Ecology: Gas development disrupts deer from green wave surfing

The migration of mule deer in the USA is substantially disrupted by the expansion of gas field developments, according to a study published in Nature Ecology & Evolution. Industrial infrastructure has created an obstruction along their seasonal migration routes, causing the deer to slow and miss the peak time in which food is available, which may influence their survival and reproduction.

Animals may embark on long-distance migrations to exploit seasonal food sources. Species such as mule deer (Odocoileus hemionus) in the western USA closely track the emergence of the youngest, most nutritious plants along a well-defined migration corridor — a behaviour known as ‘green wave surfing’. However, the extent to which these historic migration routes may be disrupted in human-modified landscapes is unclear.

Ellen Aikens and colleagues analyse movement data collected over 14 years (2005 to 2018) from 120 mule deer fitted with GPS collars in south-central Wyoming, USA, during their spring migration. Over this time period, a coalbed natural gas development that intersects the migration corridors expanded, increasing the number and density of extraction wells and roads along the route. The authors find that in the early stages of industrial development, deer were able to maintain synchrony with the green wave of plant growth. However, as the development expanded, the two phenomena became increasingly decoupled, with deer lagging on average 8 to 22 days behind the green wave. This decoupling is primarily driven by deer pausing their migration within a kilometre short of the gas fields, causing the green wave to pass them by and reducing surfing by 38% over the 14-year period.

The authors find no evidence that deer are able to adapt their strategies over time to compensate for this disruption. This could negatively affect survival and reproduction as deer become unable to feed sufficiently to meet their energetic requirements.