05_Ivanovsky.indd UDC 597/599:574.474:57.047 CHANGES IN THE TROPHIC STRUCTURE OF THE VERTEBRATE PREDATOR COMMUNITY IN THE COLD SEASON IN BELARUSSIAN PAAZERJE (NORTHERN BELARUS) WITH EMPHASIS ON DEPOPULATION OF THE WILD BOAR, SUS SCROFA (ARTIODACTYLA, SUIDA) V. V. Ivanovskij1, A. A. Sidorovich2, I. A. Solovej3 1Vitebsk State University named aft er P. M. Masherov, Moskovskij Ave., 33, Vitebsk, 210038 Belarus E-mail: ivanovski@tut.by 2Scientifi c and Practical Center for Bioresources of NAS of Belarus Akademicheskaja str., 27, Minsk, 220072 Belarus E-mail: anna-ecofox@mail.ru 3Scientifi c and Practical Center for Bioresources of NAS of Belarus Akademicheskaja str., 27, Minsk, 220072 Belarus E-mail: soloveji@tut.by A. A. Sidorovich (https://orcid.org/0000-0001-7523-5048) Changes in the Trophic Structure of the Vertebrate Predator Community in the Cold Season in Belarussian Paazerje (Northern Belarus) with Emphasis on Depopulation of the Wild Boar, Sus scrofa (Artiodactyla, Suida). Ivanovskij, V. V., Sidorovich, A. A., Solovej, I. A. — Anthropogenic disturbances oft en alter patterns of community functioning. Along that, how interacting species respond to these changes remains poorly understood. In 1972–2019, we studied the trophic structure of the vertebrate predator community in coniferous-small-leaved forests of Belarussian Paazerje (Northern Belarus). Since 2013, large scale depopulation of Wild Boars, Sus scrofa, has been started in Belarus as a measure to reduce a circulation of the African swine fever (ASF). It was found that the community consisted of four trophic guilds including small rodent consumers, bird consumers, scavengers, and ungulate consumers. Th e pronounced shift s in dietary compositions of three scavengers (the Raccoon Dog, Nyctereutes procyonoides, Golden Eagle, Aquila chrysaetos and White-tailed Eagle, Haliaeetus albicilla) after a decrease in an abundance of Wild Boar carrion was revealed. Along that, the average value of the dietary similarity between investigated species stayed the same. K e y w o r d s : community structure, vertebrate predators, dietary composition, Wild Boar depopulation, Belarus. Zoodiversity, 55(2): 133–142, 2021 DOI 10.15407/zoo2021.02.133 134 V. V. Ivanovskij, A. A. Sidorovich, I. A. Solovej Introduction Th e analysis of competitive relationships in the multi-species community of vertebrate predators and their prey was conducted in several studies (Levins, 1968; Matveev et al., 1988; Krebs, 1999; Kataev, Okulova, 2007; Sidorovich, 2016). And still a lot of open questions exist in relation to particular patterns of food resource partitioning and its seasonal and multiannual dynamics, especially in conditions of unexpected human impacts on natural environments. Th e African swine fewer (ASF) was fi rstly offi cially recognized in Belarus in 2013. And right aft er that state and private hunting estates started large-scale depopulation of Wild Boars, Sus scrofa Linnaeus, 1758, as a preventive measure. As a result, the Wild Boar numbers declined from 80.4 thousand in 2013 to 2.6 thousand in 2018. Two species of large predators (the Grey Wolf, Canis lupus Linnaeus, 1758 and Eurasian Lynx, Lynx lynx Linnaeus, 1758), predate on Wild Boars in winter time, and six species of vertebrate predators (the Raccoon Dog, Nyctereutes procyonoides Gray, 1834, Golden Eagle, Aquila chrysaetos Linnaeus, 1758, White-tailed Eagle, Haliaeetus albicilla Linnaeus, 1758, Red Fox, Vulpes vulpes Linnaeus, 1758, Pine Marten, Martes martes Linnaeus, 1758, and Rough-legged Buzzard, Buteo lagopus Pontoppidan, 1763), consume Wild Boar carrion in the cold season constantly (Sidorovich, 2016; Ivanovskij et al., 2019). Th e goal of this study was to analyze the trophic structure of the vertebrate predator community in the cold season in coniferous-small-leaved forests of Belarussian Paazerje and reveal possible changes caused by depopulation of Wild Boars. Such reduction of food supply may cause cascade ecological eff ects. Th e winter is the harshest period in the life of predators in Northern