In Hoot, what was unusual about the cottonmouths on the construction site?

In Carl Hiaasen's novel Hoot, a Mother Paula's pancake house is under construction on a site where burrowing owls are living. Napolean Leep, also known as Mullet Fingers, invents many ways to try to stop the construction of the restaurant. He pulls up survey stakes, places alligators in portable toilets, spray paints a patrol car's windows, deflates the tires on construction equipment, and introduces snakes in order to scare the guard dogs. These snakes have an unusual feature not commonly found on snakes. 
In chapter 8, the construction foreman, Curley Branitt, hires a dog trainer to place Rottweilers as guard dogs on the construction site. The purpose of the dogs is to stop the vandals from further delaying construction. Kalo, the trainer, removes the dogs in chapter 9 because nine cottonmouth water moccasin snakes are found on the property, and Kalo is concerned for the dogs' safety. The snakes are poisonous, and the dogs are worth three thousand US dollars each. 
In chapter ten, Roy, the main character, finds out Mullet Fingers placed the snakes there. He put sparkles on all the snake's tails so he can collect them from the site once the dogs are gone. Mullet Fingers also taped each one of the snake's mouths shut because he didn't want to hurt the dogs. He only wanted to scare them. Mullet Fingers cares deeply about animal welfare. When Roy asks how someone could tape a snake's mouth shut, Beatrice answers, "very carefully."