The Research Brief is a short take on interesting academic work.
THE BIG IDEA: Coyotes are poised to expand their range to a new continent. The North American canine native has now reached the Darién Gap – a dense wilderness on the border of Colombia and Panama, at the very doorstep of South America. If the coyote succeeds, it would be a new chapter in an amazing evolutionary story that’s played out over the past half century.
WHY IT MATTERS: The historical range of the coyote was originally from western Canada to Mexico. But over the past few decades, it has mixed with wolves and dogs, and its adaptability has allowed the species to expand both east and south, making them commonplace everywhere from New York City to Panama City. My colleagues and I study how humans affect the distribution of wildlife on the planet. Usually this is in a negative way – some endangered species are declining because humans are destroying their habitat or hunting them to near extinction. However, some species are quite good at dealing with the changes people bring to the landscape, and coyotes are an example.
WHAT STILL ISN’T KNOWN: If coyotes will actually reach South America, or if jaguars in the Darién will keep them out. Few coyote biologists, including myself, are betting against the coyote. We also don’t know if coyotes, presuming they make it to South America, will have a negative impact on wildlife there. These native species already live with other canine predators in South America, including foxes, so the coyote might not be so bad for native species. People with free-ranging chickens, however, may think that is a different matter!
HOW I DO MY WORK: We set up camera traps, then go back to see what images they captured, and enter everything in a database called eMammal. It’s great to visit a place, see it with your own eyes and speculate about what might be there. Then, a few weeks later, pick up the camera and see all these animals for yourself. Checking the camera memory card is like Christmas every time.
ONE OTHER THING HAPPENING IN THE FIELD: Ricardo Moreno of Yaguara works to save the jaguar in Panama. He is monitoring the Darién to see how the jaguars are doing and working with locals to prevent poaching. He is also running cameras to see if the coyotes move into the Darién.
WHAT’S NEXT FOR YOU: We have just completed #SnapshotUSA, a survey of wildlife across all 50 states, including lots of coyotes! We are in the process of going through the 6 million photos now to identify all the species. We are also working with Wildlife Insights, a data collection site for pictures of wildlife around the world, and Google to develop artificial intelligence to help process all these pictures we get. Maybe this will help us keep an eye on how the coyotes do in Panama.
South American horned frogs (Ceratophrys) can capture and swallow whole animals up to their own body size, including other frogs, lizards, snakes and rodents. This is possible because they have jaws that can produce an extremely forceful bite.
Just how powerful is the bite was part of our study, published today in Scientific Reports. We found that small horned frogs – with a head width of 45mm – can bite with a force of 30 Newtons (N). That would feel like having three litres of water balanced on the end of your fingernail.
More impressively, the largest horned frogs from Brazil – with a head width of 100mm – are calculated to bite with a force of 500N. That’s like having 51 litres of water balanced on your fingertip.
A bite like this is similar to that of reptiles and mammals with heads of similar size.
Measuring bite force
Bite force was measured using a special device called a force transducer. Unlike most frogs, horned frogs willingly open their mouths and bite objects (or fingers) as a defensive response.
This makes it easy to place the free ends of the device into the frog’s mouth so that it bites forcefully, and the device measures the amount of applied force. The free ends of the device are covered in leather to protect the animal’s jaws and to provide a naturalistic gripping surface for the teeth.
Our study is also unusual in that the relationship between size and bite force was measured using multiple measurements from the same individuals from different points during their growth rather than just using a sample of different-sized individuals.
If just out of reach, the horned frog may lift one or both rear legs over its head and wiggle its toes to attract the attention of the potential meal. Once the victim is in range, the frog will rapidly lunge forwards with a wide open mouth.
The extremely adhesive tongue sticks to the prey and retracts, pulling the prey into the mouth, and the huge jaws clamp shut with great force to prevent escape.
Associated with the impressive bite forces of horned frogs and their ambush lifestyle are several important anatomical traits. They have a heavily built skull in which many of the connections between individual skull bones fuse together as the animal grows.
The horns in horned frogs are small pointed structures above the eyes. Their prominence varies among species, and they may help to camouflage the frogs by looking like the tips of the leaves on the forest floor where they sit in wait for prey.
