My kids are 21 and 29 now, so not much looking at the tracker any more for them, but I admit, I still do, and I find it chokes me up every year. Thanks for doing this.

That paper I linked sort of talks about such things.

You have to look at the animal's life history, its evolutionary history, its brain etc. It's a very interdisciplinary thing. I'm a psychologist, but I'm also quite comfortable with zoologists and neuroscientists (to the point where I teach that stuff as well).

They know more than many give them credit for. My work has over the years focused on food storing birds. There are birds who store tens of thousands of seeds in a 40 km radius and recover the vast majority of them, months later. They use memory to do this.

The biggest trap you can get in is trying to rank order species on some made up 'evolutionary ladder' ranking of intelligence. You can study animal intelligence, but it's complicated.

Here's a good theoretical paper to get anyone started who is interested. It's old, but it's a bedrock type of thing, the ideas in here were, at the time, revolutionary, and now are generally accepted.

https://digitalcommons.unl.edu/bioscibehavior/14/

I study animal behaviour and cognition for a living.

Playback experiments are pretty common in animals that use sound to communicate. Song is played on a speaker and reactions are tested. Here's an example

https://link.springer.com/article/10.1007/BF01092552