What triggers sex is a complex question that becomes almost a ‘mission impossible’ when it refers to wildlife.
Brown bears are particularly elusive animals and their copulas are very rarely observed in the wild. As a result, we still know very little about their mating behavior and the factors influencing it. To fill this gap, an international team of 13 scientists led by Alberto García-Rodríguez from the Institute of Nature Conservation PAS in Krakow has compiled information about brown bear copulas in the field from 36 study areas across the entire distribution of the species, which inhabits large areas of Europe, North America and Asia. They were particularly interested in the starting dates of sexual activity in bears and how long it lasted.
Brown bears have a peak of sexual activity during May-June, but can also copulate out of the typical mating season, i.e. in autumn and as late as November. Researchers found that the number of daylight hours, i.e. the photoperiod, is the main factor determining the start of the mating season, and this happened when the photoperiod is 14-18 hours. Bears from southern areas started mating at earlier dates, supporting that geographical variables trigger the start of copulations in brown bears, a usual pattern across different mammal species.
For more information, please read: https://www.tandfonline.com/doi/full/10.1080/24750263.2020.1801866