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Distribution and Habitat Use of Dice Snakes (Natrix tessellata) in Slovenia


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The dice snake (Natrix tessellata) is a protected species in Slovenia, whose distribution is incompletely known and only little information about its habitat use is available. We analyzed historical and recent distributional data and performed a study of habitat use to acquire relevant information for the conservation of dice snakes in Slo-venia. Using a line transect method, we compared habitats at localities of recorded dice snakes with habitats available next to the line transects in four buffer zones (10, 20, 50, and 100 m distant from the transect). All transect lines were located in areas of less than 1 km from the rivers Sava and Kolpa. In order to get a better idea on habitat selection , habitat use including all precise localities (n = 117) of dice snakes in Slovenia was analyzed. Dice snakes were recorded mainly in the lowlands throughout the country, but were rare in the northeastern part. Its presence in the river Kolpa was confirmed for the first time. More than 75% of observations were recorded within 10 meters from a water body. To a minor degree, snakes selected grasslands and urban areas along the Sava River and land covered with shrub vegetation at the Kolpa River. Forest habitats as well as agricultural land with herbaceous plants were avoided along the Sava River.
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© 2011 Deutsche Gesellscha für Herpetologie und Terrarienkunde e.V. (DGHT), Rheinbach, Germany
Distribution and Habitat Use of Dice Snakes (Natrix tessellata)
in Slovenia
A Ž, M K, M G  K M
Abstract. e dice snake (Natrix tessellata) is a protected species in Slovenia, whose distribution is incompletely
known and only little information about its habitat use is available. We analyzed historical and recent distributional
data and performed a study of habitat use to acquire relevant information for the conservation of dice snakes in Slo-
venia. Using a line transect method, we compared habitats at localities of recorded dice snakes with habitats avail-
able next to the line transects in four buer zones (, , , and  m distant from the transect). All transect lines
were located in areas of less than  km from the rivers Sava and Kolpa. In order to get a better idea on habitat selec-
tion, habitat use including all precise localities (n = ) of dice snakes in Slovenia was analyzed. Dice snakes were
recorded mainly in the lowlands throughout the country, but were rare in the northeastern part. Its presence in the
river Kolpa was conrmed for the rst time. More than  of observations were recorded within  meters from
a water body. To a minor degree, snakes selected grasslands and urban areas along the Sava River and land covered
with shrub vegetation at the Kolpa River. Forest habitats as well as agricultural land with herbaceous plants were
avoided along the Sava River.
Key words. Squamata, Serpentes, Natrix tessellata, Slovenia, distribution, habitat use
Knowledge of the habitat use of endangered species is
crucial for many applications, such as eective manage-
ment, impact assessments, and preparation of conserva-
tion strategies. In Slovenia, Natrix tessellata is a species
protected by European (included in Annex IV of Habi-
tat Directive //ECC, and Bern Convention )
and national legislation (Decree on the Protection of
Endangered Animal Species ), classied in the cat-
egory V as a vulnerable species according to the criteria
of the Red List of threatened plant and animal species
of Slovenia (Red Data List ). is classication was
made on the basis of scarce distributional data and in-
sucient knowledge of the status of dice snakes in Slo-
venia and would require a revision when more data be-
come available. On joining the European Community in
, Slovenia also embarked on the task of implement-
ing the Habitat Directive by designating special areas of
conservation (SAC) as a part of the Natura  net-
work. However, the dice snake is not included in Annex
 of the Habitat Directive, for which SAC should be des-
ignated. It is an “Annex -species”, which concludes that
dice snakes should be protected at all sites where they
are found naturally. However, scarce and incomplete
data on their distribution render this a dicult task. Hi-
bernation sites should also receive special attention of
conservation (C  N , C et
al. , V et al. ), but locations of such sites
are not yet known in Slovenia. ough, the dice snake is
included in all impact assessments, in most cases its sta-
tus of an “Annex -species” is not properly considered
comparing to other species. Consequently, Slovenia, by
our opinion, did not implement the Habitat Directive
which is the motivation for studies, such as the one pre-
sented herewith.
As a typical member of the genus Natrix, dice snakes
are good swimmers and divers and because of their
main prey, sh, they are bound to aquatic habitats
(K ). During the active season they remain
in the immediate vicinity of surface water at a distance
of less than  m to the water (C  N
, C et al. , N  M ,
V et al. ). Its use of habitat is therefore re-
stricted to a rather narrow belt surrounding suitable wa-
ter bodies with abundant sh, which has been shown
in many studies of herpetofaunal communities or relat-
ed ecological studies of dice snakes (e.g. L  G-
 , F et al. , M , ,
C-M et al. ). Only few anecdotal re-
cords on the diet of dice snakes from Slovenia are avail-
able, which include the bullhead (Cottus gobio), brown
trout (Salmo trutta), chub (Squalius cephalus), and frog
tadpoles (Rana sp.) as prey items (C  K
, F. K pers. comm., and our pers. obs.).
According to T () the dice snake occurs
throughout Slovenia, mainly along lowland rivers with
dense vegetation. It is also common on the coastal part
of the country at semi-saline water bodies (M ,
T ). Interestingly, it has also been recorded
in one of the karstic caves of northern or central Slo-
venia (N ). Previous data suggested that the
dice snake was missing from two major rivers (Drava
and Kolpa), since there was only one nd of a dice snake
from the upper section of Drava River and one from the
lower section of Kolpa River (T ). Besides these
generalizations and anecdotal records about the occur-
MERTENSIELLA 18 207-216 20 September 2011 ISBN 978-3-9812565-4-3
A Ž, M K, M G  K M
rence of dice snakes, no study on habitat use by the dice
snake has been accomplished in Slovenia. We present
herewith a review on the distribution of the dice snake
in Slovenia, supplemented with new data, an analysis of
altitudinal distribution, and habitat use on a national
Some studies on habitat use applied absolute fre-
quencies (e.g. C et al. ), without considering
habitat availability in the study area. On a regional scale
we focus on a comparative analysis of habitat use of dice
snakes in relation to habitat availability. is could pre-
sent a basis for ecient conservational guidelines for
this species in Slovenia and abroad.
Material and Methods
Study Area
Two separate study areas were included in our analysis
of habitat selection: study area “Sava Site” denes a lower
section of Sava River between Krško and Brežice (south-
east Slovenia, lat. ˚’’’N, long. ˚’’’E, mean al-
titude  m a.s.l.); study area “Kolpa Site” is a middle
section of the Kolpa River in Slovenia between Kuželj
Fig. 1. Typical habitat at the Sava River (Sava Site) in south-east Slovenia. Photo: M G.
