Daytime sightings of elusive aardvarks hint at troubled times in the Kalahari



Disappearance of aardvarks from dry ecosystems could have devastating consequences for the many other animals that rely on their burrows.
Kelsey Green

Robyn Hetem, University of the Witwatersrand and Nora Marie Weyer, University of the Witwatersrand

Aardvarks are notoriously elusive, nocturnal mammals. They generally hide in their underground burrows during the day and emerge at night to feed exclusively on ants and termites. Aardvarks are widespread throughout most habitats of Africa south of the Sahara, except deserts. But their actual numbers are not known because they’re so elusive.

Aardvarks top the bucket list of many wildlife enthusiasts, but few have been fortunate enough to see them – until recently. Daytime sightings of aardvarks are becoming more common in the drier parts of southern Africa. But seeing them in the daytime does not bode well because it indicates they might not be finding enough food.

To understand how aardvarks cope with hot and dry conditions, we studied them in the Kalahari, one of the hottest and driest savannah regions in southern Africa in which aardvarks occur. Our study took place at Tswalu, a private reserve in South Africa that supports research through the Tswalu Foundation. We equipped wild, free-living aardvarks with biologgers (minicomputers) that remotely and continuously recorded their body temperature (an indicator of well-being in large mammals), and their activity. Each aardvark also received a radio-tracking device, allowing us to locate them regularly. Tracking the aardvarks provided clues on how they changed their behaviour in relation to environmental stressors in the different seasons and years of our three-year study.

Our study found that in drought periods, aardvarks struggled to find food. It was difficult for them to maintain their energy balance and stay warm during the cool night, so they shifted their active time to the day. Some died from starvation. Given the aardvark’s importance to ecosystems, these findings are a concern.

Comparison of Aardvarks at night and day
Aardvarks usually emerge from their burrows at night (left), but during drought periods, they are increasingly seen during daytime (right).
N. Weyer

Aardvarks are important ecosystem engineers

No other mammal in Africa digs as many large burrows as the aardvark. Dozens of mammals, birds and reptiles use aardvark burrows as shelter from extreme heat and cold, protection from predators, or a place to raise their young. In many of South Africa’s conservation areas, temperatures have already risen by 2℃ over the past 50 years. Further warming by 4-6℃ by the end of the century has been projected.

With deserts and drylands expanding across much of Africa, climate change might threaten the aardvark itself as well as the many animals reliant on aardvark burrows as a cool shelter from rising temperatures.

During typical years, aardvarks were active at night and were able to regulate their body temperature between 35-37℃.

Aardvark active at night during non-drought times
Aardvark active at night during non-drought times.
adapted from Weyer et al., 2020, Frontiers in Physiology, https://doi.org/10.3389/fphys.2020.00637

However, this pattern changed during two severe summer droughts that occurred in the Kalahari during our study. During the droughts, aardvarks shifted their activity to the daytime and their body temperature plummeted below 30°C.

Using remotely-sensed vegetation data recorded by NASA satellites and our own camera trap footage and logger data, we showed that these dramatic changes in body temperature and activity of aardvarks were related to the availability of grass, on which their ant and termite prey rely. When grass was scarce during droughts, the ant and termite prey became inaccessible to aardvarks, preventing them from meeting their daily energy requirements. As their body reserves declined, aardvarks were unable to sustain the energy costs of maintaining warm and stable body temperatures and shifted their activity to the warmer daytime.

Aardvark active in the daytime during drought
Aardvark active in the daytime during drought.
adapted from Weyer et al., 2020, Frontiers in Physiology, https://doi.org/10.3389/fphys.2020.00637

Shifting activity to the warmer daytime while food is scarce can save energy that would otherwise be spent on staying warm during cold nights. But, for our aardvarks, even these energy savings were insufficient during drought, when the ground was bare and the ant and termite prey inaccessible. As a result, seven of our twelve study aardvarks and many others died, presumably from starvation.

