Activity Patterns of Green Iguana (Iguana Iguana)

ACTIVITY PATTERNS OF GREEN IGUANA (IGUANA IGUANA)

AT HUGH TAYLOR BIRCH STATE PARK, FORT LAUDERDALE, FLORIDA

Stacey R. Sekscienski

A Thesis Submitted to the Faculty of

The Charles E. Schmidt College of Science

in Partial Fulfillment of the Requirements for the Degree of

Master of Science

Florida Atlantic University

Boca Raton, Florida

December 2012

ACKNOWLEDGEMENTS

I am greatly indebted to Hank Smith, whose passion for life and herpetology sustained me through this project. I thank my committee, Dr. Jon Moore, Dr. Dale

Gawlik, and Dr. Erik Noonburg, for their guidance and support throughout this project and Walt E. Meshaka Jr. for his encouragement. This study would not have been possible without the support of the Florida State Park Service and Parknership Program, Jim

Gibson, Mark Foley, and all of the staff and volunteers at Hugh Taylor Birch State Park.

Not only did they support this research, but they accepted me as one of their own. I am extremely grateful to Trudi Stevenson, Connie Theis, Gregg Sekscienski, Heather

Parmeter, Robert Stevenson, Dr. Teresa Randall, Steve Gooch, and Oklahoma City Zoo staff for their continued encouragement and support throughout this project. Additionally,

I thank Heather Cress, Russ Mapp, Sandy Jensen, and Steve Crossett for assistance in data collection as well as Dr. Tracy Morris, Faten Alamri, Kristin Laurie, and Monica

McGarrity for statistical advisement. Research was made possible under Florida DEP

Division of recreation and Parks permit number 5-06-80.

ABSTRACT

Author: Stacey R. Sekscienski

Title: Activity Patterns of Green Iguana (Iguana iguana) at Hugh Taylor Birch State Park, Fort Lauderdale, Florida

Institution: Florida Atlantic University

Thesis Advisor: Dr. Jon Moore

Degree: Master of Science

Year: 2012

Activity patterns of Iguana iguana from two locations within Hugh Taylor Birch

State Park, Fort Lauderdale, Florida were documented and examined. Between May 1,

2006 to April 20, 2007, I. iguana were observed on a routine basis and activities were documented as one of six major activity categories (basking, locomotion, foraging, resting, visual signaling, and other). Data was analyzed to determined differences between activity patterns of I. iguana relative to sites, seasons, and size category within the park. Iguana iguana spent more time basking at Site 1 than Site 2. Size 4 animals which consisted of dominant adult males, spent more time basking than other males and adult females. Size 4 animals also spent less time foraging than hatchlings, juveniles, and other adults. These results complement the existing research on behavior of I. iguana and may be useful in determining invasive control efforts of I. iguana in Florida.

DEDICATION

Henry T. “Hank” Smith

ACTIVITY PATTERNS OF GREEN IGUANA (Iguana Iguana) AT HUGH TAYLOR

BIRCH STATE PARK, FORT LAUDERDALE, FLORIDA

List of Tables ...... vii

List of Figures ...... viii

Introduction ...... 1

Distribution and Diet ...... 1

Behavioral Patterns ...... 2

Effects of Non-Native Species ...... 7

Iguana Iguana in Florida ...... 8

Hypotheses ...... 13

Objectives ...... 14

Methodology ...... 15

Research Site ...... 15

Data Collection ...... 21

Statistical Analysis ...... 25

Results ...... 26

Discussion ...... 36

References ...... 45

LIST OF TABLES

Table 1: Behavioral categories of Iguana iguana ...... 23

Table 2: MANOVA results with respect to site and size...... 28

Table 3: Summary statistics for activities at study sites ...... 28

Table 4: Summary statistics for size categories ...... 29

Table 5: Summary statistics for each combination of site and size ...... 30

Table 6: Mean temperatures in °C between sites across seasons ...... 31

Table 7: Plants consumed by Iguana iguana ...... 41

vii

LIST OF FIGURES

Figure 1: Aerial map of study sites at Hugh Taylor Birch State Park ...... 17

Figure 2: Habitat classifications within Hugh Taylor Birch State Park ...... 18

Figure 3: Burrows at Study Site 1 (Seawall) ...... 19

Figure 4: Study Site 1 (Seawall) ...... 20

Figure 5: Study Site 2 (Lagoon) ...... 20

Figure 6: Observation blind at Study Site 1 (Seawall) ...... 24

Figure 7: Observation blind at Study Site 2 (Lagoon) ...... 24

Figure 8: Percentage of time each activity performed at each site ...... 31

Figure 9: Percentage of time each activity performed by each size category ...... 31

Figure 10: Percentage of time each activity performed (Site 1) ...... 32

Figure 11: Percentage of time each activity performed (Site 2) ...... 32

Figure 12: Percentage of time each activity performed (Size 2/Site 1)...... 33

Figure 13: Percentage of time each activity performed (Size 2/Site 2) ...... 33

Figure 14: Percentage of time each activity performed (Size 3/Site 1)...... 34

Figure 15: Percentage of time each activity performed (Size 3/Site 2)...... 34

Figure 16: I. iguana utilizing sun-shade mosaic at Site 1 (Seawall) ...... 42

Figure 17: Three smaller adult male I. iguana. Study Site 1 (Seawall) ...... 43

Figure 18: Two dominant male I. iguana. Study Site 2 (Lagoon)...... 43

viii

INTRODUCTION

Iguana iguana

The green iguana (Iguana iguana) is one of the most identifiable and charismatic members of the lizard family Iguanidae. Eight extant genera encompassing 35 species share this family with I. iguana including the closely related taxa, Cyclura (Weins and

Hollingsworth 2000, Frost et al. 2001). Members of this herbivorous clade share three derived and distinct morphological characters: large bodies; transverse folds or valves in the colon; and flared and polycuspate marginal teeth (Etheridge and de Quieroz, 1988).

Distribution and Dietary Preference

The historic geographic range of the green iguana, Iguana iguana, extends south

from northern Mexico, through Central America to the Tropic of Capricorn in South

America (Etheridge 1982). While there are few accounts of I. iguana on Pacific islands,

its presence on islands in the western and southern Caribbean and in the Lesser Antilles is

prominent (Lazell 1973, Etheridge 1982). In its native range, this lizard thrives in coastal,

as well as riparian habitats (Rand et al. 1989, Alvarado et al. 1995).

Most researchers suggest I. iguana is exclusively herbivorous (Iverson 1982,

McBee and McBee 1982, Rand et al. 1990, van Marken Lichtenbelt 1993). Iverson

(1982) describes I. iguana as a “true herbivore” feeding primarily on fruits, flowers,

seeds, and foliage. Dietary shifts in iguanids are uncommon (Troyer 1984b, Durtsche

2000). Studies of marine and Galapagos land iguanas did not reveal dietary shift in those

species. However, Troyer (1984b) showed young I. iguana selecting leaves with higher

protein content and Durtche (2000) found that Ctenosaura pectinata shifted their

preference from insects to plants. While a distinct dietary shift has not been proven in I. iguana, there have been multiple reports of carnivory in this species (Hirth 1963, Loftin

& Tyson 1965, Lazell 1973, Arendt 1986, Townsend et al. 2005). Hirth (1963) observed a juvenile iguana eating a grasshopper and in Panama, Loftin and Tyson (1965) observed large iguanas alongside vultures feasting on opossum carrion. Arendt (1986) observed a young iguana consuming cattle egret eggs out of a nest. Because of the peripheral location of the nest to the main nesting colony and the condition of the eggs, he concluded that this was a case of sanitary predation—not true predation. Townsend et al.

(2005), documented snail consumption in two animals. While, accidental consumption was suspected in one animal due to the vegetative material found in the stomach, the other animal examined only contained snails. Most recently on Big Pine Key, Florida,

Anderson & Enge (2012) recorded several I. iguana feeding alongside black spiny-tailed

iguana (Ctenosaura similis) and turkey vultures (Cathartes aura) on a Key Deer

(Odocoileus virginianus clavium) carcass.

Behavioral Patterns

Pristine as well as disturbed habitats can contain a variety of microhabitats which

often influence the behaviors of the animals living within these habitats (Adolf 1990,

Diaz 1997, Whitaker and Shine 2002). Thermoregulatory behaviors of ectothermic

animals, such as lizards, have been strongly correlated with the delineation of

2 microhabitats within the activity space of a given species (Heatwole 1970, Adolf 1990).

Even within a microhabitat, a species’ niche may be compartmentalized according to size or life stages of that specific animal. At a site in Mexico, McGinnis and Brown (1966) reported adult I. iguana utilizing adaptive thermoregulatory behavior to avoid temperatures above 41°C ± .5°C. Juveniles avoided sunlit areas when temperatures rose above 35°C ± 1°C. Wild adult iguanas preferred sun-shade mosaic and only occasionally used fully sunlit areas for basking (McGinnis and Brown 1966). While temporal variation within a given microhabit can influence thermoregulation of ectotherms, it is only one of several factors that may influence activity patterns of a species (Adolph 1990, Diaz 1997).

