The NGSD's most unique characteristic is its dramatic ability to vary the pitch of its howl. They do not bark repetitively but have a complex vocal behavior including yelps, whines, and single-note howls. NGSD's are active, lively, and alert. They are constantly exploring everything in their environment, using all five senses, including taste. Their incredible structural flexibility allows them to pass their bodies through any opening wide enough to admit their head. Their hunting drive is very intense and may overwhelm any training when prey is detected. They use their acute sense of hearing in addition to sight and scent to locate prey. Although gentle and affectionate with people they know, they can be aloof with strangers. NGSD's can be aggressive toward other dogs, especially of the same sex.