The New Caledonian Giant Gecko is the largest gecko species on the planet, with adults reaching up to 17 inches in length. These types of geckos have robust bodies and large heads, with unique granular skin covering them. 

Their color palette ranges from greens to browns, often decorated with patterns of varying shades, enabling them to blend into tree bark and foliage.

This type of gecko is a nocturnal predator that feeds on insects, fruits, and small mammals, occasionally indulging in cannibalism. 

They also communicate through growling, barking, and hissing, which are crucial, especially during the mating season.

The Nile crocodile, stretching up to 16 feet long, is the second-largest crocodilian and the largest in Africa. Predominantly, the males reach this size; females remain somewhat smaller. Their bodies, cloaked in a dark bronze shell dotted with black and a hint of belly purple, make a perfect camouflage for preying. 

This crocodile boasts an impressively strong bite force, almost 3,000 PSI, one of the highest among animals. They inhabit the freshwater venues of Sub-Saharan Africa, the Nile Basin, and even Madagascar. These habitats provide an ideal mix of protective cover and bountiful food resources. 

Contrary to common belief, Nile crocodiles are not solitary by nature. They have a social structure, showcasing dominance and sometimes even disputes. 

They also have a sharp sensory system. This crocodile can sense minute changes in water pressure, which is vital for hunting.

The American crocodile reaches a hearty 13.5 feet in length, sporting broad snouts studded with sharp teeth for grappling prey. 

They are the only crocodile species native to the US, primarily seen in southern Florida and at times sighted in Louisiana and Texas. Their olive-gray hue provides excellent camouflage in their surroundings, hiding them from prey until the ideal strike moment.

Because of their adaptability, these crocs are the most widespread of all species living in America. They can survive in fresh wetlands, coastal lagoons, and river estuaries and even handle saltwater, courtesy of special glands that filter out excess salt. Other types of crocodiles may have tolerance to salt. Still, only the American crocodile4, other than Saltwater Crocodiles, can thrive in saltwater environments.

Despite their formidable presence and efficient predation, they tend to be reserved and mainly avoid humans. Males are territorial, and despite their solitary life, they contribute significantly to the ecosystem by keeping prey populations in check.

The Freshwater Crocodile can be found in Northern Australia. This species is also Johnston's Crocodile, commemorating the amateur naturalist Robert Arthur Johnstone, who first reported it. 

They have light brown bodies with darker bands at the back and tail. Males typically measure up to 9 feet, while females average around 7 feet. Their narrow snouts, distinguishing them from other crocs, are ideal for catching fish, insects, and small amphibians.

These freshwater crocodiles inhabit rivers, wetlands, and creeks, living away from Saltwater Crocodiles as much as possible to avoid confrontation.

The Saltwater crocodile is the world's largest land predator and reptile, stretching up to 20 feet long and weighing more than a ton. It can also overpower other predators, including lions and bears, thanks to their 3,700 psi biting power, which is the highest among other types of crocodiles2.

Their distinguishing features include wide, hefty snouts and rugged, dark green scales that blend with the surroundings, while their bellies flaunt cream-colored scales.

Also called marine crocodiles or sea crocodiles, their range spans from the eastern Indian shores to Southeast Asia and northern Australia. Remarkably tolerant to saltwater, these robust crocs tend to live in saltwater habitats but can also thrive in brackish and fresh waters. 

Their feeding habits are highly opportunistic, and they prefer to hunt submerged in water. Nothing, including fish, birds, and mammals, seems to escape their menu. Their infamous "death roll" hunting strategy is brutal but effectively attacks larger prey.

The Cuban crocodile, hailing from the heart of the Caribbean, displays a stunning mix of olive and gold hues. Males can reach up to 11 feet, with females slightly shorter. You'll commonly spot Cuban Crocodiles in the Zapata Swamp or Isle of Youth in Cuba.

Don’t let their medium size fool you. These territorial crocodiles are intelligent and aggressive5. Many scientists and zookeepers have observed these, from cooperative hunting to challenging handling. 

Unfortunately, Cuban Crocodiles are critically endangered8, with less than 2,400 individuals in the wild. They face various threats, including water pollution, climate change, illegal hunting, and habitat transformation. Additionally, hybridization with the American Crocodile compromises their genetic integrity and introduced crocodilians to compete with their resources.

The Philippine crocodile is another critically endangered species needing immediate protection6. It typically grows up to 8.8 feet. Notable features include a wide snout and durable dorsal shield. 

Endemic to the Philippines, this species dwindles in three regions, with fewer than 200 mature individuals, a decrease of 82%. Despite reintroduction attempts, an 85%-94% drop in adults exists over three generations. 

The species faces threats from habitat loss, persecution, and fishing net entanglement. High conservation dependence is noted - discontinuing conservation actions could result in extinction within ten years.

Hailing from Central America's freshwater habitats, the Morelet's Crocodile, also called the Mexican Crocodile, ranges vastly across Mexico to Guatemala. These medium-sized creatures extend up to 10 feet, with males often outsizing females.

Characteristically, this species sports a dark, grey-brown skin adorned with bands and spots over their frame and tail. This helps them blend and become nearly invisible, hunting stealthily in the murky marsh, swamp, and lake waters, which they prefer.

Their reputation includes a noticeably short temper, particularly during breeding seasons. An intriguing behavior they exhibit is their distinctive "water dance"- a body oscillation that makes the water pulsate, essential for their communication.

Though they were previously exploited for their valuable hide in the 1950s, they've rebounded thanks to dedicated conservation measures. They now hold a least concern status. However, they're still as threatened by habitat loss, pollution, and climate change as before.

The New Guinea Crocodile is a small-sized species, with males measuring up to almost 11 feet and females appearing a bit smaller. However, they both feature a broad snout and ridges down their backs and tails, distinguishing them from other species. Their green-brown skin is a notable natural beauty, yet it draws the attention of hunters as a valued resource.

They inhabit the freshwater swamps and lakes of North Guinea, while the previous type of crocodile lives in the south.

Exhibited by their love for hunting at night, New Guinea crocodiles cleverly utilize their night vision for survival. During the day, they either spend submerged in water or bask in groups.

The medium-sized Siamese crocodile, typically up to 9.8 feet, epitomizes freshwater wildlife with a sleek, olive-green exterior. Unlike its bigger kin, it boasts a smooth snout that mirrors its placid surroundings across Southeast Asia's marshlands, from Cambodia to potentially Thailand.

Unfortunately, Siamese crocodiles are critically endangered7, with populations significantly fragmented and reduced, primarily because of commercial hunting, illegal collection, habitat destruction, incidental fishing captures, and hydroelectric dam development. 

Despite new information on its ecology, it remains poorly understood. Without conservation interventions, the species' progressive decline will carry on.