Nile Monitor Care
What You Need to Know About
from By Philippe de Vosjoli
look like dragons and behave like any other large carnivore.
They’re imported indiscriminately, with thousands sold each
year. They grow quickly from charmer to liability, and outgrow any
habitat smaller than a room. They are
Alert and intelligent,
monitors’ place in herpetoculture should be at the pinnacle, in
the capable hands of experienced, responsible and dedicated
keepers. Large monitors, however, continue to be popular in the
pet trade as highly affordable juveniles. Most Nile-owning
people are unprepared for what lies ahead. You will need to know
the basics of care and what to expect from adults.
A cute baby
in the pet shop tank is deceptive, for prospective owners cannot
conceive of its incredibly rapid growth. For example, a leopard
gecko will increase its hatching weight 20-30 times (approximately
3.5 g to 100.0 g).
in contrast, will grow 200-300 times birth weight (30 g to
Size is emphasized here because it is the single most
important issue for owners of
Other large monitors offered in the trade, e.g., ornate (V.
ornatus, formerly V. niloticus ornatus), Asian
water (V. salvator), white-throat (V. albigularis)
and crocodile monitors (V. salvadori, present similar
problems in husbandry. In the guidelines that follow, every aspect
of husbandry addresses the large size of
Hatchlings can start off in tanks 3’ long with secure screen
tops. After 6 months they need enclosures of at least 4’ x 2’.
Adults (2-3 years old) require an enclosure the size of a small
room, at least 12’ x 4’ for monitors under 48 inches in length
and at least 15’ x 5’ for specimens exceeding 48”.
Juvenile monitors should be provided with shelters in which they
can curl their entire body. Adults should be offered plastic
doghouses or the top half of large dog carriers. Many monitors use
their shelter for sleep. Others will spend the night on tree
branches or in their water container. Flat rocks are required for
nail wear. If rocks are placed alongside the water container,
nails will wear as the lizards enter and exit the water.
To accommodate high levels of activity and digging, the best
substrates are mixes of peat moss-based potting soil, ground fir
bark and sand, with some coarser material such as a fine grade
ground limestone to help wear nails. This substrate allows the
digits to remain in a normal position rather than twist to the
side, as found in large monitors kept on solid flooring. (Note:
Dr. Horton prefers paper, carpet, or recycled newspaper).
may release a brown dust that will cover everything in the room.
Newspaper can be used with young animals, especially prior to
worming, but is unsightly and fails to provide a proper texture
Temperature and Light
Extra light and heat are required for monitors of all ages. Lights
should be on 12-14 hours a day.
The temperature measured right under the basking site should be
88-92° F. For thermoregulation, part of the habitat should be
5-10°F cooler. As for most amphibious monitors, the
activity temperature is relatively low, about 90° F. For
juveniles, overhead spotlights are sufficient. For monitors over
30” in length, one needs combinations of large reptile heat pads
and at least 2 spotlights, or 1 spotlight and 1 infrared ceramic
incandescent heat bulb over one or more basking sites. These can
be controlled by rheostats or thermostats.
Monitors benefit from exposure to a UV-B source (e.g., ZooMed®
5.0 fluorescent bulbs) when young, and for larger animals, mercury
vapor reptile UV-B bulbs. Alternatively, an area can be provided
can bask in unfiltered sunlight (through a welded wire
screen-covered window or in an outdoor plastic-coated welded wire
cage during the summer).
Diets for juveniles can be 4-week-old crickets gut loaded with a
multivitamin/ calcium/ vitamin D3 supplement.
should be fed crickets daily and offered a pinkie mouse weekly.
For older juveniles, king mealworms can substitute for crickets,
and larger mice can be offered. However, unlike broad-snouted
monitors, the narrow-snouted
can feed only on relatively small vertebrates (with body width
less than 2/3 the width of the monitor’s head). Monitors over 3
feet long will continue to enjoy king mealworms but the bulk of
their diet is best filled by a carnivore diet meat mix or mice.
Various zoos use a diet of lean ground turkey supplemented with
calcium carbonate and a complement of vitamins and minerals. The
turkey is either cooked or frozen for about a month to reduce
risks of Salmonella transmission. Commercial meat-based
carnivore diets can also be fed.
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.
Accessible water tubs large enough for complete immersion are
required. For small individuals, reptile water dishes, dog bowls
and plastic storage containers suffice. For adults, plastic cement
mixing tubs or plastic kiddie pools are required.
kept singly usually defecate in their water container. If kept in
groups (one male and one or more females), mating attempts by
males will often cause the females to defecate on the ground as a
Sexing is difficult in juveniles. Males may evert their hemipenes
during handling or defecation. Males generally grow larger, with a
proportionately more elongated head. Growth rates of females slow
significantly during sexual maturity while males continue to grow
rapidly for another 2 years at least.
Females raised since hatching may be tame when kept in larger
front-opening cages. They are generally less active than males. In
contrast, males generally display a much higher level of
responsiveness and curiosity, but tame less readily.
If kept in cages that are too small,
usually display behavior of being cornered, manifested by frantic
flight attempts and, when these fail, holding ground and
on this interesting animal to come.
Thank you for giving us the opportunity to
provide helpful service to you and your pet. If you have any
questions, give us a call at 847-329-8709.
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