Vertical scale: frequency (0-2500 hertz); horizontal scale: time (1 frame aprox. equal to 2 seconds); color: signal strength (from lowest to highest, violet, blue, green, yellow, orange, red).
The series of adult howls heard here can be classified as "lonesome"
or "lone" howls. Variation in their structure likely indicates who is howling,
and the frequency modulations, particularly the sudden changes in pitch, make
the howls much easier to locate.