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Corresponding author: Ricky L. Langley, MD, MPH, North Carolina Department of Health and Human Services, 1912 Mail Service Center, Raleigh, NC 27699-1912
Severe injuries and fatalities can occur from an alligator attack. Encounters with alligators appear to be increasing in the United States. This review provides information from alligator attacks reported in the United States as well as infections that may occur after an alligator bite.
Methods
Telephone interviews were conducted with state wildlife offices in all Southern states in order to collect information on the number of alligator bites, nuisance calls, and the estimated alligator population of each state. Detailed information from alligator attacks in Florida is presented, including basic demographic information on the victims and description of the types of injuries and the activity of the victim at the time of injury. Additional information regarding the size and behavior of the alligator involved in the attack is also provided in many cases.
Results
There have been 567 reports of adverse encounters with alligators with 24 deaths reported in the United States from 1928 to January 1, 2009. In addition, thousands of nuisance calls are made yearly and the number of nuisance calls as well as the alligator population is increasing in many states.
Conclusions
Injuries from encounters with alligators may range from minor scratches and punctures to amputations and death. The larger the alligator, the more likely that serious injury will occur. As the human population encroaches on the habitat of the alligator, attacks and nuisance complaints will continue to occur. A uniform reporting system among states should be developed to obtain more complete information on alligator encounters. Guidelines have been developed by many state wildlife officials to reduce adverse encounters with alligators.
In the United States at least 3 species (2 native, 1 nonnative) of crocodilians may be found. The American alligator (Alligator mississippiensis) is the most common of the 2 crocodilians native to the United States and is 1 of 23 crocodilian species in the world.
in: Prevention and Control of Wildlife Damage. Cooperative Extension Division, Institute of Agricultural and Natural Resources, University of Nebraska–Lincoln,
Lincoln, NE1994: F1-F6
It is found in most Southern States, while the American crocodile (Crocodylus acutus) is found only in the southern region of Florida. The third species that has become established in southern Florida is the nonnative caiman (Caiman crocidilus)
In the United States, alligators can be found in the following states: Florida, Georgia, South Carolina, North Carolina, Louisiana, Alabama, Arkansas, Mississippi, Texas, Oklahoma, and probably Tennessee. Occasional sightings in other states have been reported, but these are felt to be pets that have been released or occasional visitors to rivers in states bordering states where alligators are indigenous. Alligators are ectothermic and they become dormant at temperatures below 55°F (13°C), which limits their northern range.
in: Prevention and Control of Wildlife Damage. Cooperative Extension Division, Institute of Agricultural and Natural Resources, University of Nebraska–Lincoln,
Lincoln, NE1994: F1-F6
The population of alligators in the Southern United States is increasing as evidenced by the alligator being removed from the endangered species list in 1987.
Alligators are also being farmed in some states, and their hide and meat are sold in commercial trade. As more people are moving to coastal areas in the Southern United States, the interaction between people and alligators has increased, as has the number of nuisance complaints about alligators.
There is no documented report of a wild crocodile or caiman attack on humans in the United States. This study will update the few reviews of alligator attacks on humans in the United States.
Officials with Divisions of Environment(al) and Natural Resources or Fisheries and Wildlife from each of the 12 states noted above were contacted by telephone and asked the following questions: How many cases of alligator attacks on humans were they aware of in their state? How many nuisance alligator complaints do they receive annually? What is the estimated alligator population in their state? Reports of alligator bites from previous surveys
International Shark Attack File (ISAF) A Comparison of shark attacks and fatalities with the American alligator (Alligator mississippiensis) attacks and fatalities in the U.S.: 1948-2005.
were also evaluated for additional cases of bites or attacks that current state officials may not be aware of as different personnel may currently be responsible for handling alligator complaints. The Florida Fish and Wildlife Conservation Commission provided a detailed spreadsheet on alligator encounters reported since 1928 (written communication with Blair Hayman and Alan Woodward, Florida Fish and Wildlife Conservation Commission, January 16 and August 14, 2009).
