in spring the roe deer consumed more metabolisable energy (P < 0.05), but similar content of crude protein as red deer and chamois at the ridge locality (P > 0.05). Fig. 3: Vegetation coverage (veg) and volume of main items of vegetation in the diet of red (CE) and roe (CC) deer and chamois (RR) in ridges (rid) and valley (val) locality in the Jeseníky Mts. Selection of food by the studied species We have compared the cover of the main vegetation types at the two studied localities and the relative volume of these components in the diet of red deer, chamois and roe deer in summer. The studied localities differed in the average cover of the individual main vegetation types (Fig. 3). The differences were significant (df = 34; p < in all cases) except for the cover of ferns (p = 0.389). At the ridges locality, red deer and chamois consumed grasses not selectively. Grasses dominated in diets of both species and in vegetation cover respectively (E i = 0.17 and 0.18). Vaccinium was avoided (E i = and 0.94 respectively) analogous to forbs (E i = and resp.) (Fig. 3). At the valley, both red and roe deer preferred leaves of raspberry (E i = , which formed the main component of their summer diet. All of the remaining diet components which were less nutritious were avoided by both deer species (E i from to -0.98) (Fig. 3). Discussion The diets of red deer, chamois and roe deer in the studied environment corresponded to their feeding specializations [2]. Red deer and chamois are characterized as intermediate feeders typical with high plasticity in food selection. Red deer, in the environments where dominate grasses, tends to graze on the one, which then form over 90% of its diet during the vegetation season [16]. Much less proportion (< 50% of volume) build grasses in red deer diet in habitats with abundant forbs and deciduous trees [17, 18]. Chamois typically tends to eat more browse in forested areas and more herbaceous plants in territories with a well developed alpine belt (Perle & Hamr, 1985; Garcia-Gonzalez & Cuartas, 1996). In our study area, where the food supply was restricted to grasses, the chamois eat more grass than in other areas and it could not apply its ability of better selectivity than red deer [19]. In all studied species the

8 Wildlife Biology in Practice 2011, 7(1) 53 diet composition changes according to the food supply in the habitat; in habitat with diversified food sources the grasses usually compose a smaller part of their diet while the components of higher quality forbs and browse prevail [9]. If there is lack of forbs and browse, the diet is composed mainly of grasses, which in long term fulfil the feeding needs [4]. Such scheme of feeding strategy has been observed in the Jeseníky Mts. In the valley, in habitats with sufficient supply of Rubus spp., browse and forbs, these components formed a significant part of the red deer diet in summer, when their quality was higher than the quality of grasses. In autumn and spring, when leaves of Rubus spp. are not available and the supply of forbs and browse was limited (forbs are out of vegetative condition, annual shoots are overgrazed) red deer consumed mostly grasses which are still relatively abundant. Grasses were more nutritious than woody plants in winter (Table 1). Table 1: Content of crude protein (CP % of dry matter = Nx6.25) and metabolizable energy (ME MJ/Kg % of dry matter) in the most important diet components in vegetation period (v) and winter (w). At the ridge, in the environment with great prevalence of grasses in the food supply, this component dominated in the diets of both red deer and chamois during the whole vegetation season and even in winter, the volume of grasses in the diet was over 50%. The comparison of the diet quality and content of faecal nitrogen between the lower locations and the summits showed that migration of red deer into the highest localities may be partly motivated by better food supply, especially in spring. Young grasses in spring showed higher nutritional value than woody species that prevailed in the diet at the lower locality. In summer and autumn, when red deer in the lower locality consumed mostly raspberry, the quality of grasses at the summits was lower. In winter, when the food supply was restricted in both areas to needles and grasses, the differences in the quality of diet in red deer between higher and lower locations were insignificant. The limitation of food supply is the main reason for similarity in diet composition between different ungulates in winter [3, 4]. In the case of chamois, the unilateral grass diet (95% of the food volume) during the whole vegetation season in the Jeseníky Mts. was not typical for this species. In this environment of limited food sources, chamois could not even apply its ability of better food selection which is due to its smaller body size compared to red deer. In winter season when red deer to greater extent used the localities with broadleaved undergrowth, the quality of chamois diet (needles and grasses) was even lower than that of red deer. Roe deer is a typical browser; at the valley locality, in the vegetation season roe deer consumed mostly browse (Rubus spp.), in winter forbs and browse and the volume of grasses usually did not exceed 10% of the diet. This corresponds to the findings in other studies [11-14]. As expected, roe deer consumed during the vegetation season

