Black or white? Physiological implications of roost colour and choice in a microbat. (August 2016)

• Record Type: Journal Article
• Authors: Doty, Anna C.; Stawski, Clare; Currie, Shannon E.; Geiser, Fritz
• Is Part Of: Journal of thermal biology. Volume 60(2016)
• Page Start: 162
• Page End: 170
• Publication Date: 2016-08
• Subjects: Tb Body Temperature -- Tskin Skin Temperature -- Ta Ambient Temperature -- Tbox Box Temperature -- DEE Daily Energy Expenditure -- TMR Torpor Metabolic Rate -- RMR Resting Metabolic Rate -- MR Metabolic Rate -- TBD Torpor Bout Duration; Thermobiology -- Periodicals; Temperature -- Periodicals; Biology -- Periodicals; Thermobiologie -- Périodiques; Thermobiology; Periodicals; 571.46
• DOI: 10.1016/j.jtherbio.2016.07.015
• Languages: English
• ISSNs: 0306-4565

Abstract

Abstract: Although roost choice in bats has been studied previously, little is known about how opposing roost colours affect the expression of torpor quantitatively. We quantified roost selection and thermoregulation in a captive Australian insectivorous bat, Nyctophilus gouldi (n=12) in winter when roosting in black and white coloured boxes using temperature-telemetry. We quantified how roost choice influences torpor expression when food was provided ad libitum or restricted in bats housed together in an outdoor aviary exposed to natural fluctuations of ambient temperature. Black box temperatures averaged 5.1 °C (maximum 7.5 °C) warmer than white boxes at their maximum daytime temperature. Bats fed ad libitum chose black boxes on most nights (92.9%) and on 100% of nights when food-restricted. All bats used torpor on all study days. However, bats fed ad libitum and roosting in black boxes used shorter torpor and spent more time normothermic/active at night than food-restricted bats and bats roosting in white boxes. Bats roosting in black boxes also rewarmed passively more often and to a higher skin temperature than those in white boxes. Our study suggests that N. gouldi fed ad libitum select warmer roosts in order to passively rewarm to a higher skin temperature and thus save energy required for active midday rewarming as well as to maintain a normothermic body temperature for longer periods at night. This study shows that colour should be considered when deploying bat boxes; black boxes are preferable for those bats that use passive rewarming, even in winter when food availability is reduced. Highlights: Bats prefer to roost in black boxes over white boxes in winter both when fed ad libitum and when food-restricted. Bats roosting in white boxes were torpid longer and reduced normothermic periods compared to bats roosting in black boxes. Food-restricted bats spent more time torpid and less time normothermic compared to bats fed ad libitum. Black roost boxes should be made available to tree-roosting bats in winter in areas where roosts are limited.