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31 October 2021 | Story Elsabé Brits
Grassland

In the vast, flat grasslands of South Africa a host of magnificent plant and animal species flourish, but not all of them are large. Insects and spiders share the landscape, and they are sometimes the uncelebrated heroes of a fragile ecology.

Walking through grasslands one often ignores what is under our feet, but these creatures are vitally important for the wellbeing of any ecosystem.

Grasslands are the dominant vegetation in the central parts of the country, covering most of the Free State and Gauteng and large parts of the North West, Mpumalanga, KwaZulu-Natal and the Eastern Cape, explains Prof Charles Haddad from the Department of Zoology and Entomology in the Faculty of Natural and Agricultural Sciences at the University of the Free State (UFS).

Insects fulfil a myriad of ecosystem functions and deliver crucial services in grasslands. They are the most important group of pollinators, such as bees, flies, and beetles, and are critical to the breakdown of plant and animal waste, especially flies and beetles. They are predators and parasites of other invertebrates, especially spiders, beetles, wasps and flies. The more species in an ecosystem, the greater the number of interacting organisms that can contribute to food webs.

Unfortunately, grasslands are the most threatened biome in South Africa, largely as a consequence of historical agricultural expansion of crop and livestock farming. More recently, urban development, invasive plants and silviculture have impacted on the remaining natural grasslands.

“Little is known about the impact of these activities on terrestrial biodiversity. The presumption is that the destruction and fragmentation of natural grassland reduces the natural vegetation available to indigenous organisms. This creates problems for insects to find suitable plants to feed on, which has a negative impact on their predators and parasites.

“Most anthropogenic influences affect indigenous biodiversity negatively, with very few exceptions. Generally, it is exotic invasive species that benefit the most from disturbance, habitat changes or destruction,” says Prof Haddad.

Spiders

More than 900 species of spiders have been recorded in our grasslands and some 2 300 in the country. Spiders are predators of other invertebrates, especially insects, and play an important role in the natural control of their populations.

They are very resilient to disturbance but are susceptible to chemicals used on crops, the effects of alien plants, and competition with exotic spider species, says Prof Haddad.

Among the interesting spider species one can find in grasslands is a rich diversity of trapdoor spiders, which live in burrows in the ground. Many of them have narrow associations with specific soil types and are often good bioindicators for conservation management.

Some plant-dwelling spiders are uniquely adapted to living on grasses and have slender, pale bodies to camouflage themselves on the stalks of grasses. In contrast, tree-dwelling spiders are often brown with tubercles on their bodies to blend in with the bark of trees to help them ambush their prey, says Prof Haddad.

Termites

Termites are some of the most populous animals on Earth, and the effects they have are most profound in the grasslands. Termites are one of the few animals that can break down cellulose from dead wood and grass. This is made possible through their symbiotic association with tiny microorganisms in their alimentary canal, such as protozoans and bacteria. The microorganisms secrete the enzyme cellulase, which the termites cannot produce themselves, allowing for the breakdown of cellulose in the ingested plant material and the release of the component nutrients for use by the termites. Therefore, these insects play an integral role in the reintroduction of nutrients from the dead plants into the soil.

This enables them to utilise the molecules in the grass that would have otherwise been inaccessible. Their faeces, therefore, contain broken-down nutrients that the roots of plants can absorb.

Many termite species live in underground nests that are great in aerating the soil. Others build large mounds which are extensions of the nests above the soil surface. These mounds, particularly those of the snouted harvester termites, are a familiar feature in most grassland landscapes in the country. These nests and mounds also offer shelter to other organisms, such as spiders, scorpions, lizards, snakes, millipedes, and various insects.

Termites are an important food source for enigmatic animals such as the aardvark and aardwolf, as well as some spiders and beetles, says Prof Haddad. 

Mosquitoes 

Liezl Whitehead, a master’s student in the Department of Zoology and Entomology at the UFS, explains the role of how even mosquitoes are essential.

