ONE LIFE: Frogs and toads

19 March 2021

Frogs and toads are the most diverse and widespread of the three amphibian orders. Unlike the other amphibians (salamanders, newts and caecilians), adult frogs and toads have no tails, but they do have many adaptations to jumping, such as long hind legs, elongated ankle bones and a short vertebral column.

Frogs and toads are more complex than you might think.

There are over 5000 frog species in the world and each one has a unique call, and some frog calls can be heard a mile away. Frogs don’t need to drink water as they absorb it through their skin, and while some frogs’ skin contains mild toxins, some such as the poison dart frogs, are deadly.

They like to play, are capable of learning, and are dedicated parents. Around the world frogs and toads are being kept in captive conditions that fail to meet their needs and give them the complex environment they need to thrive. They are also used extensively in experimentation without care for their experience of pain.

Let’s see frogs and toads differently.

Frogs are dedicated parents

Frogs may not be the first animal that springs to mind when we think of parental care, yet evidence shows that many species are dedicated parents.

The strawberry poison dart frogs are a super parent pairing. After females lay their eggs on the rainforest floor, the finger-nail-sized frog dads keep guard from predators and urinate on the eggs daily to keep them moist. When they hatch, the tadpoles must be separated to prevent them from eating each other. To keep them all safe, mother frogs transport each baby, individually, on her back up into trees to find a safe pool of water in which to deposit them separately.

She then visits each individual nursery pool every day for approximately 50 days to lay an unfertilised egg in the pools to keep her babies fed. Meanwhile, father frogs continuously guard the territory to stop rivals finding the babies.

The African bullfrog is a super dad. They wait to breed until after heavy rainfall and lay their eggs in the shallows of the temporary ponds and puddles left behind. Once hatched, the male bullfrogs will watch over their brood until the tadpoles metamorphose. The males don’t only defend their offspring from predators, they also defend them from being stranded without water. If their small pond begins to dry up, the male bullfrog will work quickly to dig a pathway to another water source.

Midwife toads make brilliant fathers, the males carry a string of fertilised eggs around their hind legs. This behaviour keeps the eggs safe and out of the way of predators until they are ready to hatch. When they are ready, the male takes them to shallow water, where the tadpoles hatch out of the eggs. Midwife toads are hardy animals, and can even live in the snowy landscape of the Pyrenees. Although named toads, they are actually frogs!

Male Darwin's frogs help with child-rearing by swallowing their tadpoles. When Darwin's frog tadpoles hatch, their father swallows them. The tadpoles then stay in their father's vocal sac for around 60 days, whilst they grow and metamorphosise into tiny frogs. The father then coughs up the fully formed frogs. This extraordinary behaviour means more tadpoles survive and develop into frogs, giving them the best chance to reach adulthood.

Frogs like to play

Adult poison dart frogs are toxic to predators. Their poisonous skin allows them to be more active and social during the day. Adults will often engage in brief wrestling bouts with others, regardless of sex. This behaviour appears to be a form of play. 

Vietnamese mossy frog tadpoles ‘ride’ bubbles in their tank. These tadpoles have been observed repeatedly riding the bubbles from an airstone in the bottom of their tank, all the way up to the top. This is clearly fun, and the tadpoles are engaging in play.

Frogs are good learners

The Túngara frog can learn to use acoustic signals to find their way. The Túngara frog can be trained to distinguish between two arbitrary sounds; one leading to a door to their shelter, and the other to a dead-end. When the sounds are then reversed, the frogs can reverse their learning, and learn to associate the other sound with their shelter. This ability to reverse their learning indicates a degree of intelligence in frogs.

Iberian green frog tadpoles learn information from others about potential new predators. Tadpoles reduce their movements when they smell a predator nearby. Tadpoles of the Iberian green frog will also use information (alarm cues) from other tadpoles. In fact, when they receive alarm cues from other tadpoles, they reduce their movement even more. They can even learn about new predators from other tadpoles.

