Proposal for the Observation of Milk Snakes in Southern Pennsylvania

Introduction

In the world of herpetology, the common Milk Snake, Lampropeltis Triangulum, contains particular characteristics that separate them from other types of snakes. The Milk Snake is a snake that has an origin that traces back to Mexico and Central America with typically warm and rainy climates as its observed habitat (Williams, 1978). However, this snake has the most diverse range of any snake species in the Americas, with several subspecies throughout North and South America (Contant and Collins, 1991). Though this is an essential snake that resides within these particular regions, there are various types of snakes that contribute to this type of environment as well.

The subspecies Lampropeltis Triangulum Triangulum, or the Eastern Milk Snake, has made its way into popular culture of the Pennsylvania area as a commonly-viewed snake in gardens and urban areas. It's not considered a dangerous animal. Nevertheless, aside from a few sparse studies, such as Msehaka and Delis’ observation of snakes near a military base in South-Central Pennsylvania (2014), there have rarely been any studies on the Eastern Milk Snake in the South Pennsylvania area. Due to the lack of research that has been done in the South Pennsylvania area, this study will be focused on the characteristics and biology of the snake in this set habitat. The Milk Snake has been observed to have a direct link between its biology and ecological factors such as temperature (Row & Blouin-Demers, 2006) geography (Fitch & Fleet, Natural History of the Milk Snake (Lampropeltis triangulanum) in Northeastern Kansas, 1970) and interaction with other species (Meshaka & Delis, 2014). These observations will be taken near the Harrisburg area, 40°15’49.2480” N, -76°53’26.6604” W. This latitude/longitude will be used for the experiment and will set the parameters for the study. The biology of these snakes will be observed within the area with a slight margin for expanded outside areas.

In addition, morphology will be closely studied throughout this project along with the scale color, size, and skeletal structure. The Eastern Milksnake is often distinguished from other subspecies due to its different color and size (Fitch & Fleet, 1970) (Smith & Stephens, 2003). The white, cream colored belly of the snake is often used in its identification and has become a common visual characteristic for the animal (Hamilton, Hart, & Sites, 2012). Other snakes have shown differences in size and appearance due to sexual dimorphism (2012). The delimitation of Milk Snakes and distinguishing it has been a difficult subject in reptile taxonomy, with traditional morphological techniques still being occasionally problematic in the identification of the Milk Snake (Ruane, Bryson, Pyron, & Burbrink, 2014). The Eastern Milk Snake has often been misidentified amongst both common observers and academic researchers (Smith & Stephens, 2003) (Pennsylvania Fish and Boat Commission, 2015). Due to the difficulty of its identification, this study will seek to clarify the morphology of the Eastern Milk Snake and establish its distinguishing factors from other snakes in the area.

Recent studies have shown that there were variable changes in Milk Snake behavior in response to the Pleistocene climate change in Central America and Mexico (Torres-Cavarjal & Burbrink, 2015), although these changes were not uniform amongst all the demographics and subspecies of the snake (2015). This was as recent as 12,000 years ago (2015) and could potentially have changes occurring in this species due to climatic factors. While the current climatic landscape may be different, it is changing due to greenhouse gas accumulation and the added man-made temperate variables which are affecting the habits of reptiles at an increased rate (Olson & Saenz, 2013) (Wake, 2007) (Sinervo, Mendez-de-la-Cruz, & Miles, 2010). This study will be observing the habitual and adaptive changes of the snake in the context of recent man-made climate change and its own reactions to the encroachment of urban settlement on its natural habitat. The reactions of this animal will also be taken into context of the climatic changes that are happening in the area as of the past fifty years.

The reproduction cycle of the Milk Snake will be important for this study. In areas such as the Midwestern United States, the snake is often known to begin mating in the late spring with eggs laid in June to July and hatching in September before they need to hibernate (Fitch & Fleet, Natural History of the Milk Snake (Lampropeltis triangulanum) in Northeastern Kansas, 1970) (Fitch, 1999). There have been studies over the copulatory habits of the species that observed the mating rituals and habits of partner attraction between Milk Snakes (Gillingham, Carpenter, Brecke, & Murphy, 1977). However, much of the specifics of reproduction and mating in milk snakes are still largely unknown. They have been observed in captivity to produce multiple clutches of offspring (Tyron & Murphy, 1982) but still have unknown behaviors in regards to copulation and ovulation (Smith & Stephens, 2003). Because the breeding habits of Lampropeltis Triangulum are still slightly unknown outside of captivity, this study will not only attempt to draw conclusions about the reproductive cycle of the subspecies Triangulum but for the species as a whole. This study will attempt to set observations for the timing of copulation for these snakes and their gestation periods in the wild, as well as the potential for any differences in behavior from other subspecies.

