Insular Dwarfism in Female Eastern Hog-Nosed Snakes (Dipsadidae; Heterodon Platirhinos) on a Barrier Island

Canadian Journal of Zoology

Insular dwarfism in female Eastern hog-nosed snakes (Dipsadidae; Heterodon platirhinos) on a barrier island

Journal: Canadian Journal of Zoology

Manuscript ID cjz-2019-0137.R1

Manuscript Type: Article

Date Submitted by the 04-Aug-2019 Author:

Complete List of Authors: Vanek, John; Northern Illinois University, Biological Sciences Burke, Russell; Hofstra University, Biology Is your manuscript invited for Draft consideration in a Special Not applicable (regular submission) Issue?:

Colubridae, dwarfism, island biogeography, New York, Heterodon Keyword: platirhinos, Eastern Hog-nosed Snake, Long Island

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Title Insular dwarfism in female Eastern hog-nosed snakes (Dipsadidae; Heterodon platirhinos) on a barrier island

Author Information J.P. Vanek and R.L. Burke

John P. Vanek1 Department of Biology, Hofstra University, Hempstead, NY, USA.

Russell L. Burke [email protected] Department of Biology, Hofstra University,Draft Hempstead, NY, USA.

1 Current address: Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, USA

Corresponding Author: John P. Vanek 631-813-8559 [email protected] Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, 60115, USA

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Abstract

The island rule postulates that the special ecological conditions on islands, such as limited resource availability, can cause populations of large-bodied animals to evolve smaller sizes and small- bodied populations to evolve larger sizes. Although support for the island rule is well documented

(with notable exceptions and debate) in mammals and birds, similar trends are poorly explored in ectothermic vertebrates. As part of a larger study investigating the ecology of Eastern hog-nosed snakes (Heterodon platirhinos Latreille 1801), we compared the mean and maximum sizes of a population from a barrier island (~4,000 ha) to snakes on an adjacent larger island (~363,000 ha) and two mainland sites (450 total snakes across all study sites). We did not observe a difference between the small and large islands but did find differences between the smallest island and the mainland. Female snakes on the barrierDraft island were 8% smaller than those on the mainland, and the largest barrier island female was 35% smaller than the largest documented H. platirhinos. In addition, we found that males did not exhibit dwarfism. We hypothesize the observed dwarfism is a result of limited availability of large prey items and recommend that future studies distinguish between sexes in their analyses.

Keywords

Colubridae, dwarfism, Eastern Hog-nosed Snake, Heterodon platirhinos, island biogeography,

Long Island, New York

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Introduction

Populations of animals living on islands often evolve phenotypic differences relative to mainland

populations, responding to novel resource availability, predation, and competition (Foster 1964;

Van Valen 1973; Lomolino et al. 2006). In mammals, the best studied group in this respect, clear

trends are evident, if reciprocally contradictory: large-bodied species get smaller, and small species

get larger (Lomolino 1985, 2005; but see Meiri et al. 2008, 2011; Lokatis and Jeschke 2018 for

more nuance). For example, pygmy raccoons (Procyon pygmaeus Merriam 1901) are 17.5%

smaller than mainland raccoons (Procyon lotor Linnaeus 1758) (McFadden and Meiri 2013), and

woodrats (Neotoma spp. Say & Ord 1825) on 12 islands around Baja California exhibit gigantism

(Smith 1992). Similarly, in birds, populations of large birds become smaller, and populations of

smaller birds become larger (Clegg and DraftOwens 2002).

However, the evolution of gigantism and dwarfism in reptiles, and snakes in particular, does not

seem to follow the mammalian and avian patterns (Boback 2003; Meiri 2007; Itescu et al. 2014).

In snakes, the direction of change may not be predicted by just mainland body size (Boback and

Guyer 2003), but also by extrinsic factors such as competition, phylogeny, and perhaps most

importantly, food availability (King 1989; Forsman 1991; Boback 2003; Luiselli et al. 2015, but

see Meik et al. 2010). For example, Australian tiger snakes (genus Notechs Peters 1861) rapidly

evolved both dwarfism and gigantism on different islands, corresponding to differences in prey

size availability (Keogh et al. 2005), and Forsman (1991) found that European adders (Vipera

berus Linnaeus 1758) were smaller on islands with smaller prey species. Yet, as data on body

size variation are available for less than 1% of the 3500+ species (reviewed by Boback 2003), it

is premature to discuss overall body size evolution trends and biogeography of snakes,.

