Food habits of Zamenis longissimus (Laurenti, 1768) (Reptilia: Serpentes: Colubridae) in Bieszczady (south-eastern Poland)

The paper presents the results of research on the food contents of the Aesculapian snake Zamenis longissimus in Bieszczady (south-eastern Poland). Over the period of 20 years 43 dead individuals of the species of varied age were found in the valley of the San river at the foot of Otryt hills. 116 victims were recorded in 40 (93 %) stomachs fi lled with food contents, among which vertebrate, and in particular small mammals prevailed (e. g. Sorex sp., Apodemus sp., Microtus sp. and Clethrionomys sp.). Food of adult snakes (89–159.7 cm; n = 32) also included bird eggs. Food of individuals classifi ed as young (27.5–67.5 cm; n = 8), apart from vertebrate (mainly Lacertidae) included invertebrate (Coleoptera and Oligochaeta). The research indicates that food contents of this relatively small population of the Aesculapian snake can be signifi cantly diversifi ed and dependent on age.


Introduction
The Aesculapian snake Zamenis longissimus inhabits a vast, yet dispersed area from the north eastern part of the Iberian Penninsula to the eastern coast of the Black Sea.The southern range of the species includes sites in Greece, several islands of the Mediterranean Sea and isolated locations in Caucasus, in north-eastern Turkey and north-western Iran.Northernmost isolated sites in Europe are located in Germany, Czech Republic and Poland (BÖHME, 1993;HEIMES & WAITZMANN, 1993;NAULLEAU, 1997;MIKÀTOVÀ & ZAVADIL, 2001;NAJBAR, 2004;EDGAR & BIRD, 2006).
All above mentioned authors stress that on many locations of the species, isolated populations are particularly endangered by extinction and hence any information concerning their biology and ecology is extremely precious.
The composition of the snake's food is not well recognized in Poland, the most exhaustive account con-cerning this is issue can be found in NAJBAR (1999).Other data relate either to more recent but not numerous fi eld observations (NAJBAR, 2004), or information on isolated cases of individuals coming from Bieszczady and kept in breeding conditions (CAIS, 1963;JUSZCZYK, 1987).

Study area
Bieszczady area is located in south-eastern Poland, in the region of Eastern Carpathia, between the Łupkowska pass (640 m above sea level), the valley of the Osława river, Użocka pass (852 m above sea level) and the source of the San river on the border with Ukraine (KONDRACKI, 2001).It is a mountainous area of average height, whose highest peak -Tarnica is located at the altitude of 1346 m above sea level.The climate in the region is changeable due to both conti-nental and oceanic impact (WOŚ, 1996).The average temperature is above 6.5 °C, in the winter half-year -1 °C and in the summer half-year 13 °C.Average annual temperatures on the altitudes above 800 m above sea level do not go beyond 4 °C.The vegetation period lasts between 190 and 210 days (MICHNA & PACZOS, 1972;ZEMANEK, 1989).
Bieszczady is one of the most dense forest areas in Poland, rich in terms of various geological forms and almost natural fl ora.Fagetum carpaticum is a dominating forest type.Deforested areas are overgrown by various forms of fl ora, most of them are at the stage of succession.The area is sanctuary of many rare species of fauna.Most of the region, due to its natural characteristics is subject to protection, and the area inhabited by the biggest population of the Aesculapian snake is located in the San Valley Landscape Park founded in 1992, part of the Bioshere Reserve "Eastern Carpathia" (Fig. 1) (ZZKPK, 2002).

