Editor: Tim Halliday
Primary and secondary phenology. Does it pay a frog to spawn early?
Article first published online: 18 MAY 2009
© 2009 The Authors. Journal compilation © 2009 The Zoological Society of London
Journal of Zoology
Volume 279, Issue 1, pages 64–70, September 2009
How to Cite
Loman, J. (2009), Primary and secondary phenology. Does it pay a frog to spawn early?. Journal of Zoology, 279: 64–70. doi: 10.1111/j.1469-7998.2009.00589.x
- Issue published online: 20 AUG 2009
- Article first published online: 18 MAY 2009
- Received 12 February 2009; revised 31 March 2009; accepted 31 March 2009
- breeding time;
- R. temporaria
This study examines the consequences of variation in the laying and hatching date for the time of metamorphosis in the common frog Rana temporaria. Field data are presented showing that eggs laid early tend to take longer to develop. Thus, the time advantage for early eggs is reduced at the time of hatching. There was an among-year variation in this phenomenon; it was not manifest in a phenologically late year. Also, field data revealed that mortality due to pond freezing is a real risk for early laid eggs. Finally, two experiments in tanks analyse the effects of hatching date variation for the time of metamorphosis. (1) When hatching was experimentally delayed by 7 or 11 days, this resulted in later metamorphosis, however, by only 2 and 5 days, respectively. (2a) When tadpoles from the same pond that naturally hatched at different times were compared, it was found that a hatching time difference of 6 days resulted in later metamorphosis by 2 days only. (2b) A comparison of tadpoles from two different ponds that hatched 11 days apart also resulted in only 2 days' difference in metamorphosis. In this case, the later but faster developing tadpoles metamorphosed at a smaller size. I suggest that eggs from these two ponds differed genetically in the growth and development strategy. Despite the obvious risks, and the moderate gain in terms of early metamorphosis, frogs breed dangerously early in spring. Possible reasons for this are discussed. These include external selective forces that promote early metamorphosis (also at a high cost), within-pond competition among tadpoles with an advantage for early and large tadpoles and finally factors relating to mate choice at the breeding site.