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Snakes in general have been poorly researched relative to other vertebrate taxa (Shine and Bonnet

2000; Bonnet et al. 2002), and still less is known about species occurring in non-typical habitats, such as islands (Boback 2003). Snakes can be difficult to study, as they cannot easily be observed from a distance due to their cryptic nature and cannot be monitored/ located acoustically like birds or anurans (Fitch 1987). Snakes are also difficult to trap, and there are few species-specific trapping techniques are available. Marked snakes are rarely recaptured without the aid of radio- telemetry and attempts to model snake population dynamics with both traditional and progressive statistical techniques are generally unsuccessful (Steen 2010).

Comparing multiple snake populations for body size studies is additionally challenging due to issues regarding standardizing measurement techniques and determining which size metrics are most accurate and relevant (Luiselli 2005;Draft Cundall et al. 2016). Snout-vent length is the most commonly used measurement for ecological studies, often chosen over total-length (TTL), because the latter incorporates additional variation due to traumatic tail loss and tail-length sexual dimorphism (Fitch 1987), and SVL is a better predictor of mass (Feldman and Meiri 2013). Mass is less commonly used, as many historic studies of snakes relied on museum specimens, and the preservation process (formalin fixation followed by ethanol storage) dehydrates specimens. Plus, snake mass can also vary widely over brief time periods as a function of hydration levels, reproductive status, and contents of the alimentary tract. For example, some snakes can consume prey that weighs more than their body mass (e.g. Steen et al. 2010).

Another complication for snake size comparisons is their pattern of indeterminate growth, in that size can be conflated with age (Hasegawa and Mori 2008). Halliday and Verrell (1988) reviewed the relationship between age and maximum size of a variety of reptiles and concluded that only

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skeletochronology and mark-recapture methods were reliable in determining age. In addition,

snakes are subject to “silver spoon” effects, in which high food availability early in life can lead

to enhanced growth throughout the lifespan of the animal (Madsen and Shine 2000). Although it

is important to limit body size comparisons to adults only, it can be difficult to distinguish adult

(reproductive) from juvenile (pre-reproductive) snakes.

Fortunately, despite the overall difficulty in studying and comparing most snake populations, some

species at some locations can be easily collected due to unusually high densities and their relatively

conspicuous natures. One such species is the Eastern hog-nosed snake (Dipsadidae; Heterodon

platirhinos Latreille 1801), a stout-bodied, diurnal, oviparous North American species that feeds

nearly exclusively on amphibians, and primarily toads (Bufonidae) (Edgren 1955). Heterodon

platirhinos reaches sexual maturity at 40Draft – 50 cm, with a maximum reported length of 126.8 cm

(Carlile et al. 2011). Eastern hog-nosed snakes are sexually dimorphic, with females generally

reaching larger sizes and having shorter tails than similarly sized males (Ernst and Ernst 2003).

Though typically uncommon (e.g., H. platirhinos represented less than 1% of 33,117 snakes

captured in Kansas) (Fitch 1993), H. platirhinos can nevertheless occur at high densities at specific

locales. For example, the species can reach densities of over 4 snakes/ha on some islands (Scott

1986; J.P. Vanek, pers. observation).

As part of an ongoing research project into the ecology of H. platirhinos on a barrier island, we

noticed a paucity of large adults, despite a robust population and abundant food resources in the

form of Fowler’s Toads (Anaxyrus fowleri Hinckley 1882). These observations corroborated

anecdotal reports that H. platirhinos on the barrier island were small relative to those on the

mainland and an adjacent larger island (K. Barnett and J.A. Feinberg, personal communication,

2012). In addition, Boback and Guyer (2003) suggested that snake species with maximum lengths

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greater than 1.0 m in snout-vent length (SVL) tend to become smaller on islands. Intrigued by these observations, we tested whether the barrier island population exhibited island dwarfism by comparing it to populations of H. platirhinos on a much larger adjacent island and the mainland.

We assessed differences in mean length and used a novel method for testing maximum size differences between snake populations. Unlike nearly all other studies of insular dwarfism in snakes (but see Madsen and Shine 1993; Boback 2006), we analyzed males and females separately, hypothesizing the sexes may be under different selective pressures. We speculate on the drivers of selection leading to the dwarfism, and comment on future research and conservation concerns.

