New year, new opossums? Comparing the diet and health related characteristics of <i>Didelphis virginiana</i> over four years

Abstract The Virginia opossum is an animal that plays important roles in ecosystems and is a popular model for ecological studies. However, they are short-lived (average lifespan of 1.1 years), and a question arises: can the data taken from those animals be extrapolated to other years or do their characteristics change as quickly as the members of a population? Therefore, the aim of this article is to compare several characteristics (age, weight, body condition, infestation by fleas, severity of injuries, leucocyte and erythrocyte counts, and isotopic niche) of an opossum population over four years. For this, we trapped opossums in the same location at the same time of year for four years. We found that most characteristics remained similar over the study period; however, there was a change in erythrocyte counts, and the isotopic niche changed every year. A positive correlation was found between the δ 15 N and body condition. This suggests that if left undisturbed, opossum populations maintain their characteristics; however, their diet changes according to food availability. Opossums that are higher in the trophic net (most likely because they consume more carrion) tend to have a higher body condition.