In The Descent of Man, Charles Darwin noted that ‘everyone has seen how jealous a dog is of his master’s affection, if lavished on any other creature.’
But since the evolutionary biologist made the observation in 1871, scientists have debated whether animals can actually feel jealousy, with many arguing it is an emotion that only humans exhibit.
Now experts believe they have proven that dogs do get jealous when their owners give too much attention to a rival.
The University of California discovered that dogs were far more likely to snap and push at their owners if they felt they were being excluded from their affection.
"Our study suggests not only that dogs do engage in what appear to be jealous behaviours but also that they were seeking to break up the connection between the owner and a seeming rival," said lead researcher Professor Christine Harris.