Chapter 58 Alligator and Crocodile Attacks

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Crocodilians have inundated cultural media from traditional folklore to modern television.²⁵ In addition to their fearful appearance, they are one of the few animal species that will attack and kill humans.²⁰ Evidence can be found in paleontologic references that crocodilians preyed on human ancestors.⁷ Crocodilians have been feared and worshiped in ancient societies such as the Australian Aborigines, Iban people of northern Borneo, Cambodian villages, ancient Egyptians, and Native Americans.³ Following World War II, alligators were increasingly hunted, and because of a decline in numbers, were listed in 1967 on the endangered species list. Following federal protection, they were removed from the list in 1987; alligator populations in the southern United States have since increased.¹⁵ Many populations of crocodilians, however, have not fully recovered. With rising human inhabitation around coastal zones of Australia and the southern United States, human–crocodilian interactions are likely to increase.⁵

Crocodiles, alligators, and caimans are all parts of the reptilian order Crocodylia, comprising a total of 23 species separated into three families: Alligatoridae (with 8 species, including alligators and caimans), Crocodylidae (14 species, including the crocodiles), and Gavialidae (including the Indian gharial) (Figure 58-1).³ Crocodilians date to the time of the dinosaurs and are one of the oldest living members of the reptile family. Alligators and caimans belong to the same crocodilian order, and both have shorter, wider snouts than do crocodiles.⁸ When an alligator or caiman is seen with a closed mouth, its upper jaw hides the fourth, lower tooth. Some species of caimans have bony ridges, called spectacles, between the eyes.⁸ Three such species of crocodilians (genus Crocodylus) and alligators (genus Alligator) exist in the United States, two native and one foreign.²⁸ The American alligator (Alligator mississippiensis [Figure 58-2, A]) is the most common species and found in most southern states, including Florida, Georgia, South Carolina, North Carolina, Louisiana, Alabama, Arkansas, Mississippi, Texas, Oklahoma, and likely Tennessee (Figure 58-3). The American crocodile (Crocodylus acutus [Figure 58-2, B]) is found only in south Florida. The non-native caiman (Caiman crocidilus [Figure 58-2, C ]) is becoming increasingly established in south Florida.¹⁶

FIGURE 58-1 The order Crocodylia is broken into 3 families: Alligatoridae, including alligators and caimans; Crocodylidae; and Gavialidae, which includes the gharial.

FIGURE 58-2 Three species of Crocodylia live in the Americas. A, The American alligator (Alligator mississippiensis). B, The American crocodile (Crocodylus acutus). C, The caiman (Caiman crocidilus).

(A Courtesy Brad Weinert; B courtesy Gerard Caddick and Terra Incognita; C courtesy George Hertner.)

FIGURE 58-3 Map of crocodile- and alligator-inhabited regions of the United States.

Worldwide, crocodilian habitats include southern United States, Central and South America, sub-Saharan Africa, India, Sri Lanka, southern China, the Malay Archipelago, Palau, the Solomon Islands, and northern Australia (Figure 58-4). Larger species of crocodiles include the saltwater and Nile crocodiles. These are notoriously the most dangerous, reportedly killing hundreds of people every year in Africa and Southeast Asia.⁵

FIGURE 58-4 Map of crocodile- and alligator-inhabited regions of the world.

Characteristics, Lifestyle, and Habits

The crocodile family dates back 225 million years to the Mesozoic Era. Crocodilians evolved, along with modern birds, from a group of animals known as thecodonts. Crocodilians can live in captivity up to 66 years of age, with most living up to 50 years of age in the wild.⁸ Crocodilians vary in size, but in general males are larger than are females, with the most growth occurring during the first two years of life. For example, the American alligator reaches a maximum adult size of 4.5 m (14.8 feet) and the American crocodile 6 m (19.7 feet). The common caiman reaches 2.8 m (9.3 feet). The notorious Nile crocodile reaches 5.5 m (18 feet) and the saltwater crocodile 7 m (23 feet) (Table 58-1).⁸ Breeding season is typically late May or early June, with females laying clutches of 30 to 50 eggs. Their diet is predominantly carnivorous, and includes fish, snails, birds, small mammals, frogs, and crustaceans.

TABLE 58-1 Crocodilian Lengths by Species

Species and Latin Name	Maximum Adult Male Size
American alligator (Alligator mississippiensis)	4.5 m (14.8 feet)
American crocodile (Crocodylus acutus)	6 m (19.7 feet)
Australian freshwater crocodile (Crocodylus johnsoni)	3 m (10 feet)
Black caiman (Melanosuchus niger)	4.6-6 m (15-19.7 feet)
Common caiman (Caiman crocodilus)	2.8 m (9.3 feet)
Nile crocodile (Crocodylus niloticus)	5.5 m (18 feet)
Saltwater crocodile (Crocodylus porosus)	7 m (23 feet)

Data from Dudley K: Alligators and crocodiles, Calgary, 1998, Weigl Educational Publishers Limited.

