Yellow Bellied Slider Turtle Experiment

Introduction

In this study, the effect of temperature on yellow-bellied slider turtle (Trachemys scripta scripta) reproductive rates will be measured. The experiment will be controlled in a laboratory setting to determine whether either higher or lower temperatures will cause the reproductive rates of the turtle to increase or decrease. Reproductive rate, according to Pianka (1997), is defined as “average number of age class zero offspring produced by an average newborn organism during its entire lifetime.” This is important as the number of offspring produced by the species determines the growth of the population.

The experimental unit in this study is the yellow-bellied slider. The yellow-bellied slider is a common turtle found in the

Southeast, ranging from northern Florida to southeastern Virginia. These turtles can utilize a wide variety of habitats, including, but not limited to, rivers, lakes, and wetlands. (Conant & Collins, 1998) They are large turtles, and reach up to 10 inches in length; females grow to a much larger size than do males. (Mills, Scott, & Nowak, n.d.) Typically, females will grow from anywhere between 8 to 13 inches long. (Coy, 1998) Slider turtles have a dark brown or olive green shell and are mainly characterized by a yellow blotch behind the eye and on the side of the head. As the name suggests, these turtles have an almost completely yellow underside. Adult males tend to grow darker as they age. (“Yellow-Bellied Slider Turtle Fact Sheet”, n.d.)
Slider turtles’ breeding seasons are in the fall and the spring.

During this time, a male turtle will swim in front of a female, wave his fingernails in front of her, caress her chin, or create water currents above her head. In this way, he may entice her to mate. Several weeks after mating, a female will dig a hole with her hind feet and deposit six to ten eggs in it. The eggs incubate for two to three months and the young often stay in the nest over the winter, emerging the next spring. (Mills et al., n.d.) Hatchlings are almost entirely carnivorous, preferring a diet of tadpoles, insects, and dead fish. As they age, however, these turtles can subsist on a vegetative diet, including algae, leaves, stems, roots, fruits, and seeds, although their growth rate may be severely lower than that of meat-eating turtles. Slider turtles can live for more than 30 years in the wild. (“Yellow-Bellied Slider Turtle Fact Sheet”,

n.d.)
Wetlands are extremely important to this species, because they provide the perfect habitat. These turtles prefer to live in quiet, muddy, permanent waters, with good places to sit in the sun and aquatic vegetation. (Dewey & Kuhrt, 2002) Therefore, wetlands fulfill all the requirements that these turtles have.
Wetlands are also important as an ecosystem. They directly and positively affect other biomes in many ways. Wetlands prevent flooding by holding water in when water levels are high and slowly releasing the water when levels are low, thereby keeping river levels balanced and surface water relatively pure. Wetlands also counter erosion due to the high levels of aquatic vegetation that surround this ecosystem. This vegetation is able to slow the water flow enough to counter erosive forces in lakes and rivers. (“Why Are Wetlands Important?”, 2002) Wetlands help reduce the impact of storm damage, as well as fostering high levels of biodiversity. Wetlands are some of the most productive ecosystems on earth. (“Why are wetlands important?”, 2013)
The independent variable in this experiment is the temperature of the terrestrial area on which the female turtles must lay their eggs.

Although slider turtle mating occurs inside the water, suitable terrestrial area is necessary for successful egg-laying. Many different factors affect temperature, such as location, altitude, ocean currents, and proximity to water. (Rader, 2013) Temperature can also affect other parts of an ecosystem, such as the behavior of different plant and animal species. The dependent variable is the reproductive rate of the yellow-bellied slider. Whether the temperature of this area affects the reproductive rate is what will be measured in this experiment. The controlled variables include size of turtles, habitat, water temperature, amount of food, and size of tank. The research leads one to believe that if temperatures drop, then reproductive rates will also

drop.

Methods and Materials
The materials used to conduct this lab are as follows:
4 75-gallon tanks, filled with about 16-18 inches of water each
160 lbs of gravel (40 lbs each)
4 aquarium heaters
8 male yellow-bellied slider turtles (2 per tank)
8 female yellow-bellied slider turtles (2 per tank)
aquatic turtle food & leafy greens
rocks for dry basking spot
The method is as follows:
In each 75-gallon tank, fill 16-18 inches of water. Then, set up a slight slope with the 40 lbs of gravel. At the top of the slope, put a few rocks for a dry basking spot.
Place two male and two female yellow-bellied slider turtles in each tank.
Keeping every other variable the exact same, change the temperatures of each tank as follows:
Tank 1: 50°F
Tank 2: 60°F
Tank 3: 75°F
Tank 4: 90°F
Feed the same amount of the aquatic turtle food and the leafy greens to the turtles every other day.
Record data.