How Do Tree Frogs Stick to Things? Tree Frog Facts

Tree frogs stick to leaves, branches and even windows with pads on the tips of their fingers and toes. The pads grip by wet adhesion: a thin layer of fluid between the pad and the surface holds on through suction or capillary forces, much like a wet sheet of glass sticking to a table. That’s different from geckos, which use dry adhesion. Tree frogs are also usually small and light, which makes clinging easier.

Here’s how the pads work, plus a few of the most interesting tree frogs.

What is a tree frog? #

A tree frog is any frog that spends a major part of its life in trees. It’s a lifestyle, not a single family. According to Wikipedia’s tree frog article, tree frogs come from five main groups:

The true tree frogs are a big family, with more than 1,000 species. Many have forward-facing eyes that give them binocular vision, handy for judging jumps between branches. Because these groups evolved separately, their similar look is a case of convergent evolution: climbing in trees favors the same body plan again and again. Glass frogs are one of the five groups, and among the strangest.

How do tree frogs stick to things? #

With adhesive pads, the well-developed discs at the tips of their fingers and toes. The pads work by wet adhesion. Wikipedia’s article on arboreal locomotion describes wet adhesion as common in tree frogs and arboreal salamanders, working either by suction or by capillary adhesion.

Capillary adhesion is the same force that makes two wet panes of glass hard to pull apart. A thin film of fluid between the toe pad and a surface creates a strong grip, while still letting the frog peel a toe off when it wants to move. That’s why a tree frog can walk across a wet leaf or cling to a window without sliding off.

Geckos climb differently. Their feet use dry adhesion, which relies on weak molecular attractions called van der Waals forces rather than fluid. Tree frogs rely on moisture instead, which works well in the humid places most of them live.

Can tree frogs grip like hands? #

Some can. Frogs in the genus Chiromantis can oppose two fingers against the other two, giving them a vise-like grip on thin branches, a bit like a thumb.

How big are tree frogs? #

Usually tiny, since the branches they live on have to hold their weight. Most are small and slender, though a few species grow past 10 cm (4 inches). Being light is part of how the toe pads can hold them: a small frog has a lot of pad area for its weight.

What is the gray treefrog? #

The gray treefrog, Dryophytes versicolor, is one of the best-known tree frogs in eastern North America. It lives across much of the eastern United States and southeastern Canada and is small, typically 1.5 to 2 inches (3.8 to 5.1 cm) long.

Two things make it remarkable:

• It changes color. A gray treefrog can shift from nearly black to nearly white depending on its surroundings, though more slowly than a chameleon.
• It survives freezing. Gray treefrogs can survive their body fluids freezing at temperatures as low as −8 °C (18 °F), which is how they get through northern winters.

Males call with a trill of 16 to 34 pulses per second. That’s how you tell it apart from the nearly identical Cope’s gray treefrog, which trills faster, at 34 to 60 pulses. Females don’t call.

What is the red-eyed tree frog? #

The red-eyed tree frog, Agalychnis callidryas, is the frog on a thousand posters: bright green with huge red eyes, orange feet and blue and yellow stripes on its sides. It lives in Central America from northeastern Honduras to northern Colombia. Males reach about 2 inches and females about 3.

Despite the colors, it isn’t poisonous. During the day it sleeps with its eyes closed and its colorful parts tucked away, looking like a green leaf. If a predator disturbs it, it flashes the red eyes and bright flanks, which can startle the attacker long enough for the frog to escape.

Its eggs are just as clever. Females lay about 40 eggs on the underside of a leaf over a pond. If a snake starts eating the clutch, the embryos can sense the vibrations and hatch early, dropping into the water below to escape. The species is listed as Least Concern, though habitat loss, chytrid fungus and the pet trade are threats.

Do all tree frogs lay eggs in water? #

No. Many lay eggs in or near water, but some species build foam nests on leaves, and others lay eggs on leaves hanging over water so the tadpoles fall in when they hatch, as red-eyed tree frogs and glass frogs do. Tree frogs rarely come down to the ground except to breed.

Are tree frogs poisonous? #

Most aren’t dangerously toxic to people, and some brightly colored ones, like the red-eyed tree frog, aren’t poisonous at all. The frogs famous for toxins are the poison dart frogs, a different family. Still, amphibian skin can carry irritating secretions and germs, so it’s sensible to wash your hands after touching any frog and to leave wild ones alone.

Is there a tree frog in Frog Pond? #

Yes. In Frog Pond, a cozy idle game about building a pond full of frogs, the Tree Frog is the third worker tier, described as having “Sticky toes, longer reach.” It arrives at Pond Level 4, costs 1,100 coins and makes 8 coins a second, and a rare Jade Tree Frog variant can hatch from a Mystery Egg to boost the tier by 50%. The game’s other frogs include bullfrogs, glass frogs and poison darts.

Frequently asked questions #

Why do tree frogs stick to windows? #

Their toe pads grip smooth surfaces by wet adhesion, using a thin film of fluid. Smooth glass gives the pads lots of contact, so windows are easy for them to climb.

Are tree frogs sticky to touch? #

Their skin feels moist rather than sticky. The grip comes from the specialized pads on their toes, not from glue on their bodies.

How do tree frogs survive winter? #

It depends on the species. The gray treefrog can survive having its body fluids freeze at temperatures down to −8 °C.

What is the biggest tree frog? #

Most tree frogs are small, but a few species grow longer than 10 cm (4 inches).