Of the 64 species of mammals currently residing in Pennsylvania approximately 40 are inhabitants or potential inhabitants of Presque Isle State Park. The exact number of species that are inhabitants is not known because of the difficulty of finding obscure forms such as some shrews and small rodents. Therefore, this is a list of species that have been reported for the park or that the author believes are most probable to occur there. A few species such as white-tailed deer, raccoon, cottontail rabbit, and eastern chipmunk are frequently seen by park visitors but most are secretive and rarely observed. Most of the bat species have only been noted by the author through indirect observations made possible by an ultrasound detector. The only Federally Endangered Species of mammal that has a distribution that may include Presque Isle is the Indiana Bat but it is not likely to occur there. Some large species such as porcupine and bobcat often travel great distances and it is likely that these could appear as transients on the peninsula at any time but it is not likely that they would become residents. For example the river otter reportedly has been seen at least once in recent years and a black bear occupied the area for several weeks in winter of 2007-2008. Thus these species are not included on the list. The red fox is a species that was common on the peninsula in the 1980s but it became rare after coyotes established territories there in recent years. Another recent disappearance is that of the deer mouse which was last reported for the park in the 1930s. The loss of open grassy habitat on the peninsula in recent times probably accounts for its demise. At least 15 species are represented by specimens taken from Presque Isle and deposited in the Carnegie Museum of Natural History.