temperatures rose to such extremes? By Alligators from the Par Pond population have human identification at crime scenes. Using these markers to using the combination of external and also been the subjects of contaminant determine paternity in alligators led to the discovery that about internal temperature-sensitive transmitters, studies. Elevated levels of the radioactive one-third of all gator nests contain offspring from multiple researchers learned that alligators element radiocesium (137Cs) occur in some fathers. In addition, although there are many 8-10 ft (2.4-3 m) responded to thermal cues very rapidly, portions of Par Pond as a result of reactor male alligators in the gator population on the SRS, only the few seeking cooler waters in coves, stream operations. Cesium-137 mimics elemental very large males (11+ ft; 3.4+ m) sire offspring. Finally, edges, or on stream bottoms potassium when incorporated microsatellites have been used in investigations of the effects of once their body temper- into plant and animal tissues; contaminants, leading to the discovery that the Hg and low- ature reached about in animals it tends to levels of radioactive contamination in some alligators on the Federal status The American alligator and some crocodile “Threatened due to similarity of 91°F (33°C). concentrate in muscle SRS are not resulting in increased mutation rates relative to species are prime examples of the concept of The American alligator, Alligator mississippiensis, appearance” to other crocodilian tissue. SREL studies gators from other populations. Continuing research will use “sustainable use.” Sustainable use simply means occurs throughout most of the southeastern United States. Alligators species Like many wildlife concluded that al- these genetic markers to make more discoveries about the that an organism is harvested at levels that can were once hunted primarily to produce leather products, which became Size/age at maturity species, alligators though some indiv- biology of alligators, solve other environmental problems, and be continued indefinitely. The specifics of fashionable in the late 1800s. Untold numbers of animals were killed during 6 ft./dependent on growth rates are vulnerable to iduals had elevated even produce a map of the alligator genome. sustainable use programs vary among croco- decades of unregulated hunting. Even after limited protection was put into effect in Typical maximum size environmental con- levels of 137Cs in their dilian species, and among populations within a some areas in the mid-1900s, animals continued to be poached. As a result, alligator numbers species in different parts of its geographic range. males–13 to 14 feet, taminants. Because bodies, there were no Humans and Alligators were dramatically reduced and in some regions it was feared that local populations would go females–9 to 10 feet alligators are top-level detectable effects on For example, the harvesting program for extinct. Federal legislation in the 1970s and 1980s, including the Endangered Species Act of Largest SRS alligator carnivores, they can bio- individual or population The recovery of alligator populations throughout the Southeast, alligators in Florida differs from programs in 1973 and amendments to the Lacey Act in 1981, ensured the alligator’s protection, and eventually its comeback. Today Louisiana and other southeastern states; even 12’10” male that died in 1996 accumulate contaminants health. combined with human population growth and encroachment alligator numbers are estimated in the millions and they are common throughout most of their historic range. populations in different lakes within Florida are Weight in their tissues through the prey on wetland habitats, has increased the likelihood of gator-human managed differently. The numbers of adult varies; adult males can be items they ingest. Some environmental There is, however, reason for concern about interactions. Even so, the fact remains that the probability of an animals that can be killed, as well as the The story of the American alligator, both tragedy and success, is similar 500+ pounds contaminants can be passed from female human consumption of alligators due to a alligator attacking a proportions of eggs and hatchlings that can be to that of many of its close kin, the crocodiles. Worldwide there are 23 Longevity alligators to eggs, potentially adversely much more widely distributed environ- person is extremely removed from the wild, are based on annual species of crocodilians; most were also hunted for food and skins, 40 or more years in the wild, affecting the health of developing offspring. mental contaminant, mercury (Hg). Point- low. The number of population trends. The end result is that the legal, and by 1971 all crocodilians were endangered, threatened, or declining record 66 years in captivity Scientists at SREL are studying maternal source pollution and atmospheric transport alligators throughout regulated harvest of various life stages does not in