Fig. 9.

Fatty acid binding protein annual cycle and relationship to duration of torpor. Three isoforms of FABP4 (adipose-fatty acid binding protein^{2965,2700,2708}) were examined by sampling date and individual animal features. A: plot of FABP4²⁶⁹⁵ abundance vs. sampling date for each animal. B: plot of FABP4²⁶⁹⁵ abundance vs. length of previous torpor bout for all individuals. There was a limited but significant positive linear relationship between FABP4 abundance and duration of the animal's previous torpor bout in all three isoforms (no. 2695 shown, all three: 0.16 < r² < 0.24; P ≤ 0.0003). Duration = 0 for all homeothermic ground squirrels. A linear relationship was retained for a single FABP4 isoform in transition states considered alone (C: FT FABP4²⁷⁰⁰ and D: SpT FABP4²⁷⁰⁸).