Mosquitoes are vitally integrated into the ecosystem even as larvae, where they feed on aquatic microorganisms, thereby affecting species interactions and ecosystem dynamics within the aquatic habitat.

Adult mosquitoes feed on nectar as their main food source, and in the process also serve as plant pollinators. Many female mosquitoes do, however, require a blood meal for egg production, where they then transmit a multitude of pathogens. Interestingly, these pathogens play a vital role in the ecosystem, where they help to regulate host population sizes, thereby maintaining the integrity of the ecosystem.

“In recognising the significance of all forms of life, one also realises that mosquitoes play an essential role in the life cycle of numerous other organisms, including protozoans [single-celled microscopic organisms], nematodes [often referred to as roundworms, but they are not closely related to true worms], and mites that depend on mosquitoes for their development and dispersal.

The abundance and widespread nature of mosquitoes contributes to their significant role in the grassland food chain, where the larvae are consumed by countless aquatic organisms, including insects, fish and amphibians. The adults are consumed by a multitude of arthropods and vertebrates, including dragonflies, birds and bats.

“Their elimination from the ecosystem would thereby impact multiple processes within the ecosystem, affecting food webs, pollination and the presence of many other associated organisms,” Whitehead adds. 

A vital food source, urgent protection needed

Prof Liesl van As, Head of the Department of Zoology and Entomology at the UFS says that although the Grassland biome covers an area of 339 237 km2, less than 2% is formally protected. In 2004, the National Spatial Biodiversity Assessment (NSBA) identified the Grassland biome as the most threatened habitat, with more than 30% already irreversibly transformed. A year later, the Grassland Biodiversity Spatial Priority Assessment identified 37% of the land as being important for conservation and suggested that 12% needs to be under formal protection by 2028.

Most of the South African grassland literature refers to the almost 400 plant species, the 34 endemic mammals, and the dozen or so globally threatened bird species, with almost no mention to representatives of the Arthropoda (including spiders, termites and mosquitoes).

Invertebrates are the main components of faunal diversity in grasslands, playing substantial roles in ecosystem processes, including nutrient cycling, pollination, and being a vital food source in food webs (Die een se dood is die ander een se brood).

“These invertebrate communities are heavily dependent on plant diversity and production within a given ecosystem, but for some reason, they don’t get the full recognition and attention compared to the larger animals. Maybe it is because they are not so visible due to their smaller size?

“A visit to www.grasslands.org.za and the Grassland Society of Southern Africa draws our attention towards the fact that although progress has been made in the awareness of the sensitivity of grassland habitats, gaps still exist concerning the biodiversity of the remaining natural fauna. To follow up on this, I am of the opinion that when it comes to invertebrates, such as the spiders, termites and mosquitoes we are now writing about, knowledge and public awareness (citizen science) is contributing to reducing this gap” says Prof Van As.

According to her, in their department, a number of colleagues from Animal Behaviour, Arachnology, Nematology, Applied Agricultural Entomology, Environmental Entomology and Dipterology, to name a few, have been involved in research projects for the past few decades, with a focus on the grassland area, closer to home.  Through their effort and contributions, they are making a scientific difference. 

News Archive

Dr Francois Deacon appears in international film, Last of the Longnecks, due to research on giraffes
2017-04-04

Description: Giraffe research read more  Tags: Giraffe research read more

Dr Francois Deacon was invited by the producer of Last
of the Longnecks
to be part of a panel handling a question-
and-answer-session about the film.
Photo: Supplied

A great honour was bestowed on a researcher at the University of the Free State (UFS) when he was invited to the preview of the documentary film, Last of the Longnecks. Dr Francois Deacon, lecturer and researcher in the Department of Animal, Wildlife and Grassland Sciences at the UFS, who also has a role in the film, attended the preview at the Carnegie Institution for Science’s Smithsonian National Museum in Washington DC, in the US, in March this year. The preview formed part of the DC Environmental Film Festival.

