Wolves howl for social reasons, not becaue they're loners, research shows. It's not stress or bloodlust- it's love.

New research says wolves howl to show they care and to look for other wolves.

Rather than being a bone-chilling sign of violence, wolves howl to show they miss their friends or mates.

Wolf howling is not a sign of stress or hunting signal, but due to being separated from members of their pack.

Howling is more likely to occur when a close member of the wolf family leaves the pack.

Hormone level tests show that the howling was not due to stress.

 'Our data suggest that howling is not a simple stress response to being separated from close associates, but instead may be used more flexibly to maintain contact and perhaps to aid in reuniting with allies,' said lead author Dr Friederike Range from the University of Veterinary Medicine in Vienna.

In a new study, handlers took wolves out on a leash for long walks, one at a time.

And each time the individual wolves parted from their pack, the wolves left behind would howl.

'Our results suggest the social relationship can explain more of the variation we see in howling behaviour than the emotional state of the wolf,' said Dr Range, lead author of the study.

The researchers found that when a pack could sense the presence of a pack member, even if it was out of sight, they didn't howl.

The wolves howled more when the animal taken away was close to, or of a higher social rank, than the rest of the pack.

However, they found no link between howling and stress hormones.

 'If they are close to the departing animal, they then howl more. It is a form of communication with the other animal, but what they want to say we just don't know.

'But the key is friendship. Whether they are saying 'I miss you' or 'here I am, please come back', we are not sure, but it is likely because there is a strong social bond.'

The researchers measured hormone levels and data about relationships within the pack. They recorded when the wolves would howl, and which reacted the most.

Another recent study found that each wolf's howl is very individual, and that they can even be identified by "voice".