Large national parks look self-contained on a map. For most wide-ranging species they are a portion of a home range rather than a complete one, and the mismatch drives a great deal of conflict.
The boundaries were drawn for other reasons
Many parks were established around dramatic scenery, watersheds or land that nobody was farming, because those were the areas that could be set aside without contest.
Ecological considerations, where they applied at all, were secondary to ownership patterns, existing settlement and the practical business of getting a boundary agreed.
The result is lines that follow ridges, rivers and surveyed sections rather than the distribution of the habitat a given species needs across a full year.
Seasonal movement crosses the line routinely
Herbivores in many systems move between high summer range and lower wintering ground, and the lower ground is usually the more productive and therefore the more settled.
Predators follow, and territorial carnivores in particular hold ranges far larger than any single park sector, so boundary crossings are a normal part of their year.
Because the crossings are seasonal and predictable, conflict is seasonal and predictable too, concentrating in the same months and the same properties year after year.
Edges behave differently from interiors
A park boundary is an abrupt change in land use, and the strip along it experiences more human contact, more livestock and more roads than the interior.
Animals using that strip face higher mortality, so the effective protected area is smaller than the mapped one, particularly for long, narrow parks.
The ratio of edge to interior therefore matters as much as total area, and a compact park protects more usable habitat than an elongated one of the same size.
Buffer arrangements do most of the practical work
Because expanding parks is politically difficult, conservation on the outside increasingly relies on negotiated arrangements with neighbouring landholders.
These include community conservancies, grazing agreements, easements and compensation schemes, all aimed at keeping the surrounding land usable by wildlife.
Their weakness is that they are voluntary and revocable, so a corridor secured through agreements can be lost through a change of ownership or policy.
Management decisions stop at a line that animals ignore
Fire regimes, disease control, hunting rules and water management all change abruptly at the boundary, even where habitat is continuous across it.
An animal moving between jurisdictions is subject to different rules within a single day, which complicates everything from population estimates to enforcement.
Coordinating across boundaries is therefore a standard part of park management, and where it fails, the park's own management effort can be undone by decisions next door.