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The perineal glands of the porcupine, Erethizon dorsatum (L., 1758), are sexually dimorphic, paired pockets sprouting osmetrichial hairs. They lie between the anus and urethra, lateral to the midline, amid a sebaceous glandular expanse. In their active state, the glandular pockets secrete an amber substance with a terpenoid odor. When inactive, the glands produce no stain or odor. In males, activation of the glands is associated with fully descended testes. The glandular pockets yield a microbiota (“microflora”) in both their active and inactive states. We hypothesize that the active-state microflora transforms a sebaceous secretion into a pheromonally active product that is disseminated by anal dragging. The glandular microflora was characterized by gas chromatography of bacterial fatty acid methyl esters (GC-FAME) and polymerase chain reaction - denaturing gradient gel electrophoresis (PCR-DGGE) of 16S ribosomal RNA gene fragments of bacteria. PCR-DGGE results showed the resulting bacteria profiles were the same in both sexes, but differed between the active and inactive states. Active-state microfloras were dominated by members of the Actinobacteria and showed greater coefficients of similarity than inactive-state microfloras. The microflora of individual animals changed with time and with secretory state. We argue for a reproductive role for the activated perineal glands. [ABSTRACT FROM AUTHOR]