Tracking the seasons: the internal calendars of vertebrates

UMMS Affiliation

Department of Neurology

Publication Date


Document Type



Adaptation, Physiological; Animals; Biological Clocks; Environment; *Seasons; Vertebrates


Life Sciences | Medicine and Health Sciences


Animals have evolved many season-specific behavioural and physiological adaptations that allow them to both cope with and exploit the cyclic annual environment. Two classes of endogenous annual timekeeping mechanisms enable animals to track, anticipate and prepare for the seasons: a timer that measures an interval of several months and a clock that oscillates with a period of approximately a year. Here, we discuss the basic properties and biological substrates of these timekeeping mechanisms, as well as their reliance on, and encoding of environmental cues to accurately time seasonal events. While the separate classification of interval timers and circannual clocks has elucidated important differences in their underlying properties, comparative physiological investigations, especially those regarding seasonal prolactin secretions, hint at the possibility of common substrates.

DOI of Published Version



Philos Trans R Soc Lond B Biol Sci. 2008 Jan 27;363(1490):341-61. Link to article on publisher's site

Journal/Book/Conference Title

Philosophical transactions of the Royal Society of London. Series B, Biological sciences

Related Resources

Link to Article in PubMed

PubMed ID