The sperm whale (Physeter macrocephalus, Linnaeus 1758) possesses the largest brain that ever existed. Relatively few authors have dealt with it and the available descriptions are heterogeneous, with only few data about brain weight or gross anatomy. In fact the central nervous system of large cetaceans is quite difficult to obtain, given the huge body size and the low frequency of strandings of recently dead individuals. Furthermore, since the skull of the sperm whale underwent an extreme transformation for the accommodation of the spermaceti organ, the cranial cavity is surrounded by thick layers of bone and thus difficult to reach under field conditions. We recently had the chance to extract the brain from two stranded sperm whales whose bodies were in good condition. In the present note we describe the main macroscopic characteristics of the sperm whale brain, including its weight and Encephalization Quotient, review the available literature, and describe a possible new approach to the removal and preservation of the organ under field conditions.

We investigated the relationship between age and body length, and age at sexual maturity of Physeter macrocephalus individuals stranded along the Italian coast. Our molecular analysis shows that all our samples belong to the C.001.002 haplotype, shared between Atlantic and Mediterranean populations. We show that males attain sexual maturity at 10 years, similar to those from other marine areas. However, considering the same body length class, Mediterranean males are older than Atlantic ones. Our finding of a Mediterranean pregnant female of only 6.5 m in length and an assessed age of 24–26 years is particularly noteworthy, considering that females reach sexual maturity at about 9 years and 9 m of total length in other regions. Comparing our results with the literature data, we highlight the positive correlation between lifespan, adult body length and weight of males from the Mediterranean and Atlantic Ocean. Regardless of whether the relatively small size of Mediterranean specimens is a consequence of an inbreeding depression or an adaptation to less favorable trophic conditions, we recommend to closely monitor this population from a conservation perspective. In fact, its low genetic diversity likely corresponds to a relatively limited ability to respond to environmental changes compared with other populations.