Last Flight of the Ark — D.L. Jackson

Evolution never happened so fast. Twelve hours away from Terra II, Colonel Kaleb Titan, a molecular geneticist and commander of the Ark, faces a life-or-death choice that could change the fate of mankind. The Ark travels with a hold full of wildlife and three crew members. When a wolf bite and genetically-altering gamma radiation transform Kaleb, he notices his senses have been heightened, his libido has gone haywire, and he can't keep his hands off his crew. Worse yet -- or better -- they don't seem inclined to stop him. When their sister ship arrives early, Kaleb's problems compound. As soon as the command crew of the Genesis II boards, one whiff tells Kaleb they're not from Earth. He quickly begins to believe they may be far more ominous than anyone could have imagined. If he's forced to employ biological warfare against them, will it be enough to save humanity? History is about to repeat, and only one species will survive.