Adult male gorillas have taken to singing for their supper, literally -- with the behaviour being documented by researchers in the wild for the first time.
The 'singing' and 'humming' of the male great apes has been described in a study published in the PLOS ONE journal today.
While many birds and mammals -- including chimps and bonobos -- vocalise when finding or eating food, there had only been anecdotal evidence about gorillas.
The authors, from Germany and New York, studied two wild western lowland gorilla populations in the Republic of Congo and recorded and analysed the noises the apes of different ages and sexes made in response to different foods.
Of those in the groups, the adult males including the silverbacks called the most. The females and young gorillas were quieter, which the researchers suggest could reduce the risk of predation to vulnerable individuals.
The 'singing' and 'humming' was only observed in association with food --particularly aquatic vegetation, flowers and seeds.
It has been suggested the calls are a way of expressing their well-being, but could also help with group cohesion and coordination.
"Similar to the function of food calls in chimpanzees, gorillas may call to let their group mates know when it is time to finish eating," lead author Dr Eva Maria Luef says.
"Silverback males may have to call more frequently since they are often the ones initiating changes in group activity."
Only 20 gorillas in two groups were part of the observation and the researchers didn't analyse what the sounds meant in relation to specific foods.
However, the researchers say the findings could give more insight into the vocal abilities of gorillas and form a basis for future investigations.