Mortality of mule deer fawns in a natural gas development area


Recent natural gas development has caused concern among wildlife managers, researchers, and stakeholders over the potential effects on wildlife and their habitats. Specifically, understanding how this development and other factors influence mule deer (Odocoileus hemionus) fawn (i.e., 0–6 months old) mortality rates, recruitment, and subsequently population dynamics have been identified as knowledge gaps. Thus, we tested predictions concerning the relationship between natural gas development, adult female, fawn birth, and temporal (weather) characteristics on fawn mortality in the Piceance Basin of northwestern Colorado, USA, from 2012–2014. We captured and radio‐collared 184 fawns and estimated apparent cause‐specific mortality in areas with relatively high or low levels of natural gas development using a multi‐state model. Mean daily predation probability was similar in the high versus low development areas. Predation was the leading cause of fawn mortality in both areas and decreased from 0–14 days old. Black bear (Ursus americanus; 22% of all mortalities, n = 17) and cougar (Felis concolor; 36% of all mortalities, n = 6) predation was the leading cause of mortality in the high and low development areas, respectively. Predation of fawns was negatively correlated with the distance from a female’s core area to a producing well pad on winter or summer range. Contrary to expectations, predation of fawns was positively correlated with rump fat thickness of adult females. Well pad densities and development activity were relatively low during our study, indicating that the observed intensity of development did not appear to influence daily predation probability. Our results suggest maintaining development activity thresholds at levels we observed to potentially minimize the effects of development on fawn mortality. However, we caution that higher development intensity and drilling activity in flatter, less rugged areas with less concealment cover could influence fawn mortality. Managers should maintain low development densities in areas where topography and vegetation offer less concealment. Overall, region‐specific data (e.g., development intensity, topography, predator assemblages, and associated predation risk) are needed to better understand the effects of natural gas development on fawn mortality.

Journal of Wildlife Management: 82