Arousal from hibernation increases blood oxygen saturation in 13-lined ground squirrels

Fig. 1.. Physiological metrics that change throughout hibernation in 13-lined ground squirrels (Ictidomys tridecemlineatus). (A) Body temperature (Tb) in a 13-lined ground squirrel during hibernation. (B) Heart rate (fH; red dashed line) and Tb (solid black line) fluctuations during an arousal; adapted from MacCannell et al. (2018), with permission. (C) Comparison of cardiac output (from Popovic, 1964), breathing frequency (from Sprenger and Milsom, 2022) and whole-animal oxygen consumption (from Muleme et al., 2006) between torpor and interbout euthermia (IBE). Data are means±s.e.m.

Fig. 2.. Increases in fH and oxygen saturation during arousal. (A,B) Increase in fH (A) and carotid artery haemoglobin (Hb) oxygen saturation (SaO2; B) with increasing Tb. (C) Change in SaO2 with increasing fH during arousal. Symbols represent mean and shading represents s.e.m., n=9 for each 1°C Tb increase. The red (A) and teal (B) lines represent mean summer fH and SaO2, respectively, n=5, with shading representing s.e.m. Solid black lines represent the relationships of fH and SaO2 with Tb, with dashed lines representing the 95% confidence interval, non-linear regression.

Fig. 3.. Comparisons between torpid and summer haematological values. (A) Heart mass, (B) heart mass relative to body mass, (C) body mass, (D) haematocrit (Hct, as percentage packed cell volume, PCV) and concentrations of (E) haemoglobin (Hb), (F) sodium, (G) potassium, (H) calcium and (I) glucose in venous whole blood. Means±s.e.m. Asterisks indicate a significant difference, *P<0.05, ****P<0.0001, two-tailed t-tests.