090916_S2-2-24_P06_2min

Pups were individually identified with long-lasting subcutaneous tattoos (green tattoo paste, Ketchum Manufacturing) on the paws on P1. Each pup was isolated from dam and littermates and placed in a small enclosure with soft plastic surface in a soundproof chamber (temperature T=24+/1°C). Audio recordings lasted 5 min and were conducted every 2 days (P2, P4, P6, P8, P10 and P12). Recording hardware (UltraSoundGate 416-200, condenser ultrasound microphone Polaroid/CMPA) and software (Avisoft SASLab Pro Recorder) were from Avisoft Bioacoustics (sampling frequency 300kHz; fast Fourier transform length 1024 points; 16-bit format). The present file was recorded at P06 and trimmed with the first two minutes.