Birds given low doses of the pain killer Fentanyl to induce pleasure produce ‘gregarious’ song that ‘sounds like free-form jazz’, a study shows.
Researchers from the University of Wisconsin, Madison, theorised that when birds sing, opioids are produced in their brains that give them pleasure.
To prove their theory they gave starlings a doze of Fentanyl – an opioid used as a pain killer and a recreational drug – and then listened to their song.
They found that when birds sing for pleasure, rather than to mark out territory or to find a mate, the singing is ‘gregarious’ and sounds like jazz.
Biologist Lauren Riters and colleagues found that the song after the opioid drug was the same type of sound birds make when they get together in a flock.
‘When they’re practising, they try out different songs, they order and reorder and repeat song sequences, they add and drop notes,’ said Riters.
‘It sounds a bit like free-form jazz and it is quite distinct from the structured songs that male songbirds produce when trying to attract mates.
‘It is the free-form songs that are produced during practice that our studies show to be rewarding.’
Researchers from the University of Wisconsin, Madison, found that when birds sing in flocks rather than for mating purposes it is ‘gregarious’ and gives them pleasure
Previous studies into birdsong have focused on how it is produced and why it developed in the first place – but this is the first study to look at why they sing.
To better understand the underlying pleasure birds get from ‘warbling’, Riters looked at the behaviour of a group of European starlings.
The researchers decorated an area and put the birds inside after they had sung, then later gave them a choice of returning this area or an undecorated space.
The birds spent longer in the decorated area, suggesting they associated it with the pleasure they gained from singing.
‘It’s evidence that a positive state is induced by the presence of flock-mates, which stimulates song, and that birds continue to produce gregarious song because it is rewarding,’ Riters said.
‘Although male songbirds are famous for singing when they are away from other birds, for example when they are defending territories and attempting to attract mates, many birds also sing at high rates in more social contexts.
‘Our results suggest that birds sing because they feel good, and that singing helps them to maintain this positive state.’
Once they established the fact birds link singing to pleasure, they wanted to find out exactly why – theorising it was due to the production of opioids in the bird brain.
Opioid drugs like Fentanyl, Heroin and Morphine are known for giving pleasure and reducing pain in animals – creatures also produce their own natural opioids.
This production of the pleasure-giving chemical plays a central role in rewarding positive behaviours including socialising, eating and mating.
The low dose of Fentanyl given to the birds to induce artificial pleasure was designed to replicate the levels expected when they sing for joy.
The team say this automatically triggered high rates of the type of warbling song seen when the birds are in the flock.
When birds sing it produces opioids in their brains – to prove this the team, led by biologist Lauren Riters, gave starlings a doze of fentanyl then listened to their song.
‘Here we’ve shown that opioids cause singing behaviour,’ Riters said, adding that it also seemed to reduce stress-related behaviours in the birds.
They were also able to show the opposite – by using chemicals to switch off the opioid receptors in the brain they could reduce how much the birds sing.
The overall results suggest that the presence of flock mates may naturally lead to opioid release int he brain of birds and produce a positive, low-anxiety state.
They also found that singing in its own right can trigger this same response and the same findings in bird brains could apply to almost all animals.
‘If this is the case, it would mean that our studies on songbirds are revealing an ancient, evolutionarily conserved neural circuit that regulates intrinsically rewarded social behaviors across many animals,’ Riters told Psychology Today.
The discovery of an underlying link between socialisation and opioid release could help researchers develop treatments for people who are socially withdrawn.
The findings have been published in the journal Scientific Reports.