After the Great War on Earth (soon after the colonization of Beta Colony), North America and South America were much changed. North American wildlife included five-inch-long mosquitoes with venom. While a few bites would not generally kill (only make a person sick), a swarm of them could do significant harm, including significant blood loss in the victim. The ones that had been breeding in high-radiation areas could give nasty burns, as well. Woodchucks were no longer clumsy little furry animals, though what exactly they had become besides dangerous is not specified in the Vorkosigan Saga.