The system default Bluetooth tool does not reliably detect this mouse (or my Bluetooth speaker!). I recommend installing the better Bluetooth manager "blueman", which, unlike the system's default Bluetooth tool, reliably detects everything and has plenty of functionality. To do so:
sudo apt-get install blueman
Then run "Bluetooth Manager" from the system menu. It will put an applet in the system tray area of the panel.
The default Bluetooth tool will still run, but you can configure it not to show an icon in the system tray. (Right-click on the icon to do this).