hemisphere. Food supply is very limited due to low abundance and diffi cult access to food resources. Any shift s in food resource availability will impact not only on a dietary composition of the species but also may lead to signifi cant functional and structural changes in the whole vertebrate predators’ community. Th e study is a part of interrelated projects on feeding habits of vertebrate predators in Belarus (Jaksic et al., 1981; Jedrzejewska, Jedrzejewski, 1998; Sidorovich, 2016; Ivanovskij et al., 2019). Material and methods S t u d y a r e a Th e study was conducted in Northern Belarus where mixed coniferous-small-leaved forests are prevailed. Th is region is traditionally called Belarussian Paazerje (Lakeland) and comprises Vitebsk Region and some northern districts of Minsk and Grodno Regions. Central and Western parts of the territory is occupied by the Polotsk lowland. Th e climate of the territory is humid continental. Compared to the rest country, Belarussian Paazerje has more severe climate conditions. Th e average temperature in January is –6.5–7.0 °С. Th e territory belongs mainly to the basin of the Zakhadnaya Dzvina River (81 %) and is characterized by a relatively dense hydrographic network with a huge number of postglacial lakes (about 2.8 thousand) of diff erent size. Lakes cover 2.5 %, in some areas (Braslavsky and Ushachsky Districts) up to 10 %. Belarussian Paazerje belongs to the European forest zone (subzone of transitional mixed coniferous- small-leaved forests). Forest cover comprises 39.8 %. Wetlands occupy about 9 % of the territory and vary from open grassy marshes to pine bogs and swamped black alder forests. In relation to fauna composition, Belarussian Paazerje belongs to the European-Siberian subarea of the Palearctic ecoregion. About 462 species of vertebrate animals inhabit its territory: 72 species of mammals, more than 58 species of fi sh, 19 species of amphibians and reptiles, about 236 species of nesting birds and 33 species on migrations or wintering. D i e t c o m p o s i t i o n Th e dietary composition of 17 vertebrate predators in the region (5 species of birds of prey, 6 carnivorous mammals and 6 owls) was studied by visual observations and an analysis of prey remains, pellets and scats. Five birds of prey (the Golden and Wite-tailed Eagles, Goshawk, Accipiter gentilis Linnaeus, 1758, Sparrowhawk, Accipiter nisus Linnaeus, 1758, Rough-legged Buzzard) and six owls (the Eurasian Pygmy Owl, Glaucidium passerinum Linnaeus, 1758, Tengmalm’s Owl, Aegolius funereus Linnaeus, 1758, Tawny Owl, Strix aluco Linnaeus, 1758, Ural Owl, Strix uralensis Pallas, 1771, Great Grey Owl, Strix nebulosi J. R. Forster, 1772, and Eurasian Eagle Owl, Bubo bubo Linnaeus, 1758), stay in Belarussian Paazerje for overwintering. Among mammalian predators, the Wolf, Pine Marten, Red Fox, and Weasel, Mustela nivalis Linnaeus, 1766, are common and numerous there. Th e Raccoon Dog stays active when the conditions are not very cold. Th e population numbers of the Eurasian Lynx is increasing but still remains low. Rare species with low population densities were excluded from the analysis. Th e taxonomic identifi cation of osteological material, feathers and skin scales of amphibians, reptilians and birds was done by comparing with a control collection and using special keys (Cramp, Simmons, 1980; Böhme, 1977; März, 1987; Brown et al., 1999; Sidorovich, 2014). Th e identifi cation of mammals from pellets and scats was carried out by two methods: by skulls, teeth, and other parts of the skeleton (Pucek, 1981) and by the microscopic structure of ten hairs that were randomly taken from a pellet or scat (Debrot et al., 1982; Teerink, 1991). Th e number of specimens of the same small mammal species in a pellet was estimated by the number of similar skeletal remains and using known weights of a hair coat for diff erent species (Sidorovich, 2014). Insects were distinguished by the remains of exoskeleton. A total of 2,339 feeding samples (pellets, scats and prey remains) are gathered in 1972–2019 in semi-natural forests 135Changes in the Trophic Structure of the Vertebrate Predator Community with Emphasis... on Belarussian Paazerje. 