Fig. 2 (right). Typical habitat at the Kolpa River (Kolpa Site)
in southern Slovenia. Photo: M K.
Distribution and Habitat of Dice Snakes in Slovenia
and Sodevci (Kuželj, lat. ˚’’’N, long. ˚’’’E,
mean altitude  m a.s.l. and Sodevci, lat. ˚’’’N,
long. ˚’’E, mean altitude  m a.s.l.). At Sava Site
the riverbed of the Sava River is regulated and the for-
merly ooded alluvial plains are today mostly convert-
ed into agricultural elds and forest plantations (MKPG
). Forested areas are newly grown but scarce and lo-
cated mostly along the river banks. Yet, the lower part of
the river Sava still represents a relatively well preserved
habitat compared to other rivers in the lowlands of Slo-
venia. e climatic conditions in this area are typical for
a temperate continental region with a precipitation of
 mm per year and an average temperature of –
°C annually (P  O A ). In con-
trast, Kolpa Site is situated in a typical karstic landscape
in the northern Dinaric Mountains with a prevalence of
carbonate rocks. e Kolpa River represents an excep-
tion since the hydrological conditions of this region are
characterized by the lack of surface water, many subter-
ranean water systems and other typical karstic phenom-
ena. is area is one of the most extensively forested are-
as in Slovenia with over  forest cover. Most common
are beech and r forest associations (Omphalodo-Fage-
tum s. lat.). e vicinity of the Adriatic Sea inuences
this region, characterized also by its relatively high alti-
tude dierences and variable climate and weather con-
ditions. e climate is considered to be temperate con-
tinental and mountainous with average temperatures
Fig. . Study areas: the upper map (1) shows the study area Sava Site and the bottom map (2) represents the study area Kolpa
Site with transect lines (red) and habitat types indicated.
around  °C and precipitation around  mm per year
(P  O A ). Typical sites of both
study areas are shown in Figures  and  and the land-
scape with habitat types and transect lines is shown in
Figure .
Field Work and Data Sets
We used a line transect method adapted for the studies
on reptiles (B et al. ). All transects were lo-
cated less than  meters from the river. At Sava Site
data were gathered from May to September of  and
, whereas at the Kolpa Site sampling lasted between
April and September from  to . Field work
was conducted in suitable weather conditions (sunny to
partly cloudy) during the day. e methods dier in the
number of inspections of transect lines; each transect
line at the Sava Site was inspected once, whereas at the
Kolpa Site inspections were repeated  times. All nds
from transect lines were included in the results. Record-
ed individuals were not marked and we treated every
nd as an individual one. Localities were taken with a
hand held GPS. Field data were recorded with a stand-
ard form, including locality, date, time, habitat type,
presence and number of associated reptile species, age
class (juveniles, subadults, adults) and sex of the speci-
mens if possible. All eld work was conducted by the
rst author.
We applied three principal data sets to investigate
habitat selection and distribution. e rst set includ-
ed data collected on line transects and was used to an-
alyze habitat selection by the dice snake on a regional
scale in both study areas. e second data set was used
for habitat use on a national scale and was drawn from
eld sampling and literature data with precise geo-ref-
erenced locations. ird, we used the database of Slove-
nian reptiles maintained at the Centre for Cartography
of Fauna and Flora (CKFF) to evaluate the distribution
of the dice snake in Slovenia based on UTM grids of  x
 km. ese data include precise localities that contain
geo-referenced information (GPS coordinates) and also
geographically less precise localities that include infor-
mation based on a wide, less precise scale (example: Mt.
Snežnik, city Krško) and lack any habitat information.
Data Analysis
Habitat availability for dice snakes in the study areas
was estimated by GIS analysis of land use data (MKGP
) in a buer zone of , ,  and  meters dis-
Fig. . Distribution of the dice snake (Natrix tessellata) in Slovenia: pink shaded represent the UTM squares that contain records,
but without geo-reference (GPS) and red dots represent precise locality data, which were also used in habitat use analysis.
A Ž, M K, M G  K M
Distribution in Slovenia
All currently known localities of dice snakes in Slovenia
are distributed across  UTM squares of  x  km
Fig. . Available habitat types (transects) and habitat types
used by dice snakes (Natrix tessellata) (localities) at study
area Sava Site with buer zones of 10, 20, 50 and 100 meters
around transect lines or capture sites. Habitat types are: water
body (W), urban land (U), forest (F), shrubs (S), grassland
(G), agricultural land with woody plants (AW), and agricul-
tural land with herbaceous plants (AH).
Fig. . Proportion of capture sites of dice snakes (Natrix
tessellata) in relation to the distance from the nearest water
body in Slovenia (n = 117).
Fig. . Available habitat types (transects) and habitat types
used by dice snakes (Natrix tessellata) (localities) at study area
Kolpa Site with buer zones of 10, 20, 50 and 100 meters
around transect lines or capture sites. See Fig. 6 for legend
on habitat.
tance from all inspected transect lines. Next, we cal-
culated habitat composition for dice snakes by apply-
ing circle buers around individual snake nds with
the perimeter of , ,  and  meters. e maxi-
mum buer includes known average home ranges of
dice snakes, which are approximately .– hectares in
size (C  N , C at al. ,
N  M ). We compared the availa-
ble habitat types in the area with habitat types actually
occupied by dice snakes using ESRI ArcView . so-
ware. e same soware was combined with the digital
elevation model (DEM ) and land use (MKGP )
to analyze habitat use on a country-wide scale from the
second data set (see above).
Fig. 8. Average land use in a 10, 20, 500 and 100 meter buer
zone around capture sites of dice snakes (Natrix tessellata) in
Slovenia (n = 117) (see Fig. 6 for legend on habitat types).
Distribution and Habitat of Dice Snakes in Slovenia
with  precise locality records (Fig. ). is represents
 of all UTM squares in Slovenia. e majority of lo-
calities with dice snakes in Slovenia lie between  and
 m a.s.l. (Q and Qquartile). Based on precise data
only, dice snakes have been observed from sea level, at
the saltpans of Sečovlje and at Škocjanski zatok in coast-
al Slovenia (B et al. ), to the elevation of 
m a.s.l. at Ribnica, southern Slovenia.
