The elephant is largest land living mammal, which a long time ago they roamed every landmass except Australia and Antarctica. Two extant species, the Indian elephant, of India and Southeast Asia, and the African elephant, ranging south of the Sahara, are now limited to tropical forests, savannas, deserts, and river valleys. The Indian elephant reaches heights of 10 ft tall and the African elephant, 13 ft tall.
The boneless, muscular trunk, is the most distinctive feature of elephants, is actually a greatly elongated upper lip and nose used to convey grasses, leaves, and water to the mouth. Present-day elephants consume as much as 495 pounds of forage a day in this manner and drink as much as 50 gallons of water, drawing it through their nostrils and squirting it into the mouth. The trunk is also used to trumpet calls, pull down trees, rip off foliage, and draw up dust for dust bathing. It is also a highly sensitive organ, which the animals raise into the air to detect wind-borne scents. By means of fingerlike lobes on the end of the trunk and by the sucking action of the two nostrils, elephants can pick up and examine small objects.
The tusks, which are deeply embedded in the skull, are actually enormously enlarged incisors. Record tusks of the male African elephant have measured 10.5 ft long. Elephants have only four molar or grinding teeth, one to each side of the upper and lower jaws; each is a massive plate about about 12 inches long and 4 inches wide. When worn down by the coarse vegetation that elephants eat, these teeth are replaced by larger ones that shift forward from the rear of the jaws. At about 40 years of age, the animal’s fina and largest molars come into position and last for about 20 years. Elephants’ longevity is comparable to that of humans.
The African elephant can be quickly distinguished from the Indian elephant by its greater size and its larger ears, which may reach a length of about 5 ft from top to bottom. The African elephant is tallest at the shoulder, has more wrinkled skin, and bears tusks in both male and female. The Indian elephant is tallest at the arch of the back, bears tusks in the male only, and has one lobe instead of two on its trunk.
Despite their great weight, which in African elephants reaches 15,400 pounds and in Indian elephants reaches 11,000 pounds, elephants walk almost noiselessly and with exceptional grace, their columnar legs keeping their bulk moving forward in smooth, rhythmic strides. A thick cushion of resilient tissue grows on the base of the foot, absorbing the shock of the weight and enabling the animal to walk high on its hooflike toes. Elephants normally walk about about 4 mph and can charge at up to 25 mph.
The great ears of the African elephant are probably used for ventilation and visual communication as well as for hearing. The eyesight is poor, the eyes being comparatively small and fixed on the animal’s large and relatively immobile head. The most sensitive organ is the trunk, which is frequently at work, picking up scents of food and danger from the ground and the air. Observers first noted in the 1980s that elephants produce, with their nasal passages, rumbling sounds below the range of human hearing. Because such sounds travel well and because elephant hearing is better at low frequencies, the animals very likely use these sounds to communicate with one another over longdistances.
Elephants are gregarious and keenly sensitive to one another’s calls and movements. They associate in herds of 15 to 30 or more usually related members led by an old female, called a matriarch. Herds of Indian elephants are usually made up of females, immature elephants, and one old bull; those of African elephants may also include mature bulls. Bulls driven from herds live alone or in bachelor herds. Elephants commonly feed in the morning, evening, and at night and rest during the middle of the day. When migrating, they often trek single file.
The Atlantic Green Turtle (Chelonia mydas)
The following is based on information from the Recovery Plan for U.S. Population of Atlantic Green Turtles, U.S Fish and Wildlife Service and National Marine Fisheries Service, 1991. Obtained from the U.S. National Marine Fisheries Service, and used with their kind permission.
The green turtle is listed as endangered by the International Union for the Conservation of Nature. Under the U.S. Endangered Species Act of 1973, the green turtle was listed as threatened except for the breeding populations in Florida and on the Pacific coast of Mexico, where it is listed as Endangered.
Green turtles continue to be heavily exploited by humans, and the destruction and loss of nesting and foraging sites is a serious problem. Humans have already caused the extinction of large green turtle populations, including those that once nested in Bermuda and Cayman Islands. The status of green turtle populations is difficult to determine because of our lack of knowledge about their life cycles. The number of nests deposited in Florida appears to be increasing, but we don’t know whether this is due to an increase in the number of nests or because we have started to monitor nesting beaches more closely.
The green sea turtle is the largest hard-shelled sea turtle. Adults of this species commonly reach 100 cm in carapace length and 150 kg in mass. The average size of a female nesting in Florida is 101.5 cm
straight carapace length, with an average body mass of 136 kg.
Hatchling green turtles weigh about 25 g (about a handful of Smarties) and have a carapace about 50 mm long. Hatchlings are black on top and white underneath. The plastron of Atlantic green turtles remains a yellowish white throughout life, but the carapace changes colour from black to various shades of gray, green, brown and black, forming swirls and irregular patterns on their shells.
Growth rates of pelagic-stage green turtles have not been measured under natural conditions; however, growth rates of green turtles have been measured at their feeding grounds. Green turtles grow slowly.
In the southern Bahamas, green turtles grew from 30 to 75 cm in 17 years, and according to Bjorndal and Bolten, growth rate decreased with increasing carapace length. Growth rates measured in green turtles from Florida and Puerto Rico fall within the range of growth rates measured in the southern Bahamas. Based on growth rate studies of wild green turtles, the researchers Balazs, Frazer and Ehrhart estimate the age at sexual maturity range anywhere from 20 to 50 years.
Green turtles occupy three habitat types:
• High-energy oceanic beaches.
• Convergence zones in the pelagic habitat.
• Benthic feeding grounds in relatively shallow, protected waters.
Females deposit egg clutches on high energy beaches, usually on islands, where a deep nest cavity can be dug above the high water line. Hatchlings leave the beach and apparently move into convergence zones in the open ocean where they spend an undetermined length of time (Carr, 1986). When turtles reach a carapace length of approximately 20 to 25 cm, they leave the pelagic habitat and enter benthic feeding grounds. Most commonly these foraging habitats are pastures of seagrasses and/or algae, but small green turtles can also be found over coral reefs, worm reefs and rocky bottoms. Some feeding areas, such as Miskito Cays, Nicaragua, support a complete size range of green turtles from 20 cm to breeding adults. Coral reefs or rocky outcrops near feeding pastures are often used as resting areas, both at night and during the day.
Scientists assume that post-hatchling, pelagic-stage green turtles are omnivorous, but there are no data on diet from this age class. Our personal experience with a juvenile Hawaiian green confirms this theory. Our first turtle encounter resulted when a juvenile swam up to us and attempted to take some of the cuttlefish we were using to attract eels for photographic purposes.
Scientists do know that once green turtles shift to benthic feeding grounds, they are herbivores. They feed on both seagrasses and algae.
Population Distribution and Size
The green turtle can be found throughout the world in all tropical and sub-tropical oceans. In the U.S., Atlantic green turtles can be found around the U.S. Virgin Islands, Puerto Rico, and continental U.S. from Texas to Massachusetts. Important feeding areas for green turtles in Florida include Indian River Lagoon, Florida Keys, Florida Bay, Homosassa, Crystal River and Cedar Key.
Major green nesting colonies in the Atlantic are located on Ascension Island, Aves Island, Costa Rica and Suriname. In the U.S., green turtles nest in small numbers in the United States Virgin Islands, and in Puerto Rico. Greens nest in larger numbers in Florida but actual data is presently not helpful in assessing trends in nesting.