WHITE-TAILED DEER AS A ZOOGEOMORPHIC AGENT ON A POST-FLOOD STREAM TERRACE, BUCKS COUNTY, PENNSYLVANIA

The population of white-tailed deer (Odocoileus virginianus) in southeast Pennsylvania has been increasing due to a lack of predators and decreasing hunting pressure. This study investigated the impact of the deer along a bedrock-controlled terrace of Neshaminy Creek (Northampton, Bucks County) following an intense storm event (Ida, 2021). The accompanying flood stripped ground vegetation and re-deposited patches of legacy mud along small feeder creeks draining from a sandstone outcrop. Trampling and individual hoofprints of O. virginianus were studied geo-located and measured (dimensions, travel azimuth) to assess their distribution and short-term impact. Adult and subadult/juvenile cervid tracks occurred on two types of substrate: silty mud (loading pressure ~0.28 kg/cm²) and sandy gravel (~0.19 kg/cm²). Individual hoofprints ranged from 4.0-9.0 cm in length, 2.0-4.0 cm in width, and 1.0-5.5 cm in depth. The deepest prints were due to edge-loading on mud-rich sloping sections. On average, an individual white-tailed deer was found to have displaced >200 cm³ of sediment per step (non-overlapping four-point contact), increasing substantially with sliding. In addition to slope erosion, increasing particle size reduces compaction and raises permeability upon impact. Our results suggest that ungulates travelling along and l streams (cervids, suids, etc.) must be considered as significant zoogeomorphic agents of erosion and redeposition, capable of initiating and sustaining geomorphic cascades in riparian watersheds.