Long-lasting asynchronous emergence of loggerhead sea turtle Caretta caretta in one of the northernmost nests on the Adriatic coast

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22 Herpetological Bullen 169 (2024)
The loggerhead sea turtle Carea carea (L., 1758) is an
endangered species distributed throughout subtropical
and temperate regions. Due to menaces aecng its
conservaon status in the Mediterranean basin (Wallace
et al., 2010), several conservaon and management
programmes have been established to protect and monitor
its nesng sites (Casale, 2015).
In 2023, there were known to be 26 loggerhead sea turtle
nests along the western coast of the Adriac Sea. Most of
these occurred in the Puglia region, except for two, which
were located in the province of Teramo in Abruzzo and in the
province of Ravenna in Emilia Romagna. The last two cases
represent two of the most northern successfully hatched
nests along the eastern Italian coast, together with Pesaro,
Marche in 2019 (Mancino et al., 2022) and Jesolo, Veneto in
2021, which to date is the northernmost locaon recorded
(Sénégas et al., 2009) (Fig. 1). Here I describe observaons
on a nest at the beach of the Borsacchio Nature Reserve in
Teramo (Fig. 1). This is not the rst occasion in which a sea
turtle nest has been reported in the Abruzzo region, but
it is the rst me it has been possible to protect the nest
site, thanks to the commitment of local associaons. The
importance of this case is not only linked to its geographical
posion but to the dynamics regarding hatching, which, in
addion to occurring at the original site, represents a record
for the longest-lasng asynchronous emergence of hatchlings
from the nest.
On the aernoon of 18 July 2023, recent traces of a sea
turtle nest were found along the beach of the Borsacchio
Nature Reserve (Roseto degli Abruzzi, TE) at a distance of
approximately 24.5 m above the mean low-water mark.
Once the presence of the nest was veried, the site was
immediately secured by volunteers from the associaons
Centro Studi Cetacei and Guide della Riserva Borsacchio. To
protect the nest, seven days before the emergence of the
hatchlings, the volunteers installed a circular fence of 1 cm
mesh plasc net around it (4.4 m diameter and height of
0.50 m). With the same type of net they created a 1 m wide
corridor towards the sea, crossing the beach perpendicularly
nishing a few metres from the sea. The net encircling the
nest could be opened where it joined the corridor, to allow
access to the sea at mes when hatchlings were emerging
but was otherwise closed. Later, a second circular fence
was installed around the nest but with a greater diameter
(5.6 m) which allowed access to volunteers and experts but
otherwise oered addional protecon to the nest. The site
was monitored 24 hours a day by volunteers and at night
illuminated with low-impact red LED (RGB) lights with integral
solar panels. The emergence of each turtle was monitored
and assisted by volunteers from the associaons, unl
they had entered several metres into the sea. Periodically,
following the turtles’ immersion, beach secons adjacent to
the sea-entry corridor were checked in case the hatchlings
had been dragged back onto the beach. Electronic probe
thermometers (Arceli) were placed on the northern border
of the net surrounding the nest with the probes penetrang
the sand to a depth of 35 cm. An Aorlis electronic scale and a
Zhjan digital calliper were used to collect morphometric data.
The Herpetological Bulletin 169, 2024: 22–24
Long-lasng asynchronous emergence of loggerhead sea turtle
Carea carea in one of the northernmost nests on the Adriac
coast
ALESSANDRO PATERNA
OPHIS Museo Paleontologico e Centro Erpetologico, 64100 Teramo, Italy
Author e-mail: alessandro.paterna@hotmail.com
hps://doi.org/10.33256/hb169.2224
SHORT COMMUNICATION
Figure 1. The northern poron of the Adriac Sea. Red dots
correspond to the four most northern Carea carea nests recorded
to date and successfully hatched.

