Abstract

Around 80–90 elephant seal pups and weaners are rehabilitated at The Marine Mammal Center annually. Of those animals, several present with unusual lumbar spine conformations that are presumed to be abnormal but the presence of clinical signs that may be attributed to spinal disease is variable. Others have lumbar spine 'abnormalities' identified during radiography of the abdomen or pelvis/hind flippers without any evidence of spinal disease.Normal northern elephant seal spinal anatomy is neither well understood nor characterized in the literature making normal comparisons difficult.

This 25 year retrospective study reviewed lumbar radiographs of northern elephant seal pups and weaners rehabilitated at The Marine Mammal Center (TMMC). Complete lumbar radiographic studies (lateral and DV views including the entire lumbar spine) were available for 40 patients, all classified as weaners. Radiographs were reviewed for vertebral number, evidence of vertebral displacement and evidence of pathology. Radiographs demonstrated that 10/40 (25%) of elephant seal vertebral columns contain six lumbar vertebrae while 30/40 (75%) have five lumbar vertebrae; 10/40 (25%) have displacement of one or more lumbar vertebrae; and 3/40 (7.5%) have end plate lysis consistent with diskospondylitis.

These radiographic findings serve as a first step towards characterizing normal elephant seal lumbar anatomy as well as common anomalies and pathologies.

Acknowledgements

The Marine Mammal Center stranding department, staff, and volunteers; Michigan State University College of Veterinary Medicine department of Radiology.