N.Z.’s RARER REPTILES — THE TURTLES

Press, Volume CXV, Issue 33965, 4 October 1975, Page 12

N.Z.’s RARER REPTILES — THE TURTLES

(Contributed by the Canterbury Museum)

Unless you spend a lot of your time at sea or are addicted to beachcombing the chances of finding any of the marine turtles which occasionally straggle into New Zealand seas or get stranded on our coastline are remote. The reason for the scarcity of marine turtles here is obvious — they prefer warmer seas. This is why most sightings are from the wanner waters of the North Island. Once in a while, however, some marine turtles do straggle further south, even into Foveaux Strait. Recently we were notified of a turtle which was caught alive in a net 48 miles west of Greymouth and of a second specimen which became entangled in the rope of a crayfish-pot buoy further south in Jackson’s Bay. These turtles probably unwittingly moved into the East Australian Current, a stretch of warm water which flows down the West Coast of New Zealand into the cooler southern ocean. “Paddle” flippers Except for the New Guinea paddie - limbed fresh water turtle, all seagoing turtles differ from their fresh or landdwelling relatives by their paddle-like forelimbs or flippers. Another adaptation to a

water environment is the heart-shaped dorsal shell. On marine turtles this structure is flattened and streamlined, a feature which enables them to swim rapidly through water. The nostrils, too, are adapted for living in water these are located on top of the head so that when the animal wants to breathe it simply surfaces its head. Inside each nostril is a fleshy valve which closes when the turtle dives. Four species of marine turtle stray into our seas —the hawksbill, green, loggerhead and leathery (leatherback or luth) species. The largest of these is the leatherback (illustrated) which is also one of the world’s biggest turtles. Although they are far from the size of some of their extinct relatives, large specimens are eight feet long and weigh over half a ton. Small bones An interesting feature of the leatherback’s dorsal shell is that it is made up of a mosaic of small bones. On the upper surface of the shell are seven ridges. These ridges protrude out of the water, giving the general impression of an upturned partially submerged clinker-built dingy. The second species known here — the green turtle — gets its name from the colour of its fat. This species is used to make the popular green turtle soup of gourmet

fame. The adult averages three feet in length and weighs 75 to 1501 b, but exceptionally large individuals can reach 7001 b. The shell is olive or brown, and indistinctly blotched or mottled with yellow, while the underparts are various shades of yellow. Endangered species Appropriately named because of its hooked beak, the hawksbill turtle, while not hunted as a food, is sought after for its beautiful shell. This is composed of a number of clear yellow plates richly streaked with mottled brown which furnish the well-known tortoise shell of commerce. Specimens with dorsal chpll nf thrpA fppt

were once fairly common, but today an individual with a shell two feet long is considered large. Body weights can reach 601 b but nowadays few individuals captured exceed 301 b. These smaller specimens, biologists believe, are a result of the hawksbill turtle being overhunted to the extent that this animal is considered an endangered species. A feature of the last species found in our seas, the red-brown or Atlantic loggerhead, is its large head — in an old specimen the head may be 11 inches long. As is the case with many other turtles hunted by man, 8501 b individuals, measuring 9ft from tip to tip of their outstretched flippers, seem to be a phenomenon of the past.

The upperparts of the young loggerhead range from black to dark brown. The adults are brown to reddish brown above and lemon to pale orange below. The young of the species make good pets and survive for 30 years or more in captivity, but adults are vicious. Should any reader come across a marine turtle we would like to be notified. To help us identify your specimens please include sketches and photographs showing a side and top view of the head and some snaps of the upper shell and underparts. This information is particularly useful since very little is known about the biology of these fascinating creatures in New Zealand waters. — G.A.T.