Identification of the baculum in American pika (Ochotona princeps: Lagomorpha) from southwestern Alberta, Canada

We discovered hard structures that resembled bone in the penis of 20 specimens of male American pikas (Ochotona princeps) from the Rocky Mountains of southwestern Alberta, Canada. Histological sections of these structures showed features consistent with cortical bone and osteocytes, and scanning electron microscopy analyses indicated peaks in calcium and phosphorous. The anatomical positioning, internal texture, and elemental composition indicate that the structures are bacula. The presence of a baculum in O. princeps demonstrates that there is a greater phylogenetic distribution of this feature among Mammalia than commonly recognized, and it indicates that the absence of a baculum is not a derived character state for Lagomorpha.