Many diurnal animals, including us humans, lack a tapetum lucidum because we do not "need" to be able to see in the dark. Such other species include haplorhine primates (e.g. marmosets, tamarins, spider monkeys, gibbons, and great apes), squirrels, red kangaroos, and pigs. However, humans may exhibit a weak reflection from the fundus, as seen with the red-eye effect associated with flash photography.