Habitat Use
Regional scale: A total of  dice snakes were recorded at
the Sava Site and  dice snakes at the Kolpa Site. All of
the nds were made along the river banks or very close
to the water. Maximum distance from the nearest water
body was  m (Fig. ).
At Sava Site, available habitat types are relatively uni-
formly distributed with a slightly larger portion of ag-
ricultural land with herbaceous plants, grasslands and
shrubs (Fig. : transects). ere is only little agricultural
land with woody plants available as habitat. Compari-
son between habitat availability and habitat occupied by
dice snakes (Fig. : localities) show that the snakes were
detected more oen in water, grasslands and urban ar-
eas than expected from the habitat availability. On the
other hand, snakes were found less oen in forest and
agricultural land with herbaceous plants than expected.
Fig. 9. Site of several dice snakes (observed in le lower corner of image) near a cli approximately 50–100 m above a cool
mountain stream at Zaga, at 370 m a.s.l. in northwestern Slovenia. Presumably, dice snake seek that area for thermoregulatory
activities, possibly also oviposition and hibernation, as the cool temperatures of the shady canyon below, where they would
forage, are unlikely areas to provide suitable elevated temperatures. Shaded areas, in particular in the canyon, were digitally
elucidated to get a better view on the structure and height of the cli. Photo: K M.
A Ž, M K, M G  K M
At the Kolpa Site, forest occupies the largest portion
of available habitat types followed by grasslands, wa-
ter, urban areas and agricultural land with herbaceous
plants (Fig. : transects). e relatively large portion of
urban areas at the Kolpa Site results from transect lines
positioned mostly on roads along rivers and passing
through villages. Half of the dice snakes were captured
in the vicinity of water (Fig. : localities- m). In com-
parison to the habitat availability, dice snakes selected
water and shrub habitats more oen than forests and
grasslands (Fig. ).
National scale: Habitat use on a country-wide scale
shows that most dice snakes (.) were found in the
water or water was within a  m buer zone around
the capture sites (Fig. : SLO- m). On a larger scale
( m buer around capture sites), habitat types
were more balanced between forest (.), grassland
(.) and water (.) (Fig. : SLO- m). e ma-
jority (about ) of all precise localities (n = ) have
been recorded close to a water body (at a distance less
than  meters), and only few nds were located farther
away. Tthe farthest distance measured was  m in Laze
pri Predgradu (Fig. ).
Distribution of the Dice Snake in Slovenia
e current data of dice snake nds in Slovenia sug-
gest that the species is relatively uniformly distributed
throughout the lowlands of the country and that it oc-
curs in the vicinities of all major rivers, such as Drava,
Sava, Kolpa and Soča, except for Mura River in north-
eastern Slovenia, where it seems to be rare (Fig. ).
From the Mura River in NE Slovenia there have been
only two records of dice snakes in our data base, one
from a gravel pit at Zgornje Konjišče and the other from
Dokležovje. e local rarity and absence of dice snakes
Fig. 10. Dice snake, Natrix tessellata, from the cli in Fig. 9.
Photo: K M.
from the eastern part of Slovenia is in accordance with
a similar lack of data in neighboring areas of Austria,
Hungary, and Croatia (C et al. , P et al.
, J H et al. ), aside from the re-
cent recovery of dice snakes in Styria (K  M-
 ). It is not clear, however, whether this reects
a real lack of dice snakes due to extinction aer historic
degradation of once populated habitats in eastern Slo-
venia and related landscapes across the border. Alter-
natively dice snakes may have not found suitable habi-
tat in this region that could have promoted the evolu-
tion of a large population. However, we attribute this
to a lack of recent search eorts in NE Slovenia, because
K  M () report on the recoloniza-
tion of dice snakes from Graz to the Slovenian border
along the once heavily polluted Mura River aer a mas-
sive program was installed to rehabilitate that river sys-
tem. Subsequently, dice snakes have been detected since
the s at several locations on the Austrian side along
the section, where the Mura River constitutes the bor-
der between Austria and Slovenia (K  M
). It would require studying several factors to un-
derstand the reasons for the presence or absence of dice
snakes in this region of Slovenia. On the other hand, in
other parts of Slovenia dice snakes are better connected
with populations from neighboring countries, such as
dice snakes from the rivers Sotla and Kolpa adjacent to
Croatia (J H et al. ). Similarly, the dice
snake is distributed throughout the whole region along
both sides of the border with Italy (S  G
, see Fig. ).
Some regions in Slovenia are less suitable for the col-
onization of dice snake because of the lack of surface
water, such as higher parts in the Slovenian Alps and
high-karst region in the Dinaric Mountains. e species
is present in some northwestern parts of Slovenia, and
we expect it to be more frequent because cool streams in
the Julian Alps apparently do not prevent the coloniza-
tion of dice snakes (R & B , and Figs.
, ). Currently we lack data from the middle section of
the river Sava (between the towns Litija and Hrastnik)
and from some other larger rivers of Slovenia, e.g. the
middle section of Krka River, Ledava River, Reka River,
which is most likely due to lack of recent research eorts.
It is already known from other reports that dice snakes
occur also in brackish waters of lagoons, salt marshes,
river mouths, and sea water (G et al. ,
K , M ). e Sečovlje saltpans in
south-western Slovenia form a big network of ditches
with brackish water and suitable hunting places for dice
snakes. Another area with similar landscape features,
but with fresh water, is the Ljubljana moor, which has
historically spanned over a large area of central Slove-
nia. Nowadays, the wetland is a large network of ditches,
strongly aected by agriculture and surrounded by ur-
ban landscape and karstic Dinaric Mountains. Yet, it still
provides suitable habitat for dice snakes.
Distribution and Habitat of Dice Snakes in Slovenia
Habitat Use on a Regional Scale
In the lower section of the Sava River (Sava Site), we
found dice snakes almost exclusively on river banks cov-
ered with shrubs or woody plants. Although the resolu-
tion of the land use data was not as high as eld data ob-
tained directly from the snakes’ capture sites, the results
still show that agricultural land represented a substan-
tial part of the habitat used by dice snakes. However, this
does not necessary mean that dice snakes were living in
agricultural land, since we applied a circle buer around
the capture sites for analysis and agricultural land could
be included in the results due to its proximity to a river
habitat and not because it would have been actively se-
lected for by dice snakes. Agricultural elds and inten-
sively cultivated grasslands are common components of
the Sava plains today, oen leaving only a narrow belt of
trees or shrubby vegetation of approximately two meters
between river banks and agricultural land. Our results
here imply that although the landscape is intensively
cultivated, a narrow belt of suitable structure along the
water body can assure sucient habitat quality for dice
snakes. is is in accordance with similar results from
other parts of Europe (e.g. G et al. , M-
 , , C  N , C
et al. , , K  M , M et al.
