Texas Parks and Wildlife Department's website says pets must be on a leash no longer than 6 feet while on the trail, and should be kept away from swimming facilities, park buildings and restaurants (guide dogs are an exception). Pets may be kept in vehicles or proper cages. Owners need to collect pet waste and dispose of it properly.
Big Bend National Park's website says: Dogs are not allowed on trails or anywhere in the backcountry because of their interference with wildlife and because they may threaten other hikers. Dogs are allowed anywhere vehicles can go, such as roads and primitive roadside campsites. They must be on a leash or otherwise restrained at all times. They may NOT be left unattended in a campsite. We recommend that visitors also not leave their pets unattended in vehicles because of the extreme heat."
Guadalupe Mountain National Park's website says:
Pets are welcome in Guadalupe Mountains National Park, but please consider that bringing your pet to the park could limit your activities, especially hiking and backpacking, because pets are not allowed on most park trails or in the backcountry. In addition, many plants are spiny or poisonous, and many desert animals could pose a threat to your pet.
- Pets are permitted in developed areas (parking lots, campgrounds, and roadways, but not inside buildings).
- Pets must be under your physical control at all times. Please keep your pet leashed for their safety, as well as the safety of park wildlife.
- Pets may walk with you (on leash) on the short trail between the campground and the Headquarters Visitor Center, or along the Pinery Trail from the visitor center to the Butterfield Station, but pets are not allowed along any of the other park trails or in the backcountry, because they may disturb park wildlife or be harmed themselves by wild animals. There are many rattlesnakes in the park, and park wildlife may carry plague or rabies. Do not allow your pet near animals or their dens or burrows.
- Do not leave pets unattended at campsites or in vehicles; heat kills quickly, and pets are especially vulnerable to predators if left alone. The nearest kennel service (with limited hours) is at Carlsbad Caverns National Park.
- Please clean up after your pet.