An adverse encounter with an alligator, whether provoked or unprovoked, is defined as a bite, scratch, or scrape onto a person or item of clothing or gear worn by a person. Basic demographic information on the victims injured in Florida obtained by the investigating wildlife officer included race, sex, age, month of injury, and time of day injured, location where attack occurred, and use of drugs/alcohol by the victim. Additional information gathered about the alligator and circumstances surrounding the attack included the following: length and weight of alligator (measured or estimated); the sex of the alligator (as determined by the investigating Wildlife officer or trapper); the behavior of the alligator assessed by a Florida Fish and Wildlife Commission biologist; whether alligators were known to have been in the area of attack; whether dogs were present at locality at time of attack; whether the alligator was observed by victim or witnesses prior to or during the attack; human activity at the time of injury; whether the incident was provoked; and the behavior of the attacking alligator categorized by witnesses or reporters immediately prior to attack. In cases where the alligator was not observed, the investigating officer evaluated the victim's statements, and whether the wound was consistent with an alligator-associated injury.
Various information collected on the victims' injuries included information on the bite type (provoked or not), physical location of the first and subsequent bites on the victim, part of the body bitten, type of injury sustained, and severity of the injury.
Results
As of January 1, 2009 there have been 567 cases reported by individuals of adverse encounters with alligators. There have been 529 total events resulting in injury (24 fatal [4.5%] and 505 nonfatal [95.5%]) reported by various sources to have occurred in the United States from 1928 to December 31, 2008 (Table 1). No documented cases of injuries from caimans or crocodiles in their-free ranging habitat have been reported in the United States.
Table 1Adverse alligator encounters reported in the United States
Thirteen other cases in Florida involved individuals who may have had postmortem alligator-related injuries or body parts found but cause of death uncertain.
∼16 000
≥1.25 million
Texas
17 (no fatalities)
450
300 000–400 000
Georgia
10 (2 fatalities)
450
200 000–225 000
South Carolina
10 (no fatalities)
700
>100 000
Alabama
5 (no ratalities)
300
20 000–30 000
Louisiana
3 (no fatalities)
2000–2500
1–2 million
North Carolina
2 (no fatalities)
20 permits to relocate
Low thousands
Arkansas
1 (no fatalities)
70
3000–4000
Oklahoma
0 (no fatalities)
4-6
50-100
Mississippi
1 (no fatalities)
250-350
> 40 000
Tennessee
0 (no fatalities)
0
<10
Thirteen other cases in Florida involved individuals who may have had postmortem alligator-related injuries or body parts found but cause of death uncertain.
Of the 567 encounters that have been reported, the data from Florida were the most thoroughly documented. There have been 518 encounters with alligators reported in Florida. Twenty-three of these reports from Florida did not involve an injury to humans. In some cases the investigating officer did not feel the injury reported was consistent with an alligator bite or the alligator bit or bumped into an occupied boat, but no human injury was reported. In 13 additional cases, the status of the victim appeared to be a postmortem alligator bite or was classified as unknown cause of fatality, and 1 case was pending a final disposition.
The analysis that follows relates to the 481 cases in the Florida database. The average age of the alligator bite victims was 35.1 years. The demographics of the victims were as follows: 62 (13.1%) were children (0–12 years); 40 (8.4%) were teenagers (13–17 years); 372 (78.58%) were adults (18 and older). Data regarding sex of victims indicated that injuries were inflicted on 411 males (85.4%) and 70 females (14.6%). The average age of the victims by sex was 35.0 years and 35.6 years for males and females, respectively. Victims ranged in age from 2 to 83 years. By race where reported, 420 (95.8%) were Caucasians; 7 (1.6%) Black; 4 (0.9%) Hispanic; 2 (0.45%) Native American; 2 (0.45%) other; 3 (0.69%) unknown. In 42 cases, race was not reported.
Most of the injuries were due to a single bite in 370 (81%) victims. The site of the initial bite by the alligator is shown in Table 2. In 76 cases a second bite was reported (majority on the arm) and in 16 cases a third bite occurred, again most often on the arm. No information was available for 58 cases.
The injury severity was classified as high (life or limb threatened) in 57 (11.8%) cases, medium (required medical treatment, surgery, staples, extensive bandaging, or hospitalization) in 225 (46.7%) cases, and low (superficial injury requiring no medical treatment except for light dressing and antibiotics) in 187 (38.9%) cases. No bodily injury was reported in 11 (2.3%) cases (included cases where only clothing or gear was bitten), and unknown in 2 (0.4%) cases.
Alligator bites have been associated with various types of injuries, including lacerations, punctures, abrasions, contusions, fractures, and amputations (Table 3). In many cases, there were multiple injuries to the victim, especially combinations of punctures and lacerations. Miscellaneous injuries reported included traumatic loss of teeth, liver laceration, shredded muscles, massive head/face injury, and partial loss of functional use of the hand.
