Hyla regillaTree Frog call
The Pacific Tree Frog is one of our smallest but loudest amphibians of the Pacific Northwest. Belonging to the Hylidae family, this frog shares its small size, slim waist and long legs with only one other frog in its home range(the California Tree Frog Hyla californiae found only along the coast of Southern California). Pacific Tree Frogs live from southern B.C. south to California and east to Montana and Nevada. They have also been introduced to the Queen Charlotte Islands in B.C.
This frog can be recognised by its sticky toes pads, black stripes through each eye which extend to the shoulder, a V or Y-shaped mark between its eyes, light-colored belly and dark spots on back and legs. Its color varies from almost a bronze brown to a light lime green. Individuals can change color in green and brown tones in a few minutes. This color change is related to the temperature and amount of moisture in the air, not the background color as in most other amphibians and reptiles. This color change gives it the protection of camouflage as it hops and crawls about on low leaves, branches and on the ground in open forests and forest edges looking for flying and crawling insects to eat. This is an adaptable species who can live in coastal rainforests as well as ponds near treed areas of the interior dry belt.
Male tree frogs are smaller than females and have a dark throat patch, created by the stretching of the skin while vocalizing. Females grow to only about 10 cm (2 inches) from snout to vent.
Male frogs are territorial and protect their part of the pond from other males by repeating their two-toned mating call at night. This call can be heard from as far as several kilometers (a mile or more) away and attracts females who hop up to the males and must touch them to get their attention. When other males are near, they use a single note call, often referred to as the "rain call", often heard on rainy days as well as during mating season.
Fertilization of eggs is external and a clear jelly egg mass the size of a ping pong ball is laid attached to floating sticks and plants. Eggs take about 3 to 4 weeks to hatch, depending on water temperature. The cooler the water is, the longer they take to hatch.
Eggs are laid in early March to May (later at higher elevations) in temporary ponds where predators such as Brown Salamanders and Bullfrogs do not live or lay their eggs. By chosing temporary ponds instead of deep permanent ponds, Tree Frogs reduce the number of predators that may eat the tadpoles.
After eggs are laid, the parents hop back to open forests and forest edges, leaving the young to fend for themselves. Males can be heard calling almost year round in areas where frost does not occur. Adult frogs feed on flying and crawling insects and other invertebrates. Like most frogs, they will stuff creatures almost as long as themselves in their mouth!
Newly hatched tadpoles are about 1 cm ( 0.5 inch) long and grow quickly on a diet of algae and other pond plants. Their tiny mouths are located on the bottom of their heads and help them to scrape up bits of plant material. Tree Frog tadpoles are greyish-green and their intestines can be seen through the skin on their stomach. Their tail fins are well-developed and sit high on their body. Tadpoles eat a huge amount of food and produce much waste which becomes fertilizer for the pond plants they feed on.
Tadpoles are eaten by water bugs, diving beetles, salamander larvae and adults, and other frog tadpoles such as Bullfrogs.
When tadpoles are about 4.5 cm ( 1.75 inches) long, they begin to transform by first growing back legs, then front legs, enlarging both, then losing the tail to become froglets. This usually occurs by the beginning of September. During the final transformation, the tiny froglets do not eat as their mouth and digestive system is changing from a plant eater to an insect eater. Completely transformed froglets are about 1.5 cm long (about the size of an adult's baby fingernail.) and feed on tiny gnats, flies and mosquitoes at the pond edge.
Young frogs are mature at about one year of age and are eaten by raccoons, herons, mink, bullfrogs and other animals.
Pacific Tree Frogs use their sticky toe pads to climb bark, leaves and even glass and are sometimes found in moist areas in your home. Inside an aquarium, they jump with a splat!, all legs spread wide on landing.
Before you collect these tiny tadpoles to observe at home or in class, take the time to contact your state or provincial wildlife office for information as these frogs, at all life stages, are protected by law and require a permit to collect, transport and keep. This is to ensure that they will be here for future generations to enjoy. In the Greater Vancouver Area, B.C., contact Ministry of Environment 1-604-582-5200 for information. Permits cost $10.00.
Amphibians, as a group, are sensitive to changes in water quality and so are considered indicators of environmental cleanliness. Populations of all amphibians are declining world-wide even in un-touched areas such as Costa Rica. Scientists believe this is because of acid rain falling into ponds and lakes.
by Donna Hill B.Sc. B.Ed. 1998