In their historic range, active behaviors of I. iguana are influenced by seasonal and daily variations in weather, patterns of food availability, predator avoidance as well as the animal’s sex, size, and social status (Greene et al. 1978, Dugan 1980, Rodda 1992).

Van Devender (1982) revealed that adult I. iguana prefer basking/sleeping sites higher in the canopy, whereas juvenile I. iguana remained on or near the ground. On the island of

Curacao, I. iguana were observed sleeping on steep walls, in shrubs, and in crevices (van

Marken Lichtenbelt et al. 1997), while on Barro Colorado Island, Panama (Burghardt and

Rand 1985), most iguanas were found sleeping 1-4 m above ground on exposed tree branches. These very different choices in sleeping sites between these two locations suggest a level of behavioral flexibility within this species and that sleeping locations of

I. iguana are likely influenced by the overall local geography and availability of “predator safe” areas within those environments.

Nesting sites can also be dependent on location and vary from communal areas or

solitary locations (Rand 1968, Bock and Rand 1989, Rand and Dugan 1983, van Marken

Lichtenbelt and Albers 1993). However, nesting does appear to be highly synchronous

within a given habitat (Bock and Rand 1989). Reproductive cycles are most likely

determined by seasonal rainfall events unique to the location (Hirth 1963, Bock and Rand

1989, van Marken Lichtenbelt and Albers 1993). In most of its native range, mating activities of I. iguana occur at the onset of the dry season during the months October to

January (Dugan 1980, Rand and Greene 1982). In Panama, egg laying occurs at the end

of the dry season from February to March (Swanson 1950, Hirth 1963, Dugan 1980,

Rand and Greene 1982). In the Lesser Antilles, nesting occurs from December to

February (Lazell 1973). In most of its tropical range, hatching is synchronous with the

rainy season, and can begin as early as April (Dugan 1980, Rand and Greene 1982).

However, in areas where dry seasons are somewhat non-existent, Rand and Greene

(1982) suggest the possibility of a second mating cycle.

Since 1980, several studies have addressed activity patterns of I. iguana. Dugan

(1980) examined behaviors of feeding, perch changing, headbobbing, and social interactions for I. iguana and found that when awake, individuals were inactive more than

90% of the time. Van Marken Lichtenbelt and colleagues (1993) analyzed time and

energy budgets of I. iguana on Curacao and found a similar annual level of energy

expenditure in males and females but differences in the allocation of that energy. Males

allocated more time to social or territorial activities compared to females, which

dedicated more energy toward egg production and laying. Dugan (1980) suggests that

4 while energy demands strongly influence behavior, social demands should also be examined when determining cause-effect relationships. Native colonies of Iguana iguana exhibit distinct social patterns (Dugan 1980, Mora 1991, Pratt et al. 1992, Rodda 1992,

Phillips et al. 1993, van Marken Lichtenbelt et al. 1993). For I. iguana, these social interactions begin when the hatchlings leave the nest (Burghardt 1977, Burghardt et al.

1977, Mora 1991, Troyer 1984a, Troyer 1984c). Mora (1991) showed in Costa Rica, that

I. iguana hatchlings clearly exhibit social behavior when emerging from the nest and when resting together. A proposed explanation of this “group emergence” behavior is that predation is minimized when hatchlings travel as a group to more camouflaged surroundings (Mora 1991). Shortly after emergence, hatchlings spend time locating and consuming the feces of adult animals, inoculating themselves with microbial flora necessary in the digestion of plant matter (Troyer 1983, Troyer 1984c). However, Troyer

(1984a, 1984c) suggests that this physiological need to acquire microbial flora from older animals, which facilitates contact with other individuals in the population, could be considered as the catalyst for the evolution of social behavior in I. iguana.

Larger male I. iguana hatchlings exhibit dominance at an early age by commanding premium basking sites (Phillips et al. 1993). Because temperature affects digestion in these animals, young male iguanas that dominate superior basking sites have increased digestion when compared to subordinates, grow faster, and most likely continue on to become the dominant males in a population (Phillips et al. 1993). Dugan

(1980) revealed that on Flamenco Island, Panama, I. iguana groups exhibit a hierarchical social structure in which a territory consists of a dominant male accompanied by one or

more females, and the occasional peripheral male. Suprisingly, Dugan (1982) and Pratt et al. (1992) documented much smaller home ranges for the dominant males than for smaller males. One explanation for these findings is that dominant males have access to one or several premium basking sites and display perches within these ranges (Dugan

1982, Pratt et al. 1992). Rodda (1992) studied the mating behaviors of I. iguana in

Venezuela and compared the social behaviors of Panamanian iguanas to Venezuelan

iguanas and found just as many differences as similarities. One such difference revealed

in the Venezuelan study was the presence of interfemale competition for males. Rodda

(1992) also observed males mating multiple times within a 24-hour period, whereas

Dugan (1980) claimed the Panamanian male iguanas only mated once a day.

Several studies have examined the effects of physical environment on mating and

other behaviors of iguanids (Heatwole 1970, Dugan and Wiewandt 1982, Christian et al.

1983, Grant and Dunham 1988, Adolph 1990, Rodda 1992, Gier 2003). Gier (2003)

examined the influence of environmental factors on mating systems for two species of

iguanids, and found that spiny-tailed iguana (Ctenosaura similis) utilized burrows mostly

to escape predation while desert iguana (Dipsosaurus dorsalis) sought out cooler retreats to escape lethal temperatures. He concluded that each species has a set of resources unique to that environment and that the resource most narrowly distributed within that space most influences the mating system of the given species. Because ectothermic animals must thermoregulate to survive, partitioning of temporal space within a given environment should be given equal consideration to partitioning of food resources when examining interspecific resource consumption (Magnuson et al. 1979). Like other

ectotherms, iguana behavior is heavily influenced by the temporal boundaries of the

resident landscape (Magnuson et al.1979, Gier 2003, Phillips et al. 1992, Pratt et al.1992,

Rodda 1992, Meek 1995). Iguanids use both conduction and absorption to raise body temperature and when needed, retreat to shade, burrows, or cooler surfaces to lower body temperature (Bogert 1949, Heatwole 1970, Dugan 1980, Christian et al. 1983, Phillips et al. 1992, Rodda 1992).

Effects of Non-native Species

Whether all introduced species should be deemed pest species and potentially harmful to habitats in which they are non-native is debatable (Van Driesche and Van

Driesche 2000). The introduction and colonization by many non-native species has been an artifact of human exploration and colonization (Gordon and Thomas 1997, Van

Driesche and Van Driesche 2000). With the advent and continuous modernization of transportation modes, humans have, in effect, facilitated the spread of exotic species around the globe with many of the earliest introductions occurring unintentionally via ocean-going vessels, resulting in the spread of exotic species from one continent to another (Van Driesche and Van Driesche 2000). The term “biological invasion” implies some negative effect on the invaded community. For most, it is assumed that if colonization is successful, introduced species will eventually have a negative impact on native species through direct effects such as competitive exclusion, introduction of disease, modification of habitats, hybridization, and/or predation (Butterfield et al. 1997,

Van Driesche and Van Driesche 2000). While most research of invasive species has addressed biologic and economic impacts, less is known about the indirect and

synergistic effects non-native species have on native communities (Van Driesche and

Van Driesche 2000).

Iguana iguana in Florida

Whether an introduced species exhibits the full diversity of behavior and ecology

of its natural populations may be critical to long-term survival of endangered or threatened related species (Martins 2004). By determining behavioral nuances among related iguanid species, more educated conservation strategies may be employed when reintroduction of threatened or endangered species is possible (Goodman et al. 2005,

Powell 2006, Meshaka et al. 2009). Furthermore, examining trophic interactions between native and non-native species can reveal how interwoven competitive mechanisms are with regards to the success of the non-native species (Smith et al. 2006, Meshaka et al.

2009). Until recently, most research conducted on non-native reptiles in Florida has been to distinguish geographical distributions (King and Krakauer 1966, Simberloff 1997,

Meshaka et al. 2004a, Smith et al. 2006, Krysko et al. 2007, Meshaka et al. 2009,

Meshaka 2011).

Iguana iguana is an introduced species in Florida with numerous documented accounts of established colonies (Townsend et al. 2003, Meshaka et al. 2004a, 2004b,

Krysko et al. 2007). I. iguana has yet to be deemed “invasive” by government officials

(USDA 2012) probably due to the lack of research of the effects of I. iguana on native communities (Simberloff 1997). However, Dalrymple (1994) lists I. iguana as an invasive

non-indigenous species in Florida and the Global Invasive Species Programme (GISP)

managed by the IUCN includes I. iguana in their invasive species database (GISP 2012).

I. iguana was first documented in Florida over 30 years ago and its origination and

subsequent establishment is thought to have occurred as a result of an increase of stowaways and in the accidental and intentional release of captive animals (King and

Krakauer 1966, Meshaka et al. 2004a, 2004b). They are well suited for South Florida’s

tropical climate and are particularly successful in highly disturbed or urban types of

environments where ornamental/non-native plants abound and native predators and

potential competitors are largely absent (King and Krakauer 1966, Meshaka et al. 2004b).

