|
Species Description:
The brown anole Anolis sagrei is small, semi-arboreal
("trunk-ground") lizard with relatively long toes and reduced toe
pad surfaces (relative to congeners), well suited for running and
jumping (Williams 1983, Campbell 2002).
Color is variable, ranging from light gray to brown to almost
black, commonly with irregular patches or mottled patterns,
spots, chevrons and a series of light-colored lines. The tail is
somewhat laterally compressed. A prominent identifying feature of this species is the extensible
dewlap or throat fan which can be yellow to red-orange in color
and is used in territorial and mating displays.
Sexual dimorphism is pronounced with males reaching a larger
terminal size and weight (see below). The dewlap of males
is also usually larger than that of the females. Female brown
anoles often exhibit a dorsal line that can appear as a
light-colored wave, zig-zag or diamond pattern that males
typically lack. Mature males also exhibit a pronounced
crest-like ridge running down the back (Williams 1983, Campbell
2002).
Potentially Misidentified Species:
Anolis carolinensis, the southeastern US native green anole, is
slightly smaller and more delicate in build, with a longer and
more slender head and snout. Anolis carolinensis is capable of
impressive color change from bright green to brown to nearly
black, but is still recognizable as distinct from Anolis sagrei.
A number of other Anolis lizard species not native to the United
States (e.g., the knight anole A. equestris, bark anole A.
distichus, and others) now occur in Florida, most notably around
Miami (Rocus and Mazzotti 1996). These lizards can be difficult for
untrained individuals to recognize as distinct from Anolis sagrei,
particularly A. distichus which looks quite similar but does not
grow as large and is more strictly arboreal in habit.
II. HABITAT AND DISTRIBUTION
Regional Occurrence:
Genus Anolis belongs to the New World lizard family Polychrotidae
and encompasses more than 300 species of diurnal, arboreal to
semi-arboreal primarily insectivorous lizards (Frank and Ramus
1995). The genus is native to the islands of the Caribbean and
mainland South and Central America, with only the green anole
(Anolis carolinensis) occurring as a temperate North American
native (Schwartz and Henderson 1991).
Anolis sagrei is native to Cuba, the Bahamas, and nearby islands.
Six distinct subspecies have been identified, including the
principal subspecies of Cuba (Anolis sagrei sagrei) and the
Bahamas (A. sagrei ordinatus) (Schwartz and Henderson 1991).
The range of the brown anole in the eastern United States
includes all of peninsular Florida (SREL).
The brown anole has been described as a habitat generalist that
generally prefers open vegetation within disturbed sites and
urbanized areas (Campbell 2002). It spends most of its time on
the ground or on trees at trunk level up to several feet off the
ground (Williams 1969).
IRL Distribution:
A. sagrei can be found throughout the Indian River lagoon
watershed, including populations that inhabit most of the IRL
spoil islands.
III. LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan:
Adult male Anolis sagrei reach a snout-to-vent length of more than 6
cm and a weight of 6-8 g. Females rarely exceed 5 cm and 3-4 g
(Campbell 2002).
Maturation occurs rapidly with individuals becoming
reproductively active by their second summer and pronounced adult
mortality the following winter. Published reports suggest the
species in Florida has a maximum life span of less than 18 months
although some reports suggest individuals may live twice as long.
(King 1966, Lee et al. 1989).
Abundance:
In areas where this exotic species has become established, it is
very often the most abundant reptile species present. Anolis sagrei
is among the most abundant lizards throughout Florida (SREL).
Reproduction:
Breeding in Florida populations of adult brown anoles occurs in
spring and summer with individuals establishing breeding
territories in March or April and defending them for the next
five to six months (Lee et al. 1989). Territorial fighting in males is fierce, with combatants
repeatedly fighting by locking jaws and knocking one another from
their perch (Estrada and Rodriguez 1986). During the breeding
season, males display their extended dewlaps as a component of
agonistic same-sex interactions and also in courtship behavior
directed toward females (West-Eberhard 1983).
Gordon (1956) reported that females lay single eggs approximately
every week throughout the breeding season, but other references
indicate that two eggs per clutch is typical. Oviposition
alternates between the left and right ovaries with each clutch
(Gordon 1956).
Embryology:
The eggs are typically laid under decaying vegetation on the
ground and hatch within 60-90 days (Corkscrew Swamp Sanctuary
Guide to Common Lizards), as opposed to an approximate 1-month
incubation period for greens anole eggs. Hatchlings emerge at
about 15-18 mm snout-to-vent length beginning in June (Duellman
and Schwartz 1958).
