Australasian Science: Australia's authority on science since 1938

City lizards not coping with climate change

Human-modified habitats are becoming too warm for successful egg incubation.

Lizards living in their natural habitats cope better with the effects of climate change than those living in human-modified habitats, researchers from James Cook University have found.

Dr David Pike, from JCU’s School of Marine and Tropical Biology said that 10 years ago, lizards born in human-modified habitats were larger, grew faster, and survived better than their counterparts born in natural habitats.

However, climate change was increasing the temperatures of lizard nests located in human-modified habitats faster than nests located in natural habitats, he said.

“The end result is that temperatures in human-modified habitats are becoming too warm for successful egg incubation,” Dr Pike said.

“Lizard eggs require very specific incubation temperatures to hatch,” he said.

“Temperatures that are too low or too high will kill the eggs. By selecting nest sites that maintain temperatures appropriate for egg incubation, female lizards can ensure that their eggs will hatch.

“But, if the temperatures of nesting sites are becoming warmer due to climate change, this could influence the ability of females to successfully reproduce.”

Dr Pike said the researchers used long-term data from a tropical lizard, the long-tailed skink, or Eutropis longicaudata, to show that the creature’s preferred nesting habitat was being affected by climate change.

“Long-tailed skinks on Orchid Island in Taiwan either lay eggs beneath rocks in natural habitat or inside a concrete wall in human-modified habitat.

“When we started this work over a decade ago, the concrete wall was by far the best nesting site.

“The warm nest temperatures there produced baby lizards that were larger, grew faster, and survived better than their counterparts born in natural habitat.”

Dr Pike said that climate change, however, was having a detrimental impact on the human-modified nesting sites.

“Female lizards want to lay their eggs in the best site possible; generally, this means choosing sites with higher temperatures.

“But, if temperatures become too high the eggs will die before hatching.

“Our study shows that lizard nest temperatures are reaching this upper limit in human-modified habitats because of climate change, but that nest temperatures in natural habitats are still good for lizard nesting.

“Even very small temperature increases can have a detrimental impact on lizard reproduction.

“Our study highlights how different human environmental impacts can affect animals; by creating the concrete wall, humans initially provided an excellent nesting site for lizards, but human-induced climate change has caused this habitat to no longer be suitable for nesting.”

Dr Pike said the research also demonstrated climate change could encourage “ecological traps”.

“Ecological traps are habitats that are preferred by animals, but have negative consequences for using them. In our study, the concrete wall is very attractive for nesting lizards, but climate change has caused this habitat to become a poor site for nesting.”