Unlike some native insular habitats of I. iguana, such as Curacao (van Marken

Lichtenbelt 1993), South Florida’s urban environments also provide numerous, reliable,

and accessible freshwater sources which facilitate the survival of this species in these

areas (Meshaka et al. 2004b). Iguana iguana are reliably found near bodies of water, i.e.,

ponds, canals, and ditches but seem to be most populated along the coast where

temperatures remain mild (Meshaka et al. 2004b, Mckie et al. 2005, Krysko et al. 2007).

Along a freshwater canal in Broward County, Florida, Sementelli et al. (2008) reported a

burrow density of 1,794 per ha for a colony of I. iguana. There is looming concern that

the burrowing behavior of I. iguana may have negative effects on the structural

infrastructure of both freshwater canals and seawalls (Sementelli et al. 2008a and b,

Engeman et al. 2012). As in their native regions (Alvarado et al. 1995), I. iguana

routinely bask or take shelter on vegetation adjacent to or hanging over the water

(Meshaka et al. 2004b, R. Mapp pers. comm. 2005, Sekscienski pers. obs. 2006). The

network of man-made canals of which South Florida is so well known, facilitates the

dispersal of I. iguana in this environment (Krysko et al. 2007).

Since the 1960’s, Iguana iguana have been documented in at least twelve counties

in Florida with colonies documented in several state parks along Florida’s southeast coast

and in the Florida Keys including Cape Florida State Park and Oleta River State Park in

Miami-Dade County and Hugh Taylor Birch State Park (HTBSP) in Broward County

(Townsend et al. 2003, Meshaka et al. 2004a, 2004b, Krysko et al. 2007). In Florida,

documented predators of I. iguana include the domestic dog (Canis familiaris) (Meshaka

et al. 2004a), yellow-crowned night heron (Nyctanassa violacea) (Engeman et al. 2005a),

Florida burrowing owl (Athene cunicularia floridana) (Mckie et al. 2005), and the

raccoon (Procyon lotor) (Smith et al. 2006). Most recently, a North American river otter

(Lontra canadensis) was photographically captured consuming an I. iguana in it’s enclosure at Flamingo Gardens and Everglades Sanctuary in Davie, Florida (J. P. Carter, pers. comm. 2012). On separate occasions, staff of Flamingo Gardens and Everglades

Sanctuary in Davie, Florida have observed North American river otter (Lontra canadensis), great blue heron (Ardea herodias), and red-tailed hawk (Buteo jamaicensis) predating I.iguana (M. Ruggeiri, pers. comm. 2012).

In recent years, effects of Iguana iguana on Florida’s native flora and fauna have become more evident (Mckie et al. 2005, Townsend et al. 2005, Krysko et al. 2007,

Truglio et al. 2008, Daniels pers. comm. 2012). Mckie et al. (2005) documented Florida burrowing owls (Athene cunicularia floridana) consuming juvenile I. iguana in an area where competition for premium nesting/burrowing sites most certainly occurred between the two species. In the same locality of the studied burrowing owl colony, Truglio et al.

(2008) reports I. iguana damaging gopher tortoise (Gopherus polyphemus) burrows.

Iguana iguana have been observed foraging on nickerbean (Caesalpinia bonduc) in

remaining localities of the endangered Miami blue butterfly (Hemiargus thomasi

bethunebakeri) (Krysko et al. 2007, Sekscienski pers. obs. 2010, Daniels pers. comm.

2012). Interestingly, many of these iguana colonies occur in disturbed areas which may

already be unsuitable for native fauna (Meshaka et al. 2004b).

Reproductive cycles of the Iguana iguana in Florida are probably quite similar to those of their native counterparts; although, more research is needed to support this idea.

Krysko et al. (2007) documented I. iguana breeding behavior from December through

April as well as an oviposition event in April. After a three-month incubation period,

from May to August, hatchlings emerge from nests (Swanson 1950, Townsend et al.

2003, Meshaka et al. 2004a, Krysko et al. 2007). Meshaka et al. (2004a), state that

iguanas were not abundant at HTBSP until after Hurricane Andrew in 1992 and in reality

were not present in noteworthy populations until after 1999 as supported by the 1999

HTBSP Park Management Plan. In fact, the population explosion of I. iguana seemed to

follow a raccoon removal project in 2000 in which 160 raccoons were removed from the

70ha park, a density of 238 raccoons/km2 (Smith and Engeman, 2002). Smith et al.

(2006a) and Meshaka et al. (2007) suggest that the increase in I. iguana population seen

after 2001 both at HTBSP and at Cape Florida State Park, resulted from a decrease in

predation pressure after intense removal efforts of raccoons at both sites. Smith et al.

2007 estimated that in 2003 at Cape Florida State Park, the population of I. iguana

escalated to 6.27 animals/ha. Iguana iguana are a non-native species in Puerto Rico,

where Figueiredo-de-Andrade et al. (2011), reported 32 animals/ha, a density five times

more than the amount reported by Smith et al. (2007).

Occasional freezing temperatures in Florida may be the only true population

control of I. iguana (King and Krakauer 1966, Campbell 2011, M. Foley pers. comm.

2012). In January of 2010, Florida was hit with record low temperatures (NOAA 2012).

HTBSP recorded a low of 1.7°C on January 11, 2010 and the park’s Iguana iguana population was severely impacted (M. Foley pers. comm. 2012). Park personnel collected numerous dead iguanas after the record event and none of the largest, territorial males have been seen since January 2010 (M. Foley pers. comm. 2012). In fact, since January of 2010 M. Foley (pers. comm. 2012) reports HTBSP personnel only observing, on average, one iguana every 3 months and only one hatchling has been seen since January of 2012. Deaths of I. iguana as well as a reduction in breeding activities were documented in Palm Beach County following the January 2010 cold weather event

(Campbell 2011). Mere removal of these exotic lizards may not be an adequate solution to the problem, as was observed at Cape Florida State Park after a mass removal of 1457 green iguanas between 2001 and 2006 (Townsend et al. 2003, E. Golden, pers. comm.

2007, Smith et al. 2007). The high density of lizards outside of the park’s boundaries may have supplied more individuals to fill the newly vacant spaces (Townsend et al. 2003).

This response is not surprising, since studies have shown that upon removal of older, dominant male iguanas, peripheral males move in quickly to establish dominance over that territory (Dugan 1982).

HYPOTHESES

1. There are significant differences between activity patterns of I. iguana relative

to location within Hugh Taylor Birch State Park.

2. There are significant differences in activity patterns between size classes of I.

iguana within Hugh Taylor Birch State Park.

3. There are significant differences between activity patterns of I. iguana relative

to season within Hugh Taylor Birch State Park.

OBJECTIVES

Activity patterns of Iguana iguana within Hugh Taylor Birch State Park in Fort

Lauderdale, Florida were examined relative to site, size class, and season. Data were

analyzed to determined differences between activity patterns of I. iguana between sites, seasons, and size category within the park. The results of this study complement the existing research on the behavior of I. iguana and may be useful in determining invasive control efforts of I. iguana in Florida.

METHODOLOGY

Research Site

Hugh Taylor Birch State Park (HTBSP) is located at latitude-longitude

coordinates of N 26.14536 and W -80.10504 on a barrier island in Fort Lauderdale,

Florida, and encompasses 70ha (Fig. 1). Originally purchased privately by Hugh Taylor

Birch in the early 1900’s, the land was donated as parkland to the public in 1942. This

urban park, sandwiched between the Atlantic Ocean to the east and the Intracoastal

Waterway to the west, is comprised of several types of biological communities and

includes one of the last remaining maritime hammocks in Southeast Florida (Fig. 2). In

addition to the forest, this relatively small area of land includes a freshwater lagoon

system and mangrove habitat. HTBSP is a popular recreational area among residents and

visitors. While the park supports many native plants and animals, it is continually

threatened by encroachment and establishment of exotic organisms as documented in the

park’s 2006 Unit Management Plan. Many of the exotic plants established in the park

today were planted for ornamental purposes in the early 1900’s. In addition to the

numerous non-native plants, many exotic animals inhabit HTBSP. Non-native animal

species most commonly observed include the Cuban treefrog (Osteopilus septentrionalis),

brown anole (Anolis sagrei), knight anole (Anolis equestris), bark anole (Anolis distichus), marine toad (Bufo marinus), and green iguana (Iguana iguana). Within the

park boundaries, there are five permanent residences along with several volunteer RV

sites, which are only occupied several months of the year.

As in their native regions (Alvarado et al. 1995), and throughout South Florida, I.

iguana at HTBSP frequent areas near bodies of water, where they routinely bask or take

shelter on vegetation adjacent to or hanging over the water (Meshaka et al. 2004b, R.

