Báo cáo khoa học: "Influence of oak mast on feeding behaviour of red deer (Cervus elaphus L)"

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Original article Influence of oak mast on feeding behaviour of red deer (Cervus elaphus L) B Boisaubert 2 P Oleffe JF Picard 1 INRA-Centre de Recherches Forestières, Laboratoire de Phytoécologie Forestière, 54280 Seichamps; Champenoux, 2 Office National de la Chasse, CNERA Cervidés-Sanglier, Place Exelmans, 55000 Bar-Le-Duc, France (Received 21 January 1991; accepted 3 June 1991) Rumen content analysis was used for assessing the autumn and winter diet of red Summary — deer in the same forest during 2 successive hunting seasons. This paper compares the results of the second season (with an abundant oak-mast) to those obtained during the first one. The main conclu- sions are: clear relationships exist between time and/or weather conditions and the diet of red deer; - forest fruits such as wild apples, pears and acorns are very important foods for red deer in autumn; - corn consumption is reduced when acorns are available; sedges, grasses and fallen dead leaves (most likely taken from the soil surface) are also important - foods, particularly when acorns are scarce; rape is mostly consumed during cold and snowy periods; - consumption of woody twigs increases dramatically when snow covers the ground. - red deer / oak-mast / rumen content / feeding behaviour Résumé — Influence d’une glandée importante sur le comportement alimentaire du cerf (Cer- vus elaphus L). Le régime alimentaire automnal et hivernal d’une population de Cerf élaphe pré- sente dans une forêt du Nord-Est de la France (Hêtraie-Chênaie calcicole) a été étudié par la techni- que des contenus stomacaux au cours de deux saisons de chasse successives, la dernière (1984- 1985) étant caractérisée par une glandée abondante. De la comparaison entre les deux saisons de chasse, il ressort que les conditions météorologiques et la disponibilité offerte interfèrent sur le ré- gime alimentaire du Cerf. Dans les deux cas, on constate : une consommation importante de fruits charnus (pommes et poires sauvages, pourtant relative- - ment rares dans cette forêt) et de feuilles vertes (Charme surtout, mais aussi Aubépine) jusqu’aux premières gelées; utilisation des herbacées (cypéracées, graminées cultivées long de l’automne tout au non) une ou - et de l’hiver; augmentation importante de la consommation de brindilles dès que la neige tient au sol; une - utilisation de Colza en période de gel et/ou de neige, en janvier-février. une - Quand les glands sont abondants (en 1984-1985), et malgré la compétition importante exercée par les autres mammifères (Chevreuil et, surtout, Sanglier), ils sont recherchés et forment la part la plus importante du régime alimentaire (50,8% en valeur pondérale) à cette période de l’année. Ceci en- * Correspondence and reprints
traîne diminution de la consommation des rameaux ligneux (8,6% pour 19,5%), des herbacées une et des feuilles mortes (2,5% pour 11,3%). L’utilisation du Colza (surtout graminées : 5,7% pour17,1 %) semble, par contre, pas avoir été modifiée. ne cerf / glandée / contenu stomacal / régime alimentaire INTRODUCTION This forest (Allain et al, 3 rele- 1978) displays vant characteristics: Stomach content analysis is a method of the dominant tree species is oak (Quercus pe- - studying the diet of wild animals which has traea), mixed with hornbeam (Carpinus betulus) and beech (Fagus sylvatica). The main forest been used for many years, particularly for (8 000 ha) in which the animals were shot is