6,307 prey individuals were identifi ed.In addition, published data of V. E. Sidorovich (Sidorovich, 2011) on diets of the Weasel, Pine Marten, Pygmy Owl, Ural Owl, Great Grey Owl, Eagle-Owl, and Sparrowhawk before 2013 were used to complete the analysis. To investigate the feeding behavior of predators near carrion, more than 50 hours of observations from a special shelter were carried out. To obtain the percentage of food biomass consumed (hereaft er, % BC) for carnivorous mammals, we followed the approach based on the coeffi cients of digestibility (the ratio of fresh weight of a given food item to the dry weight of its remains in a feeding sample. Th e sources of the digestibility coeffi cients were Reynolds and Aebischer (1991), Jędrzejewska and Jędrzejewski (1998) and the references therein. For birds of prey calculations was done in diff erent way. Th e number of prey individuals was multiplied by the mean body mass of that prey (Pucek, 1981; Sidorovich, 2014). If a weight of a given prey or another food item (in the case of carrion consumption) is higher than the weight of average daily food intake of the species, we used the latter value in the calculations. Each researcher who deals with trophic structure of the community always faces a dilemma: how many food categories to divide out of all diversity of food items. A very detailed division can lead to the fact that behind a dense “forest” of dendrograms researches may not see a pair of connected “branches”. From other hand, the splitting into larger food categories may lead to a very high similarity between species. As a “golden mean”, we group all food items into 19 categories in accordance with consumption pattern (predation, scavenging, gathering) and a prey body mass. Dietary diversity (trophic niche breadth) was assessed by the Levins’ index B (Levins, 1968): , (Eq.1) where pi — fraction food item i is of the total biomass consumed by the predator. Th e simplifi ed Morisita’s index CH (aft er Krebs. 1999) was used to compare diets: , (Eq.2) where pij — fraction food item i is of the total biomass consumed by Common Buzzards in the study area j; pik — fraction food item i is of the total biomass consumed by Common Buzzards in the study area k; i = 1, 2, 3,…, n; n — total number of food items. Th e index varies between 0 (exclusive niches) and 1 (complete overlap). To assess the trophic structure of the community and reveal trophic guilds we applied the cluster analysis using the Morisita’s index as a proxy of similarity. Th e replicated goodness-of-fi t test (G-statistic) was used to examine the heterogeneity of percentages and reveal signifi cant diff erences between diet compositions (Sokal, Rohlf ,1995). S t a t i s t i c a l a n a l y s i s Statistical calculations were carried out using ASPID/GT soft ware (Grigyantz, 1993 ) according to the recommendations given by Sokal and Rohlf (1995). Cluster analysis was performed in PAST soft ware (release 3.06) by the method of unweighted double mean (UPGMA), using the Morisita’s index as a measure of similarity. Results and discussion T h e t r o p h i c s t r u c t u r e o f t h e v e r t e b r a t e p r e d a t o r c o m m u n i t y Our study showed that in coniferous-small-leaved forests of Belarussian Paazerje, vertebrate predators consumed all taxa of vertebrate animals as well as a wide range of insects and other invertebrates. In 1982–2011, the most important items in their diets were small rodents, ungulate carrion, and medium-sized animals (table 1–3). Th e food niche breadth, assessed with Levins’ index (B), ranged from 1.0 to 4.6. Th e values of Morisita’s index of similarity varied from 0 to 0.99 (table 4). Complete dissimilarity (CH = 0) was found for 11 pairs of species. Low dietary overlap (CH < 0.33) was attributable for 54 pairs of species, medium (0,33 < CH < 0.66) for 26 pairs of species, and high (CH > 0.66) for 40 pairs of species. Th e average value