Distribution of Cane Toads (Rhinella Marina) in Florida and Their Status in Natural Areas

DISTRIBUTION OF CANE TOADS (RHINELLA MARINA) IN FLORIDA AND THEIR STATUS IN NATURAL AREAS

AUDREY C. WILSON

A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2016

To my family

ACKNOWLEDGMENTS

I would like to thank my advisor, Steve A. Johnson, for his guidance throughout this project and for providing financial support. I am grateful to my committee members,

Christina Romagosa and Betsie Rothermel, for their constant support. Jamie Barichivich provided invaluable advice during the planning and analysis of my thesis. The USGS loaned me the equipment necessary for the fieldwork, without which this project would not have been possible. Camila Rodriguez frequently assisted me in the field. James

Colee from IFAS statistical consulting helped with analysis. I am also grateful to the faculty, students, and staff of the Department of Wildlife Ecology and Conservation for their patience and support.

TABLE OF CONTENTS

page

ACKNOWLEDGMENTS ...... 4

LIST OF TABLES ...... 7

LIST OF FIGURES ...... 8

LIST OF ABBREVIATIONS ...... 9

ABSTRACT ...... 10

CHAPTER

1 BACKGROUND ON CANE TOADS IN FLORIDA ...... 12

Invasive Species ...... 12 Florida’s Nonnative Herpetofauna ...... 13 Cane Toad Natural History ...... 13 Global Invasions ...... 15 Ecology in Florida ...... 17 Research Design and Thesis Structure ...... 18

2 PRESENCE OF CANE TOADS ALONG A DISTURBANCE GRADIENT IN FLORIDA ...... 19

Introduction ...... 19 Materials and Methods...... 24 Study Sites ...... 24 Autonomous Recording Units ...... 24 Disturbance Levels ...... 25 Song Scope ...... 26 Occupancy Modeling ...... 27 Results ...... 28 Occupancy Modeling ...... 29 Recognizer Performance ...... 29 Discussion ...... 30

3 CURRENT DISTRIBUTION OF CANE TOADS IN FLORIDA ...... 46

Introduction ...... 46 Methods ...... 48 Results ...... 49 Discussion ...... 50

4 FUTURE DIRECTIONS ...... 60

APPENDIX

A SUPPLEMENTAL GRAPH ...... 64

B RECORDS ...... 65

LIST OF REFERENCES ...... 69

BIOGRAPHICAL SKETCH ...... 76

LIST OF TABLES

Table page

2-1 Descriptions of each of the study areas...... 40

2-2 Dates ARUs were deployed at each of the study areas...... 41

2-3 Descriptions of each of the disturbance levels...... 41

2-4 Number of ARUs deployed at each disturbance level within each site...... 41

2-5 Summary of ARU results...... 42

2-6 Model rankings for 2015, all five disturbance categories ...... 43

2-7 Model rankings for 2016, all five disturbance categories ...... 44

2-8 Model rankings for 2015, binary ...... 44

2-9 Model rankings for 2016, binary ...... 44

2-10 Results for top ranked models for each season with binary habitat type ...... 45

3-1 Citizen science reports by county ...... 59

B-1 Summary of all cane toad records by county and decade...... 65

B-2 All citizen science reports of cane toads from Jul. 2014 through Sept. 2016 ...... 66

LIST OF FIGURES

Figure page

2-1 Map of study areas...... 38

2-2 Cane toad distribution...... 39

3-1 Accurate cane toad records from all sources, regardless of establishment status...... 55

3-2 Established cane toad records only...... 56

3-3 Cane toad records from southwest Florida reported prior to 2010...... 57

A-1 Weekly rainfall and deployment dates of ARUs at Archbold Biological Station during 2015...... 64

LIST OF ABBREVIATIONS

ABS Archbold Biological Station

AIC Akaike information criterion

ARU Autonomous recording unit

BCNP Big Cypress National Preserve

BNP Biscayne National Park

ENP Everglades National Park

FFT Fast Fourier transform

FLMN Florida Master Naturalists

FWC Florida Fish and Wildlife Conservation Commission

SE Standard error

SNR Signal-to-noise ratio

SPI Standardized precipitation index

UF University of Florida

Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science

DISTRIBUTION OF CANE TOADS (RHINELLA MARINA) IN FLORIDA AND THEIR STATUS IN NATURAL AREAS

Audrey C. Wilson

December 2016

Chair: Steve A. Johnson Major: Wildlife Ecology and Conservation

Nonnative cane toads (Rhinella marina) have been established in Florida since the 1950s. Although they are prevalent in human-modified habitat in much of south and central Florida, there are few reports of cane toads in natural areas. I sampled intensively at five levels of habitat disturbance to determine cane toad presence along a disturbance gradient. I deployed autonomous recording units (ARUs) in five natural areas and surrounding disturbed habitat in 2015 and 2016. Each ARU was deployed near a potential breeding site and programmed to record for five minutes each hour from sunset to sunrise. I then scanned all files with an automated recognizer using Song

Scope® software (Wildlife Acoustics). Although I regularly detected cane toads in urban areas, I detected very few at sites with the lowest disturbance levels. I conducted single- season, single-species occupancy models for the 2015 and 2016 seasons. For each season, I ran a model with all five disturbance levels and one with the disturbance levels collapsed into binary disturbed and undisturbed habitat. Occupancy for disturbed habitat was 0.2004 (SE=0.1035) and 7.05e-5 (SE=0.0024) in natural in 2015; occupancy was

0.2238 (SE=0.09862) and 0.000234 (SE=0.003952) in disturbed and natural categories, respectively, for 2016. I found no evidence that cane toads are established in natural

areas in Florida. I also compiled records from online databases, citizen scientists, and other sources to create an updated distribution map. Results indicate a range expansion in southwest FL. Establishment status could not be confirmed for all records, so those reports require further investigation.

CHAPTER 1 BACKGROUND ON CANE TOADS IN FLORIDA

Invasive Species

Invasive species are widely considered one of the most significant threats to global biodiversity (e.g., Simberloff 1997; Wilcove et al. 1998). Although only a small proportion of introduced species successfully establish and proliferate, those that do can negatively affect native species and significantly alter ecosystems (Lodge 1993;

Mack et al. 2000). They endanger native species via predation, direct and indirect competition, and can even disrupt fundamental ecological processes, such as fire, hydrology, and nutrient cycling (Mack et al. 2000; Ehrenfeld 2003). For example, the introduction of the brown tree snake (Boiga irregularis) to Guam has resulted in extinction of several native bird species (Savidge 1987). Buffelgrass (Pennisetum ciliare), introduced to arid regions around the world for erosion control and cattle grazing

(Burquez-Montijo et al. 2002), has increased fuel load and brought devastating wildfire to ecosystems not adapted for fire (McDonald and McPherson 2011).

In addition to the environmental effects of invasive species, invaders generate staggering economic losses. Costs of restoring invaded habitats are an important component of these losses, and invasive species are also known to directly impact the economy by, for example, causing power outages or reducing property values (Burgio et al. 2014; Sin and Radford 2007). A 2005 study found that in the United States alone,

50,000 invasive species generated $120 billion in environmental damage each year

(Pimentel et al. 2005).

Florida’s Nonnative Herpetofauna

Florida has been the subject of numerous species introductions and leads the nation in the number of nonindigenous reptile and amphibian species by a wide margin

(Butterfield et al. 1997; Krysko et al. 2011). Several invasion pathways are known, but the vast majority of introduced herpetofauna in Florida arrive through the pet trade

(Krysko et al. 2011). Though some have little obvious impact, others have significantly affected native species (e.g., Burmese pythons; McCleery et al. 2015). A fundamental step in identifying the impacts of nonindigenous species and developing management strategies is creating an understanding of which habitats are vulnerable to invasion by a given species. Although the majority of introduced amphibians and reptiles in Florida are exclusively associated with disturbed sites, some species have colonized natural areas (Butterfield et al. 1997; Krysko et al. 2011). Cuban treefrogs (Osteopilus septentrionalis; e.g., Meshaka 2011), Burmese pythons (Python bivittatus; e.g.,

Meshaka et al. 2000), and greenhouse frogs (Eleutherodactylus planirostris: Meshaka et al. 2004) are all established in natural areas in south Florida. Cane toads (Rhinella marina), established in Florida since the 1950s, are one of four species of nonnative anurans established in Florida (King and Krakauer 1966; Krysko et al. 2016).

Cane Toad Natural History

Cane toads, true toads (Bufonidae) native to extreme southern Texas through

Central and tropical South America, have been introduced in many other parts of the world. Cane toads naturally occur in a wide array of habitat types, primarily populating areas up to 1,000 m above sea level. This limit varies with latitude, as warmer temperatures near the equator enable cane toads to survive at higher elevations (Lever

2001). In Costa Rica, these habitat generalists live everywhere from savannah to open

forest. Dense vegetation, however, acts as a barrier to their movement (Zug 1983).

Even in their native range, cane toads have a propensity to congregate in disturbed habitat and are often found in greater densities in human-modified areas. Cane toads tolerate conditions few amphibians can, and have even been shown to survive in water up to 40% sea water (Liggins and Grigg 1985). Their tolerance for a wide range of salinity levels is expected to facilitate their spread in parts of Australia (Wijethunga et al.

2016).

Female cane toads lay between 8,000 and 30,000 eggs per clutch (Lever 2001).

They are highly toxic during the majority of their life cycle; eggs, tadpoles, subadults, and adults are poisonous to many potential predators. There is a lapse in toxicity from metamorphosis to subadulthood, however, when cane toads lose the toxicity of earlier phases but have not yet developed enlarged parotoid glands (Zug and Zug 1979). As adults, parotoid glands secrete poison and can burst when pressure is applied (i.e., the jaws of a predator). Though this toxicity has had strong deleterious effects on predators in the cane toad’s introduced range (e.g., Letnic et al. 2008; Crossland and Shine 2010;

Price-Rees et al. 2010; Shine 2010), several species prey on cane toads with impunity in their native range. Zug and Zug (1979) hypothesized that numerous mammals, birds, reptiles, and amphibians eat cane toadlets, though adults likely have few predators.

