Behavioral biologists at the University of Vienna have for the first time investigated the influence of climatic conditions such as sunshine in relation to the time of the first birth of Japanese macaques.
"On the sunny side of (new) life: Effect of sunshine duration on age at first reproduction in Japanese macaques (Macaca fuscata)": Lena S. Pflüger, Katharina E. Pink, Anja Böck, Michael A. Huffman, Bernard Wallner, American Journal of Primatology.