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Technical Report #178.
Seitz, W.A., K.M. Kagimoto, B. Luehrs and L. Katahira. 2012. Twenty
years of conservation and research findings of the Hawai‘i Island
Hawksbill Turtle Recovery Project, 1989 - 2009
6 MB
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ABSTRACT:
Prior to 1989, available information on nesting hawksbill turtles (Eretmochelys
imbricata) in the Hawaiian Islands was minimal. From 1987 to 1990,
personnel from Hawai‘i Volcanoes National Park conducted reconnaissance
along the southern coastline of Hawai‘i Island to confirm evidence of
nesting activity, identify hawksbill nesting beaches, and evaluate
threats. Thereafter, the Hawai‘i Island Hawksbill Turtle Recovery
Project (HIHTRP) was established to monitor and manage nesting sites,
document nesting events, collect baseline data, ensure hatchlings safely
reach the ocean, and mitigate threats. Between 1993 and 2009, the number
of beaches monitored for nesting activity expanded from eight to 17,
with variable coverage at each site. Flipper tagging of nesting adult
females has occurred since 1991. Primary findings from twenty years of
data collection include: 1) The southern coast of Hawai‘i Island has the
highest documented hawksbill nesting activity in the Main Hawaiian
Islands; 2) Nesting season (egg laying to hatchling emergence) begins in
April and extends to February with a peak egg laying period from
late-July to mid-September; 3) The mean seasonal cohort observed was
11.6 ± 1.2 (n= 18) with a range of 3 to 18 turtles; 4) The mean number
of nests per turtle was 3.3 ± 0.2 per season (n= 20) with a range of 1
to 6 nests; 5) The mean remigration interval was 3.5 ± 0.1 years (n=
106) with a range of 2 to 10 years; 6) Nesting turtles demonstrated a
high degree of nesting site fidelity, with 87% of individuals documented
using only one nesting site. Forty-eight of these individuals were
documented at the same beach in multiple years. Thirteen percent of
nesting females were documented at multiple sites; 7) The mean nest to
next crawl inter-nesting interval was 18.6 ± 0.1 days (n= 276) (range 13
to 24 days), while the mean nest to nest inter-nesting
interval was 20 ± 0.2 days (n= 277) (range 13 to 30 days); 8) The mean
incubation period was 62.5 ± 0.4 days (n= 446) with a range of 50 to 101
days; 9) The mean clutch size was 175.2 ± 1.5 eggs (n= 631) with a range
of 78 to 274 eggs; 10) The mean nest hatch success of eggs was 71.9 ±
1.0% (n= 640) with a range of 0 to 100%; 11) Between 1991 and 2009, 100
adult females were tagged, with a mean of 5.3 ± 0.7 (n=19) and range of
1 to 11 per season; 12) Between 1988 and 2009 a total of 742 nests (most
occurring at Kamehame, ‘Āpua Point, and Pōhue Bay) were documented with
a mean of 35 ± 4.0 (n= 21) and range of 8 to 69 per season; 13) Between
1989 and 2009, over 80,775 hatchlings are estimated to have entered the
Pacific Ocean from Hawai‘i Island; 14) Primary threats to nest and
hatchling success all of which have been significantly addressed were
non-native mammalian predators, alien plants, artificial lights,
hatchling stranding, vehicular traffic, and incompatible recreational
use of nesting beaches; 15) Volcanism including land subsidence remains
as an uncontrollable factor.
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