9 54 J.Kamler et al. Feeding Strategy of Wild Herbivores in Habitats of Limited Food Resources (spring and autumn) diet of higher quality than red deer (higher content of CP and ME in food). In summer and winter, when the diets of both species were very similar, the differences in their quality were insignificant. The similarity of the diets in summer was due to high supply of raspberry, which was preferred by both species to grasses and browse and; on the contrary, in winter the limited feeding opportunities caused profound overlapping of food niches of both species (in roe deer higher content of needles and in red deer of grasses). Similar fusions of feeding spectra of different species in winter as a result of limited food supply have been reported from various regions [15]. Roe deer practically avoided the summits. The most important cause of this phenomenon is probably the limited food supply with lack of forbs and broadleaved woody plants and consisting mostly of grasses and conifers. In the studied environment, red deer, chamois and roe deer utilized the food sources in accordance with their feeding strategies. The specifications of the environment caused insignificant differences in the quality of diet between red deer and chamois at the ridges locality (share of grasses over 90%) and even between red and roe deer at the valley locality in summer (prevalence of raspberry). In spring and autumn was roe deer able to consume food of higher nutritional value than red deer. The strictly limited food supply at the ridges locality excluded survival of roe deer, while red deer and chamois concentrated on the open areas. For all of the studied species, winter is a season of critical lack of food. In this period the food supply is limited and the diet of all species tends to be very similar. Nevertheless, the feeding strategies and food selection of each of the species are different. Chamois stays in the higher locations, red deer usually migrates to the valley and roe deer stays in lower localities. From the food supply available in this season, chamois and red deer consume grasses in the first place (diet is composed of wavy hair grass and spruce in the ratio of 1:1). Roe deer consumes mostly needles when there is lack of broadleaved species. Acknowledgements This study was supported by the Grant Agency of the Czech Republic, Grant No. 206/03/P134. References Five key references, selected by the authors, are marked below (Three recommended ( ) and two highly recommended ( ) papers). 1. Putman, R.J Competition and resource partitioning in temperate ungulate assemblies. Chapman & Hall, London. 2. Hofmann, R.R Evolutionary step of ecophysiological adaptation and diversification of ruminants: a comparative view of their digestive system. Oecologia 78: doi: /bf Homolka, M. & Heroldová, M Native red deer and introduced chamois: foraging habits and competition in a subalpine meadow-spruce forest area. Folia Zool. 50: Latham, J., Staines, B.W. & Gorman, M.L Correlations of red (Cervus elaphus) and roe (Capreolus capreolus) deer densities in Scottish forests with environmental variables. J. Zool. 242: doi: /j tb05820.x

10 Wildlife Biology in Practice 2011, 7(1) Association of official analytical chemists Official methods of analysis. Assoc. Off. Anal. Chem. Washington, D.C. 6. Kamler, J. & Homolka, M Faecal nitrogen: a potential indicator of red and roe deer diet quality in forest habitats. Folia Zool. 54: Homolka, M. & Heroldová, M Similarity of the results of stomach and fecal contents analyses in studies of the ungulate diet. Folia Zool. 41: Anthony, R.G. & Smith, N.S Comparison of rumen and fecal analysis to describe deer diets. J. Wildl. Manage. 38: doi: / Homolka, M Foraging strategy of large herbivores in forest habitats. Folia Zool. 45: Bugalho, M.N., Milne, J.A. & Racey, P.A The foraging ecology of red deer (Cervus elaphus) in a Mediterranean environment: is a larger body size advantageous? J. Zool. 255: doi: /s Henry, B.A.M., 1978: Diet of roe deer in an English conifer forest. J. Wildl. Manage. 42: doi: / De Jong, C.B., Gill, R.M.A., Wieren, S.E. & Burlton, G.W. E Diet selection by roe deer Capreolus capreolus in Kielder Forest in relation to plant cover. For. Ecol. Manage. 79: doi: / (95) Homolka, M The diet of Cervus elaphus and Capreolus capreolus in deforested areas of the Moravskoslezske Beskydy mountains. Folia Zool. 44: Tixier, H., Duncan, P., Scehovic, J., Yani, A., Gleizes, M. & Lila, M Food selection by European roe deer (Capreolus capreolus): effects of plant chemistry, and consequences for the nutritional value of their diets. J. Zool. 242: doi: /j tb05799.x 15. Matrai, K. & Kabai, P Winter plant selection by red and roe deer in a forest habitat in Hungary. Acta Theriol. 34: Heroldová, M The food of red deer (Cervus elaphus) in a part of the Krušné hory Mountains affected by emission. Folis Zool. 42: Dzieciolowski, R Food of the red deer in an anual cycle. Acta Theriol. 36: Prokešová, J Red deer in the floodplain forest: the browse specialist? Folia Zool. 53: Hofmann, R.R Die Stellung der europaeischen Wildwiederkauer im System der Asungstypen. In: Hofmann, R.R. (ed.), Wildbiologische Informationen fur den Jager. Enke Verlag Stuttgart: 9 18.