A new AZ resident from the Northwest was concerned about bears, snakes, bugs and water while hiking/backpacking in Arizona. Below is my reply to him. Originally posted on Meetup.com
You ask some interesting questions. I"ll answer in the order of the questions. First the bears. While it's very unlikely to see bears in the desert, it's not completely out of the realm of possibility. Especially in the winter. There are bears in the mountains around Tucson and in lean years have been known to wander down into the high desert. My point, while highly unlikely it would be unwise to completely write off the possibility of sighting bear in the high deserts around any large AZ mountains like Mt Lemon.
Preparation for insects is the same for snakes, look where you're putting your hands and feet before you put them there. I've lived/hiked in the desert for more than four decades and I'm always scanning ahead for the possibility of snakes and other issues. In reality scorpions are really only an issue putting your hands into thick brush and rock crevices without checking first. Extremely rare but possible, both have been known to wind up in sleeping bags when the weather is cool and sleeping bags are warm. If you're in a screened tent or screened bivy bag both are negated. Also, many people hike with trekking poles. Poles are handy to block/push thorny brush out of the way and it's better to put a pole over a rock or log before a foot or leg if you can't see what's there.
I personally don't recommend open toed sandals for hiking in the desert and its not because of insects. Very sharp rocks, cactus thorns, cat claw and just about a thousand other irritants for me make sandals a pain. I recommend lightweight breathable trail running shoes or hiking shoes (NO GORETEX). Closed toed sandals from Keen and some Teva models are the exception. It boils down to a personal preference and your tolerance for stopping and emptying your sandal of sand and pebbles.
In summer, carrying enough water for three days would weigh forty pounds or more (1.5 gallons per day min). Winter, less. Everybody in the desert (whole SW region for that matter) plans trips around water availability, with perhaps one night being a dry camp (carrying water for that night) and refilling the next day. Most of the water in AZ can be filtered with the exception of water downstream of mines (old or new). This water should always be considered contaminated with heavy metals mercury and/or cyanide and avoided at all costs except last resort emergencies. When planning trips keep in mind where the mines are.