OT: How to reconnect a lost bluetooth mouse?

[Tiemo Hollmann TB]

Hello,

My original mac mouse doesn't reconnects, after the Bluetooth connection is
lost (e.g. after a battery change). Also not after switching the mouse
on/off at the bottom.

Is there any trick to reconnect the blutooth connection or to operate a mac
without a mouse beside a total shut down (with possibly open programs) and
restart?

Sorry for asking this in this list :-)

Tiemo