Common Reed Frog (S/F)

Adult common reed frog. Photo by Kirkamon Cabello.

The common reed frog (Hyperolius viridiflavus) is a species of African reed frog in the tree frog family Hyperoliidae. It is highly variable in coloration, which may be indicative of over fifty subspecies, but some biologists believe that this frog may actually constitute a collection of around ten different but similar species. This amphibian is found near lakes and ponds in west-central Africa including Uganda, Rwanda, Burundi, South Sudan, and neighboring parts of Sudan, Kenya, Tanzania, the Democratic Republic of the Congo, and Ethiopia. It may possibly be found in parts of the Central African Republic, Chad, and Eritrea. This species is rated as Least Concern by the International Union for Conservation of Nature, meaning it is not in any immediate danger of extinction.

There is some evidence that the common reed frog may be capable of protogyny, as this was reported in a scientific journal in 1989. However, this was only observed once, and in a captive colony; biologists generally do not believe that this happens in the wild.

Proposed subspecies of this frog include:

  • Hyperolius viridiflavus spatzi
  • Hyperolius viridiflavus nitidulus
  • Hyperolius viridiflavus pallidus
  • Hyperolius viridiflavus pachydermus
  • Hyperolius viridiflavus viridiflavus
  • Hyperolius viridiflavus destefanii
  • Hyperolius viridiflavus variabilis
  • Hyperolius viridiflavus coerulescens
  • Hyperolius viridiflavus karissimbiensis
  • Hyperolius viridiflavus francoisi
  • Hyperolius viridiflavus undescribed ssp., Marsabit locality
  • Hyperolius viridiflavus pantherinus
  • Hyperolius viridiflavus ferniquei
  • Hyperolius viridiflavus sheldricki
  • Hyperolius viridiflavus rubripes
  • Hyperolius viridiflavus glandicolor
  • Hyperolius viridiflavus ommatostictus
  • Hyperolius viridiflavus goetzei
  • Hyperolius viridiflavus ngorongoroensis
  • Hyperolius viridiflavus renschi
  • Hyperolius viridiflavus mariae
  • Hyperolius viridiflavus reesi
  • Hyperolius viridiflavus bitaeniatus
  • Hyperolius viridiflavus rhodoscelis
  • Hyperolius viridiflavus nyassae
  • Hyperolius viridiflavus fumosus
  • Hyperolius viridiflavus taeniatus
  • Hyperolius viridiflavus marmoratus
  • Hyperolius viridiflavus verrucosus
  • Hyperolius viridiflavus parallelus
  • Hyperolius viridiflavus insignis
  • Hyperolius viridiflavus angolensis
  • Hyperolius viridiflavus alborufus
  • Hyperolius viridiflavus argentovittis
  • Hyperolius viridiflavus epheboides
  • Hyperolius viridiflavus marginatus
  • Hyperolius viridiflavus melanoleucus
  • Hyperolius viridiflavus pyrrhodictyon
  • Hyperolius viridiflavus aposematicus
  • Hyperolius viridiflavus rhodesianus
  • Hyperolius viridiflavus broadleyi
  • Hyperolius viridiflavus swynnertoni
  • Hyperolius viridiflavus albofasciatus

Further information about identifying the subspecies can be found here.

Description

This is not a very big frog, generally weighing around two grams (0.07 ounces) and measuring fourteen to thirty-three millimeters (0.55 to 1.3 inches) from snout to vent. There is some variability between subspecies, with some growing larger than others, but all fall within this range. Its snout is short, and the bulging eyes have horizontal pupils which help it locate and capture prey. The feet are webbed, and the gular flap is very large. These frogs have no external metatarsal tubercle, but all have a dark-colored lateral stripe which is the result of their black-pigmented abdominal muscle. However, this stripe may not be easily visible in frogs with heavily pigmented skin. In order to help the juveniles survive the harsh dry season, their skin on the dorsal and ventral sides is differentiated as to maximize the amount of water absorbed and retained.