The Environmental Film Festival in the US capital is the world’s leading showcase of films with an environmental theme and which aims to improve the public’s understanding of the environment through the power of film. During the festival, the largest such festival in the US, more than 150 films were shown to an audience of 30 000 plus. 

Dr Deacon was invited by the producer of Last of the Longnecks to be part of a panel handling a question-and-answer-session about the film directly after the show. He described it as the greatest moment of his life. 

Role in the film Last of the Longnecks

“My role in the film was as the researcher studying giraffes in their natural habitat in order to understand them better, so that we may better protect them, and be able to provide better education on the problem in Africa,” says Dr Deacon. 

“Together with Prof Nico Smit, also from the UFS Department of Animal, Wildlife and Grassland Sciences, Hennie Butler from the Department of Zoology, and Martin Haupt from Africa Wildlife Tracking, we were the first researchers in the world to equip giraffes with GPS collars and to conduct research on this initiative,” he says. This ground-breaking research has attracted international media attention to Dr Deacon and Prof Smit. 

“Satellite tracking is proving to be extremely valuable in the wildlife environment. The unit is based on a mobile global two-way communication platform, utilising two-way data satellite communication, complete with GPS systems.

“It allows us to track animals day and night, while we monitor their movements remotely from a computer over a period of a few years. These systems make the efficient control and monitoring of wildlife in all weather conditions and in near-to-real time possible. We can even communicate with the animals, calling up their positions or changing the tracking schedules,” says Dr Deacon.

The collars, which have been designed to follow giraffes, enable researchers to obtain and apply highly accurate data in order to conduct research. Data can be analysed to determine territory, distribution or habitat preference for any particular species.

Over a period of three years (2014-2016), the Last of the Longnecks team from Iniosante LLC captured on film how Dr Deacon and his team used the GPS collars in Africa to collect data and conduct research on the animals.

“With our research, which aims to understand why giraffes are becoming extinct in Africa, we are looking at the animal in its habitat but not only the animal on its own. If the habitat of these animals is lost, they will be lost as well. Therefore, our focus is on conservation and better understanding the habitat. The giraffe is only a tool to better understand the habitat problem,” says Dr Deacon. 

Since the beginning of his research Dr Deacon and his team have had six new collar designs, with animals in four different reserves being equipped with the collars. The collars use the best technology available in the world and make it possible to determine how giraffes communicate over long distances, and how their sleep patterns function. Physiological and biological focus is placed on the giraffe’s stress levels, natural hormone cycles, and milk quality in cows. 

Description: Giraffe 2017 Tags: Giraffe 2017

Photo: Supplied

Experience at the film festival

“Absolutely amazing. Totally beyond our frame of reference as South Africans.” This is how Dr Deacon describes his experience of the three days in Washington DC during the film festival.

“It was an absolute honour to be part of the global preview of the film and to be able to work with Ashley Davison, the director of the film, and his team. I am just a rural farm boy who dreams big, and now this dream is known worldwide!” he says. 

The film, which will be launched in April, will be screened in South Africa on the National Geographic channel in May 2017. Meanwhile, the film will also be shown at eight other film festivals in the US. 

Work will start on a follow-up documentary in October and Dr Deacon is excited about the prospect. A mobile X-ray machine will be available from October. Internal sonars could also be performed on each of the animals. Researchers from around the world will form part of the team which will be led and co-ordinated by Dr Deacon and his co-workers at the UFS.

Former articles: 

18 Nov 2016: http://www.ufs.ac.za/templates/news-archive-item?news=7964 
23 August 2016: http://www.ufs.ac.za/templates/news-archive-item?news=7856 
9 March 2016:Giraffe research broadcast on National Geographic channel
18 Sept 2015 Researchers reach out across continents in giraffe research
29 May 2015: Researchers international leaders in satellite tracking in the wildlife environment

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