Climate change is affecting the breeding cycles of toads and salamanders, researchers reported on Tuesday, in the first published evidence of such changes on amphibians.
They documented that two species were breeding later in the autumn than in years past, and two others were breeding earlier in the winter.
Their study, published in the Proceedings of the Royal Society B, adds to a growing body of evidence that climate change is affecting animals.
Other studies have shown some birds in North America and Europe are moving northwards as temperatures rise.
Brian Todd of the University of California, Davis and colleagues set up a net around a wetland in South Carolina starting 30 years ago, and trapped the animals that came and went.
"We analysed 30 years of data on the reproductive timing of 10 amphibian species ... and found the first evidence of delayed breeding associated with climate change," they wrote in their report.
"We also found earlier breeding in two species. The rates of change in reproductive timing in our study are among the fastest reported for any ecological events," they added.
The changes coincided with a 1.2 degree C (2.16 degrees F)warming in average overnight temperatures at the site.
"Our results highlight the sensitivity of amphibians to environmental change and provide cause for concern in the face of continued climate warming," Todd and colleagues concluded.
The dwarf salamander Eurycea quadridigitata and marbled salamander Ambystoma opacum, both autumn-breeding species, arrived significantly later in recent years than at the beginning of the study, they found.
The tiger salamander Ambystoma tigrinum and the Pseudacris ornata or ornate chorus frog, both winter-breeding species, were showing up earlier to breed.
Six other species of frogs and toads did not change the timing of their breeding, the researchers said.
