Species Fact Profile: Crocodile Monitor (Varanus salvadorii)

Crocodile Monitor

Varanus salvadorii (W. Peters & Doria, 1878)

Range: Southern New Guinea

Habitat: Coastal Lowland Rainforest, Mangrove Wetlands

Diet: Small Mammals, Birds, Eggs, Reptiles, Amphibians, Invertebrates, Carrion

Social Grouping: Solitary

Reproduction: Males court females by licking, stroking them prior to breeding; engage in ritual combat with other males for access to females.  4-12 eggs buried by the female, receive no additional parental care.  Hatch after 20 day incubation period

Lifespan: 10 Years

Conservation Status: IUCN Least Concern, CITES Appendix II

• Largest monitor species on New Guinea, sometimes described as the world’s longest lizard (though it is much more slender than many other large varanids).  Total length up to 2.65 meters, of which two-thirds is typically made up of by tail. There is a record of a 3.2 meter specimen, and there are unconfirmed lengths up to 5 meters.  Average weight of 20 kilograms.  Males are larger than females – female halt growth as soon as they reach sexual maturity at two years old, while males continue to grow
• Skin is covered with non-overlapping scales, primarily black or dark green with irregular yellow spots and yellow rings around the tail.  Hatchlings are more colorful than adults
•  Extremely agile climbers, using the long tail for balance as they climb or jump through the branches.  Tail is somewhat prehensile.  Can hang from branches by their back legs.  Contractions of their throat muscles allows for rapid intake of oxygen, facilitating quicker movements, more stamina than many lizards (even most other monitors).
•  Initially believed to be primarily arboreal, but have been observed being active on the ground for considerable amounts of time.  Believed to be a good swimmer, have been observed sleeping underwater
•  Native Papuans have reported crocodile monitors killing prey up the size of pigs and dogs, hauling their kill up into the trees to eat like a leopard.  Often stalk prey, try to anticipate its movements and get ahead of it, then charge
• Adults are not believed to have any major predators.  If angered, may use the tail as a whip.  Intolerant of human disturbance, avoids settled areas
• Have been historically utilized by Papuan people for their meat and skins, which are used in the heads of ritual kundu drums.  They are not actively hunted or sought out (in part due to their reputation for aggression), but may be trapped in snares set for other species. Viewed by some native peoples as an evil spirit with the power to breathe fire, walk upright like a person, and kill men; also believed to warn people of the presence of crocodiles
• Species does not face any major threats, but may be under pressure due to habitat loss from deforestation.  Range is fragmented, occurs at low density.  Present in the international pet trade, but collection is unlikely to be a major threat (set export quota)
• Lay eggs readily in captivity but they are seldom fertile; humidity and oxygen levels are considered key factors in reproductive success
• One human fatality reported from 1983, when a Papuan woman was bitten by a crocodile monitor and later died from a resulting infection

      Zookeeper's Journal: When I was young, I was disappointed that my local zoo  didn’t have Komodo dragons… just a pair of crocodile monitors.  Looking back years later, I can’t believe I was ever so jaded – the crocodile monitor has grown to become my favorite lizard, if not my favorite reptile.  If a Komodo is a lizard tiger, a spiny-tailed monitor is a mongoose, and a Merten’s water monitor is an otter, than a crocodile monitor is a reptilian leopard.  It possesses the arboreal agility, the hunting savagery, the fierce reputation – heck, it even has the spots.  My favorite nature painting of all time, by Carel Pieter van Kempen, depicts a crocodile monitor chasing a doomed rodent across the canopy of a Papuan rainforest.  With its large size and great beauty, the crocodile monitor is immensely popular with zoos and expert-level collectors, though it does have a nasty reputation for aggression, and I’ve heard more than a few stories of keepers who have gotten quite the chomp.  In some, I’ve seen the scars myself.  My own experience has been that female crocodile monitors suffer from a bit of a Napoleon complex and tend to be much more voracious and fierce than the males.  The boys on the other hand often seem to get mellower as they get bigger.  I’ve worked with two large specimens who acted more like big dogs than vicious predatory reptiles – one of them was allowed to roam freely in the behind-the-scenes areas of the Reptile House for much of the day, and even went for a ride on the Interstate while draped across a keeper’s dashboard.  Not recommended