The changes in the number of wild living fur animals in Poland (Bydgoszcz hunting region) in years

Roczniki Naukowe Polskiego Towarzystwa Zootechnicznego, t. 5 (2009), nr 4 The changes in the number of wild living fur animals in Poland (Bydgoszcz hunting region) in years 2001-2008 Natasza Święcicka l, Stanisław Kubacki l, Eliza Malczyk'', Monika Monkiewicz l lthe University oftechnology and Life Sciences in Bydgoszcz, Department of Horse Breeding and Fur Animals, Mazowiecka 28, 85-084 Bydgoszcz 1'he Polish Hunting Association, District Administration in Bydgoszcz, Sułkowskiego 5, 85-655 Bydgoszcz The aim of the research was to carry out the analysis of the population of wild living fur animals in Bydgoszcz hunting region in years 200112002-2007/2008. The highest mea n number of individuals, among ali the analysed predators, was recorded in the number of a common fox (red fox) -7115 individuals, Its population in the Bydgoszcz region increased by 160 individuals per year (y'= 159.93x + 6475). The second place in terms of the number of individuals was found for a raccoon dog (2310 individuals). We can draw conclusions that the increase (positive trend) of the number of foxes, raccoon dogs, martens or badgers had - in the investigated period of time - an influence on the population of ahare, whose rate per 100 hectares was on the level of 1.87 individuals. As a resuit of the conducted analysis, there has been shown the decrease of a muskrat population (53 individuals per year) which can be connected with a signiflcant increase of the population of an American mink in this area (63 individuals per year on the average). KEY WORDS: wild living fur animals / the size of the population / tendencies The size evaluation of the population of animais and the direction of their development has a basie significance for the working out and application of the correct rules in carrying on the suitable hunting economy [27]. The dynamics of the increase ar decrease of the num ber of animais in certain area depends on the state of environment. The progressive degradation of the environment, as Iasting for almost 50 years, influenced very strongly the decrease in the population of different species of animals. It is, therefore, important to regulate the num ber of animals by the carrying out the year plans of shooting animals and the knowledge of the increase of the number of individuals, that among all the other animals bom in a certain year survived to the next 275

economy year. The knowłedge of these issues enabłes to observe the correct proportion of particułar species of animałs and their structure in the herd. Materiał and methods The data for the research were obtained from the year hunting p!ans collected from the Bydgoszcz region of the Polis h Hunting Association. The surface area of the analysed region is 850084 hectares, including 256 965 hectares of forests and 593 119 hec tar es of fields. The research materia! comprised the data concerning fur animals on the list of hunting animals in the years 2001-2008. The statistical characterization of the population was carried out on the basis of the state of the number of animals according to the registration on the 15 th March for all the hunting areas in the Bydgoszcz region of the Polish Hunting Association. On the ground of the above data the trend line was całculated and presented as a function of the first degree y' = a + bx where: a - means the ordinate of the intersection of the straight line with y-axis; b - the coefficient of the straight line; x - an operand (time). For the particular trend lines, the vałue of the correlation coefficient was całculated Jxy (Statistica 8.0) assuming: x - the following years as an operand, y - the trend line as a dependent variable. On the basis of the planning parameters of the annual hunting plans, the num ber of hares was presented by the całculated population per 100 hectares of the field circuit of the Bydgoszcz region: x = the num ber of counted hares (x) I the surface area of the field circuits of the Bydgoszcz region * 100 In case of a fox the num ber of population was całcułated per 1000 hectares of the total area of the circuits of the Bydgoszcz region: x = the number of counted foxes (x) I the surface area of the circuits of the Bydgoszcz region * 1000 Also the rate of intensity of exploitation of the popułation of particular species of hunting fur animałs in the whole region of Bydgoszcz during the eight years of the research in particular hunting seasons was całculated according to the following formuła, mak ing use of the earlier publications by Bombik et al. [5]: the intensity rate of the exploitation of population (%) = the numper of shot animałs I the number of population according to the state on the 15 th of March * 100% Results and discussion The Table l presents the data concerning the size of the population of wild living fur animals in Bydgoszcz hunting region in years 2001-2008. As a result of the perfor- 276