Mapp pers. comm. 2005, Sekscienski pers. obs. 2006). Additionally, throughout HTBSP,

many I. iguana are commonly seen utilizing open ground for foraging and basking

(Townsend et al. 2003, Meshaka et al. 2004a, 2004b, Sekscienski pers. obs. 2006,

Meshaka et al., 2009). A concrete seawall spans the western edge of the park along the

Intracoastal Waterway and offers numerous basking opportunities for I. iguana, as does the vegetation around the freshwater lagoon and on the spoil island at the north end of the lagoon. Additionally, along the seawall, multiple burrows are present and utilized frequently by I. iguana (Fig. 3). Two observational locations were established for this study. Site 1 (Seawall) was located on the South side of the park adjacent to the seawall in ruderal habitat (Fig. 4) and Site 2 (Lagoon) was located adjacent to the interior lagoon

in maritime hammock (Fig.5).

Site 1 (SW) Site 2 (LL)

Figure 1. Hugh Taylor Birch State Park, Fort Lauderdale, Florida, adapted from 2006 Park Management Report.

Figure 2. Major habitat classifications according to Florida Natural Areas Inventory from 2006 Park Management Report.

Figure 3. Iguana iguana burrows at Site 1 (Seawall). Hugh Taylor Birch State Park, Fort Lauderdale, FL.

Figure 4. Study Site 1 (Seawall), Hugh Taylor Birch State Park, Fort Lauderdale, Florida.

Figure 5. Study Site 2 (Lagoon), Hugh Taylor Birch State Park, Fort Lauderdale, Florida.

Size and Season

Size of individuals was documented as one of four categories: 1 = ≤15cm; 2 =

>15 – 30 cm; 3 = > 30 – 60cm; and 4 = > 60 cm. Seasons were divided into four

categories: 1= December 21 to March 20, 2= March 21 to June 20, 3= June 21 to

September 20, and 4= September 21 to December 20.

Temperature and Weather

At site 1 and site 2, temperature was recorded around-the-clock in 15-minute increments with HOBO dataloggers (Onset Computers, Falmouth, MA) from May 1,

2006 to May 8, 2007. Additionally, temperature and humidity measurements were collected at the beginning and at the termination of each observation period using a handheld thermo-hygrometer. Additional environmental conditions were recorded at the beginning and end of observational sessions including sky conditions and wind speed.

Sky conditions were categorized and recorded as: clear (no clouds visible) = 1, partly cloudy (less than 50% coverage) = 2, cloudy (>50% but

(mph) as 0 = 1, >0 – 5 = 2, >5 – 10 = 3, >10 – 20 = 4, or > 20 = 5. Current or recent precipitation was recorded as none = 1, during = 2, or previous 24 hours = 3.

Observations

Observational data were collected on the diurnal activity patterns of feral, non- native Iguana iguana at HTBSP and examined to determine activity patterns of iguanas at two designated sites within the park. Subsequent observations were made to supplement

the existing data and provide a seasonal description of behaviors. Data collection

occurred at two designated sites within the park on different days each month from May

1, 2006 to April 20, 2007. Data were collected in two- to eight-hour blocks of time, either

beginning with sunrise or ending with sunset. Visual barriers were utilized to minimize

observer effect (Martin and Bateson 1993). At Site 1 (Seawall) observations were

collected from a portable 1.8 x 1.5m blind (Fig. 6) and at Site 2 (Lagoon) observations were collected from a permanent park structure, where a makeshift blind was constructed for each observation period (Fig. 7). Binoculars or a spotting scope were used to observe subjects. Scan sampling and continuous recording methods (Martin and Bateson 1993) were used to locate, monitor, and document behavior of animal subjects. At 5-minute intervals, the site was scanned to detect new individuals and the behavior of individual animals was recorded continuously and categorized on a minute-to-minute basis (van

Marken Lichtenbelt et al. 1993). At any given time during the observation period, the observer monitored no more than five individual animals and animals were observed until they were out of sight of the observer or the session ended. During this study, an extensive array of detailed behaviors observed was used to create a behavioral ethogram with the following categories: basking, locomoting, foraging, resting, visual signaling, and other (Table 1). During field observations, time spent for each behavior was defined as the sum of those minutes in which the behavior actually occurred (van Marken

Lichtenbelt et al. 1993).

Table 1. Behaviors of I. iguana measured at Hugh Taylor Birch State Park, Ft. Lauderdale, Florida from 11 May 2006 to 20 April 2007.

Behavior Category Activities Included in Category Basking 1 Body stationary with any body part at least partially exposed to sunlight; on soil, concrete, wood, grass, or in tree; on belly or with forelegs extended Locomoting 2 Walking, sprinting, swimming Foraging 3 Tasting, eating, walking while eating Resting 4 Body stationary and completely in shade; eyes open/closed Visual 5 Headbob; shudder bob; head shake; arm waving Signaling Other 6 Drinking, defecating

During observation periods, preferred food types of iguanas were also documented.

When available, the stomach contents of iguanas found dead within the park boundary were examined to support observational data regarding dietary preferences.

Figure 6. Observation blind at Study Site 1 (Seawall), Hugh Taylor Birch State Park, Fort Lauderdale, Florida.

Figure 7. Observation blind at Study Site 2 (Lagoon), Hugh Taylor Birch State Park, Fort Lauderdale, Florida.

Statistical Analysis

For site and size separately, and for each combination of size and site, n, mean,

standard deviation, and range was computed. Differences in the vectors of mean proportions for activities 1 through 5 with respect to site and size were determined using

Wilks’ Lambda MANOVA. To determine the location(s) of significant differences

detected in the MANOVA, an ANOVA was performed for each activity, 1 through 5. To

determine any differences between temperature means for each season between sites,

ANOVA was performed. For site and size, a 2-factor ANOVA was performed to examine effects on activities. Tukey’s multiple comparison tests were performed to examine the

differences between all possible pairs of means of activities between size classes. Two- sample T-tests were performed on temperatures between sites and for each season. For all performed tests, p-values less than 0.05 were considered significant. Activity 6

(Other) was excluded from all analyses since only 5 of the 230 subjects analyzed were observed exhibiting behaviors in this category (Total=28 minutes). All data were analyzed using SAS® software, Version 9.1 (2003).

RESULTS

From May 1, 2006 to April 20, 2007 at Hugh Taylor Birch State Park, Fort

Lauderdale, Florida, a total of 19,983 minutes of focal animal observations was collected on I. iguana (Site 1 = 5,219; Site 2 = 14,764; Season 1 = 5,609; Season 2 = 6,806; Season

3 = 2,587; Season 4 = 4,981). Summary statistics are displayed in Table 2 through Table

4 and Figures 8 and 9. An entry of 0.00 in the Mean columns of Tables 2 through 5 does not indicated that the activity was not observed at all, but merely that the mean proportion rounds to 0.00. In other words, the mean proportion is less than 0.005 in these cases. No size 4 iguanas were observed at Site 1 (Seawall)and no size 1 iguanas were observed at

Site 2 (Lagoon).

Results of the MANOVA, show that neither the site by size interaction (p =

0.5019) nor the size main effect (p = 0.16840) are significant; however, the site main effect is significant (p = 0.0484) (Table 2). This indicates there is a significant difference in the vectors of mean proportions for each activity among the sites. The univariate

ANOVAs indicate that these differences occur for activities 1 (Basking) and 4 (Resting).

Specifically, the mean proportion of time performing activity 1 (Basking) was significantly lower at Site 2 than at Site 1 (p = 0.0063) (Table 3). Conversely, the mean proportion of time performing activity 4 (Resting) was significantly lower at Site 1 than at Site 2 (p = 0.0069) (Table 3, Fig. 8, 10, 11). The univariate ANOVA for activity 1

(Basking) also indicates there is a significant difference in the mean proportions among the sizes (p = 0.0011). Tukey’s multiple comparisons showed the mean proportion of time performing activity 1 (Basking) is significantly lower (x-bar = .54) for size three iguanas than for size four iguanas (x-bar = .84) (Table 4). There are no other significant differences among the sizes. Results of the Two and Three-factor ANOVAs showed no significant effects of site and size, site and season, and size on activities (Table 5). Two- sample T-tests indicate significant differences in mean temperatures between sites for both season 2 (p = <0.0001) and season 3 (p = 0.0171) (Table 6). No other significant differences were seen in mean temperatures between sites.

Sky condition, wind, and precipitation factors were not included in analysis due to the variability that occurred within each observation period for each subject. The earliest movement observed at Site 1 (Seawall) occurred at 07:53 on July 10, 2006 and the latest at 20:09 on July 18, 2006. The earliest activity observed at Site 2 (Lagoon) occurred at

07:15 on April 14, 2007 and the latest at 20:35 on February 27, 2007.

Table 2. MANOVA results for differences in the vectors of mean proportions for activities 1 through 5 with respect to site and size. (p ≤ .05).

Variable Wilks' Lambda F df error df p-value Site 0.9509 2.27 5 220 0.0484 Size 0.9136 1.35 15 608 0.1684 Site*Size 0.9806 0.87 5 220 0.5019

Table 3. Summary statistics for activities at Site 1 (Seawall) and Site 2 (Lagoon).

Site Activity n Mean Std. Dev. Range

1 1 77 0.68 0.32 0-1 2 77 0.15 0.19 0-1 3 77 0.13 0.25 0-0.99 4 77 0.04 0.12 0-0.57 5 77 0.00 0.02 0-0.13 2 1 153 0.56 0.40 0-1 2 153 0.10 0.17 0-1 3 153 0.16 0.31 0-1 4 153 0.17 0.30 0-1 5 153 0.00 0.01 0-0.11

Table 4. Summary statistics for size categories (1 = ≤15cm; 2 = >15 – 30 cm; 3 = > 30 – 60cm; and 4 = > 60 cm).

