Marble burying behavior was assessed based on published methods (Deacon, 2006; Thomas et al., 2009). The testing apparatus consisted of a polycarbonate mouse cage (internal dimensions: 33 cm long × 21 cm wide × 19 cm high) filled to a depth of 5 cm with pine wood bedding (Harlan Sani-Chip, Indianapolis, IN), and placed in a sound-attenuating chamber lighted by a bank of white LEDs (75 lux). White noise and ventilation were supplied by a PC fan. Prior to each test, twenty clear, glass marbles (10 mm diameter) were evenly spaced and arranged in a grid-like fashion across the surface of the bedding. Then, individual mice were placed into the observation cage, which was then covered with a transparent, Plexiglas lid with air holes. At the conclusion of the 20 min test, the mice were carefully removed from the chamber and the number of buried marbles (50% or more of the marble was covered by bedding) was determined. Inter-observer reliability for assessing marble burying was > 98%.