Eating and other behavioral habits will be monitored in this study. In the past, snakes have been known to show differences in feeding habits due to their size and sexual dimorphism (Hamilton, Hart, & Sites, 2012) (Shine, 1984). The feeding of the Milk Snake can be varied in the account of its own size and the size of its prey (Fitch & Fleet, 1970) along with the availability of prey (Hamilton, Hart, & Sites, 2012). If there is reduced prey availability due to urban settlement, then the eating habits of the snake could be subject to change.

Objectives

The study will be observing the various characteristics of the Milk Snake (Lampropeltis Triangulum Triangulum) in the context of their habitat of Southern Pennsylvania. While there have been studies on the Milk Snake in the past, there are scarce resources on its biology in the latitude/longitude parameters of 40°15’49.2480” N, -76°53’26.6604” W. Due to the lack of resources during the research process, there will be continued observations of the snake to add data and findings for the species as a whole. The context of this area will be important for the continued conservation of the species and its survival in the increasingly urbanized area. The ecology and its effects on the Milk Snake will also be studied in the context of the given area. With the growing concern of climate change, there is potential for changes in behavior in snakes in the studied latitude and longitude.

The dominance of the Eastern Milk Snake will be studied and will be assessed in the context of other snake species that live in the ecosystem. Also, interspecific conflicts will be observed in regards to the American Garter Snake and the Eastern Milk Snake. The populations of snakes in area perimeter will also be considered as their interactions with the Milk Snake will be key in habitual changes.

Expected Results

The difference in theology and geography from the majority of other studies done on the snake should be palpable. Because of Pennsylvania’s cooler temperatures in comparison to Mexico or even the Southern United States, there should be noticeable behavioral differences between the Milk Snakes of this area and those that have been observed in the past. While the differences may not be dramatic when compared to other subspecies of Lampropeltis triangulum, they should be clear enough to be observed and recorded with reasonable conclusions made about them. The results should show that there are certain different biological factors that separate Triangulum from its counterparts within the Lampropeltis triangulum species.

Habitual differences will be the most commonly expected results in this study. The habits of the snake in reaction to changes in habitat, climate, and species interaction should be distinguished from other snake species. The Eastern Milk Snake has already been studied to have habitual conflict with other species in the neighboring area (Meshaka & Delis, 2014). This could mean that its interactions with other species are due in part by urban encroachment on their natural habitat. With the continual population density of these snakes growing as their habitats are increasingly restricted, the chances for habitual changes between species will increase. Thermal plasticity of snakes due to climate change has given a basis that the same could be happening to the Milk Snakes of this area (Aubret & Shine, 2009). The changes in snakes, especially those in the younger stages of the life cycle, will be expected in the observed population.

Potential differences in morphology could occur due to population genetic mutations in the area. However, this is not certain and will require study in the field. Gradual adaptive changes of the snake in the area could also change certain morphological aspects, such as size. While there will most likely not be dramatic adaptive differences in the short time that Milk Snakes have been officially observed in North America, the recent discovery of rattle buttons, and delays of rattling in juvenile rattlesnakes, bring up the potential for adaptive differences in similar reptiles (Sester, Moncino-Deloya, & Meik, 2011).

References

Aubret, F., & Shine, R. (2009). Thermal plasticity in young snakes: How will climate change affect the thermoregulatory tactics of Ectotherms? Experimental Journal of Biology, 242-248.

Contant, R., & Collins, J. (1991). A field guide to reptiles and amphibians: Eastern and central North America. Boston: Houghton Mifflin Company.

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Fitch, H., & Fleet, R. (1970). Natural history of the milk snake (Lampropeltis triangulanum) in Northeastern Kansas. Herpetologica, 387-396.

Gillingham, J., Carpenter, C., Brecke, B., & Murphy, J. B. (1977). Courtship and copulatory behavior of the Mexican milk snake, Lampropeltis triangulum. The Southwestern Naturalist, 187-194.

Hamilton, B. T., Hart, R., & Sites, J. W. (2012). Feeding ecology of the milk snake (Lampropeltis triangulum, Colubridae) in the United States. Journal of Herpetology, 515-522.

Meshaka, W., & Delis, P. (2014). Snake assemblage structures and seasonal activity patterns on a military base in south-central Pennsylvania: Land management implications for snake conservation. The Journal of North American Herpetology, 7-20.

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Shine, R. (1984). Reproductive biology and food habits of the Australian elapid snakes of the genus Cryptophis. Journal of Herpetology, 33-39.

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Smith, B., & Stephens, N. (2003). Conservation assessment of the pale milk snake in the Black Hills National Forest, South Dakota and Wyoming. Custer: United States Department of Agriculture.

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Tyron, B. W., & Murphy, J. (1982). Miscellaneous notes on the reproductive biology of reptiles. Kansas Academy of Science, 96-119.

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Williams, K. L. (1978). Systematics and Natural History of the American Milk Snake, Lampropeltis triangulanum. Milwaukee: Milwaukee Public Museum.