Size Activity n Mean Std. Dev. Range

1 1 14 0.61 0.36 0-0.98 2 14 0.19 0.27 0-1 3 14 0.18 0.32 0-0.86 4 14 0.02 0.08 0-0.30 5 14 0.00 0.01 0-0.03 2 1 57 0.65 0.35 0-1 2 57 0.14 0.19 0-1 3 57 0.13 0.24 0-0.95 4 57 0.08 0.21 0-0.99 5 57 0.01 0.02 0-0.13 3 1 136 0.54 0.40 0-1 2 136 0.11 0.18 0-1 3 136 0.18 0.32 0-1 4 136 0.17 0.30 0-1 5 136 0.00 0.01 0-0.07 4 1 23 0.84 0.18 0.41-1 2 23 0.06 0.08 0-0.34 3 23 0.02 0.04 0-0.13 4 23 0.07 0.15 0-0.53 5 23 0.01 0.01 0-0.03

Table 5. Summary statistics for each combination of site (Site 1=Seawall, Site 2=Lagoon) and size.

Site Size Activity n Mean Std. Dev. Range

1 1 1 14 0.61 0.36 0-0.99 2 14 0.19 0.27 0-1 3 14 0.18 0.32 0-0.86 4 14 0.02 0.08 0-0.30 5 14 0.00 0.01 0-0.03 1 2 1 32 0.73 0.29 0.07-1 2 32 0.12 0.17 0-0.86 3 32 0.10 0.21 0-0.76 4 32 0.05 0.13 0-0.57 5 32 0.00 0.02 0-0.13 1 3 1 31 0.67 0.33 0-1 2 31 0.16 0.17 0-0.67 3 31 0.13 0.25 0-0.99 4 31 0.04 0.13 0-0.55 5 31 0.00 0.01 0-0.07 2 2 1 25 0.55 0.40 0-1 2 25 0.16 0.22 0-1 3 25 0.16 0.29 0-0.95 4 25 0.12 0.29 0-0.99 5 25 0.01 0.02 0-0.11 2 3 1 105 0.50 0.41 0-1 2 105 0.10 0.18 0-1 3 105 0.19 0.34 0-1 4 105 0.21 0.32 0-1 5 105 0.00 0.01 0-0.04 2 4 1 23 0.84 0.18 0.41-1 2 23 0.06 0.08 0-0.34 3 23 0.02 0.04 0-0.13 4 23 0.07 0.15 0-0.53 5 23 0.01 0.01 0-0.03

Table 6. Mean temperatures in °C between sites (Site 1=Seawall, Site 2=Lagoon) across seasons (Season 1= December 21 to March 20; Season 2= March 21 to June 20; Season 3= June 21 to September 20; Season 4= September 21 to December 20).

Site 1 Site 2 Season n mean(s.d.) n mean(s.d.) p-value 1 9 25.6 (1.4) 41 25.3 (2.6) 0.5849 2 34 28.6 (1.7) 47 25.0 (3.4) <0.0001 3 17 31.2 (1.1) 20 30.1 (1.5) 0.0171 4 17 27.3 (3.2) 45 27.3 (1.9) 0.9951

Figure 8. Mean percentage of time each activity (1=basking, 2=locomotion, 3=foraging, 4=resting, 5=visual signaling) was performed at each site (Site 1=Seawall, Site 2=Lagoon). (Site 1, n=77; Site 2, n= 153).

Figure 9. Mean percentage of time each activity was performed by each size category (1 = ≤15cm; 2 = >15 – 30 cm; 3 = > 30 – 60cm; and 4 = > 60 cm).

Figure 10. Percentage of time each activity was performed at Site 1 (Seawall) (n=77). (Activities = 1=basking, 2=locomotion, 3=foraging, 4=resting, 5=visual signaling.)

Figure 11. Percentage of time each activity was performed at Site 2 (Lagoon) (n=153). (Activities = 1=basking, 2=locomotion, 3=foraging, 4=resting, 5=visual signaling.)

Figure 12. Percentage of time each activity was performed by Size 2 at Site 1 (Seawall). (Activities = 1=basking, 2=locomotion, 3=foraging, 4=resting, 5=visual signaling.)

Figure 13. Percentage of time each activity was performed by Size 2 at Site 2 (Lagoon). (Activities = 1=basking, 2=locomotion, 3=foraging, 4=resting, 5=visual signaling.)

Figure 14. Percentage of time each activity was performed by Size 3 at Site 1 (Seawall). (Activities = 1=basking, 2=locomotion, 3=foraging, 4=resting, 5=visual signaling.)

Figure 15. Percentage of time each activity was performed by Size 3 at Site 2 (Lagoon). (Activities = 1=basking, 2=locomotion, 3=foraging, 4=resting, 5=visual signaling.)

DISCUSSION

The main focus of this study was to gain insight into the activity patterns of

Iguana iguana at Hugh Taylor Birch State Park (HTBSP), Fort Lauderdale, Florida

relative to site, size, and season. The most significant results showed differences in time

spent by I. iguana on activities of basking between the two study sites and between two

size categories. At Site 1 (Seawall), I. iguana spent 68% of their time basking and only

56% of their time basking at Site 2 (Lagoon). Percentages of observed basking,

locomoting, and foraging activities were comparable to percentages of behaviors

(basking=65%, locomotion=10%, foraging=18%, and displaying=7%) observed by

Figueiredo-de-Andrade et al. (2011). Figueiredo-de-Andrade et al. (2011) categorized

basking as an inactive behavior as did Dugan (1980). Furthermore, Dugan (1980)

excluded basking and locomotion activities such as sun-to-shade movement, tree-to-tree movement, escape from disturbance, and female travel to nesting sites in the examination of activity patterns. This could account for the differences in activity distribution reported when comparing the results of this study, Figueiredo-de-Andrade (2011) and Dugan

(1980). While twice as many subjects were observed at Site 2, it is quite possible that many of these subjects were the same individuals seen earlier in the observation period.

Site 2, was located in hammock habitat and many of the animals observed were amongst the tree branches along the water’s edge. Because most of the subjects studied were not marked for identification purposes, the observation period ended for each subject once

the animal was completely out of sight. While results showed I. iguana at Site 2 spent

more time resting, this was most likely attributed to the Site 2 animals being more visible

than the Site 1 animals during resting periods. At Site 1, all subjects observed, would

retreat into burrows throughout and at the end of the day, presumable to rest.

Unfortunately, because any I. iguana at Site 1 was deemed out of sight after entering a burrow, resting behavior was not as evident as at Site 2. Site 1 provided less sun-shade mosaic areas for basking than Site 2. At Site 1, as supported by McGinnis and Brown

(1966), I. iguana were observed in direct sun on the concrete seawall or open ground

when locomoting or foraging which occurred less frequently than basking. Most burrow

locations along the seawall were located nearby what little vegetation, in the form of

isolated sabal palm trees and seagrape, was present. Most animals were observed basking in the sun-dappled area within or adjacent to the vegetation (Fig. 16). At this site, burrows were the only source of complete shade for I. iguana. Heatwole (1970) found that deeper burrows were higher in temperature on average than shallow ones during early morning hours and conversely were cooler in temperature on average during the hottest part of the day. Iguana iguana at Site 1 exhibited more predictable

thermoregulatory behavior (McGinnis and Brown 1966) whereby animals would bask in

direct sun at the edge of the sun-shade mosaic or within the sun-shade mosaic and then

move into complete shade or into a burrow. This activity was most observed throughout

the day at Site 1. While further research is needed to determine to what capacity burrows

are used at this and other sites in Florida, observations from this study at HTBSP indicate

that burrows are primarily used for thermoregulation, sleeping, and predator avoidance.

HTBSP is a pet-friendly park and on many occasions I. iguana at Site 1 were observed

retreating quickly into burrows at first sight of a domestic dog. Additionally, on multiple

occasions, I. iguana were observed utilizing both the canal along the seawall and the

lagoon to escape potential predators (Krysko et al. 2010, Meshaka 2011).

Across sites, Size 3 (> 30 – 60cm) I. iguana spent less time basking than Size 4 (>

60 cm) I. iguana. Interestingly, the Size 4 I. iguana were only documented at Site 2

(Lagoon). For purposes of this study, Size 4 describes the largest dominant males within the observed groups of animals (Fig. 17.). Size 3 described both adult males and females, some not distinguishable in terms of sex. While Size 4 animals were not documented at

Site 1 (Seawall), several smaller adult males were observed at Site 1 and therefore documented as Size 3 (Figure 18). However, throughout this study, the largest dominant males remained around the lagoon at Site 2. Dominant male I. iguana will often displace sub adults from their home territory (Dugan 1982, Figueiredo-de-Andrade et al. 2011), which may account for the smaller males seen at Site 1. Overall, many more observations occurred at Site 2 than Site 1. There are several possible explanations for this behavior. First, Site 2 provided more basking sites with many more visual barriers which allowed for more dominant males to co-habitat in this area (Fig. 11). Secondly,

Site 1 did not provide as much protection from predators and I. iguana relied on a few burrows along the wall and the canal to escape potential predators (Fig. 10). Thirdly, Site

2 offered something that Site 1 did not: a steady source of freshwater in the form of the lagoon. And finally, the interior of the park around Site 2 offered much more food choices than Site 1. When comparing two study sites, Figueiredo-de-Andrade et al.

