Leukocyte Profiles in Breeding Female and Pup Southern Elephant Seals (Mirounga leonina) in Relation to Lactation and Body Condition

This study analyzed blood smears from southern elephant seal (Mirounga leonina) adult females and pups. White blood cell profiles (total WBC count (WBC/104RBC) and the relative percentages (%) of neutrophiles, lymphocytes, monocytes, eosinophils, and basophils, as well as the neutrophil-to-lymphocyte ratio (N/L ratio)) were compared between pups and adult females, according to sex and lactation phase (beginning and end of lactation). Additionally, relationships between WBC variables and body condition were examined, as well as those between maternal WBC variables and their pups’ body condition. Adult females had more neutrophils and higher N/L ratios, but fewer lymphocytes, compared to pups. Between the beginning and the end of lactation, WBC total count increased in adult females. In females at end of lactation, lymphocytes increased with body condition while neutrophils decreased. No relationships were found between pups’ WBC variables and their body condition, or between maternal WBC variables and their pups’ body condition. In pups, no differences were seen between male and female in WBC variables. This study provides valuable insight into the immune compartment of this species. More studies are needed to improve our understanding of the physiology of southern elephant seals and its potential fitness consequences.