Matthew Clarke and Ng, in 2006, used Ng's welfare biology framework to analyse the costs, benefits and welfare implications of the culling of kangaroos—classified as affective sentients—in Puckapunyal, Australia. They concluded that while their discussion "may give some support to the culling of kangaroos or other animals in certain circumstances, a more preventive measure may be superior to the resort to culling".[2] In the same year, Thomas Eichner and Rüdiger Pethi analyzed Ng's model, raising concern regarding a lack of appropriate determinants of the welfare of organisms because of the infancy of welfare biology.[3]