, N  M , V et al. ).
e area along the Kolpa River (Kolpa Site) is mostly
covered with forests with little agricultural land because
of poor soil conditions. e area is also scarcely inhab-
ited, although there are several small villages with up to
 houses alongside the river. Our results point to the
importance of shore habitats that are anked by shrubby
vegetation but contain no or little forests. Similarly to
other studies (Z  K , C
et al. , M et al. ), dice snakes favored sites
covered with moderately dense vegetation. e banks of
the Kolpa River are densely overgrown with scrubs or
trees, except where remains of old dams of water mills
provide an opening of approximately  meters width.
Such old rocky dams are favorable basking spots for dice
snakes, where they also nd many shelters in the rock
crevices and under scrubs and trees. ese dams and the
occasional rocky outcrops apparently provide the dice
snakes with sucient access to solar radiation to main-
tain relevant physiological processes by thermoregula-
tion. It indicates that some human infrastructure pro-
vides suitable habitat for dice snakes or might in some
cases even increase habitat suitability, as has also been
suggested elsewhere (M , , C et
al. , K  M , M et al. ).
At least this seems to be the case in areas with high for-
est cover and with open structures that oer plenty of
shelter. Additionally, the Kolpa River contains substan-
tial segments with natural riverbed, exposed to river
erosion with changing depths and shoals that provide
a structurally diverse place for dice snake to forage and
nd shelter.
Habitat Use and Altitudinal Distribution
on a National Scale
In Slovenia, the dice snake occurs in the vicinities of
all lowland water bodies with a large supply of sh. It
prefers relatively open shores that are overgrown with
grassy, shrubby or moderate tree vegetation. Some dice
snake nds were also associated with urban areas. e
smallest portion of habitat types used by dice snakes
pertained to agricultural elds, suggesting that dice
snakes prefer an uncultivated landscape.
In Slovenia, the dice snake usually occurs below 
m a.s.l., whereas the average elevation of Slovenia is 
m a.s.l. (range in Slovenia,  to  m a.s.l.). Com-
pared to other countries, the low altitudes occupied by
dice snakes in Slovenia are surprising, since this species
occurs up to ~ m a.s.l. in the Swiss Alps (M
, G et al. ), close to  m a.s.l. in
Austria (C  T ), and at least up to
 m a.s.l. in northern Italy (S  G ),
although the latter record is supposed to be an erratic,
single stray nd. But indications of once existing popu-
lations have been found in the same area up to approxi-
mately  m (B et al. ). Dice snakes can
occur up to  m a.s.l. in southern countries (G
et al. ) and even up to  m a.s.l. in central Asia
(B et al. ). At present it is not clear whether
the absence of dice snakes from higher regions in Slo-
venia reects true absence or insucient eld work in
these areas. We hope that future studies will shed more
light on the distribution and ecology of dice snake in
We thank all who contributed data to the Centre for Car-
tography of Fauna and Flora and/or to the Societas Herpe-
tologica Slovenica and made preparation of this work possi-
ble. Special thanks to A. L from CKFF for preparation
of maps included in this article. Field work in study area Sava
Site was conducted as a part of a project titled “Inventarisa-
tion of Fauna and Flora and Habitat Type Mapping in the Area
of Planned Power Plants Brežice and Mokrice” funded by Hi-
droelektrarne na Spodnji Savi, d.o.o. Field work in study area
Kolpa Site contributed to a M.S. thesis by the rst author at
the Department for Biology, Biotechnical Faculty, University
of Ljubljana, Slovenia.
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, SI- Ljubljana, Slovenia, and Biotechnical Faculty, University of Ljubljana, Večna pot , SI- Ljubljana, Slovenia;
e-mail:; M G, Center for Cartography of Fauna and Flora, Antoličičeva , SI-
Miklavž na Dravskem polju, Slovenia; K M, Siebeneichenstrassse ,  Merenschwand, Switzerland.
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Z, P.  W. K (): Herpetological inventory
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... Halastavak esetében a kockás sikló gyakran zsákmányol az ott nevelt, sok esetben idegenhonos halak juvenilis egyedeit (Acipinar et al. 2006), vagy a tavakban élő kétéltűek, elsősorban békák ebihalait és fiatal példányait, mint az Jordániában is megfigyelték (Amr & Disi 1998) (Függelék 1. táblázat). Az időszakos víztestek esetében megnő a táplálékban a szárazföldi fajok szerepe a hal és kétéltű fogyasztás mellett (Amr & Disi 1998, 2011, Bakiev et al. 2011, Göçmen et al. 2011, Luiselli et al. 2007, Žagar et al. 2011) (Függelék 1. táblázat). ...
... A magashegységekben (> 1500 m) a faj specializálódhat a kétéltűek egyedeinek fogyasztására (Cafuta & Krofel 2007, Frotzler et al. 2011, Tuniyev et al. 2011, Žagar et al. 2011, valamint száraz klímájú élőhelyeken, ahol a faj időszakos víztestek, halastavak mellett él, ahol nagyon limitált a táplálékként számba vehető halfajok száma , Göçmen et al. 2011, Gruschwitz et al. 1999, Laňka 1978, Shehab et al. 2011. A halivadék nevelő tavak ezeken a területen a faj számára különösen fontosak, refugium területként működhetnek, mert az ember által átalakított környezetben ezek a mesterséges élőhelyek biztosítják a térségben a faj megmaradását (Acipinar et al. 2006;Göçmen et al. 2011). ...
