Wolves howl more when their friends are absent

New research out of Austria has found that wolves howl not out of stress, but to stay in touch with other members of the pack — and the identity of the missing wolf matters. 

Researchers at the Wolf Science Center in Ernstbrunn used a population of captive wolves to analyze why the animals howl, and under which circumstances, in research published in the Current Biology scientific journal. 

The method was simple: researchers took one member of the pack out for a walk, then watched and listened to what the remaining wolves did, as well as measuring the cortisol (stress hormone) levels of the left-behind animals.

The researchers discovered that howling was influenced considerably more by close social relationships than by stress, up-ending some previous beliefs that the animals howl as a result of anxiety. 

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"We didn't know there was some flexibility on how much they howl depending on their relationship. The amount of howling is really defined by the quality of the relationship." said researcher Friederike Range to the BBC. 

Further, it mattered which wolf was removed: researchers found that a given wolf would howl more if a high-ranking member of the pack was taken out of the enclosure, or if a particularly close friend was given the same treatment. 

"There is an emotional response in there, for sure," commented Range of the behavior to NBC News. "What exactly their motivation is, we will never know." 

Not much is known about why wolves howl, although communication across long distances — and reforming a split-up pack — are possible explanations. The howl of a wolf is audible for miles.