September | October 2016 the Tortuga Gazette Volume 52, Number 5 California Turtle & Tortoise Club founded in 1964 and dedicated to Turtle & Tortoise Preservation, Conservation and Education Nesting female Australian flatback turtle, Natator depressus, photographed in habitat in Bowen, Queensland, Australia. Photo © 2009 by Stephen Zozaya. Reprinted with permission from the photographer. Flatback Sea Turtle, Natator depressus The Australian Flatback by M. A. Cohen he Australian flatback is a mem- covers the carapace of the flatback tur- museum specimens that went undiscov- ber of the Cheloniidae, the tle. Ordinarily, keratinized scutes cover ered for decades. superfamily of sea turtles, which the carapace of sea turtles species. In the 1980s, Rainer Zangerl and Colin Tis collectively the most endangered fam- The species was first described by Limpus concluded, through indepen- ily of turtles on the planet. Least studied American ichthyologist/herpetologist dent studies, that the Australian flatback of the seven living sea turtle species, the Samuel W. Garman (1843-1927) in 1880. was a unique species and not a relative Australian flatback turtle, Natator depres- Originally Garman assigned the Aus- of C. mydas (Spotila, 2004). sus, is unusual in several respects. tralian flatback to the genus Chelonia, The flatback was officially described It is the only sea turtle that is endemic, thinking it was a type of green turtle, and as a separate species in 1988 (Flatback, i.e., restricted to a certain area (Flatback, he gave it the name C. depressa. n.d.). Consequently, it was assigned to n.d.). The Australian flatback is the only Historically, there have been differ- the genus Natator, the name which was sea turtle that does not migrate extensive ences of opinion about how to classify first given it by McCulloch in 1908. Its distances in the open ocean. Moreover, the species. In 1908, Allan R. McCulloch species name was modified and became it does not venture into the deep ocean thought he had discovered a new spe- depressus. This name is now accepted by waters, but prefers the relatively shallow cies of sea turtle, and he named it Natator the scientific community. ocean waters near the Australian coast. It tessellates. Notwithstanding, in 1913, D. The word “natator” means “a swim- occasionally journeys to favored feeding B. Fry examined the skeletal material mer,” a fitting name for a sea turtle, grounds in southeast Asia. and life history stages of the species and the most pelagic of turtle species. The Like the carapace of the leatherback reverted to the name C. depressa, but species name depressus means “flat- turtle (Dermochelys coriacea), fleshy skin he made mistakes when preparing his tened” and refers to the carapace of 2 the Australian flatback, able of Contents which is noticeably less T domed than that of oth- Turtle of the Month er sea turtle species. Flatback Sea Turtle Identification Natator depressus The Australian flatback 1 The Australian Flatback by M. A. Cohen is a medium-to-large sea turtle species that reaches 4 Raine Island: the World’s Largest Green a mature carapace length Turtle Rookery by M.A. Cohen of 114.7 centimeters (45.2 5 Educating Hungry Ravens with 3D Printed inches) at maturity, aver- Tortoise Shells by Hannah Rose Mendoza aging 90 centimeters (35. A flatback hatchling makes its way from its nest to the ocean. Photo © 2010 by 4 inches). The average Purpleturtle57; source: CC-BY- SA-3.0 6 Herpetology 2016 - Chicago Herpetological Society weight of adults is 73 kilo- the Torres Strait area on the coast of 8 The Turtle’s Garden: Mulberry by M. A. Cohen grams (161 pounds) (Arkive, n.d.). Adult Papua New Guinea, and occasionally females are larger than adult males; on the Great Barrier Reef. the females have smaller tails than the in every issue : The Australian flatback has the longer, thicker tails of the males (Ernst, Table of Contents most limited range of any species of 2 et al., n.d.). sea turtle. As a result of its restricted Mike’s Turtle Net Picks by Michael J. Connor, PhD The adult flatback turtle possesses 7 range, the species is less endangered a relatively flat carapace that is oval s Meetings and Programs than other sea turtle species that in shape, and olive to gray to pale travel greater distances in the open 9 Classified Advertisements green in coloration. Fleshy hide that ocean. This does not mean that the is somewhat “slimy” to the touch cov- s Membership Information species is not threatened by external ers its carapace (Ernst, et al, n.d.). The pressures. See the section on conser- carapace narrows at both the front vation for more information. and rear of the oval, and its edges are Following nesting, females some- slightly upturned. times migrate hundreds of miles to The plastron of the flatback is cream- favored feeding grounds in the Ara- colored to pale yellow. The head and fura Sea