Plestiodon skiltonianus

Western Skink

By Elba Sofie Fridriksson

Background image: http://reptile-database.org/

(Hosek, 1995)

Western Skink Image from: http://reptile-database.org/

(Hosek, 1995)

Introduction

The Plestiodon skiltonianus, also known as the Western Skink, is a fascinating organism with unique characteristics. This organism is a small smooth scaled lizard with a dull grey striped body and long bright blue tail. With a tail that can be twice the size of its body, the western skink is an amazing reptile to observe. The Plestiodon skiltonianus' escape behavior was recently observed in a study on the individual variability of western skink behavior with high human disturbances. The article, "High Human Disturbance Decreases Individual Variability in Skink Escape Behavior" by Dana M. Williams, Phat-Tan Nguyen, Kemal Chan, Madeleine Krohn, and Daniel T Blumstein, 87 western skinks were studied on the island Mo’orea, French Polynesia. With different levels of human and domestic disturbance on the island, scientists wanted to observe behavior plasticity to see how Western Skinks individual responses to predators would evolve with the interaction of humans.

Background

The Kingdom Animalia is the largest kingdom that composes all animals and organisms with vertebrate such as the Plestiodon skiltonianus (Hammerson. G, 2005).

The phylum Craniatia and subphylum Vertebrata is what the western skink belongs to (Hammerson. G, 2005).

The rest of the taxonomy of the Western Skink is (Hammerson. G, 2005):

Class:Reptilia

Order: Squamata

Suborder: Lacertilia

Family: Scinidae

Genus Plestiodon

Species : Plestiodon skiltonianus.

The nomenclature explains the Genus, Plestiodon, which means lizard. The specific epithet, skiltonianus, meaning smooth scaled (Hammerson. G, 2005).

The Plestiodon skiltonianus is a eukaryotic, multicellular consumer that produces offspring through sexual reproduction. These reptiles lay eggs with a clutch size of 2-6 (Hammerson. G, 2005). The western skink also falls under the category of being a Deuterostome, which means that in embryonic development the anus developed before the mouth (Hammerson. G, 2005). This smooth scaled lizard is a notochord meaning that it has a middle alignment structure within its body for vertebrate development (Hammerson. G, 2005). This reptile respires through its lungs and is ectothermic meaning that its environment will regulate body temperature. The western skink uses a defense mechanism of detaching its long blue tail from the body that will wiggle to distract a predator while the western skink escapes (the tail will grow back as a grey color) (Williams, et al., 2019).

Background Image

(Osdol, 2021)

Western Skink Image from: http://reptile-database.org/ (Hosek, 1995)

Habitat

Found in North-Western United States, French Polynesia and South Canada (Hammerson. G, 2005).
North to South: British Columbia to California (Hammerson. G, 2005).
West to East: Washington/Oregon to Wyoming/Montana (Hammerson. G, 2005).
Habitat is grassland, open woods and forests, and rocky areas near streams. Takes shelter under rocks and burrows itself in soil (Hammerson. G, 2005).

Open Field Ecosystem Image From: https://entomology.umd.edu/news/what-is-an-old-field-ecosystem-a-look-from-above-and-below (lamas and Stewart, 2018)

Western Skink Eating Insect, Image from: https://animalia.bio/american-five-lined-skink (AMERICAN FIVE-LINED SKINK, 2022)

Food

Western Skinks are carnivorous and feed on a wide variety of insects, spiders and earthworms. The western skink preys upon small invertebrates (Hammerson. G, 2005).

Western Skink Image from: (Western Skink, 2021) https://en.wikipedia.org/wiki/Western_skink

Interactions with other Organisms

Western skinks use chemical signals in social interactions and when searching for prey (Laurie, 2018). The western skinks discriminate chemical signals that are influenced by sex hormones (Laurie, 2018). These hormones influence some parts of their morphology, primarily in males when it comes to mating (Laurie, 2018).

Important Information Regarding the Experiment

Vertebrates such as the western skink display some components of individual behavioral plasticity by adding to stressors through behavior changes (Williams, et al., 2019). . Individual variability in response to urbanization can have major impacts on fitness. For example, escape behavior may be reduced through phenotypic diversity from microevolution (Williams, et al., 2019). .

