Written by Alamo Area Master Naturalist Sal Scibetta
WHAT ARE TURTLES?
Turtles are probably one of the most easily identifiable groups of animals. Simply put, they are shelled reptiles. All turtles have some kind of shell which is basically an expanded ribcage. Some turtles’ shells are domed, some are flattened, some of soft and leathery. The nomenclature we use in English can be confusing as to the three common names associated with shelled reptiles: Turtles, Tortoises and Terrapins. Generally speaking, turtles are aquatic or semi-aquatic, omnivorous, and usually have a flatter shaped shell. Tortoises are mainly terrestrial and herbivorous, have elephant-like, columnar legs and usually a high, domed shell. Terrapins are only one species, the Diamondback Terrapin, which lives in brackish water along the Gulf and Atlantic coasts. As simple as this seems, it only pertains to English names in the US. England and Australia have different definitions for the names of shelled reptiles.
TEXAS IS A TURTLE HOTSPOT!
Most people in this organization know that Texas is a hotspot for biodiversity. This is also the case with turtles. In fact, Texas is the second most diverse state in the US and the Southeast US has the largest diversity of turtles in the world!
TURTLES IN BEXAR COUNTY AND CENTRAL TEXAS
There are 8 native turtles and one tortoise that call Bexar County home. The four most frequently encountered are the Red Eared Slider, Texas Cooter, Guadalupe Spiny Softshell and Common Snapping Turtle. The Texas Cooter and Guadalupe Spiny Softshell are endemic to Texas. When you expand the area out to encompass the Hill Country, there are 13 different species and two more Texas endemics.
MOST COMMON TURTLES IN BEXAR COUNTY
Red-Eared Slider (Trachemys scripta elegans)
Listed as one of the Top 10 Most Invasive Species in the World[i] ,the Red-Eared Slider is actually native to San Antonio! This is the most commonly kept pet turtle in the world. The hatchlings are a bright green with a bright red stripe behind the eyes. These turtles are farm-raised and the babies are sent to pet shops around the world, where unfortunately, they are often released into the wild. They are a true habitat generalist. They live in many aquatic habitats from clear spring-fed streams, lakes, rivers and manmade cattle tanks, golf course ponds and even sewage retention ponds. Red-eared Sliders are omnivorous, eating pretty much anything natural in the water. Juveniles mainly eat more animal matter, but as they grow, they will eat more plant matter. Even though this turtle is extremely common it can be often misidentified. Male Red Eared Sliders as they age, become melanistic or turn black, even to the point of losing the red eye stripe.
Texas Cooter (Pseudemys texana)
The Texas Cooter, or Texas River Cooter was once believed to be a subspecies of the River Cooter (Pseudemys concinna) but has been elevated to a unique species. This turtle is probably the most commonly seen turtle in the San Antonio area. This turtle is frequently seen basking in urban lakes and ponds, often with Red Eared Sliders (Trachemys scripta elegans) and the other endemic turtle, the Guadalupe Softshell Turtle. The Texas Cooter is herbivorous, eating algae and aquatic plants.
Spiny Softshell (Apalone spinifera guadalupensis)
Softshell turtles are different from most turtles in that they have a leathery skin covering the skeleton. The Guadalupe Spiny Softshell is the only softshell native to the San Antonio area. Its pancake-like shell and snorkel nose make them easy to identify. This subspecies of the Spiny Softshell is endemic to central Texas and found in the Guadalupe and Nueces River systems. It is also frequently encountered in urban lakes and ponds as well as the region’s rivers. Like other softshell turtles, the Guadalupe Spiny is carnivorous, eating aquatic invertebrates like insects and crayfish as well as fish. They are also sexually dimorphic (when different genders of a species have different characteristics not related to reproductive organs) with the females being significantly larger than the males.
Snapping Turtle (Chelydra serpentina)
With a range including most of Central and Eastern North America, the Common Snapping Turtle is not surprisingly found in San Antonio. While this turtle seems to have a preference for larger bodies of water, it is also found in small creeks and streams. (I’ve even seen one in the acequia along Mission Reach) The much maligned and misunderstood Snapping Turtle is feared for its aggressive reputation. It also has an undeserved reputation as a pest because of the belief it commonly consumes game fish. Snapping turtles are omnivores, eating all kinds of animal matter, especially carrion and insects as well as aquatic vegetation. While Alligator Snapping Turtles (Macrochelys temminckii) are Texas residents, they only live in east Texas. However, they are often reported, which is likely a mistaken identity due to the rugose nature of carapace in juvenile Common Snapping Turtles.
