Migrating animals carry genes between populations. Migration is therefore the natural antidote to an accumulation of adverse inbreeding effects in small populations. But migrants may also carry disease. Managers therefore rest uneasily on the horns of a dilemma. Actions that encourage migration may reduce population endangerment from inbreeding but risk epidemics of disease. Actions that discourage migration may reduce population endangerment from disease but risk genetic meltdown.
There is no simple resolution of this dilemma. However, we suggest that if science can determine individual “strategies” in migration – who goes, when, where and, especially, why – managers could then manipulate conditions to encourage migration in some circumstances and discourage it in others according to prevailing risks.
To understand individual strategy in migration, we have again chosen Rocky Mountain bighorn sheep as our study species. Our research site is a complex of native populations inhabiting the Canadian Rockies in southwestern Alberta. MOCSI research biologist, Dr. Jack Hogg, and co-principal investigator, Dr. Kathreen Ruckstuhl, were recently awarded a three-year $300,000 grant to support the work. The grant will support deployment of 23 GPS collars in each of the next three years (2006-2008). The GPS data will allow us to comprehensively describe the movement patterns of migrants in the study area. In addition, we will establish three backcountry base camps from which teams of observers will monitor the behavior and success of collared and un-collared migrants in their destination populations.
Preliminary work by our team indicates that breeding migrations by rams are the primary source of both gene and disease flow in bighorn and that male mating strategy operates on a spatial scale encompassing many different populations and many hundred square kilometers. Much more remains to be discovered. For example, the purpose of female migratory movements remains obscure.