Table 3Description of injury caused by alligator bite
Activities at the time of the attack were varied. Table 4 provides information on the various activities victims were involved in when attacked. Examples of ”Other” activities included hunting, feeding fish/ducks/alligators, fell off dock, working or splashing in water, rafting, stepped on alligator, and washing hands in water.
Table 4Activity at time of encounter with alligator
The location of the victim immediately prior to the attack was categorized as follows: being in deep water (>1 m deep) in 128 cases; shallow water in 96 cases; on land >1 m from water in 81 cases; on land but at the edge (<1 meter from water) in 68 cases; dangling body part from boat, dock or bulkhead in 20 cases; in water but depth not reported in 8 cases; and unknown in 6 cases.
The time of attack of the cases in Florida was classified as follows: 189 attacks from 12:01 pm to 6:00 pm.; 75 attacks from 5:01 am to noon; 78 attacks from 6:01 pm to 9.00 pm; and 44 attacks from 9:01 pm to 5:00 am. An additional 4 cases were reported to have occurred during daylight hours, 3 cases after sunset and before total darkness, and 5 were unknown. Most attacks occurred between May and August (Figure 3) and in the afternoon hours when tourists are more likely to be outdoors.
In regards to size, the length was measured (202 cases) or estimated (229 cases) or method not reported (2 cases) in 433 cases. In 85 cases the length was not reported. The alligators ranged from less than 1 foot to slightly over 12 feet in length (<0.3–3.66 m) as determined by the investigating officer or nuisance trapper that removed the suspect alligator (written communication with Alan Woodward, Florida Fish and Wildlife Conservation Commission, August 14, 2009). Of 433 alligator lengths obtained, 251 alligators were greater than 6 feet (>1.83 m) in length (52 of which were >10 feet [3.048 m]), while 182 were less than 6 feet (<1.83 m) in length. The weight of the alligator was determined in 74 cases and ranged from 2 pounds to 520 pounds. By weight, 47 were 200–300 pounds, 21 were 301–400 pounds, and 9 were >400 pounds. By sex, 123 were determined to be male and 43 female alligators.
Of the attacks, 167 (33.0%) were felt to have been provoked. These included cases where the victim was handling the alligator or trying to rescue another human or animal victim. In an additional 62 (12.2%) cases, the provocation was unintentional such as the victim inadvertently bumping into the alligator and the alligator reacted by biting the victim. In 276 (54.8%) cases, the alligator attack was felt to be unprovoked.
In 198 cases (48.6%) there was more than 1 person present at the site of attack. There was only 1 person present at the site of attack in 209 cases (51.4%) and unknown or not reported in 110 cases. Dogs were present in 34 cases when an attack occurred and may have been partially responsible for the alligator attacking.
In 64 cases, the alligator was known to have been fed in the area of the attack, in 189 cases no evidence of prior feeding in the area was reported, and feeding status was unknown in 17 cases. No information was recorded in 227 cases.
In 144 cases (38%) the alligator was observed by the victim or witnesses immediately prior to the attack. In 91% of cases the attacking alligator was seen by the victim or witnesses during the attack. The behavior of the attacking alligator was categorized by witnesses or reporters (486 cases) and also assessed by Wildlife Commission biologist (424 cases). The witnesses felt the alligator behavior was defensive/territorial or protecting nest/young in 216 (44.4%) cases and considered the victim as prey in 142 (29.2%) cases. In contrast, the biologists suggested the alligator considered the victim as prey in 210 (49.5%) cases and the attack was defensive in 145 cases (34.2.7%).
Alcohol or drug use was reported in 27 of the victims, and absent in 85 victims. Recreational drug or alcohol use was not reported in the remaining cases.
There have been at least 24 alligator-related deaths reported in the United States and 22 of these occurred in Florida. An additional 13 deaths in Florida have been reported, but in these cases the alligator bite injuries appear to have been postmortem or body parts were found and the cause of death was uncertain. The average age of the victims with fatal outcomes in Florida was 33.2 years (range 2–82 years). The fatalities consisted of 13 males and 9 females. The size of the alligators associated with the fatalities ranged from 6'6” to 12'4” (2.0–3.76 m), and most were over 8 feet (>2.43 m) in length. In most cases, only 1 alligator was involved in the attack. Time of attack was noted in 14 cases: 7 deaths were reported from 12:01 pm to 6:00 pm; 4 deaths from 6:01 pm to midnight; 1 death from 6:01 am to noon; and 2 deaths were reported to have been at dusk. Reported activities of victims at the time of the fatal attacks in Florida are shown in Table 5. Two deaths have been reported in Georgia. One was of an 82-year-old woman and the other was a 4-year-old girl.