Aside from the streak, coloration is extremely variable in the common reed frog, which may imply that there are more than fifty subspecies or that this animal is actually a collection of about ten related species. Its taxonomy is still hotly debated. In some populations, the color morphs are very distinct, but others have a wider range of diversity. Some have a base color of light green or brown, while others are more vibrant, and plenty of them show color patterning such as spots and stripes on the back. It is common for the feet to be brightly colored as well. The coloration is meant to warn away predators. During the dry season, the aestivating juveniles will become white as purine crystals build up in their skin.

Growth

Like with most frogs, this species starts its life as a tadpole, having only a head and tail. Its legs will develop as it reaches the juvenile stage, which occurs after about eight weeks. The juveniles have a different color scheme than adults called Phase J, which is light brown or green and often has a pair of lighter-colored lines down the back. Adult colors are called Phase F and are usually much brighter. Maturity is reached in three to twelve months, depending on the climate; they rapidly enter senescence after breeding just one time, and in the wild they rarely survive the ensuing dry season.

Sexual Dimorphism

The females of this species are slightly larger than the males, as well as being more colorful. This is an unusual trait, since in many animals the males are more brightly colored. Sexually mature males usually do not leave the Phase J coloration stage, while females progress to Phase F; this makes the males less visible.

Other differences include features of the anatomy; for example, the male has a large vocal sac which can be strongly dilated. He uses this to produce mating calls, while the female is mute. Females, on the other hand, have a transverse gular flap.

Habitat
Preferred Habitat

This frog has evolved well to thrive in a harsh environment where prolonged dry seasons spell death for most water-loving amphibians. It inhabits tropical savannas, and congregates near sources of fresh water such as wetlands and rivers; plant life is a necessary component of its habitat as well and it can survive in forests and on grasslands. It is commonly found among emerging vegetation and can survive on cultivated land, especially gardens where water is provided regularly. Ponds of any size, even temporary ones, can benefit the common reed frog’s populations by giving it a place to breed.

Common reed frogs are tolerant of mild altitude, and in Ethiopia can be found up to 2,400 meters above sea level.

Isla Nublar

The common reed frog was used by International Genetic Technologies as a gene donor in the de-extinction projects of Isla Nublar, but there is no evidence of live specimens being introduced to the wild on the island. If any were brought there, they most likely were maintained in the Visitors’ Centre laboratory until operations on the island halted in 1993. This species was rejected as a gene donor due to unwanted effects after this point and was not utilized again.

Isla Sorna

InGen utilized the DNA of the common reed frog as genetic filler in their de-extinction research. This was initially carried out at the Site B laboratory facilities on Isla Sorna; however, there is no evidence to suggest that live specimens of common reed frog were brought to the island or released into the wild. If any live frogs were kept on the island, they would have lived there between 1982 and 1995, after which point the island was evacuated and most of the laboratory materials were removed.

Other

This frog is native to Africa, and is found in the central-western part of the continent. It can be found on the tropical savannas and forests of Burundi, Rwanda, Uganda, and parts of the neighboring countries; it has been reported in northwest Ethiopia, west Kenya, southern Sudan, the northeast Democratic Republic of the Congo, and northwest Tanzania. It is probably also found in the eastern Central African Republic, but political unrest has made research difficult for the time being. Populations of this frog appear to be healthy and large, congregating around rivers, ponds, swamps, and marshes where the environment is ideal for them to breed.

Behavior and Ecology
Activity Patterns

The common reed frog is mostly diurnal, but courtship and territorial combat between males occurs at dusk and during the night. Its mating calls are a widely-recognizable component of African nocturnal sounds.

Diet and Feeding Behavior

Adults of this species are insectivorous and feed largely on small insects they find near water. They are visual hunters, using their large eyes and horizontal pupils to spot flies and other prey items before snatching them in their mouths. Like most frogs, their tongues are adhesive, helping them to handle food. According to Christine Bubac on AmphibiaWeb, the common reed frog is known to eat flies in the genera Calliphora, Drosophila, Lucilia, Musca, and Phormia. In captivity they will eat crickets, waxworms, earthworms, and other commercially-available fodder invertebrates.

Tadpoles, on the other hand, are herbivores and mostly eat algae; they will also live off the nutrients from their yolks for a brief time. Once they reach the juvenile stage, they are capable of eating insects, but during the dry season they aestivate and do not move, eat, urinate, or otherwise exhibit any noticeable behaviors. They survive off of their water reserves until the wet season comes again.

