Flathead snake (Tantilla gracilis)

Flathead snake
IUCN Red List species status – Least Concern LEAST

Top facts

  • Although it is thought to be quite common throughout its range, the flathead snake is rarely seen due to its secretive habits.
  • The flathead snake is the only member of the genus Tantilla that usually does not have a distinctive black cap.
  • Along with other members of the genus Tantilla, the flathead snake has two slightly enlarged teeth at the back of the jaw which act as rudimentary fangs..
  • In Texas it is thought that non-native fire ants have reduced the population size of the flathead snake.
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Flathead snake fact file

Flathead snake description

GenusTantilla (1)

The flathead snake (Tantilla gracilis) is well adapted for an underground life, with its minute eyes, moderately flattened head, and diminutive size (2). This species is tan, reddish or tallow-brown in colour, with a slightly darker head which, uniquely for a species of the genus Tantilla, usually doesn’t have a distinct black cap (2) (3). The underside of this snake is whitish to salmon pink with more vivid colouring under the tail. While it is common throughout much of its range, it is rarely seen because of its secretive habits (4).

Also known as
Flat-headed snake.
Length: 18 - 20 cm (2)

Flathead snake biology

The flathead snake is thought to be nocturnal, but can be found during the day under logs, rocks, and other moist debris, but during summer the snake burrows deeply into the ground as the soil surface dries (2). The flathead snake’s diet consists of a variety of arthropods, including scorpions, spiders and centipedes (2).

Like all members of the genus Tantilla, the flathead snake possesses moderately enlarged teeth at the end of each upper jaw bone, along with rudimentary toxin glands. The toxins from the glands enter the saliva of the flathead snake and are not directly injected into prey items, but nevertheless the toxins help the flathead snake to incapacitate its prey (2). The toxin is not harmful to mammals, and this snake is safe to handle (2) (3).

The flathead snake lays its eggs between April and May under rocks in shallow underground hollows or within decaying vegetation (1) (5). The average clutch size of this species is between one and four eggs, and this snake is thought to produce a single clutch a year, which usually hatch in September. The young are about seven centimetres long at birth (5).


Flathead snake range

The range of the flathead snake extends from northern Mexico, northwards towards Illinois and Kansas in the Unites States, including Texas, Oklahoma, Arkansas, Missouri, and Louisiana (1).


Flathead snake habitat

The flathead snake’s habitat includes wooded hillsides, rocky forest edges, pine-oak uplands, moist deciduous woodland, pine woods, and grass-brushland (1) (2). This species often takes refuge under rocks or logs after rain (1).


Flathead snake status

The flathead snake is classified as Least Concern (LC) on the IUCN Red List (1).

IUCN Red List species status – Least Concern


Flathead snake threats

There are some reports that non-native fire ants (Solenopsis invicta) have caused a decline in the Texan population of the flathead snake (1) (6), but this is unconfirmed. This snake has a large range, many subpopulations and an estimated population size of over 100,000 individuals and is therefore not considered to be at risk of extinction (1).


Flathead snake conservation

The flathead snake is found in many protected areas throughout its range. This species receives no legal protection from the U.S. Fish & Wildlife Service, although the state of Illinois considers it to be threatened in this part of its range (3). The potential threat of invasive fire ants must be investigated as a potential threat to this species (1) (6).


Find out more

Find out more about the flathead snake:

  • Werler, J.R. and Dixon, J.R. (2000) Texas Snakes: Identification, Distribution, and Natural History. University of Texas Press, Texas.

Find out more about reptile conservation:



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A major grouping of animals that includes crustaceans, insects and arachnids. All arthropods have paired jointed limbs and a hard external skeleton (exoskeleton).
A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
An organ that makes and secretes substances used by the body.
Describes species introduced deliberately or unintentionally outside their natural habitats where they have the ability to establish themselves, invade, outcompete natives and take over the new environments.
Of or relating to the immature stage in an animal’s lifecycle, after it hatches from an egg and before it changes into the adult form. Larvae are typically very different in appearance to adults; they are able to feed and move around but are usually unable to reproduce.
Active at night.


  1. IUCN Red List (April, 2014)
  2. Werler, J.R. and Dixon, J.R. (2000) Texas Snakes: Identification, Distribution, and Natural History. University of Texas Press, Austin, Texas.
  3. Illinois Natural History Survey - Flathead snake (April, 2014)
  4. Cobb, V.A. and Reeder, T.W. (2004) Diet and Prey Size of the Flathead Snake, Tantilla gracilis. Copeia, 2004(2): 397-402.
  5. Cobb, V.A. (1990) Reproductive notes on the Eggs and Offspring of Tantilla Gracilis (Serpentes: Colubridae) with Evidence of Communal Nesting. The Southwestern Naturalist, 35(2): 222-224
  6. Tenant, A. (2006) Lone Star Field Guide to Texas Snakes. Taylor Trade Publishing, Maryland.

Image credit

Flathead snake  
Flathead snake

© Andrew Hoffman

Andrew Hoffman


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