Nile monitors are among the largest lizards in the world, reaching lengths of up to 8 feet and weights of up to 20 kg. They are native to most of Sub-Saharan Africa and along the Nile regions, where they inhabit a variety of habitats such as woodlands, savannas, grasslands, mangroves, and swamps. They are also known as African small-grain lizards, water leguaans, or river leguaans in South African English.
Nile monitors are semi-aquatic and have powerful jaws, sharp teeth, and claws that they use for hunting, digging, climbing, and defending themselves. They have a forked tongue that helps them smell their prey and a long tail that aids them in swimming. They have a grayish-brown to black coloration with yellowish-green markings on their back and tail. Their belly is usually cream-colored or yellowish with faint stripes or spots.
Nile monitors are not a single species but a complex of closely related forms that may or may not interbreed in nature. The most widely recognized subspecies are the Nile monitor (Varanus niloticus niloticus) and the ornate monitor (Varanus niloticus ornatus). For the purpose of this article, we’ll be focusing on the Nile monitor as a species.
The Nile monitor is found throughout most of the species’ range, while the ornate monitor is restricted to the rainforests of West and Central Africa. The ornate monitor has more vivid coloration and patterning than the Nile monitor and is slightly smaller in size.
Another form that is sometimes considered a separate species is the West African Nile monitor (Varanus stellatus), which occurs in the forests and savannas of West Africa. It has a more slender body, a longer snout than the Nile monitor, and a distinctive star-shaped pattern on its back.
|Nile monitor, African small-grain lizard, water leguaan, river leguaan
|Sub-Saharan Africa and along the Nile
|Up to 8 feet in length and 20 kg in weight
|10 to 20 years in the wild and up to 30 years in captivity
Minimum Tank Size
|At least twice as long as the monitor’s size
What Are Nile Monitors?
The Nile monitor is a large and powerful lizard that belongs to the monitor family (Varanidae). It is native to most of Sub-Saharan Africa and along the Nile regions, where it inhabits various habitats near water sources.
It is one of the largest lizards in the world, reaching max lengths of up to 8 feet and weights of up to 20 kg. They are a grayish-brown to black coloration with yellowish-green markings on the back and tail. They have a forked tongue, sharp teeth, and claws that are used quite effectively for hunting, digging, climbing, and defense.
They are carnivorous and opportunistic feeders that will eat nearly anything they can catch and swallow.
They are diurnal animals, most active during the day, and spend most of their time foraging or basking on the shoreline vegetation, trees, logs, or rocks. They are also incredible swimmers and divers and can stay submerged for up to an hour. Dolphins, actual sea creatures, can only hold their breath for 10 minutes!
Generally solitary and territorial, they are seen to communicate with other monitors through visual signals and sounds. Their breeding season is during the rainy season and they lay clutches of 20 to 60 eggs in termite mounds or burrows.
Life expectancy is 10 to 20 years in the wild but up to 30 years in captivity if cared for properly. However, this is not the easiest pet to keep as they require a lot of space, food, water, heating, lighting, and attention.
They are very intelligent and curious and, as such, can become destructive if bored or stressed. They are unsuitable for beginners or children as they can be aggressive and dangerous when incorrectly handled.
Nile monitors are diurnal and active throughout the year. They spend most of their time near water sources where they can hunt, bask, and escape from predators. They are excellent swimmers and divers and can stay submerged for up to an hour. They are also agile climbers and can scale trees and rocks with ease. They often sleep on tree branches or in burrows that they dig themselves or take over from other animals.
Nile monitors are generally solitary and territorial animals that will fight with other monitors over food or mates. They communicate with each other through visual signals such as head bobbing, tongue flicking, body posturing, and tail waving. They also produce hissing and growling sounds when threatened or angry.
Reproduction and Lifespan
Nile monitors breed during the rainy season, which varies depending on the region. The males compete for access to females by wrestling and biting each other. The females lay clutches of 20 to 60 eggs in termite mounds or burrows that they seal with soil and vegetation. The eggs incubate for about six to nine months before hatching. The hatchlings are about 25 cm long and have brighter colors than the adults. They are independent from birth and have to fend for themselves against predators such as birds of prey, snakes, crocodiles, and other monitors.
As I mentioned, Nile monitors are not always the easiest pet to keep. So here are some basic guidelines to take care of their space, food, water, heating, lighting, and attention needs:
Since Nile monitors tend to grow big, it is always better to use an extremely large tank where they can grow up to 9 feet long, climb, run, and even swim. Their ideal housing size is at least twice as long as their size. For example, a 6-foot-long monitor would need a 12-foot-long enclosure. The enclosure should also be at least 4 feet wide and 6 feet high. The enclosure should have a secure lid or top to prevent escapes.
The enclosure should have a basking area, a hiding area, and a water area. The basking area should have a large branch or rock where the monitor can lie down and absorb heat and light. The hiding area should have a large box or cave where the monitor can retreat and feel safe. The water area should have a large tub or pool where the monitor can swim and soak. The water should be deep enough to cover the monitor’s body and should be changed regularly to keep it clean.
Diet and Nutrition
Nile monitors are carnivorous and opportunistic feeders that will eat almost anything they can catch and swallow. Their diet includes insects, spiders, crustaceans, mollusks, fish, frogs, snakes, lizards, turtles, eggs, birds, small mammals, and even young crocodiles. They are also scavengers and will feed on carrion when available.
