IV. SWD Overwintering Mortality Forecasts

SWD seeks out warm protected habitats in order to survive cold and sometimes freezing temperatures during the winter. It seems to thrive in urban and suburban environments where building heat, access to underground hiding places, and dense vegetation can all provide thermal protection along with opportunities for finding some food and moisture. Lab data indicate that overwintering SWD may increasingly die at temperatures below 53F due to lack of metabolic activity whereby they are able to seek out and find food and moisture. We combined lab results with remotely-sensed "lights at night", a proxy for human-caused refuge, to model the mortality that SWD experiences over time and space. Results are mapped here in several series for the 48 state US and for the Pacific Northwest comparing the past three winters. We also have more information on this methodology in the form of a slide show and a webinar.