Common tree frog perched on a branch of a tree at the Poomaale Estate, Coorg.
Among the countless creatures that exist in the world, our introduction to frogs happened fairly early in life. Fairytales, folk stories, rhymes, cinema..don’t we all just love this amusing, quirky being? We often get delighted when we see a frog hop, hear it croak or simply watch it sit on a broad leaf basking in the sun. But if you observe, every action of the frog is an indicator.
Important Indicator Species
Frogs are the most popular amphibians on earth. They do not have tails or noses, but their striking, protruding eyes are enough to grab anyone’s attention. The males are typically smaller in size than the females. While they can live almost anywhere in the world, they particularly enjoy tropical rainforests and wetlands due to the abundance of water.
Some creatures are known for their predatory behaviour (such as spiders) and some are known to fall prey very often (such as ants). Frogs show both behaviours. They feed on smaller insects, worms and rodents, and also fall prey to bigger reptiles, birds and animals, thus becoming an important link in the food chain. However, the presence of frogs can help us understand things beyond the food chain. They indicate things. Their presence tells us about the health of our environment and water bodies. So when you see a frog next time, there’s one more thing to be delighted about!
Being amphibians, frogs have the best of both worlds. This also means that the threats to their survival are twice as much. And to ward off threats and lead a peaceful life, they seek help from certain plants which ultimately make up the frog’s ecosystem.
Green and Leafy Elements of a Frog’s Ecosystem
All creatures live along with other creatures in an environment. They constantly interact with each other for various reasons. For example, butterflies and flowering plants have a give-and-take of services – flowers help butterflies lay eggs and butterflies help flowers pollinate. They benefit mutually. But these relationships always need not be mutualistic. And frogs’ relationship with plants is a great example of it.
The relationships between frogs and plants are often one-sided. This kind of relationship is called Commensalism. Being ectothermic in nature, they cannot produce their own body heat. So they need to often move from shaded and sun-exposed areas to regulate body temperature. Vegetation with a good proportion of shade and sun is perfect for frogs to live in. In addition, being amphibians, they live always live on the edge – the edge of land and water, and the edge of life and death. Here, healthy vegetation on shorelines can help them protect (hide) themselves from both aquatic and land predators.
Survival and shelter are only half the reasons for frogs choosing certain plants. The other half is defined by the process of procreation.
The Embrace of Life – Amplexus
A frog has never been one to follow conventions. It breathes with its moist skin, lives in water and on land, and even under the land while hibernating in winter. However, the way it mates is one of the most unique things about the species. Male and female frogs have evolved specifically for their unique mating style. It is the male’s duty to approach the female. So it sings during the mating season to mark an impression. The female, whose duty is to select a mate from the singing frogs in the vicinity, does not croak. Once she has found a match, she carries the male on her back as she is much larger in size to find a suitable spot (generally a crevasse between rocks or fast-flowing streams) and they embrace. During this, the female lays eggs (in clutches of hundreds to thousands) and the male releases sperm. Once they have done their job, they retreat to their habitats, but it is the aquatic plants that bear the responsibility from here on.
The released eggs flow into the water and attach themselves to the leaves of aquatic plants in clusters or strings, and then fertilisation takes place. Tadpoles that hatch can easily fall prey to larger aquatic creatures. They again rely on foliage or water plants to protect themselves and consume algae for growth.
Frogs don’t just rely on just aquatic plants for reproduction. They also find homes in plants that can hold water in one or more parts. One such plant is the bromeliad – a plant family that frogs across various regions of the world collectively love.
Commensalism or Mutualism?
Bromeliads make us several species spread across tropical and sub-tropical regions, and just like frogs, they are highly adaptable too. Frogs particularly love them for the home they make in their core, also called the ‘tank’ of the bromeliad. These tanks collect water from the rains and attract other smaller creatures too – making a micro-ecosystem in themselves. Frogs typically take shelter in these tanks which also become a place for them to mate and rear the tadpoles.
Naturally, when selecting a home, any being is bound to get picky. But the parameters frogs use to choose the tanks are complex and haven’t been able to pin-down by scientists. Frogs rely on instincts, preference and convenience to honour a bromeliad with its presence. They select a tank which is neither too small nor too big, with just enough water for their needs. Leaf litter or excessive debris also repels frogs and they thrive in clean water. The selection criteria also differ from place to place, ecosystem to ecosystem.
It is widely accepted that in this close relationship between bromeliads and frogs, frogs benefit and bromeliads are unaffected. But in a study by Senior Mackenzie Goltz, it is deduced that the relationship is mutually beneficial. Frogs help bromeliads grow faster by providing them with nitrogen. Another instance of mutualism between frogs and plants can be seen with algae. With the frog’s skin being moist all the time, algae find a natural ground there. In return, they help frogs camouflage, keeping them safe when predators lurk around.
Scientists worldwide are still doing extensive research on plant-frog relationships. Such nuances tell us about the complexity that exists between interdependent species and the beautiful, unfathomable web of life we live in!
How Can You Invite Frogs to Your Ecosystem?
If you love nature and enjoy the company of all its inhabitants, attracting frogs to your gardens, open spaces and farms can benefit your ecosystem. Firstly, if a frog comes into your world, it is a sign of a healthy environment. Secondly, they are natural pest controllers and keep the insect population in check, especially flies and mosquitoes.
To make your green spaces frog-friendly, make sure you have a water body as the entire lifecycle of a frog goes in and around water. Being amphibians, they like to have the choice of going in and out of water with ease. Hence frogs prefer water bodies that are shallow around and edges and deeper at the centre. Introduce enough aquatic plants into your water body which act as a source of water and breeding grounds for frogs. Use plants that provide enough shade and sunlight along with some logs and rocks for additional shelter. Keeping your environment clean and free of litter is also important as frogs like to live in clean areas and are sensitive to chemicals/ harsh fertilizers.
Frogs are one of nature’s highly adaptable creatures. They can live in human-dominant habitats as well as lush forests full of predators. They evolve with changing climates and have diverse survival methods – from camouflaging, aposematic colouration (colours that caution predators), burrowing and more. Some frogs that have evolved in specific ecosystems turn endemic to the regions and amplify their biodiversity multifold. Excellent examples of such regions are the Western Ghats in India, which are a Biodiversity Hotspot. About 90% of over 250 amphibians found in the Western Ghats are endemic to the region including several species of strikingly beautiful frogs.
Despite their resilient nature, frog populations over the last few decades have been in decline and one of the main reasons for that is human activities and modern developments. The declining number of frogs is not just an indicator of the threats to that particular species, but also threats to all those species that are connected to its ecosystem. The survival of one is dependent on the survival of all and vice versa.
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