Methods Draft Study Site

Long Island, New York is the largest island in the contiguous United States, located in the coastal lowland ecozone of NY (Edinger et al. 2014). Long Island developed ~21,000 years ago after the most recent glacial period. South of Long Island lies an east-west chain of barrier islands (Fig. 1) formed roughly 9,000 years ago (Rampino and Sanderst 1981). These barrier islands range from

< 1 km to ~10 km away from Long Island and are separated by brackish estuaries typically < 7 m deep (Moskowitz 1976; Edinger et al. 2014; National Oceanic and Atmospheric Administration

2019). Field work for this study primarily took place on a 4000-ha barrier island (Small Island) on the archipelago, ~4 km from the southern shore of Long Island and consisting of mixed woodlands, dunes, and brackish marshes. The specific study site, withheld to prevent the snake population from exploitation, included terrestrial and wetland systems, and was devoid of large forest patches.

The wetlands were a mixture of Brackish Interdunal Swales and Maritime Freshwater Interdunal

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Swales, both dominated by the invasive Common Reed (Phragmites australis (Cav.) Trin. ex

Steud.). Uplands were a mosaic of Maritime Dune, Maritime Heathland, Maritime Grassland, and

Maritime Shrubland, with Maritime Beach adjacent to the ocean. Woody vegetation in these

uplands mostly consisted of small patches of Northern Bayberry (Myrica pensylvanica (Mirb.)

Kartesz). Where small pockets of Successional Maritime Forest occurred, they were dominated by

Japanese Black Pine (Pinus thunburgii Parl.) introduced in the early 1900s.

Comparative Locations

We obtained raw sex, length and mass data from three unpublished studies of wild H. platirhinos The first site was 65 km to the NE of SmallDraft Island, at Brookhaven National Laboratory, on Long Island (hereafter “Large Island”) (40° 52' N, 72° 52' W). Long Island is separated from the

mainland by the Long Island Sound to the North and brackish estuaries of the Hudson River to the

west (Fig. 1). Strait depths are < 30 m (National Oceanic and Atmospheric Administration 2019).

This area was ~2,100 ha of pine-oak woodlands, dominated by Pitch Pine (P. rigida P. Mill.) with

scattered ephemeral pools and wetlands, and is part of a larger pine-oak ecosystem. Snakes at

Large Island were incidentally captured, but not trapped, over a 5-year period (J.A. Feinberg,

personal communication, 2012).

The northernmost mainland site (hereafter “Mainland 1”) was 250 km NE of Long Island, at Cape

Cod National Seashore, in Massachusetts (42° 04' N, 70° 12' W) (Fig. 1). Cape Cod National

Seashore consists of ~17,600 hectares in northeastern Cape Cod, an 880,000-ha glacial outwash

barrier spit, created ~18,000 years ago (Geologic History of Cape Cod, Massachusetts 1976). The

spit was dominated by oak-pine woodlands, but also contained heathlands and dunes like those

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that occur on the Small Island. Snakes at Mainland 1 were trapped and incidentally captured over an 11-year period (R.P. Cook, personal communication, 2014).

The southernmost mainland site (hereafter “Mainland 2”) was 1,000 km to the south of Large

Island at the Savanah River National Laboratory in South Carolina (33° 20' N, 81° 43' W) (Fig. 1).

The Savanah River National Laboratory is an 80,000-ha area in the unglaciated coastal plain and included a wide variety of upland habitats with interspersed wetlands, dominated by Loblolly Pine

(P. taeda L.) and Slash Pine (P. ellioti Engelm.). Snakes at Mainland 2 were trapped and incidentally captured over a 42-year period (T.D. Tuberville, personal communication, 2014).

