Limited physiological measurements exist for the digestive physiology of porcupines. We measured CH₄ emission in three captive Indian crested porcupines (Hystrix indica; 16.1 ± 2.7 kg) fed a diet of pelleted lucerne, and measured feed intake, digestibility, and digesta mean retention time (MRT) of a solute and three particle markers (<2, 10 and 20 mm). Marker excretion patterns suggested secondary peaks indicative of caecotrophy, with MRTs of 26.4 h for the solute and 31.5, 26.8 and 26.2 h for the three particle markers, respectively. At a dry matter intake of 58 ±10 g/kg body mass^0.75/day, porcupines digested 49 and 35% organic matter and neutral detergent fibre, respectively, which is in the lower range of that expected for horses on a similar diet. The respiratory quotient (CO₂/O₂) was 0.91, the resting metabolic rate 274 kJ/kg body mass^0.75/day, and CH4 emissions averaged at 8.16 l/day and 17.9 l/kg dry matter intake. Accordingly, CH₄ yield was so high that it resembled that of a hypothetical ruminant of this body mass. The results are in accord with general understanding of hystricomorph rodent digestive physiology, and support recent findings that CH₄ production may be more prominent in rodents than previously thought.