One of the most significant predation threats for cane toad tadpoles and metamorphs comes from larger conspecifics. There are few limitations to the cane toad diet. In addition to smaller cane toads, they consume invertebrates and a variety of small vertebrates. Ants and beetles make up the majority of their diet (Zug and Zug

1979). However, they capitalize on other food sources when available, eating food set

out for pets and even scavenging meals in garbage (Lever 2001). This ability to consume such a wide range of foods is likely a factor in their capacity to thrive as commensals of man.

The prevalence of cannibalism among cane toads affects activity patterns. Like other Bufonidae species, cane toads are primarily nocturnal; however, activity period varies with age. Adult and subadult cane toads are generally active at night, but metamorphs are diurnal. This shift in activity period protects toadlets from larger, cannibalistic conspecifics (Pizzatto et al. 2008).

Global Invasions

Cane toads have been introduced to numerous locations around the world, both accidentally and intentionally (Lever 2003). The biggest driver behind these introductions was biological pest control, often aimed at pests of sugar cane crops.

Their efficacy as pest control was severely limited by a number of factors. High levels of toxicity, adaptability, and tolerance for a large variety of habitats and conditions have enabled them to thrive in various habitats and, in certain ecosystems, proven devastating for native fauna (e.g., Letnic et al. 2008; Crossland and Shine 2010; Price-

Rees et al. 2010; Shine 2010). Due to their incredible success outside of their natural habitat, cane toads have been added to the IUCN’s list of the world’s 100 most injurious invasive species.

Cane toads are established in Puerto Rico, Hawaii and Florida, many Caribbean islands, and a number of Pacific islands (Lever 2001). The cane toad’s impact in

Australia is particularly noteworthy. They were deliberately introduced in the 1930s in a misguided attempt to control the sugar cane beetle. As generalist feeders, cane toads quickly strayed from sugar cane fields and have continued to expand their range. Their

invasion front is advancing at approximately 55 km per year, with individual toads achieving distances of over 250 m per night (Phillips et al. 2007); they have colonized a wide variety of habitat types (Lever 2001). Australia has no native bufonids, and many potential predators had no behavioral or physiological adaptations for dealing with cane toad toxin. Quolls, goannas, and freshwater crocodiles are among the predator species whose populations plummeted upon the arrival of the cane toad invasion front (e.g.,

Letnic et al. 2008; Crossland and Shine 2010; Price-Rees et al. 2010). However, there is evidence that some predators can learn to avoid the toxins and some populations have rebounded following initial declines (e.g., Webb et al. 2008; O’Donnell 2010).

Nonnative populations of cane toads in Australia have colonized both natural and disturbed habitat, but occur more frequently in human-modified areas (Lever 2001). A recent study suggests this stems at least partially from increased prey availability, allowing cane toads to consume the same amount of food while remaining relatively sedentary. The same study also found that toads in natural areas were at increased risk of desiccation (Gonzalez-Bernal 2016).

Cane toads outside of their native range have demonstrated an incredible ability to adapt to novel conditions. For example, cane toads in Australia have invaded regions considerably drier than they encounter in their native range. Studies suggest they vary activity patterns to avoid conditions that would lead to desiccation (Brown et al. 2011), and that populations in areas with differing water availability have diverged and are now distinctly different in regards to their abilities to function in arid conditions (Tingley et al.

2012).

Ecology in Florida

In Florida, cane toads did not become established when they were introduced for pest control in 1936 (Easteal 1981). Instead, current populations seem to be the result of an accidental release of about 100 toads by a pet importer at Miami International

Airport in the 1950s; there have been other accidental and deliberate releases by pet traders since that original incident (King and Krakauer 1966).

Cane toad toxicity has been responsible for much of the impact this species has had in its nonnative range, as potential predators are poisoned by the novel prey. In

Florida, mortality rates for other anurans that attempted to eat cane toad eggs in a laboratory experiment ranged from 0% (eastern narrowmouth toad, Gastrophryne carolinensis) to 100% (green treefrog, Hyla cinerea) (Punzo and Lindstrom 2001).

Several native species have been documented eating cane toads with no apparent ill effect; Blue Jays (Cyanocitta cristata), Northern Mockingbirds (Mimus polyglottos), eastern hognose snakes (Heterodon platirhinos), southern water snakes (Nerodia fasciata), ribbon snakes (Thamnophis sauritus), garter snakes (Thamnophis sirtalis), eastern indigo snakes (Drymarchon couperi), and Virginia opossums (Didelphis virginiana) have all been observed preying on cane toads (Meshaka 2011).

Some researchers have indicated that cane toads in Florida are most commonly found in backyards or around canals and ponds (Krakauer 1968), others have noted they were most common in urban and agricultural lands (Wilson and Porras 1983), and others have pointed to rural subdivisions, school campuses, and golf courses as preferred habitats (Meshaka et al. 2004). The general consensus is that cane toads have not colonized Florida’s natural areas. However, the Herpetofaunal Inventories of the National Parks of South Florida and the Caribbean, a series a reports from the

USGS based on surveys from the early 2000s, found evidence of cane toads in natural areas. Cane toads were detected in Biscayne National Park (BNP), Everglades National

Park (ENP), and Big Cypress National Preserve (BCNP) (Rice et al. 2004, 2005, 2007).

All toads detected in ENP and BCNP were found during aural surveys, and none were encountered during visual surveys. The authors suggested that the low number of records and the lack of visual encounters meant that cane toads were just beginning to invade the parks. The surveys also determined that cane toads are active year round in south Florida, and humidity seems to be a driving factor in determining when they vocalize (Rice et al. 2007).

Research Design and Thesis Structure

The cane toad invasion in Australia has been the subject of a considerable amount of research. The status of cane toads in Florida, where they have been established for over sixty years, has received significantly less attention from the scientific community and the general public. The goal of my research was to address two fundamental questions regarding cane toads and invasion ecology, the results of which can inform management decisions and direct future research. Chapter two presents a survey of natural areas and nearby disturbed habitat to identify habitat disturbance levels vulnerable to cane toad colonization. Chapter three includes a collection of records compiled from a variety of sources to create an updated distribution map for this species. Finally, Chapter four outlines priorities for future research on cane toads in Florida.

CHAPTER 2 PRESENCE OF CANE TOADS ALONG A DISTURBANCE GRADIENT IN FLORIDA

Introduction

Invasive species are widely considered one of the greatest drivers of global biodiversity loss (e.g., Simberloff 1997; Wilcove et al. 1998). Although only a small proportion of introduced species successfully establish and proliferate, those that do can negatively impact native species and significantly alter ecosystems (Lodge 1993;

Mack et al. 2000). They compete with native species through direct interference or competition for resources and may also prey on native species. In some cases, they can even disrupt fundamental ecological processes, such as fire, hydrology, and nutrient cycling (Mack et al. 2000; Ehrenfeld 2003). In addition to the environmental effects of invasive species, invaders generate staggering economic losses. Costs of restoring invaded habitats are an important component of this cost, and invasive species are known to directly impact the economy by, for example, causing power outages or reducing property values (Burgio et al. 2014; Sin and Radford 2007). A 2005 study found that in the United States alone, 50,000 invasive species generated $120 billion in environmental damage annually (Pimentel et al. 2005).

Numerous nonindigenous species have been introduced in Florida, and the state leads the nation in the number of nonindigenous reptile and amphibian species by a wide margin (Butterfield et al. 1997; Krysko et al. 2011). There are several known introduction pathways, but the vast majority of introduced herpetofauna in Florida arrive through the pet trade (Krysko et al. 2011). Though some have little obvious impact, others have significantly affected native species. A fundamental step in identifying the effects of nonindigenous species and developing management strategies is creating an

understanding of which habitats are vulnerable to invasion by a given species. Although the majority of introduced amphibians and reptiles in Florida are exclusively associated with human-modified sites, some species have colonized natural areas (Butterfield et al.

1997; Krysko et al. 2011). Cuban treefrogs (Osteopilus septentrionalis), though they occur in greater densities in disturbed habitat, can be found in much of Everglades

National Park in a variety of habitat types (Meshaka 2001). Burmese pythons (Python bivittatus) have thrived in the Florida Everglades, to the severe detriment of native fauna

(McCleery et al. 2015).

Cane toads (Rhinella marina) are one of four nonnative anuran species known to be established in Florida (Krysko et al. 2016). The largest member of the family

Bufonidae, adults of this species have large parotoid glands that produce poison and protect them from most potential predators. Cane toads are incredibly prolific breeders, with females capable of laying 8,000-30,000 eggs (Lever 2001). They are generalist feeders that will eat nearly anything (Zug and Zug 1979). While invertebrates compose the majority of their diet, they have been documented eating small vertebrates, pet food, garbage, and even human feces (Lever 2001). Cane toads in their native range occupy a variety of open habitat types, often occurring in greater densities in human-modified areas (Zug 1983). These characteristics have undoubtedly been responsible for much of their success as an introduced species. Globally, they are among the most successful invasive species, having colonized a wide variety of locales far from their native range. Native to extreme southern Texas through Central and tropical South

America, cane toads are now established in Australia, Hawaii, Florida, and numerous

Caribbean and Pacific islands (e.g., Easteal 1981, Lever 2001). Many of these

populations were deliberately introduced for biological pest control in an attempt to alleviate the impacts of beetles and other insect pests in sugar cane fields. Following many of these introductions, cane toads strayed from agricultural areas and have continued to spread. The pet trade has, both deliberately and accidentally, been responsible for the remaining introductions (Lever 2001; Easteal 1981).

Cane toads have been ecologically devastating in parts of their nonnative range

(Lever 2003); their colonization of Australia is particularly well-documented. Introduced in the 1930s, they continue to expand their range in Australia (Phillips et al. 2007). High levels of toxicity, adaptability, and tolerance for a large variety of habitats and conditions have enabled them to thrive in a variety of habitats and, in certain ecosystems, proven devastating for native fauna; several native predator species in Australia have shown marked declines in the presence of this novel toxic prey (e.g., Letnic et al. 2008;

Crossland and Shine 2010; Price-Rees et al. 2010; Shine 2010). Due to their incredible success outside of their natural habitat, cane toads have been added to the IUCN’s list of the world’s 100 most injurious invasive species.

