Brown bears communicate with other individuals using marking behavior. Bipedal back
rubbing has been identified as a common marking posture. Oily substances are secreted via
enlarged sebaceous glands in the back skin of male bears during the breeding season.
However, whether apocrine gland secretions are associated with seasonal changes remains
unknown. The present study aimed to identify histological and histochemical changes in the
secretory status and the glycocomposition of the apocrine glands in the back skin of male
bears in response to changes in seasons and/or reproductive status. The apocrine glands of
intact males during the breeding season were significantly larger and more active than
those of castrated males during the breeding season and those of intact males during the
non-breeding season. Lectin histochemical analyses revealed a more intense reaction to
Vicia villosa agglutinin (VVA) in the cytoplasm, mainly Golgi zones of
apocrine cells during the breeding season among castrated, compared with intact males.
Positive staining for VVA was quite intense and weak in intact males during the
non-breeding and breeding seasons, respectively. Ultrastructural analysis revealed VVA
positivity in the Golgi zone, especially around secretory granules in apocrine cells.
Changes in lectin binding might reflect a change in the secretory system in the apocrine
cells. The present histological and histochemical findings of changes in the secretory
status and glycocomposition of the apocrine glands according to the season and
reproductive status suggest that these glands are important for chemical
communication.