I experienced this yesterday in chernarus.
I didn't hear anything until one from a pack started lunging at me.
Also, wolves and zombies have been ignoring each other since (charnarus) the release of Livonia.
Happens on my private server with no mods or edits.
It seem when they do a fix or update, they also break something else.

The latest patch has fixes this so its no longer an issue.
Can mark this as resolved.

Alright, i think i know what is going on here so this may not be a bug issue.

Cars still leak fuel after 1.06 Dec. 3 update Charnarus.