Soay sheep on the island of St. Kilda, Scotland.
For sheep, having a strong immune system may be the key to living a long life, but at the cost of reproductive success, research has shown.
The work looked at an unmanaged population of Soay Sheep (Ovis aries), a primitive breed living on the remote island of Hirta, to the far west of Scotland.
Dr Andrea Graham, an ecologist from Princeton University, and colleagues from the University of Edinburgh studied levels of antibodies in the sheep’s blood plasma over an 11 year period. The results showed that ewes with high levels of antibodies tended to live longer than those with lower levels.
Ewes with higher levels of antibodies tended to live as long as 12 to 15 years, whilst those with lower levels tended to only live for less than five. You might expect natural selection to favour the healthiest ewes, leading to a reduction in the numbers of those with lower antibody levels.
It turns out that the ewes with a weaker immune system are more likely to produce lambs every year than those with a stronger immune system. So the total lifetime number of offspring produced by both the short and long-living ewes is similar. Those with a shorter lifespan are more prolific, which prevents them dying out.
Benjamin Thompson
Benjamin Thompson is undertaking a work placement at the Wellcome Trust.
Image credit: jonesor on Flickr
Filed under: Animal Health, Bites Tagged: Dr Andrea Graham, Immunity, Princeton University, Sheep, University of Edinburgh
