Estimating Squirrel Abundance from Livetrapping Data

Nixon, Charles M.; Edwards, William R.; Eberhardt, Lee

doi:10.2307/3798363

Cited by 22 publications

(13 citation statements)

References 5 publications

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“…This method was used by Edwards & Eberh a r d t (1967) to estimate a known experimental cottontail rabbit population; with the exception of the Lincoln index, other methods tended to over or underestimate the number of individuals present. Nixon et al (1967) working with two species of tree squirrels, also found that linear regression estimates closely approximated those obtained with the Lincoln index, whereas other methods produced poor fits and much lower values. The assumptions of the regression method are similar to those for the Petersen index, as described previously.…”

Section: Discussionmentioning

confidence: 70%

The ecology of Glaucomys volans (Linnaeus, 1758) in Virginia

Sonenshine¹,

Lauer²,

Walker³

et al. 1979

Acta Theriol.

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The ecology of the southern flying squirrel, Glaucomys volans (L i nn a e u s, 1758) was studied in 2 areas of central Virginia, using artificial tree shelter traps and baited live trapping. Within one year after their installation, 46.9% of the artificial shelters were used for nesting sites, 26.6% as feeding stations, and 17.2% as defecatoria; only 9.4% were without evidence of use. The animals utilized several shelters for nesting in addition to others used for food storage and defecatoria. In habitat selection, availability of bodies of fresh water was important, but the slope of the terrain was not significant. Foraging (average range 126.8 m ± 14.8 S.E.) was not significantly related to distance from aquatic habitat. Adult males foraged substantially farther than sexually inactive females or juveniles. Most females (94.2%) became pregnant within 6-8 months after birth. Birth of young occurred in early spring, March and April, and in late summer, from August to early October. Removal rate of young squirrels from the population by mortality was 50% within 5.5 months and 67% in 7 months. Population density, estimated by the Petersen index and regression analysis of recapture frequency, varied at different seasons from 4.5 to 10.1 flying squirrels/ha at one of the localities, and from 6.2 to 13.8/ha at the other.

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Section: Discussionmentioning

confidence: 70%

The ecology of Glaucomys volans (Linnaeus, 1758) in Virginia

Sonenshine¹,

Lauer²,

Walker³

et al. 1979

Acta Theriol.

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“…The former two (of which the Geometric is a special case of the Negative Binomial) are founded on a model of heterogeneity in p deriving from unequal trap access. Although these methods have been justified on theoretical grounds (Eberhardt, Peterle & Schofield, 1963;Gates & Smith, 1972) support for them comes largely from goodness-of-fit tests and empirical evaluation Nixon et al, 1967;Tanton, 1965). Cormack (1979) and Seber (1982) concur that these methods should be regarded as statistical descriptions which might be generated by various, quite different, models.…”

Section: Discussionmentioning

confidence: 99%

“…A good deal of caution is therefore necessary in applying zero-truncated distributions to estimate population size. This is of particular relevance to grey squirrel studies, since Nixon et al (1967) have recommended the Geometric method for this species.…”

Section: Discussionmentioning

confidence: 99%

Empirical evaluation of several population size estimates applied to the grey squirrel

Don¹

1984

Acta Theriol.

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“…Otis et al (1978) and White et al (1982) discuss problems and procedures for estimating abundance from capture data. We conclude from our data that probability of capture of fox squirrels varies (is heterogeneous) among individuals, among occasions, and that it changes after the first capture-a response similar to that noted for gray squirrels (Nixon et al 1967;Bouffard and Hein 1978). We compared seasonal changes in trapping efficiency (marked capturelmarked known available) for marked squirrels known to be alive.…”

Section: Trapping Periodsmentioning

confidence: 62%

Demographic characteristics of an unexploited population of fox squirrels (Sciurus niger)

Nixon¹,

Hansen²,

Havera³

1986

Can. J. Zool.

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1986. Demographic characteristics of an unexploited population of fox squirrels (Sciurus niger). Can. J. Zool. 64: 5 12-52 1. Demographic changes in an unexploited population of fox squirrels (Sciurus niger) were studied between 1971 and 1978 on 45.2 ha of upland forest in east-central Illinois. Known numbers of squirrels varied between 69 and 142. Adult squirrels (> 15 months old) comprised >50% of the known population during the study, with annual survival exceeding 60%. Young-ofthe-year made up <20% of the livetrapped population. Increasing populations were characterized by increases ( P < 0.05) in numbers of yearling-adult males and young-of-the-year of both sexes. Recruitment depended on both immigration and on production of young by resident females. Recruitment success (proportion of new squirrels resident at least 6 months after initial capture) of immigrants was best for adults and yearlings and poorest for subadults. Adult female breeding success was highest in the winter and correlated negatively with the number of females conceiving the previous breeding period. The size and composition of the seed crop of trees in autumn had no effect ( P > 0.05) on recruitment, conception, survival rates, or changes in overall density when at least some winter-storable tree seed was available. In most years, adult females were dispersed evenly, but adult males and young of both sexes showed an aggregated or random dispersion. Breeding rates for yearling females, recruitment success of immigrants and of juveniles born on the study area, and overall changes in squirrel densities between trapping periods correlated negatively ( P < 0.05) with the number of adult females but not with the number of males or younger females. Interpretation of dispersion of adult females and the relationship of numbers of adult females to population change suggest that fox squirrels stabilize their numbers in the absence of obvious environmental stresses through aggressive interactions between adult females and resident young and immigrants of all ages.

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Estimating Squirrel Abundance from Livetrapping Data

Cited by 22 publications

References 5 publications

The ecology of Glaucomys volans (Linnaeus, 1758) in Virginia

The ecology of Glaucomys volans (Linnaeus, 1758) in Virginia

Empirical evaluation of several population size estimates applied to the grey squirrel

Demographic characteristics of an unexploited population of fox squirrels (Sciurus niger)

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