"Frogs definitely cue in on movement, and that's what you're seeing. They're just seeing something moving, and frogs are sit-and-wait predators, so they see movement and they think 'Aha, potential food.' In this case, they can't differentiate that that's a screen," Johnson told The Dodo by phone.
'They're sitting there, so they don't have any metabolic machinery to power. They could sit there for an hour and decide 'Okay, now the food item looks close enough to me.' It's not like they're wasting energy when they're not hunting. They don't have high energy demands, so they can afford to just sit there and bide their time before they strike."