Table 1.

We collected data from 13 species of hibernating bats, including metabolic rate and evaporative water loss. Torpid metabolic rate (TMR) varied across temperatures (Temperature Effect column) and the range of temperatures at which the minimum torpid metabolic rate (TMR_min) was recorded varied among species. Within that range of temperatures, TMR_min did not vary among species, but species were divided into high evaporative water loss (EWL) and low EWL clusters (see Fig. 3). Values reported as mean ± standard error.

Species	n	Sites1	Body mass (g)	Range tested (°C)	Temperature effect2	TMRmin (mW g-1)	Range TMRmin (°C)	Tdefended 3 (°C)	EWL (mg H2O min-1 g-1)	EWL cluster
Vespertilionidae
Corynorhinus townsendii	152	BC1, CO, NV1, NV2, OR, UT	10.3 ± 0.1	2–10	LR3 = 13.0, p = 0.005	0.33 ± 0.03	5–8	2–5	0.009 ± 0.001	Low
Eptesicus fuscus	7	MT1	16.7 ± 1.2	2–10	LR3 = 1.6, p = 0.67	0.25 ± 0.07	2–10	< 2	0.009 ± 0.002	Low
Lasionycteris noctivagans	23	BC2	12.7 ± 0.2	0–8	LR4 = 15.6, p = 0.004	0.15 ± 0.01	2–8	0–2	0.005 ± 0.001	Low4
Myotis californicus	45	BC2	5.7 ± 0.1	0–10	LR5 = 22.0, p < 0.001	0.26 ± 0.02	2–8	0–2	0.010 ± 0.002	Low
Myotis ciliolabrum	23	MT1, NV2	5.0 ± 0.1	2–10	LR3 = 6.2, p = 0.10	0.26 ± 0.04	2–10	< 2	0.009 ± 0.001	Low
Myotis evotis	13	MT2	7.5 ± 0.2	2–10	LR3 = 16.7, p < 0.001	0.48 ± 0.09	5–10	2–5	0.019 ± 0.001	High
Myotis lucifugus	99	MT2, AB, NWT	8.9 ± 0.1	2–10	LR3 = 15.2, p = 0.002	0.30 ± 0.02	2–8	< 2	0.014 ± 0.001	High
Myotis thysanodes	11	MT2	9.4 ± 0.3	2–10	LR3 = 11.2, p = 0.011	0.25 ± 0.08	5–10	2–5	0.018 ± 0.001	High
Myotis velifer	33	OK	14.4 ± 0.3	2–10	LR3 = 8.0, p = 0.046	0.25 ± 0.04	5–10	2–5	0.015 ± 0.001	High
Myotis volans	12	MT1, MT2	9.0 ± 0.2	2–10	LR3 = 10.6, p = 0.014	0.43 ± 0.08	5–10	2–5	0.015 ± 0.001	High
Myotis yumanensis	27	BC2, BC3	5.8 ± 0.1	0–8	LR4 = 48.4, p < 0.001	0.20 ± 0.01	4–6	2–4	n/a5
Perimyotis subflavus	34	OK	7.0 ± 0.1	2–10	LR3 = 17.1, p < 0.001	0.18 ± 0.04	8–10	5–8	0.017 ± 0.002	High
Molossidae
Tadarida brasiliensis	27	TX	13.4 ± 0.4	2–12	LR4 = 63.2, p < 0.001	0.35 ± 0.06	8–12	5–8	0.010 ± 0.001	Low

¹Subscripts identify different sites in states or provinces with multiple sites.

²Effect of temperature on metabolic rate. LR = likelihood ratio with degrees of freedom indicated in subscript.

³Where metabolic rate did not increase at coldest temperature tested, T_defended can only be determined as less than the lowest temperature tested. Otherwise T_defended is between the range of temperatures indicated.

⁴L. noctivagans may represent a third cluster with lower EWL (see Fig. 3b), but to be conservative we present only two clusters here.

⁵EWL was not measured for Myotis yumanensis.