Influence of apex predators

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This week’s featured research article has just been published in Ecosystems and examines the trophic cascade between an apex predator, mammalian herbivore and grasses in a desert ecosystem in Australia. The researchers’ state there has long been debate regarding the primacy of bottom-up and top-down effects as factors shaping ecosystems. To inform this debate, the researchers measured activity/abundances of dingoes, red kangaroos and grasses, and diet of dingoes, in landscapes where dingoes were culled or not culled over three years. Dingo activity was correlated with rainfall, and their tracks were less frequent at culled sites. Kangaroo abundance was greater at sites where dingoes were culled and increased with rainfall in the previous six months. Grass cover was greater at sites where dingoes were not culled and increased with rainfall in the previous three months. During a period of average rainfall, dingoes primarily consumed rodents and increased their consumption of kangaroos during a period of drier conditions. The results are consistent with the hypothesis that suppression of an apex predator triggers a trophic cascade, but are at odds with the prediction that the magnitude of trophic cascades should increase with primary productivity. The researchers state that the study demonstrates that temporal fluctuations in primary productivity can have effects on biomasses of plants and consumers which are in many ways analogous to those observed along spatial gradients of primary productivity. The paper can be downloaded here.