Florida’s cane toads have not been nearly as extensively studied as their

Australian counterparts. They were initially introduced to the state in several agricultural areas in the 1930s and 40s to combat sugar cane pests, but those introductions failed

(Easteal 1981). Cane toads did not become established in Florida until a pet importer accidentally released 100 individuals at Miami International Airport in 1955. Pet dealers were responsible for additional releases in Broward and Dade Counties within the following decade (King and Krakauer 1966). Although they have spread through much of south and central Florida, declines in native predators have not been documented.

Blue Jays (Cyanocitta cristata), Northern Mockingbirds (Mimus polyglottos), eastern hognose snakes (Heterodon platirhinos), southern water snakes (Nerodia fasciata), ribbon snakes (Thamnophis sauritus), garter snakes (Thamnophis sirtalis), eastern indigo snakes (Drymarchon couperi), and Virginia opossums (Didelphis virginiana) have all been observed preying on cane toads with no apparent ill effect (Meshaka 2011).

However, an examination of the effects of cane toad toxicity on native anurans feeding on cane toad eggs found mortality rates ranging from 0% (eastern narrowmouth toad,

Gastrophryne carolinensis) to 100% (green treefrog, Hyla cinerea) in a laboratory experiment (Punzo and Lindstrom 2001). While some native species can tolerate cane toad poison, others have been shown to be vulnerable to their toxicity. Potential impacts on these and other native species cannot be studied or anticipated without an understanding of habitat overlap. In other words, we must know which habitat types cane toads colonize to know the species with which they co-occur in order to anticipate effects on native species.

Current evidence suggests cane toads in Florida are generally limited to human- modified regions. Some researchers have indicated that cane toads in Florida are most commonly found in backyards or around canals and ponds (Krakauer 1968), others have noted they are most common in urban and agricultural lands (Wilson and Porras

1983), and others have pointed to rural subdivisions, school campuses, and golf courses as preferred habitats (Meshaka et al. 2004). The general consensus is that cane toads have not colonized Florida’s natural areas. If cane toads are constrained to disturbed habitat, the degree to which they can affect native species is limited.

However, many existing records are results of chance sightings in yards and other

populated sites, and natural areas have not been comprehensively sampled with an approach designed to target cane toads.

A significant exception to the assertion that cane toads are absent from natural areas comes from the Herpetofaunal Inventories of the National Parks of South Florida and the Caribbean. This series of reports from the USGS, based on surveys from the early 2000s, found evidence of cane toads in natural areas. Cane toads were detected in Biscayne National Park (BNP), Everglades National Park (ENP), and Big Cypress

National Preserve (BCNP) (Rice et al. 2007, 2004, 2005). Notably, all cane toads were found during aural surveys and none were encountered during visual surveys. The authors suggested that the low number of records and lack of visual encounters meant that cane toads were just beginning to invade the parks. If, a decade later, cane toads are established in the park or other natural areas, researchers must begin to re-evaluate potential effects on native species. The results of these surveys indicate that further assessment of cane toad invasion in Florida is necessary and that acoustic monitoring is the preferred method through which to do so. Other work has found that autonomous recording units (ARUs), which allow for monitoring throughout the night, can detect species that traditional manual call surveys might miss (Bridges and Dorcas 2000).

The primary objective of my study was to determine whether cane toads have colonized natural areas in Florida. To understand their potential role in Florida’s ecosystems, it is important to enhance our understanding of cane toad habitat use.

Since there is no clear-cut distinction between natural and disturbed habitat, I examined the occupancy of cane toads along a disturbance gradient. I deployed autonomous recording units (ARUs) in several south and central Florida natural areas and

surrounding locations to determine which levels of disturbance are vulnerable to cane toad colonization.

Materials and Methods

Study Sites

I surveyed a total of five natural areas and surrounding habitat in Florida. Study areas included Flatwoods Park (Thonotosassa, Hillsborough County), Archbold

Biological Station (Venus, Highlands County), J.W. Corbett Wildlife Management Area

(West Palm Beach, Palm Beach County), Picayune Strand State Forest (Naples, Collier

County) and Everglades National Park; these areas (Figure 2-1) were chosen for their proximity to disturbed habitat where cane toads are known to be prevalent (Figure 2-2).

The sites comprise numerous habitat types and represent a latitudinal gradient. Table 2-

1 includes descriptions of study areas.

Autonomous Recording Units

I deployed autonomous recording units (ARUs; Song Meter SM2(+), Wildlife

Acoustics; SMXII microphones, sensitivity -36+/-4dB; SNR>62dB) in natural areas and nearby disturbed habitat in 2015 and 2016 (Table 2-2). Units were spaced at least 800 m apart to ensure independence, as per the North American Amphibian Monitoring

Protocol (NAAMP 2001). The ARUs were programmed to record for five minutes each hour from sunset to sunrise, with coordinates programmed in to enable start time to change with time at sunset. All units were deployed near water bodies of varying size and hydroperiod (i.e., a range of potential cane toad breeding sites); since some were ephemeral, standing water was not continually present at all sampling locations during the study period. Habitat where I deployed ARUs was highly variable, and sampling locations were not selected to represent specific habitat types. Instead, ARUs were

placed at designated levels of habitat disturbance. Specific sites were chosen based on the presence of a water body and accessibility.

Disturbance Levels

Each ARU location was categorized based on level of disturbance. I chose a categorical gradient to avoid assumptions inherent in many numerical gradients. For example, other authors have used percent impervious surface to develop disturbance gradients (e.g., Gergel et al. 2002). Since it is unclear which facet of disturbed habitat has allowed cane toad populations to thrive in human-modified habitat (e.g., impervious surface, water and prey availability, predator density, open areas), a gradient constructed along any one feature could fail to incorporate the effects of the others. A gradient established by percent impervious surface would lead agricultural areas to be considered relatively natural, an inaccurate representation of this habitat type.

Disturbance levels chosen for this study included natural, semi-natural, agricultural, rural, and urban. Brief descriptions of categories can be found in Table 2-3.

Although it is difficult to truly call habitat undisturbed and virtually impossible to account for all past land use, sampling locations designated “natural” contained no obvious human modification. There were no clearings or structures, and no artificial bodies of water. While hydrology has been dramatically altered throughout southern

Florida (e.g., Skylar et al. 1999), a sampling location could be considered natural unless hydrological modification created an artificial body of water. Semi-natural habitats were sites with primarily natural conditions, but with more alteration to hydrology or vegetation cover. These sites contained small clearings, canals, or other sources of water, but did not contain structures. Agricultural sampling locations contained both crop and pasture sites. All pastures were cattle pasture and supplied a constant water

source. Rural and urban categories were delineated based on the density of structures, following the cutoff of two per acre outlined by Kawula (2009) in the Florida Land Cover

Classification System report by the Florida Fish and Wildlife Conservation Commission

(Low Intensity Urban vs. Urban in that report). Land cover type was determined in the field and using Google Earth. Categories were assigned based on land cover within a

400 m radius of the sampling location. This corresponds with the 800 m ARU separation required by the sampling protocol. Furthermore, a cane toad call is approximately 85dB

(Beard et al. 2015). Microphones had a signal-to-noise ratio of >62 dB, meaning that sounds below 32 dB are indistinguishable from microphone noise. Using the equation for propagation of sound, Lp = Lw - 20 log(r) + K', where Lp is sound pressure at distance, Lw is sound pressure at source, r is distance, and K’ is a constant, the maximum radius at which the ARUs can detect a cane toad is 125.89 m. This is a simplification, as multiple calling toads would increase this radius, but vegetation and other obstacles would decrease this value significantly. However, it provides a strong baseline and a cane toad calling from outside this radius would be extremely faint, and unlikely to be detected by an ARU.

Because my focus was to determine if cane toads have colonized natural areas, more ARUs were deployed in natural habitat than within the other disturbance categories (Table 2-4). Not all disturbance levels were represented at all study areas, as

I was limited by availability of habitat types.

Song Scope

I used Song Scope® software (Version 4.1.3A, Wildlife Acoustics) to analyze recordings and identify cane toad calls. Using cane toad calls recorded with an ARU in

Lake Placid, FL, I developed an automated recognizer to screen all files (Sample rate

5000Hz, FFT size 32, FFT overlap 3/4). Cutoffs for evaluation metrics were set low to reduce type II error (Quality=20, Score=50). I then manually evaluated recognizer results to confirm or deny the presence of calling cane toads. To confirm that environmental conditions were appropriate for breeding bufonids during my study period, I also scanned all files with a recognizer for native southern toads (Anaxyrus terrestris).

Occupancy Modeling

Occupancy modeling was conducted using the package unmarked in program R.

Separate single-season, single-species occupancy models were run for the 2015 and

2016 sampling seasons (Mackenzie et al. 2002; Mackenzie et al. 2005). Data from 2015 were truncated to 22 Jun. through 22 Sept. to limit to one season and because all calling fell within this period. Models for 2016 included 24 Mar. through 17 Jul. because

ARUs were deployed at all sites for this period. Disturbance level was used as a site- level covariate, with levels converted to ordinal factors. For each season, I ran a model with all five disturbance levels and another with disturbance levels collapsed into binary natural (disturbance level 1) and disturbed (disturbance levels 2-5) categories. Although presence of cane toads along the disturbance gradient was of interest, including all categories in the models resulted in relatively small sample sizes. I included rainfall as an observation-level covariate since rainfall drives cane toad breeding behavior (Zug

1983). The one-month standardized precipitation index (SPI) was also included since generally wetter or drier conditions may have an effect on breeding behavior that a single heavy rain or brief dry period cannot account for. I acquired rainfall data from the following sources: Weather Underground, a website that compiles data from numerous weather stations; the Archbold Automated Weather Station; the NOAA Archbold

Reserve CRN station; and South Florida Information Access (SOFIA), a network of weather stations run by the USGS in the Everglades. For each ARU, I used weather data from the nearest available weather station because rainfall in Florida is often patchy. Standardized precipitation index data were downloaded from the NOAA Climatic

Data Center.

