A COMPARISON OF THE ARBOREAL BEHAVIOR OF OLD WORLD
(COELOGNATHUS), NEW WORLD (PANTHEROPHIS &
SCOTOPHIS), AND HYBRID (PANTHEROPHIS +
SCOTOPHIS, PITUOPHIS + SCOTOPHIS)
COLUBRID SNAKES
A Thesis
by
JERROD G. TYNES
Submitted to the Office of Graduate Studies of Texas A&M University- Commerce in partial fulfillment of the requirements for the Degree of MASTERS OF SCIENCE May 2014
A COMPARISON OF THE ARBOREAL BEHAVIOR OF OLD WORLD
(COELOGNATHUS), NEW WORLD (PANTHEROPHIS &
SCOTOPHIS), AND HYBRID (PANTHEROPHIS +
SCOTOPHIS, PITUOPHIS + SCOTOPHIS)
COLUBRID SNAKES
A Thesis
by
JERROD G. TYNES
Approved by:
Advisor: Lani Lyman-Henley
Committee: John P. Slovak Jackie Wahrmund
Head of Department: Larry F. Lemanski
Dean of the College: Dan Edelman
Dean of Graduate Studies: Arlene Horne
iii
Copyright © 2014
Jerrod G. Tynes
iv
ABSTRACT
A COMPARISON OF THE ARBOREAL BEHAVIOR OF OLD WORLD (COELOGNATHUS), NEW WORLD (PANTHEROPHIS & SCOTOPHIS), AND HYBRID (PANTHEROPHIS + SCOTOPHIS, PITUOPHIS + SCOTOPHIS) COLUBRID SNAKES
Jerrod G. Tynes, MS Texas A&M University-Commerce, 2014
Advisor: Lani Lyman-Henley, PhD
A total of 24 Colubrid snakes were observed for their arboreal behavior and hide box selection. These snakes had been allocated into six different testing groups, group 1 consisting of four yearling corn snake/rat snake hybrids (Pantherophis + Scotophis), group 2 consisting of four pine snake/rat snake hybrids (Pituophis + Scotophis), group 3 consisting of four second generation intergrade rat snakes (50% Scotophis obsolete, 37.5% S. alleghaniensis, 12.5% S. spiloides), group 4 consisting of four yearling Okeetee corn snakes (Pantherophis guttatus), group 5 consisting of four Texas rat snakes (Scotophis obsoleta), and group 6 consisting of four trinket snakes (Coelognathus helena helena). All snakes were captive born and all groups except group 5 consisted of siblings. All of these snakes were fed a consistent diet of lab mice on a weekly or biweekly basis. Snake groups were placed in testing tanks with two identical hide box options in different elevations within the tank, as similarly described by Tynes and Lyman-
Henley, 2011. Paper towels were used as the cage substrate and a water dish was provided.
Animal feeding was synchronized and one round of data collection occurred for each group.
Each round consisted of 5 days of data collection with tanks being checked five times daily. The arboreal behaviors and hide box selections were documented and differences between groups and sexes were analyzed. Chi-square results show arboreal preference for groups 1,2,3,6, a terrestrial
v preference for group 4 and no distinct preference for group 5 [X2 (df = 1, n = 4) = 0.640, p ≤
0.05]. One way ANOVA and Tukey HSD tests indicate that group 1 and group 2 had a significantly higher selection of the arboreal locations than group 4 at the 0.05 level of significance. Females of groups 1, 2, 3, and 4 were more arboreal than the males within their respective groups, while males in groups 5 and 6 were more arboreal than their female counterparts.
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ACKNOWLEDGEMENTS
Thank you to everyone who helped to make this happen, including Dr. Neil Ford, Gerry
Salmon and others for several of the study subjects. Thanks to Dr. Lani Lyman-Henley who has been a great advisor and mentor. Thank you to my committee members Dr. John P. Slovak and
Dr. Jackie Wahrmund. Thank you to Dr. Izhar Khan for allowing me to do the study in his lab. I would also like to thank my department head Dr. Larry F. Lemanski and our dean Dr. Dan
Edelman. Special thanks to my amazing wife Ashleigh Tynes, and to all my family and friends.
