Olfaction and brain size in the bowhead whale (Balaena mysticetus)

Although there are several isolated references to the olfactory anatomy of mysticetes, it is usually thought that olfaction is rudimentary in this group. We investigated the olfactory anatomy of bowhead whales and found that these whales have a cribriform plate and small, but histologically complex olfactory bulb. The olfactory bulb makes up approximately 0.13% of brain weight, unlike odontocetes where this structure is absent. We also determined that 51% of olfactory receptor genes were intact, unlike odontocetes, where this number is less than 25%. This suggests that bowheads have a sense of smell, and we speculate that they may use this to find aggregations of krill on which they feed.