Table 5Activity of victim at time of alligator attack resulting in fatality
in: Prevention and Control of Wildlife Damage. Cooperative Extension Division, Institute of Agricultural and Natural Resources, University of Nebraska–Lincoln,
Lincoln, NE1994: F1-F6
The average sizes for adult female and male alligators are 8.2 feet (2.49 m) and 11.2 feet (3.41 m), respectively. However, males can grow up to 19 feet (5.79 m) long and weigh nearly 1000 pounds.
Alligators are ectothermic, relying on external sources of heat to maintain their body temperature. They are most active at warmer temperatures and prefer 82° to 92°F (28°–33°C). They become dormant at temperatures below 55 °F (13 °C).1 Alligators usually breed in late May or early June and the female lays a clutch of 30 to 50 eggs.
Alligators are carnivorous, have very strong jaws, and use their sharp teeth to seize and hold their prey. Bites are characterized by puncture wounds and/or torn flesh. Alligators may spin on their long axis, “death roll,” after biting their prey to tear off the limbs and drown their prey.
in: Prevention and Control of Wildlife Damage. Cooperative Extension Division, Institute of Agricultural and Natural Resources, University of Nebraska–Lincoln,
Lincoln, NE1994: F1-F6
Alligators are not generally aggressive towards humans, but aberrant behavior may occur. Smaller alligators usually only make single bites; however, up to one third of attacks may involve repeated bites.
in: Prevention and Control of Wildlife Damage. Cooperative Extension Division, Institute of Agricultural and Natural Resources, University of Nebraska–Lincoln,
Lincoln, NE1994: F1-F6
This review found 19% of victims experienced more than 1 bite during an attack. Serious and repeated attacks usually are made by alligators over 8 feet (>2.43 m) in length, and are probably due to chase and feeding behavior.
in: Prevention and Control of Wildlife Damage. Cooperative Extension Division, Institute of Agricultural and Natural Resources, University of Nebraska–Lincoln,
Lincoln, NE1994: F1-F6
Alligators quickly become conditioned to humans, especially when food is involved. These food-habituated alligators lose their fear of humans and can be very dangerous to unsuspecting people.
in: Prevention and Control of Wildlife Damage. Cooperative Extension Division, Institute of Agricultural and Natural Resources, University of Nebraska–Lincoln,
Lincoln, NE1994: F1-F6
In almost one fourth of cases in this review, the alligator was known to have been previously fed in the area where the attack occurred. In 39% of cases, the attack appears to have been provoked by humans or dogs. Investigation of these encounters by a biologist suggested that almost 50% were due to predatory behavior.
Traumatic bites from alligators and crocodiles may cause amputations or even death. In a study of crocodile attacks in southern Malawi, 60 patients were injured over a 4-month period. Twenty-four (40%) had serious injuries resulting in permanent deformity and 1 died of sepsis.
Injuries in survivors ranged from minor lacerations and puncture wounds to major abdominal, chest, and limb trauma. External injuries may appear minor, but massive internal injuries may occur from direct heavy crush injuries by the jaws.
General management of alligator wounds includes thorough debridement of wounds, fixation of fractures, restoration of vascular integrity, repair of nerve and tendon injuries, anti-tetanus prophylaxis, and appropriate broad-spectrum prophylactic antibiotics.
In a case of crocodile bite forearm amputation where pain was not relieved by intravenous opiates, continuous infraclavicular brachial plexus block with bupivacaine and lidocaine has been used successfully.
Numerous aerobic, anaerobic, and fungal species have been cultured from the mouths of alligators. Flandry et al studied the oral flora of Alligator mississippiensis and cultured more than 38 species of bacteria and 20 species of fungi.
The aerobic bacteria isolated included Aeromonas hydrophila, Citrobacter freundii, Bacteroides oralis, Proteus vulgaris, and Pseudomonas spp. The anaerobic microbes isolated included Clostridium bifermentans, Bacteroides bivius, Fusobacterium varium, Peptococcus prevotii, and Clostridium tetani. In an alligator bite in Louisiana, Aeromonas hydrophila, Enterobacter agglomerans, and Citrobacter diversus were isolated.
