Relocation of the European pond turtle Emys orbicularis clutches did not influence the hatching rate

Abstract

Six clutches of the European pond turtle Emys orbicularis deposited on hazardous areas in central Poland were relocated in 1999 and 2000, to the nearest egg laying areas (used by other females in the same season). The eggs were moved up to 12h after laying, and were not rotated. There were no statistical significant differences in the proportion of hatched turtles from clutches relocated vs. no relocated ( F = 0,76 , df = 1, P = 0,39). However, the effectiveness of such methods for protection of the turtle populations is small, and if the larger proportion of clutches in any population were be relocated, it could have a negative effect on the turtle population.

Full text

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Acta Biol. Univ. Daugavp. 8 (1) 2008
ISSN 1407 - 8953
INT RODUCTION
The European pond turtle (Emys orbicularis) is
an endangered species in many parts of its
territorial range, mostly because of changes in
its natural habitats (Fritz 2003). Presently, a
considerable number of turt le protection
programmes are being undertaken (Seigel & Dodd
2000). Protection of turtles natural habitats is -
without reservations - a good method for
protection of the animals (cf. Maciantowicz &
Najbar 2004), but other methods (reintroduction,
headstarting etc.) are controversial (cf. Heppell
et al. 1996, Seigel & Dodd 2000, Mitrus 2005).
Under some protection programmes, activities
RELOCATION OF THE EUROPEAN POND TURTLE EMYS
ORB I CULA R I S CLUTC HE S DID NO T INFLU ENC E THE
HATCHING RATE
Sławomir Mitrus
Mitrus S. 2008. Relocation of the European pond turtle Emys orbicularis clutches did not
influence the hatching rate. Acta Biol. Univ. Daugavp., 8(1): 63 - 66.
Six clutches of the European pond turtle Emys orbicularis deposited on hazardous areas in
central Poland were relocated in 1999 and 2000, to the nearest egg laying areas (used by other
females in the same season). The eggs were moved up to 12h after laying, and were not
rotated. There were no statistical significant differences in the proportion of hatched turtles
from clutches relocated vs. no relocated (F = 0,76 , df = 1, P = 0,39). However, the effectiveness
of such methods for protection of the turtle populations is small, and if the larger proportion
of clutches in any population were be relocated, it could have a negative effect on the turtle
population.
Key words: Emys orbicularis, protection, clutch size, predation.
Sławomir Mitrus. Jagiellonian University, Institute of Environmental Sciences, Department
of Ecosystem Studies, Gronostajowa 7, 30-387 Cracow, Poland; Opole University, Department
of Biosystematics, Laboratory of Vertebrate Zoology, Oleska 22, 45-052 Opole, Poland, e-
mail: emyspl@yahoo.com (present address)
aimed at nest protection or relocations are being
undertaken (Maylan & Ehrenfeld 2000).
In central Poland clutches of the European pond
turtle Emys orbicularis are typically deposited
on xerothermic slopes and barrens. However,
some of them are deposited in agricultural fields,
on roads across fields, or other hazardous
locations (Mitrus 2006a, b). In such situations
they could be destroyed by agricultural vehicles.
During an active protection programme in central
Poland such clutches were relocated to other
areas (Mitrus 2005). The objective of this study
was to compare the hatching rate for non-
manipulated and relocated clutches.