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TABLE OF CONTENTS
LIST OF TABLES……………………………………………………………………………...viii
LIST OF FIGURES ……………………………………………………………………………...ix
CHAPTER
1. INTRODUCTION ...... 1
Taxonomy & Terminology ………………………………………………………… .....1
Corn Snakes ...... 2
North American Rat Snakes…………………………………………………………….3
Pine Snakes ………………………………………………………………………….…5
Asian Rat Snakes ...... 7
Hybrids & Intergrades...... 7
Previous Work………………………………………………………………………...10
My Study………………………………………………………………………………10
Hypothesis...... 11
2. METHODS ...... 12
Subjects ...... 12
Materials and Procedures ……………………………………………………………..16
3. RESULTS ...... 18
Data Analysis …………………………………………………………………………25
4. DISCUSSION……………………………………………………………………………27
REFERENCES…………………………………………………………………………………..32
VITA……………………………………………………………………………………………..36
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LIST OF TABLES
TABLES
1. Results of the Corn snake/ rat snake hybrids (Pantherophis + Scotophis) and the
locations that the snakes were found in during the study.…………………………...18
2. Results of the pine snake/rat snake hybrids (Pituophis + Scotophis) and the locations
that the snakes were found in during the study………………………………………19
3. Results of the intergrade rat snakes (50% Scotophis obsoleta, 33.33% S.
alleghaniensis, 16.67% S. spiloides) and the locations that the snakes were found in
during the study………………………………………………………………………20
4. Results of the Okeetee corn snakes (Pantherophis guttatus) and the locations that the
snakes were found in during the study……………………………………………….21
5. Results of the Western rat snakes (Scotophis obsoletus) and the locations that the
snakes were found in during the study………….……………………………………22
6. Results of the trinket snakes (Coelognathus helena helena) and the locations that the
snakes were found in during the study…………………………………………….…23
7. Results of all groups and the locations that the groups were found in during the
study……….…………………………………………………………………………24
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LIST OF FIGURES
FIGURE
1. Distribution map and intergrade zones of rat snakes (Scotophis spp.) broken up by
native color phases……… ……………………………………………………………9
2. Individuals from the six testing groups…………………....……………...……….. ..15
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CHAPTER 1
INTRODUCTION
There are approximately 3,000 species of snakes worldwide and the Colubrids make up
1,600 of those species (Behler, 2000). Some snakes within this group are more closely related than others with some possibly even being moved out of the family Colubridae. Some snakes such as those within the Lampropeltini tribe do not adhere to the strict biological species concept as many can produce viable offspring when crossing the species and even genus lines. In the summers of 2012 and 2013 the Texas A&M University-Commerce Animal Care Facility successfully produced snakes from parents of two different genera. As the taxonomy of this entire tribe of snakes is still under debate, research on these animals can be enlightening and can add to the paucity of literature on hybrid snakes.
Taxonomy & Terminology
For the past several decades there has been controversy regarding the taxonomic relationships of corn snakes, rat snakes, fox snakes, and pine snakes. Recently, Burbrink and
Pyron (2010) established that the genus of Pantherophis (formerly Elaphe) describes all of the
North American corn snakes, rat snakes and fox snakes. The Center of North American
Herpetology (CNAH), however, recognizes the breakup of this large genus into three distinct genera Pantherophis, Scotophis, and Mintonius, respectively (Collins & Taggart, 2008), on the stance that it provides more information regarding the evolutionary background of the members of the group. The CNAH currently stands as a decisive database which uses up to date publications to describe the scientifically accepted taxonomy of North American herpetofauna.
This paper will use all scientific names that align with the current recognition of CNAH.
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Since there is also little clarity of the definition of intergrades and hybrids among snakes, for the purpose of this paper the term intergrade will refer to individuals that have parents of different species but within the same genus. The word hybrid will refer to individuals from parents of two different genera.
Corn Snakes
The genus Pantherophis includes three species: the Great Plains rat snake (Pantherophis emoryi), the Slowinski’s corn snake (Pantherophis slowinskii), and the Eastern corn snake
(Pantherophis guttatus) (Collins & Taggart, 2008). These snakes are found throughout the southern United States and are variable in color from red, orange, yellow, gray and brown
(Behler, 2000). Corn snakes have 27-29 rows of smooth scales running along their bodies, with two prefrontal scales and a divided anal scale (Conant, 1975). These medium sized snakes range from 61-182.9 cm in length and can be found in a large variety of habitats, feeding on a variety of prey items including rodents, frogs, lizards, birds, and bats (Behler, 2000). The Eastern corn snake (P. guttatus) is a popular pet snake due to its easy care and temperament. Since the 1960s this snake has been a major animal in the pet industry and has been reported to be the most popular snake in the world (Love, 2013). As with any pet, especially one that lives for a long period of time, released and escaped animals can be found in the wild.
When examining corn snake feeding patterns, movement and proximity of prey are strong cues for foraging success in this predator. There is little difference in selection regarding prey color and substrate color, a commonality often seen in terrestrial predators. Avian predators on the other hand, often utilize color conspicuousness to hunt (Smith & Watson, 1972). The terrestrial nature of corn snakes allows for them to be ideal study subjects for specific fields such
3 as road ecology, as they have low road avoidance for southeastern snake species. Corn snakes do not avoid roads, a behavior commonly seen in terrestrial animals which move large distances for food or breeding (Andrew & Gibbins, 2005).
While rodents are the primary prey for this group of snakes, birds have been taken in their arboreal nests. For example, Great Plains rat snakes (P. emoryi) have been documented feeding on adult Golden-cheeked warblers (Dendroica chrysoparia). Nocturnal foraging behavior and the ability to climb allows for the success of adult bird predation on occasion
(Stake, 2001).
North American Rat Snakes
North American rat snakes or Woodland rat snakes (Scotophis) are strong constrictors that can reach lengths of anywhere between 86.4 cm – 256.5 cm. There are four species of
Woodland rat snakes found throughout North America: the Baird’s rat snake (Scotophis bairdi), the Western or Texas rat snake (Scotophis obsoletus), the Midland or gray rat snake (Scotophis spiloides), and the Eastern rat snake often referred to as the Black rat snake, Yellow rat snake or
Everglades rat snake based on the color patterns of the individual which is differentiated by latitudes (Scotophis alleghaniensis) (Collins & Taggart, 2008).
