Why Do Tree Frogs Lay Eggs on the Ground Instead of on Tree Branches Where They Usually Live?

Why Do Tree Frogs Lay Eggs on the Ground Instead of on Tree Branches Where They Usually Live?
(Photo : Wikimedia Commons/LiquidGhoul)

Tree frogs leave their comfort zone or their home when laying their eggs. Instead of laying on the trees' branches where they live, the amphibians have to go to the ground and place their foam nest there to lay their eggs.

Why Tree Frogs Lay Eggs on the Ground?

A team of researchers from Nagoya University in Japan followed the spawning behavior of forest green tree frog (Zhangixalus arboreus) in a new study titled "Arboreal or terrestrial: Oviposition site of Zhangixalus frogs affects the thermal function of foam nests." According to lead researcher Yukio Ichioka, they found areas where the frog's foam nests were on the ground around ponds, even if there were trees suitable for building bubble nests. They wondered why the frogs chose to lay their eggs on the ground, where they were at high risk of predation by their natural enemies.

To find an answer, the researchers compared the temperatures inside a sample of ground-based nests and a sample of nests atop tree branches, and the ambient temperature. By calculating the proportion of eggs that developed into tadpoles and those that did not, they were also able to determine the hatchability rate of eggs.

Ichioka and Professor Hisashi Kajimura discovered that tree frogs have a somewhat intricate method for laying their eggs. The interior temperature of the ground-based foam nests was higher than the ambient temperature during periods of low air temperature.

The effect of heat retention was most noticeable at night when the temperature was lower. The likelihood of the eggs hatching was enhanced by the above-ground foam nests, which shielded them from freezing conditions. The fact that the eggs' hatchability rate was higher at ground level than it was at tree level proved to be the reason tree frogs prefer to lay their eggs on the ground.

Their results point to the hitherto unrecognized adaptive value of ground-nesting tree frogs. That is, they are protected from the cold by depositing their eggs on the ground. Given that forest green tree frogs can occasionally reside in regions that are high above sea level, this behavior is significant.

According to Kajimura, these results will significantly advance their knowledge of the evolution of amphibian spawning behavior. They will also provide insight into how forest creatures adjust to the warmer climate.

The study is significant for the connections between animal behavior and climate, and it can help comprehend how behavior evolved, particularly in the context of the modern world, the professor added.

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What Are Tree Frogs?

Tree frogs are a broad family of frogs comprising more than 800 species. Tree frogs do not always reside in trees.

Instead, their shared trait has to do with their feet; specifically, the terminal phalanx, the last bone in each toe, resembles a claw. Tree frogs also have toe pads to aid in their climbing, and many of them have additional bone elements in their toes.

While there are many different hues of tree frogs, the majority of species found in the US are green, gray, or brown. Some can change color like chameleons, such as the squirrel tree frog (Hyla squirella).

Tree frogs come in a variety of sizes, but the majority of arboreal species are quite small due to their reliance on thin branches and leaves to support their body weight. The largest tree frog in the world is the white-lipped tree frog (Litoria infrafrenata), which is found in Australia and Oceania and measures 4 to 5.5 inches (10 to 14 cm) in length. With a length of 1.5 to 5 inches (3.8 to 12.7 cm), the non-native Cuban tree frog is the largest tree frog in the United States. Less than an inch (2.5 centimeters) is the length of the tiniest tree frog in the world!