IV. PHYSICAL TOLERANCES
Temperature:
Like all reptiles, the brown anole is a poikilotherm that relies
on external warmth to raise its body temperature and employs
behavioral thermoregulatory techniques (i.e., basking) to
maintain its body temperature within acceptable limits.
The northern limits of the brown anole in the United States, into
central Georgia, appear to be temperature related; cold winters
are capable of reducing population densities in the northern
portions of their range (Campbell 1996, Parmley 2002).
V. COMMUNITY ECOLOGY
Trophic Mode:
Natural dietary items of these generalist predators include
arthropods, worms and molluscs (Campbell 2002). Cannabalism of adult
Anolis lizards on their hatchlings is also well documented, and this
behavior may be prevalent in A. sagrei (Cochran 1989, Nicholson et al. 2000).
VI. INVASION INFORMATION
Invasion History:
The brown anole was first documented in the Florida Keys in the
1880s. By the 1940s the species had also become
established on the Florida mainland (Campbell 2002). Lee
(1985) concludes that introduction to peninsular Florida in the
1940s occurred on at least six different occasions.
By 1980 established brown anole populations existed in all or most
of Florida's large urban centers south of Gainsville (Lee 1985).
The Florida range of this species continues to expand into the
northernmost and panhandle counties and populations have also
become established in Georgia, Louisiana, and near Houston, TX.
Accidental transport via motor vehicles and as accidental
introductions (particularly as eggs) with transported live plants
has been suggested as the likely source of these introductions
(Campbell 1996, Corkscrew Swamp Sanctuary Guide to Common Lizards).
Although both the Cuban and Bahamian subspecies have been
introduced to Florida, the genetic identies of these distinct lines
has been lost through outcrossing (Lee 1985).
Campbell (2002) notes that the species has also been introduced
into Hawaii and Jamaica, and Green et al. (2002) and Kolbe et al.
(2004) report their presence in Granada. The ISGG database additionally includes Belize, Mexico, and Taiwan as part
of the brown anole's alien range and lists Guam as a country into
which the species was introduced but whose subsequent establishment
was intercepted.
Potential to Compete With Natives:
The first anecdotal suggestions implicating the exotic brown anole
in the decline of native green anole populations in Florida were
published in the 1960s (Collette 1961, King and Krakauer 1966).
Direct studies of interspecific associatiosns between the two
congeners appear much less significant than intraspecific
(within-species) competitive interactions within these aggressive,
territorial animals (Brown and Echternacht 1991).
Field observations and experimental manipulations have demonstrated
that brown anoles in Florida prey directly on other small
vertebrates including hatchlings of the native green anole.
(Campbell 2000, Campbell and Gerber 1996). Campbell (2000)
reported that adult green anoles also consume brown anole
hatchlings. The lack of documented among-species interactions
notwithstanding, Campbell (2000) reports that where Anolis sagrei and
Anolis carolinensis populations co-occur Anolis carolinensis individuals
shift their spatial niche upward to occupy arboreal perches from
trunk to tree canopy, abandoning the ground perches they otherwise
also utilize when populations occur in the absence of Anolis sagrei.
The author speculates that this spatial shift may lead to a change
in the number and types of prey available to native Anolis carolinensis
populations.
Wardle (2002) reports that Anolis sagrei feeding activity is capable of
reducing the numbers and diversity of spiders on which they prey,
although Cambell (2006) has suggested that the overall impact of
the species on prey populations is probably too small to be
considered economically important.
Possible Economic Consequences of Invasion:
No steps have been taken to eradicate or control brown anoles in
Florida, and the abundance, fecundity, and generalist habits
exhibited by the species make it highly unlikely that eradication
could ever be achieved (Campbell 1999, 2002).
VII.
REFERENCES
Brown P.R. and A.C. Echternacht. 1991. Interspecific behavioral interaction of
adult male Anolis carolinensis (Sauria: Iguanidae): A preliminary field
study. Anolis Newsletter IV:21-30.
Campbell T.S. 1996. Northern range expansion of the brown anole Anolis
sagre in Florida and Georgia. Herp. Review 27:155-157.
Campbell T. S. 1999. Consequences of the Cuban brown anole invasion: it's not
easy being green. Anolis Newsletter V:12-21.