Results

I collected and analyzed a total of ~6646 hours of recordings (1.1TB). Results are summarized in Table 2-5. Cane toads were detected 111 times out of a total of 7976 recording nights. There was at least one detection at nine ARUs. With the exception of

Flatwoods Park, cane toads were regularly heard at a minimum of one sampling location per study area. All sites where cane toads were detected on more than one night were disturbance level 5 (urban) or 3 (agricultural). The site with the highest proportion of total nights with detections (0.359) was a filter pond in an urban area of

Naples; detections were much lower at other sites with multiple hits (0.128, 0.117,

0.083, 0.167, 0.072). I detected a single cane toad calling at only one natural sampling location (disturbance level 1), but the call was so faint I believe it came from the adjacent agricultural area just outside the radius used to identify habitat type and the record was excluded from further analyses. There were two other sites where cane toads were detected only once: one disturbance level 4 (rural) and one level 2 (semi- natural). These hits were also discarded from further analyses. Single records out of so many replicates are likely indicative of itinerant toads rather than resident populations or individuals and generate an artificially low detection probability, which would cause models to over-predict occupancy state. Data from Flatwoods Park were excluded from

analysis because no cane toads were detected at any sampling location within that study area.

Occupancy Modeling

Detection probability was 0.127 (SE=0.0229) for the 2015 season and 0.169

(SE=0.0183) for 2016. Naïve occupancy estimates were 0.111 (SE=0.0606) and 0.122

(SE=0.057), respectively. Rankings for occupancy models with five separate disturbance levels are found in Table 2-6 and Table 2-7. However, they generated extremely high standard errors for occupancy state (2015: 109, 226, 236, 252, 258;

2016: 25.8, 42.5, 35.9, 80.8, 60.9). I therefore used models with binary disturbance level to predict occupancy state (Table 2-8, 2-9). The best model for 2015 yielded an occupancy state of 0.200 (SE=0.103) for disturbed habitat and 7.05E-05 (SE=0.002428) for natural habitat. Occupancy state for 2016 was 0.223765 (SE=0.098616) in disturbed habitat and 0.000234 (SE=0.003952) for natural areas. Although these are reasonable estimates, the range of lower and upper limits in natural areas suggest poor model fit

(Table 2-10).

Recognizer Performance

The automated recognizer yielded numerous false positives. Large volumes of background noise, much of which falls within the frequency range of cane toad calls, triggered many of the false positives. Leopard frog (Lithobates sphenocephalus) and eastern screech owl (Megascops asio) calls generated many of the false positives with the highest scores. Call duration was the best indicator of a true positive. Analysis was not designed to evaluate the efficacy of the program or the recognizer. The recognizer for southern toads had considerably fewer false positives than that for cane toads.

Native southern toads were detected at a minimum of one ARU of disturbance level 1

per study area. I also detected them calling in disturbed habitat. They regularly called at an urban site by ABS where cane toads were also detected.

Discussion

Occupancy models that included all five disturbance categories resulted in extremely high standard error. I therefore focused on the models using binary natural or disturbed habitat to predict occupancy state. As expected, occupancy for disturbed habitat was much higher than that predicted for natural habitat. The best model for the

2015 season included disturbance level as a site-level covariate and no observation covariates, whereas disturbance level combined with rainfall constituted the top model for 2016. Standardized precipitation index models consistently performed poorly, so this variable seems to play a negligible role in determining when cane toads call. Short-term rainfall is considerably more important. However, models combining the effects of rainfall and SPI suggest that the combined effects may play a role. Though predicted values for occupancy state make intuitive and biological sense, the range identified by the upper and lower limits indicate that there is still considerable variation that has not been accounted for. Detectability was low for both seasons due to the nature of the sampling method and cane toad breeding behavior. Call surveys have detected cane toads in habitats where other methods have failed, but calling is sporadic and in this case appears to have only tenuous connections to observation-level environmental covariates. Because calling was limited to disturbed habitat and the connection between disturbance level and occupancy should be strong, there is likely an observation covariate causing heterogeneity in detectability that was not identified. It is also possible that there is an element of stochasticity driving calling that produces heterogeneity in detection probability that cannot be accounted for in an occupancy model. Because this

possibility would violate an assumption of occupancy modeling, I conducted logistic regressions for each season using rain as a covariate; I ran models with five disturbance levels and with binary categories. However, this method also produced high standard errors so I did not pursue it further.

Although quantitative analyses were unable to account for all variation in calling behavior, the results of this study provide compelling evidence that cane toads have a strong affinity for high levels of disturbance and only rarely occur in natural and semi- natural habitat in Florida. I regularly detected cane toads at the highest disturbance level and only occasionally at all other levels. I do not suggest that there are no cane toads in natural habitat nor that they are incapable of surviving there, but found no indication that they are currently established in natural areas. In their herpetofaunal inventories of Everglades National Park and Big Cypress National Preserve, Rice et al.

(2004, 2005) suggested that the low densities of cane toads they identified were indicative of cane toads beginning to invade the park. A decade later, my year-long survey of ENP uncovered a single calling individual at just one ARU. This toad was detected at the Eco Pond, a location deep within the park. However, the pond is less than a mile from a popular boat ramp and visitor’s center, making it a likely spot for a hitchhiking cane toad to arrive. This does not indicate that cane toads are penetrating natural areas; rather, a few individuals may have been inadvertently transported or have strayed into the park. It appears they can survive within the park, but are unlikely to select habitat in natural areas. In addition, although they are not specifically targeting cane toads, other researchers conducting herpetofaunal surveys have rarely encountered cane toads in natural areas. For example, Florida Fish and Wildlife

Conservation Commission (FWC) herpetologists conducted dip net surveys, call surveys, and road surveys from July 2010 through Dec. 2014 in north and central

Florida. Extensive surveys in central Florida, including Highlands County where cane toads are established (Enge et al. 2014), uncovered only one cane toad in a semi- natural habitat and none in natural areas (pers. comm. Kevin Enge). ARU surveys in

Picayune Strand State Forest during the summers of 2010 and 2011, designed to monitor the effects of restoration on anuran communities, did not yield any cane toad detections (Walls et al. 2014). These results provide further evidence that cane toads rarely inhabit natural habitat in Florida, more than fifty years after establishment.

An important assumption for this study was that conditions were appropriate for cane toads to call. Though I detected very few in natural areas, cane toads were detected calling at four of the five study areas, suggesting that breeding was not limited by weather conditions. I eliminated data from Flatwoods Park because I did not detect any cane toads for the duration of the sampling period and this could indicate inadequate conditions for breeding. However, six of the eight ARUs were deployed in natural habitat and I was unable to establish a full disturbance gradient; there were fewer disturbed sites that could be used to confirm calling. Nevertheless, it is notable that no cane toads were recorded calling within the relatively small (5400 acres) park, particularly during a wet summer (One month standardized precipitation index Jul.

2015=0.76, Aug. 2015=1.3). J.W. Corbett and ENP experienced dry conditions in the summer of 2015, but I detected cane toads calling at both urban sites near Corbett and heard cane toads calling in an agricultural field near ENP during the same period; this suggests that weather was not a limiting factor for cane toad calling. Like Flatwoods

Park, Archbold received plentiful rain; a graphical depiction of weekly rainfall and cane toad calling can be found in Appendix A (Table A-1). Finally, southern toads were detected at multiple natural locations within each study area, further suggesting environmental conditions would not have limited cane toad calls during the study period.

Because there is strong evidence that cane toads are not established in natural areas, the greatest threat posed by cane toads in Florida continues to be to domestic dogs and cats, as well as native species that frequently occur in disturbed habitat.

Species with which cane toads are most likely to co-occur in significant numbers in

Florida are generalists that can live in urbanized areas. Southern toads are the most similar native species, and reports have indicated that the smaller native species begins to disappear when cane toads arrive. Fortunately, there is no evidence that southern toad populations are in decline in natural areas or in parts of their range without cane toads (Lannoo 2005). Cane toads, like many successful introduced species, thrive in disturbed habitat, and ongoing habitat destruction will continue to confer a selective advantage on them at the expense of native species. If Florida’s human population grows and development continues at the projected rate, an estimated 2.8 million ha will be converted to urban habitat by the year 2060 (Zwick and Carr 2006). This figure includes some current agricultural land, but also substantial natural habitat. Land use change in Florida will therefore favor cane toads and other invasive species, and habitat type is unlikely to be a significant limiting factor to their range expansion.

A logical follow-up is to identify the reasons cane toads have not spread into natural areas in Florida. While they are certainly found in greater densities in residential areas in Australia, they have also colonized more undisturbed habitat. Numerous

factors could contribute to this dichotomy, including the presence of similar species.

While Australia has no native toads, Florida is home to three native bufonid species, two of which overlap in range with cane toads. Though they are smaller and less toxic than cane toads, predators have evolved in the presence of a similar potential prey item and are probably better adapted to handle it. However, although this difference explains why predators in Florida have not suffered the population crashes seen in Australia, it likely plays only a small role in rendering disturbance levels resistant or vulnerable to cane toad invasion in Florida. Several predators capable of consuming cane toads in Florida

(e.g., Blue Jays, Northern Mockingbirds, Virginia opossums; Meshaka 2011), frequent disturbed habitat. Furthermore, while predation pressure in natural areas by other species should be addressed, Zug (1983) noted that predation on adults and subadults in their native range is uncommon; this suggests that predators are unlikely to be a significant determinant factor in cane toad range.

A more likely explanation for cane toad habitat preference is prey availability.

