Abundance and ecological associations of small mammals

Weldy, Matthew J.; Epps, Clinton W.; Lesmeister, Damon B.; Manning, Tom; Linnell, Mark A.; Forsman, Eric D.

doi:10.1002/jwmg.21641

Cited by 20 publications

(21 citation statements)

References 87 publications

(115 reference statements)

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“…Similarly, capture probability was substantially higher on HJA sites relative to SIU sites. The abundance estimates presented here are similar to those reported by Weldy et al (2019) which were obtained using HJA data. Apparent annual survival was similar on both the HJA and SIU sites.…”

Section: Discussionsupporting

confidence: 89%

“…However, we are unaware of any studies that examined how increasing or decreasing the number of trap nights influences flying squirrel abundance estimates. Weldy et al (2019) recently estimated Humboldt’s flying squirrel abundance using Huggins closed-population models and found the estimates of precision were very small, in some cases small enough that the reported estimates resemble a full census, suggesting that reducing trap nights could be considered. Similarly, considerable time and energy goes into hanging traps on trees.…”

Section: Introductionmentioning

confidence: 99%

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Effects of trapping effort and trap placement on estimating abundance of Humboldt’s flying squirrels

Weldy

Wilson

Lesmeister

et al. 2019

PeerJ

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Live trapping is a common tool used to assess demography of small mammals. However, live-trapping is often expensive and stressful to captured individuals. Thus, assessing the relative tradeoffs among study goals, project expenses, and animal well-being is necessary. Here, we evaluated how apparent bias and precision of estimates for apparent annual survival, abundance, capture probability, and recapture probability of Humboldt’s flying squirrels (Glaucomys oregonensis) varied with the number of secondary trapping occasions. We used data from forested sites trapped on 12 consecutive occasions annually in the HJ Andrews Experimental Forest (9 sites, 6 years) and the Siuslaw National Forest (seven sites, three years) in Oregon. We used Huggins robust design models to estimate parameters of interest for the first 4, 8, and 12 trapping occasions. We also estimated the effect of attaching Tomahawk traps to tree boles on site- and year-specific flying squirrel capture frequencies. Our estimates with 12 occasions were similar to those from previous studies. Abundances and capture probabilities were variable among years on both sites; however, variation was much lower on the Siuslaw sites. Reducing the length of primary trapping occasions from 12 to 8 nights had very little impact on parameter estimates, but further reducing the length of primary trapping occasions to four nights caused substantial apparent bias in parameter estimates and decreased precision. We found that attaching Tomahawk traps to tree boles increased the site- and year-specific capture frequency of flying squirrels. Our results suggest that live-trapping studies targeting Humboldt’s flying squirrels in the Pacific Northwest of the United States could reduce per-site costs and stress to captured individuals without biasing estimates by reducing the length of primary trapping occasions to 8 nights. We encourage similar analyses for other commonly-trapped species in these and other ecosystems.

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Section: Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Effects of trapping effort and trap placement on estimating abundance of Humboldt’s flying squirrels

Weldy

Wilson

Lesmeister

et al. 2019

PeerJ

Self Cite

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“…We felt that this assumption was met on our study-sites, which were randomly placed within a large, continuous, old late-successional forest where site edges did not reflect biological edges. Further, Carey (1995) suggested that there was no evidence that the densities of flying squirrels and chipmunks were misleading indicators of habitat suitability, and Weldy et al (2019) found no evidence for marginal or sink habitat on our study sites. Presence of sink habitats would have indicated that individuals were more likely to emigrate from or immigrate to specific sites.…”

Section: Discussionmentioning

confidence: 62%

“…Flying squirrels have been characterized as a potentially K-selected species, with survival that is higher than similar-sized mammals (Smith, 2007; Villa et al, 1999) and varies little across time (Lehmkuhl et al, 2006). However, other demographic characteristics such as abundance (Weldy et al 2019), sex ratio (Rosenberg & Anthony, 1992), and recruitment (Weldy et al 2020) vary substantially across time. Much less is known about chipmunk demography, but they have been characterized as an r-selected species with population growth rates primarily driven by recruitment and generally lower survival which can exhibit substantial temporal variation (Weldy et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Emigration Effects on Estimates of Age- and Sex-specific Survival of Small Mammals

