A habitat is the type of natural environment in which a species can live and grow. This includes adequate food, a water supply, shelter, and associated species. Some species, called generalists, can live in a wide variety of habitats. Examples of generalists include raccoons, sparrows, and squirrels. Other species, called specialists, have evolved with very specific habitat needs. Examples of these needs are the constant temperatures required by some cave species or the presence of a certain plant for nectar by insect pollinators. In the example of one of our local endangered species, the golden-cheeked warbler requires the bark of mature Ashe juniper trees in order to build nests.
The Bull Creek Nature Preserve contains five major types of habitat. Shrub habitat is dominated by low shrubs and small trees, such as evergreen sumac and shin oak. These small woody plants usually grow after a major disturbance such as a fire or clearing. This habitat can often be relatively short-lived, as it may eventually develop into mature woodlands.
Savannah, a common habitat in the Safari region of Africa, is a dry grassland that is interspersed with small groups of trees called mottes. Mottes in central Texas are often composed of live oaks, but can also include other tree species such as hackberry and persimmon.
Prairies, described by early settlers as ‘oceans of grass’, are grasslands composed mostly of native grasses and wildflowers. Prairies are often created and maintained by natural fires, which keep woody vegetation to a minimum. However, due to development and fire suppression practices, prairies in the preserve area have become smaller and more fragmented than in pre-settlement times.
Woodland habitats are dominated by tree species, which vary with topography and available water. Riparian woodlands grow close to water sources, such as creeks and rivers. Major species are largely deciduous and include pecan, willow, and sycamore. Mixed-evergreen woodlands are found in the uplands and often contain more drought-tolerant species such as Ashe juniper and live oak. This specific combination of juniper and oak species (known as oak-juniper woodlands) creates a habitat that is characteristic of the Balcones Canyonlands and vital for the golden-cheeked warbler.
The final type of habitat exists below ground in the caves within the limestone bedrock. Known as karst, these habitats are home to invertebrates that are specially adapted to living underground. Six of these invertebrates found within karst habitats of the Balcones Canyonlands Preserve are listed as endangered species.