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Mitru s S.
MATERIALS AND METHODS
The fieldwork was conducted in the Zwoleńka
River Valey from 1997 to 2001 (Borowiec Nature
Reserve (BNR) and the Barycz village region
(central Poland, in the Radom District); the
location was presented in Mitrus & Zemanek
2004, with more details about BNR in Zemanek
1992). Each year during the egg laying period
(mid-May to mid-June), I observed the female
turtles on their way to their nesting sites and
during nesting using binoculars. When possible,
I counted the eggs during the egg laying process.
I marked the nests by placing pegs at the corners
of a 50 cm square centred on the nest.
For the years 1998–2000, there were no statistical
differences between the BNR and Barycz village
region in the average number of eggs laid (t =
1,24, df = 22, P = 0,23), and the size of the females
that laid eggs (for the straight carapace length: t
= 1,16, df = 25, P = 0,26; Mitrus 2002). One adult
female marked in the BNR several years later was
caught in the Barycz region (cf. Mitrus and
Zemanek 2004). Thus, I analysed the data from
the two areas together.
Some clutches were deposited in agricultural
fields, on roads across fields, or other hazardous
locations (cf. Mitrus 2006a, b). Based on my
experience from studies of the turtle in the BNR
from 1990 to 1997, it is evident to me that they
would be destroyed by agricultural vehicles.
Thus, I relocated these clutches to safer places;
generally the nearest area used by other nesting
females in the same season.
In central Poland the turtle lays eggs in the
evening (Zemanek 1988, Mitrus & Zemanek
1998). Moving the eggs from hazardous locations,
was made on the following morning, up to 12
hours after laying. I opened a nest from the top.
Each located egg was numbered on the top,
placed in a container with moistened soil, and
moved to a new place. The eggs were not rotated,
because in the early part of incubation the embryo
attaches to the upper eggshell above the yolk
mass and could be distorted or die if the egg is
turned (cf. Ewert 1989). Then I started to make an
artificial breeding chamber, which for the
European pond turtle has been described as
“pear-shaped” (Zemanek 1988, Andreas & Paul
1998). Using a small spoon I made a breeding
chamber resembling such a shape, approximately
15 cm in depth, with a chamber width of 10 cm,
and a 5 cm hole(cf. sizes of the turtle breeding
chamber in: Zemanek 1988, Andreas & Paul 1998).
Afterwards, I placed the eggs into the artificial
chamber using the spoon, keeping the original
order of the eggs as they were laid (eggs found
in the bottom of the chamber were placed first in
the artificial chamber), and the original position
of the eggs (top-bottom). I then closed the hole
to the artificial chamber using the soil removed
during construction of the chamber.
I checked all the nests irregularly over the spring
for signs of predation. At the end of the summer
I checked them every 10 to 14 days for signs of
hatchling emergence (= moving from the nest
chamber to ground level). In winter I checked the
marked nests irregularly (depending on snow
cover), and in the following spring, every 10 to
14 days. If there were signs of hatchling
emergence (a hole in the chamber), I opened the
nest immediately, and counted the hatchlings
(dead and alive), eggs, and eggshells. I calculated
the hatching success separately for each nest;
the calculation was made in the same way for
moved and unmoved clutches (for details of the
calculation see: Mitrus 2005). I analysed the data
with STATISTICA for Windows version 5.5 (StatSoft,
Inc., 1999).
RESULTS
The mean clutch size of the turtle in the Zwoleńka
River Valley was 14.5 eggs (SD = 2.79, range 9–
23; data from four seasons, 47 clutches from 24
different females). Seven known clutches were
deposited on hazardous places: two of the 20 in
1999, four of the15 in 2000, and one of the 17 in
2001.Of the seven clutches that were relocated,
one of them (in 2000) was destroyed by man.
For years 1999 and 2000 there were no statistical
significant differences in the proportion of

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Relocation of clutches of the turtle Emys orbicularis...
hatched turtles from relocated clutches vs. not
relocated (F = 0,76 , df = 1, P = 0,39), but there
were differences between the two years (F = 8,45,
df = 1, P < 0,01).
DISCUSSION
The relocation of nests is used in protection
programmes (e.g. of marine turtles). However,
there are some essential problems concerning the
relocation of nests; namely that for many turtle
species (including the European pond turtle;
Pieau & Dorizzi 1981), the sex determination is
temperature dependent, and the temperature in
the artificial chamber would probably be different
as we do not know how to shape the artificial
breeding chamber, how to arrange the eggs, and
so forth (Meylan & Ehrenfeld 2000).
In an extremely small population, destroying nests
may became a serious problem to the very
survival of the population (Andreas 2000). But,
in central Poland only a small part of the nests is
deposited are located in hazardous locations (13
of 118 nests, Mitrus 2006a), and the predation
rate (including destroying nests from such
localities) is not high: during spring and summer
0.20 and during winter for nests containing
overwintering hatchlings 0.07 (details see: Mitrus
2005).
During the research I opened nests deposited in
hazardous locations up to 12 hours after of the
eggs were laid, and relocated to the nearest
nesting areas. The eggs were moved with the
moist soil were not rotated. Each of the factors
(in addition to probably others, e.g. depth of
artificial breeding chamber, temperature during
moving) could affect the hatching rate. In the
research, no statistical differences in the hatching
rate between relocated and non-relocated
clutches were found, although the analysed
probe was small. Other subjects (e.g. sex ratio in
nests) were not studied.
Results of the study show, that it is possible to
protect nests from hazardous locations by
relocating them to safer areas. However, if a larger
proportion of clutches in any population were
relocated it could have a negative effect on the
turtle population (Meylan & Ehrenfeld 2000,
Nordmoe et al. 2004), and protection of nests
without additional conservation efforts that
reduced adult mortality wi ll be probably
ineffective (cf. Heppell et al. 1996, Mitrus 2005).
What is more, for the relocation or protection of
endangered clutches, precise information about
their location is necessary, although gathering
such information is time-consuming and costly
(cf. Joyal et al. 2000). Thus, the method is not
particularly useful for the protection of the
European pond turtle population, although such
activities could draw peoples attention to the
problems of protection of the species.
ACKNO WLEDGEMENTS
Thanks to all my friends who helped in the field
during this study, especially to Dr. M. Zemanek
and Eng. A. Kotowicz. Data used in the study
were collected as part of a programme of active
protection of the European pond turtle, supported
by the Environment and Agriculture Department,
the Mazovian Voivodeship Office in Warsaw, the
EcoFund - Polish Debt for Environment Swap,
Global Environment Facility - GEF/SGP UNDP,
and the Kozienice Landscape Park. I also thank
R. Tertil and Ian Harman, both of Letterman
Tr ansl ators & In ter preter s who provided
linguistic corrections.
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Andreas B., Paul R. 1998. Clutch size and structure
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Received: 15.11.2008.
Accepted: 06.06.2008.