Telomeres, workload and life-history in great tits

Ageing and the effects of increased workload in great titsA new measurement to quantify variation in quality and rate of ageing between individuals is telomere length. Telomeres are a piece of DNA at the end of chromosomes, and they protect the other DNA. In many species shortening of telomere length with increasing age was demonstrated. This shortening is accelerated by processes that also decrease life expectancy.In this project we discovered that telomeres of great tits differ from telomeres in humans and other bird species. They seem to have two classes of telomeres: long telomeres that do not shorten with increasing age and shorter telomeres that do shorten with age. So great tits have a group of ultra-long telomeres that behave differently, but why remains a mystery.In great tits we used the shorter telomeres as measurement for ageing. We found that great tits that are most successful in reproduction also better maintained their telomeres. This suggests that these successful great tits are of better quality. This effect was not observed yet, and more research into the causes could give fundamental insights about ageing.In a number of male great tits we increased the workload, because we equipped them with a backpack with the size of a transmitter. We found no long term effects of the backpacks on telomere shortening or fitness parameters, but there were some short term effects which suggested small behavioural changes. More often birds receive equipment such as transmitters, and with our results we show that these could be used without negative consequences on the long term in great tits