3 Cold Blooded Amphibians of Fiji

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What is an Amphibian? – Amphibians are cold-blooded (unable to internally control their body temperatures, meaning their bodies remain at the same temperature as their immediate surroundings) vertebrates (backbone or spinal column). In this article, our team starts the amazing journey of discovering these often ignored classes of animals. With the two endemic frogs, the Fijian ground frog (Platymantis Vitianus) and the smaller tree frog (Platymantis vitiensis), and the dominant cane toad, one you will definitely observe hopping across the road or pathway whilst traversing across the islands, a formidable character introduced into Fiji in the 1930s by the Fijian Agriculture Department as a biological control agent.

Table of Contents

What is an Amphibian? 

‘Amphibians (Class Amphibia), have the ability to exploit both aquatic and terrestrial environments. The name amphibian, derived from the Greek amphibious meaning “living a double life,” reflects this dual life strategy.’ (Britannica, 2022)

‘Amphibians are a class of animals, representing the third highest biological classification. As a group, they are referred to as Amphibia. All modern amphibians can be grouped into the subclass Lissamphibia. Beyond this subclass, there are three orders of amphibians that represent all of the species. Anura, Caudata, Gymnophiona. Frogs and Toads belong to the Anoura class the name originating from the Greek meaning ‘without’ and ‘tail” (Earth, 2015)

YouTube Video:  Frogs at the Garden of the Sleeping Giant


Amphibians in Fiji (Endemic and Introduced)

There are only two endemic amphibians in Fiji, the endangered Fijian ground frog (Platymantis vitianus) and the smaller tree frog (P.vitiensis), with the introduced Cane Toad, brought to Fiji, for pest control in the early twentieth century.

Image Description
Fijian Ground FrogFijian Ground Frog – Platymantis vitianus (Endemic) These frogs once lived throughout Fiji but now only survive on four mongoose-free islands: Taveuni, Gau, Ovalau and Viwa (Tailevu).  A giant ground frog once lived in Fiji but is now extinct.  Description Shades of brown, with a white spot behind the eardrum some having an X marking on the shoulders or a white vertebral stripe running the length of the body. Habitats usually found in and around damp areas of the coastal and lowland forest floor near water. Behaviour – Nocturnal and secretive – sit for a long time in one position until suitable prey comes along. They consume live insects Good swimmers.
Size (snout-vent length (SVL))Females 85-270mm (SVL) – Males 50-110mm (SVL) – Hatchlings from 9-11 mm. (SVL)
Fiji Tree Frog Developing eggs laid in leaf of Pandanus tree Pandanus tectorius FijiFijian Tree Frog – Platymantis Vitiensis – (Endemic) – Currently found in Viti Levu and Vanua Levu.

Description – Light creamy grey to brilliant yellow, tans and oranges Habitat/Behaviour – Nocturnal animals and search for mates and forage for food (insects) at night. They mostly found in closed canopy rainforestm river systems. These frogs are good swimmers and climbers
Size (snout-vent length (SVL))Females 47-60 mm – Males 32-45 mm – Hatchlings from 9-11 mm.

Seven visual differences between a Frog and Toad


Visual differences between the Fijian Amphibians the Frog and Toad Diagram
Visual differences between a Frog and Toad Diagram | Image: Supplied
  1. Legs – There difference in leg length –  Frogs have much longer hind legs and have the ability to leap over 1 meter in distance, whereas the cane toads with their shorter stubby legs can only hop several centimeters.
  2. Body shape – Frogs project the appearance of athletic-looking animals. Toads are more aptly described as dumpy-looking.
  3. Skin Appearances –  The skin of a frog is relatively smooth and moist skin. The skin of a toad is bumpy with thicker skin than frogs
  4. Skin Moisture – Frogs have moist skin with a slimy feel. The skin of toads is usually the complete opposite with much drier skin.
  5. Habitat Differences – Frogs live on the water. They don’t stay in water 100 percent of the time. When they leave the water to go on land, they don’t venture far away from the water. Toads live on land. They will go into the water, but that’s not where they live. Because toads spend most of their time on land, they tend to stay close to the water.
  6. Colour Variations – Frogs tend to be much brighter and more vibrant in colour than toads. Most common frogs are (bright green or yellowy-green, though brownish-green hue). Toads are dark green or a dull shade of olive green
  7. Nose Shapes –  A frog’s nose is somewhat much more pointy in shape, with the toad’s nose being much broader in shape than that of a frog.

Two-phase, Six-stage lifecycle of the frog and toad


Diagram of a Lifecycle of the frog and toad (Amphibians of Fiji)
Diagram of a Lifecycle of the frog and toad | Image: Supplied

During the courting and mating rituals,  Frogs and toads produce a rich variety of sounds, calls, and songs, the callers, usually males, make stereotyped sounds in order to advertise their location, and their mating readiness.  Females steadily move toward and locate the calling males, where they gather in large numbers around a water source such as a pond, marsh and or drainage ditches.

