Estimating deer abundance from line transect surveys of dung: sika deer in southern Scotland

Abstract

Summary1. Accurate and precise estimates of abundance are required for the development of management regimes for deer populations. In woodland areas, indirect dung count methods, such as the clearance plot and standing crop methods, are currently the preferred procedures to estimate deer abundance. The use of line transect methodology is likely to provide a cost-effective alternative to these methods. 2. We outline a methodology based on line transect surveys of deer dung that can be used to obtain deer abundance estimates by geographical block and habitat type. Variance estimation procedures are also described. 3.As an example, we applied the method to estimate sika deer Cervus nippon abundance in south Scotland. Estimates of deer defecation and length of time to dung decay were used to convert pellet group density to deer density by geographical block and habitat type. The results obtained agreed with knowledge from cull and sightings data, and the precision of the estimates was generally high. 4. Relatively high sika deer densities observed in moorland areas up to 300 m from the forest edge indicated the need to encompass those areas in future surveys to avoid an underestimate of deer abundance in the region of interest. 5. It is unlikely that a single method for estimating deer abundance will prove to be better under all circumstances. Direct comparisons between methods are required to evaluate thoroughly the relative merits of each of them. 6. Line transect surveys of dung are becoming a widely used tool to aid management and conservation of a wide range of species. The survey methodology we outline is readily adaptable to other vertebrates that are amenable to dung survey methodology.

Is relative abundance a good indicator of population size? Evidence from fragmented populations of a specialist butterfly (Lepidoptera: Lycaenidae)

“…Various methods exist to estimate the abundance of populations (Marques et al, 2001;Mattoni et al, 2001;Newman et al, 2003), but generally animal populations can be either surveyed visually (Brown and Boyce, 1998;Royer et al, 1998) using standardised replicated surveys (Mattoni et al, 2001), or by more intensive methods employing mark-recapture techniques (Gall, 1984;Baker, 2004;Chao and Huggins, 2005;Pollack and Alpizar-Jara, 2005). The former approach commonly employs a transect survey that records the number of individuals observed over a set distance through a habitat (Pollard, 1977;Brown and Boyce, 1998;Freilich et al, 2000).…”

The success of species reintroductions: a case study of red deer in Portugal two decades after reintroduction

“…Future studies should aim to estimate the production rate, considering the one used was from the U.K., as there is no value available for the Iberian Peninsula or for other region where environmental conditions are more similar. This is particularly important since climatic conditions influence the food present in deer habitats and consequently feeding habits which has a clear role in production rate (Mitchell et al 1985;Mayle et al 1996;Marques et al 2001). In fact, we are aware of this bias, as the used value did not have a variance or standard error associated, meaning the results obtained did not took into account rate variations.…”

“…The coefficient of variation (%) value was higher than the expected, but this can occur in areas where population density is not high (Smart et al 2004), such as in our study area. Several other studies regarding deer density have also recorded wide confidence intervals range, mainly where densities are smaller (Acevedo et al 2010;Marques et al 2001;Acevedo et al 2008). …”

“…CONTACT Rita Torres rita.torres@ua.pt groups with less than 6 individual pellets were not considered (Marques et al 2001). For density estimation we used distance sampling, which implies the modulation of a detection function that is used to estimate the detection probability.…”

Situación de las poblaciones de corzo andaluz (Capreolus capreolus) en las sierras occidentales de Málaga

“…El uso de un índice de abundancia basado en conteo de grupos de excrementos a lo largo de un recorrido puede resultar muy útil, por su sencillez, fiabilidad y relación coste-esfuerzo, habiendo sido empleado en estudios de otras especies de ungulados (Acevedo et al 2008) y en estudios de dispersión y colonización de corzo (Acevedo et al 2005). Transformar abundancia de excrementos en densidad de animales, reduciendo el error de la detectabilidad de los grupos de excrementos mediante Distance Sampling, es una metodología novedosa que ha dado buenos resultados (exactos y precisos) y es rentable en términos de esfuerzo (Marques et al 2001), incluso aplicada en ambientes forestales mediterráneos (Acevedo et al 2010). Sin embargo, no está exenta de asunciones que pueden no ser acertadas.…”