sur- red deer, Cervus elaphus* (Jensen, 1968; rounded by 2 000 ha of smaller forests and Dzieciolowski, 1970; Goffin and de Crom- many pastures and fields (including corn, Zea brugghe, 1976; Mitchell et al, 1977; mays, and rape, Brassica napus); Gebczynska, 1980; Picard et al, 1985). the vegetation has been heavily grazed for - more than 10 years due to very high populations The present research was carried out: of game animals. Estimates based on 4 annual i), to establish the importance of abundant culls are 6-9 red deer per km 8-10 roe deer , 2 oak-mast in the diet of red deer (acorns (Capreolus capreolus L) per km The density of . 2 usually occur abundantly 1 year out of 12 wild boar (Sus scrofa) must also be high (≈ 300 in northeastern France); and ii), to com- animals culled each year); pare the results in the same forest with red deer are shot almost every day during late - those of the previous year, when there autumn and winter, except when snow is too deep; regular sampling throughout the shooting was no oak-mast and a poor beech-mast, period is possible. but when the other trophic conditions (nat- ural and artificial food) were the same. During both years, autumn and winter Methods weather conditions were similar and be- longed to 4 main types: Method for collecting samples mild and wet; - cold and dry; As animal had been shot, the - soon as an rumen opened and its contents mixed. About 1 I was cold and wet; - was stored by deep freezing. snowy. - Eighty-seven rumens were collected between 21 September, 1984, and 21 February, 1985. Figure 1 shows the structure of the sample for MATERIALS AND METHODS and date. sex Method for analysing Materials the rumen contents As ina previous study (Picard et al, 1985), the The method used has been described and dis- samples were from red deer shot in the state cussed by Mitchell et al (1977), Maizeret (1983) forest of Arc Barrois, in northeastern France. and Picard et al (1985). The samples were en * cited to Grzimek for animals and to Tutin et al for Species according (1978) (1964) names are plants.
species was calculated as the percent dry mixed after thawing, and 100 g were taken and sieved through 2 square mesh sieves (5 mm on weight of the species with respect to the total top and 2 mm beneath) under running tap water. dry weight of the sample. The percentage fre- Food fragments retained by each sieve were quency of each species was also calculated. placed in large Petri dishes and sorted into plant Use of the largest (5 mm) sieve permitted easier identification, but for some species the ra- groups or species using a dissecting micro- tio &dquo;large pieces/small pieces&dquo; may be of inter- scope. Each specific fraction was then dried (48 h at 70 °C) and weighed. The result for each will be demonstrated in the of rape. est, as case
The main variables consisted of 26 categor- Statistical analysis ies of food items, closely related to those listed in table I. Factorial analysis of correspondances (FAC; Le- Additional variables consisted of undeter- bart et al, 1984) was used to group plant spe- mined food items (< 0.1% of total by weight), cies (main variables) and to relate these groups number of each food item in a rumen, size of to independent variables (additional variables). items, and deer weight, sex, age, length of lower jaw, date and time of death. Main variables were used for the determina- tion of axes, and additional variables were sub- Six rumens containing > 50% corn were dis- carded because a preliminary FAC had shown sequently plotted on the factorial planes.