Data Collection Draft

We measured snakes from Small Island after locating them via visual encounter surveys (2013-

2015), trapping them in box traps (2014-2015), or if encountered while radio-tracking previously encountered individuals (2013-2015). Box traps were modified from Burgdorf et al. (2005), and used funnels made of either wire mesh or trimmed plastic bottles. Snakes were also radio-tracked

(implanted with 5-g radio transmitters (model SB-5, Holohil®) following Reinert and Cundall

(1982) to help locate additional new individuals. Telemetry was invaluable for finding new snakes because: (1) a better understanding of natural history and spatial ecology (activity periods, microhabitat use, home range etc.) obtained via telemetry allowed us to locate new snakes with greater success, and (2) by creating “Judas” snakes, in which radio-tracked females led us to new males during the breeding season (e.g. Taylor and Katahira 1988; Smith et al. 2016).

We uniquely marked each adult snake by scale-clipping 3-6 ventral scales following a technique modified from Brown and Parker (1976). We also took photographs of the dorsal surface of each

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snake’s head and used the unique markings on the parietal, frontal, and supraocular scales as a

supplement to the identifying scale clips (Fig. 2). Similar unique pattern identification has been

used successfully in the Indian python (Python molurus Linnaeus 1758) (Bhupathy 1990); there

was no indication that individual patterns changed over the course of this study (J.P. Vanek,

personal observation).

For each collected snake, we measured mass to the nearest gram using a digital scale. Snout-vent

length (SVL), total length (TTL), and tail length (TL) were measured to the nearest cm using the

image processing software ImageJ (Schneider et al. 2012). We found this method to be comparable

to more traditional measuring techniques based on comparative measurements of 46 preserved H.

platirhinos (J.V. unpublished data). Transmitters were surgically removed at the end of the study

when we could locate them before transmitterDraft batteries died or when we incidentally encountered

snakes with previously dead batteries. All snakes were treated humanely following the Guidelines

for use of Live Animals and Reptiles in Field and Laboratory Research (2nd Edition, American

Society of Ichthyologists and Herpetologists, 2004) and all procedures were pre-approved by

Hofstra University’s Institutional Animal Care and Use Committee.

We supplemented our data by measuring the SVL, TL, and TTL of museum specimens previously

collected on the Small Island (n = 5; AMNH 113074, AMNH 58282, AMNH 133078, AMNH

133073, AMNH 65382) and from the Large Island (n = 4; AMNH 3628, AMNH 128191, AMNH

4153, AMNH 38185). These 9 specimens (of 47 examined) were included because they had

interpretable locality information and were ostensibly sexually mature.

Data Analysis

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We used R version 3.4 (R Foundation for Statistical Computing, Vienna Austria) to conduct all statistical analyses.

We used single-factor ANOVA to test for differences in mean and maximum SVL between each population. We used the measurements of the five largest snakes of each sex and population for maximum size comparisons, a novel method intended to reduce the impact of outliers. We tested for departures from normalcy and homogeneity using the Shapiro-Wilks and Levene’s test, respectfully and subsequently all data were log transformed before analysis. ANOVAs indicating significant differences were followed by Tukey-Kramer post-hoc tests for unequal sample sizes (McDonald 2014). Draft Only sexually mature snakes (males ≥ 40 SVL, females ≥ 45 SVL; Ernst and Ernst 2003) were included in the analyses and each sex was analyzed separately due to differing size at maturity.

The ratios of TL: TTL and/or TL: SVL were used to assign sex or SVL to snakes with ambiguous, erroneous, or missing data. Ratios of SVL: TL were based on ratios of snakes known to be correctly sexed via probing or subcaudal scale counts and conformed closely to ratios reported in Scott

(1986).

Results

We obtained morphometric data from 791 unique snakes, 450 of which were classified as adults and used for subsequent analysis. Most records came from Mainland 2 (259 adults over 42 years), followed by Small Island (87 adults over 3 years + 5 museum specimens), Mainland 1 (68 adults

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over 11 years), and Large Island (27 adults over 5 years + 4 museum specimens). Means, standard

errors, and sample sizes for each analysis are presented in Table 1.

2 The mean SVLs of females varied significantly by location (F3,183 = 3.7, p = 0.013, ω = 0.041).

Small Island females averaged 8% shorter than females from both the Mainland 1 site (p = 0.023)

and Mainland 2 site (p = 0.012) but did not differ significantly from females on the Large Island

(Figure 3, Table 1). Females on the Large Island did not differ significantly from females on either

Mainland site (Fig. 3). The mean SVLs of males did not vary by location (F3,259 = 2.3, p = 0.076,

ω2 = 0.015).

