Spiny-Tailed Monitor/Ackie’s Dwarf Monitor/Ridge-Tailed Monitor

Spiny-Tailed Monitor/Ackie’s Monitor/Ridge-Tailed Monitor Varanus acanthurus

Type of Animal:

Rocky areas, rocky ranges, outcrops, scrubland, trees, burrows, lowland areas of shrubs & spinifex grass, stony areas, rock crevices, desert, grassland, shrubland, arid flat areas near rock outcrops, tropical escarpments, boulders, subhumid to arid woodlands

N Western Australia, most of Northern Territory, W Queensland, & islands off E Northern Territory

Color ranges from dark brown to bright yellow to cream to red w/ spots/stripes, spots very visible, dark scales, “Red Ackies” more common in W part of range, “Yellow Ackies” more common in E part of range, Reds bigger than yellows w/ longer tails, streamlined body

Insects, insect larvae, grubs, spiders, snails, eggs, smaller lizards (including smaller members of own species & smaller monitor species), shrimp, small mammals, small snakes

Status in Wild:

Breeding in zoos & herpetoculture

Solitary or small harems of a male w/ 3 females

Additional Info:

Young: Hatchling
Group: Colony
Male: 11-12 oz
Female: 10-11 oz
17 weeks 

Life Span:
15-20 years

Body Length:
Male: 2.3 ft
Female: 2 ft
Young: 1 ft

Tail Length:
Male: 2.76-5.29 ft
Female: 2.4-4.6 ft
Young: 1.2-2.3 ft

Main predators are larger monitors, snakes, raptors, cats, & foxes.
Like many monitors, it’s an ambush predator.
Females can produce up to 6 clutches a year (each w/ 4-18 eggs). Eggs usually white oval shaped.
They’re rather curious lizards.
Active during the day (diurnal).
Gravid (pregnant) females have voracious appetites.
Uses camouflage to hide from predators & catch prey.
Sexually mature at a year old.
Breed from August-November.
Hatchlings & juveniles sometimes show mounting behavior as way to exert dominance.
Fights between males can be vicious & sometimes deadly.
They’re built for burrowing & digging.

Fun Fact(s):
One of most common monitor lizard species kept as pets due to small size.
70% of water requirement comes from food.
When threatened, they’ll retreat into tight spaces (i.e. rock crevices) & puff bodies to wedge themselves between rocks. If this doesn’t work, they can whip tails & bite.
Spiny-Tailed Monitor, Ridge-Tailed Monitor, Ackie’s Dwarf Monitor, stock photo

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