The term Black rat snake can be somewhat confusing as each species has darker forms found in the north of its respected region, possibly as an evolutionary thermoregulatory adaptation to cooler environments (Burbrink, Lawson, & Slowinski, 2000). These snakes are found all over the United States from as west as Texas and as north and east as New York and
Vermont, depending on species. All rat snakes have 25-33 rows of weakly keeled scales running along their bodies, two prefrontal scales, and a divided anal scale. In spring and fall these snakes
4 are active during the day and during the summer they become nocturnal. In captivity these snakes may live longer than 20 years. Rat snakes are known to feed on a variety of animals, most notably the rodents for which they are named. In addition to mice, rats and squirrels, rat snakes will often eat birds, nestlings, bird eggs, frogs, and lizards (Behler, 2000). All rat snake species (Scotophis) are known to be fantastic climbers, often ascending trees to forage for food
(Dunn, 2001).
In Missouri and Texas rat snakes (Scotophis obsoletus) have been found to regularly prey upon nestling birds and eggs. The activity of the birds coming to and from the nest appears to aid in the success of the snakes. After fledging some of the snakes occasionally returned to the now-empty nests at which they had prior hunting success (Stake, Thompson III, Faaborg, &
Burhans, 2005). The hunting success of rat snakes may have major implications in migratory bird management. The use of different tree types by birds as nesting sites can greatly affect the predation success of rat snakes (Mullin & Cooper, 2002). In a study conducted at Stephen F.
Austin State University seven Texas rat snakes (S. obsoletus) were studied to determine what kind of arboreal structures they preferred. The peak of the snakes’ arboreal selection was after the peak breeding and nesting season of arboreal birds, which may suggest that there is more than predation that affects Texas rat snake arboreal behavior (Pierce, Fleet, McBrayer, &
Rudolph, 2008).
In Florida the Yellow rat snake (Scotophis alleghaniensis) has been recorded feeding on the Cuban tree frog (Osteopilus septentrionalis) in an arboreal setting. It is observed that buildings and hammocks are the most likely place to find the Cuban treefrog and that the yellow rat snake was commonly seen around buildings and also uses hammocks. A 62.0 cm Yellow rat snake was seen feeding on a 44 mm tree frog on the top of a building in the Everglades
5
(Meshaka Jr. & Ferster, 1995). Yellow rat snakes near Lake Okeechobee and the surrounding
Everglades have been commonly found in the rafters of abandoned buildings and barns (Parker,
2012). In a study in Maryland, female Black rat snakes (S. allegheniensis) moved less than males and were found to be in arboreal shelters like trees and buildings more often. Elevated sites were recorded to be used more often (>50%) and females preferred to be higher up than males (Durner & Gates, 1993).
Pine Snakes
Pine and Gopher snakes, genus Pituophis, are a closely related group of snakes found within the Lampropeltini tribe along with the Pantherophis and Scotophis (Burbrink & Pyron,
2010). There is one species of gopher snake (Pituophis catenifer) and two species of pine snake, the Eastern Pine snake (Pituophis melanoleucus) and the Louisiana Pine Snake (Pituophis ruthveni). In North America there are six subspecies of gopher snakes; the Sonoran gopher snake (P. c. affinis), the San Diego gopher snake (P. c. annectens), the Pacific gopher snake (P. c. catenifer), the Great Basin gopher snake (P. c. deserticola), the Santa Cruz gopher snake (P. c. pumilis), and the Bullsnake (P. c. sayi). The Eastern Pine snake has three subspecies: the
Black Pine snake (P. m. lodingi), the Northern Pine snake (P. m. melanoleucus), and the Florida
Pine snake (P. m. mugitus) (Collin & Taggart, 2008).
Several Pituophis species and subspecies are documented under the U.S. Endangered
Species Act (U.S. ESA) and the Committee on the Status of Endangered Wildlife in Canada
(COSEWIC). P. c. catenifer is documented to be extirpated (COSEWIC) from British
Columbia, P. c. deserticola is documented to be threatened (COSEWIC) in British Columbia, P.
6 m. lodingi is documented as a candidate (U.S. ESA), and P. m. mugitus is documented as a candidate (U.S. ESA) (NatureServe, 2014).
Pine snakes feed primarily on small mammals but on occasion will eat birds, bird eggs, and lizards. These diurnal snakes are considered useful in controlling rodent populations within their range. The Northern Pine snake (P. m. melanoleucus) ranges between 122-168 cm and is covered in keeled scales. This species, as well as other pine snakes, has four prefrontal scales which distinguishes it amongst other Colubrids. Northern Pines are very secretive and their burrowing habits decrease their contact with people. The Northern Pine snake has a range from
New Jersey south to South Carolina where it intergrades with the Florida Pine snake (P. m. mugitus) (Conant, 1975).
In the wild, these snakes are typically found under rocks or logs and will often use tortoise and mammal burrows as shelter (Behler, 2000). Northern Pine snakes (P. m. melanoleucus) will commonly nest in areas of less than 10% tree cover. These snakes will excavate nests and lay their eggs in the soft sand of open clearings (Burger & Zappalorti, 1986).