numbers. Habitat destruction in many countries exacerbated the Home range size transfer of contaminants from females to of this metal have resulted in many wildlife the range at any given harm the population, and gator and croc declines. But a combination of legislation, effective law enforcement, up to 2,000 acres for their offspring. On the SRS, alligators nest species having elevated Hg levels, even in point in time is populations can thrive even as humans use them dedicated conservationists, and innovative sustainable yield harvesting adult males in a swamp downstream from a coal- “pristine” habitats. High Hg levels are probably more than commercially. In fact, many scientists believe that programs reversed the decline for many species, despite continuing some crocodile species would be in far worse Hatchling size burning power plant. The swamp is common in wetland habitats and in top-level three million animals, habitat loss. Since the 1970s 16 of the 23 crocodilian species have shape, and perhaps would have become extinct, contaminated with a variety of potentially predators. Alligators are therefore prime yet on the average there 8 to 10 inches if there were not a sustainable use management increased in population size. However, some species, such as the Clutch size toxic trace elements including arsenic, candidates for exhibiting high Hg are fewer than 10 program for those species. Carefully managed Chinese alligator, remain highly endangered in the wild. 20–60 eggs cadmium, and selenium (Se). Of these concentrations. Mercury levels in the tissues attacks per year. The sustained-yield harvest programs provide direct Incubation period elements, selenium is of great concern of SRS alligators, as well as those from other majority of attacks have economic benefits to local people and The current federal protection status of the alligator remains as “threatened due to similarity of appearance” to endangered approximately 65 days because it readily bioaccumulates and southeastern wetlands, have been analyzed. occurred in Florida, communities, giving everyone an incentive to crocodiles (and products made from their skin). In some states alligators may be harvested using controlled hunts. Alligators are Teeth causes developmental abnormalities when Although there are no national standards for where there have been protect both the species and its habitat. also bred and raised in captivity for the production of meat and skins, but most of the half million farmed alligators are hatched 74 to 80 transferred from females to developing Hg concentrations in reptile meat, if the 11 fatalities during a from eggs collected from the wild. The products from these tightly regulated wild harvests and alligator farms are now sold legally, Name origin embryos. Monitoring efforts in the same standards that are used for fish were 50-year period. Most This brochure was produced by the Savannah River Ecology providing important funds for the conservation of this species and its habitat. Alligator is derived from the contaminated system revealed that adult applied to alligators (1 mg Hg/kg wet weight attacks occur either because alligators have lost their natural Laboratory Environmental Outreach Program, in support of Spanish el lagarto which means female alligators accumulate Se and of tissue), then a high proportion of fear of humans (due to being illegally fed by people and learning Partners in Amphibian and Reptile Conservation (PARC; Alligator Ecology “the lizard”; mississippiensis transfer significant quantities to their eggs. alligators from the Everglades, other areas to associate humans with food) or because they are defending www.parcplace.org). Printing was sponsored by SREL means “of or belonging to the Concentrations of Se in eggs and hatchlings of Florida, and the SRS would be considered a territory. Humans can do several things to minimize the risk (www.uga.edu/srel/), with additional program support from The Habitat Mississippi” collected from the contaminated site are unsafe for human consumption. of attack: Christensen Fund and the Department of Energy. Text by David Alligators live in fresh and brackish water habitats but will venture into salt Ancestry 3-5 times higher than levels from n Do not feed alligators, thereby causing them to become E. Scott, I. Lehr Brisbin, Jr., Travis C. Glenn, and William A. water. Alligators inhabit swamps, tidal marshes, creeks and rivers, canals, ponds, fossil records of crocodilian uncontaminated samples. Fortunately, the SREL scientists are also developing and using accustomed to humans. Hopkins. Photographs by David E. Scott lakes, and reservoirs. In some areas alligators do something that only a few ancestors, archosaurs, are concentrations of Se do not appear high modern analytical and DNA techniques to n Do not swim in areas (especially near heavily vegetated (except as noted). Layout and design by species, such as humans and beavers, do—create wetland habitat. In marsh, Laura L. Janecek. known