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Doktori munkám két fő célkitűzése (i) a kockás sikló, a vízisikló és potenciális táplálékszervezeteik tér- és időbeli dinamikájának megismerése a Duna három mellékvízfolyáson, az Ipolyon, a Sződrákos-patakon és az Ilka-patakon, azok torkolati és a torkolatok körüli dunai szakaszokon, (ii) valamint hazánk öt régiójában, a Balaton, a Dráva, a Duna, a Koppány és a Tisza-tó térségében gyűjtött egyedek táplálék vizsgálatának összehasonlítása a szakirodalmi adatokkal. A kutatásaim során a következő kérdésekre kívántam válaszokat adni. 1. Hogyan alkalmazkodik a kockás sikló és a vízisikló az eltérő vízjárások hatására megváltozó táplálék készlethez és ezzel párhuzamosan hogyan változik az élőhely preferenciájuk a három folyó-mellékfolyó rendszerben. 2. Milyen fajokat fogyaszt a kockás sikló és a vízisikló hazánk öt különböző területén és az itt gyűjtött adatok milyen összefüggéseket mutatnak a két Natrix-faj teljes elterjedési területéről származó adatokkal. / The two aims of my doctoral thesis are (i) to understand the temporal and the spatial dynamics of the dice snake, the grass snake and their potential prey items in three tributaries of River Danube, in River Ipoly, in Sződrákos and Ilka stream and the estuaries section in River Danube and (ii) to compare the prey composition of sampled individuals at five areas of Hungary to the data of specialist literature. My study is aimed to give answers to the following questions: 1. How the dice snake and the grass snake adapt to the different prey composition parallel with the habitat preferences in different water level fluctuation in the three river-tributary systems. 2. Which species the dice snake and the grass snake eat in the five different areas of Hungary, and what relationships are shown between the sampled data and the data from the whole distribution area of both Natrix species.
... In fishponds, the main prey species of the dice snake were juvenile fish from aquaculture and allochthonous fish species (Acipinar et al. 2006) with occasional predation on amphibians (tadpoles and froglets) such as in Jordanian fish ponds (Amr and Disi 1998) (Additional file 1). With decreasing waterbody size, the feeding spectrum of the dice snake considerably changes to include terrestrial species besides fish and amphibians common in the given area Disi 1998, 2011;Bakiev et al. 2011;Göçmen et al. 2011;Luiselli et al. 2007;Žagar et al. 2011) (Additional file 1). Populations in high mountains (over 1,000 m a.s.l.) may specialise on eating larval and adult amphibians (Cafuta and Krofel 2007;Frotzler et al. 2011;Tuniyev et al. 2011;Žagar et al. 2011) as predominant food. ...
... With decreasing waterbody size, the feeding spectrum of the dice snake considerably changes to include terrestrial species besides fish and amphibians common in the given area Disi 1998, 2011;Bakiev et al. 2011;Göçmen et al. 2011;Luiselli et al. 2007;Žagar et al. 2011) (Additional file 1). Populations in high mountains (over 1,000 m a.s.l.) may specialise on eating larval and adult amphibians (Cafuta and Krofel 2007;Frotzler et al. 2011;Tuniyev et al. 2011;Žagar et al. 2011) as predominant food. It can also be considerable in arid regions, where the dice snake often lives along temporary water bodies or fish ponds, where only a limited number of fish species are present Göçmen et al. 2011;Laňka 1978;Gruschwitz et al. 1999;Shehab et al. 2011). ...
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Background: A global overview on the diet of the dice snake (Natrix tessellata) from a geographical perspective: foraging in atypical habitats and feeding spectrum widening helps colonisation and survival under suboptimal conditions for a piscivorous snake Abstract Background: The dice snake (Natrix tessellata Laurenti, 1768) is generally considered to be a fully or partially piscivorous freshwater snake species. The aim of the study was to make the first global overview on the taxonomy and geographical distribution of the species based on own observations, available databases and the special literature. Results: Besides freshwaters, N. tessellata turned out to hunt also in marine and terrestrial habitats predating on at least 29 and 15 species, respectively. On the basis of our data and the literature altogether, 113 prey taxa, mostly fish, were listed but 20% of them were invertebrates, amphibians, reptiles and mammals. The importance of non-fish species in the diet was especially pronounced in deserts, high mountains and in dry Mediterranean areas. In spite of the wide feeding spectrum, only fish and amphibians were found to be predominant food items over the whole species' range. Fish dominated the catch of the dice snake in most quantitative studies, except one survey in Turkey, where the ratio of non-fish prey items was over 50%. Conclusions: The global analysis of the diet of the dice snake revealed a feeding spectrum characteristically changing over the broad distribution area including non-fish prey as well as taxa from marine and terrestrial habitats. The analysis of the feeding spectrum separated four large geographical units with further distinctions in Central and Eastern Europe. Such diversity helps explain why this species was able to colonise a large and diverse Eurasian range.
... The main factor for high density of piscivorous snakes is the abundance of their prey (Chim and Diong, 2013). Numerous studies have shown that certain infrastructural objects are suitable for dice snakes as hiding places; in some instances, they even improved the suitability of habitats Kammel and Mebert, 2011;Žagar et al., 2011). On the other hand, in close proximity to human settlements, potential bird predators were not observed, while outside the areas under anthropogenic pressure numerous herons were encountered (G.Š., personal observation). ...
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Despite their comparative richness and accessibility in the Republic of Srpska and in Bosnia and Herzegovina in general, population studies of reptiles have not been performed in Srpska until recently. For example, one of the most common snake species in this area is the dice snake; nevertheless, previous studies have only reported its distribution. The aim of the present study was to analyze characteristics of the dice snake population along the Vrbanja River. Animals were processed during 2011 throughout their activity period. In total, 199 individuals of all ages were collected. We observed substantial differences in numbers of animals captured in different habitat types classified according to the level of anthropogenic influence. Unexpectedly, the largest number of snakes was captured in the zone with the highest anthropogenic influence, while the smallest number was observed in the zone with no anthropogenic pressures. The above is probably connected with the observed greater number of their most common prey, as well as the absence of raptors in areas with human impact. In the surveyed area, dice snakes feed predominantly on cyprinid fishes, and their reproductive traits are in accord with literature data.
... It is also supported by an abundance peak of Apodemus sylvaticus (with a maximum of 15%) and the slight increase in the abundance of Clethrionomys (to around 6%). The abundance peak of Natrix tessellata within this unit suggests a semi-closed environment with an open water surface in the close proximity of the site (Amr et al., 2011;Mebert et al., 2011;Zagar et al., 2011). The decrease in the abundance of Bufotes viridis compared to the previous unit might be related to the fact that these animals avoided the closest proximity of the nearby waterbody (Böhme et al., 2006). ...
