The use of drey counts to estimate Grey squirrel populations

Don, B. A. C.

doi:10.1111/j.1469-7998.1985.tb05656.x

Cited by 13 publications

(7 citation statements)

References 6 publications

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“…Our data on presence/absence of grey squirrels in the different woodlots within their distribution range can also be used to make an informed estimate of minimum population size. The population of Stupinigi forest, based on drey counts and the regression of grey squirrel density on drey density calculated by Don (1985) for English woodlands, was estimated at 305 animals. However, the mean density of grey squirrels, 0.5/ha 1 , was rather low and might be the result of the above relationship not being applicable to the Stupinigi habitat.…”

Section: Discussionmentioning

confidence: 99%

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Grey squirrel Sciurus carolinensis management in Italy ‐ squirrel distribution in a highly fragmented landscape

et al. 1997

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American grey squirrels Sciurus carolinensis introduced to northern Italy in 1948 have caused damage to commercial poplar plantations and have replaced the native red squirrel Sciurus vulgaris from most of the 350 km2 of the Piedmont Po‐plain they currently occupy. In order to plan a control programme aiming to stop grey squirrels from further spreading and to decrease their numbers, the current distribution and population size in the highly fragmented landscape of the Po‐plain were studied. The probability of finding grey squirrels in woodland fragments increased with habitat quality (diversity of trees producing large, consumable seeds), woodlot size and the proportion of poplar. Adding isolation variables did not improve the fit of the logistic regression model that predicted squirrel presence. The density of squirrel dreys, an index of population density, in the large Stupinigi forest also increased with tree species diversity. An estimate of the minimum population size for all woodlots assessed for squirrel presence was 1,260 animals in the summer of 1996. This extrapolates to a total of ca 2,500 grey squirrels in Piedmont. Grey squirrels continue to increase their range and are getting close to the continuous mixed forests of the pre‐Alps and to large hazel plantations. Control measures to stop the spread of grey squirrels, and eventually to eradicate them, should be implemented immediately.

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Section: Discussionmentioning

confidence: 99%

“…At the Stupinigi forest a drey census was carried out to estimate squirrel density and determine habitat preferences (Don 1985, Wauters & Dhondt 1988). Dreys were counted in 37 census plots of 1 ha each, by walking through every plot on straight lines about 10 m apart (Wauters & Dhondt 1988).…”

Section: Methodsmentioning

confidence: 99%

Grey squirrel Sciurus carolinensis management in Italy ‐ squirrel distribution in a highly fragmented landscape

et al. 1997

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“…Nests are highly visible and reliable indicators of squirrel presence (Bouffard 1982, Don 1985); therefore, we applied distance‐sampling methods to data collected from line transects to assess density of nests within the study area and relative density among forest types (Anderson et al 1979, Don 1985). The short trees (12.0 ± 1.0 m) and low density of large trees (≥40 cm dbh; 33.3 ± 7.2 trees/ha) in the study area provided an ideal environment in which to locate nests and assess density; consequently, we are confident we met distance‐sampling assumptions of 100% detectability on the transect line (Buckland et al 2001).…”

Section: Methodsmentioning

confidence: 99%

Importance of scale in nest‐site selection by Arizona gray squirrels

Cudworth

Koprowski

2011

J Wildl Manag

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Nests provide a place for individuals to rest, raise young, avoid predators, and escape inclement weather; consequently, knowledge of habitat characteristics important to nest placement is critical for managing species of conservation concern. Arizona gray squirrels (Sciurus arizonensis) are endemic to mountains of southwestern United States and northwestern Mexico. We investigated factors influencing nest‐site selection at 4 spatial scales (forest‐type, nest‐site, nest‐tree, and within‐canopy placement) to provide ecological information and management recommendations for this sensitive species. Nest densities were 2.6 times higher in riparian than pine‐oak woodlands. Nest sites had more large trees, snags, logs, and canopy cover and had lower slope. Arizona gray squirrels selected tall trees with more interlocking trees and tended to place nests adjacent to the main trunk. Regardless of scale, Arizona gray squirrels seemed to select nesting areas for their ability to provide protection from predators and the elements as well as access to food. Consequently, maintaining large trees with closed canopies and downed logs should be considered when determining land management plans. © 2011 The Wildlife Society.

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“…Red-bellied squirrels construct dreys (spherical leaf and stick nests) in trees; dreys are visible from the ground, are excellent indicators of tree squirrel presence (Don 1985) and were the primary means by which we documented presence of this introduced species. The squirrel nests are unique in design and shape, so they could not be confused with nests of other animal species.…”

Section: Methodsmentioning

confidence: 99%

Distribution and spread of an introduced insular population of red-bellied squirrels (Sciurus aureogaster) in Florida

Palmer¹,

Koprowski²,

Pernas³

2014

Mammalia

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Introduced populations of species pose one of the greatest threats to the persistence of native species. Documentation of distribution, range expansion and habitat use of introduced populations are key components of developing effective management strategies for the control and eradication of invasive species. In 2006 and 2007, we surveyed four islands in Biscayne National Park for nests to evaluate the presence of redbellied squirrels (Sciurus aureogaster) and the distribution and index of dispersion of their nests in the Florida Keys archipelago within the Atlantic Ocean. Red-bellied squirrels were initially introduced to Elliott Key, Florida, USA in in 1938. We documented evidence of squirrels on two additional islands, Sands Key and Old Rhodes Key, which adds to concerns of spread of this introduced squirrel to areas with endangered endemic insular mammals. Squirrel nests were documented only in mixed-hardwood forest, and nests had a clumped distribution within this forest type. Range expansion was a chief concern to the National Park Service, as continued spread could result in squirrels exiting the park, and prompted management action. Understanding nest site selection and distribution was critical for developing an eradication strategy for the introduced population of red-bellied squirrels from south Florida.

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The use of drey counts to estimate Grey squirrel populations

Cited by 13 publications

References 6 publications

Grey squirrel Sciurus carolinensis management in Italy ‐ squirrel distribution in a highly fragmented landscape

Grey squirrel Sciurus carolinensis management in Italy ‐ squirrel distribution in a highly fragmented landscape

Importance of scale in nest‐site selection by Arizona gray squirrels

Distribution and spread of an introduced insular population of red-bellied squirrels (Sciurus aureogaster) in Florida

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