Tree frogs are found on every continent except Antarctica; worldwide, there are about 800 species of tree frogs, with three-quarters of them being found in Central and South America. Over 30 species live in the USA, and seven can be found in Canada, although in our area, we can only expect to find three of them – the Spring Peeper, Western Chorus Frog and Gray Tree Frog.
Weighing only a few grams, their arboreal (meaning they live in trees) lifestyle means they must be tiny to survive as these forest sprites (1-1.5 inches long) cling to leaves and small twigs. The largest tree frog in the world is found in Australia and is called the White-lipped Tree Frog, but even then, it is only 4-5 inches in length.
But how can they climb smooth surfaces and even cling to the underside of leaves? Their feet are modified such that the last bone (called a terminal phalanx) is shaped like a small claw, so they can grasp most surfaces. Toe pads, sort of like sticky pads, in the feet aid their arboreal lifestyle. Most are well camouflaged in gray, green or brown colours. However, some, such as our own Gray Tree Frog, can change colour from a drab gray to a shocking, beautiful pastel green!
One of the first signs of spring for me is not the robin but rather a tiny frog known as a Spring Peeper. Belonging to the same families as the exotic tree frogs of Central and South America, this diminutive little guy is hardy and overwinters frozen solid in our ponds and small lakes. To attract their mates, the males vocalize using unique sounds to entice the female. It makes an obvious ‘peeping’ sound starting around the beginning of April. How the female decides which has the best ‘voice’ is not known, but assuredly they can tell, for invariably, she chooses a male and mates and then lays her eggs in the water.
The Spring Peeper lives a bit longer than the Chorus Frog, generally surviving 3 or 4 years in the wild. The life cycle is similar, and the eggs are laid in the water. Up to 1000 eggs are laid and immediately fertilized by the males. In as little as one day, if conditions are ideal, the eggs hatch, and tiny tadpoles emerge and start to eat algae and small micro-organisms. Over the course of 6 to 7 weeks, the tadpoles continue to develop, using their gills to breathe underwater. Once they are adults, the gills disappear, and they become more terrestrial in nature.
The chorus frog will lay clusters of eggs in the water, up to 1500 eggs for each female. But why so many? Simple, everything eats them, small fish, birds, some mammals and many aquatic insects. The eggs hatch by midsummer, and the tadpoles grow until they approach the time when they will morph from a tadpole into a tailless adult. These tiny tadpoles are actually herbivores and dine on algae, but as they grow, they gradually eat larger and larger invertebrates. A lucky chorus frog will live only 2 or 3 years, but most perish when about one year old.
The Gray Tree Frog is long-lived in frog terms – 7 to 9 years is not uncommon. They are more acrobatic than the other tree frogs, able to leap easily between branches and leaves in search of food. After a noisy and aggressive stand-off with other males during the breeding cycle, the female chooses a male and mates, producing 1000 to 2000 eggs, which are laid in the water. Three to seven days later, the tadpoles hatch and, like the other species, start out eating algae but quickly change their diet to include various invertebrates. As an adult, it continues its carnivorous diet but adds young of its own species to the menu! The gardeners out there will be pleased to know they also dine on slugs and garden snails.
All these tiny tree frogs are in trouble worldwide, but for now, I cherish their return each spring!
Geoff Carpentier is a published author, expedition guide and environmental consultant. Visit Geoff online on LinkedIn, Facebook and Instagram.