Horned frogs are not currently considered endangered but some species are considered near threatened. Like many animals they are suffering a loss of natural habitat. They are also often killed by local people because of false beliefs that they are venomous, and collection for the pet trade may also be significant.
A prehistoric frog with a bigger bite
Bite forces of some ancient frogs may have been even more impressive than those of today’s South American horned frogs.
Beelzebufo ampinga is a large heavily built frog from the Late Cretaceous period of Madagascar with a skull at least 150mm wide.
Detailed comparisons with the available skeleton suggest that its closest living relatives might be the South American horned frogs. When the relationship between bite force and size in the South American horned frogs is applied to the skull width of Beelzebufo the value obtained is 2,200N. That’s a massive 224 litres of water balanced on a fingertip – more than three times the weight of an average Australian woman.
A bite of this force is comparable to estimates for mammalian predators such as wolves and female lions, and within the realm of bite forces measured for crocodiles and turtles with similar skull widths.
For context, the bite force of an adult human male averages only about 25% that of a large Beelzebufo. With a bite like that, Beelzebufo would have been capable of easily overcoming small or juvenile dinosaurs that shared its environment.
The Amazon, often described as the “lungs of the Earth”, is the largest rainforest in the world. Its extraordinary biodiversity and sheer scale has made it a globally significant resource in the fight against climate change.
The reserve, known as “Renca”, covers 46,000 square kilometres and is thought to contain huge amounts of copper, as well as gold, iron ore and other minerals. Roughly 30% of Renca will now be open to mining exploration. Renca also includes indigenous reserves inhabited by various ethnic communities living in relative isolation.
Brazil is currently in the middle of the largest corruption scandals in its history. Since 2014, an ongoing federal investigation called Operation Car Wash has implicated elite businesspeople and high-ranking politicians, uncovering bribes worth millions of dollars exchanged for deals with the state oil company Petrobas. According to the BBC, almost a third of President Temer’s cabinet is under investigation for alleged corruption.
There is no doubt that Brazil needs to find ways out of recession and unemployment. As the minister of mining and energy has said, “the objective of the measure [to allow mining] is to attract new investments, generating wealth for the country and employment and income for society.”
However it’s not clear that this move will benefit ordinary Brazilians. This is not the first gold rush into this area, and the Amazon still has high indices of poverty and many other challenges.
During the 1980s and 90s tens of thousands of miners flocked to gold deposits in the Amazon, driven by high international prices. One of the most famous examples, “Serra Pelada,” saw 60,000 men dig a massive crater in the Amazon Basin.
In reality the Amazon and its people deserve a sustainable model of development, which takes advantage of the outstanding biodiversity and beauty of its standing forests. The historical record shows mining is likely to lead to a demographic explosion, and further deforestation, pollution and land conflicts.
The principle of non-regression
One important aspect of international environmental law is called the “principle of non-regression”. The principle states that some legal rules should be non-revokable in the name of the common interest of humankind. Essentially, once a level of protection has been granted there is no coming back.
While the Amazon is a fundamental part of Brazil’s history, it’s also an essential part of the global battle against climate change. The Amazon contains half the worlds’ tropical rainforests, and its trees absorb and store vast amounts of carbon dioxide.
Developed countries around the world have committed resources to help Brazil offset the costs of safeguarding their forests. One example is the Amazon Fund, created in 2008. It has received billions of dollars from foreign governments such as Norway and Germany, to combat deforestation and to promote sustainable practices in the Brazilian Amazon.
As well as governments, companies have also committed billions of dollars to fight climate change and support projects that reduce carbon emissions and promote energy efficiency. Most businesses have also created self-regulatory standards to ensure compliance with international laws and ethical standards.
The decision of the Brazilian government leaves us with two questions. How will the international community honour their commitments to keep global warming below 2℃, if countries begin rolling back their environmental protections? And how will companies involved in mining projects in the Amazon honour their social responsibility commitments and moral obligation towards present and future generations?
The degradation of the Amazon will affect the entire world. The clearing of the Amazon for mining will lead to the emissions of thousands of tons of greenhouse gases, furthering global warming and causing the irreversible loss of biodiversity, and water resources, as well as damage to local and indigenous communities.
Let us not take a step back towards more destruction. Rather, let us strengthen the protection of our remaining forests.