Saturday, August 31, 2019
American Alligator Primary Habitats
Alligator mississippiensis is in the family Crocodylidae. This family has existed since the upper Triassic period, but the modern family members appear in the fossil record as little as 80 million years ago. There are three subfamilies, Alligatorinae, Crocodylinae, and Gavaialinae. Some people also include a fourth subfamily, Tomistominae, which contains a single species, the False Gharial. Alligatorinae includes the American and Chinese alligators and the caimans. Crocodylinae includes the crocodiles. Gavaialinae contains the gharials (or gavials). The alligators are unusually tolerant of cold and have been found frozen in ice at the most northern parts of their ranges (Beck). All of the family Crocodylidae is endangered. However, the American alligator has undergone a dramatic population resurgence because of human protection. Restrictions are still in place on capturing alligators from the wild (Beck). Studies have shown that using hormones such as norethindrone can be used to feminize alligator embryos at the male producing temperature (Lance, 79). This could lead to a way to help alligators increase in numbers of both sexes as well as help other members of the family Crocodylidae. Alligators are important ecologically and are dependent on the spatial and temporal patterns of water fluctuations. Patterns of courtship, mating, nesting, and habitat use are all dependent on marsh water levels. Alligators are a great study organism to study the adaptations and responses to the seasonal changes to the hydrological conditions in the everglades. Alligators seem to be able to adjust the height of the nest egg cavity based on the spring water levels, which historically indicated the water levels later in the nesting season. Water levels also determine the availability of food therefore affecting the patterns of growth and survival. Alligators are most abundant in central sloughs, which is probably due to recommendations regarding managing hydrological conditions for alligators focused on maintaining alligators in central slough habitats (Mazzotti, 485). The American alligator is one of the keystone species in the Florida everglades and other marsh systems. It is the only large, abundant, widespread nonmarine carnivore left in the southeastern United States (Mazzotti, 485). They are spread as far west as reserves in Texas, and their northern boundary is in South Carolina. The interesting thing about alligators is the temperature determination of sex. At 29? C all females will be produced. At 32? C all males are produced. Temperatures in-between will produce mixed sets of young. The lower the temperature the less yolk there is for the young, there fore the young turns out smaller and female (Allsteadt, 76). It would be the opposite for warmer temperatures. The female alligator chooses the nest site, which in turn determines the sex of the young. The sex of the young is determined in the first two-thirds of incubation. During the final third of incubation the quality of the young is determined. Snout length, carcass lean dry and lipid mass, and yolk sac lean dry and lipid mass are determined by the final third of the incubation period (Congdon, 497). These characteristics could affect the vitality of the young in competition after they hatch. In South Carolina growth rates of alligators were thought to be slower, but it seems that alligators reach sexual maturity at a later age and larger body size than alligators elsewhere. It is assumed that the delayed breeding of alligators in South Carolina may be related more to social dominance than to growth rates. It is essential that age and size relations need to be understood better if alligators are to be managed effectively (Wilkinson, 397). All alligators, caimans, gavials, and crocodiles are carnivorous. In the wild, each depends upon a somewhat different selection of prey from its local fauna. For captive specimens, diet should vary with the size of the animal and the availability of prey. Small captives will do well on small animals (e. g.. goldfish, insects, or mice. ) As the reptile grows, its diet should change from mice to rats to rabbits, chickens, and other suitable larger prey. It's prudent to supplement meals with added calcium. Reptiles are susceptible to a variety of cutaneous and deep mycotic infections, however relatively few cases are reported in the American alligator. A juvenile alligator in Texas was captured that was covered with a fungus-like material, which was a dermetophillic fungus (Foreyt, 530). This could indicate that alligators are becoming more susceptible to cutaneous infections. Since alligator's sex is determined by temperature there is a problem with primarily one sex being born. This causes a major problem since you have to have both male and female to produce young in alligators. Many surveys of juveniles and adults show a male-biased ratio, although a female-biased ratio exists in Louisiana. From a study of 25 nests with 778 hatchlings a ratio of 1 male to every 3. 8 females was determined (Rhodes, 640). However since sex ratios vary temporally and spatially, long tern studies in representative habitats would be required for adequate ratios. Hypoxic incubated alligator eggs temp to hatch later and produce smaller young. Their hematocrit was significantly higher after hatching. Alligators exposed to 20% Oxygen maintained oxygen consumption relative to their normoxic siblings despite their lower mass (Warburton, 44). Obviously being in hypoxic conditions wouldn't be life threatening to a certain point, but in future competition being smaller than the rest of the alligators is not a good quality. Humans as usual are a threat to any type of wildlife including alligators. Thirty farms in Florida's swampland are currently raising an estimated 100,000 alligators. They sold nearly 26,000 adult skins in 1995. The price for skins has increased 67% since 1993, and 30 % from 1995 to 1996 (Good). With skins being worth more each year, $150. 00 in 1996, more people may decide to take a risk in capturing alligators from the wild to sell skins. This could be detrimental to the wild population of alligators. However in 1998 trappers reported a decline in the demand for alligator skins resulting in a decrease in the price for skins. This helps slow programs where alligators that frighten people are killed (Falling, 6). If skins become popular again programs like these would hurt the population. This program has flaws because most alligators are relatively calm. The psychological orientation of alligators is interesting. It appears that alligators tend to regard humans as animals larger than themselves and thus will not generally attack a human without provocation. However, they will certainly look after their interests, and a small number of accidents have occurred when their predatory or protective instincts were inadvertently triggered. Crocodilians will attack in self-defense, to obtain food, and to protect their young up to two years after birth. Indeed, the outstanding parental care they afford is unique among herps and (along with certain anatomical features) illustrates the close alliance of this family to birds and, ultimately, dinosaurs (Beck).
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