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The Somssich Hill 2 site (Villány Mts., South Hungary) yielded one of the richest late Early Pleistocene vertebrate assemblages within the Carpathian Basin. The present paper provides a summary of all former and new taxonomical results, as well as biostratigraphical and palaeoecological conclusions, which is completed with previously unpublished sedimentological and taphonomical observations on the locality. The bulk of the fauna can be referred to the Mimomys savini–Mimomys pusillus Biozone in the Biharian (MQ1), whereas a few specimens suggest an older age, namely the Mimomys pliocaenicus Biozone in the late Villanyian (MN17). The bones were affected by only a short-distance aquatic transport, thus they represent a parautochtonous and relatively unaltered assemblage. Consequently, the material was considered here as a reliable base for reconstructing the direct palaeoenvironment of the cavity. The entire section was divided here to five different palaeoecological units based on the small vertebrate fauna.
... Although the vast majority of N. tessellata populations rely on fresh water bodies, few do occur in saline environments along the coasts of the Adriatic Sea [28,[32][33][34][35], the Ionian and Aegean Seas [36], the Black Sea ( [37][38][39][40], this study) and the Caspian Sea [41,42]. In most of these cases, N. tessellata occurs in brackish waters of lagoons, salt marshes and river mouths. ...
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The widespread relationship between salt excreting structures (e.g., salt glands) and marine life strongly suggests that the ability to regulate salt balance has been crucial during the transition to marine life in tetrapods. Elevated natremia (plasma sodium) recorded in several marine snakes species suggests that the development of a tolerance toward hypernatremia, in addition to salt gland development, has been a critical feature in the evolution of marine snakes. However, data from intermediate stage (species lacking salt glands but occasionally using salty environments) are lacking to draw a comprehensive picture of the evolution of an euryhaline physiology in these organisms. In this study, we assessed natremia of free-ranging Dice snakes (Natrix tessellata, a predominantly fresh water natricine lacking salt glands) from a coastal population in Bulgaria. Our results show that coastal N. tessellata can display hypernatremia (up to 195.5 mmol.l-1) without any apparent effect on several physiological and behavioural traits (e.g., hematocrit, body condition, foraging). More generally, a review of natremia in species situated along a continuum of habitat use between fresh- and seawater shows that snake species display a concomitant tolerance toward hypernatremia, even in species lacking salt glands. Collectively, these data suggest that a physiological tolerance toward hypernatremia has been critical during the evolution of an euryhaline physiology, and may well have preceded the evolution of salt glands.
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Using Species Distribution Modeling (SDMs) and Least Cost Path Analysis in order to examine the current and future distribution of the Cyprus grass snake and the effect of climate change on it.
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Formerly, the Early Pleistocene vertebrate material collected independently from 15 diff erent sampling sites of Beremend Crystal Cave were merged together and treated as a whole, under the name of Beremend 16. However, the thorough analysis of the fauna of each separate sampling site revealed considerable taxonomic, palaeoecological and stratigraphic diff erences, which render the aforementioned unifi cation unjustifi ed. Diverse and sparse assemblages were recognized based on the fossil richness and taxonomic composition of the samples. Some of the assemblages contain only bats, whereas others consist of further small mammals besides the bats as well as herpetofaunal elements. Th e compositional dissimilarities suggest taphonomical or age diff erences comparing the sites. Based on our environmental reconstruction, a water body varying in size was always present in the vicinity of the cave during the studied time period, which was surrounded by an open or a more closed vegetation depending on the slight climatic changes. Our stratigraphic analysis showed that most of the sites can be dated between 1.5 and 1.2 Ma. In the case of two sites, it was possible to make a more precise age estimation (1.2 Ma) based on the appearance of the white-toothed shrew, Crocidura obtusa. With 4 fi gures and 4 tables.
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Th e fossil material of Esztramos 6 palaeovertebrate locality has been revised in this study with special regard to its herpetofauna. Result of this study has shown the presence of the species Latonia gigantea and the fauna list of the locality has been expanded by amphibian, reptil-ian, and mammalian taxa. Considering diff erences of the mammalian fauna the Esztramos 6 lower and upper sites are probably not coeval, however their palaeoenvironment shows similarities. With 23 fi gures and 1 table.
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Natrix tessellata یک گونه وابسته به آب است که زندگی بسیاری از آنها در نزدیکی نهرهایی که غنی از ماهی هستند کشیده شده است. در این مطالعه که از 15 فروردین تا 15 آبان 1391 روی جمعیتهای شهرستان ساری در استان مازندران انجام شد، تعداد 57 نمونه مار نر از چهار ایستگاه تالاب پرورش ماهی آبندانکش، پارك جنگلی زارع، رودخانه تجن و شالیزارهای اطراف ساری بهمنظور مطالعات تولیدمثلی، رفتارشناسی، بررسی صفات ریختی متریک و مریستیک در گشتهای روزانه و با دست جمعآوری شدند. نمونهها از ارتفاع 30 متری از سطح دریا در شالیزارهای برنج تا ارتفاع 700 متری در منطقه پارك جنگلی زارع مشاهده شدند. نتایج تحقیق حاضر نشان داد که طول بدن آنها بین 34 تا 68 سانتیمتر، طول دم آنها بین 11 تا 16 سانتیمتر و در صفات مریستیک تعداد فلسهای جلو چشمی 2 یا 3 عدد، 3 یا 4 فلس عقب چشمی، لب بالا دارای 8 و لب پایین 9 یا 10 فلس، فلسهای شکمی 169 تا 183 عدد، زیر دمی 60 تا 78 عدد و فلسهای پشتی در تمام نمونهها 19 عدد میباشد. زمان فعالیت این گونه در منطقه مورد مطالعه در فصل بهار از ساعت 9 صبح تا 16 عصر میباشد اما در فصل تابستان از ساعت 8 تا 13 و در بعد از ظهر از ساعت 17 تا 20 میباشد. همچنین در این تحقیق فعالیت شبانهای از این مار مشاهده نشد. با شروع اسپرماتوژنز در اواسط خرداد، تعداد اسپرمها رفته رفته افزایش یافته و در اواسط مرداد و شهریور به حداکثر تعداد میرسد.