Similarly, the mean SVL of the five longest females from each population varied significantly by

2 location (F3,16 = 11.0, p = 0.00036, ω =Draft 0.6). The five longest females on the Small Island were 9% shorter than the five longest females from Mainland 1 (p < 0.01) and 12% shorter than those

on Mainland 2 (p < 0.001) (Figure 4, Table 1). In addition, the five longest females on the Large

Island were 9% shorter than the five longest females at Mainland 2 (p < 0.01) (Fig. 4). The mean

SVL of the five longest males from each population did not vary by location (F3,16 = 1.5, p = 0.25,

ω2 = 0.069).

To test if the difference in maximum size of females was an artifact of unequal sample sizes, we

used a resampling approach to compare the SVL of five longest females from the Small Island to

a combined sample of both mainland populations. To do so, we took a random sample without

replacement of 36 female snakes (the sample size of females from the Small Island) from the

combined mainland population (n = 187) and compared the mean of the five longest females from

this sample to the five longest females from the Small Island. We repeated this process for 10,000

iterations and found that the longest females on the Small Island females averaged 5.4 ± 1.9 cm

SVL shorter than longest female mainland snakes (Supplementary Materials).

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Discussion

We found compelling evidence of dwarfism in female H. platirhinos from the Small Island, but not on the Large Island. Small Island females (the larger of the sexes) both averaged and reached smaller maximum lengths than Mainland females. These differences were lacking in males mirroring instances of female only dwarfism in Boa constrictor (Boback 2006) and Natrix natrix

(Madsen and Shine 1993), even though Vanek (2016) found that males on the Small Island mature at small sizes. In addition, the absolute maximum SVL of the largest Small Island snake (71.3 cm) was 35% smaller than the largest documented H. platirhinos (Carlile et al. 2011). However, we did not find strong evidence of dwarfismDraft in snakes from the Large Island, and like (Boback 2003), we were unable to find a link between island size and the extent of island effects. Females on the

Large Island averaged both no larger than the Small Island females and no shorter than Mainland females; it is possible that a larger sample size would have revealed size differences. Based on these results, we recommend that studies of insular dwarfism in snakes analyze males and females separately.

Why are female snakes on the Small Island dwarfs? We hypothesize that Small Island females are under directional selection for small body size due to adaptation to their only available food source,

A. fowleri. Though preferentially preying on Bufonids, H. platirhinos is an amphibian generalist, consuming a wide variety of amphibian species (Edgren 1955; reviewed by Ernst and Ernst 2003).

Eastern hog-nosed snakes on the Large Island had access to a wide variety of suitable prey species, including not only A. fowleri but Eastern spadefoot toads (Scaphiopus holbrookii Harlan 1835),

American bullfrogs (Lithobates catesbeianus Shaw 1802), green frogs (L. clamitans Latreille

1801), spotted salamanders (Ambystoma maculatum Shaw 1802), and Eastern tiger salamanders

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(A. tigrinum Green 1825), all of which reach larger sizes than A. fowleri (Gibbs et al. 2007).

Similarly, mainland H. platirhinos have access to most of the species present on the Large Island

plus other large toad species such as American Toads (A. americanus Holbrook 1836) at Mainland

1 and Southern toads (A. terrestris Bonnaterre 1789) at Mainland 2.

Other snake species have been shown to express dwarfism in response to lower prey species

diversity and smaller body size of available prey. For example, European grass snakes (N. natrix

Linnaeus 1758) were smaller on islands with a reduced number of potential prey species compared

to the nearby mainland (Madsen and Shine 1993), and European adders were smaller on islands

with smaller field voles (Microtus agrestis Linnaeus 1761) (Forsman 1991). However, to the best

of our knowledge this is the first study that formally assessed insular dwarfism in snakes of the

family Dipsadidae (reviewed by BobackDraft 2003). While dwarfism has been suggested for the Puerto

Rican racer (Borikenophis [Alsophis] portoricensis Reinhardt and Lütken 1863) (Schwartz 1966)

and the musssurana (Clelia Clelia Daudin 1803) (Schwartz and Henderson 1991), no statistical

analysis has been put forward to confirm these observations.

