I have a few thoughts here.
First, I don’t doubt for a second that dogs can experience grief, or that they recognize distress in others. The book For The Love of a Dog is great, if you’re interested in this topic.
However, I do have some reservations about dogs understanding the storyline of a cartoon. This question is interesting because we’re trying to determine whether a dog understands another being’s internal state…and in the process, we’re trying to understand another being’s internal state. Turtles all the way down. Since we’re humans, we can try to reason it out and imagine what it’s like to be a dog.
Luna, this (very sweet) dog, is four months old. What does she know about death? What are the chances that she’d recognize death from a scene like this? Why would we even assume that dogs, who live in an olfactory world, would rely on visual cues for this important event? Why would Simba’s heavily anthropomorphized expression (he cries!) spell sadness to her – especially as she’s likely seeing a series of slides rather than fluid movement (since the framerate is human-appropriately low)?
Now, looking at Luna, she is definitely broadcasting anxiety. I don’t think she is particularly sad. If you mute the video, it’s easier to focus on her body language. She looks extremely interested to me, and confused. Watching her ears, she’s very alert. Her general posture displays a lack of confidence. Her tail shows how excited she’s getting, and her raised hackles indicate that she’s spooked.
Listening to only her vocalizations, she does sound sad. But then again, we humans tend to interpret all whining as sadness and pain. There’s another video of the same dog, anticipating a friend’s arrival. She’s clearly excited and happy, but her whining still sounds sad to me. My own dog sounds pathetically sad when he sees girlfriends, and he is head over heels in love with them all.
So, if I had to guess what’s happening: this is a young and excitable dog who hasn’t learned that what’s on TV isn’t necessarily real. There’s a weird cat-shaped being on the wall. It’s exciting, but strange. If the humans in the room are getting emotional, Luna is picking up on that through her amazing powers of observation and smell.
She’s clearly very sensitive and attentive. I bet she’s a lot of fun, and she seems loved. Thanks for sharing this!