Campbell T.S. 2000. Analyses of the effects of an exotic lizard (Anolis
sagrei) on a native lizard (Anolis carolinensis) in Florida, using
islands as experimental units. Unpublished Ph.D. Dissertation, University of
Tennessee, Knoxville, TN.
Campbell T. 2002. The Brown Anole (Anolis sagrei Dumeril and Bibron 1837). The
Institute for Biological Invasions: The Invader of the Month, February 2001.
(Available online here).
Campbell T.S and G. Gerber. 1996. Natural History: Anolis sagre:
Saurophagy. Herp. Rev. 27:106.
Cochran P.A. 1989. Anolis sagrebehavior. Herp. Rev. 20:70.
Collette B.B. 1961. Correlations between ecology and morphology in anoline
lizards from Havana, Cuba and southern Florida. Bull. Mus. Comp. Zool.
125:137-162.
Corkscrew Swamp Sanctuary Guide to Common Lizards. Published online by National Audubon Society.
Duellman W.E. and A. Schwartz. 1958. Amphibians and reptiles of southern
Florida. Bulletin of the Florida State Museum 3:181-324.
Frank N. and E. Ramus. 1995. A Complete Guide to Scientific and Common Names
of Reptiles and Amphibians of the World. NG Publishing inc., Pottsville, PA.
377 p.
Estrada A.R. and Novo Rodriguez J. 1986. Subnicho estructural de Anolis
sagrai en Cayo InŽs de Soto Cuba. Analisis intra-y extraboblacional.
Poeyana 320:1-13.
Gordon R.E. 1956. The biology and biodemography of Anolis carolinensis
carolinensis Voigt. Unpublished Ph.D. Dissertation. Tulane University, New
Orleans LA.
Greene, B. T., D. T. Yorks, J. S. Parmerlee, R. Powell, and R. W. Henderson.
2002. Discovery of Anolis Sagrei in Grenada with Comments on Its
Potential Impact on Native Anoles. Carribean Journal of Science 38:270-272.
King W. and T. Krakauer. 1966. The exotic herpetofauna of southeast Florida.
Quart. J. Florida Acad. Sci. 29:144-154.
Kolbe J.J., Glor R.E., Schettino L.R., Lara A.C., Larson A., and J.B. Losos.
2004. Genetic variation increases during biological invasion by a Cuban lizard.
Nature 431:177-181.
Lee J.C. 1985. Anolis sagrei in Florida: Phenetics of a colonizing
species I. Meristic characters. Copeia 1985:182-194.
Lee J.C., Clayton D., Eisenstein S., and I. Perez. 1989. The reproductive cycle
of Anolis sagrei in southern Florida. Copeia 1989:930-937.
Nicholson K.E.,. Paterson A.V, and P.M. Richards. 2000. Anolis sagrei
(brown anole) cannibalism. Herpetological Review 31:173-174.
Parmley D. 2002. Northernmost record of the brown anole (Anolis sagrei)
in Georgia. Georgia Journal of Science 4:191.
Rocus D.S. and F.J. Mazzotti. 1996. Reptiles of Southern Florida. UF/IFAS
Florida Cooperative Extension Service document WEC71.
Schwartz A. and R.W. Henderson. 1991. Amphibians and reptiles of the West
Indies: descriptions, distributions, and natural history. University of Florida
Press, Gainesville.
SREL (online). Lizards of South Carolina and Georgia University of Georgia
Savannah River Ecology Laboratory, Herpetology program.
Wardle D.A. 2002. Islands as model system for understanding how species affect
ecosystem properties. Journal of Biogeography 29:583-591.
West-Eberhard M.J. 2983. Sexual Selection, Social Competition, and Speciation.
Quarterly Review of Biology 58:155-183.
Williams E.E. 1969. The ecology of colonization as seen in the zoogeography of
anoline lizards on small islands. Quart. Rev. Biol. 44:345-389.
Williams E.E., 1983. Ecomorphs, faunas, island size, and diverse endpoints in
island radiations of Anolis. In R. B. Huey, E. R. Pianka, and T. W.
Schoener (eds.), Lizard Ecology: Studies of A Model Organism. pp. 326-370.
Harvard University Press, Cambridge, Massachusetts.
Report by:
J. Masterson, Smithsonian Marine Station
Submit additional information, photos or comments
to:
irl_webmaster@si.edu
Page last updated: June 12, 2007 |