Northern pine snakes can lay between four and 16 eggs and the burrows which they construct for their eggs can vary in size and humidity (Burger & Zappalorti, 1991). Most of the multi- seasonal pine snake hibernacula is dug by the snakes themselves and these dens have several (up to eight) side chambers in which different snakes will individually overwinter (Burger et al.,
1988). The habitat use of pine snakes is correlated with the density of their small mammal prey.
These snakes have large home ranges and cross roads often. More data should be collected on pine snakes as they are an understudied taxon (Baxley & Qualls, 2009).
7
Asian Rat Snakes
Trinket snakes (Coelognathus helenus) were previously considered close relatives of the
North American rat snakes as they both shared the genus name Elaphe (Schatti & Wilson, 1986).
These snakes have since been separated into the genus Coelognathus as the polyphyletic differences between Old World and New World rat snakes were clarified using morphological and molecular data (Utiger et al., 2005). There are two subspecies of trinket snakes: the Indian
Trinket snake, Coelognathus helena helena and the Montane Trinket snake, Coelognathus helena monticollaris (Knight, 2010). They are found throughout India, Sri Lanka, Nepal, and
Bangladesh. This diurnal species reaches sexual maturity in 2 years and can live to be 15 in captivity (Robert et al., 2007). In the wild these snakes are often seen in shrubs and trees in the wild and are considered to be arboreal (Walmiki et al., 2012). There is little literature on Asian rat snakes species and any additional data on these snakes can increase our understanding of this species and fill much needed gaps in the literature over these snakes.
Hybrids and Intergrades
There is little data on hybrid and intergrade snakes in the literature. Even the data on wild snakes of all of the species used in this study are sparse, especially for trinket snakes, and published by one or two individuals. Any data collected will increase understanding of how snakes are related and will showcase how innate behavior is affected by genetic influences from other species.
As seen in Figure 1, intergrade rat snakes have been recorded where species borders overlap (Dunn, 2001). Hybrid rat snakes have been discovered in the wild where species zones overlap (Vandewege et al., 2012). Hybrids can occur in the lab with little to no human assistance
8 as was observed with both the corn/rat and pine/rat hybrid study subjects. There is no reason to believe this can’t occur as readily in the wild with these species. The potential of escaped pet snakes breeding with native species not only affects the genetics of the endemic species but all other native species (such as birds), as new genetics bring new adaptations and behaviors.
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Figure 1: Distribution map and intergrade zones of rat snakes (Scotophis spp.) broken up by native color phases; Grey: Midland rat snake (Scotophis sploides), Green: Hybrid rat snake (Scotophis spp.), Black: Eastern rat snake (Scotophis alleghaniensis), Yellow: Eastern rat snake (Scotophis alleghaniensis)
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Previous Work
In 2011, Dr. Lani Lyman-Henley and I studied 24 captive bred rat snakes (Scotophis) of varied intergrades in order to determine their affinity for elevated hide boxes. Data were collected on which hide boxes the individuals preferred with differences being noted between sexes, intergrade crosses, and with regards to room temperature. The rat snakes were found most often (52.08%) in the top hide boxes and males were found in the top boxes more than the females. There was a difference between the different rat snake intergrades with the yellow and
Texas intergrades being found in the top box the most and the grey and Texas rat snake intergrades found in the top box the least (Tynes, 2011).
This study had a narrow focus on rat snakes and their intergrades. The scope of this study will be expanded upon to encompass more species and hybrids as a means to analyze the relationships between taxonomy and behavior as it pertains to hide box selection and climbing.
My Study
The literature discussed here indicates that wild and captive Old World and New World rat snakes can be found in elevated hiding places, pine snakes prefer underground burrows, and corn snakes utilize both. The purpose of this study was to determine the arboreal behavioral differences between hybrid snakes compared to that of pure breed snakes by comparing the snakes’ affinity for elevated hide boxes. I focused on the snakes’ hide box of choice, any differences in accordance to time, between sexes and differences based on taxonomic lineage.
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Hypotheses
Based on the prior literature, I expected that the Texas rat snakes would be found in the elevated boxes more than any other snake group. Selection of the top hide box by the Asian rat snakes was expected to mirror that of the North American rat snakes. The corn/rat snake hybrids were expected to be found in the elevated boxes less than the rat snakes but more than the corn snakes, while the pine/rat snakes should be found in the elevated boxes less than any other group.
Females of all groups were expected to be found in the elevated hide boxes more than males.
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CHAPTER 2
METHODS
Subjects
Six different testing groups of snakes were used in the experiment; an example from each is shown in Figure 2. All snakes were captive born, and each group consisted of siblings, with the exception of the group 5. All of these snakes were fed a consistent diet of lab mice on a weekly or biweekly basis.
Group 1 consisted of four yearling corn snake/rat snake hybrids (Pantherophis +
Scotophis), two males and two females. The sire of these hybrids was an albino 4 year old corn snake (Pantherophis guttatus) and the dam was a yellow/Texas rat snake intergrade (Scotophis spp.). The corn/rat snakes appear in color to be similar to Eastern corn snakes with a high variability of colors between individuals, weekly keeled scales, four prefrontal scales and a divided anal scale (Fig. 2A).