they occurred randomly during the hunting period 3: from 1 November to 13 Decem- that - and that they distorted the analysis. season (29 rumens, 3 of which were corn- ber dominated); period 4: from 14 December to 30 De- - RESULTS cember (11 rumens, 1 of which was corn- dominated); period 5: from 31 December, 1984, to 30 - 1984-1985 hunting season January, 1985, (50 rumens, 1 of which was corn-dominated); Eighty-eight different food items iden- were period 6: from 31 January to 21 February - tified, including the dead leaves of 26 spe- (9 rumens, one of which was corn- cies and the green leaves of 21 species. dominated). The 25 main food items (> 0.1% occur- Comparison with figure 1 shows that rence) are listed with percent weight, per- some of the limits between these periods cent frequency and importance relative to correspond to important weather changes. frequency (table I). More precisely, period 4 corresponds to Acorns constituted the largest compo- when snow started to fall, period 5 to the nent from all rumens combined (50.8%). presence of a constant snow layer on the Only 9 food items comprised > 1%, and ground, and period 6 to the disappearance represented 95.7% of the analysed materi- of snow on the ground. al. The frequency with which these various food items were found in rumens was vari- able and was not always related to their representation according to weight. For in- stance, rape and corn which were well rep- resented in terms of weight only occurred in 18 and 15% of the rumens, respectively. Similarly, horse-chestnuts (seed from Aes- culus hippocastanum), found only once, represented 0.3% of the weight of all ana- lysed food items. Bramble leaves (Rubus sp), on the other hand, with the same pro- portion in weight, were found in 45% of the rumens. A careful examination of the first factori- al graph as defined by FAC (fig 2) led to the grouping of rumens according to their contents. Six main groups corresponding to 6 distinct time periods were clearly iden- tified: period 1: from 21 September to 12 Octo- - ber (13 rumens, 3 of which were from rut- ting animals); period 2: 13-31 October (10 rumens); -
for grasses However, the 3 first periods correspond (5.1%), all other food Except items in food availability (dis- decreasing. to change were more a appearance of green leaves in autumn, During period 4 (first snow fall), rape ap- rarefaction of apples and pears, appear- peared significantly in the rumens (9% of ance of acorns) than to climatic conditions. total weight). Grasses, and sedges to a lesser extent, reached a maximum during The date on which the animals were the fourth period while acorns remained shot was clearly related with the total num- the basic food item (52.1% of total weight). ber of food items in the rumen contents Woody twigs, dead leaves and leaf-stalks (including those < 0.1 % of total by weight). had increased since the previous period. The diet showed a wide diversity in au- tumn, but was much less diverse during A dramatic change occurred during peri- period 5, when snow covered the ground. the od 5 when covering ground: snow was woody twigs represented 56% (of total FAC also showed that sex, age, time of weight) of the rumen contents; dead death and other individual characteristics leaves and grasses reached a minimum; of the animals were not correlated with the rape was well represented in the rumens diet. This result is consistent with those of (26.3% of total weight) despite its poor ac- the previous hunting season. Dzieciolow- cessibility under the snow. ski (1970) had also found no difference be- tween the diets of males, females and Period 6, which corresponded to snow to be intermediate be- calves. However, Mitchell et al (1977) and thawing, seems previous periods. The propor- Staines et al (1982), found differences in tween the 2 tion of increased again, and partly diet between stags and hinds. acorns replaced woody twigs. Rape was stable The proportion of the different food and grasses increased. The rumen con- items on a weight basis in the 6 periods tents were much more varied during period defined by FAC is given figure 3. 6 than during the previous ones. In 8 ru- The diet during period 1 was character- mens out of 9, different food items repre- ized by the abundance of pears, apples sented > 50% (by weight) of their total con- and green leaves. Some leaf-stalks and tent: woody twigs for 2 rumens; acorns for woody twigs were present, as well as 1 rumen; rape for 2 rumens; grasses for 2 grasses, sedges and corn. Some animals rumens; corn for 1 rumen. had already found acorns (acorns started Thus an average diet cannot be de- to fall to the ground from late September, scribed for this last period: it would be pos- becoming abundant by mid-October). sible with a largest sample. The animals during period 2 was intermedi- The diet had difficulties in recovering a regular diet ate between those of periods 1 and 3: and displayed a typical opportunistic beha- were already dominant. Some ap- acorns viour when confronted with less diverse ples and pears were still present, but and less available foods than at the begin- green leaves had almost completely disap- ning of the hunting season. peared in the rumens (they were not avail- able any more because of leaf-fall), and dead leaves appeared. Woody twigs and Reminder of 1983-1984 hunting season leaf-stalks had decreased slightly, and grasses and sedges became very rare. This divided into 4 hunting season was The diet during period 3 was largely main weather conditions based periods on dominated by acorns (84% of total weight). (table II):
DISCUSSION before October 20: weather mild and - mostly on green leaves of wet. Deer fed woody plants (mostly hornbeam; Carpinus Comparison between years (table III) betulus L and oak, Quercus sp), wild ap- ples and pears, dead leaves and some grasses (including sedges and rushes); Acorns are seldom cited as an important October 20-December 17: weather cold food item red deer, probably because - and dry. Deer fed on beech nuts and corn acorns (and, perhaps, oaks) are rare in the (from nearby fields) in addition to dead forests where most studies take place. leaves and grasses in a larger amount However, Gebczynska (1980) also found than previously; an occasional high consumption of acorns, and considered that red deer fed mostly on December 17-January 20: weather cold - trees and shrubs rather than on herbs and and wet; dead leaves and beech nuts grasses. Our results do not support this were still present in rumen contents, but view. grasses were dominant; In the case of roe deer, Maillard (1984) after January 20: snow on the ground; - also found a high consumption of acorns, no more dead leaves or beech nuts in ru- reaching 87% (by weight) of the rumen men contents, slight reduction of grasses, contents. Jackson (1977, 1980), Fichant a dramatic increase of twigs and buds (1974), and Harlow et al (1975) showed from woody plants and rape leaves (Bras- that acorns were very important in autumn sica napus L) from nearby fields.