Material and methods
The research material analyzed in this paper was collected between May and September in the years 1984-1987 and 1990-2005.The contents of snakes' stomachs was examined.
The gender of the snakes was established on the basis of calculation of the ratio of the total length to the length of the tail, the shape of base of the tail and probing the cloacae.In view of the fact that Aesculapian snakes attain sexual maturity once they have reached the length of approximately 90 cm (e.g.BESZKOW, 1975;NAJBAR, 2000), apart from providing a general characteristics of the composition of the snake's food, the paper introduced the division into juvenile/subadult (27.5-67.5 cm) and mature (89-159.7 cm) individuals.
Invertebrate are sporadically devoured by young individuals.Remains of Necrophorus sp. were observed in a 27.5 cm long female, whereas remains of Lumbricus sp. were identifi ed in a female, whose length was 49.7 cm.
The largest victims were observed in the stomachs of a 136.7 cm male (3 juv.Myoxus /Glis/ glis), a 144 cm long female (juv.Talpa europaea) and a 147.9 cm long male (ad.M. glis and ad.T. europaea).

Discussion
The research indicates that food contents of the Aesculapian snake in Bieszczady can be diversifi ed (Tab.1).
The availability of victims in the environment is most probably subject to seasonal changes, but the specifi c periods when dead males and females were found did not vary (periods are understood here as particular months, irrelevant of the year in which snakes were found) (Kolmogorov-Smirnov test D = 0.048, P > 0.10, N = 34).
The length of the snakes in which food was observed did not differ from the length of the individuals with empty stomachs (test t, t = 0.53, df = 41, P = 0.60), and similarly the length of adult males did not differ from the length of adult females (test t, t = 0.80, df = 30, P = 0.42).
In the case of snakes in which food was observed it was checked whether the presence of particular types of victims (mammals, birds, reptiles or other groups i. e. amphibians or invertebrates) is connected with the length of the snakes.For this purpose four U tests were carried out and data was analysed taking into consideration Benferroni's correction at the P = 0.0125 signifi cance level.The correlation between the length of the snakes and the presence of mammals, birds or reptiles in their stomachs was as follows: for mammals Z = 0.30, P = 0.76, for birds Z = 0.87, P = 0.40, for reptiles Z = 1.48,P = 0.14, and for amphibians and invertebrates Z = 3.07, P = 0.0022.
The data concerning the composition of the food of Zamenis longissimus in Bieszczady presented above suggests diversifi cation and changes conditioned by the age of the snakes.Young individuals hunt mainly for lizards, fairly common in the region, which is compatible with the data provided by ARNOLD & BUR-TON (1979) or LUISELLI & ANGELICI (1996).They also eagerly hunt for small mammals, and the amount of the remains of such victims rises with the snakes age.Compared to various other European populations of the species it occurs that mammals (along with lizards and birds) constitute the basic element of the food of adult individuals, which has been observed by many researchers (e.g.: VASÁRHELYI, 1965;BRUNO et al., 1973;BESZKOW, 1976;SZCZERBAK & SZCZERBAN, 1980;BRUNO & MAUGERI, 1990;REHÁK et al., 1992;LUISELLI & RUGIERO, 1993;NAULLEAU & BONNET, 1995;CAPIZZI & LUISELLI, 1996).Some authors e. g.BARBADILLO (1987) or BRUNO & MAUGERI (1990) observe that in some regions of Europe young snakes devour also amphibians and invertebrate, which well corresponds to the results obtained in Poland.According to CAPIZZI et al. (1995) in case of this species, the composition of food is conditioned mainly by the density of the populations of victims in the environment.
Other, not mentioned victims, which are enumerated in the table, had signifi cantly less important, in terms of percentages, or even marginal share in the food contents of the snakes examined (Tab.1).
3 (7 %) stomachs were empty, the remaining 40 (93 %) were fi lled with chime.116 victims of the snakes were identifi ed.Mammals constituted the most numerous group, out of which prevailed: common shrew Sorex araneus, yellow-necked mouse Apodemus fl avicollis, orkney vole Microtus arvalis, shrews Sorex sp. and bank vole Clethrionomys glareolus.The second group of victims, in terms of quantity, included reptiles out of which prevailed viviparous lizard Zootoca vivipara, and slow-worm Anguis fragilis.In the researched region Aesculapian snakes also hunt for common bird species, in particular house sparrow Passer domesticus and spotted fl ycatcher Muscicapa striata.

Table 1 .
Food habits of Zamenis longissimus in the study area.