2018-马尔代夫海龟_现场识别指南（英文版）-21mb

Summary of "Marine Turtles of the Maldives – A Field Identification Guide"

Core Content

This document is a comprehensive field identification guide for marine turtles found in the Maldives. It provides essential information on the biology, ecology, and conservation of marine turtles in the region, along with practical guidance for identifying and responding to turtle-related situations.

Main Points

1. What is a Turtle?

• Turtles are long-lived reptiles in the order Reptilia, which includes snakes, lizards, and crocodiles.

• They are characterized by:

  • Scaly skin
  • Cold-blooded (poikilothermic) nature
  • Air-breathing
  • Oviparous reproduction (laying eggs)

• Marine turtles are a subset of turtles that live in the ocean, with adaptations for marine life:

  • Streamlined shells and flippers for efficient swimming
  • Specialized circulatory and respiratory systems for diving
  • Salt glands to expel excess salt from the body

• Marine turtles are not able to retract their head and limbs into their shell, unlike tortoises.

2. How Old Are Marine Turtles?

• The oldest known turtle fossil is from 220 million years ago and resembled a modern freshwater snapping turtle.
• Marine turtles appeared around 120 million years ago during the Cretaceous era.
• The Archelon ischyros, a giant marine turtle from the late Mesozoic era (around 65 million years ago), was a slow-moving grazer with a 4.5m shell and 2,200kg weight.
• Only two families of marine turtles remain today: Cheloniidae (6 of 7 species) and Dermochelydae (1 species, the leatherback).

3. Adaptations to Marine Life

• Great Divers: Marine turtles have efficient respiratory and circulatory systems that allow them to stay submerged for long periods.

  • No diaphragm, using fused ribs for efficient breathing
  • High levels of haemoglobin and myoglobin for oxygen storage
  • Counter-current heat exchange system to regulate body temperature

• Keeping Warm in the Water:

  • Cold-blooded and poikilothermic
  • Use circulatory adaptations to retain heat in the core of the body and minimize heat loss in the flippers

• Surviving in a Salty Environment:

  • Specialized salt glands behind the eyes expel excess salt via tears
  • On land, these tears are often mistaken for signs of distress

4. The Lifecycle of Marine Turtles

• Marine turtles have a complex lifecycle:
  • Female turtles come ashore to lay eggs on nuptal beaches
  • Eggs hatch after 40–60 days
  • Hatchlings crawl to the sea and swim offshore, often referred to as the "lost years"
  • They feed on Sargassum and other surface organisms
  • After a few years, they settle in coastal areas to forage and grow until reaching sexual maturity
  • Adults then migrate to mating and nesting grounds

5. Marine Turtles in the Maldives

• The Maldives is home to five marine turtle species:

  • Green turtle (Chelonia mydas)
  • Hawksbill turtle (Eretmochelys imbricata)
  • Loggerhead turtle (Caretta caretta)
  • Olive Ridley turtle (Lepidochlys olivacea)
  • Leatherback turtle (Dermochelys coriacea)

• Each species has a unique Divehi name and is described with key features:

  • Green turtle: "Velaa"
  • Hawksbill turtle: "Kahan'bu"
  • Loggerhead turtle: "Boa bodu velaa or Varvohori"
  • Olive Ridley turtle: "Vaa voshi velaa"
  • Leatherback turtle: "Musimbi"

6. Threats to Marine Turtles

• Global threats include:

  • Natural threats: such as storms, predators, and disease
  • Anthropogenic threats: including direct harvest, bycatch in fisheries, ingestion of marine debris, artificial lighting, erosion and beach armouring, invasive vegetation, and predators

• Local threats in the Maldives include:

  • Direct harvest (poaching)
  • Bycatch in fisheries (especially longline and trawl fishing)
  • Ingestion of marine debris
  • Artificial lighting and urban development on nesting beaches
  • Erosion and beach armouring
  • Invasive beach vegetation and predators

7. Conservation Efforts

• Legislation in the Maldives includes:

  • National laws and international conventions such as CITES and CMS
  • Population monitoring and photographic identification (Photo-ID) are used to track and conserve turtle populations

• What to do if you see:

  • A turtle nesting: do not disturb, observe from a distance
  • A turtle: keep a safe distance and avoid touching
  • An injured turtle: report to local conservation authorities
  • A lost hatchling: do not move it, allow it to reach the sea naturally

Key Information

• Cold stunning occurs when sea temperatures drop below 10–15°C, causing turtles to float, have reduced heart rate, and be vulnerable to predators and boat strikes.
• Marine turtles use magnetic imprinting to navigate back to their natal beaches for nesting.
• Some turtles may have multiple paternities in a single clutch, with up to five fathers.
• Sargassum is a crucial habitat for young turtles, providing food and shelter.
• The guide is authored by Jillian Hudgins, Agnese Mancini, and Khadeeja Ali, published by IUCN and the Government of Maldives, with support from USAID and Global Blue.

Conclusion

This guide is an essential resource for identifying marine turtles in the Maldives, understanding their biology and ecology, and contributing to their conservation. It highlights the importance of these animals in the ecosystem and the various threats they face, both globally and locally. Readers are encouraged to respect and protect marine turtles, especially during their nesting and early life stages.