Ibutton temperature loggers

Stove use was tracked with iButton temperature loggers (Model Number DS1921G, Maxim Integrated, San Jose, CA, USA) that recorded temperature in degrees Celsius every ten minutes. Fieldworkers retrieved data every two weeks using Thermodata data downloaders (Thermodata, Eight Mile Plains, QLD, Australia).
Raw temperature data was transformed into a ‘cooking events’ variable using the AnomalyDetection package in R. While this package was originally developed to detect anomalies in internet traffic, when applied to temperature data, the package detects events that deviate from the ambient diurnal temperature pattern. We applied numerous filters to the processed data, including only considering positive slope anomalies as cooking time and grouping anomalies within 60 min of each other. Stove use was defined as an indicator variable of 0 (no stove use) or 1 (stove use) in each week. Dates were transformed from calendar dates to weeks relative to each participant’s study end date because GRAPHS had a rolling enrollment and exit.

Samples analyzing stress indicators (4-HNE and cortisol) came from AGS that were implanted with I-button temperature loggers (Maxim Integrated, San Jose, CA) using sterile technique in the abdominal cavity in early August from another study as previously described (Rice et al. 2021 (link)). Animals were anesthetized with isoflurane (5% mixed with medical grade oxygen and delivered at 1.5 L/min) to achieve a surgical plane of anesthesia and maintained on 2.5–3% isoflurane throughout the procedure as previously described (Rice et al. 2021 (link)). During the hibernation season, the “shavings added” method was employed to track torpor bout length. On the first day of torpor when respirations were below 5 breaths per minute and the animal was inactive and showed a curled posture, shavings were placed onto the animal’s back. Using this method to identify when animals were hibernating, we monitored the animals daily through the hibernation season. End of a torpor bout was determined when animals’ shavings were disturbed, signifying an interbout arousal (IBA).