You get your birders, your wildlife enthusiasts, people that collect bugs and butterflies, and then you get your froggers or people that study and track frogs. Carel Loubser explores the world of frogging and why these little amphibians are such interesting creatures…
What is frogging?
Not only is it a science, but also a recreational activity. Some people may do it as research for their Ph. while for others it means exciting discoveries on a summer holiday or just a reason to leave the city behind.
It is not all about the frogs, but is also about exploring wetlands, listening to the sounds of the African bush, observing and conserving the natural world. It is much more than trekking through a drenched marsh after a frog’s call, hoping to catch a glimpse of it.
Frogs’ place in the animal kingdom
In general animals are classified into a hierarchy of categories based on their skeletal or other features that indicate a common evolutionary ancestor.
- Frogs belong to the phylum Chordata or vertebrates – these are animals with a backbone.
- Vertebrates can be divided into five classes: fish, amphibians, reptiles, birds and mammals. Frogs are amphibians, animals with two phases in their lives – a tadpole and a four-legged adult.
- Amphibians are divided in three orders. There are the tail-less amphibians belonging to the Anura order, the Caudata order of salamanders and newts and then the Apoda order of worm-like caecilians.
- There are 18 families of frogs in the world with nine of these in southern Africa.
- In southern Africa there are 33 genera out of a total 270.
- 2 500 species exist worldwide with roughly 130 in southern Africa.
How to find a frog?
Most frogs are nocturnal and you will require a good flashlight, a very good ear and lots of patience. The best way to find them is by tracking their calls after dark. Frogs are well concealed and calls sometimes seem to be ventriloquial.
Best way is to track a frog is with a partner, walking well apart from each other. Once you hear a call you point your torch in the direction of the sound. The frog will most likely be where your beams intersect. Move slowly towards the location. If the sounds stop, stand still and switch off the torch and wait for the call to start again.
Why the chorus of frogs?
Frogs utter a number of calls, for mating purposes, to stake their territory, when they are distressed and when they make a release call. The most common call is males trying to attract females to their breeding site. Each call is unique to each species.
A male frog needs to carefully choose his position from where he will make a territorial call. If unsuccessful, an intruder may be attacked by being wrestled, kicked or pushed with an expanded vocal sac.
A release call is made when a female wants to terminate mating or when, during a sexual frenzy at a breeding site, males accidently clasp each other. With a sharp rebuff in the form of the release call the males will quickly get the message and leave each other alone.
Once the female has been successfully attracted to the breeding site, mating will take place. The smaller male will clasp his mate in amplexus and deposit sperm onto the eggs that the female lays.
From tadpole to frog…
After several days the eggs hatch into a tadpole which is usually aquatic and obtains oxygen through gills. These little tadpoles feed on algae and other organic matter in the water. Species that hatch outside the water will feed off the egg yolk and are supported in a fluid jelly.
Metamorphosis is driven by the release of hormones form the thyroid and pituitary glands in the tadpole. Within a few days of the metamorphosis being triggered, the tail, fins and gills will disappear. The frogs’ internal organs change to allow for its carnivorous habits. The full vertebrate skeleton and muscle system develops together with the tongue, eyelids and a totally different type of skin.
Breathing through its skin…
Glands in the skin secrete fluids which help to keep the skin moist as well as with oxygen absorption. Being able to absorb oxygen through their skins allow frogs to stay under water longer.
The skin of frogs needs to stay moist. If they are unprotected from dry conditions they will desiccate. Most frogs will retreat to a moist area during the heat of the day. Other species can change their skin pigmentation so that it becomes lighter to reflect the heat.
Distribution of frogs
Frogs prefer warm and damp regions due to their porous skin with the greatest number of species found in the eastern regions of southern Africa where high rainfall combines with warm year-round temperatures.
Some species are widely dispersed while others like the Table Mountain ghost frog and Amatola toad have extremely limited ranges.
What do frogs eat?
A tongue fixed to the front of the mouth will flip forward to catch its prey live, swallowing it whole. The diet mainly consists of insects and other invertebrates.
Seeing and hearing
Except for burrowing species, frogs have large eyes, well-developed for their nocturnal behaviour. Hearing is of considerable importance and a large tympanum or eardrum helps with its hearing.
Written by Carel Loubser, Wilderness Safaris Blog Contributor
Photographs by Dana Allen