of Indonesia. Nesting female neck are olive-gray above and pale flatbacks tagged in Australia have yellow below, while the flippers of the been recaptured in feeding grounds adult flatback are olive-gray on the top over 800 miles from the nesting beach. and cream-colored on the underside Follow CTTC on Facebook (Spotila, 2004). Feeding Hatchling flatback turtles are the Omnivorous in its feeding habits, N. largest of any sea turtle species, in- depressus consumes a variety of marine California Turtle & Tortoise Club: a Society Dedicated to Turtle & Tortoise Preservation, Conservation and creasing their chances of survival. The invertebrates, including bryozoans, Edu-cation Since 1964. Promoting and Facilitating the average carapace length at hatching is jellyfish, molluscs, sea cucumbers, Care, Rehoming, and Adoption of Native and Nonnative 6.1 centimeters (2.4 inches), with an av- sea pens, shrimp, and others (Spotila, Turtles and Tortoises. erage weight is 43 grams (1.5 ounces). 2004). The species also consumes sea- The Tortuga Gazette (ISSN 1073-1334) is owned by the Cal- The hatchling carapace is gray with grasses and soft corals (GBIF, n.d.). This ifornia Turtle & Tortoise Club Executive Board, which is each scute outlined in black. The edg- diet renders its flesh less palatable to incorporated in the State of California as a Not-for-Profit es of the carapace and the plastron of humans than that of herbivorous sea Corporation and is tax-exempt under IRS code 501(c)(3). the hatchling are white (Arkive, n.d). turtles, so humans rarely take flatback All material is copyright © CTTC unless otherwise attrib- turtles for food (Ernst et al., n.d.). uted. CTTC policy permits reproduction of articles by Range other not-for-profit groups and educational institutions N. depressus inhabits the conti- Reproduction when permission is requested. Permission is granted on a nental shelf of tropical northern and The Australian flatback breeds and case-by-case basis and CTTC must be cited as the source of the material. eastern Australia, from the Kimber- nests throughout its range off the Views expressed in the Tortuga Gazette are those of the ley region in the state of Western coast of northern Australia as well contributors and not necessarily those of the Editor or the Australia, across the Northern Ter- as “patchily along the Great Barrier California Turtle & Tortoise Club. ritory to the Torres Strait between Reef” (Cogger, 1992). The Torres Strait region between Cape York Penin- Is your email address changing? the Cape York Peninsula and Papua New Guinea. Cape York Peninsula is sula in Queensland and Papua New Update your email address through your on the northern tip of the state of Guinea is the area with the greatest MailChimp account, or send address Queensland. The flatback turtle also concentration of flatback nesting changes and corrections to this address: inhabits coastal regions off eastern sites. The largest single flatback nest- [email protected] Queensland. The species is found in ing colony occurs on Crab Island in Tortuga Gazette Volume 52, Number 5 3 the northeastern Gulf of Carpentaria in from their nests. flatback populations to be at significant Queensland (Spotila, 2004). Once they reach the sea, flatback hatch- risk from predation.” The Australian gov- The nesting season varies by locality, lings and juveniles become the prey of ernment does protect nesting beaches, as and is likely linked to the local climate. various species of fish and sharks that pa- well as protecting turtles at sea through On the southern Queensland coast, for trol the shallow waters of the continental the required use of Turtle Excluder De- example, flatbacks nest mainly between shelf awaiting the arrival of the hatchlings vices on many shrimp trawlers (Spotila, October and January, whereas on Crab Is- (GBIF, n.d.). Sea turtle biologists estimate 2004). However, incidental capture in gill land in the Gulf of Carpentaria they nest that, in general, only one out of every 100 nets and other types of fishing gear also year-round. In some areas, flatbacks nest sea turtle hatchlings lives to maturity. poses a risk to flatbacks in coastal waters. from March to October during the dry sea- The IUCN Red List finds that the species son, while in others, the turtles nest from Predation and Conservation is “data deficient” but notes the need for Nest predators include the native din- October to February during the rainy sea- an update to that finding. The flatback is goes (Canis familiaris dingo) and monitor son (Spotila, 2004). Nesting typically takes in danger of extinction in coastal Western lizards [goannas] (Varanus gouldii, V. pan- place on undeveloped, isolated beaches. Australia, and faces imminent threats off optes), and the introduced red fox (Vulpes Mating occurs in the shallow coastal the northern Kimberley coast due to in- vulpes) (GBIF, n.d.).