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Providing evidence to improve practice

Individual study: Modified cave entrances: thermal effect on body mass and resulting decline of endangered indiana bats (Myotis sodalis)

Published source details

Richter A.R., Humphrey S.R., Cope J.B. & Brack V. (1993) Modified cave entrances: thermal effect on body mass and resulting decline of endangered indiana bats (Myotis sodalis). Conservation Biology, 7, 407-415


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Install and maintain cave gates to restrict public access Bat Conservation

A before-and-after and site comparison study in 1976–1991 in two caves in Indiana, USA (Richter et al 1993) found that Indiana bats Myotis sodalis hibernating within a cave modified with a stone wall and gate constructed at the entrance entered hibernation at a 5% higher body mass and lost 42% more body mass than bats in an unmodified cave 4 km away. The stone wall and gate in the modified cave restricted the cave opening by 62% reducing airflow and resulting in average winter temperatures 5°C higher than in the unmodified cave. In 1977, the stone wall was removed and replaced with steel bars. From 1977 to 1991, the population of Indiana bats in the cave increased from 2,000 to 13,000 bats. In each of two caves, temperatures were measured near to hibernation sites every other week, and bats were counted and weighed in early winter (October–November 1976) and late winter (March 1977). Bats were monitored with a biannual census from 1977 to 1991 (no other details reported).

(Summarised by Anna Berthinussen)