A bleak future for aardvarks in a hotter and drier world

On the Red List of Species of the International Union for Conservation of Nature, aardvarks are currently categorised as a species of “Least Concern”. However, we consider aardvarks to be threatened in the drier parts of their distribution in Africa, such as the Kalahari, where climate change brings about droughts. Disappearance of aardvarks from these ecosystems could have devastating consequences for the many other animals that rely on the aardvarks’ burrows.

We hope that our findings will raise further awareness about the consequences of climate change and inform future wildlife conservation and management decisions. Such steps might include assessments of the actual population status of aardvarks across Africa, or mitigation measures to preserve species that depend on burrows for refuge in regions where aardvarks might go locally extinct. More extensive measures, like water-wise reserve management, increasing sizes and connectivity of nature reserves in semi-arid regions, and reducing emissions to mitigate climate change, are just as urgent.

Finally, any solution to the plight of climate change on free-living animals requires a better understanding of their capacities to cope with drought. Therefore, many more long-term comprehensive studies are needed on the physiology and behaviour of the vulnerable animals living in hot, arid regions of the world.

Nora Marie Weyer’s disclosure statement has been updated.The Conversation

Robyn Hetem, Senior Lecturer, University of the Witwatersrand and Nora Marie Weyer, PhD – Wildlife Conservation Physiology, University of the Witwatersrand

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The diet of invasive toads in Mauritius has some rare species on the menu



The invasive guttural toad.
Author supplied.

James Baxter-Gilbert, Stellenbosch University

The guttural toad (Sclerophrys gutturalis) is a common amphibian found in much of sub-Saharan Africa, from Angola to Kenya and down to eastern South Africa. With such a wide geographic range, and a liking for living in human-disturbed areas, it’s often seen in people’s backyards. Around gardens it can be thought of as a helpful neighbour, as it is a keen predator of insects and other invertebrates that may try to eat plants. Yet it also has the potential to be ecologically hazardous outside its native range – and this toad is an accomplished invader.

In the Mascarene Archipelago in the Indian Ocean, far from mainland Africa, these toads have been an established invasive species for almost 100 years. In 1922, the director of dock management in Port Louis, Mauritius, deliberately released guttural toads in an attempt to control cane beetles – a pest of the country’s major crop, sugar cane. This attempt at biocontrol failed, but the toads appeared to thrive and rapidly spread across the island.

Mauritius had no native amphibian species for it to compete with, and no native predators with a recent evolutionary history with toads. In mainland Africa these toads would have to divide resources, like food, with a host of native amphibians and deal with an array of native birds, mammals and snakes that evolved feeding on them. But without these challenges on Mauritius, the toads colonised the entire island rapidly.

Most toads are generalist predators and hunt a wide variety of prey, more or less eating whatever they can fit in their mouth. So as the guttural toad’s population numbers grew through the decades, so too did the concerns from Mauritian ecologists about the impact on native fauna. Anecdotal accounts as early as the 1930s suggest that the toads were having a negative impact on endemic invertebrate populations. In fact it has been suggested that the toads may have been a driver in the decline, and possible extinction, of endemic carabid beetles and snails.

But it’s only recently that the toad’s diet in Mauritius has been examined closely. In our new study we examined the stomach contents of 361 toads collected in some of the last remaining native forests of Mauritius.

By knowing more about what species the toads are eating, and which groups they favour, our research may help inform toad control actions to protect areas with known sensitive species.

In the belly of the beast

Through our research we were able to identify almost 3,000 individual prey items, encompassing a wide variety of invertebrates like insects, woodlice, snails, spiders, millipedes and earthworms.

This research also went one step further to examine the prey preference of the toads. In general, they seemed to favour, some of the more abundant and common prey species. These included ants and woodlice, which made up about two-thirds of their overall diet.

These findings may suggest that the toads were able to identify a readily available food source, and this may have fuelled their invasive population growth. Yet they are also eating prey that represents a more serious conservation concern.

Inside the toads we found 13 different species of native snail, most of which were island endemics. Four species are listed as being vulnerable to extinction and one, Omphalotropis plicosa, being critically endangered – having been presumed extinct until it was rediscovered in 2002. Understandably, we found it very troubling to find a “Lazarus species” within the stomach of an invasive predator.