(2011) found I. iguana choosing sites with more reliable food sources. The behaviors

observed at HTBSP during the course of this study could indicate that when given the

choice, I. iguana prefer habitat with more food choices, access to freshwater, and protection from predators.

In a study by van Marken Lichtenbelt and colleagues (1993), males spent more

time on locomotion activities (included foraging) than female I. iguana. Although not

significant, results of this study showed Size 3 category of the I. iguana spent more time

than Size 4 animals on other activities such as foraging and locomoting (Figure 2).

Additionally, Size 1 and Size 3 I. iguana spent more time foraging than Size 2 and Size 4

animals. Size 1 category included hatchling I. iguana and Size 3 category included

reproductive females. While mean high temperatures across seasons differed, specifically

in the Spring and Summer, seasonality in this study did not affect activity patterns of I.

iguana at HTBSP from May 1, 2006 to April 20, 2007. Seasonality, which includes

temporal variation, may minimally affect locomotion activities of I. iguana at HTBSP

when taking into account study sites. While the ANOVA analysis did not show any

significant effects of seasonality on activity patterns, interaction of site and season on the

activity of locomotion (p=0.0590) was almost significant at p=0.05.

Additional noteworthy observations on the activities of I. iguana were made

during the course of this study. At least one mating event was observed on January 13,

2006 at Site 1 (Seawall) and involved a sub-dominant male similar in appearance to an

adult female. In 2007, hatchlings of I. iguana were observed by park personnel as early as

April 11 (G. Busch pers. comm. 2007). This is noteworthy as Krysko et al. (2007) reports

that in Florida hatching of I. iguana occurs from May to August and Meshaka et al.

(2007) reports peak nesting season in April. However, Dugan (1980) and Rand and

Greene 1982) reported that in most of it native tropical range, hatching is synchronous

with the rainy season and can begin as early as April. In Florida, many colonies of I.

iguana are established within or adjacent to urbanized landscapes, which contain pockets

of man-made freshwater sources (Meshaka et al. 2004b) and resultant forage material

throughout the year. Rand and Greene (1982) suggest that in some environments, whereby dry seasons are non-existent, I. iguana may possibly exhibit a second mating season. On July 10, 2006, six newly hatched I. iguana were observed communally foraging at the Site 1 (Seawall). For approximately two hours they foraged in the open grass, staying within 1m of each other and were accompanied by one larger juvenile iguana that did not appear to be foraging. On several occasions, during this study,

communal foraging events were observed where one individual seemed to have taken on

the role of a sentinel.

Within the park, I. iguana were observed using a variety of plants for basking and

sleeping including Australian pine (Casuarina equisetifolia), seagrape (Cocoloba uvifera),

cocoplum (Chrysobalanus icaco), strangler fig (Ficus aurea), and cabbage palm (Sabal palmetto) (Table 7). HTBSP iguanas consume a variety of plant material including wedelia (Wedelia trilobata), hibiscus (Hibiscus spp.), strangler fig (Ficus aurea), seagrape

(Cocoloba uvifera), and Surinam cherry (Eugenia uniflora) (J. Gibson and R. Mapp, pers. comm. 2005, Sekscienski pers. obs. 2007). Examination of fecal material for two iguanas revealed the presence of Surinam cherry seeds. Although the seeds were not successfully

germinated, seed dispersal of this and other non-native plants may be likely by I. iguana

in Florida (Iverson 1985, Smith et al. 2007, Engeman et al. 2011).

Table 7. Plants consumed by I. iguana at Hugh Taylor Birch State Park from May 2006 to April 2007. N = native, I = invasive, A = annual, P = Perennial, LV = leaves, FL = flower, FR = fruit.

Family Scientific Name Common Name N or I A or P LV FL FR Annonaceae Annona glabra pond apple N P x Asteraceae Wedelia trilobata Biscayne Bay x x I A/P creeping oxeye Chrysobalanaceae Chrysobalanus icaco cocoplum N P x x Convolvulaceae Ipomoea spp. morning glory I/N A/P x Goodeniaceae Scaevola taccada var. beach naupaka x I P sericea Malvaceae Sida acuta common wireweed N P x x Malvaceae Hibiscus spp. hibiscus I x x Moraceae Ficus aurea strangler fig N P x x Myrtaceae Eugenia uniflora Surinam cherry I P x x Polygonaceae Coccoloba uvifera seagrape N P x x Rubiaceace Spermacoce prostrata prostrate false x x N A buttonweed Verbenaceae Lippia spp. fog fruit N P x x Vitaceae Vitis spp. wild grape N P x

Conclusion

Many of the successful green iguana populations in Florida occur in environments where the natural flora and fauna communities have been disturbed (Meshaka et al.

2004b, Smith et al. 2006, Smith et al. 2007, Sementelli et al. 2008, Meshaka et al. 2009,

Meshaka 2011). As the case at HTBSP, these areas facilitate the explosive growth of ornamental and exotic plants, are largely void of competitors and predators, and therefore, support large numbers of iguanas (Meshaka et al. 2004b, Smith et al. 2007).

There may be other environmental characteristics and stimuli as well as social habits to consider when developing eradication or control strategies of green iguana. For example,

41 previous studies have revealed that in their native habitat, I. iguana females show nest site fidelity (Bock et al. 1985). Additionally, I. iguana frequently nest in sandy soil (Carr

1956, Townsend et al. 2003, Engeman et al. 2005b), so it may be pertinent to locate and monitor those areas to destroy nests as they are laid and to trap returning females. While several gravid female I. iguana were observed during the month of April 2007, no nesting behavior was observed nor a nesting site confirmed at HTBSP. While some effects of I. iguana’s effects on South Florida ecosystems have been revealed (Simberhoff 1997

Mckie et al. 2005, Truglio et al. 2008), more quantitative studies should be attempted to explain the reason for their success in such an array of habitats.

Gathering behavioral data can offer researchers the chance to see which mechanisms are the most responsible for the success of a particular invasive species.

Additionally, the overall health of a habitat being invaded can be an indicator of the threat that an invasive species poses to that habitat (Van Driesche and Van Driesche

2000). One idea contends invading species will be most successful in niches not occupied by natives (Van Driesche and Van Driesche 2000). Furthermore, invasive lizards can compete for food and space and it is in habitats where sensitive species are already at risk of extinction through other pressures such as hurricanes, frost events, human disturbance, and drought, that I. Iguana can be the most detrimental (Meshaka et al., 2004a, J. Daniels, pers. comm. 2012). The Miami blue butterfly (Hemiargus thomasi bethunebakeri) is listed as federally endangered and became extirpated from Bahia Honda State Park,

Bahia Honda Key, Florida in 2010. (J. Daniels, pers. comm. 2012). After their initial introduction to the island in 2005, the population of I. iguana continued to grow and

began to severely denude remaining patches of the Miami blue butterfly’s host plant

nickerbean (Caesalpinia bonduc). While the new growth on the nickerbean was preferred

for egg-laying Miami blue butterflies, continued defoliation of these portions of the host

plant by I. iguana resulted in loss of eggs and larvae i.e. biological sink (J. Daniels, pers.

comm. 2012). Engeman et al. 2011 suggests focusing removal efforts of I. iguana in areas

with higher risks to native species, specifically islands. Unfortunately, complete

eradication of I. iguana on the island of Bahia Honda has not been successful and may

have contributed to the extirpation of the Miami blue butterfly (J. Daniels, pers. comm.

2012).

With the prevalence of introduced species, scientists are constantly required to

hone eradication protocols and management strategies for these species; therefore,

gathering baseline data and continued monitoring is extremely warranted. The results of

this study offer more baseline data into the behavior of I. iguana in Florida and give

further evidence into the behavioral flexibility of this species.

Figure 16. Iguana iguana utilizing sun-shade mosaic. Hugh Taylor Birch State Park, Fort Lauderdale, Florida. 43

Figure 17. Three smaller adult male I. iguana at Study Site 1 (Seawall), Hugh Taylor Birch State Park, Fort Lauderdale, Florida.

Figure 18. Two dominant male I. iguana at Study Site 2 (Lagoon), Hugh Taylor Birch State Park, Fort Lauderdale, Florida.

REFERENCES

Adolph, S. C. 1990. Influence of behavioral thermoregulation on microhabitat use by two

Sceloporus lizards. Ecology 71: 315-327.

Alvarado, J., L. Ibarra, I. Suazo, G. Rodriguez, and R. Zamora. 1995. Reproductive

characteristics of a green iguana (Iguana iguana) population of the west coast of

Mexico. The Southwestern Naturalist 40(2): 234-237.