Toads are incredible navigators

Toads use both geometrical information (shapes of walls and terrain) and features of their environment (such as colours and smells) to navigate themselves and get where they want to go. When the information conflicts, they will focus on the geometrical information around them. Toads are, therefore, able to use similar mechanisms for navigation as birds, fish and us mammals do. 

Toads may be able to predict earthquakes

Toads that were 74km away from an earthquake exhibited dramatic changes in behaviour five days before the earthquake, and for several days after. In the five days before the earthquake, male toads and mating pairs of toads disappeared from the breeding ground. They did not reappear until two days after the earthquake. No spawning occurred during this time either. These behaviours are highly unusual for toads. It appears that the toads sensed the earthquake and moved away to hide.

Frogs can jump more than 20 times their body length

A frog's powerful jump allows them to escape quickly from predators. The best jumpers can jump over 20 times their body length. That is the equivalent of an adult human jumping over 37 metres. The South African sharp-nosed frog is only 8cm long, but they can jump nearly 3.5m; 44 times their body length. Not all frogs jump though. The waxy tree frog walks like a lizard. Toads tend to walk too, and they are generally much slower than frogs at getting about.

Frogs are a key indicator of the health of our environment

The importance of frogs in the natural world cannot be underestimated and throughout their lives they pay a key role in the health of our natural environment.

Frogs are critically important within the food chain as both predator and prey. The tadpoles feed on algae, helping to regulate algal blooms, reducing the chances of algal contamination, and keeping our waterways clean. They are also excellent pest controllers, competing with mosquito larvae for food sources and eating millions upon millions of larvae and adult mosquitos that can potentially transmit diseases including Dengue fever, Malaria, West Nile fever and Zika.

Tadpoles and adult frogs are also a large food source for a huge number of fish, mammals, birds and reptiles. In parts of the world where we have lost amphibian species, we immediately see a negative impact on the natural environment, with a decline in other species reliant on frogs and tadpoles for food and algae growth clogging up the waterways.

Frogs need suitable land and freshwater habitats in order to survive. They have highly permeable skin that can easily absorb bacteria, chemicals and other toxins. These traits make them susceptible to changes in the natural environment and great indicators of the environment's health, and because they live on both land and in the water, they are a good indicator of the health of these two different environments within the same region. 

The frog’s natural behaviour makes them a key species and one of the most important members of the natural community to ensure the continued health of the forests and waterways in which they live.  The disappearance of frogs disturbs an intricate food web with cascading effects felt throughout an entire ecosystem.

Frogs have existed for nearly 300 million years, unless we act quickly, frogs and other amphibian species will continue to disappear, resulting in irreversible consequences to the planet’s ecosystems and to humans.

Frog conservation

Frog populations have been declining worldwide at unprecedented rates, and nearly one-third of the world’s amphibian species are threatened with extinction.

Amphibian populations are faced with an array of environmental problems, including pollution, infectious diseases, habitat loss, invasive species, climate change, and over-harvesting for the pet and food trades. 

The deadly fungal disease chytridiomycosis has caused dramatic population declines in more than 500 amphibian species, including 90 extinctions, over the past 50 years. The disease, which eats away at the skin of amphibians, has completely wiped out some species, while causing more sporadic deaths among other species. The deadly disease is present in more than 60 countries—the worst affected parts of the world are Australia, Central America and South America. 

The unprecedented number of declines places chytrid fungus among the most damaging of invasive species worldwide. Research suggests that globalisation and wildlife trade are the main causes of this global pandemic and are enabling the spread of disease to continue.

More than 40 frog species in Australia have declined due to the fungal disease during the past 30 years, including seven species that have become extinct. Scientists predict climate change, habitat destruction and disease could drive more than half of all Europe's frogs, toads and newts to extinction within 40 years.

This rapid disappearance of amphibian populations in recent decades is undoubtedly the most tragic loss of biodiversity we have ever witnessed and is one of the most serious environmental issues of our time.

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