Assessing Methods for Detecting Island Spotted Skunks

Abstract

Island spotted skunks (Spilogale gracilis amphiala) are endemic to 2 of the California Channel Islands (CA, USA)-Santa Cruz and Santa Rosa. The status of skunks is uncertain, although incidental captures in traps set for island foxes (Urocyon littoralis) suggest that skunks have declined to low numbers. We superimposed wildlife cameras at fox traps in 2016 and 2017 to provide a second measure of skunk detectability. On both islands, detection rates of skunks with fox traps (0.92/100 operating nights) and with cameras (0.72/100 operating nights) did not differ during summer, indicating the 2 methods are of similar reliability for detecting skunks. In 2017, skunk detections with cameras increased from summer to early winter, suggesting monitoring in winter may improve survey efforts. Low detection rates of island spotted skunks (<1/100 operating nights) were comparable to those of other spotted skunk populations that are considered rare. KEY WORDS California Channel Islands, camera trap, carnivores, island fox, island spotted skunk, Spilogale gracilis amphiala, Urocyon littoralis.

An evaluation of detection methods for the plains spotted skunk

“…At the county level, the detection rates in Coryell (0.36%) and Waller (0.27%) compared favorably with those in Missouri and the rate in Harris County (0.73%) was comparable with 0.81% reported for Arkansas (Hackett et al 2007). Recent assessment of the detectability of the island spotted skunk (S. g. amphiala) resulted in low detection rates for both live traps (0.92%) and camera traps (0.72%; Bolas et al 2020). We confirmed that live traps, track plates, and cameras traps likely would detect plains spotted skunks if the species is present, although in areas with low abundance, such as the FWNCR, multiple surveys may be required for detection.…”

“…Recent assessment of the detectability of the island spotted skunk ( S. g. amphiala ) resulted in low detection rates for both live traps (0.92%) and camera traps (0.72%; Bolas et al. 2020). We confirmed that live traps, track plates, and cameras traps likely would detect plains spotted skunks if the species is present, although in areas with low abundance, such as the FWNCR, multiple surveys may be required for detection.…”

“…In Arkansas, the detection success of live traps was not compared to that of cameras traps and track plates; however, it was reported that live traps were more successful than the other 2 devices (Hackett et al 2007). Live and camera traps were both equally efficient at detecting island spotted skunks, but the ability of each to remain operational was not reported (Bolas et al 2020). Live traps provide the potential for collection of tissues, ectoparasites, and other biological samples not possible with cameras or track plates; however, this trade‐off requires more time and resources.…”

“…In Arkansas, the detection success of live traps was not compared to that of cameras traps and track plates; however, it was reported that live traps were more successful than the other 2 devices (Hackett et al 2007). Live and camera traps were both equally efficient at detecting island spotted skunks, but the ability of each to remain operational was not reported (Bolas et al 2020).…”