for roe deer, fallow deer and white-tailed est forlonger than usual. This hypothesis deer. Thus, it is clear that acorns may be is supported by the fact that wheat was an important part of the diet of deer when found to be mixed with corn in 2 rumens oak-mast is abundant. (12 January and 6 February). Some other food items, such Woody twigs. The mean percent of wood as corn, woody twigs, rape, grasses, dead leaves, (by weight) in rumens differs markedly be- ivy and bramble merit further discussion: tween the 2 years. Before snow and with (first year), the proportion was no acorns Corn. Important differences in corn con- 15.7%; with acorns (second year), it was sumption are clearly indicated between the only 6.7% before snow. However, during 2 hunting seasons. During the first year, snowy periods, the proportion was 45.2% corn was found in rumens mostly between for the first year and 47.9% for the second 20 October and 17 December, probably one. These latter 2 proportions are quite because the animals were eating the left- similar and much higher than those for the from the harvest. This was con- overs period before snow: it shows that snow is a firmed by the high frequency (73%) of ru- determinant in the choice of this type of mens with corn containing fragments of food which is available above ground. This ears. In contrast, during the second year, is consistent with the results of Delaunay corn was found in rumens during the whole (1983) for chamois in the French Alps. hunting season, and only 38% of those ru- mens with corn contained ear fragments. It Rumen content analysis do not lead Rape. is likely that the tendency to eat corn in the importance of to a correct estimation of the fields was diverted by the abundance of in the diet of red deer during winter. rape acorns, which kept the red deer in the for- This particular food item quickly disap-
very important in mid-winter, especial- 2 ob- pears from the rumen, shown by was as ly of plants 10-20 cm high. servations: consistent be- Grasses. The results in vitro digestibility tests (Oleffe et al, un- are - tween the 2 years. After the shrubs have published observations) have shown that shed their leaves and the fleshy fruits have rape is quickly digested, even more quick- became scarce, grasses and sedges are a ly than alfalfa; basic food for red deer. The relative impor- figure 4 shows that each time rape rep- - tance of these food items is reduced in the (by weight) of the rumen resents > 20% case of abundant oak-mast, but they re- content, most of it is in thecoarse fraction main more represented than dead leaves 5 mm; whole leaves or stalks or ribs). (> which are less digestible (Oleffe, 1986), Thus, the leaf blades are quickly digested. and probably overestimated by the tech- Another observation suggests that rape nique used. Staines and Welch (1984) and is rapidly digested: for most of animals Jensen (1968) have confirmed the impor- whose rumens contained rape, shooting tance of grasses in the diet of red deer in time was before midday and it is known summer and winter. that deer feed in fields exclusively by Dead leaves. This food item was the most night. reduced by the presence of acorns (from However, it is probably not by chance 16.5% to 7% of the rumen contents by that a large amount of rape was found for weight). The only period of the second both years in the rumens after the first year (with acorns) when deer ate a signifi- snow; this food item is likely to be more cant amount of dead leaves was when ap- important for the animals when such ples and pears became scarce and acorns weather conditions are prevailing. Ahlèn were just beginning to fall. (1965) found that rape consumption by red The fact that for both years the con- deer in Scandinavia began in October and sumption of dead leaves is negligible when snow covers the forest floor suggests that deer prefer dead leaves on the ground than those still attached to shrubs. Ivy and bramble. Scarcity of these 2 spe- cies in the forest is probably the main rea- son why they are almost absent in rumens. In a nearby forest, much richer in ivy and bramble, these species sometimes repre- sented > 50% of the rumen contents. For the first year (Picard et al, 1985), diet was clearly related to weather. This was not the case for the second year as long as acorns were easily available on the ground. When this was the case, animals fed mostly on them after an initial period when green leaves and fleshy fruits were abundant. The slight weather changes which occurred during that period had no effect on diet.
