From a fellow transplanted Arizonian, Muse, who I simply do not read enough:

Animals take their cue from the weather, and enjoy the lull of the winter. During the summer, the desert is a study in brute survival, for every creature is the enemy of the others, and all must compete to live another long, hot night. Everything has talons and teeth, especially the plants. To live a full summer in the desert means to either be incredibly resilient or to be stronger than your enemy. During the winter, clumsy javelinas feel bold enough to leave their tracks and scat in common areas, and mice invade homes because most of the threatening lizards are hibernating. Summer lives from the blood of wildlife, whereas winter is a calmer time.