Biochemical, hematological and morphometric assessment of free-ranging Galapagos fur seal (Arctocephalus galapagoensis) pups

The endangered Galapagos fur seal (GFS, Arctocephalus galapagoensis) was hunted for its fur to the brink of extinction in the early 20th century. Although populations have recovered following the introduction of protection laws, a combination of natural and anthropogenic risks continues to threaten this species. Data on the health status of individuals can provide valuable information for assessing conservation status. Despite this, reference ranges are scarce for many otariid species, including the GFS, due to challenges in accessing rookeries and sampling free-ranging animals. We determined the biochemical, hematological, and morphometric values of apparently healthy GFS pups (n = 59) captured across the nine major breeding rookeries throughout the Galapagos archipelago in March 2024. Twelve blood parameters were analyzed, and none of them were statistically different between sexes (p > 0.05). Alanine aminotransferase, amylase, albumin, globulin, total protein, blood urea nitrogen, creatinine, phosphate, sodium, glucose and hematocrit were within the normal range reported in other otariids species, which confirms their apparently good health status. All individuals exhibited an apparently stable body condition based on physical examination, and no abnormalities were detected in the differential leukocyte count. However, pups with poor body condition exhibited lower lymphocyte counts (r_s > 0.5), which could have implications for survival. Our results represent an initial step toward establishing a baseline of health biomarkers for GFS, which contributes to expanding knowledge about this endangered endemic species and will serve as a reference for future health assessments in the coming years.