Comparison of Two Techniques for Surveying Headwater Stream Amphibians

Abstract

: We compared rubble‐rousing versus light‐touch stream amphibian survey techniques in multiple 1‐m plots across 10 streams in southwest Washington, USA. Specifically, we wanted to determine if light‐touch surveys provide unbiased estimates of abundance (i.e., provide counts correlated with rubble‐rousing counts) and which method would provide more cost‐effective presence or absence information. Rubble‐rousing, a common technique for surveying stream‐associated amphibians in the Pacific Northwest, took 12 times as long as light‐touch to apply. Abundance estimates and standard errors for rubble‐rousing were consistently higher than those for light‐touch for all life stages for the coastal tailed frog (Ascaphus truei) and Columbia torrent salamander (Rhyacotriton kezeri). Except for eggs, light‐touch detected all life stages found during rubble‐rousing. For frogs, only some rubble‐rousing abundance estimates, mostly involving second‐year larvae, were highly correlated with their light‐touch counterparts, whereas for salamanders, similar comparisons generated high correlations across most life stages. Correlations between methods were consistently greater for salamanders than for frogs. However the smaller tailed frog sample sizes and the cryptozoic nature of some life stages may have contributed to this pattern. Depending on the degree to which researchers can tolerate false‐negative error rates, light‐touch may prove less costly than rubble‐rousing for detecting species presence. For the cost of obtaining one rubble‐rousing sample, many light‐touch samples can be used across a range of habitats for detecting species patchily distributed.

Factors influencing stream occupancy and detection probability parameters of stream-associated amphibians in commercial forests of Oregon and Washington, USA

“…The same 100 m interval was sampled at each visit. We used the lighttouch method (Hayes et al, 2006;Quinn et al, 2007) to minimize disturbance to the stream segment. We searched the stream-bed and under cut-banks visually and using high-power flashlights and commercial bait-nets.…”

“…Researchers have employed general linear models to analyze occurrence data for SAA (Wilkins and Peterson, 2000;Russell et al, 2004;Stoddard and Hayes, 2005), but these models are appropriate only if detection probability is equal to 1 (or, at least, does not vary across important factors such as space, time, and treatment). Perfect detectability of amphibians generally and SAA specifically (Quinn et al, 2007) is unlikely (destructive, intensive sampling methods should provide high detection probabilities; see Corn and Bury, 1989), and published research reports have not rigorously tested this assumption. As a result, parameter estimates may be biased (Tyre et al, 2003;Gu and Swihart, 2004) and lead to spurious conclusions about SAA/habitat relationships (MacKenzie, 2006).…”

Electroshocking as a survey technique for stream‐dwelling amphibians

“…tadpoles are easily detected via visual encounter, rock rolling, snorkel, and SCUBA surveys (Nielson et al 2001, Quinn et al 2007, adults can be more difficult to locate using these methods (J. Cossel, unpublished data). However, we have commonly encountered adult A. montanus during electroshocking surveys that might have gone unnoticed via other survey methods (e.g., tucked into crevices, hiding under attached moss, or emerging from undercut banks).…”

“…However, we have commonly encountered adult A. montanus during electroshocking surveys that might have gone unnoticed via other survey methods (e.g., tucked into crevices, hiding under attached moss, or emerging from undercut banks). Quinn et al (2007) suggest that light touch (rock rolling) may have limitations when estimating abundance of coastal tailed frogs. However, our high detection probabilities for both adult and larval A. montanus in streams of varying sizes and substrate complexities suggest that electroshocking is a very suitable technique for detecting various life stages of Ascaphus spp.…”

“…There are numerous survey techniques for locating stream-dwelling species of amphibians, including snorkeling and SCUBA (Trauth et al 1993, Nickerson et al 2002, visual-encounter surveys (Crump andScott 1994, Humphries andPauley 2000), dipnetting and funnel trapping (Willson and Dorcas 2003), baited traps (Kern 1984), seining and hand capture (Bury and Adams 1999), leaf litter bags (Waldron et al 2003), and rock rolling (Welsh et al 1997). Rock rolling, also known as rubblerousing (Bury and Corn 1991, Barr and Babbitt 2001, Quinn et al 2007, and light-touch (Lowe and Bolger 2002) has traditionally been used to locate a variety of streamdwelling amphibians including coastal giant salamanders (Dicamptodon tenebrosus; Sagar et al 2007), hellbenders (Cryptobranchus alleganiensis; Hillis and Bellis 1971, Williams et al 1981, Peterson 1987, Soule and Lindberg 1994, mudpuppies (Necturus maculosus; Matson 1990, Nickerson et al 2002, Plethodontid salamanders (Eurycea cirrigera, Desmognathus monticola, D. fuscus, Gyrinophilus porphyriticus; Marsh 2009), torrent salamanders (Rhyacotriton kezeri; Quinn et al 2007), and coastal tailed frogs (Ascaphus truei; Adams 1999, Quinn et al 2007). However, rock rolling has many shortcomings outlined by Foster et al (2008), including the disruption of habitat; possible destruction of nests; difficulty locating small larvae; poor visibility due to silt, surface glare, and water depth; possible back injury to researchers from heavy lifting; and the ability of salamanders to escape unnoticed by surveyors.…”