of the trophic similarity for the community was moderate and equaled 0.37. In accordance with cluster analysis, the community of vertebrate predators in forest ecosystems consisted off our pronounced clusters (trophic guilds) with the level of similarity inside clusters is higher than 0.5 (fi g. 1). Th e largest trophic guild (cluster 1) comprised nine small mammal consumers: the Tengmalm’s Owl, Weasel, Rough-legged Buzzard, Ural Owl, Great Grey Owl, Tawny Owl, Eagle-Owl, Pine Marten, and Red Fox. Th e portion of small mammals in the diets of these predators varied from 38.9 to 88.9 % BC. Th e Pine Marten 136 V. V. Ivanovskij, A. A. Sidorovich, I. A. Solovej T a b l e 1 . Dietary composition (% BC) of mammalian predators in the cold season in coniferous- small-leaved forests of Belarussian Paazeje, Northern Belarus, 1982–2011 Food items Weasel* Pine Marten* Raccon Dog Red Fox Eurasian Lyn x* Grey Wolf* Invertebrates 0.1 4.8 2.6 0.1 – – Fish – – 0.5 – – – Amphibians and reptiles 0.7 1.7 0.9 0.2 – – Small insectivores 7.1 6.1 0.4 0.4 – – Small rodents, among them: 86.5 38.9 1.7 46.4 8.1 0.1 Microtus voles 20.1 3.4 1.1 29.0 5.1 0.1 Sylvaemus mice 2.1 7.0 0.1 1.6 – – Bank Vole 62.8 22.2 0.5 8.8 – – Water Vole 1.5 – – 1.9 – – Other small rodent species – 6.3 – 5.1 3.0 – Squirrel, Muskrat and Hedgehog – 6.3 1.7 5.1 3.0 – Hares – 1.1 0.4 13.4 45.7 2.7 Beaver – – – – 0.5 3.5 Wild ungulates, among them: – – – – 24.4 87.0 Roe Deer – – – – 21.4 7.9 Elk – – – – – 28.3 Wild Boar – – – – 3.0 50.8 Small mustelids – – 0.2 0.4 – – Medium-sized mustelids – – 0.3 1.6 1.3 – Red Fox and Raccoon Dog – – – – 4.4 4.0 Domestic animals – – – – 1.2 2.4 Carrion of wild animals, among them: – 21.6 58.3 28.5 – – Beaver Carrion – 0.1 – 4.8 – – Carrion of Cervids – 21.4 39.0 18.4 – – Wild Boar Carrion – 0.1 19.3 5.3 – – Small birds 2.8 3.9 0.4 0.9 0.9 – Medium-sized and big birds – 4.0 1.8 2.9 13.4 0.1 Bird eggs – 0.5 – – – – Seeds, fruits and vegetables – 11.1 20.3 0.1 0.1 0.2 Other – – 10.5 – – – Number of food specimens (n) in the analysed samples (m), n (m) 190 (178) 604 (243) 1270 (397) 2186 (465) 425 (250) 1052 (620) Levins’ index (B) of food niche breadth 1.33 4.47 2.54 3.14 2.08 1.54 *Diets of the predators are taken from Sidorovich et al., 2011. 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 Pygmy Owl Sparrowhawk Goshawk Tengmalm's Owl Weasel Rough-legged Buzzard Ural Owl Great Grey Owl Tawny Owl Eagle-Owl Pine Marten* Red Fox Raccon Dog White-tailed Eagle Golden Eagle European Lynx Grey Wolf Similarity Fig. 1. Dietary similarity of 17 vertebrate predators in the cold season in Belarussian Paazerje, 1972–2012. 137Changes in the Trophic Structure of the Vertebrate Predator Community with Emphasis... and Red Fox formed separate sub-cluster within cluster 1 due to frequent consumption of ungulate carrion. A dietary similarity between small mammal consumers was much higher than between species in other guilds. Two guilds consisted of three species each. Th e guild of scavengers (cluster 2) included the Raccoon Dog, White-tailed and Golden Eagles in whose diets mammalian carrion constituted not less than 40 % BC. Birds prevailed in diets of the Goshawk, Sparrowhawk and Pygmy Owl (cluster 3), and were important additional food stuff for the rest predators. Th e Wolf and Lynx represented the guild of ungulate consumers. B e h a v i o r a l p a t t e r n s o f s c a v e n g e r s n e a r m a m m a l i a n c a r r i o n We examined a behavior of fi ve taxonomic predatory species (the Wite-tailed Eagle, Golden Eagle, Red Fox, Pine Marten and Raccoon Dog) and one non-taxonomic predatory species (the Common Raven, Corvus corax Linnaeus, 1758) while feeding on the carrion. Simultaneous presence and feeding on carrion was registered for avian scavengers at day time. Th e Golden and White-tailed Eagles regularly confl icted over carrion (fi g. 2), and the raven just tried to grab a piece of meat during these encounters. Mammalian scavengers ate mostly when avian predators fl ew away or came to carrion at night. We also found no physical