Primary roosts used by Indiana bats are typically snags in canopy gaps and forest edges that receive direct sunlight throughout the day. Alternate roosts are live or dead trees, generally located in the forest interior, that usually receive little or no direct sunlight. Weather, such as very warm temperatures and precipitation, appears to influence the use of interior alternate roost trees over primary roosts, as alternate roosts generally offer more shade and protection during inclement weather and extreme heat. However, this preference may fluctuate from season to season. Indiana bats moved to the alternate roost during periods of heavy rain and colder ambient temperatures during fall in Missouri, but chose to roost in the primary snag during inclement weather in the spring. These differences may be attributed to variation in the heat-retention capabilities of the trees at different times of the year. Bats from a maternity colony switched roosts more frequently in summer and autumn than they did in spring in an oak-pine forest in Kentucky. They exhibit strong fidelity to individual roost trees from year to year if they are still suitable roost sites. Many trees are no longer usable after just a few years, while others may last as long as 20 years.