Direct relationship between evapotranspiration rate (ET_O) and vertebrate decomposition rate

When vertebrate scavenging is excluded, the Evapotranspiration Rate (ET_o) of a given geographic region directly regulates the decomposition rate of unclothed vertebrate carrion, with any deviation attributed to insect activity. We conducted four decomposition experiments using pig carrion (Sus scrofa domesticus) over the span of two years (2018-2020) at a location in Davis, California. We used ET_o, a variable that accounts for five climatic parameters (wind, temperature, humidity, solar radiation, and altitude) as the rate-determining variable of the decomposition process. We found ET_o to have a strong (R² = 0.98) predictive relationship with the decomposition rate. To account for maggot activity decomposing the carrion, we measured maggot weight in 2019 and 2020 using a novel method, and in 2020 we used FLIR imagery to measure maggot mass temperatures as a surrogate measurement of total maggot activity. Maggot activity was a significant predictor (p < 0.0001) of the decomposition rate, while maggot weight was not (p > 0.1). We hope to show the forensic entomology community the potential of using ET_o. Future projects can incorporate ET_o as a baseline to decomposition studies to determine if ET_o remains the most accurate descriptor of decomposition and ultimately increase certainty in the Postmortem Interval (PMI).