A practical and cost-effective procedure for deer population estimation based on faecal pellet group counts

Reliable population density estimates are crucial for managing wild ungulates in high-density Mediterranean agro-silvo-pastoral landscapes. The conventional faecal standing crop (FSC) method requires estimating two challenging parameters: defecation rate and pellet decay time. To improve field-work-time efficiency, we propose a streamlined FSC procedure incorporating the pellet groups per individual ( \(\:{P}gi\) ) parameter. As a species- and environment-specific metric—or integrated community parameter— \(\:{P}gi\) is derived from enclosures with known deer abundance ( \(\:{D}d\) ) and allows the estimation of deer density ( \(\:{{D}}d\) ) directly in target areas from estimated pellet group density ( \(\:{{D}}pg\) ). We evaluated two sampling strategies—strip transect (ST) and line transect (LT)—in two fenced sites with known deer numbers ( Santa Rita , \(N=5\) ; Tapada dos Bichos , \(N=93\) ). Both methods demonstrated high sampling precision ( \(\:CV%≈\:11%-20%\) ). However, ST was significantly more fieldwork-time efficient, requiring less than half the total observer-effort of LT in the larger study area. Propagated precision for final deer density estimates ( \(\:CV%\) of \(\:{{D}}d\) ) consistently met the standard \(\:≤\:25%\) management threshold across scenarios (except LT in Santa Rita ). While \(\:{P}gi\) requires initial calibration in a known population, it can subsequently be applied to target management areas with similar habitat, climate, and species composition. Under the tested conditions, the \(\:{P}gi\) -based ST protocol provided a more time-efficient alternative to LT while maintaining equivalent sampling precision, offering a practical framework for deer monitoring.