OTHER TURTLES IN OUR AREA
Yellow Mud Turtle (Kinosternon flavescens)
Believed to be a common turtle, the Yellow Mud Turtle is infrequently encountered due to their secretive nature. The Yellow Mud Turtle lives in small, murky bodies of water with muddy or sandy bottoms. These turtles are encountered after heavy summer rains. They will often be seen far from water sources as they walk long distances to a new location. Not a lot is known about their natural history due to their secretive nature. They are believed to be mainly carnivorous, eating any available animal matter, including carrion. They may also eat some plant matter. This is a small turtle, reaching lengths of up to 16cm. Males are usually slightly larger than the females.
Musk Turtle (Sternotherus odoratus)
This turtle is our smallest resident, reaching lengths up to 11cm and hatchlings are only around 20mm. The Common Musk Turtle is also called Stinkpot due to the musk it exudes from Rathcke’s Glands located on either side of the plastron bridge. The plastron (bony plates on the underside) of this turtle is also significantly reduced, with skin between the scutes. These turtles live in a variety of aquatic habitats from small streams to lakes. Musk turtles will “walk” the bottom of creeks looking for prey including any invertebrate, even mussels, clams and snails. This is also the turtle that occasionally shows up in bags of live crawfish. It is most commonly encountered after heavy rains and is often caught in crawfish traps.
There are three species of terrestrial turtles that live in the San Antonio area., The Ornate Box Turtle, the Three Toed Box Turtle and the Texas Tortoise.
Ornate Box Turtle (Terrapene ornata)
The Ornate or Plains Box Turtle is found throughout most of Texas, including the entire Hill Country. They are extremely uncommon in Bexar County and have been experiencing a significant population decline lately. It is not uncommon to hear long-time residents comment on how they don’t see them anymore when the turtles were commonly found decades ago. Ornate Box Turtles are about 10-15cm long. The carapace is usually a dark brown to black with 5-9 yellow radiating stripes on each scute. Ornate Box Turtles are omnivorous. There does seem to be a predilection for more animal matter. Beetles, earthworms, caterpillars and grasshoppers and main prey items but fruits, forbs, and cactus pads and fruits will be eaten as well.
Toed Box Turtle (Terrapene carolina triunguis)
While more common in east Texas, the Three Toed Box Turtle is also extremely uncommon in Bexar County. Three Toed Box Turtles are typically a woodland species and prefer edge habitat near bodies of water, both permanent and temporary.[ii] Even with the warmer temperatures, this turtle does not appear to be active during the cooler months and typically hibernates from early November to late March. It will occasionally emerge and even forage during some of the warm, sunny days. They are truly omnivorous, eating both plant and animal matter readily. Like all box turtles, they have an affinity for worms, slugs, and other invertebrates as well as fruit and forbs.
Tortoise (Gopherus berlandieri)
Finally, the Texas or Belandier’s Tortoise is the smallest (about 22 cm) tortoise native to North America and possibly the Western Hemisphere. Our native tortoise can be found throughout Bexar County and even inside the San Antonio city limits. These tortoises are fairly common in South Texas. Texas Tortoises are different from most Gopherus (North American tortoises) species in that they do not dig their own burrow. They dig small depressions called pallets. These pallets are usually found in close association with their main food, the Prickly Pear Cactus (Opuntia engelmannii). They not only eat the fruit of the cactus, but also the pads. In addition to cacti, they also eat grasses and forbs. Even though tortoises are considered herbivores, they also have been known to eat insects and feces, especially feces of the Collared Peccary (Dicotyles tajacu).[iii] Originally populations suffered from over collection in the pet trade and was even used in the cosmetic industry where the fat was used in skin cream. While collection is illegal today, the tortoises are under threat from increased road mortality and loss of habitat. Texas Tortoises are a state protected species and it is illegal to keep in Texas without a permit.