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119IGUANADecember 2003

Varanidae is a monotypic family of about 50
species of Old-World lizards containing only the
genus Varanus. These generally large, intelligent, car-
nivorous lizards occur in Africa, Australia, and
Southeast Asia in habitats ranging from deserts and
savannahs to tropical rainforests and mangroves. At
least one large species has gained a foothold in the
Western Hemisphere and may represent a consider-
able threat to native wildlife populations.

The Nile monitor, Varanus niloticus, ranges nat-
urally throughout central and southern Africa. Two
subspecies, the Common (V. n. niloticus) and Ornate
(V. n. ornata) Nile Monitor were once recognized,
but full species status was recently awarded them
both. The former has a blue tongue and 6–9 gold
dorsal bands and the latter has a pinkish tongue and
3–5 dorsal bands. The oft-used vernacular name
“Money Monitor” refers to its coin-sized, gold dor-
sal spots. Reaching a maximum total length of over
two meters (usually about 1.5 m) and a maximum
weight of over 10 kg (usually 5–8 kg), this is one of

the largest lizard species on Earth. They often live to
be 10 or more years old, but reach sexual maturity in
under three years, and larger, older females may lay
60–80 eggs in a clutch. In Kenya, they reach densi-
ties of 40–60 lizards/km2. As a result of their large
size, high reproductive rates, and abundance, this
species is heavily exploited for meat and leather, and
is considered valuable in its native lands — but this
species is particularly unwelcome outside its native
range.

At least 13 years ago, this species became estab-
lished in Cape Coral, a sprawling coastal residential
area near Ft. Myers in southwestern Florida. In the
1950s, the wetlands of this region were ‘reclaimed’
for development by using the spoils dug from an
over 400-mile-long network of deep canals.
Additional aquatic and wetland habitats were cre-
ated in the areas’ numerous golf courses. Moreover,
Cape Coral is fringed by extensive mangroves and
remote barrier islands. These freshwater canals,
lakes, and wetlands, combined with a low density of
homes and remote coastal mangroves, provide ideal
conditions for the establishment and spread of this
species. The origin of the introduced lizards remains
unknown, but the extent of the problem became
apparent in 2000 due to the efforts of Kraig Hankins
(City of Cape Coral), Kenneth Krysko (University of
Florida), and Kevin Enge (Florida Fish and Wildlife
Conservation Commission). This species currently
occupies over 50 km2 of residential areas, canal
banks, and surrounding pine flatwoods, mangroves,

SPECIES PROFILE: 
Nile Monitors (Varanus niloticus) in Florida

Todd Campbell
Department of Biology, University of Tampa

This 5-foot, 15-pound Nile Monitor was captured at a res-
idence in Cape Coral.

Nile Monitors construct burrows in the banks of over 400
miles of canals in Cape Coral.

The remote pine flatwoods of the Charlotte Harbor Buffer
Preserve provide valuable habitat for native species, but
also may be a corridor for expansion of Nile Monitors.



120 IGUANA Volume 10, Number 4

barrier islands, and other natural habitats in and
around Cape Coral.

The impact of this species on native wildlife is
largely anecdotal at this time, but in southwestern
Cape Coral, pets have been disappearing, feral cats
are relatively rare, and residents tell tales of monitors
eating rabbits in their yards and goldfish in their
ponds. In their native range, Nile Monitors are gen-
eralist carnivores that will take snails, spiders, crus-
taceans, insects, fish, amphibians, reptiles, birds, bird
eggs, and mammals. Their diet changes with age
from crabs and other invertebrates to vertebrates
and carrion. They can dig their own burrows, but
prefer to sequester an existing burrow after making
a meal of the resident. These intelligent, stealthy
predators are at home above and below ground, in
water, and in trees. The potential for impact on
native species is not yet known, but a few legally
protected taxa may be particularly vulnerable.

Cape Coral has a notoriously large population of
Burrowing Owls, a small species of terrestrial owl
that digs burrows in open habitats and canal banks.
The eggs and hatchlings of the Gopher Tortoise,
another burrowing species, may be vulnerable to
adult monitors. Nile Monitors compete with and
consume Dwarf Crocodiles in their native haunts,
suggesting that American Alligators could be at risk.
Nile Monitors also harbor introduced parasites that
could be transmitted to other vertebrates and even
humans. 

In July 2003, I initiated a research program at
the University of Tampa with funding from the
Charlotte Harbor National Estuary Program and the
National Fish and Wildlife Foundation. With the help
of local residents, lizards are being located, trapped,
and ethically euthanized to obtain information about
their current geographic distribution, density, natural
history, reproductive cycle, diet, and impact on native

species — and to assess the potential for range
expansion and the possibility of eradicating this
species from the area. Total eradication may prove
unfeasible, but the knowledge gained will assist in
managing populations of this and other introduced
carnivorous lizards in Florida and elsewhere.

References
Bennett, D. 1995. Little Book of Monitor Lizards. Viper Press.

Burridge, M. J., L. A. Simmons, and S. A. Allan. 2000.
Introduction of potential heartwater vectors and other exotic
ticks into Florida on imported reptiles. Journal of Parasitology
86:700–704.

de Buffrénil, V. and G. Hémery. 2002. Variation in longevity,
growth, and morphology in exploited Nile Monitors (Varanus
niloticus) from Sahelian Africa. Journal of Herpetology
36:419–426.

de Buffrénil, V., C. Chabanet, and J. Castanet. 1994.
Preliminary data on dimensions, growth and longevity of mon-
itor lizard Varanus niloticus in Lake Chad area. Canadian
Journal of Zoology 72:262–273.

Lenz, S. 1995. The biology and ecology of the Nile Monitor,
Varanus niloticus (Linnaeus 1766) in Gambia, West Africa.
Mertensiella 5:1–256 (in German).

Losos, J. B. and H. W. Greene. 1988. Ecological and evolution-
ary implications of diet in monitor lizards. Biological Journal of
the Linnaean Society 35:379–407.

Luiselli, L., G. C. Akani, and D. Capizzi. 1999. Is there any inter-
specific competition between Dwarf Crocodiles (Osteolaemus
tetraspis) and Nile Monitors (Varanus niloticus) in the swamps
of central Africa? Journal of Zoology, London 247:127–131.

All photographs by the author.

The author with the first Nile Monitor to trapped in his
attempt to eradicate the species from Cape Coral.

Nile Monitors patrol regular pathways and excavate bur-
rows along artificial canal banks in Cape Coral, but also
cross the canals and enter the surrounding natural man-
grove habitats in the Charlotte Harbor Buffer Preserve.




