Heavy livestock grazing negatively impacts a marsupial ecosystem engineer

Human activities modulate reciprocal effects of a subterranean ecological engineer rodent, Tachyoryctes macrocephalus, on Afroalpine vegetation cover

Human activities, directly and indirectly, impact ecological engineering activities of subterranean rodents. As engineering activities of burrowing rodents are affected by, and reciprocally affect vegetation cover via feeding, burrowing and mound building, human influence such as settlements and livestock grazing, could have cascading effects on biodiversity and ecosystem processes such as bioturbation. However, there is limited understanding of the relationship between human activities and burrowing rodents. The aim of this study was therefore to understand how human activities influence the ecological engineering activity of the giant root-rat (Tachyoryctes macrocephalus), a subterranean rodent species endemic to the Afroalpine ecosystem of the Bale Mountains of Ethiopia. We collected data on human impact, burrowing activity and vegetation during February and March of 2021. Using path analysis, we tested (1) direct effects of human settlement on the patterns of livestock grazing intensity, (2) direct and indirect impacts of humans and livestock grazing intensity on the root-rat burrow density and (3) whether human settlement and livestock grazing influence the effects of giant root-rat burrow density on vegetation and vice versa. We found lower levels of livestock grazing intensity further from human settlement than in its proximity. We also found a significantly increased giant root-rat burrow density with increasing livestock grazing intensity. Seasonal settlement and livestock grazing intensity had an indirect negative and positive effect on giant root-rat burrow density, respectively, both via vegetation cover. Analysing the reciprocal effects of giant root-rat on vegetation, we found a significantly decreased vegetation cover with increasing density of giant root-rat burrows, and indirectly with increasing livestock grazing intensity via giant root-rat burrow density. Our results demonstrate that giant root-rats play a synanthropic engineering role that affects vegetation structure and ecosystem processes.

Does reducing grazing pressure or predation conserve kowaris? A case study at Diamantina National Park

Livestock contributes to the decline of many species in Australia. However, they may have less impact in arid environments, where annual plant species dominate. Kowaris (Dasyuroides byrnei), a small carnivorous marsupial, living on Diamantina National Park were monitored to assess the success of ecosystem recovery following a reduction in cattle. Kowaris were found at 10 locations within the study area: five where they had been recorded prior to the area becoming a national park and five ‘new’ locations. No kowaris were found at one of the historical sites. The density was estimated to range from 1 to 2.5 kowaris per square kilometre from 2007 to 2009. The results suggest that the population likely increased following a reduction in grazing pressure. However, a boom in rodents and predators occurred during the study with a corresponding decline in kowari detections. Kowaris have not been detected at any of the study sites since 2012. These results suggest that management of top-down factors as well as bottom-up factors are required to conserve kowaris. The work further highlights the need for replicated, long-term studies if the interactions between complex ecological processes, at a landscape scale, are to be understood so that threatened species, like the kowari, can be managed effectively.