There are a variety of Lizards, Horned Toads [Horned Toads are actually lizards], and Scorpion’s, that you will encounter during your Havasu Falls visit. I would venture to say everyone will see at least some of these during their visit. Lizard sightings are the most common. Often fleeting off at a distance. Or sunning themselves on a warm rock.
The warmer it is, the more active they are. Keep your tent zipped up unless you want one snuggling up to you for warmth.
Shake out your footwear before slipping them on.