Unanswered questions

These early insights into the native species now being hunted by a widespread and voracious predator raise new research questions. To understand the greater impact the toads are having on native species much more work is required to understand their prey’s population dynamics so we can determine if the toad’s invertebrate “harvest” is contributing to declines.

Furthermore, how does the toad’s invasive diet in Mauritius compare with that of other invasive populations, like those in Réunion or Cape Town – is their invasive success linked to a common prey type? And how does it compare with their diet in their own native species range?

Our study could only examine what they are eating currently, but Mauritius has seen numerous species decline over the past 100 years. What role did the toad play in these losses? Perhaps they historically fed more readily on creatures that were more abundant in the past, but had to switch their favour to ants and woodlice when the populations of other species dropped. We may never know.

What is clear is that there is much to learn about the habits of this far-from-home amphibian and its impact on the ecosystems it has invaded.The Conversation

James Baxter-Gilbert, Postdoctoral Fellow, Centre for Invasion Biology (C·I·B), Department of Botany & Zoology, Stellenbosch University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Why microplastics found in Nigeria’s freshwaters raise a red flag



Plastic pollution remains a topmost environmental concern
Pius Utomi Ekpei/AFP via Getty Images

Emmanuel O. Akindele, Obafemi Awolowo University

Freshwater ecosystems are a priority for environmental scientists because they affect the health of animals and plants on land too – as well as people. They provide food, water, transport and flood control. Freshwater ecosystems also keep nutrients moving among organisms and support diverse forms of life.

Freshwater systems make a big difference to the quality of life in any human society. But they are under great pressure. Freshwater biodiversity is declining faster than terrestrial biodiversity.

Among the three major types of habitats – terrestrial, freshwater and marine – freshwater accounts for less than 1% of the earth’s surface. Yet these habitats support more species per unit area and account for about 6% of the world’s biodiversity.

One of the biggest stresses on freshwater ecosystems is the presence of plastics. Some microplastics – tiny pieces of plastic that have broken down from bigger pieces – get into water from various sources. Some are introduced from industrial sources like cosmetics, toothpaste and shaving cream. Another major source is dumping of plastic waste like bags and bottles.

In Nigeria, an important source is the plastic sachets that contain drinking water. Over 60 million of these are consumed in a day.

Ultimately all these types of plastic waste find their way to the aquatic environment. There they stay in the water column, settle on river beds or are ingested by aquatic animals.

My research group set out to assess the load and chemical nature of microplastics in two important rivers and Gulf of Guinea tributaries in Nigeria. We looked for the presence of microplastics in aquatic insects since they often dominate aquatic animal life. Most also spend their adult stage in the terrestrial environment, once they emerge from their larvae. We found that microplastics were present in large quantities in the insect larvae. The insects are part of a food chain and could transfer the harmful effects of microplastics throughout the chain.

This further reinforces the urgent need for Nigeria to go ahead with measures to reduce the use of plastic bags and single-use plastics.

The research findings

We used three of the rivers’ aquatic insect species as bio-indicators and found that all three had ingested microplastics from the two rivers. The ingested microplastics include styrene-ethylene-butylene-styrene, acrylonitrile butadiene styrene, chlorinated polyethylene, polypropylene, and polyester. The quantity of microplastics ingested by the insects was fairly high, especially in the Chironomus sp. which is a riverbed dweller recorded in the Ogun River.

The diversity of plastic polymers recorded in these insects suggests a wide range of applications of plastics in Nigeria.

The three insect species spend their larval stages in the water and later migrate to land in the adult phase. The concern is that the insect larvae could serve as a link for microplastics’ transfer to higher trophic levels in the aquatic environment. Also, the adults serve in the same capacity in the terrestrial environment. A trophic level is the group of organisms within an ecosystem which occupy the same level in a food chain.

Dragonfly larvae in the water are eaten by fish, salamanders, turtles, birds and beetles. Adult dragonflies on land are also eaten by birds and other insects.

