Gumby Legacy is thrilled to present as our first guest poster, Dr Jeanne Tarrant, an expert in frogs and manager of the Endangered Wildlife Trust’s Threatened Amphibian Program. She has kindly agreed to do a frog for each letter as we go through our 365 Nature Days.
Amphibians (from the Greek amphi = double, and bios = life), are well-known to most of us, often being one our first connections to nature as we eagerly scoop up tadpoles to watch them develop out into froglets in a tub at home. They are the largest animals to undergo such transformation – metamorphosis – an amazing fast-forward representation of evolution of the invasion of land from water, and one that sparks all of our imaginations.
Amphibians are an extremely diverse Class of vertebrates, comprised of the tailless Anura (frogs and toads), of which there are currently over 6000 known species; the tailed Caudata (salamanders): 600+ species and; the worm-like, underground dwellers Gymnophiona (caecilians): 200 species. Indeed, amphibian species diversity now exceeds that of mammals (about 4000 species).
Amphibians have been around since before the dinosaurs, survived after the dinosaurs disappeared, and have certainly been on Earth a lot longer than our own species (at a paltry 200 thousand years). During this long existence, frogs have been masters of adaptation and filled just about every ecological niche available. Other than the frozen ends of the Earth, frogs can be found on all continents and habitat types including grasslands, wetlands, rivers, mountains and even deserts. They do tend to like warm and moist places so there is particularly high species richness in the tropics.
Similarly, humans (along with frogs, one of the only vertebrates not to have tails) are equally good at invading all territories across the planet, and with an ever burgeoning population, are wiping out frog habitat at an unprecedented rate. The result is that there are more threatened amphibians on Earth than any other vertebrate group: almost half of all known species are experiencing population declines.
Amphibians are also well recognised as important bio-indicators. This is because amphibians have a number of physiological, ecological and life-history characteristics that make them prone to changes in the environment. Most species make use of both the aquatic and terrestrial environments during their life cycles, and as a result, are sensitive to changes in both systems. Both habitats are also impacted by intense human use. Amphibian declines would thus have negative impacts in both aquatic and terrestrial ecosystems.
Due to their biphasic lifestyle and their sensitive semi-permeable skins, amphibians are considered good indicators of environmental health and the state of the biosphere as a whole. Owing to their low vagility (i.e. they are not able to move away from disturbance as quickly or effectively as say birds), they are particularly sensitive to habitat fragmentation and are vulnerable to the changes brought about through habitat transformation.
Frogs are the most threatened vertebrates on Earth (with 32% listed on the International Union for the Conservation of Nature Red List compared with 12% of birds and 23% of mammals). This is a huge proportion of an entire Class of animal facing extinction, with dire consequences. The Red List includes the threat categories of Vulnerable, Endangered and Critically Endangered depending on the severity of threats facing a particular species and or its rarity. Critically Endangered species are those most at threat of extinction unless proactive intervention is taken to curb threats.
Frogs are important indicators of the health of our environment and the fact that a third of all species face extinction should be a clear warning that our global health is in jeopardy. The expected magnitude in the loss of amphibians is significant and will undoubtedly have a multiplier effect, ultimately contributing to declines and extinctions of other species which rely on them.
Arum Lily Frog
Arum Lily Frogs are known only from the Western Cape in South Africa. As the name suggests, they enjoy sheltering in the beautiful Arum Lilies which are common around pans, dams, vleis and small streams. They are creamy in colour, with a pale band and dark stripe running down their side. Males have a dark yellow throat.
As with all frogs, only the males call, usually at night – a harsh quee-quee bleat. Each species of frog has its own unique call – used to attract breeding females to suitable sites for mating and depositing eggs.
The Arum Lily Frog lays clutches of 10 – 30 creamy eggs attached the plants under water. Tadpoles take a few weeks to develop.
A number of other frogs species utilise Arum Lilies, including Tree Frogs, different species of Reed Frogs, and Leaf-folding frogs. This has led to some confusion in South Africa about exactly who the real Arum Lily Frog is, but this is easily solved depending on where in the country you are – Arum Lily frogs are the Western Cape’s only true reed frog species, with the rest being found on the East side of the country.
How do you get on with frogs? Were you were aware that they are so important in letting us know what a mess the planet is in?