Table 1 - Tabela 1 The statistical characterization and the level of exploitation' of wild living fur animals population from Bydgoszcz hunting region in years 2001-2008 Charakterystyka statystyczna oraz poziom eksploatacji) populacji dziko żyjących zwierząt futerkowych pochodzących z bydgoskiego okręgu łowieckiego w latach 2001-2008 Species Liczba zwierząt - Number of anirnals The level Gatunek of exploitation x V% min max of population Poziom eksploatacji populacji Raccoon dog 2310 12.06 1873 2623 26.40 Jenot Common fox 7115 5.38 6665 7662 81.55 Lis pospolity Badger 1520 17.50 1058 1925 4.27 Borsuk Matten 2042 13.06 1621 2410 3.95 Kuna Polecat 1468 17.51 1335 1767 3.26 Tchórz American mink 374 36.26 204 578 3.57 Norka amerykańska Muskrat 1209 21.17 1005 1729 91.22 Piżmak Hare 11 139 12.65 10 548 12301 2.46 Zając Wild rabbi t 1315 23.60 713 1705 0.35 Dziki królik Raccoon 29 12008 4 79 0.00 Szop pracz )exploitation = the number of shot anirnals / the number of the who le population according to the state on the 15,h March x 100 )eksploatacja = liczba pozyskanych zwierząt / liczebność populacji zwierzyny według stanu na 15 marca x 100 med calculations it has been recorded that the highest number of animals among the hunting predators in the investigated eight years of the research, presented the population of the common fox (about 7115 animals on the average). The size of the population of this species in the particular years was found more or less on the same level and it refiected low variabiiity rate (5.38%). In spite of the regular shooting of foxes their number in the Bydgoszcz region increased every year by about 160 individuals (the increase statistically significant - Table 2). The increase in the number of animals was caused by the lack of the naturai enemies in the environment. According to the planning parameters, made in the year hunting plans, the density of the population in the Bydgoszcz region counted per 1000 hectares of the total surface area of the circuits is more or less 2 pairs of animals per 1000 hectares. The number of 277

Table 2 - Tabela 2 The tendency line (trend) ofwild living fur anirnals (according to the record) frorn Bydgoszcz huntingregion in season 2001-2008 Linia tendencji (trend) dziko żyjących zwierzątfuterkowych (według inwentaryzacji) z bydgoskiego okręgu łowieckiego w sezonie 2001-2008 Species Season Trend Gatunek Sezon 200112008 Raccoon dog I) 1873 Y= 145.86x + 1800 Jenot I) Common fox 6665 y = 159.93x + 6475 Lis pospolity Badger 1058 y = 146.36x + 934.57 Borsuk Marten 1621 y = 121.46x + 1556 Kuna Polecat 1027 y = 113.93x + 1012.1 Tchórz American mink') 262 y = 63.114x + 152.6 Norka amerykańska') Muskrat 1037 y = 53.143x + 1421.9 Piżmak Hare 7555 y = 866.32x + 7674.4 Zając Wild rabbi! 713 y = 119.36x + 837.71 Dziki królik Ixy ** ** ** Season The relative increase Sezon or decrease (%) 2007/2008 Względny wzrost lub spadek (%) 2623 8.10 7403 2.47 1925 15.66 2410 7.80 1767 11.25 578 41.36 1036 3.74 14243 11.29 1705 14.25 1).2) _ trend from the season 200212003-200712008 - trend od sezonu 200212003-200712008 Correlation rate (rx) significant: * - at PSO.05; ** - at PSO.OI Współczynnik korelacji (rxy) istotny: * - przy PSO,OS; ** - przy PSO,OI animals ranged from 7.84 individuals per 1000 hectares (year 2002) to 9.01 individuals per 1000 hectares (year 2007). The mean number of foxes in Bydgoszcz region was 7115 animals and it gives 8.37 animals per 1000 hectares (Table 3) and it is more than 4 pairs. The ratio is twice as big as the mean num ber of animals of thjs species accepted in the rational hunting economy. We can assume that one of the reasons for an increased size of the population of this species is an influence of dropped vaccines against the rabies that immune these animals [27] and as a result decreases the naturai lethality of the fox. The Iimitation of presence of this illness may lead significantly to the increase in the number of this species in hunting areas of Bydgoszcz region and even shooting these anima1s beside quick reproduction of this species will not lead to the decrease in the population. In spite of the fact that shooting foxes increases along with its number, Iimitation of the number of foxes in hunting areas is difficult because of the migrations of animals through different hunting club circuits and constant coming of new individuals in this area. These animals cause losses of the livestock. However big alimentary diversity puts it very high in the food chain and lets him survive and enables a development in certain environment. In the naturai environment the diet of the common fox comprises: 20-30% a field mouse, about 22% meat of a rabbit and the remaining mammals 10% [15]. 278