collisions between mammalian scavengers. Consumption on carrion in winter conditions has negative consequences for the White-tailed and Golden Eagles. Th ey suff ered from traps set by hunters at carrion to Catch Wolves, Red Foxes, Raccoon Dogs and Pine Martens (fi g. 3). During the study period (1972–2019), we revealed 46 White-tailed Eagles and 37 Golden Eagles caught in a trap and died. T a b l e 2 . Dietary composition (% BC) of owls in the cold season in coniferous-small-leaved forests of Belarussian Paazeje, Northern Belarus, 1982–2011 Food items Pygmy Owl* Tengmalm’s Owl Tawny Owl* Ural Owl* Great Grey Owl* Eagle- Owl* Invertebrates – 0.1 3.8 – – – Fish – – – – – – Amphibians and reptiles – – 14.0 1.7 – 1.0 Small insectivores 2.5 1.3 13.8 8.5 2.3 5.6 Small rodents, among them: 41.3 95.7 53.6 64.9 75.8 54.1 Microtus voles 1.7 10.7 22.9 11.2 38.4 3.6 Sylvaemus mice 13.4 6.2 6.6 8.6 4.6 0.9 Bank Vole 25.0 73.1 24.1 29.0 2.1 0.7 Water Vole – 5.7 – 6.9 30.7 48.4 Other small rodent species 1.2 – – 9.2 – 0.5 Squirrel, Muskrat and Hedgehog – – – 9.2 0.5 0.5 Hares – – – 3.0 4.9 21.8 Beaver – – – – – – Wild ungulates, among them: – – – – – – Roe Deer – – – – – – Elk – – – – – – Wild Boar – – – – – – Small mustelids – – 4.7 5.5 13.1 10.4 Medium-sized mustelids – – – – 0.3 0.5 Red Fox and Raccoon Dog – – – – – – Domestic animals – – – – – – Carrion of wild animals, among them: – – – – – – Beaver Carrion – – – – – – Carrion of Cervids – – – – – – Wild Boar Carrion – – – – – – Small birds 56.2 2.9 3.6 3.0 – 0.6 Medium-sized and big birds – – 6.5 4.2 3.1 5.5 Bird eggs – – – – – – Seeds, fruits and vegetables – – – – – – Other – – – – – – Number of food specimens (n) in the analysed samples (m), n (m) 109 (52) 104 (83) 324 (62) 41 (41) 184 (42) 226 (26) Levins’ index (B) of food niche breadth 2.05 1.09 2.98 2.25 1.68 2.80 *Diets of the predators are taken from Sidorovich et al., 2011. 138 V. V. Ivanovskij, A. A. Sidorovich, I. A. Solovej T a b l e 3 . Dietary composition (% BC) of birds of prey in the cold season in coniferous-small-leaved forests of Belarussian Paazeje, Northern Belarus, 1982–2011 Food items Sparrow-hawk* Goshawk Rough-legged Buzzard Golden Eagle White-tailed Eagle Invertebrates – – 0.1 – – Fish – – – – 27.8 Amphibians and reptiles – 0.1 – – – Small insectivores – – 0.7 – – Small rodents, among them: – 16.0 88.9 0.8 – Microtus voles – 2.1 80.4 – – Sylvaemus mice – 1.5 7.0 – – Bank Vole – 9.9 1.4 – – Water Vole – – – – – Other small rodent species – 2.5 0.1 0.8 – Squirrel, Muskrat and Hedgehog – 13.4 – 0.8 0.3 Hares – 5.3 7.8 24.8 3.0 Beaver – – – 6.4 – Wild ungulates, among them: – – – – – Roe deer – – – 1.9 – Elk – – – – – Wild Boar – – – – – Small mustelids – 1.4 – – – Medium-sized mustelids – 0.7 – 2.2 6 Red Fox and Raccoon Dog – 0 – 5.8 8.3 Domestic animals – 2.3 – 0.8 0 Carrion of wild animals, among them: – 2.6 2.5 42.7 46.1 Beaver Carrion – – – – – Carrion of Cervids – 2.6 1.0 21.3 25.6 Wild Boar Ccarrion – – 1.5 21.4 20.5 Small birds 100 28.2 – 1.2 – Medium-sized and big birds – 30.0 – 12.6 8.5 Bird eggs – – – – – Seeds, fruits and vegetables – – – – – Other – – – – – Number of food specimens (n) in the analysed samples (m), n (m) 339 (66) 108 (65) 515 (264) 116 (81) 158 (63) Levins’ index (B) of food niche breadth 1.00 4.60 1.25 3.73 3.24 *Diets of the predators are taken from Sidorovich et al., 2011 Fig. 2. Th e Golden and White-tailed Eagles feed regularly on carrion and physical interference takes place quite oft en. 139Changes in the Trophic Structure of the Vertebrate Predator Community with Emphasis... Shift in feeding habits and resource partitioning between vertebrate predators in relation to Wild Boar depopulation While comparing the feeding habits of some predatory species before and aft er depopulation of Wild Boars it was revealed that the dietary composition of three species (the Raccoon Dog, White-tailed and Golden Eagles) out of 10 selected species changed signifi cantly (G = 53.5–119.0, p < 0.05) due to lower consumption of Wild Boar carrion and higher consumption of other