Owl pellets: a more effective alternative to conventional trapping for broad‐scale studies of small mammal communities

Abstract

1. Small mammal community composition is almost universally estimated from conventional trapping, which is logistically difficult to scale up for landscape-level assessments. Owl pellets may be a more effective alternative for measuring small mammal community composition over large geographic areas due to the relative ease and low cost of field collections. However, owl pellets may introduce sampling biases that differ from those associated with conventional trapping. A thorough comparison to conventional traps is required before owl pellets can be widely adopted as an alternative research tool for small mammal studies. 2. We conducted a literature review of owl diet-prey availability studies to: (i) compare small mammal community composition between owl pellets and trapping when the two methods were used simultaneously and (ii) assess the influence of owl genus and habitat type on community composition estimated by these two methods. We used data from 27 published studies, which allowed for 32 comparisons between owl pellets and trapping conducted simultaneously. These studies included 15 owl species from five common genera from different major habitats. 3. Rarefied estimates showed that owls consistently sampled identical or higher species richness compared to conventional trapping. Richness estimates rarefied to the lowest sample size per study were not statistically identical (l Drichness = 0Á20 AE 0Á09 SE, P = 0Á30); on average, 0Á95 AE 0Á13 SE additional species were identified from pellets compared to trapping. Measures of species dominance and evenness estimated from both methods were statistically identical (l D1-D = 0Á02 AE 0Á03 SE; l DPIE = 0Á004 AE 0Á04 SE). Species lists, relative species composition and species rank-order abundance were in moderate agreement between sampling methods (Jaccard = 0Á62 AE 0Á04 SE; Bray-Curtis = 0Á53 AE 0Á04 SE; Spearman rho = 0Á41 AE 0Á07 SE). Linear regression and AIC model selection showed that the performance of pellets versus traps did not differ based on owl genus or habitat type. 4. Small mammal community composition estimated via pellets was better represented compared to estimates from conventional trapping. Composition metrics from the two methods were consistent and not affected by owl genera or habitat type. Thus, owls are an effective alternative for landscape-level assessments of small mammal communities.

Using owl pellets to infer habitat associations and clarify the regional distribution of a cryptic shrew

“…On the one hand, owl pellets allow the detection of more species than other standard methods of sampling small mammals, such as live-trapping (Torre, Arrizabalaga & Flaquer, 2004;McDonald, Burnett & Robinson, 2013). Moreover, owl pellets are often collected with relatively less effort than live-trapping, especially when applied over large geographical areas (van Strien et al, 2015;Heisler, Somers & Poulin, 2016). On the other hand, most survey methods are incapable of reliably distinguishing morphologically similar species.…”

The prey composition of the Barn Owl(Tyto alba)with respect to landscape structure of its hunting area (Zala County, Hungary)

“…trapping (Heisler et al 2016). Advantage of the pellet analysis in contrast to the trapping is that the rare small mammal species are more often detected by using this indirect method (Torre et al 2004(Torre et al , 2015.…”

“…Advantage of the pellet analysis in contrast to the trapping is that the rare small mammal species are more often detected by using this indirect method (Torre et al 2004(Torre et al , 2015. Owls are an effective alternative for landscape-level assessments of small mammal communities (Heisler et al 2016).…”

Sex Ratio of Rodents as Barn Owl (Tyto alba) Prey

“…This aligns with local habitat usage by voles and deer mice (e.g., Randall and Johnson, 1979;Kaufman et al, 1988;and Falls et al, 2007, respectively). It also reflects the fact that barn owls are opportunistic feeders (Smith et al, 1972;Marti, 1988;Marra et al, 1989), therefore remains of prey in their pellets tend to reflect the small mammal fauna on the landscape (Hadly, 1999;Terry, 2010;Heisler et al, 2016).…”