“Fluctuations in hormones and behaviour are part of a delicate biological orchestra that is crucial to life.” Professor Simone Meddle

Scientists from the Universities of Edinburgh and Manchester studying sheep have researched how the brain responds to short and long days to allow animals to adapt to changing conditions such as growing thicker coats and breeding cycles .

Professor Simone Meddle, who co-led the research from the University of Edinburgh’s Roslin Institute, said:

“Fluctuations in hormones and behaviour are part of a delicate biological orchestra that is crucial to life. Many animals depend on seasonal changes in their biology to survive and our findings are a crucial part of the puzzle to understand the underlying processes.”

Circadian rhythms are influenced by genetics. The scientists studied an endocrine gland attached to the brain called the pituitary gland in sheep experiencing short or long lengths of day.

In summer when nights are long, the brain generates hormones that cause a cascade of gene activity leading to biological characteristics associated with summer.

When nights are short in winter, the switch is flipped – night-time hormones are released for longer, triggering biological processes linked to winter.

Professor Andrew Loudon, who co-led the study from the University of Manchester, said:

“The genetic ‘flip-flop’ timer we have identified is key to functions such as fertility as sheep transition between winter and summer. We speculate that this genetic timer is likely to be fundamental to yearly changes in many species.”

The study, published in Nature Communications, was funded by the Biotechnology and Biological Sciences Research Council.