Lights in human-modified areas attract insects which in turn attract cane toads. A recent study examining the higher density of cane toads near buildings in Australia found that inhabiting those areas allowed cane toads to consume the same amount of food while remaining relatively sedentary (Gonzalez-Bernal 2016). Since they also eat pet food and are otherwise opportunistic feeders, human-modified habitat provides constant food. Another factor driving cane toad habitat preference is water availability. Although water is readily available in many of Florida’s natural areas for much of the year, artificial water bodies common in disturbed habitat create ideal cane toad habitat. Ideal breeding sites are slow-moving bodies of water with gradual slopes surrounded by

cleared ground (Hagman and Shine 2006), conditions often fulfilled by artificial water sources. Finally, cane toads are averse to moving through densely vegetated areas, so disturbed human-modified areas reduce obstacles to movement (Zug 1983).

An interesting deviation from the trends identified by this and other studies is the prevalence of cane toads in Biscayne National Park. A 2007 report summarizing the results of extensive herpetofaunal surveys found naïve occupancy to be 37.8 percent, and the percent of area occupied estimate, which accounts for detectability, was 77.9 percent (SE = 0.1499) in the park as a whole (Rice et al. 2007). Occupancy estimation was considerably higher for mainland than island sites. This is likely the result of edge effects as the mainland portion of the park is narrow and abuts urban areas. Individuals on islands, whether they reached those areas through hitchhiking or other means, are less likely to leave once they have arrived in the natural area than those on the mainland. Cane toad invasive potential may therefore be different on islands off of

Florida where humans may accidentally transport them.

It is worth noting that disturbance levels were chosen based on the habitat type immediately surrounding each ARU. I did not account for barriers to cane toad movement or other dispersal limitations. Cane toads have been known to travel along roads (Brown et al. 2006) and spread via canals (Krakauer 1968), but do not move through dense vegetation (Zug 1983). Presence of these movement corridors could affect the chance of cane toads arriving to a site, regardless of habitat type. Dispersal limitations may explain why I did not detect many in rural, the second most disturbed, sites. Several of the rural sites are in isolated areas where cane toads are unlikely to arrive but could flourish if it became more easily accessible or they arrived via another

vector. Methods of dispersal are beyond the scope of this project, and future studies should examine the role of roads and canals in the spread of this species. Regardless, in many instances roads are highly correlated with level of habitat disturbance. Though the results of my thesis do not signify that cane toads are incapable of colonizing undisturbed habitat, there is no evidence that they are currently established in natural areas in Florida.

A focus in invasion ecology has been to understand the factors that enable a species to invade another ecosystem in an effort to better predict and prevent future invasions. The success or failure of an invader is determined by a suite of factors ranging from species traits, to the characteristics of the invaded ecosystem, to traits of the particular individuals introduced to the ecosystem (Kolar and Lodge 2001). Some potential predictors, such as species richness or presence of congeners in the invaded territory, have yielded different results across taxa and at different scales (Tingley et al.

2011; Kennedy et al. 2002; Fargione et al. 2003; Capers et al. 2007; Levine 2000).

However, a history of successful invasions and broad physiological tolerance have consistently proven strong predictors of likelihood of invasion success (Kolar and Lodge

2001; Ricciardi 2003). Another pattern that has consistently emerged across biomes indicates an increase in invasive species in disturbed landscapes. When human– mediated changes occur and native taxa cannot adapt, the ecosystem is vulnerable to nonindigenous species more capable of exploiting available resources (Hobbs and

Huenneke 1992). Due to the wide variety of ecosystems where they have been introduced around the world, cane toads are an ideal organism through which to study site-level factors that influence invasibility. Global comparisons of habitats they have

invaded, including the degree to which they have colonized natural areas, could provide valuable insight into the role habitat characteristics, native species, and myriad other local factors play in the establishment of a newly introduced organism.

Figure 2-1. Map of study areas. 1. Flatwoods Park 2. Archbold Biological Station 3. J.W. Corbett Wildlife Management Area 4. Picayune Strand State Forest 5. Everglades National Park

Figure 2-2. Cane toad distribution (2010). Map created by Steve A. Johnson and Monica McGarrity. Range in southwest Florida has expanded since this map was made and the population in the panhandle is likely extirpated.

Table 2-1. Descriptions of each of the study areas. Site Size (ha) Description Surrounding habitat Cane toad status Flatwoods Park 2,185 Mesic flatwoods, hydric hammock, Housing Numerous reports in basin swamp, cypress swamp, developments and surrounding area, no freshwater marsh (FCLCM…2015); residential known sightings within seven-mile paved loop trail for park cyclists throughout Archbold 3,577 Southern ridge sandhill, sand pine Agriculture, A few cane toads have Biological Station scrub, oak hickory scrub, rosemary including cattle and been found near scrub, scrubby flatwoods, flatwoods, citrus, low density- buildings at entrance to bayhead, and seasonal pond residential areas the station, but none ecosystems (ABS…2014); within natural habitat accessibility limited to sand trails, no public access J.W. Corbett 24,422 Mesic flatwoods, wet flatwoods, Agriculture, primarily Very common in nearby Wildlife freshwater marsh, strand swamp, citrus and other residential areas, no Management dome swamp (FCLCM…2015); one crops, expanding known records within Area long loop road through property; urban areas WMA popular site for hunters Picayune Strand 31,565 Cypress strands, wet prairie, pine Rural and urban Increasing reports from State Forest flatwoods, hardwood hammocks nearby Naples (PSSF…2012-2016); numerous roads (paved and dirt) throughout eastern half, but not maintained, popular for hunting and fishing Everglades 607,028 Hardwood hammocks, pineland, Agriculture, mostly Occasionally seen at National Park mangrove, coastal lowlands, crops, and visitors centers, common freshwater slough, freshwater marl numerous canals along canals just outside prairie, cypress, marine, and park estuarine (ENP…2016)

Table 2-2. Dates ARUs were deployed at each of the study areas. Site Dates Surveyed Number of ARUs Flatwoods Park 7/10/15-11/16/15 8 Archbold Biological Station 6/23/15-11/16/15 9 Archbold Biological Station 3/1/16-7/16/16 10 J.W. Corbett Wildlife Management Area 6/28/15-8/26/15 8 Picayune Strand State Forest 3/26/16-7/17/16 12 Everglades National Park 7/19/15-7/19/16 11 Some ARUs were not deployed for the entire duration of the sampling seasons because they malfunctioned or ran out of battery for a period. At a few sites, an additional ARU was added later in the sampling season.

Table 2-3. Descriptions of each of the disturbance levels. Disturbance Category Description Level 1 Natural Undisturbed habitat 2 Semi-natural Primarily undisturbed, but contains artificial clearing or water body; no structures 3 Agricultural Crop or pastureland 4 Rural Up to two structures per acre 5 Urban More than two structures per acre (Kawula 2009)

Table 2-4. Number of ARUs deployed at each disturbance level within each site. Site Dates Natural Semi- Agricultural Rural Urban Total natural Flatwoods 7/10/15-11/16/15 6 0 0 1 1 8 Archbold 6/22/15-11/16/15 4 0 1 2 2 9 Archbold 3/1/16-7/16/16 5 0 2 1 2 10 Corbett 6/28/15-8/26/15 3 2 0 1 2 8 Picayune 3/26/16-7/17/16 5 4 1 0 2 12 Everglades 7/19/15-7/19/16 5 3 1 2 0 11 Total 28 9 5 7 9 58 Archbold Biological Station (ABS) is listed twice because there were two distinct sampling seasons. Total is larger than the actual total number of ARUs deployed (55) because a few locations at ABS were surveyed both seasons.

Table 2-5. Summary of ARU Results. Site Location ID Disturbance Level Recording Hits Proportion Nights Flatwoods ID0001 1 122 0 0.000 Flatwoods ID0002 4 129 0 0.000 Flatwoods ID0003 1 130 0 0.000 Flatwoods ID0004 1 130 0 0.000 Flatwoods ID0005 1 130 0 0.000 Flatwoods ID0006 1 130 0 0.000 Flatwoods ID0007 1 82 0 0.000 Flatwoods ID0008 5 129 0 0.000 Archbold ID0009 5 104 0 0.000 Archbold ID0010 5 67 0 0.000 Archbold ID0011 5 235 30 0.128 Archbold ID0012 1 147 0 0.000 Archbold ID0013 1 114 0 0.000 Archbold ID0014 3 137 0 0.000 Archbold ID0015 3 138 0 0.000 Archbold ID0016 3 138 0 0.000 Archbold ID0017 1 262 0 0.000 Archbold ID0018 1 266 0 0.000 Archbold ID0019 1 64 0 0.000 Archbold ID0020 4 148 0 0.000 Archbold ID0021 4 143 1* 0.007 Archbold ID0022 4 138 0 0.000 Archbold ID0023 1 111 0 0.000 Archbold ID0024 1 127 0 0.000 Corbett ID0025 2 61 0 0.000 Corbett ID0026 5 60 7 0.117 Corbett ID0027 4 60 0 0.000 Corbett ID0028 1 28 0 0.000 Corbett ID0029 5 60 5 0.083 Corbett ID0030 1 33 0 0.000 Corbett ID0031 2 61 0 0.000 Corbett ID0032 1 61 1* 0.016 Picayune ID0033 2 91 0 0.000 Picayune ID0034 1 115 0 0.000 Picayune ID0035 2 99 0 0.000 Picayune ID0036 1 76 0 0.000 Picayune ID0037 5 103 37 0.359 Picayune ID0038 1 115 0 0.000 Picayune ID0039 3 71 0 0.000 Picayune ID0040 2 116 0 0.000

Table 2-5. Continued. Site Location ID Disturbance Level Recording Hits Proportion Nights Picayune ID0041 1 116 0 0.000 Picayune ID0042 5 114 19 0.167 Picayune ID0043 2 115 0 0.000 Picayune ID0044 1 110 0 0.000 Everglades ID0045 4 201 0 0.000 Everglades ID0046 4 364 0 0.000 Everglades ID0047 1 336 0 0.000 Everglades ID0048 1 246 0 0.000 Everglades ID0049 1 349 0 0.000 Everglades ID0050 1 318 0 0.000 Everglades ID0051 2 303 0 0.000 Everglades ID0052 2 342 1* 0.003 Everglades ID0053 1 322 0 0.000 Everglades ID0054 2 340 0 0.000 Everglades ID0055 3 139 10 0.072 Total 7976 111 0.014 A hit is a night (sunset to sunrise) in which at least one cane toad was detected. Number of recording nights varies within sites and seasons because of equipment malfunctions. These include all dates the units were running and are not limited by appropriate breeding weather. Asterisks denote sites with only one hit, and detection was removed for occupancy modeling.