Herpetological Bullen 169 (2024) 23
Long-lasng asynchronous emergence of loggerhead sea turtle in one of the northernmost nests on the Adriac coast
Since the nest was located within a nature reserve, it was
free of bathing establishments in the nearby area, but was
sll frequented by residents and tourists. The area is almost
completely natural, with the excepon of a ruined building
on the beach a few metres from the water, and a cycle path
anked by a railway parallel to the beach, located about 100–
110 m from the sea. The beach consisted of ne white sand
that was clean for about twenty metres from the sea. The
closest sources of light polluon were located approximately
820 m north and 1,150 m south of the nest.
On the morning of 9 September, 53 days aer the
discovery of the nest, a depression formed in the centre of
the nest at 07:30 h, which was a symptom of the imminent
emergence of the hatchlings. The rst specimens began to
emerge twelve hours later, from 19:30 h to 22:00 h (Fig. 2),
when 20 turtles found their way to the sea within two and a
half hours. Two more specimens emerged during the night,
before dawn. On the evening of 11 September, another 24
specimens emerged and headed towards the sea from 19:30
h to 22:14 h. In the following nine days, other specimens
emerged individually or in small groups (max. 4) (Fig. 3).
The major acvity of the hatchlings was observed from
18:45 h to 04:00 h, during twilight and night, while no acvity
was recorded from 09:00 h to 18:45 h (Fig. 3). The longest
period of inacvity between emergences was 47 hours.
Times from emergence to immersion in the sea (distance
of about 24.5 m) varied from 20 to 45 minutes. The tracks
le by the hatchlings on the sand provided evidence of the
dispersal paern within the delimited area circumscribing
the nest. These were mainly orientated towards the south/
south-east quadrant of the area. A few individuals ‘inspected’
the western poron of the fence, but none moved into the
northern half, where the sand remained undisturbed.
On the morning of 23 September, 55 hours aer the
emergence of the last specimen, it was decided to disinter
the nest due to an expected storm and the bad weather. In
the egg chamber, which had a depth of 43 cm at the base,
there were empty eggs shells, 12 inferle eggs, three dead
hatchlings and two live hatchlings. Morphometric data of the
last two specimens were taken before they were released.
On average, they had a total length of 58 mm, carapace
length of 40 mm, and weighed 15 g. The nest had contained a
total of 84 eggs, from which a total of 70 hatchlings emerged,
giving a hatch success rate of 86%. During the whole period
of observaon, the weather was almost connuously
favourable. Strong winds never occurred and rain only fell
on two occasions, both during the night. The temperature
recorded by the electronic probes inserted into the subsoil
showed no signicant variaons during the days when the
nest was monitored, oscillang between 24.6 °C at night and
a maximum of 25.7 °C during the day. The lowest temperature
recorded was 24.2 °C during one of the two nights with rain.
Within the rst three days of the emergence period two
thirds of the hatchlings had le the nest, mostly in large groups,
while the remaining third were distributed throughout the
following days as single individuals or small groups consisng
of a few individuals (Fig. 3). The incubaon period of the
eggs is not certain due to the wide spread of emergences
from the nest but can at least be esmated roughly. It may
be assumed that the nest was found on the morning aer
egg laying, we know that that the rst hatchlings emerged
53 days later, that hatchlings are known to take from 2 to 7
days to reverse the folded posture assumed inside the egg,
to absorb the yolk sac, and to dig themselves out of the nest
(Godfrey & Mrosovsky, 1997; Miller et al., 2003). From this
we can esmate that at least some of turtles hatched within
about 46–51 days from egg laying. Most likely, the turtles did
not all hatch at the same me, as 12 days elapsed between
the rst and last emergences from the nest, meaning that
some of the hatchlings may have taken 14–19 days to
emerge, while the last two specimens may have spent 17–22
days inside the egg chamber aer hatching. As documented,
Figure 2. Carea carea hatchlings emerging from the nest site in
the Borsacchio Nature Reserve in the province of Teramo, Abruzzo
Figure 3. Date and me of day that hatchling Carea carea emerged
from a nest in the Borsacchio Nature Reserve in the province of
Teramo, Abruzzo. The bars represent me of hatchlings’ acvity
(from emergence to immersion in the sea) and show the number of
specimens. * Live specimens found during nest disinterring.

24 Herpetological Bullen 169 (2024)
Alessandro Paterna
Accepted: 7 February 2024
in some nests around the Mediterranean basin, within-
nest temperature dierences can generate variaons in the
hatchlings’ emergence paerns (Adam et al., 2007; Glen et
al., 2005; Field et al., 2021).
The emergence of the hatchlings from the nest occurred
over a period of 12 days (approximately 292 hours between
the rst and the last emergence), with the addion of two
live specimens recovered on the morning of the 15th day
(approximately 324.5 hours from the rst emergence). This
case represents one of, if not the longest, asynchronous
emergences reported in the literature (Hays et al., 1992;
Houghton & Hays, 2001; Adam et al., 2007). Although extended
asynchronous emergence might seem disadvantageous in
terms of natural selecon, minor emergence groups have
higher chances of surviving aquac predaon, as the number
of hatchlings entering the water is lower (Wyneken et al.,
1998; Pilcher et al., 2000; Glen et al., 2005).
A subject for future research would be the dispersal paern
and orientaon of the hatchlings following emergence in
the localies where nests of this species rarely occur. Since
the nest site was delimited by a fence, the hatchlings were
directed into a corridor that crossed the beach perpendicular
to the sea. However, immediately aer emergence the
hatchlings were free to orientate around the nest area and
there was a tendency for them to aempt to disperse more
towards the south rather than the east (in the direcon of
the water). This could be an eect of light polluon or other
variables (Witherington & Bjorndal, 1991).
Human acvity in coastal zones has a signicant impact
on the reproducon of sea turtles. This study highlights
the importance of nature reserves together with the work
of associaons and volunteers in the delivery of eecve
ecosystem conservaon.
ACKNOWLEDGEMENTS
I thank the associaons Centro Studi Cetacei and Guide della
Riserva Borsacchio and all of the volunteers for their work,
their help and for allowing me to study the deposion site
and parcipate in the monitoring shis. I thank Dr Chris
Michaels for suggested revisions.
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