transitions between diurnality and nocturnality occurred several times within primate lineages, with switching to diurnality being the most common transitions. Still today, diurnality seems to be reappearing in many lineages of other animals, including small rodent mammals like the Nile grass rat and golden mantle squirrel and reptiles. More specifically, geckos, which were thought to be naturally nocturnal have shown many transitions to diurnality, with about 430 species of geckos now showing diurnal activity. With so many diurnal species recorded, comparative analysis studies using newer lineages of gecko species have been done to study the evolution of diurnality. With about 20 transitions counted for the gecko lineages, it shows the significance of diurnality. Strong environmental influences like climate change, predation risk, and competition for resources are all contributing factors. Using the example of geckos, it is thought that species like Mediodactylus amictopholis that live at higher altitudes have switched to diurnality to help gain more heat through the day, and therefore conserve more energy, especially when colder seasonal temperatures hit. Light Light is one of the most defining environmental factors that determines an animal's activity pattern. Photoperiod or a light dark cycle is determined by the geographical location, with day time being associated with much ambient light, and night time being associated with little ambient light. Light is one of the strongest influences of the suprachiasmatic nucleus (SCN) which is part of the hypothalamus in the brain that controls the circadian rhythm in most animals. This is what determines whether an animal is diurnal or not. The SCN uses visual information like light to start a cascade of hormones that are released and work on many physiological and behavioural functions. Light can produce powerful masking effects on an animal's circadian rhythm, meaning that it can "mask" or influence the internal clock, changing the activity patterns of an animal, either temporarily or over the long term if exposed to enough light over a long period of time. Masking can be referred to either as positive masking or negative masking, with it either increasing an diurnal animals activity or decreasing a nocturnal animal's activity, respectively. This can be depicted when exposing different types of rodents to the same photoperiods. When a diurnal Nile grass rat and nocturnal mouse are exposed to the same photoperiod and light intensity, increased activity occurred within the grass rat (positive masking), and decreased activity within the mouse