Fun Fact 1:  The Fiji frogs are one of the few species in the world where both females and males call. The call sounds much like a dripping tap, and is quite difficult to hear near a loud, fast-flowing stream. Fun Fact (Nature Fiji, 2008)

Once the male has chosen his mate,  the male clasps the female from behind in the sexual embrace called ‘amplexus’, in which the male typically takes a position on the back of the female and tightly grasps onto the female with his front legs, they can remain attached in this position for several days.   Observations that this can be a highly aggressive act.

Eggs /Spawn – The attached pair swim about as the female swollen with eggs selects a site for depositing them as several thousand eggs are expelled from the female’s body in jelly-like streams the male fertilizes them with sperm.  The Jelly surrounding the eggs swells in the water until each egg is covered with a thick coating this acts as a float to keep the eggs near the surface of the water where it is warmer and there is more oxygen

Fun Fact 2:  Fijian Tree Frog – Undergo direct development. That is, tiny froglets or miniature frogs, rather than tadpoles, emerge from hatched eggs. The Fiji tree frogs lay their eggs in leaf axils, particularly of Pandanus trees from November to AprilFun Fact (Nature Fiji, 2008)

The eggs take 1-3 days to develop before a tadpole will hatch from each fertilized egg and another 22 days to mature before they leave the water.  First, the developing tadpole grows longer then the body and tail take shape and the tadpole shows signs of life with small wriggling movements at this stage the tadpole does not have any legs and breathes through gills.   In the next stage of development, the tadpole loses the gills and develops lungs, with the final stage within the aquatic environment, limbs appear first two hind legs and then two front legs and the tail is absorbed the tadpole has metamorphosed into a frog/toad and is able to begin a new way of life on land.  It will take almost two years to reach adulthood and be ready to mate with the opposite sex, to start this whole cycle again.

Fijian Cane Toad


Fijian Cane Toad
Fijian Cane Toad | Image: Supplied

In the 1936s Fijian farmers had a really big problem there’s sugar cane crops were being decimated by a voracious grub the larvae of the cane beetle which destroys the plant’s roots; after failed attempts at chemically controlling the grubs officials sought a biological solution they thought if they introduced a predator of the beetle, the problem would be solved.

The Fijian ecosystem was never the same again, the toads quickly became one of the dominant predators rapidly spreading over the two main islands today cane toads properly known as bufo marinus are one of the most notorious of all invasive species in Fiji this lumpy guy is seemingly unstoppable, with a large appetite they consume insects trash, dog food, small reptiles, and rodents and even small birds the one thing it doesn’t eat so is the cane beetle perched too high off the ground for cane toads to reach and the toads certainly can’t get to the grubs underground.

The introduction of this Fijian non-native habitat has been linked to the decline of several native species.  The cane toads’ particular biology makes it so most of the natural inhabitants of the Fijian ecosystem don’t stand a chance largely because cane toads are extremely poisonous adult cane toads have venom-secreting poison glands on each shoulder where a highly toxic milky substance is released when they are threatened if an animal tries to bite at the toad.

Unfortunately, it’s not just the adult cane toads that are the problem even the eggs and the tadpoles are poisonous which if ingested by vertebrate predators like fish and turtles can be fatal and this is no small threat cane toads don’t just lay a few eggs they lay a devastating amount of eggs and their toxicity added to their sheer numbers is creating a completely unexpected evolutionary event the life of a cane toad begins within an egg one cane toad female can lay up to 40,000 eggs at a time that’s a lot of eggs but usually when an animal has so many offspring they don’t expect many of them to survive but the problem with the cane toads in Fiji is the majority of them do survive these tiny black dots speckled down the string of eggs soon will hatch into tadpoles through metamorphosis process to emerge onto the land as young toads, staring the life whole cycle again.

Although the toad is not a real threat to humans, if you have handled one, always wash your hands thoroughly afterward and before consuming any food.

References

  • Barrios, A. (2022, December 5). How to Tell the Difference Between a Frog and a Toad. Wikihow. Retrieved March 13, 2023, from Link
  • Malone, M. (2021, February 21). Life Stages of a Toad. Cuteness. Retrieved March 13, 2023, from Link
  • Thomas, N. (2008, April 11). Fijian ground frog (Platymantis vitianus). Nature Fiji. Retrieved February 12, 2023, from Link
  • Sartore, J. (2020, October 12). Cane Toad. National Geographic. Retrieved March 13, 223, from Link
  • Unknown (2008, April 6). Fiji tree frog (Platymantis vitiensis). Nature Fiji. Retrieved February 12, 2023, from Link
  • Unknown (2021, September 22). Life Cycle of a Toad. Retrieved March 12, 2023, from Link
  • Unknown (2020, October 20). All about frogs and toads. Welcome Wildlife. Retrieved March 13, 2023, from Link
  • Weschsler, D. (2022, September 8). Toad Life Cycle. Doug Weschsler. Retrieved March 13, 2023, from Link
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Thakombau, Chief of the Fiji Islands, 1817-1883
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