Complex sentence: In January 2012, the town was attacked by a pack of approximately four hundred wolves which, according to biologists, occurred due to a mass migration caused by a shortage in the wolves' natural food sources, in particular blue hares.
Split into simpler sentences: In January 2012, the town was attacked by a pack of about 400 wolves. According to biologists, the attack was due to a mass migration caused by a shortage in the wolves' natural food sources, in particular blue hares.