from 225 million years enough to adversely affect developing learn about alligators and solve environ- shorelines) where large (>6 feet) alligators are present, sawgrass, and floodplain habitats gators sometimes create “gator holes,” which ago; archosaurs are thought to offspring; embryonic development, hatch- mental problems. For example, researchers particularly at night/dusk when they are feeding. provide a refuge for many other animals during dry periods. Alligators create have given rise to dinosaurs ing success, and hatchling size all appear have developed microsatellite DNA loci for n Do not attempt to capture alligators—it is dangerous and the holes, which can be the size of a small backyard pool, using their snout, and birds normal in clutches produced by female alligators, which are the same type of genetic against the law. forefeet, and tail. Alligators are called a “keystone species” due to the strong alligators nesting in the contaminated area. markers used for paternity analyses or n Do not approach an alligator nest or hatchlings. influence they have on other species. Alligator in a gator hole (photo by T.C. Glenn, SREL). The habitat preferences of alligators depend After mating, females construct shoreline wide variety of animals, including large Range of the American alligator. to communicate, from reproductive synchronization with females SREL scientists found somewhat on the size, age, and sex of the mound nests made from vegetation, leaf wading birds, snakes, bass, and even coughing and hissing to that remained in the cooler parts of the themselves in a unique gator. Large adult male alligators generally litter, and mud. In June and July females bullfrogs. distress yelps, hatching reservoir and entered typical winter position in 1991, when prefer deep, open water during the entire lay 20-60 eggs in the nest and calls, and bellowing. In dormancy. Researchers speculated that the Par Pond was lowered active season. Large females also are found cover them with additional Feeding habits addition, alligators are altered male activity cycle may have caused approximately 18 ft (5.5 in open water during the breeding season, vegetation and debris. The diet of alligators is one of many species of a change in the timing of male repro- m) while repairs were but then move to marshes and lake edges The temperature of the quite varied, and is animals that commun- duction, and made males incapable of made to the dam. during the nesting season and after young nest during the dependent upon the icate using sounds that breeding by the time females became active Radiotracking studies have hatched. Smaller alligators (4-5 ft/1.2- middle third of the size of the gator. All we cannot hear. and ready to breed in the spring. Indeed, during the 3-year period 1.5 m or less) typically occur in wetlands incubation period gators, regardless of Humans hear sound in the early gator population at Par Pond had of low water level with relatively dense vegetation, which determines the sex size, are primarily the range of 20-20,000 an unusually high proportion of adults showed that breeding provides both a hiding place and good of the hatchlings. carnivores, although temperature, food resources of the habitat, and the animal’s sex, size, Hz (hertz; cycles per (64%) and few juveniles, the pattern one females remained in the habitat for prey items. Constant incubation some plant material and age. For example, juvenile alligators in some South Carolina second), and some might expect if females were not nesting lowered reservoir and temperatures below may incidentally be populations average 7.5” (19 cm) of growth per year, while those in alligator vocalizations An alligator exhibiting “icing” behavoir. and producing young. However, the same continued to nest successfully. However, and body temperature were determined. Reproduction, nesting, & hatching 87.8oF (31oC) during ingested. Hatchlings Louisiana may grow 12” (30.5 cm) per year. Because maturity is related are below 20 Hz, in the infrasound range. Low frequency sound pattern might occur if males are more survival of young from these nests was Using these methods researchers studied The time it takes for alligators to become this period produce and young alligators eat to body size, this means that alligators in Louisiana may reach maturity can travel very long distances. likely than females to colonize new aquatic extremely low because the draw-down the body temperature and behavior H . a m mature, and thus able to reproduce, varies only females, temper- tch o insects, crayfish, snails and earlier than those in South Carolina. As alligators get larger their growth n Researchers who have used radiotransmitters to track alligators habitats, resulting in a male-biased sex had denuded the reservoir shoreline of relationships of larger alligators as they lin n M g g de o from population to population. Repro- atures between 90.5 and ator hitching a ri other invertebrates, small fish, rate slows, and once an