Hind paw of a fisher (Pekania pennanti)

Fishers have plantar glands within whorls of hair on their hind paws that emit a distinctive odour.(1)(2)(3)(4) They appear as small dark circular patches on the large segmented centre pad (known as the metacarpal pad).
The plantar glands of pregnant female fishers enlarge to >10mm during January through May, and reduce in size (<10 mm) during June after giving birth. On males, the glands increase in size from <15 mm in December to >30mm in May. Reduction of the gland size is complete by June. Because these glands enlarge near and during mating season, it is hypothesised they serve the purpose of creating a trail of scent for fishers to locate each other for mating.(3)
Most marten species also have visible patches on their hind paws that are associated with plantar glands.
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