Body mass condition in greek tortoises: Regional and interspecific variation

Body mass and length data from large samples of wild Testudo graeca, T. hermanni and T. marginata in Greece were used to assess body mass condition. Mass-length relationships differed significantly between the sexes (females being heavier) and among the species (T. marginata being least heavy). Mass-length relationships for each species and sex were used to calculate the condition index (CI) log (M/M?), where M is observed mass and M? is mass predicted from length, which is equal to residuals from the regression of log M on log length. It was possible to use the empirical mass-length relationships from one population of T. hermanni to calculate CI in other populations of substantially different adult size. The seasonal pattern of the CI varied with latitude, with a sharper and later peak further north, and habitat, declining more in summer at a xeric coastal site. The seasonal patterns of CI in T. graeca and T. marginata were similar, with sharper and later peaks compared to T. hermanni. These seasonal patterns of CI were related to differences in activity and food availability among species and sites. The variability of the CI was similar in all three species, with most values between -0.1 and +0.1; seasonal variation was of relatively low amplitude, with a range of about 0.05 between the highest and lowest monthly means.