Lizard Mothers Turn Protective When Predators Lurk, Study
In a rare show of maternal care in lizards, female Asian long-tailed skinks actively deter snakes from consuming their eggs on Taiwan’s Orchid Island.
AsianScientist (Feb. 6, 2013) - In a rare show of maternal care in lizards, female Asian long-tailed skinks (Eutropis longicaudata) actively deter snakes from consuming their eggs on Taiwan's Orchid Island.
On this island, female skinks attack egg-eating snakes (Oligodon formosanus) that attempt to raid their nests and consume their eggs.
Dr. David Pike, a lecturer at James Cook University's School of Marine and Tropical Biology in Australia and one of the scientists involved in the study, said that he expects that people may be surprised that lizards could deter a predator as formidable as a snake.
"Many snake species readily eat lizards, so with the species we studied, we found we were either dealing with a very unique lizard or very wimpy snakes," he said.
It turns out that the physical attributes of the two were also a factor in the phenomenon.
"The lizards are also pretty big and the snakes don't get very big. This allows the lizards to attack snakes without fear of being eaten," said Pike.
But the most interesting part of this unusual lizard-snake relationship was that the Asian long-tailed skink only protected its eggs on Orchid Island.
On nearby islands, this same lizard species lays the eggs and leaves them to face nature's fate. In fact, almost all animal species expressing parental care are known to do so throughout their entire geographical range, which makes the Asian long-tail skink rather unusual.
Pike explains that this behavior evolved on Orchid Island because mothers who protect their eggs have more babies than mothers who abandon them.
When researchers transferred individual lizards from their home island with very few snakes to Orchid Island, which has lots of snakes, female lizards changed their behavior and became good mothers. In contrast, nest-defending mothers who were moved to islands with few snakes decided not to guard their eggs, because of the small chance that they would eaten by snakes.
How do nesting females decide whether or not to guard their eggs? The authors have various explanations for the phenomenon they observed on Orchid Island.
Even lizards raised in captivity that had never encountered predators before adulthood expressed maternal care, which rules out predator encounters during ontogeny as an explanation. Individual experience with predators immediately before nesting is a likely mechanism, they say. The authors also raise the interesting possibility that the lizards are using social behavior of others as a cue to their own behavior.
The article can be found at: Huang W-S et al. (2012) Predation drives interpopulation differences in parental care expression.
Source: JCU; Photo: University of Hong Kong.
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