The availability of GPS technology has enhanced biological knowledge while creating opportunities for conservation, especially for species such as manatees (Trichechus manatus
), humpback whales (Megaptera novaeangliae
) and African elephants (Loxodonta africana
) where conflicts with humans continue to intensify (Wilson et al. 2004
; Douglas-Hamilton et al. 2005
; Pomilla & Rosenbaum 2005
). Although ecological phenomena such as migration are fascinating, challenges to their persistence will arise because of the increasing demand of humans for habitable space. This creates an urgent premium to identify lands crucial for protection.
Our documentation of an invariant migration corridor is noteworthy for two reasons. First, not only is this migration of archeological and cultural importance, but the round-trip movement involves three geographical bottlenecks through which every individual (200–300) of an entire park population must pass. Any obstruction is likely to extirpate pronghorn from GTNP, a supposition bolstered by the loss and failure to re-establish historically used pathways to and from the region's two national parks, Yellowstone and GTNP (inset in ).
Second, the current migration persists in a country with nearly 300 million people and where current national energy policy is reducing biological diversity on public lands (Ehrlich 1994
; Berger 2003
). For instance, some migrants cross areas that nurture petroleum development, which at full scale will fragment parts of routes that pronghorn have used for millennia. Given the rarity of relict migrations among terrestrial mammals in the Western Hemisphere in excess of even 100
km (Berger 2004
) and a desire of most American citizens to maintain a semblance of ecological integrity in national parks (Soule et al. 2003
), the invariant route we report that still involves part of an ancient pathway should warrant protective action.
Nevertheless, there are issues of scale, size and ecological function. Unlike the Serengeti with its migratory wildebeest, zebra (Equus burchelli) and Thompson's gazelle (Gazella thomsonii) or Arctic caribou where hundreds of thousands or more move long distances, why should a mere 200–300 migratory pronghorn be of concern? After all, it is common knowledge that there are more pronghorn than people in the State of Wyoming.
Two issues are germane. First, the protection of this migration corridor is more than symbolic. If obstructed, whether by petroleum development, housing or other factors, an entire population from a national park will be eliminated, leaving a conspicuous gap in the function of native predator–prey interactions there. Second, ecological processes are being sacrificed globally, some as a consequence of death by a thousand cuts and others by massive and rapid changes in land use. In an era with few conservation victories, particularly in developed countries, if biological diversity is to be promoted in less-developed countries, we must maintain equal or greater concern for local wildlife conservation by establishing the permanent protection of corridors, whether they are ancient and still functioning or new. Our report of an invariant migratory route suggests that when corridors persist, when they are narrow and when temporal variability in use is low, it should be easier to enact robust conservation measures.