Differences in trapping mortality rates of northern flying squirrels

Abstract

1993. Differences in trapping mortality rates of northern flying squirrels. Can. J. Zool. 71: 660-663. We described trapping mortality rates of northern flying squirrel (Glaucomys sabrinus) populations in western Oregon, U.S.A., and evaluated the effects of sex, age, body mass, and number of times an individual was recaptured on these rates. Although the overall trapping mortality rates were relatively low (7%) during 16-21 day trapping sessions, we observed differential mortality rates among the sex and age cohorts. The order of mortality rates was: juvenile females (32.3 %) > juvenile males (11.1%) > adult females (5.1%) = adult males (4.1%). Overall trapping mortality rates were not affected by the number of times an individual was captured. We hypothesize that the differences we found were due to extrinsic factors (weather-related) acting on differential behavioral responses to trapping and thresholds of stress an animal can tolerate. ROSENBERG, D. K., et ANTHONY, R. G. 1993. Differences in trapping mortality rates of northern flying squirrels. Can. J. Zool. 71 : 660-663. Nous avons déterminé les taux de mortalité au piégeage dans des populations du Petit Polatouche (Glaucomys volans) de l'ouest de l'Orégon, U.S.A. et évalué les effets du sexe, de l'âge, de la masse et du nombre de recaptures sur cette mortalité. Bien que le taux de mortalité global au piégeage ait été assez bas (7%) au cours de périodes de piégeage de 16 à 21 jours, les taux variaient d'après le sexe et l'âge. La mortalité décroissait de 32,3 % chez les jeunes femelles à 11,1 % chez les jeunes mâles, à 5,1% chez les femelles adultes et à 4,1% chez les males adultes. Il n'y avait pas de relation entre le nombre de fois qu'un individu était recapturé et la mortalité globale. Nous croyons que les différences que nous avons observées sont dues à des facteurs extrinsèques (réliés au climat) agissant sur les réactions comportementales variables au piégeage et sur les niveaux de stress que chaque animal peut supporter.[Traduit par la rédaction]

Peer Review #3 of "Effects of trapping effort and trap placement on estimating abundance of Humboldt’s flying squirrels (v0.1)"

“…Live trapping remains an important technique in these studies but can be both labor intensive and physically demanding, and project costs are sensitive to the number of project trap nights. In addition, capture events can cause considerable stress or even mortality of target and non-target species, especially during longer trapping sessions (Sikes, 2016), although this pattern has been debated for some species (Rosenberg & Anthony, 1993). To minimize invasiveness of vertebrate research, it is important to carefully consider how best to incorporate the principles emphasized by the three R's (Replace, Reduce, Refine) of animal welfare, while still obtaining sufficient samples from which to draw inferences from the data (Russell & Burch, 1959;Powell & Proulx, 2003;Villette et al, 2016).…”

“…Flying squirrels also contribute to the maintenance of ecosystem health through the dispersal of hypogeous fungi, berries, and seeds (Maser, Trappe & Nussbaum, 1978;Bowers & Dooley Jr., 1993;Carey et al, 1999). Much of the early research on flying squirrels focused on differences in abundance among young, mature, and old-growth forests (Rosenberg & Anthony, 1993;Carey et al, 1999;Holloway & Smith, 2011). More recent research emphasis has been on understanding the effects of timber harvest strategies implemented to speed the development late-seral forest characteristics from young, managed forests (Carey, 2000;Holloway et al, 2012;Manning, Hagar & McComb, 2012;Wilson and Forsman 2013).…”

“…Second, some studies reported fewer squirrel captures during the first week of study, and a subsequent increase of captures during the second week, especially in structurally complex forests (Wilson, 2010). Other trapping protocols have been used to sample arboreal rodents in the PNW (Rosenberg & Anthony, 1993;Rosenberg & Anthony, 1995;Ransome & Sullivan, 1997). However, we are unaware of any studies that examined how increasing or decreasing the number of trap nights influences flying squirrel abundance estimates.…”

A novel technique for detecting northern flying squirrels

“…Currently, live‐trapping is frequently employed to detect and capture flying squirrels throughout their range (Smith and Nichols ). Although live‐trapping is effective for quantifying attributes of populations of flying squirrels, the technique can be costly to implement at large scales; flying squirrels also have been reported to be sensitive to capture myopathy, which can affect populations and bias survey results (Rosenberg and Anthony ). Increasingly, noninvasive techniques are commonly used to detect a wide range of wildlife species (Gompper et al , Long et al ).…”

Salt marsh harvest mouse abundance and site use in a managed marsh

“…Increasing trapping periods may also be cost prohibitive and may increase animal trap mortality (D.K. Rosenberg & Anthony, 1993), a concern when dealing with an endangered species. By definition, endangered species sample sizes tend to be small, making sampling difficult (MacKenzie et al, 2005).…”