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Primary and secondary phenology. Does it pay a frog to breed early?

Publiceringsår: 2009
Språk: Engelska
Sidor: 64-70
Publikation/Tidskrift/Serie: Journal of Zoology
Volym: 279
Nummer: 1
Dokumenttyp: Artikel i tidskrift
Förlag: Wiley-Blackwell


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.


  • Biological Sciences
  • metamorphosis
  • hatching
  • freezing
  • breeding time
  • egg
  • R. temporaria.


  • ISSN: 0952-8369

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