Other research elsewhere has shown the link between microplastics and human health.

Through feeding, the transfer of microplastics in the environment could go as far as people – who caused the plastic pollution in the first place.

Evidence suggests that microplastics reduce the physiological fitness of animals. This comes through decreased food consumption, weight loss, decreased growth rate, energy depletion and susceptibility to other harmful substances. Human health could similarly be at risk on account of microplastic ingestion.

Microplastics can be retained for a longer time at the higher trophic levels where humans belong, thereby predisposing humans to serious health hazards.

Case for a plastic bags ban

A ban on plastic bags would curb the plastic pollution in Nigeria. There are alternatives to the use of plastic bags, for instance, bags made from banana stalks, coconut, palm leaf, cassava flour and chicken feathers. Unlike plastic bags, which could persist in the environments for over a century, bags made from these organic materials decompose readily in a manner that does not pose a health risk to the environment.

For a long while, the call to mitigate plastic pollution was not heeded in Nigeria. Recently, the House of Representatives passed a bill banning plastic bags. But this is yet to be implemented as the president has not assented to it.

A study in the European Union indicates that a ban on single-use plastics could reduce marine plastic pollution by about 5.5%.

It is about time Nigeria treated plastic pollution as a national emergency, considering its implications for human health and the ecological integrity of aquatic ecosystems. An approach that puts people at the centre of the issue has been suggested as one way to convince local communities to preserve the integrity of the environment.

Perhaps this approach could help restore plastic-laden aquatic ecosystems and preserve the pristine ones.The Conversation

Emmanuel O. Akindele, Senior Lecturer, Obafemi Awolowo University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Daytime sightings of elusive aardvarks hint at troubled times in the Kalahari



Disappearance of aardvarks from dry ecosystems could have devastating consequences for the many other animals that rely on their burrows.
Kelsey Green

Robyn Hetem, University of the Witwatersrand and Nora Marie Weyer, University of the Witwatersrand

Aardvarks are notoriously elusive, nocturnal mammals. They generally hide in their underground burrows during the day and emerge at night to feed exclusively on ants and termites. Aardvarks are widespread throughout most habitats of Africa south of the Sahara, except deserts. But their actual numbers are not known because they’re so elusive.

Aardvarks top the bucket list of many wildlife enthusiasts, but few have been fortunate enough to see them – until recently. Daytime sightings of aardvarks are becoming more common in the drier parts of southern Africa. But seeing them in the daytime does not bode well because it indicates they might not be finding enough food.

To understand how aardvarks cope with hot and dry conditions, we studied them in the Kalahari, one of the hottest and driest savannah regions in southern Africa in which aardvarks occur. Our study took place at Tswalu, a private reserve in South Africa that supports research through the Tswalu Foundation. We equipped wild, free-living aardvarks with biologgers (minicomputers) that remotely and continuously recorded their body temperature (an indicator of well-being in large mammals), and their activity. Each aardvark also received a radio-tracking device, allowing us to locate them regularly. Tracking the aardvarks provided clues on how they changed their behaviour in relation to environmental stressors in the different seasons and years of our three-year study.

Our study found that in drought periods, aardvarks struggled to find food. It was difficult for them to maintain their energy balance and stay warm during the cool night, so they shifted their active time to the day. Some died from starvation. Given the aardvark’s importance to ecosystems, these findings are a concern.

Comparison of Aardvarks at night and day
Aardvarks usually emerge from their burrows at night (left), but during drought periods, they are increasingly seen during daytime (right).
N. Weyer

Aardvarks are important ecosystem engineers

No other mammal in Africa digs as many large burrows as the aardvark. Dozens of mammals, birds and reptiles use aardvark burrows as shelter from extreme heat and cold, protection from predators, or a place to raise their young. In many of South Africa’s conservation areas, temperatures have already risen by 2℃ over the past 50 years. Further warming by 4-6℃ by the end of the century has been projected.

With deserts and drylands expanding across much of Africa, climate change might threaten the aardvark itself as well as the many animals reliant on aardvark burrows as a cool shelter from rising temperatures.