Social Behavior

Since water sources are at a premium on the savanna, frogs are often found in large numbers around any freshwater they can find. During the wet season, males are occupied with calling for females and will choose exposed spots to perform where females can best see them. Competition for these stages is fierce, and males will often engage in physical combat in order to secure their space. These territorial fights can last for a surprisingly long time. Such behaviors are not seen among the juveniles, whose existence is solely devoted to surviving the punishing dry season in order to mate.

Reproduction

Breeding occurs during the wet season, November to March. A breeding period usually lasts a few months, but varies depending on the frog’s subspecies. Common reed frogs are polygynandrous, mating many times throughout the season to maximize their reproductive success. As soon as water becomes available, males make their way to it, selecting the best spaces to perform mating calls for females. Since the frogs congregate around bodies of fresh water, even a temporary pond during the wet season can host choruses of common reed frogs which can be heard at dusk. Males put all of their efforts into attracting females, who prefer those males which can best defend their territories; these males are more likely to produce offspring which can withstand the hot, arid conditions of the dry season. Males must also be wary while performing, since they call in exposed areas and may attract the attention of predators such as birds and mammals. It is the female who initiates mating. She lays her eggs on submerged vegetation. A female reed frog may lay between 94 and 800 eggs, with the average being 330; she may lay a new clutch of eggs every ten to twenty days.

Under laboratory conditions, the common reed frog has been observed experiencing protogyny. Female frogs had their reproductive organs deteriorate and regrow as male organs, allowing these terminal-phase males to fertilize the eggs of those that were still female. Such a phenomenon would allow a population with mostly females to increase its reproductive output, but it has never been observed in the wild, suggesting that the conditions for protogyny are almost never met in nature.

The common reed frog provides no parental care once its eggs are laid, and not without reason. The eggs hatch after two to five days depending on environmental conditions, and the tadpoles mature into juveniles after eight weeks; full maturity is then achieved in four to twelve months. The reason for this extreme variability in maturation rate has to do with the frogs’ environment. West Africa experiences an extremely arid dry season, with many of the water sources disappearing. Frogs, as amphibians, need to remain moist in order to survive, and adult common reed frogs simply cannot stay wet enough during this time of year. In the wild, it is believed that close to 100% of adults die during the dry season. Juveniles that have grown old enough in time will begin to aestivate, entering into a sedentary state of hibernation in an effort to conserve water. They expend no energy moving or eating, and do not produce any waste. There are few signs that they are alive at all. Uniquely among frogs, they will aestivate on desiccated plants in the open, rather than burrowing into the ground.

Once the rains come, the juveniles that have survived will mature into adults. At this point they will venture forth toward whatever sources of water they can find, and the cycle will begin again.

Communication

The rapid and urgent life cycle of this frog means that virtually all of its forms of communication are devoted to reproductive rituals. Males produce two types of calls. The first is the mating call, which is a short metallic click. Females respond to the calls of males they like and initiate mating. The second is the territorial call; males use this to ward off rival males from their display perches, and is a longer, deeper sound. Larger frogs make louder calls.

Common reed frog calls are sometimes compared to the plinking of a xylophone, and are a characteristic part of the night sounds during the West African wet season. Since males are found in large numbers around ideal breeding sites, they form choruses. Females, on the other hand, cannot produce any sounds and are mute.

Ecological Interactions

One of the more common species of frog in its environment, the common reed frog is a notable component of the food web as it feeds on many types of flies. Most of its prey items are very small, but predatory pressure from reed frogs keeps these insect populations in check and provides relief to the plants and animals for which small flies would otherwise be a bother. Tadpoles, on the other hand, graze on algae in quiet pools of fresh water.

Common reed frogs are also a food item for many small predators. The tadpoles can be eaten by dragonfly nymphs and beetle larvae; adults are often preyed upon while near the water by turtles, fish, and other animals. African water snakes of the genus Lycodonomorphus are one of their major predators. To ward off visual predators, the common reed frog has warning coloration, but it is quite vulnerable to carnivorous animals that hunt by sound during the dusk and nighttime hours.

