Among the worst enemies of the Ice Age's giant mastodons was a charging frenzied monster with curved tusks backed by six tons of angry flesh and bone — in other words, other mastodons, according to new evidence. Three-dimensional modeling of fossil mastodon skulls, tusks and bone injuries make a compelling case for the possibility that the male, or bull elephant-like animals of the ice age often fought dramatic battles to the death over mating rights. "There's a pattern of damage that's observed on several different skulls," said mastodon expert Dan Fisher of the University of Michigan. Crushed bone found under and behind one eye would have required puncturing a tough skin and 20 inches of jaw muscles. "It's not a place that'd be easy to get to just thumping around," he said. The 3-D modeling of the injuries has also revealed at least one injury that conforms to the shape of a tusk tip. "The short of it is that there was tusk impact on bone." And there was death. Fisher presented his discovery this week at the meeting of the Society of Vertebrate Paleontology in St. Paul, Minn. The telltale injuries also support the idea that bull mastodons probably went into a crazed mating state of mind, called musth, in the same way as do modern bull elephants, hippos and elk in rutting season. While in musth bulls do not eat and are extremely violent towards other males — to the point of deadly jousting. More evidence that bull mastodons were in musth when they died is the tree-ring-like growth records in their tusks. The tusks indicate that the bulls were probably fasting at the time of death, Fisher said.