Microclimate in Hell's Canyon mines used by maternity colonies of Myotis yumanensis

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Temperature, relative humidity, and air flow were measured May–September in three mines used by Myotis yumanensis for maternity colonies and two similar but unused mines. Ambient temperatures differed little between mines with or without maternity colonies, but relative humidity was much higher and fluctuated less in mines with maternity colonies than in mines without maternity colonies. Air flow was insignificant in all mines. Bats clustered in small ceiling domes. Large colonies of 500–750 adults in two of the mines raised temperatures at roost sites to >30 °C, but roost-site temperatures of a small colony of only 50–60 individuals in the third mine rarely exceeded 25 °C. Although topography of ceilings allowing capture of exogenous metabolic heat may be important for producing temperatures conducive to rapid growth of juveniles and reduced thermoregulatory costs, bats may have selected these three mines on the basis of higher humidity or lower levels of disturbance by humans than occur in mines without maternity colonies. Alternative maternity roosts seem limited in Hell's Canyon, and future additional protection of these three colonies may be important for the continued presence of this species in the canyon.

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ELECTRONIC FILE - Zoology: Mammals

Citation: Betts, B. J. 1997. Microclimate in Hell's Canyon mines used by maternity colonies of Myotis yumanensis. Journal of Mammalogy 78(4): 1240–1250.