African forest elephants are estimated to constitute up to one-third of the continent's elephant population but have been poorly studied because of the difficulty in observing them through the dense vegetation that makes up their habitat. Thermal imaging has facilitated observation of the species, leading to more information on their ecology, numbers, and behavior, including their interactions with elephants and other species. Scientists have learned more about how the elephants, who have poor night vision, negotiate their environment using only their hearing and olfactory senses. They also appeared to be much more active sexually during the night compared to the day, which was unexpected.