food items (table 5). A little sift s in diets of other scavengers have also been noticed however these changes were not statistically signifi cant. Th e Golden Eagle and White-tailed Eagle compensated for the lack of Wild Boar carrion by more frequent consumption of Cervids’ carrion, and the Raccoon Dog started to consume Bea- ver (Castor fi ber L.) carcasses. Dietary overlaps between 10 selected species changed when comparing before and aft er depopulation — for 17 pairs of species dietary similarity increased, and for 23 pairs of Fig. 3. Th e Golden (a) and White-tailed (b) Eagles suff ered from traps set by hunters at Carrion to Catch Wolves, Red Foxes, Raccoon Dogs and Pine Martens. Photos by Ronald Jan Huijssen (a) and Ugis Bergmanis (b). a b T a b l e 4 . Dietary overlaps (the Morisita’s index) between vertebrate predators in the cold season in coniferous-small-leaved forests of Belarussian Paazerje, Northern Belarus, upper right corner — before a depopulation of the Wild Boar (1982–2011), bottom left corner — aft er a large-scale depopulation of the Wild Boar (2013–2019) Spe cies Mm** Np Vv Af Sa An Ag Bl Ha Ach Mn Ll Cl Gp Su Sn Bb Mm 0.39 0.96 0.78 0.88 0.06 0.45 0.82 0.34 0.36 0.70 0.17 0 0.58 0.87 0.85 0.84 Np 0.42 0.50 0.03 0.04 0.01 0.09 0.05 0.78 0.77 0.03 0.02 0 0.02 0.11 0.03 0.03 Vv 0.93 0.56 0.73 0.77 0.01 0.41 0.79 0.44 0.55 0.75 0.34 0.01 0.50 0.79 0.80 0.84 Af 0.81 0.07 0.60 0.82 0.03 0.28 0.99 0 0.01 0.99 0.13 0 0.59 0.76 0.96 0.82 Sa 0.92 0.10 0.76 0.86 0.05 0.42 0.85 0.02 0.04 0.87 0.17 0 0.60 0.92 0.90 0.89 An 0.07 0.04 0.01 0.03 0.05 0.44 0.01 0 0.02 0.03 0.01 0 0.76 0.05 0 0.01 Ag 0.64 0.12 0.38 0.27 0.66 0.37 0.30 0.16 0.30 0.01 0.33 0 0.62 0.48 0.34 0.42 Bl 0.86 0.11 0.59 0.98 0.89 0 0.22 0.03 0.07 0.99 0.20 0 0.57 0.79 0.98 0.87 Ha 0.26 0.77 0.45 0 0 0 0.01 0.05 0.77 0 0.10 0.01 0 0.02 0.01 0.03 Ach 0.20 0.61 0.47 0 0 0 0.02 0.04 0.70 0.01 0.49 0.05 0.03 0.07 0.05 0.20 Mn 0.13 0 0.60 0.95 0.97 0.85 Ll 0.43 0.10 0.20 0.20 0.46 Cl 0 0 0 0.01 Gp 0.57 0.58 0.54 Su 0.86 0.89 Sn 0.92 Bb N o t e. complete dietary dissimilarity; low overlap; medium overlap; high overlap **Abbreviations: Pine Marten — Mm; Raccoon Dog — Np; Red Fox — Vv; Tengmalm’s Owl — Af; Tawny Owl — Sa; Sparrowhawk — An; Goshawk — Ag; Rough-legged Buzzard — Bl; White-tailed Eagle — Ha; Golden Eagle — Ach; Weasel — Mn; Eurasian Lynx — Ll; Grey Wolf — Cl; Pygmy Owl — Gp; Ural Owl — Su, Great Grey Owl — Sn; Eagle-Owl — Bb. 140 V. V. Ivanovskij, A. A. Sidorovich, I. A. Solovej species decreased, for 4 species was the same (table 4). Along that, the average value of the dietary similarity for selected species remained almost the same — 0.37 before 2013 versus 0.36 aft er 2013. Th e food niche breadth of predators became wider with the exception of the Pine Marten whose range of foods consumed decreased. Despite of revealed changes, the trophic structure of the community remained almost the same (fi g. 4) with the exception of the goshawk who moved to the small mammal consumers’ guild. During the study we revealed that the most common 16 species of vertebrate predators in forests of Belarussian Paazerje during the cold season formed four trophic guilds: small mammal consumers, bird consumers, scavengers, and ungulate consumers. Th e guilds comprised species from diff erent taxonomic groups and with diff erent food niche breadth. Despite of the extremely high (> 90 %) dietary overlaps within each guild the average dietary similarity for the whole community was fairly moderate — 0.37. Th e highest dietary overlaps were found for the guild of small mammal consumers. However, reduction of an actual competition between them was possible due to a selection of diff erent prey species. Voles genus Microtus, the Bank Vole, Myodes glareolus Schreber, 1780, and mice genus Sylvaemus were preferential prey and caught with diff erent frequency by diff erent predatory species (tables 1–4). Rodents have 3–5 year multiannual cycles in Belarus (Sidorovich, 2011), and periods of outbreaks alternates with periods of population declines. Predators