One summer morning of the year 1989, myself and a forestry technician were just finishing up a routine spotted owl survey in the northern part of the Chuska Mountain range. After calling for owls at a call point, just before sunrise, we began to walk back to the vehicle when we heard a loud, deep yell/roar from down below our position. The habitat was a mixed conifer stand within a deep dark canyon. Since there are sheep camps throughout the Chuska Mtn. range, it did cross our mind that perhaps someone (a human) was yelling but the distinct factor that myself and the technician had agreed upon was that the yell was very deep and long (lasted approx. 5 seconds). After the vocalization, the echo itself retained the deepness of the sound as it travelled through the canyon below us. This was definately not a human that had the lung capacity to make such a sound. After researching it a bit more recently, about sasquatch sightings, audio clips etc., my theory is the animal, whatever it was, may have been responding to our sounds, since we were calling with the imitated vocalization of the the Mexican Spotted Owl. I've listened to several audio clips of recorded sasquatch vocalizations and can see where one may have mistaken us for another creature of its kind.