Group 2 consisted of four pine snake/rat snake hybrids (Pituophis + Scotophis), one male and three females (Fig. 2B). These snakes are roughly 3 years old and were donated by a private snake breeder from south Texas. The sire of these hybrids was a Northern Pine snake (Pituophis m. melanoleucus) and the dam was an Eastern (black) rat snake (Scotophis alleghaniensis). The pine/rat snakes appear in color to be similar to pine snakes and have more pronounced keeling on the scales; interestingly they have three prefrontal scales and a non-uniform divided anal scale.
Both of these parents were wild caught in central New York. The snakes from this group are the only snakes of sexual maturity.
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Group 3 consisted of four second generation intergrade rat snakes (50% Scotophis obsoleta, 37.5% S. alleghaniensis, 12.5% S. spiloides), two males and two females (Fig. 2C).
The sire of these snakes was a wild caught Texas rat snake (S. obsoleta) and the dam was an intergrade rat snake (Scotophis spp.). The dam was produced by a male albino black rat snake and Everglades rat snake (both S. alleghaniensis forms) bred to a female Yellow rat snake (S. alleghaniensis) and Grey rat snake (S. spiloides) intergrade. The intergrade rat snakes appear in overall color to be similar to that of Yellow rat snakes with saddles like that of Western rat snakes, a moderate variability of colors between individuals, weekly keeled scales, four prefrontal scales and a divided anal scale.
Group 4 consisted of four yearling Okeetee corn snakes (Pantherophis guttatus), two males and two females (Fig. 2D). These snakes were purchased from a private snake breeder.
These snakes are a pet industry line and are the sun kissed color phase from the original Love line. The corn snakes appear in color to be similar to wild corn snakes from the Okeetee County,
Florida region with a higher amount of red, no variability of colors between individuals, weekly keeled scales, four prefrontal scales and a divided anal scale.
Group 5 consisted of four Western rat snakes (Scotophis obsoletus) (Fig. 2E). Two of these were juvenile captive born Texas Rat snake siblings and the other two were wild caught juveniles of roughly the same size from north East Texas. The rat snakes are the typical grey coloration of naive rat snakes, no variability of colors between individuals, weekly keeled scales, four prefrontal scales and a divided anal scale.
As a niche comparison from another continent my group 6 consisted of four 2-year-old trinket snakes (Coelognathus helena helena), three males and one female (Fig. 2F). These snakes were from an original collection from University of Texas at Tyler. The trinket snakes
14 are the typical bronze coloration and pattern similar to the Southern Sri Lanka locality, small variability of colors between individuals, weekly keeled scales, two prefrontal scales and a divided anal scale.
15
2A 2B
2C 2D
2E 2F
Figure 2: Individuals from the six testing groups; 2A: Corn snake rat snake hybrids
(Pantherophis + Scotophis), 2B: Pine snake/rat snake hybrids (Pituophis + Scotophis), 2C:
Intergrade rat snakes (50% Scotophis obsoleta, 37.5% S. alleghaniensis, 12.5% S. spiloides), 2D:
Okeetee corn snakes (Pantherophis guttatus), 2E: Western rat snakes (Scotophis obsoletus), 2F: trinket snakes (Coelognathus helena helena).
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Materials and Procedures
The methodology was similar to that of Tynes (2011), adjusted for the size difference of the snakes. Each snake was placed within a 10 gallon testing tank and allowed to acclimate to the testing room temperature for 24 hours. A water dish was provided and the bottom of the tank was covered with paper towel as substrate. The snakes were separated to eliminate any social aspect of hide box selection (Tynes & Lyman-Henley, 2013). The tanks were placed side ways to provide more height and the screens were secured with bungee cords to keep the snakes from escaping. Two plastic hide boxes were placed inside the tank at different heights stacked in a vertical column using pine blocks. The pine blocks were soaked in water and flash boiled to remove any potential aromatic toxins from the wood. One hide box was on the bottom of the tank directly on the substrate, while the other was elevated to the top of the tank. The snakes were removed from the test tanks to be fed lab mice after their week of data collection.
Observations were conducted five times a day Monday through Friday at 8:00 am, 10:00 am, 2:00 p.m., 6:00 p.m. and 8:00 p.m. for the study. The study was conducted over a total of 3 weeks due to tank availability and available testing space. Eight test tanks were ran at a time and the subjects were randomized across the 3 weeks. The location in the tank of each snake was recorded. If the animal was in a hide box it was removed and placed on the substrate, and the hide box returned to its original position. The snake’s removal from the box eliminated the chance of future observations being skewed from a snake’s lack of movement from a box.
Rather, the next box that the snake is found in was due to the snake’s active selection. The tanks were spot cleaned as needed. The testing room was maintained at a constant temperature of 9 F and lighting was controlled within the room for a 12 hour on and off cycle. All procedures described herein were performed in accordance with IACUC permit number P13-11-02.
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The experimental design of this project was a six group, post-test comparison. The experimental units were the 24 snakes and the main effect was the selection of an arboreal location by the snakes. All alpha levels were set at p < 0.05. Statistical tests were conducted using the stat program R and Microsoft Excel. Tests included a one way ANOVA, a Tukey HSD test, and a chi-square goodness of fit test.
