Blood parameters in natural populations of Trichosurus species (Marsupialia : Phalangeridae) II. Influence of habitat and population strategies of T. caninus and T. vulpecula

Abstract

Body weight and six blood parameters were determined in T. caninus and T. vulpecula from their preferred and peripheral habitats. Habitat had a large effect on T. caninus. Of the seven parameters measured, six (body weight, red blood cell count, haemoglobin concentration, haematocrit and plasma protein and lipid concentrations) were higher in the population from the peripheral habitat than in that from the preferred habitat. Only body weight was different in T. vulpecula, being higher in the peripheral than in the preferred habitat population. There were differences between T. caninus and T. vulpecula in four of the measured parameters (body weight, haematocrit, haemoglobin concentration and red blood cell count) irrespective of habitat, whereas plasma lipid concentration was the same in T. caninus from peripheral habitat and T. vulpecula, but differed in T. caninus between habitats. Four parameters showed significant seasonal variation in preferred-habitat T. caninus, three in peripheral-habitat T. caninus and one in T. vulpecula. However, the pattern of seasonal change in peripheral-habitat T. caninus was more similar to that in T. vulpecula than to that in preferred-habitat T. caninus, suggesting a physiological shift in peripheral-habitat T. caninus towards that of the more r-selected T. vulpecula. No differences were found between resident and dispersing T. caninus. T. caninus which had lost a pouch young and failed to maintain another in the same year had lower haematocrit and plasma lipid concentration than females in other reproductive states. It is suggested that the measurement of physiological responsiveness of populations may aid the understanding of adaptive strategies.