Anderson, C. and K. M. Enge. 2012. Ctenosaura similis (Gray’s Spiny-tailed Iguana) and

Iguana iguana (Green Iguana). Carrion Feeding. Herpetological Review 43(1):

131.

Arendt, W. J. 1986. An observation of Iguana iguana feeding on eggs of the cattle egret

(Bulbicus ibis) at Fox’s Bay, Montserrat, West Indies: a case of predation or

scavenging? Caribbean Journal of Science 22(3-4): 221-222.

Bock, B. C. and A. S. Rand. 1989. Factors influencing nesting synchrony and hatching

success at a green iguana nesting aggregation in Panama. Copeia 1989(4): 978-

986.

Bock, B. C., Rand, A. S., & Burghardt, G. M. 1985. Seasonal migration and nesting site

fidelity in the green iguana. Contributions in Marine Science 37: 435-443.

Bogert, C. M. 1949. Thermoregulation in reptiles, a factor in evolution. Evolution 3(3):

195-211.

Burghardt, G. M. 1977. Of iguanas and dinosaurs: Social behavior and communication in

neonate reptiles. American Zoologist, 17(1): 177-190.

Burghardt, G. M., H. W. Greene and A. S. Rand. 1977. Social behavior in hatchling

green Iguanas: Life at a reptile rookery. Science. 195(4279): 689-691.

Burghardt, G. M. and S. A. Rand. 1985. Group size and growth rate in hatchling green

iguanas (Iguana iguana). Behavioral Ecology and Sociobiology 18: 101-104.

Busch, G. 2007. Hugh Taylor Birch State Park, Fort Lauderdale, Fl. Pers. Comm.

Butterfield, B. P., Meshaka, Jr., W. E, and C. Guyer. 1997. Nonindigenous

amphibians and reptiles. In Strangers in Paradise. (Simberloff, D., Schmitz, and

T. C. Brown, eds.) pp. 123-138. Island Press.

Campbell, A. 2011. Effects of a severe winter event on invasive green iguanas (Iguana

iguana). Unpubl. Master’s thesis, Florida Atlantic University, Boca Raton,

Florida.

Carr, A. 1956. The Windward Road; Adventures of a Naturalist on Remote Caribbean

Shores. A. A. Knopf.

Carter, J. P. 2012. 1107 NW 133 Avenue, Pembroke Pines, Fl. Pers. Comm.

Christian, K., C. R. Tracy, and W. P. Porter. 1983. Seasonal shifts in body temperature

and use of microhabitats by Galapagos land iguanas (Conolophus pallidus).

Ecology 64:463-468.

Dalrymple, G. H. 1994. Non-indigenous amphibians and reptiles. Pages 67-78, in D. C.

Schmitz and T. C. Brown, project directors. An assessment of invasive non-

indigenous species in Florida's public lands. Florida Department of

Environmental Protection Technical Report No. TSS-94-100, Tallahassee,

Florida, USA.

Daniels, J. 2012. Florida Museum of Natural History, University of Florida, Gainesville,

Fl. Pers. Comm.

Diaz, J. A. 1997. Ecological correlates of the thermal quality of an ectotherm's habitat: a

comparison between two temperate lizard populations. Functional Ecology 11(1):

79-89.

Division of Recreation and Parks. 2006. Hugh Taylor Birch State Park Florida State Park:

Unit Management Plan. Florida Department of Environmental Protection,

Tallahassee, Florida, USA.

Dugan, B. A. 1980. A field study of the social structure, mating system, and display

behavior of the green iguana. Unpubl. Ph. D. dissertation,University of

Tennessee, Knoxville, Tennessee.

Dugan, B. A. 1982. The mating behavior of the green iguana, Iguana iguana. In Iguana of

the World: Their Behavior, Ecology, and Conservation. (Burghardt, G. M. and A.

S. Rand, eds.) pp. 320-341. Noyes.

Dugan, B. A. and T. V. Wiewandt. 1982. Socio-Ecological determinants of mating

strategies in iguanine lizards. In Iguanas of the World: Their Behavior, Ecology,

and Conservation. (Burghardt, G. M. and A. S. Rand, eds.) pp. 303-319. Noyes.

Durtsche, R. D. 2000. Ontogenetic plasticity of food habits in the Mexican spiny-tailed

iguana, Ctenosaura Pectinata. Oecologia 124(2): 185-195.

Engeman, R. M., E. Jacobson, M.L. Avery, and W. E. Meshaka Jr. 2012. The aggressive

invasion of exotic reptiles in Florida with a focus on prominent species: A review.

Current Zoology 57(5): 599-612.

Engeman, R. M., E. M. Sweet, and H. T. Smith. 2005a. Iguana iguana (Green Iguana)

Predation. Herpetological Review 36 (3): 320.

Engeman, R. M., H. T. Smith, and D. Constantin. 2005b. Invasive green iguanas as

airstrike hazards at San Juan International Airport, Puerto Rico. Journal of

Aviation-Aerospace Education and Research. 14 (3): 45-50.

Etheridge, R. E. 1982. Checklist of the iguanine and Malagasy iguanid lizards. In Iguanas

of the World: Their Behavior, Ecology, and Conservation. (Burghardt, G. M. and

A. S. Rand, eds.) pp. 7-37. Noyes.

Etheridge, R. E., and K. de Queiroz. 1988. A phylogeny of Iguanidae. In Phylogenetic

relationships of the lizard families: Essays Commemorating Charles L. Camp.

(Estes, R. and G. Pregill, eds.) pp. 283-367. Stanford.

Figueiredo-de-Andrade, C. A., R. A. Montoya-Ospina, J. C. Voltolini, and C. R. Ruiz-

Miranda. Population biology and behaviour of the alien species Iguana iguana

(Linnaeus, 1758) on a restored wetland in Puerto Rico. Herpetology Notes 4:

445- 451.

Foley, M. 2012. Hugh Taylor Birch State Park, Fort Lauderdale, Fl. Pers. Comm.

Frost, D. R., R. E. Etheridge, J. Daniel, and T. A. Titus. 2001.Total evidence, sequence

alignment, evolution of polychrotid lizards, and a reclassification of the Iguania

(Squamata: Iguania). American Museum Novitates. 3343: 1–38.

Gibson, J. 2005. Hugh Taylor Birch State Park, Fort Lauderdale, Fl. Pers. Comm.

Gier, P. J. 2003. The interplay among environment, social behavior, and morphology:

iguanid mating systems. In Lizard Social Behavior. (Fox, S. F., J. K. McCoy, and

T. A. Baird, eds.) pp. 278-309. Johns Hopkins.

Global Invasive Species Database (2012) Iguana iguana. Retrieved October 1, 2012

from http://www.issg.org/database/species/ecology.asp?si=1022&fr=1&sts=

Golden, E. 2007. Bill Baggs Cape Florida State Park, Key Biscayne, Fl. Pers. Comm.

Goodman, R. M., F. J. Burton, and A. C. Echternacht. 2005. Habitat use of the

endangered iguana Cyclura lewisi in a human-modified landscape on Grand

Cayman. Animal Conservation 8: 397-405.

Gordon, D. R. and K. P. Thomas. 1997. Florida’s invasion by nonindigenous

plants: history, screening, and regulation. In Strangers in Paradise. (Simberloff,

D., Schmitz, and T. C. Brown, eds.) pp. 21-37. Island Press.

Greene, H. W., G. M. Burghardt, B. A. Dugan, and A. S. Rand. 1978. Predation and the

defensive behavior of green iguanas (Reptilia, Lacertilia, Iguanidae). Journal of

Herpetology 12 (2): 169-176.

Grant, B. W., and A. E. Dunham 1988. Thermally imposed time constraints on the

activity of the desert lizard Sceloporus merriami. Ecology 69 (1): 167-176

Heatwole, H. 1970. Thermal ecology of the desert dragon Amphibolurus inermis.

Ecological Monographs 40: 425-457.

Hirth, H. F. 1963. Some aspects of the natural history of Iguana iguana on a tropical

strand. Ecology 44: 613-615.

Iverson, J. B. 1982. Adaptations to herbivory in iguanine lizards. In Iguanas of

the World: Their Behavior, Ecology, and Conservation. (Burghardt, G. M. and A.

S. Rand, eds.) pp. 60-76. Noyes.

King, W. and T. Krakauer. 1966. The exotic herpetofauna of southeastern Florida.

Quarterly Journal of the Florida Academy of Sciences 29: 144-154.

Krysko, K. L., K. M. Enge, E. M. Donlan, J. C. Seitz, and E. A. Golden. 2007.

Distribution, natural history, and impacts of the introduced green iguana (Iguana

iguana) in Florida. Iguana 14:2-11.

Krysko, K. L., Enge, K. M., Donlan, E. M., Golden, E. A., Burgess, J. P., and K. W.

Larsen. 2010. The non-marine herpetofauna of Key Biscayne, Florida.

Herpetological Conservation and Biology 5(1): 132-142.

Lazell, J. D., Jr. 1973. The lizard genus Iguana in the Lesser Antilles. Bulletin of the

Museum of Comparative Zoology 145(1):1-28.

