Observability of eastern massasauga (Sistrurus catenatus) during visual encounter surveys in Michigan, USA

Wildlife Society Bulletin
By: , and 

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Abstract

Visual encounter surveys are commonly used to document site occupancy for the eastern massasauga (Sistrurus catenatus; EMR). Efficacy of surveys depends on visual and auditory cues, with basking behavior and burrow use strongly affecting detection. Our goal was to predict body exposure and probability of burrow use from telemetered EMR to better inform implementation of visual encounter surveys. We collected body exposure and burrow use from 23 EMR (14 females [12 gravid], 9 males) from April through September (i.e., active season) at 2 sites in south central Michigan, USA, 2020–2022. Average body exposure for observed snakes was 42% (SE = 3%) and ranged from 0–100%. Percent body exposure during the active season was positively influenced by air temperature, where body exposure increased from ~25% at ~15°C to ~50% at ~35°C. We did not find an effect of cloud cover, hour of day, humidity, or sex on EMR body exposure. Of 176 observations of EMR during the active season, we found EMR using burrows 20 times (~11% of observations). Julian date and air temperature affected the probability of EMR burrow use early in the active season. Probability of EMR burrow use was <0.10 from the end of May through the end of October and was almost 0.00 after mid-July. The probability of using a burrow was generally low (i.e., <0.25) across the range of air temperatures measured in our study, but approached 0.00 as temperatures exceeded 30°C. We did not find an effect of cloud cover, time of day, humidity, or sex on probability of EMR burrow use. Our results indicated that EMR observability in southern Michigan was greatest when air temperatures were 30°C to 35°C, corresponding to when EMR were visible and aboveground.

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Publication type Article
Publication Subtype Journal Article
Title Observability of eastern massasauga (Sistrurus catenatus) during visual encounter surveys in Michigan, USA
Series title Wildlife Society Bulletin
DOI 10.1002/wsb.1605
Volume 49
Issue 3
Publication Date July 11, 2025
Year Published 2025
Language English
Publisher The Wildlife Society
Contributing office(s) Coop Res Unit Leetown
Description e1605, 13 p.
Country United States
State Michigan
County Lenawee County, Oakland County
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