For many plants and animals on the Galapagos Islands, survival makes for some prickly partnerships. Indeed, many of the animals here would not have been able to survive without the food, water and shelter that the cacti provide. The plants are helped in return by having their pollen transported from blossom to blossom, and their seeds dispersed over the landscape. But the cacti have also had to protect themselves against the destructive tendencies of the animals that depend on them. In the ensuing competition both sides - plant and animal - have developed canny tricks to be able to accomplish their purpose while also avoiding being abused.