Photo by @joelsartore | A female common marmoset named Liilu and her baby, Marshmallow, regard me with curiosity during a Photo Ark shoot at the University of Nebraska Omaha. Females of this species typically give birth to a set of non-identical twins, though triplets or single infants are not unheard of. Because nursing their young requires a tremendous amount of energy, marmosets have adapted to having offspring during times of the year when food is abundant—at either the end of the dry season or the end of the rainy season. To see more species featured in the Photo Ark, follow me @joelsartore. #PhotoArk