Re: Why Rana arvalis turn blue?
Posted: Sun Feb 26, 2017 2:47 pm
Here in Denmark it varies from year to year - and seemingly also from population to population - to which extent they turn blue, from no more than temporaria to electric.
I don't know of any studies documenting it but it is widely acknowledged that this indeed correlates to weather and water temperature. This also corresponds with my own experience.
Further, in my experience it seems there is a second correlation with the level of breeding activity. When conditions are ideal we experience large choruses of blue males for a day or two whereas in less optimal conditions breeding seems to be spread out across a few days more with less activity and ditto colour each day.
I don't know of any studies documenting it but it is widely acknowledged that this indeed correlates to weather and water temperature. This also corresponds with my own experience.
Further, in my experience it seems there is a second correlation with the level of breeding activity. When conditions are ideal we experience large choruses of blue males for a day or two whereas in less optimal conditions breeding seems to be spread out across a few days more with less activity and ditto colour each day.