Table 3 - Tabela 3 According to Fruziński [12], the The population of common foxes in the Bydgoszcz region (the number of individuals) diet of the fox may contain meat Stan pogłowia lisów pospolitych w okręgu bydgoskim of the big game for example a y- (sztuk) oung buck. Big expansion of the fox in Year Population The number of individuals Rok Stan poglowia per 1000 hectares the area of Poland leads to the Sztuk na 1000 hektarów decrease of the population of other animals. According to many 6665 7.84 2002 2003 6765 7.95 authors [7, 14, 25, 28], the fox is 2004 6768 7.96 a species which limits significantly the number of smali game, es- 2005 7302 8.58 2006 7238 8.51 2007 7662 9.01 pecially a partridge, a pheasant 2008 7403 8.70 and ahare. Kubacki et al. [21], 7115 8.37 analyzing the number of animals in Podanin forest inspectorate, stated balanced level of hares that results from the decreasing population of their natural enemy in the environment - the fox. Regular shooting the foxes is important in order not to lead to the disorder of the hunting economy in the country. According to the research of Skoczylas et al. [30] who analysed the number of the population of the common fox in Szczecin region, keeping the shooting foxes on the low level leads to the increase of the number of foxes. A raccoon dog is another spreading predator in Poland. The colonization by raccoon dogs took place by individuals introduced to the population in Lithuania, Ukraine, and Belarus [24]. Raccoon dog has spread since the 50-ies in the past age and perfectly adjusted to our land [10]. According the own research the number of raccoon dogs in the area of Bydgoszcz hunting region during the eight analysed years increased on the average by 146 animals per year (Table 2). The numerical state of the raccoon dog was about 2310 animals (Table l), which places it in terms of the size of the population of hunting predators on the second position just after the common fox. It has been noticed that the level of exploitation of the population of foxes between 2001-2008 was higher than that of the raccoon dog and ranged between 70-90%; on the other hand, the raccoon dogs population was on the stable level of 20-30% (Fig.). The raccoon dog can, as well as the fox, adjust to different conditions. It feels better by the water. A broad spectrum of its diet shows (we must keep in mind that it is an omnivorous animai) that it is not a big threat to the native species. Finnish research showed that the ratio of overlapping feeding niches for the fox and raccoon dog was only 0.36. The fox ate more hares and birds than the raccoon dog [19]. Similar observations were made in the research carried out in Białowieża Woodland [17]. The observations carried out in Scandinavia suggest significant differences in the diet of the fox and raccoon dog [6]. In Scandinavia and Estonia it has been noticed that the fox in comparison to the raccoon dog hunted on bigger victims as: hares, muskrats and birds [19,23]. The research carried out in Poland proves that foxes specialize in eating small 279

cf. 120 100 --*- ra=on dog - jenot -+- common (red) fox - lis pospolity 80 60 40 20 O+-----~------~----~----~------~----~----~ 200112002 200212003 200312004 200412005 200512006 200612007 200712008 years-iata ---- badger-borsuk --*- marten-kuna polecat- tchórz -+-- American mink-notka amerykańska 6,5 6 5,5 5 4,5 4 3,5 3 2,5 2 '1,5 1 0,5 O+-----~------~----~----~------._----~----, 200112002 200212003 200312004 200412005 200512006 200612007 200712008 years-iata ;!. 12 200112002 200212003 200312004 2004[2005 2005[2006 2006/2007 2007.12008 years -lata Fig. The level of exploitation (see Table I) of the population of animals in particular hunting seasons Rys. Stopień eksploatacji (patrz tabela I) populacji zwierząt w poszczególnych sezonach łowieckich 280