Table 2-6. Model rankings for 2015, all five disturbance categories Model nPars AIC Delta AIC weight Cumulative weight Disturbance level 6 178.18 0.00 0.3443 0.34 Disturbance level, rain 7 178.30 0.12 0.3245 0.67 Disturbance level, rain, SPI 8 179.85 1.66 0.1500 0.82 Disturbance level, SPI 7 179.97 1.79 0.1406 0.96 Null 2 184.51 6.32 0.0146 0.97 Rain 3 184.63 6.44 0.0137 0.99 Rain and SPI 4 186.17 7.98 0.0064 0.99 SPI 3 186.29 8.11 0.0060 1.00 Top four models are good fits, all of which include disturbance level as a site-level covariate. Models including standard precipitation index performed poorly.

Table 2-7. Model rankings for 2016, all five disturbance categories Model nPars AIC Delta AIC weight Cumulative weight Disturbance level, rain 7 399.24 0.00 0.4989 0.50 Disturbance level, rain, SPI 8 400.01 0.77 0.3387 0.84 Disturbance level 6 402.67 3.43 0.0896 0.93 Disturbance level, SPI 7 403.92 4.68 0.0481 0.98 Rain 3 406.59 7.35 0.0127 0.99 Rain and SPI 4 407.37 8.13 0.0086 1.00 Null 2 410.03 10.79 0.0023 1.00 SPI 3 411.27 12.04 0.0012 1.00 Top four models are good fits, all of which include disturbance level as a site-level covariate. Models including standard precipitation index performed poorly.

Table 2-8. Model rankings for 2015, binary Model nPars AIC Delta AIC weight Cumulative weight Disturbance level 3 182.69 0 0.256 0.26 Disturbance level, rain 4 182.81 0.12 0.241 0.50 Disturbance level, rain, SPI 5 184.35 1.67 0.111 0.61 Disturbance level, SPI 4 184.47 1.79 0.105 0.71 Null 2 184.51 1.82 0.103 0.82 Rain 3 184.63 1.94 0.097 0.91 Rain and SPI 4 186.17 3.48 0.045 0.96 SPI 3 186.29 3.61 0.042 1.00 Models with disturbance level rank at the top, but there is no clear best model.

Table 2-9. Model rankings for 2016, binary Model nPars AIC Delta AIC weight Cumulative weight Disturbance level, rain 4 403.26 0 0.4309 0.43 Disturbance level, rain, SPI 5 404.04 0.78 0.2919 0.72 Rain 3 406.59 3.33 0.0817 0.80 Disturbance level 3 406.72 3.46 0.0765 0.88 Rain and SPI 4 407.37 4.11 0.0553 0.94 Disturbance level, SPI 4 407.95 4.69 0.0413 0.98 Null 2 410.03 6.77 0.0146 0.99 SPI 3 411.27 8.01 0.0078 1.00 Top two models are significant.

Table 2-10. Results for top ranked models for each season with binary habitat type Covariates Season Disturbance Predicted Standard Lower Upper level Error Disturbance 2015 Disturbed 0.200383 0.103481 0.06600747 0.470508 level Disturbance 2015 Natural 7.05E-05 0.002428 3.50E-34 1.00 level Disturbance 2016 Disturbed 0.223765 0.098616 8.65E-02 1.00 level, rain Disturbance 2016 Natural 0.000234 0.003952 1.03E-18 1.00 level, rain Occupancy estimates for each level of disturbance. Standard error is low, but the wide range for lower and upper values indicates poor model fit.

CHAPTER 3 CURRENT DISTRIBUTION OF CANE TOADS IN FLORIDA

Introduction

Cane toads are among the most successful introduced species in the world, having colonized many areas far from their native range. Their native range extends from extreme southern Texas through Central and tropical South America, but they are now established in Australia, Hawaii, Florida, and numerous Caribbean and Pacific islands (Lever 2001). Many of these populations were deliberately introduced for biological pest control to mitigate the impacts of beetles and other insect pests on sugar cane crops. The pet trade has, both deliberately and accidentally, been responsible for the remaining introductions (Easteal 1981; Lever 2001). Cane toads have an affinity for disturbed habitat in both their native and introduced range (Zug 1983). Despite being concentrated in human-modified habitat, they have been ecologically devastating in parts of their introduced range, largely owing to their toxicity. The largest member of the

Bufonidae, or true toad, family, adult cane toads have large, toxin-secreting parotoid glands that limit predation in their native range (Zug 1983). Female cane toads lay between 8,000 and 30,000 eggs per clutch (Lever 2001). Eggs and tadpoles are toxic to many species, though there is a brief lapse in toxicity after metamorphosis and before the development of enlarged parotoid glands (Zug and Zug 1979).

Colonization and impacts on native fauna have been particularly well- documented in Australia (Lever 2003; Shine 2010). Introduced in the 1930s, cane toads continue to expand their range in the country. Several native predator species have shown marked declines in the presence of this novel, toxic predator (e.g., Letnic et al.

2008; Crossland and Shine 2010; Price-Rees et al. 2010). While the invasion in

Australia has been the subject of a robust body of literature, cane toads in Florida have not been nearly as well studied. The first cane toad releases in Florida were for biological pest control in the 1930s. Two hundred cane toads from Puerto Rico, where cane toads had been introduced from other nonindigenous populations in the

Caribbean, were introduced near Canal Point and Belle Glade by Lake Okeechobee.

Within a decade, more cane toads were brought from Puerto Rico and introduced near

Clewiston. However, none of these introductions were successful (Easteal 1981). Cane toads did not apparently become established in Florida until a pet importer accidentally released 100 individuals at Miami International Airport in 1955. Additional releases occurred in Broward and Dade Counties in the early 1960s (King and Krakauer 1966).

By 1968, Krakauer reported that cane toads were sufficiently abundant in parts of south

Florida as to be a public nuisance (Krakauer 1968).

In parts of their introduced range, cane toad populations have expanded at incredible rates. The invasion front in Australia is progressing at 55 km per year, with some individuals regularly traveling more than 200 m in a night (Phillips et al. 2007).

Roads serve as movement corridors, allowing them to travel even more rapidly (Brown et al. 2006). Florida’s extensive network of roads could facilitate movement throughout much of climatically suitable habitat in the state, and it is therefore important to proactively search for records to maintain a current understanding of their distribution.

Potential impacts of this toxic invasive species on native fauna, as well as domestic animals, necessitate a comprehensive assessment of cane toad range. While predators in Florida have not experienced the declines witnessed in Australia, they are known to

be toxic to some native fauna (Punzo and Lindstrom 2001) and can pose a significant threat to domestic dogs (Johnnides et al. 2016).

The objective of this study was to determine the current distribution of cane toads in Florida and create an updated cane toad distribution map for use by land managers, researchers, and the public. Understanding range is a fundamental step for prioritizing management strategies or studies of interactions with native fauna. Because cane toads are so prevalent in human-modified areas, interactions with the public are common.

Treatment for dogs poisoned by cane toads can be highly effective if provided immediately (Johnnides et al. 2016). It is therefore essential that educational material disseminated to the public is current and thorough, as awareness of its presence is an important first step in reducing dog mortality following an attempt to eat a cane toad. I collected records from a variety of sources in order to determine distribution and update the range map for cane toads in Florida.

Methods

I compiled records from online databases, including the Florida Museum of

Natural History Herpetology Master Database

(https://www.flmnh.ufl.edu/herpetology/collection/database/), EDDMapS

(http://www.eddmaps.org/), and the USGS Nonindigenous Aquatic Species database

(https://nas.er.usgs.gov/Default.aspx). Each of these databases comprises records from a variety of sources, so I screened for and eliminated duplicates by excluding records with identical coordinates from the same year. I then evaluated records for establishment status. For records from the USGS, I relied on the provided establishment classification. Individual toads found far from established populations were not considered established. If I could not confirm status, as in the case of

individual toads found in counties adjacent to areas with established populations or populations reported in the past with no follow-up surveys, I designated the records

“unknown.”

I supplemented these data with records from citizen scientists. Because of the

University of Florida’s Extension program, I received regular emails from members of the public seeking assistance with anuran identification or wishing to report an invasive species. These records, with a photo voucher to positively confirm species identification and exact address, were included in the dataset. I also reached out to Florida Master

Naturalists (FLMN) and University of Florida County Extension Agents to request records from around the state. Participants in the FLMN program complete training modules on Florida ecosystems and conservation and are scattered around the state.

County Extension Agents are part of the University of Florida Institute of Food and

Agricultural Sciences, and have offices in every county. After compiling records, I mapped them in ArcMap 10.4. I then created maps highlighting only established records or areas with growing numbers of reports.

Results

I collected a total of 585 unique records with sufficient accompanying information.

The majority were from online databases, although 77 were from citizen scientists or

Master Naturalists. Forty-seven of the citizen science reports came from Lee or Collier

County in southwest Florida (Table 3-1); only 16 came from Broward or Miami-Dade

County in the southeast portion of the state, where cane toads have been established since the 1960s (King and Krakauer 1966). Overall, the earliest records from southwest

Florida available from the databases I included were reported after the year 2000. A

summary of citizen science records (Table B-1) and all records organized by county and decade (Table B-2) can be found in Appendix B.

The following maps illustrate the most significant findings from the records I collected. The first map (Figure 3-1) portrays all accurate records from all sources.

Locations are accurate for all included records, but records may or may not represent established populations. Figure 3-2 is limited to records from established populations. It includes a few records of unknown status, as I was unable to confirm establishment state for all records based on proximity to other populations or contacting other researchers. While most established records fell within areas cane toads were known to be established (e.g., Meshaka et al. 2011; Powell et al. 2016), I identified one new, likely established population in Volusia County. Because a majority of recent records came from southwest FL, I created detailed maps of that region to clearly depict the expansion of cane toad range in that part of the state. Figure 3-3 and Figure 3-4 highlight the stark contrast between the number of records reported prior to and after

2010.