Aeromonas infections may be rapidly progressive becoming manifest within 24 to 48 hours after injury. These organisms are found in fresh and brackish waters and soil. Infection may be associated with cellulitis or bullae formation that may progress to areas of frank necrosis.
Another gram-negative organism found in marine and estuarine environments, Vibrio vulnificus, may also cause rapidly progressive infections after an external injury, particularly in persons with underlying liver disease or hemochromatosis.
Cutaneous lesions often develop into hemorrhagic bullae or vesicles and then necrotic ulcers. Howard and Burgess reported 1 case of Vibrio infection after an alligator injury.
In case the victim is submerged and develops pneumonia, then Psuedoallescheria boydii should be considered in the differential diagnosis. This fungus may disseminate into the central nervous system if not treated early. Voriconazole has been recommended as therapy to add to the antibiotic regimen in case the victim develops pneumonia and the history suggests aspiration of water.
There are limitations in using only reports to wildlife officials regarding alligator attacks. The number of alligator-related injuries reported in this study should be considered a minimum. Alligator farming is practiced in several Southern states. The frequency of injuries from encounters with farm-raised alligators is not known and, unless serious, are not likely to be reported to wildlife officials. Additionally individuals that keep alligators as pets are not likely to voluntarily report injuries, nor are individuals that are injured while poaching animals. Other deficiencies are apparent when reviewing the telephone surveys with wildlife officials. One problem noted with attempting to obtain information on alligator attacks is there is no uniform system for collecting information and no mandatory reporting of alligator attacks in most states. Some states do not track nuisance calls and the definition of a nuisance may vary by state. Information about alligator attacks may not be passed on when wildlife officials retire, so number of bites reported in a previous survey may not match the number reported by the current official. This report uses the highest number of attacks reported if more cases were reported in previous surveys than were provided by current officials to this author. As actual medical records were not reviewed, it is not known how many wounds actually became infected. Also in some cases, especially from the earliest reports in the Florida database, where victims believed their injuries were due to an alligator attack, the cases may not have been confirmed by wildlife officials as being due to an alligator.
The alligator population is increasing in the United States and so is the number of nuisance complaints.
Thousands of nuisance complaints are reported yearly, and according to wildlife officials, the numbers in most states are increasing. In Florida the number of nuisance calls related to alligators increased from 4914 in 1987 to approximately 18 307 in 2006.
Florida and Louisiana report the most nuisance calls and many alligators are moved to other areas of the state or are harvested once a nuisance call is investigated. It is not clear why Florida reports more alligator attacks than Louisiana given their similar populations of alligators. Perhaps it is related to differences in tourism and underreporting. Further studies to evaluate the similarities and differences in the frequency of alligator encounters between these 2 states is suggested. It is likely that the number of alligator attacks will increase as the human population moves into coastal areas of the Southern States.
Safety tips to prevent alligator bites have been recommended.
Actions to be avoided include allowing small children to approach bodies of water that may be inhabited by alligators; swimming outside of posted swimming areas; swimming at dawn, dusk, or nighttime when alligators most actively feed and they may be more difficult to see; swimming in murky water any time of the day; feeding or enticing alligators; throwing fish scraps into water or leaving them on shore; allowing pets to swim in waters not known to be free of alligators; and removing alligators from their natural habitat or accepting one as a pet. Furthermore, individuals should call their fish and wildlife office to report a nuisance alligator. A uniform reporting system should be developed for states to use to obtain more information about alligator encounters. A regional meeting of Southern states' fisheries and wildlife officials to address this issue may prove beneficial.
Acknowledgments
The author would like to thank the following personnel of the fisheries/wildlife offices of the listed states for providing information: Greg Waters—Georgia; Amos Cooper—Texas; Jeff Boundy—Louisiana; Gary Moody and Chuck Sharp—Alabama; Ricky Flynn—Mississippi; John Kleopfer—Virginia; Jay Butfoloski—South Carolina; Jeff Hall—North Carolina; Joe Hamphill—Oklahoma; Kelly Irwin—Arkansas; Walter Cook—Tennessee; Blair Hayman and Allan Woodward—Florida.
References
Woodward A.R.
David D.N.
Alligators.
in: Prevention and Control of Wildlife Damage. Cooperative Extension Division, Institute of Agricultural and Natural Resources, University of Nebraska–Lincoln,
Lincoln, NE1994: F1-F6
Thirteen other cases in Florida involved individuals who may have had postmortem alligator-related injuries or body parts found but cause of death uncertain.
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