alligator becomes reproductively mature its have learned that they have large home range sizes, with males ratio with few adult females available for much of the emergent aquatic vegetation faced cold weather in unheated reservoirs. ductive maturity in alligators is primarily 91.4oF (32.5-33oC) produce only and amphibians. At 5-6 ft long (1.5- growth rate drops dramatically. Male alligators grow faster and larger using a larger area than females. Males move the most and have breeding. In 1974 there were 3.2 male that newly hatched alligators need for related to body size, so the age at which an males, and temperatures above 93.2oF 1.8 m) alligators begin to feed more on than females. Females can attain approximately 9 ft (2.7 m) in length their largest home ranges during the breeding season, and females alligators for every female, and only an protection from predators. Some adult Similar techniques were used in other individual can breed depends on how fast (34oC) produce a high proportion of large fish, turtles, snakes, waterfowl and and 200+ lbs (91 kg). Males can grow to 13+ ft (4 m) and 500+ lbs move the least and have their smallest ranges during the nesting estimated 15 females in all of Par Pond. alligators, primarily males, moved from studies of the effects of thermal effluent it grows throughout its life. Both males and females. It generally takes a little more wading birds, and small mammals. In (227 kg). The record alligator, taken on Marsh Island, Louisiana, was season. Alligator home range size depends on many factors, Multiple possible causes for a single Par Pond to nearby bodies of water. L- from reactors. In addition to cooling females tend to mature at about 6 feet (1.8 than two months for the embryos to addition to keen eyesight, hundreds of reported to be 19’2” long. including the location and type of habitat, but an adult male alligator observed pattern illustrates why science Lake, a new reservoir constructed in late reservoirs, three SRS streams received m) in length, but the size at which an develop and for hatchlings to emerge from specialized pressure sensors on the snouts may have a home range of more than 1,000 acres. can be so challenging! 1985, is approximately 4 miles (6.4 km) thermal effluent during periods of reactor alligator may successfully breed is also the eggs. Eggs in alligator nests are often of gators help them locate prey in the water; Interesting behaviors n Unique among reptiles, crocodilians have been observed bringing from Par Pond. By 1988 alligators had operation. In the 1980s SREL researchers dependent upon social interactions among preyed upon by raccoons, opossums, these bumps are sensitive enough to detect For an animal with a maximum brain mass of less than ½ ounce (~10.5 food to their young. By the mid-1980s the Par Pond alligator not colonized the reservoir, but in the examined how hot water plumes in SRS members of the population. The courtship skunks, pigs, and other nest predators. ripples from a single drop of water. Because grams), alligators demonstrate some interesting behaviors. population had nearly doubled from 1974 1990s alligators began to take up streams affected alligators. At the time, n and breeding season for alligators is For example, in Florida it is considered alligators are “cold blooded” their feeding In the temperate portions of their range, alligators construct dens Alligator Research at SREL estimates, to a total of almost 200 adults residence in the new lake, although none alligators were still a federally listed generally from April through May, although “normal” if only 50% of the eggs escape activity is dependent on water temper- (a cave-like structure in the bank of the waterway) where they and juveniles (42%), with 24 adult females. were identified as known Par Pond endangered species in inland South there are some reports of autumn mating. predation and hatch. At hatching time the ature—gators will usually stop feeding if remain dormant during winter months. Gators also exhibit “icing The University of Georgia’s Savannah River Ecology Laboratory (SREL) animals. Researchers continue to study Carolina, and the impact of hot water on Breeding occurs in open water. Body babies make a call that attracts the female. water temperatures are below approxi- behavior” in response to extreme cold. Before a pond freezes, an began conducting ecological studies on the newly created Savannah the colonization of L-Lake by alligators, alligators was of concern to the Department posturing, snout rubbing, water slapping, She uncovers the hatchlings in the nest by mately 70oF (21oC). Thus, alligators adult will move to shallow water, place its nostrils (on the tip of River Site (SRS) on the upper Coastal Plain of South Carolina in 1951. which had reached a population size of of Energy. Researchers had already and bellowing are all part of the courtship digging with her front feet and snout and generally feed from late March/early April the snout) out of the water, and