Visual method for evaluating the state of sexual development in male grey squirrels (Sciurus carolinensis)

2006 ◽  
Vol 18 (3) ◽  
pp. 383 ◽  
Author(s):  
Mark Ferryman ◽  
Brenda A. Mayle ◽  
Geoff W. Morgan
Keyword(s):  
Sexual Development ◽  
Population Biology ◽  
Captive Breeding ◽  
Fertility Control ◽  
Sciurus Carolinensis ◽  
High Group ◽  
Visual Method ◽  
Epididymal Spermatozoa ◽  
Grey Squirrels ◽  
Selection Of

Stages of sexual development in grey squirrels were classified by scoring the presence of periscrotal hair and staining, as well as the position, size and colour of testes, to develop a visual breeding score (VBS). The VBS was a highly significant predictor of the presence and concentration of epididymal spermatozoa, which were produced from 12 months of age. Two classes of producers were identified: ‘high’ with spermatozoa levels >10 × 106 mL−1 and ‘low’ with spermatozoa levels <10 × 106 mL−1. Sperm motility was variable across all levels of productive males but was generally higher in the ‘high’ group, indicating that these were ‘functional’ males. Sexual regression was observed in two autumn periods. The VBS was less effective in determining states of regression and redevelopment; the confidence of classification improved when age class (adult or prepubertal) and date of capture was known. The use of the VBS to classify stages of sexual development in grey squirrels will improve selection of animals for studies of population biology and fertility control, and has potential application in captive breeding studies of rare Sciuridae species.

scholarly journals The Distribution and Habitat Selection of Introduced Eastern Grey Squirrels, Sciurus carolinensis, in British Columbia

2005 ◽  
Vol 119 (3) ◽  
pp. 343 ◽  
Author(s):  
Emily K. Gonzales
Keyword(s):  
British Columbia ◽  
Habitat Selection ◽  
Coniferous Forests ◽  
Sciurus Carolinensis ◽  
Conifer Forests ◽  
Residential Land ◽  
Bodies Of Water ◽  
Land Types ◽  
Grey Squirrels ◽  
Selection Of

Eastern Grey Squirrels were first introduced to Vancouver in the Lower Mainland of British Columbia in 1909. A separate introduction to Metchosin in the Victoria region occurred in 1966. I surveyed the distribution and habitat selection of Eastern Grey Squirrels in both locales. Eastern Grey Squirrels spread throughout both regions over a period of 30 years and were found predominantly in residential land types. Some natural features and habitats, such as mountains, large bodies of water, and coniferous forests, have acted as barriers to expansion for Eastern Grey Squirrels. Given that urbanization is replacing conifer forests throughout southern British Columbia, it is predicted that Eastern Grey Squirrels will continue to spread as habitat barriers are removed.

scholarly journals Selection of Agricultural Foods by Eastern Grey Squirrels (Sciurus carolinensis): Implications for a New Introduction in British Columbia

2016 ◽  
Vol 130 (3) ◽  
pp. 202
Author(s):  
Jillian M McAllister ◽  
Valerie Law ◽  
Karl W Larsen
Keyword(s):  
British Columbia ◽  
Local Scale ◽  
Sciurus Carolinensis ◽  
Grey Squirrel ◽  
Food Items ◽  
South Central ◽  
Fruit Growing ◽  
Free Ranging ◽  
Grey Squirrels ◽  
Selection Of

The recent introduction of the Eastern Grey Squirrel (Sciurus carolinensis) into south-central British Columbia occurred within an important agricultural zone. As repercussions for the fruit-growing sector are currently unknown, we conducted trials with captive squirrels to understand the range of fruits consumed and their references. The squirrels consumed a portion of every food item offered, although the order in which the foods were used was inconsistent (with sharp contrasts between animals). Of the fruit types offered, apples appeared to be of greatest overall interest. However, seeds and nuts tended to be used first when presented in combination with fruit, suggesting opportunities to use these food types to deflect or remove Eastern Grey Squirrels from orchard crops. We caution that our results may not reflect the food items that free-ranging Eastern Grey Squirrels will target or disregard once densities in the introduced population become higher and the availability of food on a local scale begins to exert an effect.

