(negative masking). Even small amounts of environmental light change have shown to have an effect on the activity of mammals. An observational study done on the activity of nocturnal owl monkeys in the Gran Chaco in South America showed that increased amounts of moonlight at night increased their activity levels through the night which led to a decrease of daytime activity. Meaning that for this species, ambient moonlight is negatively correlated with diurnal activity. This is also connected with the foraging behaviours of the monkeys, as when there were nights of little to no moonlight, it affected the monkey's ability to forage efficiently, so they were forced to be more active in the day to find food. Other environmental influences Diurnality has shown to be an evolutionary trait in many animal species, with diurnality mostly reappearing in many lineages. Other environmental factors like ambient temperature, food availability, and predation risk can all influence whether an animal will evolve to be diurnal, or if their effects are strong enough, then mask over their circadian rhythm, changing their activity patterns to becoming diurnal. All three factors often involve one another, and animals need to be able to find a balance between them if they are to survive and thrive. Ambient temperature has been shown to affect and even convert nocturnal animals to diurnality as it is a way for them to conserve metabolic energy. Nocturnal animals are often energetically challenged due to being most active in the nighttime when ambient temperatures are lower than through the day, and so they lose a lot of energy in the form of body heat. According to the circadian thermos-energetics (CTE) hypothesis, animals that are expending more energy than they are taking in (through food and sleep) will be more active in the light cycle, meaning they will be more active in the day. This has been shown in studies done on small nocturnal mice in a laboratory setting. When they were placed under a combination of enough cold and hunger stress, they converted to diurnality through temporal niche switching, which was expected. Another similar study that involved energetically challenging small mammals showed that diurnality is most beneficial when the animal has a sheltered location to rest in, reducing heat loss. Both studies concluded that nocturnal mammals do change their activity patterns to be more diurnal when energetically stressed (due to heat loss and limited food