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.