Loftin, H. and E. L. Tyson. 1965. Iguanas as carrion eaters. Copeia: 515-515.

Magnuson, J. T., L. B. Crowder, and P. A. Medvick. 1979. Temperature as an ecological

resource. American Zoologist 19:331-343.

Mapp, R. 2005. Hugh Taylor Birch State Park, Fort Lauderdale, Fl. Pers. Comm.

Martin, P. and P. Bateson (1993). Measuring Behaviour: An Introductory Guide.

Cambridge University Press.

Martins, E. P. (2004). Introduction of behavior and ecology. In Iguanas: Biology and

Conservation. (Alberts, A. C., Carter, R.L., Hayes, W. K., and E. P. Martins, eds.)

pp. 97-100. University of California Press.

McBee, R. H. and V. H. McBee. 1982. The bindgut fermentation in the Green iguana,

Iguana iguana. In Iguanas of the World: Their Behavior, Ecology, and

Conservation. (Burghardt, G. M. and A. S. Rand, eds.) pp. 77-83. Noyes.

McGinnis, S. and C. Brown. 1966. Thermal behavior of the green iguana, Iguana iguana.

Herpetologica: 189-199.

Mckie, A. C., J. E. Hammond, H. T. Smith, and W. E. Meshaka, Jr. 2005. Invasive green

iguana interactions in a burrowing owl colony in Florida. Florida Field Naturalist

33(4): 125-127.

Meek, R. 1995. Reptiles, Thermoregulation and the Environment. Testudo (4)2: 56-78.

Meshaka, W.E., Jr. 2011. A Runaway Train in the Making: The Exotic Amphibians,

Reptiles, Turtles, and Crocodilians of Florida. Monograph 1. Herpetological

Conservation and Biology 6:1-101.

Meshaka, W. E., Jr., B. P. Butterfield, and J. B. Houge. 2004a. The Exotic Amphibians

and Reptiles of Florida. Krieger Publishing Company.

Meshaka, W. E., Jr., R. D. Bartlett, and H.T. Smith. 2004b. Colonization success by

green iguanas in Florida. Iguana 11(3): 155-161.

Meshaka, W. E., H. T. Smith, H. L. Cress, S. R. Sekscienski, W. R. Mapp, E. M. Cowan,

and J. A. Moore. 2009. Raccoon (Proycon lotor) removal and the rapid

colonization of the green iguana (Iguana iguana) on a public land in South

Florida: A conservation opportunity for the Caribbean. Caribbean Journal of

Science 45(1): 15-19.

Mora, J. M. 1991. Comparative grouping behavior of juvenile ctenosaurs and iguanas.

Journal of Herpetology 25(2): 244-246.

NOAA (2012). National Climatic Data Center. Retrieved October 12, 2012 from

http://www.ncdc.noaa.gov/cdo-web/#t=secondTabLink.

Phillips, J. A., A. C. Alberts, and N. C. Pratt. 1993. Differential resource use, growth, and

the ontogeny of social relationships in the green iguana. Physiology & Behavior

53: 81-88.

Powell, R. 2006. Conservation of the herpetofauna on the Dutch Windward

Islands: St. Eustatius, Saba, and St. Maarten. Applied Herpetology 3: 293-306

Pratt, N. C., A. C. Alberts, K. G. Fulton-Medler, and J. A. Phillips. 1992. Behavioral,

physiological, and morphological components of dominance and mate attraction

in male green iguanas. Zoo Biology 11:153-163.

Rand, A. S. 1968. A nesting aggregation of iguanas. Copeia 552-561.

Rand, A. S. 1990. The diet of a generalized folivore: Iguana iguana in Panama. Journal

of Herpetology 24: 211-214.

Rand, A. S., and B. Dugan. 1983. Structure of complex iguana nests. Copeia, 705-711.

Rand, A. S. and H. W. Greene. 1982. Latitude and climate in the phenology of

reproduction in the green iguana, Iguana iguana. In Iguanas of the World: Their

Behavior, Ecology, and Conservation. (Burghardt, G. M. and A. S. Rand, eds.)

pp. 303-319. Noyes.

Rand, A. S., E. Font, D. Ramos, D. I. Werner and B. C. Bock. 1989. Home range in green

iguanas (Iguana iguana) in Panama. Copeia 1: 217-221.

Rodda, G. H. 1992. The mating behavior of Iguana iguana. Smithsonian Contributions to

Zoology 534: l-40.

Ruggeiri, M. 2012. Flamingo Gardens and Everglades Sanctuary, Fl. Pers. Comm.

SAS® 2003. Software Version 9.1. SAS Institute Inc.

Sementelli, A. J., H. T. Smith, W. E. Meshaka Jr. and D. Alexander. 2008a. Iguana

iguana (green iguana): Colony burrow density in Florida. Journal of Kansas

Herpetology 25: 11.

Sementelli, A. J., H. T. Smith, W. E. Meshaka and R. M. Engeman. 2008b. Just green

iguanas? The associated costs and policy implications of exotic invasive wildlife

in South Florida. Public Works Management & Policy 12(4): 599-606.

Simberloff, D. 1997. The biology of invasions. In Strangers in Paradise. (Simberloff, D.,

Schmitz, and T. C. Brown, eds.) pp. 3-17. Island Press.

Smith, H. T. and R. M. Engeman. 2002. An extraordinary raccoon, Procyon lotor,

density at an urban park. Canadian Field-Naturalist 116: 636-639.

Smith, H. T., W. E. Meshaka, R. M. Engeman, S. M. Crossett, M. E. Foley, and G.

Busch. 2006. Raccoon predation as a limiting factor in the success of the green

iguana in southern Florida. Journal of Kansas Herpetology 20: 7-8.

Smith, H. T., E. Golden, and W. E. Meshaka. 2007. Population density estimates for

a green iguana (Iguana iguana) colony in a Florida State Park. Journal of Kansas

Herpetology 21: 19-20.

Swanson, P. L. 1950. The Iguana Iguana iguana iguana (L). Herpetologica 6:187-193.

Townsend, J. H., K. L. Krysko, and K. M. Enge. 2003. Introduced iguanas in southern

Florida: a history of more than 35 years. Iguana 10(4): 111-118.

Townsend, J. H., J. Slapcinsky, K. L. Krysko, E. M. Donlan, and E. A. Golden. 2005.

Predation of a tree snail Drymaeus multilineatus (Gastropoda: Bulimulidae) by

Iguana iguana (Reptilia: Iguanidae) on Key Biscayne, Florida. Southeastern

Naturalist 4(2): 361-364.

Troyer, K. 1983. Posthatching yolk energy in a lizard; utilization pattern and interclutch

variation. Oecologia 58(3): 340-344.

Troyer, K. 1984a. Microbes, herbivory and the evolution of social behavior. Journal of

Theoretical Biology 106(2): 157-169.

Troyer, K. 1984b. Diet selection and digestion in Iguana iguana; the importance of age

and nutrient requirements. Oecologia 61(2): 201-207.

Troyer, K. 1984c. Behavioral acquisition of the hindgut fermentation system by hatchling

Iguana iguana. Behavioral Ecology and Sociobiology 14(3): 189-193.

Truglio, M. R., H. T. Smith, and W. E. Meshaka Jr. 2008. Use of gopher tortoise burrows

(Gopherus polyphemus) by the exotic green iguana (Iguana iguana) in Southern

Florida. Herpetology: 22.

USDA (2012) Invasive Species Program. Retrieved October 12, 2012 from

http://www.fs.fed.us/invasivespecies/index.shtml.

Van Devender, R. W. 1982. Growth and ecology of spiny-tailed and green iguanas in

Costa Rica, with comments on the evolution of herbivory and large body size. In

Iguanas Of the World: Their Behavior, Ecology, and Conservation. (Burghardt,

G. M. and A. S. Rand, eds.) pp. 162-183. Noyes.

Van Driesche J. and R. Van Driesche. 2000. Nature Out of Place: Biological Invasions in

the Global Age. Island Press. van Marken Lichtenbelt, W. D. 1993. Optimal foraging of a herbivorous lizard, the green

in a seasonal environment. Oecologia 95(2): 246-256. van Marken Lichtenbelt, W. D. and K. B. Albers. 1993. Reproductive adaptations of the

green iguana on a semi-arid island. Copeia 3: 790-798. van Marken Lichtenbelt, W. D., Wesselingh, R. A., Vogel, J. T., and K. B. Albers. 1993.

Energy budgets in free-living green iguanas in a seasonal environment. Ecology

74(4): 1157-1172. van Marken Lichtenbelt, W. D., Vogel, J. T., and R. A. Wesselingh. 1997. Energetic

consequences of field body temperatures in green iguana. Ecology 78(1): 297-

307.

Weins, J. J. and B. D. Hollingsworth. 2000. War of the Iguanas: Conflicting Molecular

and Morphological Phylogenies and Long-Branch Attraction in Iguanid Lizards

Systematic Biology 49(1): 143-159.

Whitaker, P. B. and R. Shine. 2002. Thermal biology and activity patterns of the eastern

brownsnake (Pseudonaja textilis): a radiotelemetric study. Herpetologica 58(4):

436-452.