Terminology:

Individual Variability - the individual organisms' response over trials.

Phenotypic Diversity - consequence of genetic variation as a result of behavioral factors (Williams, et al., 2019).

Behavior Plasticity - change in an organisms' behavior as a result of exposure to stimuli (Williams, et al., 2019).

FID- flight initiation distance (Williams, et al., 2019).

Urbanization- process of making an area more urban (Williams, et al., 2019).

AIC - Akaike Information Criterion, used to create figure 2 that shows the most information along with a slope line of best fit (Williams, et al., 2019).

Figure 2 Distance Fled (DF) Image from:

https://academic.oup.com/cz/article/66/1/63/5492624

(Williams, et al., 2019)

AIC, Table 4 Showing Distance Fled Image from: https://academic.oup.com/cz/article/66/1/63/5492624

(Williams, et al., 2019)

Data Analysis

"High Human Disturbance Decreases Individual Variability in Skink Escape Behavior"

Authors: Dana M. Williams, Phat-Tan Nguyen, Kemal Chan, Madeleine Krohn and Daniel T Blumstein

Scientists wanted to see if high human disturbances and domestic disturbance affected western skink escape behavior (Williams, et al., 2019).

Observers were trained to approach skinks at a constant speed of 0.5m/s and drop flags noting where the skink was when approach, the instance flight distances, and the distance fled (Williams, et al., 2019). .

87 Western Skinks Observed (Williams, et al., 2019).
13-day Testing Period (Williams, et al., 2019).

Results

Decreased individual variability in Western Skinks in urban areas (high-medium human disturbances) will lead to lower behavior plasticity (change in western skinks’ behavior as a result of exposure to stimuli) (Williams, et al., 2019). . Urbanization has led to these reptiles becoming more stressed within their habitats, resulting in the change to their responses to predators and surrounding organisms. The individual phenotypes have been altered to best suit skinks exposed to humans and change their anti-predator responses (Williams, et al., 2019). Western skinks at low human disturbance sites fled at shorter distances compared to the medium to high human disturbance sites (Williams, et al., 2019). As a result, skinks in high human disturbance sites had lower variable FIDs(flight initiation distances) than at low human disturbance sites (Williams, et al., 2019). For this reason, there is a decrease in individual variability within skinks in escape behavior (Williams, et al., 2019).

Conclusion

In conclusion, Western Skinks individual variability in escape behaviors was lower at high-medium disturbance sites than low human disturbance sites.

The impact of humans, domestic animals such as chickens and cats, cause skinks in high-medium disturbance areas to flee at further distances trying to seek out refuge and become stressed (Williams, et al., 2019).

Leading to skinks not tolerating close approach distances like the low human disturbance site skinks.

This discovery is important because it shows how urbanization has caused such small animals in the wild to change their morphological data just by being exposed to new stimuli (Williams, et al., 2019). The threat of other animals changing their responses in the wild will not stop at the Western Skink, but may affect many other organisms too.

References

Primary Literature:

Williams, Dana M., Phat-Tan Nguyen, Kemal Chan, Madeleine Krohn, and Daniel T Blumstein. 2019. “High Human Disturbance Decreases Individual Variability in Skink Escape Behavior.” Current Zoology 66, 1: Pages 63–70. https://academic.oup.com/cz/article/66/1/63/5492624

Secondary Literature:

Hammerson, G. “ Plestiodon skiltonianus Western Skink"[Internet]. NatureServe Explorer. September1, 2022. Available from https://explorer.natureserve.org/

Vitt, Laurie. "Skink" [Internet]. Encyclopedia Britannica. October 10, 2018. Available from https://www.britannica.com/animal/skink

Images from:

https://reptile-database.reptarium.cz/species?genus=Plestiodon&species=skiltonianus

https://fineartamerica.com/featured/blue-tailed-skink-hibernating-scott-d-van-osdol.html

https://www.usgs.gov/media/images/western-skink

https://en.wikipedia.org/wiki/Western_skink

https://entomology.umd.edu/news/what-is-an-old-field-ecosystem-a-look-from-above-and-below

https://animalia.bio/american-five-lined-skink

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