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CHAPTER 3
RESULTS
The results here express number of observations in a terrestrial or arboreal location. Each individual was observed 25 times, for a total of 100 observations for each group and the percentages are based on the observations within the group results.
The amount of time the snakes from group 1 spent in each location is shown in Table 1.
As a group, the snakes were found in a terrestrial location for 16% of the observations, either using the bottom hide box or found at ground level within the tank. These snakes were observed in an arboreal location 84% of the time, either using the top hide box or climbing the tank perch.
Males were found in the arboreal locations for 76% of the observations, while females used the arboreal locations for 92% of the observations. All individuals showed a strong preference for the top hide box.
Table 1
Results of the Corn snake/ rat snake hybrids (Pantherophis + Scotophis) and the locations that the snakes were found in during the study.
Snake Bottom Out Bottom In Top Out Top In Totals
Corn/ Rat Male 1 7 0 0 18 25
Corn/ Rat Male 2 5 0 4 16 25
Corn/ Rat Female 1 4 0 4 17 25
Corn/ Rat Female 2 0 0 8 17 25
Totals 16 0 16 68 100
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Location observations are recorded for each snake from group 2 is shown in Table 2. As a group, the snakes were found in a terrestrial location for 28% of the observations, either using the bottom hide box or found at ground level within the tank. These snakes were in an arboreal location 72% of the observations, either using the top hide box or climbing the tank perch.
Males were found in the arboreal locations 68% of the observations, while females used the arboreal locations 73.3% of the observations. All individuals showed a strong preference for the top hide box.
Table 2
Results of the pine snake/rat snake hybrids (Pituophis + Scotophis) and the locations that the snakes were found in during the study.
Snake Bottom Out Bottom In Top Out Top In Totals
Pine/ Rat Male 1 5 3 3 14 25
Pine/ Rat Female 1 3 3 2 17 25
Pine/ Rat Female 2 4 4 2 15 25
Pine/ Rat Female 3 4 2 2 17 25
Totals 16 12 9 63 100
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Location observations are recorded for each snake from group 3 is shown in Table 3. As a group, the snakes were found in a terrestrial location for 31% of the observations, either using the bottom hide box or found at ground level within the tank. These snakes were in an arboreal location 69% of the observations, either using the top hide box or climbing the tank perch.
Males were found in the arboreal locations 60% of the observations, while females used the arboreal locations 78% of the observations. Both females and male 1 showed a preference for the top hide box, while male 2 showed no obvious preference.
Table 3
Results of the intergrade rat snakes (50% Scotophis obsoleta, 33.33% S. alleghaniensis, 16.67%
S. spiloides) and the locations that the snakes were found in during the study.
Snake Bottom Out Bottom In Top Out Top In Totals
Intergrade Rat Male 1 11 4 0 10 25
Intergrade Rat Male 2 3 2 0 20 25
Intergrade Rat Female 1 3 5 3 14 25
Intergrade Rat Female 2 1 2 3 19 25
Totals 18 13 6 63 100
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Location observations are recorded for each snake from group 4 is shown in Table 4. As a group, the snakes were found in a terrestrial location for 67% of the observations, either using the bottom hide box or found at ground level within the tank. These snakes were in an arboreal location 33% of the observations, either using the top hide box or climbing the tank perch.
Males were found in the arboreal locations 14% of the observations, while females used the arboreal locations 52% of the observations. Both males showed a preference for the terrestrial location, male one outside the hide box and male two using the hide box. Female one showed no specific preference, while female two preferred to use the top hide box.
Table 4
Results of the Okeetee corn snakes (Pantherophis guttatus) and the locations that the snakes were found in during the study.
Snake Bottom Out Bottom In Top Out Top In Totals
Okeetee Corn Male 1 17 8 0 0 25
Okeetee Corn Male 2 0 18 4 3 25
Okeetee Corn Female 1 4 11 0 10 25
Okeetee Corn Female 2 4 5 1 15 25
Totals 25 42 5 28 100
22
Location observations are recorded for each snake from group 5 is shown in table 5. As a group, the snakes were found in a terrestrial location for 46% of the observations, either using the bottom hide box or found at ground level within the tank. These snakes were in an arboreal location 54% of the observations, either using the top hide box or climbing the tank perch.
Males were found in the arboreal locations 78% of the observations, while females used the arboreal locations 53.3% of the observations. Female 3 showed a preference for bottom out, female 2 showed a preference for the top locations. The male and female 1 showed no distinct preference.
Table 5
Results of the Western rat snakes (Scotophis obsoletus) and the locations that the snakes were found in during the study. *Denotes siblings.
Snake Bottom Out Bottom In Top Out Top In Totals
Western Rat Male 1 7 4 9 5 25
Western Rat Female 1* 10 2 9 4 25
Western Rat Female 2* 2 3 8 12 25
Western Rat Female 3 15 3 3 4 25
Totals 34 12 29 25 100
23
Location observations are recorded for each snake from group 6 is shown in table 6. As a group, the snakes were found in terrestrial location for 31% of the observations, either using the bottom hide box or found at ground level within the tank. These snakes were in an arboreal location 69% of the observations, either using the top hide box or climbing the tank perch.