Discussion

Distribution of an invasive species is rarely stagnant, as dispersal limitations and time can temporarily prevent an introduced species from colonizing appropriate, climatically suitable habitat. These factors should not be expected to constrain distribution indefinitely. Although cane toad range in Florida has not expanded dramatically in recent years, my results do highlight some regions where the number of populations has increased, as well as at least one new population that seems to have arisen. It is clear that although they have been established for over fifty years, cane toads have not yet reached the full extent of their potential range in Florida.

A comparison between Figure 3-3 and Figure 3-4 indicates that cane toad populations have increased in southwest Florida. Many of the records sent in by the public in the past two years came from this part of the state. While increased education and awareness likely play a role in the growing number of records in Lee and Collier

Counties, anecdotal accounts from people familiar with Florida anurans suggest that cane toads were rarely seen in southwest Florida until recent years (pers. comm. Jeff

Schmid, Conservancy of Southwest Florida). It is unclear how cane toads arrived in southwest Florida, as the population is disjunct from the rest of their range, the majority of which appears contiguous.

While cane toad populations in southwest Florida have clearly expanded, establishment status could not be confirmed for all records in other parts of the state.

Individual cane toads identified far from known populations were not considered established (e.g. Godwin et al. 2014; Somma and Merritt 2014); since cane toads are still in the pet trade, additional deliberate and accidental releases are inevitable.

However, reports of a small number of cane toads in a county adjacent to an area with established populations are more difficult to classify but could signify range expansion.

These areas should be closely monitored to determine if they were actually representative of populations. Cane toads have been reported outside of their confirmed distribution on both coasts (Figure 3-2). One population of uncertain status was originally reported at the site of a defunct zoo in Panama City, Florida in 2007 (Himes

2007). Unlike other records in north Florida, this was confirmed to be a breeding population and has been included in recent cane toad range maps (e.g., Powell et al.

2016). This would suggest an ability to colonize cooler climates and regions

considerably outside their current distribution. However, there have been no additional records from that location since the initial breeding was reported. John Himes, who made the initial report, believes they were unable to survive a cold winter and no longer inhabit the area. (pers. comm., John Himes). Nonetheless, systematic surveys should be conducted to confirm extirpation, due to the implications for cane toad thermal tolerance and potential range expansion. Another population that warrants further investigation was reported in Deland, Volusia County. This population was initially reported in 2012 (see specimens UF 166744 and 166745 in Florida Museum of Natural

History database) and was later revisited for a study on cane toad thermal sensitivity

(Mendonca and Dagg 2015). As with the Panama City population, established populations this far north are highly significant for our understanding of thermal limitation and regions vulnerable to colonization by cane toads.

Just as the status of certain records require further investigation, gaps in cane toad range need to be examined. Records of cane toads in Florida reveal conspicuous gaps in range. It is likely that some of these gaps are false negatives, and that low human population density or public awareness of this species allowed populations to go unreported. They may also indicate a lack of suitable habitat. However, large portions of southwest Florida are primarily composed of agricultural land, a habitat type in which cane toads have thrived in elsewhere in the state (Wilson and Porras 1983). Surveys must be conducted to determine whether cane toads are absent or simply unreported in these areas. Finally, some gaps indicate areas that cane toads have not yet colonized but might in coming years.

Identifying pathways of spread and expansion should be a priority for future analysis as the mode of expansion has implications for management and anticipating future spread. Range expansions could be the result of migrating individuals or new releases. Cane toads are known to use roads as movement corridors, and individuals in

Australia have been recorded traveling more than 200 m in a night (Phillips et al. 2007).

In Florida, spread from the initial introduction point was facilitated by construction of canals (Krakauer 1968). Canals or ditches could be an important factor in modern cane toad range expansion in the state. Genetic analyses should be conducted to examine disjunct populations; these results will enable researchers to determine if isolated populations stem from migrating individuals, hitchhikers, or separate introductions.

Cane toads thrive in disturbed or degraded areas, so there is an abundance of appropriate habitat for the species in Florida. The extensive network of roads and canals, as well as continuing propagule pressure, may eventually eliminate barriers to dispersal and climate will be the limiting factor in cane toad distribution. Cane toads, like many successful introduced species, thrive in disturbed habitat, and ongoing habitat destruction will continue to confer a selective advantage on them at the expense of native species. If Florida’s human population increases and development continues at the projected rate, 2.8 million ha of land will be converted to urban habitat. This includes some current agricultural areas, but a substantial portion is natural habitat. These land use changes will favor cane toads and other invasive species, eliminating habitat type as a factor constraining cane toad range expansion (Zwick and Carr 2016).

Temperature will likely be the limiting factor preventing expansion to the north. In their native range, temperature determines elevational limits; cane toads closer to the

equator can survive at greater altitudes due to warmer climates (Lever 2001). As climate change continues to increase temperatures, cane toads in Florida will likely be able to spread farther north. This emphasizes the important role temperature has played in determining cane toad range thus far, and that warmer winters could enable a range expansion. Species distribution models should be used to identify regions most vulnerable to cane toad invasion under current conditions and various climate change scenarios. This compilation of records provides an improved understanding of current cane toad range, but further research into methods of dispersal and climate limitations is necessary to identify areas vulnerable to cane toad colonization.

Figure 3-1. Accurate cane toad records from all sources, regardless of establishment status.

Figure 3-2. Established cane toad records only. Red triangles denote records of unknown establishment status.

Figure 3-3. Cane toad records from southwest Florida reported prior to 2010.

Figure 3-4. Records from southwest Florida reported from 2010-2016. Triangles denote citizen science reports from Jul. 2014 through Sept. 2016.

Table 3-1. Citizen science reports by county County Number of reports Proportion of total Lee 26 0.317 Collier 22 0.268 Broward 10 0.122 Miami-Dade 6 0.073 Palm Beach 5 0.061 Hillsborough 4 0.049 Pinellas 4 0.049 St. Lucie 2 0.024 Polk 1 0.012 Pasco 1 0.012 Martin 1 0.012 Total 82 Includes all verified records reported by the general public from Jul. 2014 through Sept. 2016. Total is greater than number included in maps (n=77) because some locations were not precise enough for mapping purposes, but county is known.

CHAPTER 4 FUTURE DIRECTIONS

My research provides strong evidence that cane toads have not colonized natural areas in Florida. I was also able to demonstrate that they continue to expand their range in certain parts of Florida. With these results, however, comes another suite of questions and variables that should be addressed in future studies. A priority for future analyses should be to address the question of why cane toads are largely absent in

Florida’s natural areas. While they display an affinity for disturbed habitat throughout their natural and introduced ranges, the factors controlling this pattern in Florida should be examined. Possible factors include predator and prey density, water availability, barriers to movement, and prevalence of potential breeding sites. Furthermore, though cane toads have not colonized natural areas, these results do not indicate that cane toads cannot survive in these habitats. Male cane toads could be radio-tagged, released, and traced through a variety of natural areas. Their behavior in these habitats could elucidate which factors limit their colonization of natural areas.

Studies of cane toad movement should also be used to examine the modes through which cane toad range is expanding. It is currently unclear how cane toads have spread, particularly to southwest Florida. Genetic analyses could determine whether the isolated population in this region arose from a separate introduction, as cane toads are still available through the pet trade, or spread there from another part of their range in the state. These analyses could help determine if cane toads are spreading via roads and other movement corridors. The role of roads could also be examined by fitting radio transmitters to toads to study their movements. In addition to facilitating movement around the state, roads may impact habitat choice on a local level.

My work defined habitat type independent of proximity to and density of roads. Although there is certainly a correlation between disturbance level and presence of roads, I did not directly address dispersal. Dispersal limitations could potentially be as important as the habitat type itself. Including road proximity as a variable is an important next step.

Cane toads, like many successful introduced species, thrive in disturbed habitat, and ongoing habitat destruction will continue to confer a selective advantage on them at the expense of native species. If Florida’s human population increases and development continues at the projected rate, 2.8 million ha of land will be converted to urban habitat.

This include some current agricultural areas, but a substantial portion is natural habitat.

These land use changes will favor cane toads and other invasive species, eliminating habitat type as a factor constraining cane toad range expansion (Zwick and Carr 2016).

I was also unable to account for variation in habitat type, as my study grouped habitat types into broad categories. I chose sites that seemed to be appropriate toad habitat, but they in no way represent the full range of habitat types in Florida. Future studies should consider specific habitat type, since there may be a natural area with conditions better suited for cane toad colonization. A large number of sites needs to be used so that occupancy modeling can be a viable method of analysis.

Another unanswered question is why there are such conspicuous gaps in cane toad range. A detailed habitat analysis may reveal why cane toads have not colonized certain parts of Florida. If there is appropriate habitat and climate, additional surveys should be conducted to ensure the apparent absence of cane toads in these areas is not an artifact of lack of sampling effort. There were several isolated sightings reported north of the regions where cane toads are established. I was unable to find evidence

that these came from established populations, but this does not necessarily indicate that all of these sightings were just individual toads. These locations should be monitored for additional records that signify a northern range expansion. Since temperature appears to be a limiting factor in cane toad range in Florida, future studies should address their thermal tolerance to better identify regions susceptible to cane toad invasion. Species distribution models can be used to identify climatically suitable habitat under various climate scenarios.

Finally, future research needs to study the impacts on native species. The results of my thesis strongly suggest cane toads are limited to disturbed habitat, but many native species live in these areas. Southern toads are generally common in human- modified habitat but are considerably less common in areas cane toads have colonized

(Lannoo 2005). Studies should address the reasons for these apparent declines, as they could be the result of direct predation or resource competition. Although their numbers are bolstered by populations in natural areas and parts of their range without cane toad presence, the effects of cane toads on southern toads and other native species that frequent disturbed habitat must be addressed. There are reports of several native species eating cane toads, and research should be conducted to determine how common these predation events are and how they affect the predators. It is possible that although some predators can tolerate them, cane toads are a poor food choice with deleterious long-term effects. There has also been little research regarding the frequency with which native predators consume cane toads. Feeding experiments would help determine whether predators preferentially select cane toads as prey items.