let its snout become frozen into Studies of the American alligator on the SRS have increased our several dozen (mostly adults) by the late determined that the critical thermal process. may carry hatchlings in her mouth from through October. the ice. Hatchlings and juveniles may not be as successful at this, knowledge about its basic ecology and provided insights on the effects 1990s. maximum (CTM), or the temperature at the nest to the water’s edge. which may explain (in part) the limits to the range of the alligator. of industrial facilities on alligators. SREL’s ongoing research, in which alligators would overheat and die, Growth & body size n Humans can hear a wide variety of the sounds that alligators use collaboration with researchers from around the world, continues to SREL biologists have also used the was 100°F (38°C). Temperatures in parts Most reptile species do very little Growth rates in young alligators vary from lead to new discoveries about alligators and other crocodilians. technique of radiotelemetry to learn of some SRS streams exceeded 104°F “parenting,” especially after the eggs have 4-14” (10-36 cm) per year, depending on about alligator physiology. Radio- (40°C) when reactors were operating. How hatched. In contrast, female The SREL program of alligator research began in the late 1960s when transmitters can be designed so that the did alligators respond when water alligators will protect babies nuclear production reactors were periodically discharging heated pulse rate of the radio signal is at all stages: eggs in the effluents into cooling reservoirs and streams on the SRS. The heated dependent on temperature, simply nest, hatchlings, and babies waters created unique gradients of water temperature never before meaning that the sound a biologist up to three years old. experienced by alligators. As one example of a “thermal effect,” alligators hears when tracking the animal is Hatchling gators generally that inhabited the warm portions of the 2,840 acre (1,150 hectare) slower when cold and faster when stay together in a “pod” for Par Pond reservoir were noted to bask less frequently, especially during warm. In the case of a large alligator, 1-3 years, and make a call cooler months, than gators in normal-temperature water. Research over researchers attached one trans- (presumably a distress call) the next decade documented the seasonal use of heated waters, The American alligator (top) and American mitter on a collar to the outside of crocodile (right) are native to the U.S. The spectacled to which females respond. particularly by larger males that moved into the warm waters and caiman (lower left) is established in parts of south the animal, and inserted one Nonetheless, many hatch- remained active during the winter months of the year. The prolonged Florida. Species are distinguished primarily by transmitter into the stomach, so that lings are preyed upon by a active season of these larger male alligators seemed to put them out of location (range and habitat), head shape, and teeth. both the environmental temperature The habitat preferences of alligators depend After mating, females construct shoreline wide variety of animals, including large Range of the American alligator. to communicate, from reproductive synchronization with females SREL scientists found somewhat on the size, age, and sex of the mound nests made from vegetation, leaf wading birds, snakes, bass, and even coughing and hissing to that remained in the cooler parts of the themselves in a unique gator. Large adult male alligators generally litter, and mud. In June and July females bullfrogs. distress yelps, hatching reservoir and entered typical winter position in 1991, when prefer deep, open water during the entire lay 20-60 eggs in the nest and calls, and bellowing. In dormancy. Researchers speculated that the Par Pond was lowered active season. Large females also are found cover them with additional Feeding habits addition, alligators are altered male activity cycle may have caused approximately 18 ft (5.5 in open water during the breeding season, vegetation and debris. The diet of alligators is one of many species of a change in the timing of male repro- m) while repairs were but then move to marshes and lake edges The temperature of the quite varied, and is animals that commun- duction, and made males incapable of made to the dam. during the nesting season and after young nest during the dependent upon the icate using sounds that breeding by the time females became active Radiotracking studies have hatched. Smaller alligators (4-5 ft/1.2- middle third of the size of the gator. All we cannot hear. and ready to breed in the spring. Indeed, during the 3-year period 1.5 m or less) typically occur in wetlands incubation period gators, regardless of Humans hear sound in the early gator population at Par Pond had of low water level with relatively dense vegetation, which determines the sex size, are primarily the range of 20-20,000 an unusually high