mammals and birds; the raccoon dog eats plants, amphibians, reptiles and carrion. Moreover, this predator eats large quantities of shrews and animals which because of its smeli and taste are avoided by the fox [17, 18, 29]. Kluczyńska et al. [20] showed that the increase of the population of the fox and raccoon dog is negatively correlated with the increase in the number of hares or partridges. During the whole analysed period the number of hares increased by 866 individuals per year - the increase is significant (the relative increase is 11.29%). Taking into consideration the size of the area of ali the 146 leased circuits, the mean density of hares, in the investigated period of time, was 1.87 animals per 100 hectares of the field size of the area (Tab le 4). The plans of shooting hares were approved in these circuits in which the density in spring was 5 animals per 100 hectares. According to the information obtained from the headquarters of the Polish Hunting Association in Bydgoszcz it appears that from 1981/1982 to 200112002 seasons, the state of hares showed decreasing tendency. The increase of the state of hares was noticed in several seasons. In years 1997-2002 the number of hares deciined so drasticaliy that shooting was forbidden. A significant increase in the number of hares in Bydgoszcz region has been noticed since the season 200112002 (y = 866.32x + 7674.4). At the same time the number of circuits in which shooting of hares is permitted increases. The factors reducing the number of the hare population might be both the development of civilization, intensification of agriculture, the increasing number of predators or the environmental poliution [8, 11]. The undertaken attempts to restore the population of hare in Poland by improvement of the environmental conditions, reintroduction and breeding in the pens, settling in the hunting fields lead to the increase of the num ber of these animals [3,4]. The most important reason among other factors reducing the number of the population of this species in the 90-ies of XX century was the appearance of the epidemie virus of hares that is the European Brown Hare Syndrome Virus (EBHS) [9]. It is very important to carry out special prophylaxis in order to prevent such events. Much worse is the situation of another species - a herbivorous muskrat. In the own research it has been ascertained a gradual deciine in population of these animals. From 200 l to 2008 year the number of muskrat deciined by 53 animals per year on Table 4 - Tabela 4 The population of hares in the Bydgoszcz region (the the average. The ratio of exploitation number of individuals) of the muskrat population deciined in Stan pogłowia zajęcy w okręgu bydgoskim (sztuk) season 2005/2006 to the level of 1% Year Rok 2002 2003 2004 2005 2006 2007 2008 Population Stan pogłowia 7555 10702 10817 10548 II 812 12301 14243 The number of individuałs per 100 hectares of field Sztuk na 100 hektarów terenu polnego 1.20 1.80 1.80 1.77 1.99 2.07 2.40 II 139 1.87 (Fig.). The deciine in the number of muskrat observed also Kluczyńska et al. [20] who analysed the number of smali game in Osie forest inspectorate. The probabie reason of the deciine in population of muskrat might be the increase of the number of the waterland predators such as an American minko The presence of this species of 281

animals in Bydgoszcz region has been noted for the first time in season 2002/2003. From this time the size of the researched population from one year to another increased (63 animals on the average). The relative increase of the trend!ine was 41.36% which indicates very intensive development of this species of animals. The level of exploitation of the population, in the investigated period, was much diversified. The highest ratio was noticed in season 2004/2005 - almost 4% and in season 2007/2008 - about 6%. The main food of minks included fish, amphibians and rodents. In Białowieża Woodland it has been noticed that muskrats we re a good delicacy [34]. Minks are often the main predators among the bird's nests. This diversification of mink's food is the key to success which have lasted for a few tens of years of the colonization of Europe by these animals. The analogous situation was observed also in case of other weasel's animals occurring in the area of Bydgoszcz region (a marten, a badger and polecat). Particular attention should be paid to the population of the polecat which during the eight years increased significantly. The carried out observation proved that the number of polecats increased every year by 113 individuals (Table 2) and the ca1culated straight line of the trend for the badgers or martens showed increasing tendency. In the last analysed seasons in hunting circuits of the Bydgoszcz region it has been noticed the presence of a new species that is a raccoon. It has been noticed for the first time in season 2004/2005, at that time there were only 4 animals. In the last investigated period of time 79 individuals of this species have been noticed and it proves a perfect acclimatization of the raccoon in our territory. According to Hoffrnann and Gottschang [16], the raccoon is a threat to the native rare species such as forest hens, thrushes, water and marsh birds. Moreover, this species is thought to be a carrier of rabies [32], parasites and nematodes [l]. Gębczyńska and Raczyński [13] think that from the point of view of the protection of the native fauna and hunting economy this species is redundant in Poland. The conducted analysis revealed the increase in the num ber of population of the wild fur animals with the exception of the muskrat which had a decreasing tendency. The increase of the common fox, polecat and the American mink was statistically significant. We can presume that the showed increase (a positive trend) of the number of raccoon dogs, martens and badgers had an impact on the population of hares which in spite of the increasing tendency still shows relatively low ratio per 100 hectares of the surface area in Bydgoszcz region (1.87 animals). REFERENCES l l. BARTOSZEWICZ M., OKARMA H., ZALEWSKI A., SZCZĘSNA r., 2008 - Ecology of raceon (Procyon lotor) from western Poland - preliminary results. Annales Zoologici Fennici 45, 291-298. 2. BARTOSZEWICZ M., 2004 - Wpływ norki amerykańskiej Musrela vison na ptaki wodne a strategia ich ochrony w Parku Narodowym "Ujście Warty". Rozprawa doktorska, Instytut Ochrony Przyrody PAN w Krakowie. 282 ~. I j

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