Males were found in the arboreal locations 70.7% of the observations, while females used the arboreal locations 64% of the observations. All snakes showed a preference for the arboreal locations.
Table 6
Results of the trinket snakes (Coelognathus helena helena) and the locations that the snakes were found in during the study.
Snake Bottom Out Bottom In Top Out Top In Totals
Trinket Male 1 2 7 2 14 25
Trinket Male 2 4 3 9 9 25
Trinket Male 3 6 0 0 19 25
Trinket Female 1 5 4 3 13 25
Totals 17 14 14 55 100
24
The number of observations the groups spent in each location is shown in table 7. As a whole, the snakes were found in a terrestrial location for 36.5% of the observations, either using the bottom hide box or found at ground level within the tank. The snakes were in an arboreal location 63.5% of the observations, either using the top hide box or climbing the tank perch.
Overall the snakes showed a preference for the arboreal locations.
Table 7
Results of all groups and the locations that the groups were found in during the study.
Group Bottom Out Bottom In Top Out Top In Totals
G1: Corn/ Rats 16 0 16 68 100
G2: Pine/ Rats 16 12 9 63 100
G3: Intergrade Rats 18 13 6 63 100
G4: Corns 25 42 5 28 100
G5: Western Rats 34 12 29 25 100
G6: Trinkets 17 14 14 55 100
Totals 126 93 79 302 600
25
Data Analysis
For the ANOVA, the arboreal behavior differed significantly as a function of taxonomic groups, F(5, 18) = 4.199, MSE = 78.675, p = .0105.
Corn snakes had the lowest average of arboreal behavior with 33% of the observations
(8.25 observations) and the largest variance with 44.25. The corn snake/ rat snake hybrids had the greatest average of arboreal behavior with 84% of their observations (21 observations) and a low variance of 8.667. The pine snake / rat snake hybrids had the lowest variance of 1.333 and second greatest arboreal behavior with 72% of their observations (18 observations) in an arboreal location.
A post-hoc Tukey HSD test showed that group 1 and group 2 had a significantly higher selection of the arboreal locations than group 4 at the 0.05 level of significance ( p = 0.0492, p =
0.0065) All other comparisons were not significant.
A chi-square test of goodness-of-fit was performed to determine whether the two locations within the tank (bottom vs. top) were equally preferred for each group. Preference for the two locations was not equally distributed for group 1, X2 (df = 1, n = 4) = 46.240, p < 0.001, as they showed a clear preference for the arboreal location. Preference for the two locations was not equally distributed for group 2, X2 (df = 1, n = 4) = 19.360, p < 0.001, as they showed a preference for the arboreal location. Preference for the two locations was not equally distributed for group 3, X2 (df = 1, n = 4) = 14.440, p < 0.001, as they showed a preference for the arboreal location. Preference for the two locations was not equally distributed for group 4, X2 (df = 1, n =
4) = 11.560, p <0.001, as they showed a preference for the terrestrial locations. Preference for the two locations was equally distributed for group 5, X2 (df = 1, n = 4) = 0.640, p = 0.424, as
26 they showed no distinct preference for either location. Preference for the two locations was not equally distributed for group 6, X2 (df = 1, n = 4) = 14.440, p < 0.001, as they showed a strong preference for the arboreal location.
27
CHAPTER 4
DISCUSSION
The results of this study show that there are clear differences between the groups regarding their arboreal behavior. This indicates that there is a difference in arboreal behavior across the different taxa of snakes observed. This is to be expected given the different natural histories of the snake species observed. The differences in foraging behaviors, reproductive behaviors, and physiological adaptations across groups all play a role in a species’ ability and propensity to climb.
Group 1, the corn snake/rat snake hybrids, proved to be the most strongly arboreal of the subject groups when observing the amount of time they spent in the arboreal locations (84%).
This group was expected to show arboreal behavior that was in between that of group 4 (corn snakes) and group three and five (rat snakes). While group 1 was in the arboreal locations more than group 4 as expected, they surpassed the amount of time that the rat snakes spent in the arboreal locations. This specific behavior did not line up in between the two taxon groups as expected based on behavioral studies of these hybrids in previous literature (Tynes & Lyman-
Henley, 2013).
Group 2, the pine snake/ rat snake hybrids, proved to be primarily arboreal when analyzing the amount of time they spent in the arboreal locations (72%). This group was expected to be in the arboreal locations the least of any group because of the highly terrestrial and sub terrestrial behavior of pine snakes as documented in the literature (Burger et al., 1988).
The arboreal behavior of this group was very similar to that of the intergrade rat snakes with a difference of only 3%. This small difference may be due to a heavy behavioral influence of the rat snake parent. However, there may just simply be a lack of data on arboreal behavior and
28 climbing abilities of pine snakes. Baxley & Qualls (2009) stated that pine snakes are an understudied group of snakes. It may be that, at least for this parent population, pine snakes can show more arboreal behavior than previously reported.
Group 3, the intergrade rat snakes proved to be primarily arboreal when analyzing the amount of time they spent in the arboreal locations (69%). This group was expected to be in the arboreal locations a majority of their time and this was the case in the study. The expectation that intergrade rat snakes would utilize the arboreal locations was an assumption based on previous research conducted with intergrade rat snakes (Tynes, 2011).
