letting nature back in

Guttural Toads and other frogs have been galvanised into springtime activity by sprinklings of early season rain. The males have been calling for mates culminating in pairs spawning in our pond.

Most noticeable are the Guttural Toads (Sclerophrys gutturalis) due to their loud nocturnal calls during their breeding times and because they are the largest and least shy amphibians in our garden. Like many toad species in southern Africa, Guttural Toads are explosive breeders: they breed in response to specific trigger factors. Breeding is triggered by rain in the early spring  and possibly also by rising temperatures for those near permanent bodies of water. Breeding events triggered by rain may take place through to mid-summer.

After a rowdy night, these Guttural Toads were busy spawning in the pond in the early morning. Their spawn can seen behind them in the form of two gelatinous strings of eggs that the pair of toads wind around the vegetation as they swim

In our garden, the loud calling from the Guttural Toads, which starts after sundown – and may continue for several hours – lasts only a few nights until the next trigger for the next breeding event. So for those who object to the sounds of calling toads, in our experience at least, the calling periods are sporadic. During the day Guttural Toads take shelter in shady and concealed spots, such as under leaves and logs, with some excavating small burrows in soft ground.  

Worldwide, amphibians are decreasing in number. Of the 117 species of frogs and toads found in South Africa, 51 species are endemic. In 2010, of these, 8 species were classed as being Critically Endangered, 16 species as Endangered, 16 as Vulnerable and 8 species Near Threatened. Habitat loss is one of the major threats facing amphibians.

The Guttural Toad is not one of the species endemic to southern Africa and it occurs naturally as far north as southern Somalia. In South Africa it has adapted well to artificial bodies of water such as dams and ponds, even in urban areas. Its range has extended into the south-west, probably because of inadvertent translocation by people, and it is considered a threat to the Leopard Toad that is endemic to that region. Consequently, in the South Western Cape they are subjected to eradication. 

A Guttural Toad out on the lawn hunting flying ants (termites) that emerged after rain

Although invasive in other regions, in our region Guttural Toads occur naturally, although we have noticed a decline in our specific neighbourhood. Years back, especially on misty nights Guttural Toads used to congregate under street lamps in our quiet street to catch insects attracted to the lights. In recent years we almost never see frogs in the street – either alive or dead as a result of being run over, which was a common occurrence before. Although Guttural Toads are adaptable, they also suffer from loss of habitat and are subject to persecution in suburban areas.

In KwaZulu-Natal there is no reason to persecute these animals. That they eat insects, such as mosquitoes, and eat snails and slugs can be viewed as beneficial, and they play a role in our local ecology. The calling of breeding toads and frogs indicates a healthy environment and many people like the sounds that put them in touch with the natural world.  Consider that tourists spend a lot of money to go on African safaris and are enchanted by the sounds of frogs and toads calling at night. Compared to loud music and house parties, traffic and leaf blowers, it seems strange that so many people are so intolerant of the calls of frogs and toads.

Last night when more light rain was imminent and the toads and frogs responded with their calling, we went out with a torch and camera to take a look. We interrupted a Guttural Toad who stopped calling due to our presence. He looked rather startled by the torchlight. To the left of the photo a much smaller Clicking Stream Frog can just be seen.  The clicking calls of these small frogs is audible most rainy nights in the breeding season

This Guttural Toad could hardly wait for us to leave so it could carry on calling

Females are attracted by the calling of the males. When preparing for the process of mating the male mounts the female and grasps her tightly with his forearms in an embrace known as amplexus (which in fact is Latin for ‘embrace’). In this posture he is positioned to fertilise the eggs as they are expelled from the female’s body into the water.

On an overcast morning, a male Guttural Toad was still calling while another male paired up with a female in our garden pond. (This and some other photos in this post and the video were taken in another summer when there was more foliage in the pond than there is currently.)

Breeding can be highly competitive and male toads can seek to dislodge and displace another male that is already coupled with a female. In some instances competition may be so fierce that a ball or tangle of toads can form as males actively try to displace each other and grasp the female. Needless to say this can be very dangerous for females and can result in drownings.

 A male Guttural Toad, seemingly glaring at me, is about to try to dislodge another male that is already coupled with a female

In the video below, in the first clip a coupled pair prepares to spawn while another toad provides the soundtrack. In the second clip the spawn can be seen flowing out into the water, the male fertilizing the eggs as they are emitted from the female’s body. In the third clip, a second male has climbed on top of a coupled pair and does his best to dislodge the rival male.

