Allometric scaling relationships for tortoises (T), mammalian nonruminants (NR) and ruminants (R) for daily methane production with body mass (M) according to the equation y = a Mb.

DM dry matter, GE gross energy, DE digestible energy, dNDF digestible neutral detergent fibre, I intake tortoise data from this study; ruminant data collection from Franz et al. [25], nonruminant data collection from Franz et al. [26].*sample sizes vary between measurements because for tortoises, not all measurements could be performed due to logistic reasons, and because for mammals, data available from the literature varied between sources.