Tranquilliser darts are only viable at very short distances as they are mainly fired from air rifles or CO2 powered rifles and the tranquilliser dart does not make an particularly aerodynamic or accurate delivery option. Most competent people familiar with their use would not attempt their use at a distance much greater than 50m. Whilst agreeing that the killing of the Lynx was unfortunate, perhaps the authorities who took the decision to kill the lynx felt that an opportunity once presented had to be taken and that the distance was too great to use the less lethal option. Sometimes the Hard option is the one that has to be taken and I am sure the decision to use lethal force in this instance was not taken lightly
So if it couldn't be taken down by a tranquiliser, why was it shot at all, when it posed NO risk to humans [see above]?