Conservation and Ecology of Marine Reptiles

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Conservation and Ecology of Marine Reptiles MARE
494 Dr. Turner Summer 2007
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Reproduction
Occurs within 3 general contraints 1. Nesting
must occur during condition which are conducive
to adult activity 2. Nesting must occur during
conditions that favor embryo development
survival 3. Hatchlings must emerge into
conditions that are conducive to their survival
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Exhibition
All sea turtles exhibit 1. Iteroperous
reproduction (except Ridleys) 2. Stereotyped
nesting behavior 3. Laying relative large
numbers of eggs 4. Strong nesting site fidelity
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Exhibition
Semelparous organisms produce all of their
offspring over one relatively short period in a
single reproductive event.
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Exhibition
Iteroperous organisms produce their offspring in
a series of separate events, which means that
they have to save some of their resources to
survive between reproductive events.
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Adult Cycle
All species migrate (at least short distance)
from forage to mating areas - ? back to
foraging areas - ? to nesting beaches Cheloniids
reproduce on or near beaches
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Adult Cycle
Generalize Sea Turtle Life Cycle
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Distribution
Foraging areas widely distributed - cold
temperate (leatherback) to tropical Nesting
areas typically tropical subtropical D.
coriacea, C. mydas, N. depressus, E. imbricata,
L. kempi, L. olivacea mainland or island beaches
between Tropics of Cancer Capricorn C. caretta
temperate - subtropical
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Reproductive Statistics
Maturity gt 10 years Beach deep, loose sand
above high tide Philopatry (regional
decrimination) b/w forage nesting most lt1000
km, 2600 km May not return to specific beach of
birth but return to specific region Nest site
fidelity subsequent nesting 0-5 km Periodicity
1-9 years - L. kempi ? C. caretta annually???
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Reproductive Statistics
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Mating Activity
Precopulatory behaviors head bobbing, position
in water column, head-head bumps, nuzzling,
biting, movement of flipper, dinner ? mounts ?,
uses enlarged claws on fore hind flippers to
hold carapace Curls long tail to bring cloacea
into contact In captivity coupled gt 10hrs ?
Coupling ? Fertility
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Nesting Activity
General Requirements of Nesting Beaches 1.
Accessible from the sea 2. High enough to
prevent water inundation e.g. tides, water
table 3. Substrate facilitates gas diffusion 4.
Substrate must prevent collapse of egg chamber
during construction e.g. moist
fine-grained Typically ? salinity, ? humidity,
? ventilation
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Nesting Activity
Time of Nesting most at night Time required to
complete nesting process L. olivacea L. kempi
1 hr E. imbricata, N. depressus 1-1.5 hr C.
caretta 1-2 hr D. coriacea 1.5 hr C. mydas 2-3
hr Extreme durations Hawksbill 45 min Green 7
hrs
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Nesting Process
General nesting process similar in all
species Pattern contains 1. Emerging from
surf 2. Ascending the beach 3. Excavating the
body pit 4. Digging the egg chamber 5.
Oviposition 6. Filling the egg chamber 7. Filling
the body pit 8. Return to the sea
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Stages of Nesting Behavior
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Reproductive Characteristics
All species Lay several clutches during a
nesting season Lay white, spherical cleidoic
eggs with flexible calcareous shells Size of
eggs differs between clutches and among
species Size of eggs, of clutches
represent result of adaptive survival compromise
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Reproductive Characteristics
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Embryos!
Fertility is marine turtles typically high
gt95 measured by hatching success Factors that
can influences success Nutrition Health Stress
ors Human impacts Tightness of underwear
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Embryos!
When a ? sea turtle arrives on the nesting beach
carrying the full component of follicles to
supply yolks for all the eggs laid that
season Follicles increase in size slightly due
to H2O absorption
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Hatchlings!
Hatch after 6 13 weeks of incubation depending
upon temperature Weigh lt 50 of oviposition
weight Large eggs produce large hatchlings
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The Hatch!
Embryos use caruncle to cut through the amniotic
chlorio-allantoic membranes Shell ruptured,
amniotic fluid drains Reduction in volume allows
the space required for the hatchlings to wriggle
to the surface Social Facilitation
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Social Facilitation
The upward digging activity of the hatchlings
that is stimulated by the activity of the other
hatchlings usually from the bottom of the
chamber Typically emerge at night circumvent
two major problems with diurnal emergence 1.
Lethal temperature 2. Predators
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Hatching Success!
Clutches of sea turtle eggs typically have high
hatching success gt 80 Reduction of hatching
success caused by 1. Predation 2. Environmental
change 3. Microbial infection
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Hatchling Protection
Focus on conservation protection for reducing
turtles divides into two categories 1.
Protection of the animals 2. Protection of their
habitat This requires 1. Protection of eggs 2.
Protection of nests 3. Protection of foraging
areas 4. Protection of mating areas
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Temperature Effects
Incubation time is directly influenced by nest
temperature Thermal tolerance range (TTR) for
development of sea turtle embryos incubated at a
constant temperature appear to fall between
25-27C 33-35C
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Temperature Effects
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Temperature Effects
Temperature-dependent sex determination
produces ? at warm temps, ? at cool
temps Sensitive period for sex determination
takes place during middle third of
incubation Threshold temperature for the
transition of producing one sex to the other is
28-30C
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Temperature Effects
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Temperature Effects
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Temperature Effects
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Emergence Sea Finding
After emerging, hatchlings crawl toward the sea
sea-finding behavior occurs reliable in daylight
or at night in a variety of conditions
- cues hatchlings use are primarily visual
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Emergence Sea Finding
Cues hatchlings use are primarily visual
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Emergence Sea Finding
Sensitivity to directional light can be described
by a specific cone of acceptance which
indicates how much of the world a hatchling
measures at any one instant
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Light Effects
Artificial light a problem Not tied to full
moon Focused on light sources at the horizon
sources high in the sky (moon, streetlights)
often dont have a direct effect
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Wave Effects
As hatchlings complete their crawl across the
beach and enter the surf, they are lifted off the
sand by incoming waves When their flippers no
longer contact sand they being swimming
vigorously
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Orientation Mechanisms
Three types of cues visual, wave magnetic
orientation
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Chemical Imprinting
The chemical imprinting hypothesis for sea
turtles proposes that hatchling turtles imprint
on chemical cues unique to their natal beach and
use this information years later as adults to
return to the same beach for nesting
mating Little evidence to support or refute