Managing Forest Disturbances: Effects on Mule Deer and Plant Communities in Montana’s Northern Forests

MS Theses, Teagan Hayes (2017-2020)

Mule deer (Odocoileus hemionus) are frequently the focus of population and habitat management in the western United States. Land and wildlife managers use disturbance to reset forests to earlier successional stages and improve the quality and quantity of forage available to mule deer. However, the effects of management practices on nutrition and selection vary widely, so the implementation of management practices raises ecological as well as management-related concerns. This work investigated how disturbance from wildfire, prescribed fire, and timber harvest influences the spatial and temporal distribution of nutritional resources in mule deer summer range, and therefore, how the nutritional landscape influences mule deer selection of disturbance. We studied changes in vegetation and habitat selection by mule deer in three areas with differing disturbance regimes during 2017–2019. We found differences in forage nutrition response to disturbance that was specific to study areas, suggesting that targeted forest management within disturbance regimes would provide nutritional benefits to mule deer populations in the northern Rocky Mountains. Other vegetative responses revealed trade-offs specific to forest and disturbance types. Despite substantial variation in selection among individuals and among study areas, we found some common effects of forage nutrition and disturbance type on selection at population scales. As we predicted, deer selection within home ranges was not explained well within these constraints, suggesting that deer selection may be influenced more by other factors, such as security or cover within home ranges. The age and type of disturbance also influence selection at a population scale, but do not predict selection within home ranges, where the availability of disturbances is irregular. In all study areas, we documented similar selection for more recent disturbance and avoidance of open woodland at the population scale, suggesting that these responses can be generalized to deer in other populations in the Rocky Mountains because we observed them in multiple sites under widely differing conditions. Managers accounting for local and regional frequency and availability of disturbance can identify management actions that are accessible and beneficial for mule deer. Furthermore, consideration of the likely outcomes of forest-specific vegetative responses can help managers balance potential tradeoffs of management alternatives.