Protein metabolism and physical fitness are physiological determinants of body condition in Southern European carnivores
The physiological significance of biometric body condition indices (bBCI) is poorly understood. We hypothesized that bBCI are composite metrics of nutritional physiology, physical fitness and health. To test this hypothesis, we first compared the performance of eight bBCI, using 434 Southern European carnivores from six species as a model system; and then identified, by non-destructive methods, the hematology and serum biochemistry correlates of three selected bBCI. Fulton's K Index, Major Axis Regression Residuals and Scaled Mass Index were the only bBCI insensitive to the effect of sex and age. The most informative physiological parameters in explaining the variation of these bBCI were the albumin (Effect Size (ES) = − 1.66 to − 1.76), urea (ES = 1.61 to 1.85) and total bilirubin (ES = − 1.62 to − 1.79). Hemoglobin and globulins (positive) and cholesterol (negative) were moderately informative (0.9 <|ES|< 1.5). This study shows that most bBCI do not control for the effect of age and sex in Southern European carnivores. Our results support that bBCI are composite measures of physiologic processes, reflecting a positive gradient from protein-poor to protein-rich diets, accompanied by increased physical fitness. Biometric body condition indices allow the integration of ecologically relevant physiological aspects in an easily obtained metric. ; This work was supported by Junta de Comunidades de Castilla-La Mancha [Project PREG-05-23], Spanish Ministry of Science and Innovation and European Union-FEDER funds [Project CGL2009-10741]; Organismo Autónomo Parques Nacionales [Project OAPN352/2011]; Empreendimentos Eólicos do Vale do Minho S.A. and Associação para a Conservação do Habitat do Lobo Ibérico (ACHLI); Fundação para a Ciência e Tecnologia [grants SFRH/BPD/116596/2016 to N.S. and SFRH/BD/144087/2019 to M.N. and UID/BIA/50027/2019 to P.M.]; FCT/MCTES, through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020 [cE3c—UIDB/00329/2020]; Juan de la Cierva research contracts from Ministerio de Ciencia e Innovación, Funder Id: 10.13039/501100004837 from the Spanish Ministry of Economy, Industry and Competitiveness [FJCI-2015-24949 to F.D.R.]; and the European Union H2020 [Project H2020 VACDIVA 862874 to J.A.B.]. ; Peer reviewed
