Red - H. n. kennerlyi . H. nasicus occurs throughout Texas. However, there are large gaps in portions of the state. Of course, the question of where this species occurs in Texas is the focus of this study and will be dealt with in detail. Green - H. n. kennerlyi .
Stars represent fossil records.
The populations of H. nasicus seem to be highly correlated to coarse alluvial and marine deposits. In instances where the snakes appear to occur outside of these broad deposits they are still associated with alluvial deposits. Whether this is a dependency on soil type itself or food preference alone still remains to be tested as well as whether there is indeed a significant correlation at all. However, the species of the genus Heterodon in general tend to depend on soil structure for thermoregulation, reproduction and foraging. It is believed that the upturned rostrum of this genus is specifically designed for burrowing which would suggest loose soil substrates.