The first important diet modification dur- importance of which in the diet of red deer has been demonstrated in this study. the second year was caused by snow, ing which dramatically reduced the importance Jackson (1977) summarized the limita- of acorns. It is also probable that at the tion of the method: "Thus quantitative com- same time the stock of acorns was already parisons between different foods only ap- significantly depleted by the earlier mas- proximate indications of their relative sive intakes, including intakes by wild boar. importance (Dzieciolowski, 1970); but as At the same time, grasses and sedges in- Jensen (1968) indicates, when comparing creased in the diet. the diets of large mammals it is generally of little consequence whether a food forms precisely 30, 35 or 40% of the intake. The Methodology crucial point is that is forms about one third ot the diet and it is therefore a major food". This study also suggests criticisms some of the method: CONCLUSIONS measuring the dry weight of the different - food items over-represents dry fruits com- pared to fleshy fruits or fungi (Picard et al, This study confirms the major importance 1985; Maillard and Picard, 1987). Measur- of forest fruits in the autumn diet of red ing volumes (Jackson, 1977; Kay and deer already reported (Picard et al, 1985): Staines, 1981) is likely to give more relia- beech nuts and acorns (when available), ble results as far as satiety is concerned. and apples and pears (in spite of the rarity the frequency of food items recorded of fruit trees in this forest). Corn is avidly - may give biased estimates of their impor- sought for by animals, in the forest on tance to the animal diet due to differential feeding places for wild boar as well as in digestibility: digestibility is not the same for the surrounding fields. different food items, and the time they It is confirmed that grasses and sedges have been in the rumen is unknown. This basic food item for red deer. Howev- are a may introduce a bias in the interpretation temporarily neglected as long they are er, of the results of rumen analysis in terms of available in large quantities. as acorns are the actual food uptake by the animals. preference for acorns is also reported This Mclnnis et al (1983) compared 4 methods by Jackson (1977) for fallow deer. for studying the diet of sheep (direct obser- Dead leaves are also important in the vation, oesophageal fistulation, rumen diet of red deer. Jackson (1977) noted up analysis and faecal analysis) and conclud- to 59% of dead leaves in fallow deer ru- ed that the results of rumen analysis gave mens, but there have been few reports for correct estimation of the diet. However, a red deer. noted that grasses they overestimat- were ed if digestible forbs. compared to more never been found in the ru- Bark has the 2 years of the study. This during Inspite of these criticisms, the rumen mens is contrary to the results of Dzieciolowski analysis method is very valuable as a com- (1970), Borowski and Kossak (1975) in Po- plement to browsing studies, because the land or of Ahlèn (1965) in Scandinavia, intake of many food items does not leave who consider that bark in a normal food clear evidence in the forest. This is particu- item for red deer. larly true for acorns and dead leaves, the
