Heatmap based on xy-coordinates

Hey there! I am new to plotly and R/Matlab, and I dearly need your help.
I have a dataset which consists of x and y coordinates that indicate the trajectories of 6 animals simultaneously tracked in 6 different open-space arenas (see Fig.).

I have created a scatter plot, but I think it would make a lot more sense if I displayed heat maps on the very frequently explored areas? Many thanks in advance for any advice!