Nile monitors should be fed every 1-2 days. Niles are almost always hungry and fare best if fed measured portions once daily, although babies can be offered as much as they will eat per feeding. For adults, I feed an amount roughly equal to the volume of the monitor’s head every 2 days. Excess food can lead to obesity in adults.
When they are young, Nile monitors can be fed insects (like crickets, dubia roaches, mealworms, and superworms) that are gut-loaded and dusted with calcium and vitamin supplements. When they are older, they can be fed pre-killed rodents like mice and rats, as well as chicks, quail, and rabbits. Wild Nile monitors eat live prey items but feeding live mice or rats to a pet Nile monitor is not recommended due to the risk of the prey biting your lizard. Monitors with especially large enclosures with numerous hiding spots may be at less risk for injuries from their food, but the potential for bites is still there.
Nile monitors should always have access to fresh water for drinking and soaking. The water should be changed daily or as needed to keep it clean. A large water bowl or tub should be provided in the enclosure that is big enough for the monitor to submerge itself completely. The water level should be checked regularly and refilled as needed.
Heating and Lighting
Nile monitors are ectothermic, meaning they rely on external sources of heat to regulate their body temperature. They need a temperature gradient in their enclosure that allows them to choose between warmer and cooler areas. They also need exposure to ultraviolet (UV) light, which helps them synthesize vitamin D3 and absorb calcium.
The basking area should have a heat lamp that provides a temperature of around 120°F (49°C). The ambient temperature in the rest of the enclosure should range from 80°F (27°C) to 90°F (32°C) during the day and drop to 70°F (21°C) to 75°F (24°C) at night. A thermometer should be used to monitor the temperature in different areas of the enclosure.
The enclosure should also have a UVB lamp that provides 10% to 12% UVB output. The lamp should be placed within 12 inches (30 cm) of the basking area and should cover at least half of the enclosure. The lamp should be on for 10 to 12 hours per day and replaced every 6 months. A timer can be used to regulate the light cycle.
The substrate is the material that covers the bottom of the enclosure. It should be safe, clean, and comfortable for the monitor. It should also retain some moisture and allow for digging. Some good options for substrate are coconut fiber, cypress mulch, orchid bark, or a mixture of these. The substrate should be at least 6 inches (15 cm) deep and changed every month or as needed.
Tank Bedding and Accessories
The enclosure should have some bedding and accessories that provide enrichment, stimulation, and security for the monitor. These include branches, rocks, plants, hides, and toys. Branches and rocks should be sturdy and stable enough to support the monitor’s weight. Plants can be artificial or live, but make sure they are non-toxic if ingested. Hides can be boxes, caves, or tunnels that offer shelter and privacy. Toys can be balls, ropes, or puzzles that encourage exploration and play.
The enclosure should be kept clean and sanitary to prevent diseases and infections. Spot-clean the enclosure daily by removing any feces, urates, leftover food, or debris. Change the water daily or as needed. Disinfect the enclosure monthly by removing everything from it and wiping it down with a reptile-safe cleaner. Rinse well with water and let it dry completely before putting everything back. Wash and disinfect any bedding, accessories, or dishes as well.
Nile monitors need adequate hydration to stay healthy and prevent dehydration. They get most of their water from their food and from soaking in their water bowl or tub. However, if provided, they will sometimes drink from a spray bottle or a drip system. Spray or mist the enclosure daily or every other day with lukewarm water to increase humidity and encourage drinking. A good hygrometer can be used to measure the humidity level in the enclosure, which should be around 60% to 80%.
Nile monitors have been introduced to several places outside their native range by intentional or unintentional releases from the exotic pet trade. One of the most notorious examples is Florida, where they have established breeding populations in several locations such as Cape Coral, Lee County, Florida Keys, Homestead Air Reserve Base, Broward County Regional Park at Weston, and Boca Raton. They seriously threaten native wildlife as they prey on endangered species such as gopher tortoises, American crocodiles, and burrowing owls. They also compete with native predators such as alligators, bobcats, and panthers. They can also transmit diseases such as salmonella, parasites, and rabies to humans and domestic animals. The Florida Fish and Wildlife Conservation Commission (FWC) considers them a high-priority invasive species and encourages people to report any sightings or captures of Nile monitors. The FWC also conducts trapping, removal, and research programs to control their populations.
Nile monitors are amazing and impressive animals with many fascinating features and abilities. They are one of the largest and most powerful lizards in the world, and they can easily swim, climb, dig, and hunt. They are also very smart and curious and have a lot of personality. However, they are not for everyone and should not be taken lightly as pets. They require a lot of research, preparation, and commitment before acquiring them as pets.
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How big do Nile monitors get?
Nile monitors have been seen up to 8 feet and weights up to 20+ kg. Most Nile monitors will max out around 6 feet long and weigh between 0.8 and 20 kg.
Are Nile monitors good pets?
Nile monitors can make great pets for some people. But they are very large, strong, aggressive, and destructive. They need a lot of space, food, water, heating, lighting, and attention, and they are not very tame or trustworthy. So they are really only suitable for experienced and dedicated reptile keepers who can provide them with proper care and respect.
How fast do Nile monitors grow?
Nile monitors grow very fast and can reach adult size in about two years. They can grow up to a foot per year when they are young and need a lot of food and calcium to support their growth. They should be housed in a large enclosure that can accommodate their size and activity level.