Purdue University began studying the predator–prey interaction, the wolves were up to 20 and the moose down to 538. The two population numbers have seesawed ever since. Peterson, who joined the project as a graduate student in 1970 and later moved to Michigan Technological University in Houghton, was teaching dissection using some moose metatarsal bones that he had collected from mainland Michigan. (The metatarsus in a moose makes up the hind leg and serves as a proxy for body size.) Peterson noticed that their size was “consistently above the average for Isle Royale moose. Then when researchers in Minnesota started collaring moose and making collections from dead animals, I saw an opportunity to collect enough moose bones to do a respectable comparison.” As is reported in the current issue of the moose journal Alces, researchers measured the length of more than 1000 metatarsal bones collected on Isle Royale and found that the mean was significantly shorter than that of bones collected from nearby mainland moose, by about 9 millimeters for females and double that for males. The difference with moose bones collected from mainland Sweden and Alaska was even greater; Isle Royale moose, it seems, may be among the smallest in the world. Shripad Tuljapurkar, a Stanford University evolutionary biologist who has worked on the evolution of phenotypic traits, calls the paper “an insightful historical analysis that provides valuable detail about evolution in a large mammalian species and marches with the general island rule.” The detail, he notes, should help in creating analytical models of size change for species with island and mainland populations.