Cultural Significance
Symbolism

The common reed frog’s melodious calls are one of West Africa’s popular nighttime sounds. A common superstition surrounding the common reed frog is that it is fatally toxic to cattle, and that cattle sometimes die from eating this frog. This superstition originates among the Maasai people and is probably based on the common reed frog’s bright warning colors. Such patterns are common among poisonous frogs, but this species in particular is not especially dangerous.

Many people associate this frog species with protogyny, since it was famously observed changing sex from female to male and breeding after the transition was complete. This was relevant in genetic engineering as this trait was accidentally implemented in InGen animals. However, even though H. viridiflavus is popularly thought of as a protogynous amphibian, it was only ever observed undergoing this process once in a laboratory. It has never been observed in the wild, meaning this is probably a very rare occurrence in nature.

In Captivity

Both in the laboratory and as a pet, this frog has been successfully kept in captivity and is occasionally seen in the international pet trade. The wide range of colors seen in the females makes them very attractive, but unfortunately, they do not live for much longer than a year; even though they can be given the conditions necessary for their survival in a captive environment, they have evolved to die off and make room for the next generation anyway. Frogs that live through a breeding season will undergo rapid aging and will inevitably die. For this reason, they are not popular pets.

Among people who do keep them, breeding is necessary in order for the frogs to last more than a year or two. They require an aquatic environment, inhabiting freshwater, and as their name suggests they prefer to live among reeds. Eggs are laid on submerged plants, with live rather than artificial plants being ideal. A twenty-four-inch aquarium can be used to house six to eight adult frogs. Warm temperatures are necessary as they are native to the tropics and cannot withstand cold; breeders recommend daytime temperatures of 24 to 26 degrees Celsius and nighttime temperatures of 20 to 22 degrees. Relative humidity should be around 40% to 60%, and the frogs will need a moist but not soaked place to rest on land as well as a large pool of water to swim and breed in. The substrate should ideally be small, smooth pebbles or orchid bark, topped with two inches of live or fresh sphagnum moss.

Science

Common reed frogs have been studied in the field and under laboratory conditions to learn about their behavior and reproductive cycle. They are a highly interesting species of frog, having developed unique evolutionary adaptations to the harsh conditions of West Africa’s dry season. Among these adaptations are its highly variable growth rate, juvenile aestivation period, and near-total mortality rate of post-reproductive adults.

A fascinating discovery regrading the common reed frog is its apparent genetic inclination toward protogyny, a phenomenon in which a female animal naturally transforms into a male. This was reported by scientists T.U. Grafe and K.E. Linsenmair in a 1989 edition of Copeia (now titled Ichthyology & Herpetology), with female frog specimens of the subspecies H. v. ommatostictus becoming male under laboratory conditions and fertilizing the eggs of other females. This has never been observed in the wild, and these results have never been repeated in a laboratory either. Even though the frog does appear to have the ability to experience protogyny, the conditions under which the transformation is triggered appear to be difficult to replicate and rarely occur in nature.

Politics

There is no known political significance to the common reed frog.

Resources

While the common reed frog is sometimes sold as a pet, its short lifespan makes it unpopular. It has more use as a laboratory specimen. In particular, it has gained notoriety due to its use by InGen geneticist Dr. Henry Wu during the 1990s; among other amphibian species, he utilized this frog’s DNA as a filler material for de-extinction. Supposed “junk” DNA sequences were removed from the common reed frog genome and applied to the genomes of extinct species in order to reconstruct them.

Common reed frog DNA was first utilized to repair the decayed gene sequences of Velociraptor in 1991 following the failure of Dendrobates leucomelas (yellow-banded poison dart frog) genes to integrate successfully. The genes selected were assumed to be functionally the same as those they were replacing, but in 1993 it was discovered that the selected genes coded for protogyny. As this did successfully integrate into the genomes of the animals it was applied to, it resulted in animal species that could change sex from female to male in order to breed. Because of this unwanted side effect, the common reed frog is not considered a preferred source of donor genes.

Safety

Despite its warning colors, the common reed frog is not known to have any harmful effects on humans and is safe to handle. Adult males will be aggressive toward one another, but cannot hurt a human. You are in no danger from this animal; it is only a frog.