The interface between genetics and the environment in snakes has been shown to be complex, and

some life history characteristics, such as growth rate and clutch size, may be influenced by genetics

and diet in complicated ways, depending on species. For example, Plummer (1983) found that

clutch size was not influenced by food availability in rough greensnakes (Opheodrys aestivus

Linnaeus 1766), but Seigel and Ford (1991) found that high food availability increased clutch size

in red cornsnakes (Pantherophis guttatus Linnaeus 1766). Tanaka (2011) combined long-term

mark-recapture data and experimental feeding in Japanese four-lined snakes (Elaphe

quadrivirgata Boie 1826) to show insular dwarfism was a response to island prey limitation, and

not a function of shorter lifespan (e.g. via increased predation or food scarcity). In addition, local

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adaptation to specific habitats is known from island snakes less than five km from the mainland

(King 1993; King and Lawson 1997) and populations of mainland snakes less than 20 km from

each other (Gangloff et al. 2017), so it is not unreasonable that Small Island H. platirhinos have

evolved to the specific conditions of the island.

Snakes are gape-limited predators and predators with large gapes can consume prey of a wider

variety of sizes (King 2002). Gape size is highly plastic and can be experimentally induced simply

by feeding snakes larger prey items (Aubret and Shine 2010). It is also capable of evolving rapidly,

as is body size. For example, in just 20 generations, two species of Australian snakes evolved

larger head sizes in response to the large invasive Cane Toad (Rhinella marina Linnaeus 1758)

(Phillips and Shine 2004). Where H. platirhinos is sympatric with L. catesbianus, L. clamitans, A. americanus, and other large amphibians,Draft snakes with small gapes would be unable to eat these larger prey species. However, on the Small Island, with only the small A. fowleri available as prey

(J.V. unpublished data), there is no selective pressure for a larger body size based on prey availability and a larger body size implies a greater metabolic cost. As active foragers, larger- bodied H. platirhinos would need to spend more time foraging than smaller individuals, which would be able to meet their needs catching fewer toads. For example, in comparison to smaller

Eastern garter snakes (Thamnophis sirtalis Linnaeus 1758), larger T. sirtalis had a higher ratio of field metabolic rate to standard metabolic rate and Peterson et al. (1998) concluded that larger T. sirtalis had to use more energy than smaller individuals.

Like the Small Island, Assateague Island, a barrier island off the coast of Virginia, USA, has a dense population of H. platirhinos, but unlike the Small Island, the snakes are not dwarfed (Scott

1986; R.A. Cook, personal communication 2014). We suggest this is because they prey on not only A. fowleri, but also the larger Southern leopard frog (L. sphenocephalus Cope 1889), L.

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catesbianus, and L. clamitans, all known from the island (Conant et al. 1990). As with many other

taxa (Case 1978), dwarfism in the Small Island H. platirhinos may not be a response to islands

directly, but of reduced prey diversity and prey size. This phenotypic plasticity, however, can lead

to rapid shifts in body size, which over time can lead to selection for smaller body sizes or growth

rates (Aubret and Shine 2007). Finally, it is unlikely that the observed dwarfism in the Small Island

H. platirhinos was a function of poor growth rates related to limited food resources overall,

because toads of all life stages were extremely common (J.P. Vanek, personal observation). In

addition, we observed high rates of H. platirhinos reproduction and we observed no snakes in poor

body condition (J.P. Vanek, personal observation).

In conclusion, we found evidence of dwarfism in female H. platirhinos inhabiting a relatively

small barrier island with limited prey Draftdiversity. To the best of our knowledge, this is the first

evidence of insular dwarfism in a Diapsid snake. This insular population of H. platirhinos provides

an excellent system to study the evolution and interaction between life history characteristics,

heredity, and environmental pressures. Future work should investigate the degree of genetic

isolation of the Small Island population, as well as growth rates, maternal effects, and the

inheritance of maximum body size in H. platirhinos. Care should be taken to conserve this unique

population and protect it from collection, exploitation, development, and climate change.