There are many areas of cane toad ecology in Florida that need to be studied.

Although they do not seem to be colonizing natural areas, they continue to spread and maintain the potential to impact native species. Continuing research is important in order to understand and mitigate the effects of this toxic invasive species.

APPENDIX A SUPPLEMENTAL GRAPH

Figure A-1. Weekly rainfall and deployment dates of ARUs at Archbold Biological Station during 2015. Rainfall from most central weather station for all ARUs was used for this graph, although daily rainfall used in models came from the closest station to each ARU. Horizontal lines represent individual units and tick marks indicate a cane toad was detected at least once that week. Gaps indicate the ARU malfunctioned.

APPENDIX B RECORDS

Table B-1. Summary of all cane toad records by county and decade. County 1950s 1960s 1970s 1980s 1990s 2000s 2010s Total Alachua 0 0 0 0 0 0 1 1 Bay 0 0 0 0 0 1 0 1 Brevard 0 0 0 0 0 1 0 1 Broward 0 2 0 0 2 8 39 51 Clay 0 0 0 1 0 0 0 1 Collier 0 0 0 0 0 2 40 42 Gilchrist 0 0 0 0 0 0 1 1 Hendry 0 0 0 0 0 6 1 7 Highlands 0 0 1 0 3 2 38 44 Hillsborough 0 0 11 0 4 2 14 31 Indian River 0 0 0 0 0 1 2 3 Lee 0 0 0 0 0 2 65 67 Manatee 0 0 0 0 0 0 1 1 Marion 0 0 0 0 0 0 1 1 Martin 0 0 0 0 3 1 2 6 Miami-Dade 1 31 20 0 26 18 133 229 Monroe 0 1 0 0 0 5 0 6 Nassau 0 0 0 0 0 0 1 1 Okeechobee 0 0 0 0 0 2 0 2 Orange 0 0 0 0 0 0 1 1 Palm Beach 0 0 2 0 1 3 38 44 Pasco 0 0 0 0 2 2 7 11 Pinellas 0 0 0 0 0 0 4 4 Polk 0 0 0 0 1 2 8 11 Sarasota 0 0 0 0 0 0 1 1 St. Lucie 0 0 0 0 0 0 14 14 Suwanee 0 0 0 0 0 1 0 1 Volusia 0 0 0 0 0 0 2 2 Total 1 34 34 1 42 59 414 585 Includes records from EDDMapS, Florida Museum of Natural History Herpetology Database, USGS Nonindigenous Aquatic Species Database, citizen scientists, and reports from other researchers. Biased by temporal and geographic variation in sampling effort.

Table B-2. All citizen science reports of cane toads from Jul. 2014 through Sept. 2016 Latitude Longitude Date Location County 1 25.488611 -80.4761111 7/16/2014 Homestead Miami-Dade 2 25.808192 -80.3577694 10/7/2014 Doral Miami-Dade 3 27.889736 -82.4978611 10/15/2014 Tampa Hillsborough 4 26.188769 -81.7733528 10/31/2014 Naples Collier 5 28.093097 -82.425875 11/15/2014 Lutz Hillsborough 6 26.105192 -80.1615667 12/7/2014 Fort Lauderdale Broward 7 26.292639 -80.2599222 2/27/2015 Coral Springs Broward 8 26.189806 -81.8034111 3/15/2015 Naples Collier 9 25.864786 -80.1903 4/9/2015 Miami Shores Miami-Dade 10 28.103008 -82.7385056 5/6/2015 Palm Harbor Pinellas 11 25.546 -80.394 6/19/2015 Princeton Miami-Dade 12 28.025686 -81.9780333 6/20/2015 Lakeland Polk 13 26.572417 -81.8706361 6/22/2015 Fort Myers Lee 14 26.430319 -82.1012139 7/13/2015 Sanibel Island Lee 15 27.284056 -80.3947194 7/18/2015 Port St. Lucie St. Lucie 16 26.018892 -80.1569222 7/20/2015 Hollywood Broward 17 26.051075 -80.4148278 7/29/2015 Pembroke Pines Broward 18 26.6282 -81.882754 8/1/2015 Fort Myers Lee 19 26.204494 -81.7902444 8/21/2015 Naples Collier 20 28.115894 -82.7191778 8/25/2015 Palm Harbor Pinellas 21 26.2295 -81.7238361 8/27/2015 Naples Collier 22 26.013839 -80.201425 9/19/2015 Hollywood Broward 23 26.148536 -81.8030444 9/22/2015 Naples Collier 24 26.541447 -81.8883306 9/25/2015 Fort Myers Lee 25 27.128453 -80.3329583 10/5/2015 I95 rest stop Martin 26 26.378775 -81.8280861 12/25/2015 Bonita Springs Lee 27 26.631882 -81.87969 1/1/2016 Fort Myers Lee 28 26.15932 -81.748675 1/22/2016 Naples Collier 29 26.5122 -81.9098361 5/1/2016 Fort Myers Lee 30 27.913381 -82.5182778 5/9/2016 Tampa Hillsborough 31 26.025125 -80.1373806 5/10/2016 Hollywood Broward 32 26.248722 -81.7825472 5/12/2016 Naples Collier 33 26.541447 -81.8883306 5/12/2016 Fort Myers Lee 34 26.122714 -80.3129694 5/12/2016 Plantation Broward 35 26.526872 -81.9079889 5/13/2016 Fort Myers Lee 36 26.481456 -81.8049389 5/13/2016 Fort Myers Lee 37 26.700103 -80.0345667 5/13/2016 Palm Beach Palm Beach 38 26.569975 -81.8856583 5/13/2016 Fort Myers Lee 39 26.201872 -81.8067194 5/13/2016 Naples Collier 40 26.663858 -81.8445278 5/14/2016 Fort Myers Lee

Table B-2. Continued Latitude Longitude Date Location County 41 26.6779 -81.7160417 5/14/2016 Fort Myers Lee 42 26.241614 -81.7588 5/14/2016 Naples Collier 43 26.73565 -80.1208833 5/15/2016 West Palm Beach Palm Beach 44 26.240725 -81.7768639 5/16/2016 Naples Collier 45 26.154164 -81.805675 5/17/2016 Naples Collier 46 26.026842 -81.6714333 5/17/2016 Naples Collier 47 26.064364 -81.6943861 5/17/2016 Naples Collier 48 26.587336 -81.8924333 5/18/2016 Fort Myers Lee 49 26.342325 -81.8047889 5/18/2016 Bonita Springs Lee 50 26.672767 -81.7528417 5/19/2016 Fort Myers Lee 51 27.215761 -80.3806306 5/19/2016 Port St. Lucie St. Lucie 52 26.359608 -81.8053389 5/19/2016 Bonita Springs Lee 53 26.617725 -81.8864972 5/19/2016 Fort Myers Lee 54 26.326956 -81.8018861 5/20/2016 Bonita Springs Lee 55 26.616514 -81.88625 5/20/2016 Fort Myers Lee 56 26.804861 -80.2342722 5/21/2016 West Palm Beach Palm Beach 57 26.969567 -80.0919444 5/22/2016 Tequesta Palm Beach 58 26.573849 -81.898917 5/31/2016 Ft. Myers Lee 59 26.265546 -81.6874 5/31/2016 Naples Collier 60 26.46824 -81.815167 5/31/2016 Ft. Myers Lee 61 26.649215 -81.719812 5/31/2016 Ft. Myers Lee 62 26.815693 -80.074742 6/2/2016 North Palm Beach Palm Beach 63 26.624305 -81.884709 6/3/2016 Ft. Myers Lee 64 26.309522 -80.295084 6/9/2016 Coral Springs Broward 65 26.265546 -81.6874 6/9/2016 Naples Collier 66 28.314812 -82.50208 6/10/2016 Land O' Lakes Pasco 67 26.185773 -81.801236 6/11/2016 Naples Collier 68 25.938641 -80.302196 6/12/2016 Hialeah Miami-Dade 69 28.017921 -82.693336 6/20/2016 Safety Harbor Pinellas 70 NA NA 7/1/2016 Parkland Broward 71 26.133451 -81.769558 7/14/2016 Naples Collier 72 26.664269 -81.794759 7/25/2016 Ft. Myers Collier 73 26.204378 -81.793823 7/27/2016 Naples Collier 74 25.797235 -80.187185 7/31/2016 Miami Miami-Dade 75 NA NA 8/9/2016 Naples Collier 76 26.163427 -81.684 8/12/2016 Naples Collier 77 NA NA 8/13/2016 Oldsmar Pinellas 78 NA NA 8/25/2016 Dover Hillsborough 79 NA NA 8/28/2016 Deerfield Beach Broward 80 26.434798 -81.832868 9/19/2016 Estero Lee 81 26.443742 -81.818301 9/26/2016 Estero Lee

Table B-2. Continued. Latitude Longitude Date Location County 82 26.255084 -81.700768 9/27/2016 Naples Collier All citizen science records collected directly through UF extension. Coordinates primarily map-derived based on address. NAs indicate reports without sufficient data for exact coordinates. Species identification was confirmed based on digital images submitted by the citizen scientists.

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BIOGRAPHICAL SKETCH

Audrey Wilson graduated with her bachelor’s degree in biology from the

University of Pennsylvania in 2013. She worked as an intern for the Student

Conservation Association in Saguaro National Park, Tucson, AZ, before beginning her master’s degree. She began her graduate studies at University of Florida in August

2014 and worked with her advisor, Dr. Steve Johnson, to study invasive cane toads in

Florida. Audrey deployed autonomous recording units in natural areas and surrounding disturbed habitat to determine whether or not cane toads have invaded natural areas in the state. She also compiled records from databases and citizen scientists to create a distribution map and identify any range expansion. She graduated with a Master of

Science in wildlife ecology and conservation in December 2016.