Dogs can become so attached to particular toys they display behaviour that would be associated with addictions such as gambling and internet gaming in humans, researchers have said.
According to a study of 105 dogs published in Scientific Reports this month, when certain dogs were deprived of their toys, they became so fixated on what they'd lost that their blood pressure increased and they ignored everything else.
The Austrian veterinary researchers behind the study described this behaviour as a compulsive engagement with a specific activity regardless of any negative consequences.
Before this study, there was only anecdotal evidence to suggest that dogs had addiction-like behaviour towards toys that was similar to human addictions, the researchers said.
Stefanie Riemer, one of the authors of the study, said: "It's a very commonly known phenomenon in kind of the dog world that dogs are called ball junkies."
"Junkie would imply addiction, but of course, is this just a saying, or is there some truth behind it?" said Riemer, a behavioural biologist at the University of Veterinary Medicine in Vienna.
"So, we wanted to see if these highly motivated, highly focused, over-hyper-motivated dogs may fulfil addiction criteria that we have from the human literature, and yes, that's what we did find."
A third of the dogs reportedly displayed behaviour similar to addiction in humans, with the most obsessive breeds being traditional working dogs like German Shepherds or Collies.
Toy-obsessed dogs displayed high levels of frustration and "had very little self-control", Reimer said.
"Even in our cool-down period, when all the toys, all the food, everything had been removed from the room ... some of these dogs stayed highly roused.
"They kept focusing on the door through which the toys disappeared, or on the shelves where toys had been stored. And interestingly, when we measured heart rate, their heart rate remained very elevated the whole 15 minutes of this period after the test."
However, Riemer said the study shouldn't be treated as a "diagnostic tool" to label certain dogs as addicts.
"We did discover some behaviours which would be consistent with addiction criteria from the human literature. But behavioural addictions are difficult even in humans ... so, there's always a grey area," she said.
Why could dogs get addicted to toys?
Professional dog trainer Una McEvoy said dog addiction had everything to do with dopamine.
Dopamine is a hormone that plays a crucial role in the brain's reward and motivation system. It's released during pleasurable activities and reinforces those behaviours.
It's also a factor in addictive behaviour in humans, with alcohol and other addictive drugs appearing to trigger dopamine release.
But dogs don't need drugs. Instead, they get a dopamine release from actions like catching and biting down on a ball or chasing an animal, McEvoy said.
Different breeds will obtain this dopamine release in different ways, she said. For some, it will be from a ball, for others it will be eating, following a scent or playing with a toy.
She said dog owners aren't always prepared for what comes naturally to their pet.
"What I find quite often in my work is that we may have a human that finds a behaviour, an unwanted behaviour, and I do have to break it to them gently that this is this breed's behaviour."
Dog toys are big business
If dogs are getting addicted to their playthings, that's good news for those who produce them.
Pet toys and accessories have become a big business globally.
In 2022, the Australian pet industry was worth $13 billion, covering food, vet bills and, of course, toys.
That also means owning a dog — something nearly half of Australian households do — can get expensive, with a dog costing its owner approximately $25,000 over its lifetime.
McEvoy said there's no better way to keep your dog happy than to play with them yourself.
"I look at two-player toys, so I'm not a fan of a ball, but there's certain toys that have a longer handle and that you can play with your dog.
"Sometimes they have a ball attached to them so you can still throw them if your dog wants to have that chase, but they come back to you, you're still playing tug with them, which means that you are increasing the value of being back to you."