Acknowledgements

The authors would like to thank R.A. Cook and T.D. Tuberville for providing long-term data, as

well as the veterinarians (especially P.P. Calle) and staff at the Wildlife Conservation Society’s

Wildlife Health Program. Conversations with K. Barnett and J.A. Feinberg were instrumental in

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initializing and developing this project. C.N. Wails provided helpful advice and code examples for the randomizations. Finally, J.P. Vanek would like to thank the members of his thesis committee for helpful comments on the manuscript: P. Andreadis, D. Wasko, and R. Sarno. Funding for this study was provided by the Department of Biology at Hofstra University, a grant from the Theodore

Roosevelt Memorial Fund to J.P. Vanek, a Donald Axinn Fellowship in Ecology and Conservation to J.P. Vanek, a Graduate Student Research in Herpetology grant from the Chicago Herpetological

Society to J.P. Vanek, and from a crowdfunding campaign at Experiment.com run by J.P. Vanek.

Data were collected with appropriate permits from the NYS OPRHP (#13-0338) and NYS DEC

(#1908). Draft

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Table 1. Sample sizes and mean snout-vent lengths (SVL) in cm of all adult Eastern hog-nosed snakes (Heterodon platirhinos Latreille 1801) and of the five largest snakes by sex from each site included in our analyses. Site n (female, male) Female SVL Female SVL Male SVL Male SVL Mean Top 5 Mean Top 5 Small 36, 56 55.6 (± 1.2) 67.8 (± 0.9) 48.1 (± 0.8) 62.2 (1.2) Island Large 19, 12 58.9 (± 1.8) 69.8 (± 1.7) 51.6 (± 1.9) 53.5 (2.7) Island Mainland 1 43, 25 60.7 (± 1.3) 74.5 (± 1.1) 50.4 (± 1.1) 59.2 (2.0) Mainland 2 89, 170 60.4 (± 0.9) 76.8 (± 1.0) 49.3 (± 0.4) 61.4 (0.9)

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Figure Legend

Figure 1. Map of Long Island, New York, USA and locations of comparative study populations (inset). The main study site (exact location withheld to prevent the snake population from exploitation) is located on the chain of barrier island on the southern shore of Long Island.

Figure 2. Unique head pattern differences between three marked Eastern hog-nosed snakes (Heterodon platirhinos Latreille 1801) as evident by melanin deposits on the parietal, frontal, and supraocular scales.

Figure 3. Tukey style boxplots depicting the snout-vent lengths (SVL) of sexually mature (>= 45 cm SVL) female Eastern hog-nosed snakes (Heterodon platirhinos Latreille 1801) at each site. There was a significant effect of site on mean SVL (dashed line) by one-way ANOVA (p < 0.05). Sites grouped by horizontal lines below site name are not significantly different from each other (Tukey-Kramer, p > 0.05). Analysis was conducted on log-transformed data. Thick black lines represent the median SVL, and whiskersDraft represent observations no greater or lower than 1.5 times the interquartile range (top and bottom edges of boxes).

Figure 4. Mean snout-vent lengths (SVL) of the five largest Eastern hog-nosed snakes (Heterodon platirhinos Latreille 1801) at each study site. There was a significant effect of site on mean by one-way ANOVA (p < 0.05).

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Figure 1. Map of Long Island, New York, USA and locations of comparative study populations (stars). The main study site (exact location withheld to prevent the snake population from exploitation) is located on the chain of barrier island on the southern shore of Long Island. Spatial data provided by the NYS Office of Information Technology Services GIS Program Office (GPO), NYS Department of Environmental Conservation, United States Census Bureau, United States Geological Survey, and Natural Resources Canada.

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Figure 3. Tukey style boxplots depicting the snout-vent lengths (SVL) of sexually mature (>= 45 cm SVL) female Eastern hog-nosed snakes (Heterodon platirhinos Latreille 1801) at each site. There was a significant effect of site on mean SVL (dashed line) by one-way ANOVA (p < 0.05). Sites grouped by horizontal lines below site name are not significantly different from each other (Tukey-Kramer, p > 0.05). Analysis was conducted on log-transformed data. Thick black lines represent the median SVL, and whiskers represent observations no greater or lower than 1.5 times the interquartile range (top and bottom edges of boxes).

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Figure 4. Snout-vent lengths (SVL) of the five largest female (grey circle) and male (white square) ± 1 SD. Eastern hog-nosed snakes (Heterodon platirhinos Latreille 1801) at each study site. There was a significant effect of site on max SVL by one-way ANOVA (p < 0.05) for females, but not males. Sites grouped by horizontal lines below site name were not significantly different from each other (female data only) (Tukey-Kramer, p > 0.05). Analysis was conducted on log-transformed data.

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