Group 4, the Okeetee corn snakes (Pantherophis guttatus) spent a majority of their time in the terrestrial locations (67%). This was the only group which was more terrestrial than arboreal. This was clearly seen from the Tukey HSD test that there was a significant difference between this group and groups 1 and 2. This terrestrial behavior is supported in previous literature (Andrew & Gibbins, 2005).
Group 5, the Western rat snakes spent a relatively equal amount of time in arboreal locations (54%) compared to terrestrial locations (46%). This data did not support the hypothesis that Western rat snakes would be the most arboreal snake group in the study, a hypothesis made from the many examples of these snakes climbing in the literature (Stake et al.,
2005). This behavior may be in part to this species natural history as a generalist and adaptive species as described by Behler (2000). In the literature most of the snakes documented climbing and feeding on avian prey are adults (Mullin & Cooper, 2002). The snakes in this study were juveniles, which simply may climb less than adults. This change in behavior may be due to the size difference in prey items, as birds, even nestlings, are relatively too large for juvenile snakes to swallow. In the wild juvenile snakes are documented to feed primarily on baby mice, small
29 lizards and small frogs (Behler, 2000). The data may also be explained by the difference in individual preferences with two snakes having no preference, one snake preferring the top and another preferring the bottom locations. A larger sample size may be needed to extrapolate more information about the preferences of the species.
Four of the groups proved to be primarily arboreal when analyzing the amount of time they spent in the elevated locations. It is somewhat interesting to note that the three groups of hybrids and intergrades had the greatest amount of arboreal behavior, followed by the trinket snakes. This data supports the expectations that trinket snakes are an arboreal Asian rat snake species as documented previously in the literature (Walmiki et al., 2012). The results of the trinket snakes did mirror the results of the most arboreal groups of snakes, although it had been expected that the Western rat snakes would have taken that honor which they did not.
Females in the corn snake/ rat snake hybrids, intergrade rat snakes, pine snake/rat snake hybrids and the Okeetee corn snakes were more arboreal than the males within their respective groups. This information aligned with my hypothesis that females were expected to be in the elevated locations more than males. This assumption was based on literature, and the common moving behaviors displayed by males and females, as males typically have a larger home range and move more in an attempt to locate females (Durner & Gates, 1993). These general behaviors are seen in sexually mature snakes and juveniles have not been recorded to exhibit this difference. The corn snakes and corn/ rat hybrids were not sexually mature and the behavior of the females may show that this behavior is innate before sexually maturity occurs. Males in the
Texas rat snakes and trinket snakes were more arboreal than the females within their respective groups.
30
The information discovered from this research can have implications on how captive snake enclosures are built and configured to allow for a full range of native behaviors. All of the snake species used in this project can be found at reptile shows for sale and in the lab for research purposes, and some like the corn snake are very popular (Love, 2013). This information can be given to the pet owner or scientist to educate them regarding enclosure setup.
Information on the arboreal behavior of the trinket snakes may have implications in ecology of prey items such as bird nestlings and eggs. This species and its arboreal behavior should be considered when drafting management plans for other Southeast Asian species. Data on the arboreal behavior of the hybrid and intergrade groups may have implications in ecology of avian prey items. The results indicate that hybrids and intergrades prefer elevated locations which may put them in contact with prey items more often. Intergrades have been documented in the literature where the species borders overlap (Dunn, 2001). This could be a management concern for some prey species such as the red-cockaded woodpeckers which are preyed upon by rat snakes as well as other snakes (Cole, 2004). Bird species susceptible to nest predation in regions of hybrid zones may need to be more monitored than others.
The hybrid and intergrade groups were more arboreal than the pure-breed snake groups.
Group 1, the corn snake/rat snakes, had a greater percentage of arboreal behavior (84%) than group 4, the corn snakes (33%) and group 5, the Western rat snakes (54%). Group 2, the pine snake/rat snakes, had a greater percentage of arboreal behavior (72%) than group 4, the corn snakes (33%) and group 5, the Western rat snakes (54%). Group 3, the intergrade rat snakes, had a greater percentage of arboreal behavior (69%) than group 4, the corn snakes (33%) and group
5, the Western rat snakes (54%). The arboreal behavior seen in groups 1, 2, and 3 may represent examples of behavioral hybrid vigor, which has been documented in a few species of hybrid
31 reptiles (Robbins, Pruitt, Straub, Mccoy & Mushinsky, 2010). Behavioral hybrid vigor regarding arboreality could mean that the hybrids have an advantage, having a greater ability to exploit arboreal resources. Analysis of the morphologic traits of the hybrids may better explain this, as some behavioral vigor is a result of morphology (Robbins et al., 2010).
This study indicates that there are clear differences between the groups regarding their arboreal behavior. While the difference in arboreal behavior across the different taxa of snakes is to be expected given their natural histories, the arboreal behavior of some of the groups did not align with the hypotheses. The hybrid groups especially showed surprising preferences for the arboreal location, something that may need to be further investigated. The occurrence of behavioral hybrid vigor demonstrated in this study could have major implications beyond the scope of this study.
32
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