African Side-Necked Turtles: Pelomedusidae

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AFRICAN SIDE-NECKED TURTLES: Pelomedusidae

HELMETED TURTLE (Pelomedusa subrufa): SPECIES ACCOUNT

PHYSICAL CHARACTERISTICS

African side-necked turtles are small- to medium-sized turtles that fold their necks sideways under their shells, rather than pulling them straight back into the shell, along with their heads. They have five claws on each hind foot. The upper shell, or carapace (KARE-a-pays), of adults usually is less than 1 foot (30.5 centimeters) long, but the length of shells can range from about 4 to 21.6 inches (10–55 centimeters). The turtle has a large lower shell, or plastron (PLAS-trun), that covers much of the chest and belly. Sometimes the plastron has a hinge that allows the animal to pull its lower shell quite tight against the upper shell and offers protection from predators (PREH-duhters), or animals that seek these turtles out as a source of food. In addition, the turtles have glands, or special organs, along the sides of their bodies that give off a musky, or earthy, smell to ward off attackers.

GEOGRAPHIC RANGE

African side-necked turtles live in Africa, Madagascar, and the Seychelles Islands, which are northeast of Madagascar.

HABITAT

These turtles often are seen in freshwater lakes and rivers that hold water all year long, but they also are found in temporary freshwater ponds, which lose their water during the dry season. Some side-necked turtles, including those that are called "mud turtles," spend much of their time in soft-bottomed ponds that are filled with water for only a few weeks every year.

DIET

African side-necked turtles are mainly meat eaters, although a few will eat plants. The main items in their diet are worms; clams and other mollusks, or soft-bodied animals covered by shells; shrimp and other crustaceans (krus-TAY-shuns), or animals with a soft, segmented body covered by shells; insects; fish; frogs and other amphibians (am-FIB-ee-uns), or animals that spend part of their lives in water and part on land. These turtles also eat whatever dead animal matter they can find. Those that eat plants prefer water lettuce and grasses that grow in lakes, ponds, and streams and various fruits that drop into the water from overhanging trees.

BEHAVIOR AND REPRODUCTION

Although these side-necked turtles can be quite noticeable in their habitat, scientists know very little about their behavior. The turtles bask, spending warm days sunning themselves near the shoreline. They are especially active during the wet season, when they may roam over land. When the weather turns dry, many side-necked turtles seek shelter underground. Those that live in the cool, mild climate of the far south of Africa may hibernate, or become inactive, on land or under water through the winter months.

These turtles breed during late spring or summer, with the females laying six to four dozen oblong-shaped eggs. Scientists suspect that the turtles may have more than one set of young every year. The outside temperature controls how many eggs in a clutch, or group, will develop into males and how many will develop into females. Scientists call this "temperature-dependent sex determination," or TDSD. If the weather is constantly warm or especially cool, most of the young are females. If the weather is more temperate, or mild, most are males.

THE TURTLE–RHINO CONNECTION

Although few people would think that turtles get much of their food from rhinoceroses, several African side-necked turtles do rely on the large mammals for some of their food. The turtles do not eat the rhinos but rather wait for them to wade into a water hole and then swim up to nibble off the ticks that cling to their hides. Rhinos are not the only buffet table for the turtles. They will do the same with other large herding animals that stop by for a drink.

AFRICAN SIDE-NECKED TURTLES AND PEOPLE

African side-neced turtles are unpopular as pets and as food, but people occasionally eat them. One reason for their lack of popularity is their smell. The musk glands are very powerful weapons against predators, including humans. Pet owners who keep African side-necked turtles often find that they are unfriendly and can be aggressive; they will bite at other turtles in the same aquarium and will nip at humans who put their hands too close.

CONSERVATION STATUS

In 2003 the World Conservation Union (IUCN) listed one species, the Seychelles mud turtle, as Extinct; none of these turtles is still alive. In addition, it listed the Magdalena river turtle and the Madagascar big-headed turtle as Endangered, meaning that it faces a very high threat of extinction in the wild. Five species are Vulnerable, which means that there is a high threat of their extinction, and one is Near Threatened, meaning that it is at risk of becoming threatened with extinction soon. Many of these species live in very small areas, so even slight disturbances can kill populations and possibly the entire species. For example, the Broadley's mud turtle, which is listed as Vulnerable, is found only in Lake Rudolph (also known as Lake Turkana) in Kenya.

HELMETED TURTLE (Pelomedusa subrufa): SPECIES ACCOUNT

Physical characteristics: Adult helmeted turtles have upper shells that reach 13 inches (33 centimeters) in length. The brown to greenish-brown upper shell is fairly flat. The lower shell is usually yellow or cream-colored, sometimes with dark seams or large, dark smudges. The lower neck is also yellow or cream-colored. These turtles have a rather pointed face with a mouth that looks as if it is set in a permanent grin. Males and females look alike, except that males have longer tails and concave, or indented, lower shells. Males may have red spots or white coloration on their heads during mating season.

Geographic range: Helmeted turtles inhabit Madagascar, southern Saudi Arabia, Yemen, and central to southern Africa.

Habitat: Helmeted turtles can be found in various water bodies, including ponds, marshes, and streams that are filled with water all year long and temporary ponds that dry up from time to time. They move from water site to water site during the year, so they are often seen on land.

Diet: Like other side-necked turtles, helmeted turtles are mostly meat eaters, feeding on worms; snails and clams; insects and other small invertebrates (in-VER-teh-brehts), or animals without backbones; fishes; frogs; and whatever dead animals they can find. They also eat small reptiles and mammals. They are some of the only reptiles that will band together and hunt as a pack to catch, drown, and tear apart birds, mammals, and other reptiles. An occasional piece of fruit or water-living plant rounds out the diet.

Behavior and reproduction: Except those individuals that live in the hottest of climates, these turtles spend much of the day basking near the shoreline. They are also noticeable when they are moving from water body to water body. The young will eat all day long and into the night, but the adults tend to feed only in the early morning or early evening hours. When the weather is too dry, they will bury themselves in the mud until the rains come. This period of inactivity in dry weather, which is called estivation (es-tuh-VAY-shun), can last for months. In the cooler areas where they live, they hibernate by finding a spot under leaves or below ground to wait out the winter.

Mating usually happens in the spring. During courtship, a male will chase a female, touching and sometimes nipping at her back legs and tail; bob his head from side to side; and shoot water out of his nostrils. The females lay one set of thirteen to forty eggs every year (fewer than twenty eggs is typical) in a nest that is sometimes set among rocks. The outside temperature determines the number of male and female young in the clutch. Especially warm or cool temperatures will produce more females, while moderate temperatures yield males.

Helmeted turtles and people: Although people frequently see this common turtle, it does not usually notice or mind their presence, even sometimes entering and making good use of man-made ponds. Some people eat helmeted turtles or drain their blood for folk medicines; a few become pets. These practices have not affected the survival of the species.

Conservation status: The helmeted turtle is not threatened. ∎

FOR MORE INFORMATION

Books:

Boycott, R. C., and O. Bourquin. The Southern African Tortoise Book: A Guide to Southern African Tortoises, Terrapins and Turtles. KwaZulu-Natal, South Africa: privately printed, 2000.

Branch, B. Field Guide to the Snakes and Other Reptiles of Southern Africa. Cape Town, South Africa: Struik Publishers, 1998.

Burnie, David, and Don E. Wilson, eds. Animal: The Definitive Visual Guide to the World's Wildlife. London: Dorling Kindersley, 2001.

Spawls, S., K. Howell, R. Drewes, and J. Ashe. A Field Guide to the Reptiles of East Africa. San Diego: Academic Press, 2002.