Weldy

Lesmeister

Epps

2021

Preprint

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Age- and sex-specific survival estimates are crucial to understanding important life-history characteristics and variation in these estimates can be a key driver of population dynamics. When estimating survival using Cormack-Jolly-Seber (CJS) models and capture-recapture data, emigration is typically assumed to have a negligible effect on estimates such that apparent survival is indistinguishable from true survival. Consequently, especially for populations or age classes with high dispersal rates, apparent survival estimates are often biased low and temporal patterns in survival might be masked when site fidelity varies temporally. We used 9 years of annual mark-recapture data to estimate age-, sex-, and time-specific apparent survival of Humboldt's flying squirrels (Glaucomys oregonensis) and Townsend's chipmunks (Neotamias townsendii). For Humboldt's flying squirrels, these estimates support a small body of research investigating potential variation of survival among age and sex classes, but age- and sex-specific survival has not been evaluated for Townsend's chipmunks. We also quantified the effects of age- and sex-specific emigration on confounded estimates of apparent survival. Our estimates of juvenile flying squirrel survival were high relative to other small mammal species and estimates for both species were variable among years. We found survival differed moderately among age and sex classes for Humboldt's flying squirrels, but little among age and sex classes for Townsend's chipmunks, and that the degree to which emigration confounded apparent survival estimates varied substantially among years. Without correcting for emigration, apparent survival estimates were lower and temporal variation was obscured, particularly for male Humboldt's flying squirrels and female Townsend's chipmunks. Our results demonstrate that emigration can influence commonly used estimates of apparent survival. Unadjusted estimates confounded the interpretation of differences in survival between age and sex classes and masked potential temporal patterns in survival because the magnitude of adjustment varied among years. We conclude that apparent survival estimators are robust during some time periods; however, when emigration rates vary in time the effects of emigration should be carefully considered and accounted for, especially in comparative studies and those with policy and conservation implications.

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“…

Small terrestrial mammals are of extraordinary importance in most terrestrial ecosystems (Barrett and Peles, 1999;Weldy et al, 2019). Their biomass, relatively high and variable abundance, short generation interval, and rapid response to changing conditions make them one of the most sensitive bioindicators of change throughout the environment (e.g., Pearce and Venier, 2005;Heroldová et al, 2018).

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mentioning

confidence: 99%

Efficiency of pitfall traps and snap traps in small terrestrial mammals depends on their diet composition

Čepelka¹,

Michalko²,

Kula³

2019

Turk J Zool

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Small terrestrial mammals are of extraordinary importance in most terrestrial ecosystems (Barrett and Peles, 1999;Weldy et al., 2019). Their biomass, relatively high and variable abundance, short generation interval, and rapid response to changing conditions make them one of the most sensitive bioindicators of change throughout the environment (e.g., Pearce and Venier, 2005;Heroldová et al, 2018). At the same time, small terrestrial mammals are among the vertebrates that are most difficult to trace (Zejda, 1991). Different types of traps (snap traps, pitfalls, live traps) are mostly used to describe communities of small mammals (e.g., Sheftel, 2018).Numerous studies have already been devoted to comparing the effectiveness of different trapping methods and types of traps. Some have also been devoted to the direct comparison of the different ways of using pitfalls and snap traps under different habitat conditions (e.g.

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Abundance and ecological associations of small mammals

Cited by 20 publications

References 87 publications

Effects of trapping effort and trap placement on estimating abundance of Humboldt’s flying squirrels

Effects of trapping effort and trap placement on estimating abundance of Humboldt’s flying squirrels

Emigration Effects on Estimates of Age- and Sex-specific Survival of Small Mammals

Efficiency of pitfall traps and snap traps in small terrestrial mammals depends on their diet composition

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