Tiger populations are protected, but are they connected?

Maintaining protected areas for tigers may seem like an obvious conservation step.  But what about making sure that those protected areas connect populations?  While protected areas are known to provide safe habitat for territories and mating, little is known about how well connected protected areas are, and how the surrounding landscape allows for dispersal between populations to ensure genetic flow.  In a new publication in PLoS ONE, Joshi et al. ask whether protected areas that support tiger populations have high connectivity, and how landscape elements in the matrix between protected areas might influence that connectivity.  Since dispersal events for large, rare mammals can be infrequent and difficult to observe, the study uses genetic techniques to look at genetic diversity, relatedness, population structure and migration between six protected areas in central India to infer information about population connectivity in a highly human dominated region.  The authors combined genetic analysis with landscape resistance models to determine which factors in the landscape between protected areas might be most influential for gene flow and dispersal in tigers.

Two main results stand out from the study: 1. Tigers seem to disperse at much greater distances than previously seen with empirical data such as camera traps – at least 345 km and possibly over 600 km, and 2. Roads and human settlements, particularly high density human settlements, act as the biggest barriers to population connectivity.  Considering this, an individual attempting a very long-distance migration through densely populated habitat (such as central India) has huge challenges to face in arriving at more protected habitat.  The implication is that protecting land in isolation without considering habitat linkages may not be enough to sustain populations.  The authors urge conservationists to move beyond a focus of increasing tiger populations, and consider land management for connectivity of areas between core tiger habitat as a high priority for maintaining healthy populations.