Video of mating Guttural Toads filmed in our garden pond

Usually when I have seen Guttural Toads spawning, even when it is busy and there are several couples in the pond, it mostly seems to be a rather benign affair. But little did I know.

Last week on an overcast morning after the busy night before, I visited the pond and found festoons of spawn in the water plus also this pair (below) floating in the pond. I thought there was something a bit odd about the pair. The male had beautiful golden eyes but I wondered if the female with only one cloudy eye visible was blind.

The next day, we found them still in the pond and it dawned on me that in fact the female was dead, although still clasped tightly by the male who was largely submerged. Fearing that the male might be drowning we moved the pair (using a sieve we use to scoop leaves from the surface of the pond) to the shallow end, ensuring that the male’s nose was out of the water. As this was a disturbing sight, I did not take any photographs, but instead went inside to see if I could find any information about frogs and toads mating with a dead partner.

To my surprise I did come across information on some species of frogs and toads – and other species besides – that have been found mating with a dead partner. In the case of some toad species, they have even been found in amplexus with inanimate objects and sometimes also with other species.

Most surprising of all, was that there are recorded incidents of lizards and frogs managing to extract eggs from a dead female’s body and fertilise them. For example, this has been seen in a species of South American frog, Rhinella proboscidea. Field researchers in Brazil observing a male frog clasping a dead female, “saw him squeezing rhythmically, coaxing a string of sticky eggs from her body”. The scientists, in order to confirm if such efforts had been successful collected eggs from “one-sided pairings” and stored them in water-filled plastic bags. As the eggs began to develop they were able to confirm that the males had indeed fertilised the eggs. It is noted that “it is very likely that other frogs engage in similar postmortem reproduction—but acknowledge[d] it will be hard to spot. (For more see https://www.the-scientist.com/notebook/croakus-interruptus-39244)

After reading this information I decided to take my camera to record the male frog I had left clasping a dead female on the sieve in the shallow end of the pond. But as I approached I saw the male had gone. To my amazement there was a trail of fresh spawn on the sieve, with a strand of eggs wound around a hind leg of the dead female. It appeared that in my absence when I was looking up the phenomenon, the male had extracted eggs from the dead female. Presumably he had fertilised the eggs in the process before he disappeared from the scene.

I regretted that my squeamishness had prevented me from taking photographs and keeping a better record. Such a mating may not be a rare practice amount Guttural Toads, but it seems records of such an event are rare. We tipped the spawn into the pond to give it a chance of survival and we will never know if it was fertile or not.

Currently there is not much foliage in the pond, so other pairings of toads used a rock around which to wind some of the spawn

One of the small plants in the pond is also festooned with ropes of spawn

Hopefully the eggs will hatch tadpoles that will eventually develop and transform into frogs. This astonishing metamorphosis underlies the folktales that tell of the extreme transformation of a frog turning into a prince, although I think that the natural phenomenon is miraculous enough as it is.

This photo of three tadpoles in our pond (together with a water snail and what might be a tiny damselfly nymph) was taken last summer. These tadpoles are starting to grow hind legs, most noticeable in the tadpole at the top

We value that the tadpoles eat the algae in our pond and also eat mosquito larvae. They also are a source of food for other creatures, such as the fishing spider, and tadpoles themselves are also known to eat each other. From the thousands of eggs laid by the Guttural Toads, only a small percentage survive to hatch as tadpoles, and an even smaller percentage of these survive to develop into froglets, and only a small percentage of these survive to become adults that themselves are potential prey for snakes and other predators. Such is the circle of life when one is a toad.

Sources: 

Measey, G John. 2011. Ensuring a Future for South Africa’s Frogs: A Strategy for Conservation Research. SANBI Biodiversity Series 9. Pretoria: National Biodiversity Institute. https://www.researchgate.net/publication/259285286_Ensuring_a_future_for_South_Africa’s_frogs_a_strategy_for_conservation_research;

Richards, Sabrina. 2012. Croakus Interruptus. The Scientist. https://www.the-scientist.com/notebook/croakus-interruptus-39244;

Vlok, W, Fouché, PSO, Cook, CL, Wepener, V & Wagenaar, GM. 2013. An assessment of the current distribution, biodiversity and health of frogs of the Kruger National Park in relation to physical and chemical factors. WRC Report no. 1928/1/12. Gezina: Water Research Commission. https://www.researchgate.net/publication/262913308_An_assessment_of_the_current_distribution_biodiversity_and_health_of_the_frogs_of_the_Kruger_National_Park_in_relation_to_physical_and_chemical_factors

 Posted by Carol