We found that SMA better describes the scaling relationship between body mass and body size than OLS regression whether we use the SMA slope from the reference population (2.642 ± 0.11 vs. 2.011 ± 0.088; z  = 4.54, P  <   0.001) or from the Kelly and Tawes (2013) data set (2.32 ± 0.088 vs. 2.011 ± 0.088; z  = 2.46, P  =   0.014). Using the SMA slope derived from the Kelly and Tawes (2013) data set (i.e., b SMA = 2.32) produced results that were very similar (sex: F  =   2.57, df = 1,171, P  =   0.111; diet: F  =   0.001, df = 1,171, P  =   0.980) to those using the slope from the reference population (i.e., b SMA = 2.642). This might not always be the case, however, and so we recommend that biologists use b SMA from our reference populations in their calculations of  in G. texensis or A. domesticus.