proportion of adults showed that breeding provides both a hiding place and good of the hatchlings. carnivores, although temperature, food resources of the habitat, and the animal’s sex, size, Hz (hertz; cycles per (64%) and few juveniles, the pattern one females remained in the habitat for prey items. Constant incubation some plant material and age. For example, juvenile alligators in some South Carolina second), and some might expect if females were not nesting lowered reservoir and temperatures below may incidentally be populations average 7.5” (19 cm) of growth per year, while those in alligator vocalizations An alligator exhibiting “icing” behavoir. and producing young. However, the same continued to nest successfully. However, and body temperature were determined. Reproduction, nesting, & hatching 87.8oF (31oC) during ingested. Hatchlings Louisiana may grow 12” (30.5 cm) per year. Because maturity is related are below 20 Hz, in the infrasound range. Low frequency sound pattern might occur if males are more survival of young from these nests was Using these methods researchers studied The time it takes for alligators to become this period produce and young alligators eat to body size, this means that alligators in Louisiana may reach maturity can travel very long distances. likely than females to colonize new aquatic extremely low because the draw-down the body temperature and behavior H . a m mature, and thus able to reproduce, varies only females, temper- tch o insects, crayfish, snails and earlier than those in South Carolina. As alligators get larger their growth n Researchers who have used radiotransmitters to track alligators habitats, resulting in a male-biased sex had denuded the reservoir shoreline of relationships of larger alligators as they lin n M g g de o from population to population. Repro- atures between 90.5 and ator hitching a ri other invertebrates, small fish, rate slows, and once an alligator becomes reproductively mature its have learned that they have large home range sizes, with males ratio with few adult females available for much of the emergent aquatic vegetation faced cold weather in unheated reservoirs. ductive maturity in alligators is primarily 91.4oF (32.5-33oC) produce only and amphibians. At 5-6 ft long (1.5- growth rate drops dramatically. Male alligators grow faster and larger using a larger area than females. Males move the most and have breeding. In 1974 there were 3.2 male that newly hatched alligators need for related to body size, so the age at which an males, and temperatures above 93.2oF 1.8 m) alligators begin to feed more on than females. Females can attain approximately 9 ft (2.7 m) in length their largest home ranges during the breeding season, and females alligators for every female, and only an protection from predators. Some adult Similar techniques were used in other individual can breed depends on how fast (34oC) produce a high proportion of large fish, turtles, snakes, waterfowl and and 200+ lbs (91 kg). Males can grow to 13+ ft (4 m) and 500+ lbs move the least and have their smallest ranges during the nesting estimated 15 females in all of Par Pond. alligators, primarily males, moved from studies of the effects of thermal effluent it grows throughout its life. Both males and females. It generally takes a little more wading birds, and small mammals. In (227 kg). The record alligator, taken on Marsh Island, Louisiana, was season. Alligator home range size depends on many factors, Multiple possible causes for a single Par Pond to nearby bodies of water. L- from reactors. In addition to cooling females tend to mature at about 6 feet (1.8 than two months for the embryos to addition to keen eyesight, hundreds of reported to be 19’2” long. including the location and type of habitat, but an adult male alligator observed pattern illustrates why science Lake, a new reservoir constructed in late reservoirs, three SRS streams received m) in length, but the size at which an develop and for hatchlings to emerge from specialized pressure sensors on the snouts may have a home range of more than 1,000 acres. can be so challenging! 1985, is approximately 4 miles (6.4 km) thermal effluent during periods of reactor alligator may successfully breed is also the eggs. Eggs in alligator nests are often of gators help them locate prey in the water; Interesting behaviors n Unique among reptiles, crocodilians have been observed bringing from Par Pond. By 1988 alligators had operation. In the 1980s SREL researchers dependent upon social interactions among preyed upon by raccoons, opossums, these bumps are sensitive enough to detect For an animal with a maximum brain mass of less than ½ ounce (~10.5 food to their young. By the mid-1980s the Par Pond alligator not colonized the reservoir, but in the examined how hot water plumes in SRS members of the population. The courtship skunks, pigs, and other nest predators. ripples from a single drop of water. Because grams), alligators demonstrate some interesting