Site-fidelity in a declining population of migratory wildebeest

Background/Question/Methods

Site fidelity to breeding habitat shapes the spatial structure of migratory populations and constrains its capacity to respond to heterogeneity and change in the landscape. Because population structure defines both management units and evolutionarily significant units, site fidelity can be a critical aspect of migratory behavior with consequences for population viability or recovery.  However, in many species, characterizing site fidelity is challenging because it requires following a large portion of the population over long distances and across seasons. We used a non-invasive computer-assisted photographic identification method to examine site-fidelity patterns in a declining population of migratory wildebeest (Connochaetes taurinus) in the Tarangire Ecosystem of Northern Tanzania. This landscape is rapidly changing due to the expansion of agricultural cultivation and human settlements within the migratory pathways and breeding sites of wildebeest. 

Results/Conclusions

We identified 5560 adult wildebeest across three seasons (2005-2007) and three possible breeding sites. Based on 318 recaptures across seasons, we found strong site-fidelity to breeding areas in wildebeest, with only 14% of individuals moving to different breeding areas between years.  Females were over twice as likely to migrate to different breeding sites than males, suggesting that social mechanisms may play a role in decisions about where to migrate from year to year in wildebeest.