react on changes in a small rodent abundance either with numerical responses (e. g. Weasel (Sidorovich, 2011)) or with functional responses (e. g. Rough-legged T a b l e 5 . Dietary composition (% BC) of vertebrate predators in the cold season in coniferous-small- leaved forests of Belarussian Paazerje, Northern Belarus, 2013–2019 Food items Pi ne M ar te n R ac co on D og R ed F ox T en gm al m ’s O w l T aw ny O w l Sp ar ro w - ha w k G os ha w k R ou gh -l eg ge d Bu zz ar d G ol de n Ea gl e W hi te -t ai le d Ea gl e Invertebrates 3.0 0.2 0.1 0.5 – – – 0.1 – – Fish 0.2 3.1 – – – – – – – 26.9 Amphibians and reptiles 1.7 4.3 0.2 – 10 – 0.1 – – – Small insectivores 5.9 5.4 0.4 1.3 13.7 – – 0.9 – – Small rodents, among them: 52.1 3.7 41.7 95.4 57.5 – 28.8 88.2 – – Microtus voles 17.5 3.3 29.0 73.1 19.5 – 10.9 80.9 – – Sylvaemus mice 6.2 0 0.1 10.8 6.7 – 2.5 7.0 – – Bank Vole 22.1 0.4 12.3 8.2 26.2 – 12.9 0.2 – – Water Vole – – – 0.4 – – – – – – Other small rodent species 6.3 – 0.3 2.9 5.1 – 2.5 0.1 – – Squirrel, muskrat and hedgehog 6.3 0.2 8.7 – 4.9 – 13.4 3.6 – – Hares 0.4 5.4 12.7 – – – – 0.1 26.3 8.4 Beaver – – 1.9 – – – – – – – Roe Deer and Red Deer – – – – – – – – – – Elk – – – – – – – – – – Wild Boar – – – – – – – – – – Small mustelids 0.1 – – – 3.8 – 1.4 0.3 – – Medium-sized mustelids – 1.3 – – – – 0.7 – 3.6 7.2 Red Fox and Raccoon Dog – 1.0 – – – – – – 17.7 10.9 Domestic animals – 0.4 – – – – 2.3 – 7.3 – Carrion of wild animals, among them: 19.8 56.8 28.7 – – – 0.6 6.8 26.3 37.2 Beaver 0.5 20.5 – – – – – 1.2 – – Cervids 19.3 33.3 23.4 – – – 0.6 5.5 22.1 31.2 Wild Boar – 3.0 5.3 – – – – 0.1 4.2 6.0 Small birds 4.4 2.8 0.9 2.9 3.6 100 23.2 – – – Medium-sized and big birds 4.0 3.2 2.9 – 6.5 – 29.5 – 18.9 9.3 Bird eggs 1.8 0.5 – – – – – – – – Seeds, fruits and vegetables 0.3 9.2 1.8 – – – – – – – Other – 2.5 – – – – – – – – Number of food specimens (n) in the analysed samples (m), n (m) 181 (87) 305 (198) 381 (127) 104 (83) 342 (70) 93 (43) 108 (65) 211 (123) 48 (48) 77 (77) Levins’ index (B) of food niche breadth 3.09 2.91 3.55 1.10 2.71 1.00 4.12 1.28 4.7 4.1 141Changes in the Trophic Structure of the Vertebrate Predator Community with Emphasis... Buzzard (Sidorovich, 2016) or both (e. g. Red Fox (Sidorovich et al., 2006; Sidorovich et al., 2010). Another mechanisms of reduction of competition is a merge in daily activity and habitat use as it takes place for example for the Rough-legged Buzzard and Great Grey Owl (Ivanovskij, 2012).Th us, the trophic structure of the community is not static and shift s all the time. During the warm period ecological carrying capacity of the environment and prey accessibility is much higher than that in the cold season so it is much easier to fi nd alternative food resources. Th at is why the cold season is the crucial period for the surviving for the most predatory species. In the guild of bird consumers, the same patterns lead to a more effi cient resource partitioning. Selection of diff erent prey species was found for the Sparrowhawk and Gashawk (tables 1 and 2), and a diff erent daily activity time is attributable for the Sparrowhawk and Pygmy Owl. Kills of large predators such as the Wolf and Lynx are essential supply of carrion for scavengers (Sidorovich et al., 2000), so shift in the diet of large predators is the primeval cause of changes in resource partitioning between scavenging species. Scavengers cannot escape direct competition, and the scarcity of mammalian carrion may have negative consequences for their population dynamics. During our study we reveal that physical encounters between White-tailed and Golden Eagles near carrion took place quite oft en, while the rest scavengers fed on carrion without direct interference. Anthropogenic disturbances oft en alter patterns of community functioning. Along that, how interacting species respond to these changes remains poorly understood. Usually resource scarcity leads to a greater trophic similarity due to more frequent utilization of remained resources. However, in our study, recent decrease in abundance of carrion in a result of depopulation of Wild Boars did not caused signifi cant structural changes in the community although the dietary composition of all carrion consumers have been changed. Th e average dietary similarity in the community stayed almost the same showing compensatory mechanisms in resource partitioning in the community. Fig. 4. Dietary similarity of 10 vertebrate predators in the cold season in Belarussian Paazerje, 2013–2019. 