PELLET: An Excel®-Based Procedure for Estimating Deer Population Density Using the Pellet-Group Counting Method

Abstract

Pellet-group counting (PGC) is a commonly used method for estimating the population density of various ungulate species. The method assumes a positive linear relationship between the number of animals and the number of pellet-groups. To estimate population density from PGC, three parameters must be determined: defecation rate, persistence time, and spatial pattern of pellet-groups. This article introduces PELLET, a semi-automatic procedure in Microsoft Excel® for estimating population density in deer. The purpose of PELLET is to support deer managers and studies that determine and compare densities in different types of habitats. The density calculation includes a range of variation in the defecation rate that eliminates the subjective practice of selecting one single defined value for this rate. The calculation also incorporates spatial variation and deposition time. PELLET comprises four Excel® worksheets, the choice of which depends on type of plot and number of field samples. As an example, I describe the application of this procedure in a case study. Spanish and English versions of PELLET are freely available online.Keywords: monitoring, defecation rate, spreadsheet, linear model, probability distribution. ResumenEl conteo de grupos fecales (CGF) es un método empleado comúnmente para estimar la densidad poblacional de varias especies de ungulados. Este método asume una relación lineal positiva entre el número de venados y el número de grupos fecales. Para convertir el CGF a número de animales, se requiere conocer tres parámetros: la tasa de defecación, el tiempo de permanencia y el patrón espacial de los grupos fecales. En este artículo se introduce PELLET un procedimiento semiautomatizado en Excel® para estimar la densidad de venados. El propósito de PELLET es apoyar a los manejadores y estudiosos de los venados para calcular y comparar las estimaciones en diferentes tipos de hábitats principalmente bosques densos en regiones tropicales y otras. El cálculo de la densidad se realiza incluyendo un rango de variación en la tasa de defecación lo cual elimina la subjetividad de seleccionar solo un valor determinado de la misma. Además, el cálculo incorpora la variación espacial y el tiempo de depósito de los excrementos. PELLET tiene cuatro hojas dependiendo el diseño de muestreo: tipo de parcelas y número de muestreos en campo. A manera de ejemplo, se presenta la aplicación de este procedimiento en un estudio de caso. PELLET está disponible gratis en línea en versión en español o inglés.Palabras clave: monitoreo, tasa de defecación, hoja de cálculo, modelo lineal, distribución probabilística.

Low accuracy of identifying Neotropical deer species by scat morphology

“…Classification functions for species of the genera Mazama, Ozotoceros and Blastocerus that can show sympatry between two species in the Atlantic Forest, Cerrado and Pantanal. addition, studies on density estimation using pelletgroup counts are very common among cervids (Mandujano 2014), including South American populations (Rivero et al 2004;Periago & Leynaud 2009). In Neotropical species, Chame (2003) has already highlighted the impossibility of differentiating between M. gouazoubira and M. americana by measuring scat samples.…”

Conservation Value, History and Legal Status of Non-Native White-Tailed Deer (Odocoileus Virginianus) on the Caribbean Island of St. Kitts

“…parasite load). Methods such as distance sampling [60], fecal pellet counts [61], and camera trap surveys [62], could reasonably accomplish this goal relatively quickly and inexpensively. This data would form a baseline from which to move forward and begin assessing other important components of their conservation, as well as associated ecological and human health risks, such as population demography (survival, mortality, and growth rates); the probability of persistence, through a Population Viability Analysis (PVA) [63]; and observing and recording novel white-tailed deer behavior and life characteristics.…”

Classification of Vegetation Types in the Habitat of White-Tailed Deer in a Location of the Tehuacán-Cuicatlán Biosphere Reserve, Mexico

“…To estimate population density, we employed PELLET version 2.1, which is a semi-automatized procedure in Excel ® [36]. PELLET approaches density calculation by assuming that density has a probabilistic distribution depending on variation in the parameters of defecation rate, time of persistence of the fecal pellet-groups, and the pattern or spatial distribution of the fecal pellet-groups.…”