During typical years, aardvarks were active at night and were able to regulate their body temperature between 35-37℃.

Aardvark active at night during non-drought times
Aardvark active at night during non-drought times.
adapted from Weyer et al., 2020, Frontiers in Physiology, https://doi.org/10.3389/fphys.2020.00637

However, this pattern changed during two severe summer droughts that occurred in the Kalahari during our study. During the droughts, aardvarks shifted their activity to the daytime and their body temperature plummeted below 30°C.

Using remotely-sensed vegetation data recorded by NASA satellites and our own camera trap footage and logger data, we showed that these dramatic changes in body temperature and activity of aardvarks were related to the availability of grass, on which their ant and termite prey rely. When grass was scarce during droughts, the ant and termite prey became inaccessible to aardvarks, preventing them from meeting their daily energy requirements. As their body reserves declined, aardvarks were unable to sustain the energy costs of maintaining warm and stable body temperatures and shifted their activity to the warmer daytime.

Aardvark active in the daytime during drought
Aardvark active in the daytime during drought.
adapted from Weyer et al., 2020, Frontiers in Physiology, https://doi.org/10.3389/fphys.2020.00637

Shifting activity to the warmer daytime while food is scarce can save energy that would otherwise be spent on staying warm during cold nights. But, for our aardvarks, even these energy savings were insufficient during drought, when the ground was bare and the ant and termite prey inaccessible. As a result, seven of our twelve study aardvarks and many others died, presumably from starvation.

A bleak future for aardvarks in a hotter and drier world

On the Red List of Species of the International Union for Conservation of Nature, aardvarks are currently categorised as a species of “Least Concern”. However, we consider aardvarks to be threatened in the drier parts of their distribution in Africa, such as the Kalahari, where climate change brings about droughts. Disappearance of aardvarks from these ecosystems could have devastating consequences for the many other animals that rely on the aardvarks’ burrows.

We hope that our findings will raise further awareness about the consequences of climate change and inform future wildlife conservation and management decisions. Such steps might include assessments of the actual population status of aardvarks across Africa, or mitigation measures to preserve species that depend on burrows for refuge in regions where aardvarks might go locally extinct. More extensive measures, like water-wise reserve management, increasing sizes and connectivity of nature reserves in semi-arid regions, and reducing emissions to mitigate climate change, are just as urgent.

Finally, any solution to the plight of climate change on free-living animals requires a better understanding of their capacities to cope with drought. Therefore, many more long-term comprehensive studies are needed on the physiology and behaviour of the vulnerable animals living in hot, arid regions of the world.

Nora Marie Weyer’s disclosure statement has been updated.The Conversation

Robyn Hetem, Senior Lecturer, University of the Witwatersrand and Nora Marie Weyer, PhD – Wildlife Conservation Physiology, University of the Witwatersrand

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Fires shaped Mount Kilimanjaro’s unique environment. Now they threaten it



Fires on Kilimanjaro, October 2020.
Thomas Becker/picture alliance via Getty Images

Andreas Hemp, Bayreuth University

In October, firefighters in Tanzania had to tackle a number of fires on Mount Kilimanjaro, Africa’s tallest mountain and the largest free-standing mountain in the world. The mountain and surrounding forests fall into Kilimanjaro National Park, named a UNESCO World Heritage site in 1987. Andreas Hemp provides a glimpse into the mountain’s natural environment and the challenges it faces.

Is this the first time there has been a fire of this magnitude? If there have been fires like this before, what damage was done to the mountain’s vegetation and how long did it take it to recover?

Fires are quite common in the higher areas of Kilimanjaro at the end of the dry seasons, around February to March and September to October. Fire can transform land cover, but it also maintains it. Studies that I’ve done with colleagues (using pollen records buried in the soil that go back 50,000 years) showed that fires always played a role in shaping the vegetation belts on the mountain.

For instance, certain species, such as the giant groundsels (Dendrosenecio) became fire-adapted. Also, without fires opening up the forests many light demanding species, such as the famous giant lobelias, would not be able to grow.