0 0,12 0,24 0,36 0,48 0,6 0,72 0,84 0,96 Similarity Golden Eagle Raccoon Dog White-tailed Eagle Goshawk Tengmalm's Owl Rough-legged Buzzard Tawny Owl Red Fox Pine Marten Sparrowhawk 142 V. V. Ivanovskij, A. A. Sidorovich, I. A. Solovej References Böhme, G. 1977. Zur Bestimmung quartärer Anuren Europas an Hand von Skelettelementen. Wissenschaft liche Zeitschrift der Humboldt-Universitat zu Berlin, Mathematish-Naturwissenschaft liche Reihe, 1977, 26, 283–300. 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Received 17 January 2021 Accepted 3 March 2021 << /ASCII85EncodePages false /AllowTransparency false /AutoPositionEPSFiles true /AutoRotatePages /None /Binding /Left /CalGrayProfile (Dot Gain 20%) /CalRGBProfile (sRGB IEC61966-2.1) /CalCMYKProfile (U.S. Web Coated \050SWOP\051 v2) /sRGBProfile (sRGB IEC61966-2.1) /CannotEmbedFontPolicy /Error /CompatibilityLevel 1.4 /CompressObjects /Tags /CompressPages true /ConvertImagesToIndexed true /PassThroughJPEGImages true /CreateJobTicket false /DefaultRenderingIntent /Default /DetectBlends true /DetectCurves 0.0000 /ColorConversionStrategy /CMYK /DoThumbnails false /EmbedAllFonts true /EmbedOpenType false /ParseICCProfilesInComments true /EmbedJobOptions true /DSCReportingLevel 0 /EmitDSCWarnings false /EndPage -1 /ImageMemory 1048576 /LockDistillerParams false /MaxSubsetPct 100 /Optimize true /OPM 1 /ParseDSCComments true /ParseDSCCommentsForDocInfo true /PreserveCopyPage true /PreserveDICMYKValues true /PreserveEPSInfo true /PreserveFlatness true /PreserveHalftoneInfo false /PreserveOPIComments true /PreserveOverprintSettings true /StartPage 1 /SubsetFonts true /TransferFunctionInfo /Apply /UCRandBGInfo /Preserve /UsePrologue false /ColorSettingsFile () /AlwaysEmbed [ true ] /NeverEmbed [ true ] /AntiAliasColorImages false /CropColorImages true /ColorImageMinResolution 300 /ColorImageMinResolutionPolicy /OK /DownsampleColorImages true /ColorImageDownsampleType /Bicubic /ColorImageResolution 300 /ColorImageDepth -1 /ColorImageMinDownsampleDepth 1 /ColorImageDownsampleThreshold 1.50000 /EncodeColorImages true /ColorImageFilter /DCTEncode /AutoFilterColorImages true /ColorImageAutoFilterStrategy /JPEG /ColorACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /ColorImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000ColorACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000ColorImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasGrayImages false /CropGrayImages true /GrayImageMinResolution 300 /GrayImageMinResolutionPolicy /OK /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageMinDownsampleDepth 2 /GrayImageDownsampleThreshold 1.50000 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /GrayImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000GrayACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000GrayImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasMonoImages false /CropMonoImages true /MonoImageMinResolution 1200 /MonoImageMinResolutionPolicy /OK /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 1200 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.50000 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict << /K -1 >> /AllowPSXObjects false /CheckCompliance [ /None ] /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile () /PDFXOutputConditionIdentifier () /PDFXOutputCondition () /PDFXRegistryName () /PDFXTrapped /False /CreateJDFFile false /Description << /ARA /BGR /CHS /CHT /CZE /DAN /DEU /ESP /ETI /FRA /GRE /HEB /HRV (Za stvaranje Adobe PDF dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. 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