Why do dogs lick people

Just Wow. Photo: Chris Sembrot Photography

Hi Julie,

Yes, but WHY?

I loved Claudia Fugazzas guest post about drawing on dogs social imitation capacities to learn as copy-cats in the Do as I do training technique. Good stuff!

A few things collided this week that resulted in me deciding to look into why dogs lick people. The first was the Huffington Post This Is What Happens When You Ask People To Kiss Their Dogs In Front Of A Camera (example above from Chris Sembrots For the love of dog photography collection) that a friend so kindly brought to my attention. 

The second was this tweet that came to us on Twitter from passionate science education guru (and keen admirer of dogs), Charlotte Pezaro:

@DoUBelieveInDog why do dogs lick you lots when they like you?
— Chloe Zara Potter (@cpezaro) March 28, 2014

Now Julie, like me, Im sure you know theres no quick and easy answer to this - I knew I needed more than 140 characters to respond to Charlotte, and I also threw it out to the 7,500+ people (What! So exciting!) in our Facebook community:

Valid point! Photo: Flickr/jmonin87

Turns out (not surprisingly!) our Facebook community is a really clued in bunch (Ive hazed names to be polite). They pretty much know it all anyway. However, for Charlottes sake, let quickly revisit why indeed, dogs lick us bipedal folk.

Food: the evolutionary basis of licking?
Many people have heard at some point or another that dogs lick at us -- and particularly our faces -- because young wolves lick and poke at adult wolf muzzles to trigger them to regurgitate food that they can then feed on. Its likely that the common ancestor shared by dogs, wolves and other canid species also demonstrated this behaviour, as its also seen in foxes, African wild dogs, etc. 

However, licking is also seen in young canids (and many mammal species) as a newborn behaviour when a puppy seeks the mothers nipples to feed.

This suckling behaviour is thought to be re-oriented to become a useful pacifying gesture. A human analogy is to consider young children thumb-sucking to self-soothe -- imagine if they licked our faces instead when they felt a bit unsure or stressed! Dogs have been seen to use licking as a type of appeasement behaviour - often interpreted by people as intended to reduce tension or apologise. This kind of pacifying lick can be self directed in the absence of other dogs or people, and in extreme cases, can even be a self-mutilation health issue.

Greeting: I lick you = I like you?

Dogs may lick another (dog, or person) during greeting. This can be for a number of reasons as our clever Facebook team outlined. Greetings can even become ritualised, and in addition to licking, can include play bows, rubbing, jumping, running and vocalising.

These can be considered affiliative behaviours - designed to elicit attachment, often interpreted as bonding and playful. 

Not really from a pirate. 

These greetings are generally consistent and independent of how we look or what we do. Lynette Hart (in The Domestic Dog, see below for reference) suggests that "In this way, dogs may provide their owners with feelings of unconditional acceptance, and at the same time, enhance the persons attachment to the dog". 

 

Similar to the evolutionary basis of appeasement licking, affiliative licking may have originally developed in young pups experiencing parental licking to keep clean and generalised into a shared bonding and tactile behaviour amongst littermates. 

Others have suggested that dog licking can be used to dismiss people or increase space. This is interesting (outlined here by Dr Patricia McConnell), and although it has not been published in the scientific literature (to my knowledge), it is something I can relate to from scenarios with my own dog. 

 
If I blow in Calebs face - he will 100%, always, absolutely - lick me. If I do it again, he will 100%, always, absolutely box me with a front paw - usually right in my face. This can be teamed with a play bow and launch into play, he might move his face away or he might leave by walking off altogether. To the left I even managed to interrupt the old mans sleep on the couch to demo this for you (n=1). 

 

So do you think his lick saying "go away"? Or is it a variation on appeasement? Or affiliative? Food for thought. Speaking of food...

Taste: licks to sample?

Maybe we just taste good? We often have salty, sweaty hands and faces, dont we? We put delicious things into our mouths every day, so why wouldnt dogs be interested in having a sample of the residue? 

We can be fairly sure that licking, in addition to smelling, brings a whole host of information to dogs about where we have been, not just what weve ingested. It also gets our attention which may lead to more interaction, feeding, patting - things that serve to reward the behaviour and reinforce dogs that good things come from licking people.

So Julie - and Charlotte - licking is a lot of things. It can be appeasing and it can be affiliating, it can be exploratory and it can be tasty, it can get our attention or maybe even dismiss us, it can be stress relieving and it can be a sign of anxiety. The initial question asked Why do dogs lick you lots when they like us" - but can we assume that because they lick us, they like us? Maybe.

Flickr: MikeBaird

But maybe not always. Its certainly nice to think so. Alexandra Horowitz said, "It is not a stretch to say that the licks are a way to express happiness that you have returned". But then again - it could just be that leg moisturiser you just applied.

What an oxymoron licking appears to be - but it certainly seems important to dogs! 

I think its important we keep asking these kinds of questions and considering the answers from the dogs perspective.

Til next time, big slurps to all!

Mia

p.s. maybe 140 characters is enough after all?

.@cpezaro Short version: can be affiliative, attention seeking, stress relieving, tasty!
— Cobb & Hecht (@DoUBelieveInDog) March 28, 2014

Further reading: 

Mech L.D., Wolf P.C. & Packard J.M. (1999). Regurgitative food transfer among wild wolves, Canadian Journal of Zoology, 77 (8) 1192-1195. DOI: 10.1139/cjz-77-8-1192

Horowitz, A. (2010). Inside of a dog: What dogs see, smell, and know. Simon and Schuster.

Abrantes, R. (2013). Dog language. Dogwise Publishing.

Serpell, J. (Ed.). (1995). The domestic dog: its evolution, behaviour and interactions with people. Cambridge University Press.

Bradshaw J.W.S., Blackwell E.J. & Casey R.A. (2009). Dominance in domestic dogs—useful construct or bad habit?, Journal of Veterinary Behavior: Clinical Applications and Research, 4 (3) 135-144. DOI: 10.1016/j.jveb.2008.08.004

Bonanni R., Cafazzo S., Valsecchi P. & Natoli E. (2010). Effect of affiliative and agonistic relationships on leadership behaviour in free-ranging dogs, Animal Behaviour, 79 (5) 981-991. DOI: 10.1016/j.anbehav.2010.02.021

© Mia Cobb | Do You Believe in Dog? 2014