Tag Archives: mammals

Giant Crocodylians Dominated South America’s Miocene Food Chain, Study Finds

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South America was home to a formidable collection of predators more than 10 million years ago, when a vast lake covered much of the continent and supported giant turtles, crocodylians and an extraordinary range of prey.

New research suggests that crocodylians, rather than mammals or other land-based predators, were the most important predators in these ancient ecosystems, particularly when it came to hunting large animals.

The findings are based on an analysis of fossil remains dating from about 10.5 million to 16 million years ago. Researchers examined bite and tooth marks preserved on herbivore fossils, providing direct evidence of interactions between predators and their prey.

A Seven-Metre Predator at the Top

The Miocene lake system supported an abundance of large herbivores, including giant ground sloths, glyptodonts — ancient relatives of modern armadillos — and several groups of large hoofed mammals.

Some of these animals, including astrapotheres and toxodontids, could weigh more than a tonne.

They shared the ecosystem with an equally imposing group of predators. Among the most formidable was Purussaurus neivensis, a giant crocodylian related to modern caimans. It could reach about seven metres in length and weigh as much as 1,800 kilograms.

Other predators included anacondas, saber-toothed mammals, flightless terror birds and sebecids, which were terrestrial relatives of modern crocodylians.

Despite this diversity, the study indicates that crocodylians were particularly important predators in the ancient ecosystem.

Fossil Bite Marks Tell the Story

Researchers from the University of Helsinki studied bite and tooth marks preserved on fossilized remains of herbivores. Such marks can reveal which predators attacked or scavenged animals, even when the predator itself is not preserved alongside its potential prey.

The frequency and characteristics of marks attributed to Purussaurus suggest that the giant crocodylian played a major role in the tropical food web.

Oscar Wilson, a postdoctoral researcher at the University of Helsinki, said the abundance of prey was so great that mammalian predators alone would not have been capable of consuming it all.

The evidence indicates that crocodylians filled an important ecological role, particularly by targeting large-bodied prey.

The findings also raise the possibility that Purussaurus influenced herbivore populations. As one of the largest predators in the ecosystem, the giant crocodylian may have exerted substantial pressure on large herbivores and helped shape the structure of the ancient food web.

The study provides a glimpse into an ecosystem where enormous predators and prey lived alongside one another — and where giant crocodylians may have occupied a position closer to the top of the food chain than previously recognized.

 

Also Read:

Crocodiles Set to Face Extinction, Says Australian Researcher

‘Nagatitan’: Southeast Asia’s biggest long-necked dinosaur discovered

 

Aardvarks’ fate points to worrying consequences for wildlife, due to climate change

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The aardvark, a highlight for anyone on a game-viewing African safari, will become increasingly rare as the world warms and dries, and the consequences go well beyond a decline in aardvark safari encounters.

According to researchers studying this elusive mammal, sometimes classed as one of the “Shy 5”, in South Africa’s Kalahari Desert, aardvarks prove to be highly susceptible to the warmer and drier climates that are predicted for the western parts of southern Africa, in the future. During the study of a number of aardvarks by researchers of the Brain Function Research Group at the University of the Witwatersrand, all but one of the study animals – as well as other aardvarks in the area – died because of a severe drought, with air temperatures much higher than normal and very dry soil in the area.

“While unusual now, those are the conditions that climate change is likely to bring as the new normal,” says Professor Andrea Fuller, the Research Group’s director.

Dr Benjamin Rey studied the aardvarks as part of his postdoctoral studies. Along with his colleagues, he used the new technology of “biologgers” (miniature sensors attached to computer chips and implanted into the aardvarks by wildlife veterinarians), to study the activity patterns and body temperatures of aardvarks living in the Kalahari. The researchers were not to know that during the year of their study there would be a severe drought, which led to the death of the study animals.

“It is not because the aardvark’s body can’t take the heat, but that the termites and ants that they rely on – not just for food but also for water – can’t take the heat and aridity of changing climates,” says Rey.

Aardvarks usually sleep during the day in burrows that they have dug, and emerge at night, to feed on ant and termites, using their long, sticky tongues to sweep up thousands of insects. However, during the drought, the termites and ants, on which the aardvark depends for body energy, were not available.

“As a result, the aardvarks’ body temperatures fell precipitously at night. The aardvarks tried to compensate by shifting their search for ants and termites from the colder night to the warmer day, so that they would not have to use energy to keep warm, but that was not enough to save their energy stores,” says Dr Robyn Hetem, a co-worker on the study. “We believe the aardvarks starved to death.”

The aardvark progressively became skinnier and bonier. They even tried sun-basking to save energy, but many ultimately died. Their body temperatures dropped to as low as 25°C just before they died.

Rey says that this curious-looking creature – described as having the snout of a pig, the ears of a rabbit and the tail of a kangaroo – is much more than just a curiosity to be checked off a bucket list.

“Many species of African birds, mammals and reptiles use the burrows dug by aardvarks to escape cold and heat, to reproduce, and to avoid predators. They can’t dig these burrows themselves. Without aardvarks, they would have no refuge. Worryingly, they could face the same fate as the aardvark.”

Climate change in southern Africa affects animals through the direct effects of increasing air temperatures and aridity. Wild dogs, for example, reduce hunting activity as temperature increases. But the indirect consequences of heat and aridity may be more pervasive. Disappearance of aardvarks, and with them the burrows that they dig, will have knock-on effects for many other animals.