I got a new iMac, which comes with a wireless keyboard and mouse. These accessories look slick, but the mouse cursor does all sorts of bizarre jumping around on the screen. Am I doing this or do I have a feral mouse?
The Bluetooth-enabled “Magic Mouse” that comes with Apple’s new iMac computers can react to different finger movements you make when holding it. If the mouse seems to be performing a specific action like enlarging the view of a Web page, the device is probably responding to one of Apple’s integrated “multi-touch gestures.” (Double-tapping the top of the mouse with a finger makes it zoom in or out of the open window on the Mac’s screen.)
Apple has a guide to the various Magic Mouse gestures on its site. If you find the gestures more annoying than helpful, you can change how the mouse behaves. To do so, open the Mac’s System Preferences icon on the Dock (or go to the Apple menu in the top left corner and choose System Preferences). Click the Mouse icon to get to the controls for mouse behavior. Adjusting the mouse’s tracking speed may also help the jumpy cursor.
The Mouse preferences box also displays the battery’s strength level. If you were not using the multi-touch gestures, a low battery may be the cause of the mouse’s erratic performance; instructions for changing the batteries are here.
If all that seems fine and the mouse is still jumpy, check the sensor on the bottom of the device for dust or debris and clean it if needed. Using the mouse in a different desk surface or on a clean mousepad may also help. Multiple Bluetooth devices too close to the Mac can cause interference, so if you have Bluetooth speakers, a headset or other wireless devices nearby, try turning those off and see if the mouse calms down.