Conservation and Ecology of Marine Reptiles MARE 490 Dr. Turner Summer 2011

Variation in Life History Patterns Sea turtles – slow growing & long lived Complex life history patterns Diversity of ecosystems – terrestrial (oviposition & embryonic development), neritic, coastal, & oceanic zones (developmental & foraging habitats)

Terminology Standard oceanographic terminology Neritic zone – inshore marine environment from surface to sea floor; <200m Oceanic zone – vast ocean environment from surface to sea floor; >200 Pelagic – if occupy water columns Epipelagic – if occupy upper 200m Benthic or demersal – ocean floor

Variation in Life History Patterns Three primary life history patterns- Characteristics of developmental stages (oceanic & neritic) and adult foraging patterns (oceanic & neritic) are primary differences that distinguish

Sea Turtle Life History Patterns Once hatchlings emerge from their nests, crawl down the beach, and enter the ocean 3 types of basic life history patterns: Type 1: Complete development in neritic zone Type 2: Early juvenile development in oceanic & later juvenile development in neritic zone Type 3: Complete development in oceanic

Type 1: Neritic Pattern Development & adult stages in neritic Flatback only extant example Hatchlings are larger than other chelonids 60 vs mm; 39 vs g Clutch size smaller Suggests ↑ food resources in neritic but tradeoff of ↑ predation; but “Bigger is better”

Type 1: Neritic Pattern

Type 2: Oceanic-Neritic Pattern Early development oceanic - later neritic Best known loggerhead, also green (black?), hawksbill, Kemp’s ridley; possibly Olive Move to oceanic after hatching for several years; in loggerhead Recruit back to neritic before maturity; often slow transition from oceanic Return to oceanic for migration

Type 2: Oceanic-Neritic Pattern

Type 3: Oceanic Pattern Developmental & Adult in oceanic zone Leatherback & Olive Ridley Little known about juvenile life history – thought to be oceanic Very different species physiologically Olive - spend large portion at surface (>20%)

Type 3: Oceanic Pattern

Habitat Utilization &Migration

Generalized habitat model for sea turtles based upon ontogenetic stages 1. Early juvenile nursery habitat (pelagic or oceanic) 2. Later juvenile development habitat (demersal & neretic) 3. Adult foraging habitat 4. Adult inter-nesting and/or breeding habitat

Juvenile Nursery Habitats 1 st year known as “Lost year” as hatchlings migrate to the offshore environment and do not return to the neritic environment until they have grown into much larger juveniles Assumed that time is spent exclusively in offshore/pelagic habitats

Early Juvenile Loggerheads Best documented – typically associated with oceanic convergence zones - Sargassum habitat Thought to be “lost decade” instead of “lost year” due to extreme duration in the pelagic environment

Later Juvenile Loggerheads Recruit from oceanic to neritic after 7-10y; 25-30cm Strong site fidelity once recruited Return to same foraging sites after nesting Often brumate in winter (semi-hibernation state in which a reptile sleeps a majority of the time, and eats very little)

Early Juvenile Kemp’s Ridley Typically spend first two years at sea Move throughout the Gulf of Mexico and into South Atlantic (> 29%) If such a large population utilizes the Atlantic then must be able to efficiently return to the GOM No info on Olive Ridleys Flatback lack pelagic stage

Later Juvenile Kemp’s Ridley Recruit from oceanic to demersal neritic at 20-25cm Throughout Gulf of Mexico, Atlantic as far north as New York Bays are important habitats; Chesapeake, Mobile, Galveston

Juvenile Olive Ridley Nothing known about early juvenile nursery area – probably pelagic & oceanic Little known about later juvenile habitats may use either coastal or oceanic

Juvenile Flatback Lack oceanic stage – juveniles spend entire life history in coastal neritic waters

Early Juvenile Green Swim continuously for first 24 hrs Strong counter-coloration patterns in hatchlings/juveniles Recruit to neritic environment at a smaller size then loggerheads – less than 2 yrs Loggerhead Green

Later Juvenile Green Recruit to demersal habitat at 30-40cm Typically coral reefs, rocky shore, or seagrass meadows Tropical-subtropical estuaries

Early Juvenile Hawksbill Some remain on local reefs Those recruiting back to neritic systems are smaller than greens & loggerheads < 1-3 yrs Recruit at small size 20-25cm

Later Juvenile Hawksbill Restricted to tropical systems more than any other sea turtle Shallow coral reefs & mangroves – both abundant with sponges Strong site fidelity

Early Juvenile Leatherback Move to pelagic environments immediately Disappear to oceanic environment for 4 years based upon growth rates Need to consumer body weight/day in gelatinous prey

Later Juvenile Leatherback Thought to be tied to upwelling to support high biomass of gelatinous prey Remain in pelagic waters as adults

Survivorship Natural selection will favor those nesting locations with the highest survivorship during the early juvenile stage Most important determination of nesting beach location is survivorship of hatchlings and small juveniles in the nursery habitats

Survivorship As with fishes – number & diversity of predators & resulting mortality rates and inversely proportional to size of the juvenile “Bigger is Better” Advantage of pelagic-oceanic nurseries: low density of predatory fishes & birds due to low primary production

Adult Migration & Habitat Use Exhibit longest migrations of any reptile Hundreds to thousands of miles between feeding & breeding areas Inter & intraspecific variation in migratory behavior in extant turtles Probably parallel in potential navigation systems employed

Leatherback Widely distributed throughout the world’s oceans Highly migratory, capable of transoceanic migrations Elusive, little known about migrations

Olive Ridley Circumtropical distribution; Atlantic, Pacific, & Indian Oceans Little known about migrations Spends non-breeding life cycle in oceanic zone Occupy neretic zones during breeding seasons

Kemp’s Ridley Relatively restricted range – neritic zone of Gulf of Mexico & Atlantic Swim through shallow coastal waters along US & Mexico Arribadas occur every 28 days

Hawksbill Distributed through tropical waters of Atlantic, Pacific, & Indian Oceans Associated with hard-substrate community such as coral reefs – spongivory Once thought to be non-migratory; some migrate vast distances Locally some only migrate along the Big Island

Flatback Most restricted migratory range of all sea turtles Endemic to tropical waters of Australian continental shelf Once thought non-migratory; now known long-distance migrations

Loggerhead Occur in subtropical & temperate waters across continental shelves & estuarine areas in Atlantic, Pacific, & Indian Oceans Nearshore & inshore waters Highly migratory, hundreds to thousands of Km between feeding & breeding

Occur in tropical & subtropical waters of Atlantic, Pacific, & Indian Oceans Nearshore & inshore waters; forage on sea grasses & algae Oceanic habitat between foraging & breeding areas Locally between MHI & NWHI Green

Black Restricted to coastal waters, lagoons, & bays along W. coast of US to S. Peru Feed on seagrass & algae Nest in Central America & Mexico

Adult Migration & Habitat Use Distinct migratory patterns which are different than developmental patterns Best understood in context of location & size of foraging area Migrating behavior & navigation systems still much unknown

Adult Migration & Habitat Use 1 st pattern: Migrate to oceanic waters where they forage over very broad areas Very spatially & temporally variable; unpredictable (Leatherback & Olive Ridley)

Adult Migration & Habitat Use 2 nd pattern: Migrate to highly productive neritic foraging areas located on continental shelves (Kemp’s Ridley, Loggerhead, Flatback)

Adult Migration & Habitat Use 3 rd pattern: Migrate to well-established, fixed foraging areas located nearshore Relatively small foraging area & virtually no spatial or temporal variation exists (green & hawksbill)