scholarly journals Preserving Wildlife: An International Perspective

2001 ◽  
Vol 7 (2) ◽  
pp. 146
Author(s):  
Nadia Elizabeth Tapp
Keyword(s):  
Wildlife Management ◽  
Native Species ◽  
Captive Breeding ◽  
Management Strategies ◽  
Field Studies ◽  
Moral Values ◽  
International Perspective ◽  
Management Approaches ◽  
Sport Hunting ◽  
Selection Of

PRESERVING Wildlife: An International Perspective is an anthology of twenty papers exploring the issues related to the preservation of wildlife, with an emphasis on related management approaches. This topic is introduced philosophically with a discussion of moral values associated with human activities. Sport hunting, the medical aid of injured wild animals and the manipulation of wildlife during ecological field studies are discussed within this context. The focus then shifts to a selection of wildlife management strategies including habitat protection, captive breeding, culling of non-native species, eco-tourism and marketing of wildlife products.

Brushtail possums (Trichosurus vulpecula) in metropolitan Sydney: population biology and response to Suprelorin contraceptive implants

2013 ◽  
Vol 61 (1) ◽  
pp. 78 ◽  
Author(s):  
J. Eymann ◽  
D. W. Cooper ◽  
C. A. Herbert
Keyword(s):  
Urban Areas ◽  
Population Biology ◽  
Local Population ◽  
Fertility Control ◽  
Main Peak ◽  
Brushtail Possum ◽  
Trichosurus Vulpecula ◽  
Management Options ◽  
Contraceptive Implants ◽  
Over Time

The cohabitation of the common brushtail possum (Trichosurus vulpecula) with people in urban areas often causes conflict. Basic biological parameters are needed to evaluate potential new management options such as fertility control. This study investigated the biology of an urban brushtail possum population and the effects of Suprelorin contraceptive implants on individual females within that population. Trapping success remained constant over time, with 2.8 ± 0.2 individuals trapped per residential property. Recapture rates for males declined rapidly over time, with only 30% of males recaptured on the same property 12 months after initial capture (n = 30) and no males recaptured after 18 months (compared with female recapture rates of 58% after 18 months, n = 33). These data, combined with the preponderance of males observed within the lower age classes, suggests that male possum turnover is high within urban areas. This may be partially compensated for by the male-bias (1.8 : 1) observed in pouch young. Breeding was seasonal with the main peak of births in autumn, and a secondary smaller peak in spring. Suprelorin contraceptive treatment effectively inhibited reproduction in adult females for a minimum duration of 519 ± 7 (n = 5) and ≥700 ± 20 (n = 5) days after administration of one or two 4.7-mg implants, respectively, with no negative side-effects obvious. The concurrent collection of data on contraceptive efficacy and population-specific life-history parameters provides a unique opportunity to highlight the importance of understanding local population dynamics when evaluating the likely efficacy and implementation of fertility control programs to manage problem wildlife.

Behavioural differences between locally recruiting and dispersing gray squirrels, Sciurus carolinensis

1990 ◽  
Vol 68 (5) ◽  
pp. 935-941 ◽  
Author(s):  
M. Pasitschniak-Arts ◽  
J. F. Bendell
Keyword(s):  
Sex Ratio ◽  
Laboratory Tests ◽  
Population Regulation ◽  
Tail Length ◽  
Sciurus Carolinensis ◽  
Colour Morph ◽  
Resident Population ◽  
Behavioural Type ◽  
Local Recruitment ◽  
Selection Of

We tested the hypothesis that recruitment into a resident population involved the selection of an independently defined behavioural type of animal. Gray squirrels were captured in or shortly after leaving their nests, held in the laboratory in a similar manner, and their behavioural profiles and other properties were determined. The following spring, they were released into the area where most were captured and which we virtually emptied of residents prior to the release. Sixty days following the release, 64% (18/28) of the squirrels had dispersed, most before 10 days, and the remainder recruited and became residents. From the laboratory tests, local recruits compared with dispersers were on average more aggressive. There were no clear differences between the two types in mass, tail length, and sex ratio. All were sexually immature. Recruits were more active than dispersers in December, and activity of both appeared to decline from November to April. Proportionately more of the pepper morph recruited than of the black and gray morphs. There appear to be genetic behavioural and colour morph differences among squirrels that affect or are linked to their local recruitment or dispersal and population regulation.

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