Gazelle : The Palestinian Biological Bulletin (ISSN 0178 – 6288) . Number 115, July 2014, pp. 1-9. | Page 3

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physical conditions prevailing in the nests. During the 1986-1989 nesting seasons
(mid-May through July), Silberstein and Dmi'el (1991) surveyed repeatedly, in
collaboration with the rangers of the Nature Reserves Authority, 35 km of beach
along the northern Mediterranean coast of Palestine. A total of 34 loggerhead
nests were found in this area (16 nests were found in 1986, 10 in 1987, 4 in 1988, 4
in 1989). The earliest clutch was laid on 21 May, the latest on 27 July. Most of the
nests were located <10-50 m beyond the high-tide line. Only a few were found
further, in the dunes, some 80-150 m beyond the high-tide line. The average
clutch size was 82 eggs (range 55-149). The average period of incubation was 54
days, ranging from 60-62 days in May (temperature in the center of the nest =
26.5°C) to 50-52 days in late July (nest temperature = 30°C) (Silberstein and
Dmi'el 1991).
During 1986-1989, hatching success varied considerably among nests, ranging
from 0%-90%. Hatch failure was attributed to the depth of the nest and to its
location with respect to the water line. Typically, nests were dug by the female to
a depth of 30 cm (upper egg layer) to 50 cm (lower egg layer) below the sand
surface. At this depth, the sand humidity (average water content 3%) and the
daily temperature fluctuation (2°C) were stable. Four nests, however, were
constructed so that the uppermost eggs were only 10-15 cm below the sand
surface. In these cases, strong temperature fluctuations and sand desiccation
resulted in an average hatching success of only 6%. Eleven nests, located too
close to the high-tide line, were exposed to summer storms that occasionally
occur in this area. Seawater inundation resulted in an almost complete cessation
of embryo development, resulting in 0-11% hatching success (Silberstein and
Dmi'el 1991).
A sharp decline in the number and density of loggerhead sea turtle nests in
Palestine is attributable to both regional and local processes. On the one hand, an
immense fishing of turtles took place in the eastern basin of the Mediterranean
Sea during the first half of last century. Today the intensity of this activity has
diminished, but the consequences for the loggerhead population are still very
conspicuous. Concomitantly, a local large-scale excavation of beach sand for
concrete production took place in occupied Palestine. This altered the structure
of many beaches in which female loggerheads dug their nests (Sella 1982). The
present situation demands that immediate protective measures be taken. The
first emergency step should be to rescue eggs laid in poorly located nests, as is
done for other sea turtle species (e.g., Eckert and Eckert 1990). These eggs should
be transplanted over the shortest practicable distance and reburied under
favorable natural conditions (at a beach hatchery site if necessary). As a last
resort, and only if beach reburial is not possible, eggs may be artificially
incubated in the laboratory. This procedure has been shown to result in high
(90%) hatching success (Silberstein 1988). In either case, hatchlings should be
Gazelle : The Palestinian Biological Bulletin – Number 115 – July 2014