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30Although dark coat color in dogs has been theorized as a risk factor for thermal stress, 31 there is little evidence in the scientific literature to support that position. We utilized 16 non-32 conditioned Labradors (8 black and 8 yellow) in a three-phase test to examine effects of coat 33 color on thermal status of the dog. Rectal, gastrointestinal (GI), surface temperature, and 34 respiration rate measured in breaths per minute (bpm), were collected prior to (Baseline -phase 35 1) and immediately after a controlled 30-minute walk in an open-air environment on a sunny day 36 (Sunlight -phase 2). Follow up measurements were taken 15 minutes after walking (Cool 37 down -phase 3) to determine post-exposure return to baseline. No effect of coat color was 38 measured for rectal, gastrointestinal or surface temperature, or respiration (P > 0.05) in dogs 39 following their 30-minute walk. Temperatures increased similarly across both coat colors (rectal 40 1.88 • C and 1.83 • C; GI 1.89 • C and 1.94 • C; eye 1.89 • C and 1.94 • C; abdominal 2.93 • C and 41 2.35 • C) for black and yellow dogs respectively during the sunlight phase (P > 0.05). All 42 temperatures and respiration rates decreased similarly across coat colors for rectal (0.9 • C and 1.0 43 • C) and GI (1.5 • C and 1.3 • C) for black and yellow dogs respectively (P>0.05). Similarly, sex did 44 not impact thermal status across rectal, gastrointestinal or surface temperature or respiration rates 45 measured (P > 0.05). These data contradict the commonly held theory that dogs with darker coat 46 color may experience a greater thermal change when exposed to direct sunlight compared to 47 dogs with a lighter coat color.48 49

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