contenus stomacaux. Fond l’analyse des The main difference between the 2 Univ Luxemb Sér Notes Rech 23 pp hunting seasons is the abundance of oak- Gebczynska Z (1980) Food of the roe deer and mast during the second one. The acorns red deer in the Bialowieza primeval forest. were largely consumed by red deer. When Acta Theriol 25 (40), 487-500 acorns are available, weather (tempera- Goffin RA, de Crombrugghe SA (1976) Régime ture and rainfall) has no significant effect alimentaire du cerf (Cervus elaphus L) et du on the diet except when snow covers the chevreuil (Capreolus capreolus L) et critéres ground. de capacité stationnelle de leurs habitats. Mammalia 40 (3), 355-376 Nevertheless, with the exception of the last period (after 31 January) during which Grzimek B (1978) Le Monde Animal en Treize Volumes. Encyclopédie de la Vie des Bêtes. the diet was disturbed (and the sample too Stauffacher SA, Zurich small), the results of the 2 years are con- Harlow RF, Whelan JB, Crawford HS, Skeen JE sistent: according to weather conditions (1975) Deer foods during years of oak mast and food availability, red deer are able to abundance and scarcity. J Wildl Manage 39 adapt to the changing resources. (2), 330-336 BAM (1978) Diet of deer in an English Henry roe conifer forest. J Wildl 42 (4), 937- Manage ACKNOWLEDGMENTS 940 Jackson J (1977) The annual diet of the fallow The authors are grateful to the Office National deer (Dama dama) in the New Forest, Hamp- des Forêts which supported this work and con- shire, as determined by rumen content analy- tributed to it by sampling the rumens and to sis. J Zool (Lond) 181, 465-473 J Garbaye who helped us write the English ver- Jackson J (1980) The annual diet of the roe sion of this paper. deer (Capreolus capreolus) in the New For- est, Hampshire, as determined by rumen content analysis. J Zool (Lond) 192, 71-83 REFERENCES Jensen PV (1968) Food selection of the Danish red deer (Cervus elaphus L) as determined by examination of the rumen content. Dan Ahlèn I (1965) Studies on the red deer, Cervus Rev Game Biol 5 (3), 1-44 elaphus L in Scandinavia. III. Ecological in- vestigations. Viltrevy 3 (3), 177-376 Staines BW (1981) The nutrition of Kay RNB, the red deer (Cervus elaphus). Commonw Allain R, Commeau A, Picard JF (1978) Étude Bur Anim Nutr Ser B 51 (9), 601-622 des relations forêt-cervidés en forêt doma- niale d’Arc en Barrois (52). Rev For Fr 30 Lebart L, Morineau A, Warwick KM (1984) Multi- (5), 333-352 variate Descriptive Statistical Analysis. J Wi- ley and Sons, NY Borowski S, Kossak S (1975) The food habits of deer in the Bialowieza primeval forest. Acta Mcinnis ML, Vaura M, Krueger WC (1983) A Theriol 20 (32), 463-506 comparison of four methods used to deter- mine the diet of large herbivores. J Range Delaunay G (1983) Suivi du régime alimentaire Manage 36 (3), 302-306 hivernal du chamois Rupicapra rupicapra L dans le parc national des Écrins. Actes Coll Maillard D (1984) Contribution à l’étude de Natl Mammal (Grenoble) 75-82 l’alimentation automnale et hivernale du chevreuil en forêt de Haye (54) par fanalyse Dzieciolowski R (1970) Foods of the red deer as determined by rumen content analyses. Acta des contenus stomacaux. DEA, biologie et Theriol 15 (6), 89-110 physiologie végétale, Univ Nancy I, 88 pp + annexes Fichant R (1974) L’alimentation du chevreuil Maillard D, Picard JF (1987) Le régime alimen- (Capreolus capreolus L) en période autom- nale, dans le sud de l’Ardenne Belge, par taire automnal et hivernal du chevreuil (Ca-
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