Influence of multiple predators decreases body condition and fecundity of European hares

We assessed the hypothesised negative correlation between the influence of multiple predators and body condition and fecundity of the European hare, from 13 areas in the Netherlands. Year-round abundance of predators was estimated by hunters. We quantified predator influence as the sum of their field metabolic rates, as this sum reflects the daily food requirements of multiple individuals. We determined the ratio between body mass and hindfoot length of hares as an index of body condition, and the weight of their adrenal gland as a measure of chronic exposure to stress, and we counted the number of placental scars to estimate the fecundity of hares. As hypothesised, we found that the sum of field metabolic rate of predators was negatively correlated with body condition and the number of placental scars, whereas it was positively related to the weight of the adrenal glands. In contrast to the sum of the field metabolic rate, the total number of predators did not affect the investigated risk responses. The sum of the field metabolic rate can be a useful proxy for the influence of multiple predators and takes into account predator abundance, type, body weight, and food requirements of multiple predators. With our findings, our paper contributes to a better understanding of the risk effects of multiple predators on prey fitness. Additionally, we identify a potential contributor to the decline of European hare populations.