There have, however, been several severe fires on Kilimanjaro over the last few decades that have dramatically changed land cover.

Fires in 1996 and 1997 – years with unusually dry seasons – destroyed vast areas of old cloud forest. These are characteristically moist forests in high altitude areas which create unique environments. The forest was replaced by bush. Vegetation has started to recover and shrubs have sprouted, but it’s far from being a forest, which would take at least 100 years to grow without fire. Since these old forests have an important function of fog water collection, the loss of these forests means a serious impact on the water balance of the mountain, much larger than the impact of the melting glaciers, which is ecologically negligible.

The impact of these former fires was much bigger than that of the recent one, which “only” affected bush land and not forest.

What type of vegetation exists on Mt Kilimanjaro and how unique is it?

Due to its enormous height, Kilimanjaro has several distinct vegetation belts.

It is surrounded on the foothills by cultivation with a unique mix of agriculture, savanna and forest. This harbours very rich biodiversity as well as the tallest trees on the continent.

Higher up the mountain – between about 1,800 and 3,000 metres – a montane forest belt encircles the whole mountain. This is one of the largest forest blocks in East Africa.

Even higher up, between 3,000 and 4,000 metres, there’s a heathland belt typical of the high mountains in East Africa. This vegetation consists of Erica, Protea, Stoebe and many other shrub species, many of them are endemic, occurring only on one or several mountains.

Erica shrubs burn very easily, which makes this vegetation belt particularly flammable. During wet periods without fire, the former forest can re-establish and expand to the tree line at 4000m. During dry periods, with recurring fires (natural and or caused by people), the forest belt shrinks and the ericaceous belt expands.

What challenges does the mountain’s natural environment face and have there been any noticeable changes over the years?

Over the last 150 years, the regional climate has become drier. This has caused the mountain’s glaciers to shrink by almost 90% of their former extent. The drier climate is also the reason for an increase in the frequency and intensity of wild fires in the upper areas of Kilimanjaro, affecting the forests.

Most of these fires are lit by people (such as honey collectors smoking out bees), but these fires would not have been so devastating if the climate was wetter.

There’s an interplay between direct anthropogenic (caused by people) and climatic impacts.

Since 1911 the human population on Kilimanjaro has increased from 100,000 to over 1.2 million. This has resulted in an enormous loss of natural vegetation. Kilimanjaro is becoming an ecological island, isolated and surrounded by agriculture. Over this period it has lost 50% of its forest cover. In the lower areas this is mainly due to logging and clearing. In the upper areas it’s due to fires.

In combination with global climate change, this forest destruction results in a decrease of moisture in the region. This will also affect agriculture in the region because it’s partly irrigated.

Who is responsible for protecting the mountain and how well protected is it?

In 2005, the forest belt was incorporated into the mountain’s existing national park area. This means that it falls under the responsibility of the Tanzania and Kilimanjaro National Park authorities. The forest belt is much better protected than it was before, as a forest reserve.

The banning of camp fires on the tourist routes by the national park authorities helped to reduce the fire risk. But it’s not possible to exclude the risk in this large heathland belt totally. Perhaps the acquisition of larger fire-fighting airplanes could help. Fires are usually fought by hundreds of volunteers and firefighters, using shovels and machetes creating fire breaks by hand. This recent fire was the first time that a helicopter was used to carry water from nearby dams.

What else can be done?

To protect the biodiversity of Kilimanjaro the unique forests of the larger deep river valleys below the National Park should be incorporated into the National Park. Kilimanjaro is becoming an ecological island completely isolated and surrounded by agriculture. This inhibits the exchange of animal populations and affects biodiversity.

It’s all the more important that the wildlife corridor connecting the Amboseli ecosystem in Kenya and Kilimanjaro National Park has to be well protected. It is under great pressure due to grazing and agriculture. This corridor is important for the migration of elephants, which stay now more and more on Kilimanjaro destroying the forest.The Conversation

Andreas Hemp, Research Associate Plant Systematics, Bayreuth University

This article is republished from The Conversation under a Creative Commons license. Read the original article.