Hummingbirds have one of the highest metabolisms of any animal. This requires them to consume a tremendous amount of food to stay alive. They keep from starving to death each night by going into torpor, a state where their heart rate slows, breathing slows, and and their body temperature drops. It can take a hummingbird as much as 45 minutes to come out of torpor, making them very vulnerable to predators. Torpor will vary with the availability of food. A hummingbird that has enough food will not go into torpor at night, meaning it is much more likely to avoid night time predators.