Skilled and ferocious hunters though they are, wolves, with their strict social hierarchies, have intense and complex relationships with one another, and the reason why they howl may have more to do with emotion than previously thought, NBC News reports, and their songs may sound mournful for a reason.

Researchers observed nine timber wolves living at Austria's Wolf Science Center in an attempt to understand what motivates their famous howls. Friederike Range, an animal behavior researcher at the University of Veterinary Medicine in Vienna and her colleagues took turns separating the wolves from their packs. They then recorded the length and number of howls that accompanied each wolf's exit from the group.

"What exactly their motivation is, we will never know," Range told NBC News, though she emphasized that "there is an emotional response in there, for sure."

When the wolves were separated from their packs, taken for 20 minute walks by the researchers, their pack members began to howl within seconds. However, not all wolves were howled for equally. If a wolf taken for a walk was a pack leader, he or she received many more howls, and if the departed wolf had a special friend in the group, their friend's songs would last for much longer.

What motivates such behavior in wolves?

David Mech, an adjunct professor at the University of Minnesota who has been studying wolves since the late 1950s, compared the howls of wolves to "children calling for their parents when the parents leave" in an email to NBC News. Although Mech was not involved in the latest study, his experience with wolves has led him to believe that howling is more than simply a form of communication, but of conscious strategy as well.

In his 1966 book "The Wolves of Isle Royale," Mech described witnessing the phenomenon first-hand when a pack of 15 wild wolves had been separated from one another after a hunt.

"After howling, the pack was then able to assemble again," Mech said, and indeed, the newest study on wolf howling, published in the journal Current Biology, provides further evidence that wolves use howling to help each other regroup, and like Mech, the researchers strongly suspect the length and number of songs wolves use are emotionally motivated.

The new research further illustrates that wolves are not purely driven by instinct, and have some level of voluntary control over their howling behavior.