The arrival of olive ridley turtles (Lepidochelys olivacea), seen from the air in Playa Ostional, pacific coast of Costa Rica.
The olive ridley has one of the most extraordinary nesting habits in the natural world. Large groups of turtles gather off shore of nesting beaches. Then, all at once, vast numbers of turtles come ashore and nest in what is known as an "arribada". During these arribadas, hundreds to thousands of females come ashore to lay their eggs. At many nesting beaches, the nesting density is so high that previously laid egg clutches are dug up by other females excavating the nest to lay their own eggs.
There are many theories on what triggers an arribada, including offshore winds, lunar cycles, and the release of pheromones by females. Despite these theories, scientists have yet to determine the actual cues for ridley arribadas. Not all females nest during an arribada, instead some are solitary nesters. Some olive ridleys employ a mixed nesting strategy. For example, a single female might nest during an arribada, as well as nest alone during the same nesting season. Arribada nesting is a behavior found only in the genus Lepidochelys: Kemp’s ridley sea turtles and olive ridley sea turtles. Although other turtles have been documented nesting in groups, no other turtles (marine or otherwise) have been observed nesting in such mass numbers and synchrony.
photos by mikeroberts, masa ushioda, peter liu and doug perrine of green sea turtles being cleaned by yellow tangs, goldring surgeonfish and saddle wrasse. by feeding on the algea and parasites which grow on the turtle shells, the fish not only keep them clean, but reduce drag, helping the turtles to swim faster.
endangered hawaiian green sea turtle (or honu in hawaiian) swimming under breaking waves. the sea turtles come into the shallow waters to eat seaweed off of the reef and are very skilled at being just the right distance away from the dangers of the crahsing waves. photos by clark little, viatheseadditionalsources. (more sea turtle posts)
Pollution in urban and farm runoff in Hawaii is causing tumors in endangered sea turtles, a new study finds.
The study, published Tuesday in the peer-reviewed open-access journal PeerJ, shows that nitrogen in the runoff ends up in algae that the turtles eat, promoting the formation of tumors on the animals’ eyes, flippers and internal organs.
Scientists at Duke University, the University of Hawaii and the National Oceanic and Atmospheric Administration (NOAA) conducted the study to better understand the causes behind the tumor-forming disease Fibropapillomatosis, which is the leading known cause of death in green turtles, said Kyle Van Houtan, adjunct associate professor at Duke’s Nicholas School of the Environment.
"We’re drawing direct lines from human nutrient inputs to the reef ecosystem, and how it affects wildlife," said Van Houtan, who is also a scientist in NOAA’s Turtle Research Program.
Caption: This image shows a sea turtle with tumors caused by fibropapillomatosis.Credit: Chris Stankis
From bottom to top: 1. Common Snapping Turtle (Chelydra serpentina) 2. Geometric Tortoise (Psammobates geometricus) 3. Galapagos Tortoise (Dipsochelys dussumieri) 4. Argentine Snake-Necked Turtle (Hydromedusa tectifera) 5. Mata Mata (Chelus fimbriata) 6. Leatherback Turtle (Dermochelys coriacea) 7. Hawksbill Turtle (Eretmochelys imbricata)
The Testidunes (or Chelonii, often called Chelonians) are the reptiles belonging to the order Testudines, and include all of the turtles and tortoises. This order is characterized by their protective bony carapaces, which developed from their ribs millions of years ago. Ribs still line the inside of the shell.
As they’re reptiles, they’re ectothermic, and their body temperature adjusts to the surroundings. They’re all amniotes, as well - that is, they lay eggs outside of the water.
The carapace of most chelonians is covered by bony, overlapping plates, called scutes. However, some species, such as the leatherback sea turtle, have a thick, oily skin covering their carapace instead. Chelonians also have a protective chest plate, called a plastron.
The difference between “turtle”, “tortoise”, and “terrapin” is defined differently depending upon your field and what part of the world you live in. In general, turtles live in either freshwater or the ocean. Tortoises live on dry land and cannot swim. Terrapin is a more specific term for some turtles, referring to the small, edible, hard-shelled turtles.
While all chelonians can be long-lived (as their organs do not suffer age-related decay), large torotoises are the best-known for living over a hundred years. Jonathan, a Seychelles Giant Tortoise, is 183 years old next week, and is the oldest living creature on earth!