Crocodilians, like all reptiles, are ectothermic (cold-blooded). They rely on their environment for body temperature, and as a result, their activity level depends greatly on the time of day. In hot climates, crocodiles keep cool during much of the day by staying underwater, before they move onto land during the night. They may remain submerged for more than an hour. They may also be found in mud burrows close to the water’s edge as they lay their eggs or retreat from the water during colder months. Special adaptations make them superior predators in the water environment, preferring slow moving water to preserve their sense of smell when submerged. Crocodilians in cool climates bask in the sun to stay warm.⁸ Crocodilians may also rest with the mouth open, using the thin skin inside the mouth as a radiator to increase cooling.

Crocodilians are largely nocturnal creatures, using their characteristic slit-like eyes to make use of more light than does a round pupil.⁸ A third eyelid helps protect their eyes while they swim underwater, making them more effective hunters in murky water. Watertight nostrils on the distal end of their long snouts allow an impeccable sense of smell, even when the majority of the body is completely submerged under water. Crocodilians have roughly 28 to 32 teeth in the lower jaw and 30 to 40 teeth in the upper jaw. These teeth are excellent for grabbing and tearing, but cannot be used for chewing. Thus, crocodilians must tear their prey into pieces before swallowing them. Broken teeth are replaced by new teeth growing under exiting teeth, in a manner analogous to that of sharks.⁸ The jaws of the American alligator were noted in one study to produce the biting force of 1000 kg (2.2 tons).³ This is enough force to crush large bones and shells. Opposing muscles used to open these massive jaws, however, are quite weak and easily kept closed by human arms, as depicted by popular television and alligator tourist shows.

Feeding and Predation Habits

Saltwater crocodilians are generally larger and more aggressive than are freshwater crocodilians. They are more active at night and during the summer months but are opportunistic feeders and will pursue a meal when one becomes available. Larger crocodilians have been known to attack larger prey such as pigs, cattle, buffalo, horses, and humans. In addition to shallow and deep water, attacks have been witnessed on beaches and riverbanks.

Crocodilians have peg-like teeth well adapted for catching and holding onto prey. However, the teeth are not well suited for chewing, so most prey is killed and allowed to rot, which makes it easier to swallow.²⁸ Once captured, prey is often completely neutralized by being crushed by the attacker’s powerful jaws. Larger prey animals are often attacked at the lower extremities, throwing them off balance prior to their being dragging into the water and drowned. Once overtaken, smaller animals are swallowed whole. Violent thrashing of the crocodilian head from side to side dismembers larger prey. Further attempts of separating smaller pieces are accomplished by rolling the prey over and over underwater, the so-called “death roll.”²⁸ As a result, victims of crocodilian attacks are generally severely disfigured with significant crush injuries.²⁰

Attacks

Most crocodilian attacks occur “out of the blue” as the attacking animal utilizes a sudden burst of speed and the advantage of surprise.⁶ An adult crocodile can devour prey much larger in size than a human. According to one report, the stomach of an Australian estuarine crocodile contained the remains of an aborigine and a 4-gallon drum containing two blankets. The crocodile can travel in water at a speed of 32 km/hr (20 mph) and can charge a short distance over land at 24 to 48 km/hr (15 to 30 mph). The enormous jaws and canine teeth can bite with sufficient force to sever an outboard boat propeller. Feeding in freshwater rivers and adjacent land has introduced them to cows, horses, and humans, who are attacked when they cross rivers, catch fish, draw water, or work in the fields.²⁷ Alligators residing in lakes and ponds associated with golf courses, parks, and tourist attractions have attacked humans in the United States.²⁵

A study in the United States analyzing crocodilian attacks between 1928 and 2009 identified that 567 adverse encounters and 24 deaths had been reported. It is estimated that these events are largely underreported, and may not be representative of notably higher incidence in other countries. Most fatalities are reported in Florida, followed by Texas, Georgia, and South Carolina.¹⁶ Severe injuries described as life or limb threatening represented only 11.8% of cases. Attacks in most instances were only a single bite (81%). Victims were more likely to be males (85.4%) and adults 18 years of age or older (78.6%).¹⁶ Most injuries were classified as lacerations and punctures to the arms, forearms, hands, fingers, legs, and thighs. Most injuries occurred while handling alligators, followed by wading or swimming, typically occurring in deep (>1 m) water, followed by shallow water, and within 1 m from shore.¹⁶ Most attacks occurred between the months of May and August and during the afternoon hours to twilight (Figure 58-5). Of the attacks in this study, 33% were felt to be provoked, with the majority of instances stemming from the victim trying to handle the alligator or trying to rescue another human or animal victim. The majority (54.8%) of cases were felt to be unprovoked.