behaviors. population had nearly doubled from 1974 1990s alligators began to take up streams affected alligators. At the time, n and breeding season for alligators is For example, in Florida it is considered alligators are “cold blooded” their feeding In the temperate portions of their range, alligators construct dens Alligator Research at SREL estimates, to a total of almost 200 adults residence in the new lake, although none alligators were still a federally listed generally from April through May, although “normal” if only 50% of the eggs escape activity is dependent on water temper- (a cave-like structure in the bank of the waterway) where they and juveniles (42%), with 24 adult females. were identified as known Par Pond endangered species in inland South there are some reports of autumn mating. predation and hatch. At hatching time the ature—gators will usually stop feeding if remain dormant during winter months. Gators also exhibit “icing The University of Georgia’s Savannah River Ecology Laboratory (SREL) animals. Researchers continue to study Carolina, and the impact of hot water on Breeding occurs in open water. Body babies make a call that attracts the female. water temperatures are below approxi- behavior” in response to extreme cold. Before a pond freezes, an began conducting ecological studies on the newly created Savannah the colonization of L-Lake by alligators, alligators was of concern to the Department posturing, snout rubbing, water slapping, She uncovers the hatchlings in the nest by mately 70oF (21oC). Thus, alligators adult will move to shallow water, place its nostrils (on the tip of River Site (SRS) on the upper Coastal Plain of South Carolina in 1951. which had reached a population size of of Energy. Researchers had already and bellowing are all part of the courtship digging with her front feet and snout and generally feed from late March/early April the snout) out of the water, and let its snout become frozen into Studies of the American alligator on the SRS have increased our several dozen (mostly adults) by the late determined that the critical thermal process. may carry hatchlings in her mouth from through October. the ice. Hatchlings and juveniles may not be as successful at this, knowledge about its basic ecology and provided insights on the effects 1990s. maximum (CTM), or the temperature at the nest to the water’s edge. which may explain (in part) the limits to the range of the alligator. of industrial facilities on alligators. SREL’s ongoing research, in which alligators would overheat and die, Growth & body size n Humans can hear a wide variety of the sounds that alligators use collaboration with researchers from around the world, continues to SREL biologists have also used the was 100°F (38°C). Temperatures in parts Most reptile species do very little Growth rates in young alligators vary from lead to new discoveries about alligators and other crocodilians. technique of radiotelemetry to learn of some SRS streams exceeded 104°F “parenting,” especially after the eggs have 4-14” (10-36 cm) per year, depending on about alligator physiology. Radio- (40°C) when reactors were operating. How hatched. In contrast, female The SREL program of alligator research began in the late 1960s when transmitters can be designed so that the did alligators respond when water alligators will protect babies nuclear production reactors were periodically discharging heated pulse rate of the radio signal is at all stages: eggs in the effluents into cooling reservoirs and streams on the SRS. The heated dependent on temperature, simply nest, hatchlings, and babies waters created unique gradients of water temperature never before meaning that the sound a biologist up to three years old. experienced by alligators. As one example of a “thermal effect,” alligators hears when tracking the animal is Hatchling gators generally that inhabited the warm portions of the 2,840 acre (1,150 hectare) slower when cold and faster when stay together in a “pod” for Par Pond reservoir were noted to bask less frequently, especially during warm. In the case of a large alligator, 1-3 years, and make a call cooler months, than gators in normal-temperature water. Research over researchers attached one trans- (presumably a distress call) the next decade documented the seasonal use of heated waters, The American alligator (top) and American mitter on a collar to the outside of crocodile (right) are native to the U.S. The spectacled to which females respond. particularly by larger males that moved into the warm waters and caiman (lower left) is established in parts of south the animal, and inserted one Nonetheless, many hatch- remained active during the winter months of the year. The prolonged Florida. Species are distinguished primarily by transmitter into the stomach, so that lings are preyed upon by a active season of these larger male alligators seemed to put them out of location (range and habitat), head shape, and teeth. both the environmental temperature