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Due to Croatia’s geographical position, which is situated at the crossroads of several biogeographical regions, in its small area we find an exceptional wealth of flora and fauna that complements the biological diversity of Europe. Thus, the fauna of amphibians and reptiles (herpetofauna) in Croatia is of great importance, and stands out particularly in terms of endemic species, whether it is the regional endemics such as the Italian agile frogs or the Croatian endemics like the Lastovo wall lizard. Many species of amphibians and reptiles lived on Earth for millions of years virtually unchanged (for instance, crocodiles and turtles and tortoises), however, due to human activities in the modern era such animals have been exposed to the threat of extinction. A significant decrease in their numbers, sometimes even resulting in the extinction of amphibians and reptiles is attributed to various causes, such as loss and fragmentation of habitat, pollution of soil, water and air, the onset of disease, over-exploitation, i.e. collecting and introducing invasive alien species. According to the International Union for Conservation of Nature (IUCN), amphibians were highlighted as the most threatened group of vertebrates. Since they react quickly to very small changes in the environment, they are considered good environmental indicators, namely a change in their living communities is a sign that certain negative impacts exist in our environment.
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With an increasing industrialization of the region and poor sanitation in the 1960s and 1970s the river Mur was excessively polluted and de facto biologically dead. Numerous waterbound species like the dice snake were largely extinct in the investigation area and survived only in tributaries and water bodies close to the Mur. Through a massive effort to rehabilitate the ecosystem "Mur" since 1985, its water quality had improved significantly. Since then, both the dice snake as well as its potential prey, various fish species, re-populated the area. In addition, several projects of nature-orientated hydraulic engineering were implemented. The dice snake still continues to expand in this area. An exception to this development can be observed at water reservoirs of hydroelectric power plants. While downstream of the weir plants, there are often dense populations of dice snakes, this species is missing in the water reservoir area immediately upstream of the respective weirs possibly due to the paucity of the habitat, inlcuding little structured banks, high sedimentation of fine sand and a low stock of fish. Zusammenfassung. Durch zunehmende Industrialisierung der Region und mangelhafte Abwasserentsorgung zeigte sich das Flusssystem der Mur in den 1960er-und 1970er-Jahren als übermässig verschmutzt und de facto biologisch tot. Zahlreiche Fischarten sowie die Würfelnatter waren damals im grössten Teil des Untersuchungsgebietes ausge-storben; ihr Vorkommen beschränkte sich weitgehend auf Refugialräume an Nebengewässern. Durch massive Be-mühungen zur Restauration des Ökosystems "Mur" seit 1985 konnte die Wasserqualität erheblich verbessert werden. Seitdem hat die Würfelnatter gemeinsam mit ihren Beutefischarten den Lebensraum Mur wieder besiedelt. Zudem wurden zahlreiche Projekte im Sinne der Zielvorstellungen des naturnahen Wasserbaues umgesetzt. Die Würfelnat-ter breitet sich auch aktuell noch weiter aus. Eine Ausnahme von dieser Entwicklung stellen Stauräume der Wasser-kraftwerke dar. Während sich unterhalb der jeweiligen Staustufen häufig Würfelnatterbestände mit hohen Abundan-zen befinden, fehlt die Art in den unmittelbaren Stauhaltungsbereichen durch Mangel an Lebensraum, einschliess-lich Strukturarmut, hohe Feinsedimentation und geringen Fischbestand.
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The dice snake, Natrix tessellata, is classified as a highly endangered species in the Czech Republic. The Prague Zoo, supervised by the Agency for Nature Conservation and Landscape Protection (AOPK), promoted the study of its isolated population of dice snakes along the Vltava River in order to contribute to the rehabilitation of the nationally endangered species. The field work spanned from 2005–2008 and included numerous methods, of which the results related to ecology and ethology are reported herewith. Related field work involved a capture/recapture method, and acquisiton of reproductive and ecdysis data, measuring cloacal temperatures and radiotelemetry of five individuals. Results summarize, that dice snakes hibernate up to 238 days to mid April, migrate several hundred me-ters in a few days to a summer habitat, and return to their hibernacula as early as August and September, which are located up on the slope of a hill in the zoo. The summer habitat is a 750 m long littoral zone, where they begin hunting for fish as late as mid May. Oviposition happened within the first two weeks of July after which female snakes were left with as little as 40 days to acquire enough food and energy for the following hibernation. Currently, this popula-tion appears to be very healthy, as the density of individuals is approximately 180 individuals per hectare with a total population size between 500 and 800 snakes. In conclusion, the dice snake population of the Prague Zoo is one of the most important habitats of this snake species in the Czech Republic.
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Based on a two-year monitoring, we analysed the distribution of dice snake populations in the Canton of Ticino (Switzerland). Imperfect detection was taken into account in order to avoid underestimation of the distrubtion range and hence overestimating the species threat status: we therefore used a model based on a mark-recapturelike approach to estimate detection probability, which was 61.2% (± 6.8%; standard error), and site occupancy, which was 78.0% (± 7.9%). Detection probability depended on habitat characteristics (tree cover and naturalness of the streams and lake shores) while occupancy was best predicted by the number of previous dice snake records at a site. We observed local decline or extinction of some small populations located on secondary streams, apparently because of habitat deterioration. However, populations located on lakes (Lugano, Maggiore) and main rivers (Ticino, Brenno, Maggia, Vedeggio and Tresa) showed no signs of decline and rather high densities. Therefore, the status of Natrix tessellata in Ticino should be considered as stable. The endangered status reported by the Swiss Red List for these species is adequate because of the small area occupied at national level (IUCN criteria B2a, B2b (iii, iv)) and vulnerability of freshwater ecosystems. A specific action plan in favour of the conservation of dice snakes populations in Ticino, Switzerland, will now be based on the collected data.
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Nine adult female dice snakes, Natrix tessellata, from three different sites were tracked during an entire season using radiotelemetry. The study sites represent the variation of habitats occupied by dice snakes in the can-ton Ticino (southern Switzerland); a relatively intact and protected river delta (Bolle di Magadino), a semi-natural stream (Arbedo) and a lake ecosystem with strong human influence (Riva San Vitale). The radio-tracked dice snakes were found only in the immediate surroundings of the open water surface with 97% of the locations occurring at less than 20 m distance from the water. The most frequent structures selected by the monitored animals for sheltering, thermoregulation and oviposition were artificial rocky embankments (rip-raps) and other similar retaining works (i.e. stone walls) covered with light vegetation and well exposed to the sun. The snakes avoided forest habitat with dense monotonous vegetation or artificial stream reaches with concrete banks and a low ecomorphological value (lack of microstructure). The rather long monitoring period at the Bolle di Magadino site allowed us to identify rel-evant seasonal changes in their habitat use. During the fall, the snakes moved from the summer habitat towards the hibernation sites at the edge of the flood plain. In spring, they used the same migration route to return to their sum-mer habitat.
