Linda Benedict | 5/5/2005 7:06:12 PM
Alligator populations in Louisiana have changed drastically during the last century in response to changes in management and in the environment. American alligators are strictly carnivorous reptiles whose native range was restricted to the southeastern part of the United States. They occur in a wide variety of aquatic habitats including rivers, streams, lakes and ponds but are most abundant in swamps and marshes.
Alligators are relatively torpid during the winter, surfacing only to breathe. In late winter and early spring, they will bask in the sun. By late April, they begin to feed vigorously. Mating occurs in April and May, and nest building and egg laying in June and early July. The female builds the nest using vegetation and mud found in the immediate vicinity. The marsh nests contain much vegetation and routinely reach 3 feet in height and 5 feet in diameter. Many nests in the swamps tend to be less bulky and have much mud and a few sticks. The eggs are laid in a hole toward the top of the nest and covered with nesting material. If the nests are flooded for more than 24 hours, the embryos will drown, a common source of nest loss in some years. Predation by mammals such as raccoons is common.
The eggs hatch in August or early September. The young alligators are 9 to 11 inches long and feed on insects and aquatic organisms until early October, when the alligators again become lethargic and cease feeding. Young alligators grow rapidly and may grow a foot during the first year. During their first year, young alligators feed on insects and small aquatic organisms. As they grow larger, they eat more fish along with some snakes and amphibians. When they reach about 6 feet long, they add mammals and birds to the diet, although fish are always an important part. When they are about 6 feet long and 10 to 12 years old, the wild females start to nest. Once the females start to nest, growth slows considerably as energy is diverted to the 20 to 50 eggs laid each year. Few females ever reach 9 feet in length. The males, on the other hand, continue to grow, and 10-foot-long males weighing about 300 pounds are common. Males 11 and 12 feet long are harvested every year. Alligators longer than 13 feet are rare.
During the 1950s and early 1960s, alligators were harvested with no regulations. No records are available on the magnitude of the harvest, but anecdotal reports indicate that it was high, and the populations were depleted. Alligator harvest was banned during the mid and late 1960s but was reopened in 1972 in three parishes in southwestern Louisiana where the Department of Wildlife and Fisheries carefully regulated it. Harvest in this area has continued since then with two exceptions. One year in the early 1970s, there was no harvest because the regulations were slow in getting established. Another year in the early 1980s, there was a glut of alligators on the market. During the last few years, about 30,000 wild alligators have been harvested yearly in Louisiana.
The data available on alligator harvest include the length and sex of each animal harvested since the season was opened in 1972. The number of large animals being harvested has remained reasonably steady, which suggests that the harvest has not been excessive. An even better indicator of the health of the population is an aerial survey to count the nests in the marshes of Louisiana. Louisiana Department of Wildlife and Fisheries personnel use helicopters to count nests soon after the alligators build them.
The density of nests has increased about threefold since the nest surveys began in the early 1970s (Figure 1). This clearly indicates that the number of nesting females has increased; however, we do not know whether the proportion of females that nest each year is a constant. Many alligator specialists believe that a smaller percentage of females will nest during droughts.
During the late 1980s a new management program for alligators was initiated. Eggs are collected from nests found in the wild and then hatched in captivity. The first large-scale collection of eggs was in 1989 when 169,000 were collected. The eggs are then carefully transported to the hatching facility. The transport is critical, because turning the egg over after incubation starts will tear blood vessels and kill the embryo. Incubation occurs in temperature-controlled situations where the eggs and nest material are kept in baskets over warm water.
Research shows that incubation temperature is critical since more than 95 percent of those incubated at 85 degrees F are females, and most of those incubated at 90 degrees F are male. Equal numbers of those hatching at 88.5 degrees F are of each sex. Hatching occurs in 60 to 70 days, and the young are then moved in special temperature-controlled houses for rearing.
These hatchlings are then sold to alligator farmers who raise the young in heated houses until they are about 4 feet long. This takes about 15 months. Some of the alligators are returned to the landowner where the eggs were collected for release into the wild. The rest are sold for meat and hides.
Vernon L. Wright, Professor, School of Renewable Natural Resources, LSU AgCenter, Baton Rouge, La.
(This article appeared in the spring 2002 issue of Louisiana Agriculture.)