Application of bivariate regression method for estimating the secondary natality in brown hare

Abstract

Knowledge of reproductive performance of the European brown hare (Lepus europaeus, Pallas, 1778) is an essential condition for planning rational utilization. The direct possibility of estimating the number of leverets is the placental scar counting of the eviscerated females in the hunting bag. A condition for a reliable estimate is a sufficient sample quantity and the timing of sampling. Late sampling leads to a risky and unreliable estimate due to the disappearance of placental scars (amount of reproduction), which will result in under- or over-utilization. The goal of study is to test a method that enables reliable estimation for the amount of reproduction by using individual biological parameters and eliminates the risk resulting from timing. This case report is an attempt to estimate the number of placental scars (born leverets) by using the dried eye lens weight and body weight of fertile females by bivariate linear regression method. Based on the real placental scar number (y), three classes were created: class I: y=1-4; class II: y=5-9; class III: y=9-13 placental scares. The estimated values of the placental scar numbers (y’) using the regression model was only accurate for values belonging to class II. For those belonging to class I the model resulted over-, and to class III an underestimation. The linear regression model using eye lens weight and body weight as independent variables did not result in a reliable estimate of secondary natality for the entire stock in the given situation.