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The valley of the river Nahe is known to sustain the largest population of dice snakes in Germany. The population is further dispersed into half a dozen subpopulations along the approximately 15 km long Nahe River. A frequented road splits most of the habitat, leading to numerous traffic casualties of snakes every year. Because of its isolation to other populations of dice snakes and its relatively large population size, an active protection of the Nahe population can be considered to be fundamental for the conservation of this nationally endangered species. In 2007, a radiotelemetry study was carried out at one of the subpopulations to analyze the migration behavior of the dice snakes to provide ecological data for future conservation strategies. Five adult female dice snakes were tagged with subcutaneous implanted transmitters to construct movement profiles. The calculated homerange varied depending on the analysis method from 0.22 ha (95% Kernel) to 0.27 ha (MCP). The tagged snakes were mainly active at air tem-peratures between 20–26 °C and partially cloudy sky. Activity in the water or near the shore was detected every 4–5 days, mostly between 15–18 pm. The daily movement of the tagged snakes was in 80% less than 30 m. Zusammenfassung. Die Kernlebensraum der grössten deutschen Würfelnatterpopulation am Fluss Nahe, Rhein-land-Pfalz, Deutschland, wird fast entlang des gesamten Flusslaufs von einer teils stark frequentierten Strasse zer-schnitten. Hier werden jedes Jahr Dutzende Würfelnattern überfahren. Dies ist eine ernstzunehmende Gefahr für die isolierte Population, die sich entlang des ca. 15 km langen Flussabschnitts auf etwa ein halbes Dutzend Subpopu-lationen verteilt. Im Jahr 2007 wurde an einem dieser Subpopulationen eine radiotelemetrische Studie durchgeführt, um durch genauere Bewegungskenntnisse effektivere Schutzmassnahmen durchführen zu können. Hierfür wurden fünf adulte Würfelnatterweibchen mit subcutan implantierten Sendern versehen und deren Bewegungsprofile er-stellt. Der ermittelte Aktionsraum beträgt je nach Auswertungsmethode zwischen ca. 0.22 ha (95% Kernel) und 0.27 ha (MCP). Die Hauptaktivität der Senderschlangen war bei 20–26 °C Lufttemperatur und wechselhafter Bewölkung. Aktivität im Wasser oder in Ufernähe war etwa alle 4–5 Tage zu verzeichnen, in über 50% der Fälle dann zwischen 15 und 18 Uhr nachmittags. Die täglich zurückgelegte Strecke der Senderschlangen war in 80% der Fälle unter 30 m.
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Le serpent Natricidae Natrix tessellata (Lauren-ti, 1768) est une espèce aquatique à vaste répar-tition occupant trois continents, l'Europe, l'Afrique et l'Asie. Elle se rencontre en effet depuis la Suisse et l'Allemagne en Europe cen-trale jusqu'en Égypte sur le continent africain et à l'est jusqu'à la Province du Xinjiang en Chine. L'espèce occupe une diversité d'habitats, depuis les oasis des déserts de Jordanie, de Syrie ou d'Iran jusqu'en pleine mer en Méditerranée ou en Mer Noire, à des altitudes inférieures au niveau de la mer sur les berges de la Mer Cas-pienne jusqu'au-dessus de 2 800 m dans certai-nes vallées, en passant par les steppes d'Asie centrale ou encore le coeur de certaines grandes cités modernes comme Prague ou Bucarest. Malgré cela, nos connaissances sur cette espèce, au régime principalement piscivore, restaient éparses et marginales. Ce volume, publié dans la série Mertensiella associée à la magnifique revue allemande Salamandra (tous deux édités par la DHGT, Société allemande d'Herpétologie), dresse un état actualisé des connaissances à présent conséquentes sur l'espèce, aussi bien sa biologie, sa répartition et son écologie, que des problèmes liés à sa conservation. Il s'agit là d'un ouvrage collectif qui regroupe 57 arti-cles et un DVD impliquant un total de 122 auteurs et co-auteurs issus de plus de 22 pays. Dans l'introduction, l'éditeur de ce volume, l'herpétologue suisse Konrad Mebert, expose la laborieuse genèse de son exploit éditorial totalisant plus de 4 000 heures de travail réparties sur quatre années. Il propose à présent un produit final d'excellente qualité. Ce dernier regroupe des articles presque tous en anglais émanant des quatre coins de la vaste aire de répartition du serpent, nous donnant ainsi une vision de la plasticité d'un taxon (habitat, éco-logie, comportement, morphologie etc.) qui reste malgré tout une espèce à part entière. En dépit de quelques variations locales et régionales, une couleuvre tessellée d'Italie n'est guère
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In the years 1977-2001, the fauna of and ecological conditions in 55 cavities – caves and artificial tunnels – in northern and central Slovenia were systematically investigated. Zoogeographically, this is the meeting point of the Alpine, Pannonian and Dinaric biome. This article lists 321 terrestrial genera, 456 species and 100 subspecies belonging to 183 families, that had been recorded by 2005 in cavities of this region in the course of our own investigations, and that have been cited in the references. This taxonomical review serves as a foundation for understanding ecological and other treatise on the terrestrial fauna in the hypogean habitats of northern and central Slovenia, those that have been published ones, as well as those in preparation. The overview of the systematically investigated cavities, and the review of the methods and techniques used has been added to provide general information about the morphology of these caves, and the ecological research within them. V letih 1977-2001 smo sistematsko raziskovali kopensko favno in ekološke razmere v 55 votlinah – jamah in izkopanih rovih – severne in osrednje Slovenije. Zoogeografsko je to ozemlje na stičišču alpskega, panonskega in deloma dinarskega bioma. V članku je pregled 321 rodov, 456 vrst in 100 podvrst živali iz 183 družin, ki so bile do leta 2005 najdene v votlinah tega območja med lastnimi raziskavami ter po podatkih iz citirane literature. Taksonomski pregled je osnova in opora za razumevanje ekoloških ter drugih razprav o kopenski favni v podzemeljskih habitatih severne in osrednje Slovenije, ki so že objavljene in ki jih pripravljamo. V nadaljevanju so predstavljene votline, v katerih so potekale sistematske ekološke raziskave, ter naštete uporabljene metode in tehnike, s čimer je omogočen vpogled v morfologijo ekološko raziskanih votlin ter metode raziskovanja