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There are new hopes for the survival of the Tasmanian devils in danger after a large number of people have been killed by facial tumors.
The largest carnivorous marsupials in the world have been battling Devil's Facial Tumor Disease (DFTD) for more than 20 years.
But the researchers discovered that the animal's immune system was changing to fight the badault.
And according to an international team of Australian, British, American and French scientists, the future of demons is more promising.
"In the past, we managed the devil populations to avoid extinction." We are moving gradually to an adaptive management strategy, reinforcing these selective adaptations for the evolution of devil coexistence / DFTD, "says Dr. Rodrigo Hamede of the University of Tasmania. .
Discovered for the first time in northeastern Tasmania in 1996, the disease has since spread to 95% of the species' range, resulting in higher local population loss. at 90%.
Dr. Hamede's team has collected epidemiological evidence over the last 10 years. The group has mapped scenarios based on current infection rates in nature and, in their predictions for the next 100 years, 57% of scenarios predict a gradual weakening of the DFTD and 22% prediction of coexistence .
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Dr. Max Stammnitz
Tumors can reach half the size of the face
How is the disease spread?
The disease is spread when the devils bite their face during fights.
Mordant behavior is a means of socializing and baderting its dominance which, along with shouts resembling a grunt, has allowed the devils to earn their nickname.
"Our current hypothesis is that bites do not only lead to the spread of tumors, but can be the starting point," says Max Stammnitz, of the University of Cambridge in the UK, who sequences the genomes of you die.
"If the process of healing recurrent wounds is interrupted by a mutation, it can become cancerous, it does not heal, and it starts to develop in an external tissue that can become transmissible," says Stammnitz.
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After the bite, a solid tumor then develops around the face or neck, with the power to fracture the bones of the jaw – killing the animal after 6 to 24 months.
To aggravate the crisis, in 2014, a second transmissible cancer (DFT2) was discovered in wild populations of the south of the island.
"A second transmissible tumor in demons was extremely surprising, like a lightning bolt that hits demons twice," says Dr. Hamede.
But for five or six years, some demons have developed greater tolerance for infections and even resistance without human intervention, which means that if the population has not regained its pre-DFTD level, the decline has less stabilized.
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Max Stammnitz
DFTD can move teeth or protrude through the eyes and nostrils of the animal
How does natural selection help?
"Natural selection tries to solve the problem itself by favoring those who can survive the tumor, so we're more optimistic than ever before," says Dr. Hamede.
The international team monitors every three months eight sites located in the east, south and west of the island, observing several generations of devils.
"We have witnessed how these tumors shape the ecology of demons and their evolution in real time with their hosts," said Dr. Hamede.
Demons can now adapt to transmissible cancer at the genetic and phenotypic levels – that is, DNA and trait traits. This is due to their phenotypic plasticity – the ability of an individual organism to alter its physiology or the expression of its genes in response to changing environmental conditions. And what's even more unique is the speed with which it happened – in the space of 16 years, in just eight generations of the devil.
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Manuel Ruiz Aravena
In some animals, tumors (inlays) have completely regressed without any human intervention
"It is a constant arms race between animals and diseases, and we are developing resistance mechanisms that cause pathogens to improve infections," Stammnitz said.
The first of these mechanisms is tolerance and the second is resistance.
The team discovered demons who had been living with the disease for at least two years, allowing two additional litters to serve as population recruitment for the disease.
In addition, 23 cases of tumor regression have been discovered so far – showing that devils also have the ability to fight and recover from the DFTD.
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Max Stammnitz
To study animals, researchers must first catch them
What is the future of the devils?
The second biggest threat to devils is road mortality, with a minimum of 350 to 450 devils each year, according to Dr. Fox's Save the Tasmanian Devil (STDP) program.
By targeting hot spots, the PDTS has installed a fence that sounds the alarm and warns wild animals of approaching cars. The current trail has resulted in a 50% reduction in road deaths since 2015.
The number of affected devils dropped by a quarter and Tasmanian pademelons and Bennett's wallabies also benefited.
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Max Stammnitz
Humane traps are used by the team
The government is also following a new application since July that the public can use to report observations to monitor populations.
Until now, the application has been downloaded by more than 2,000 users who have registered 6,000 reports.
"When we watched the start of the DFTD in 2003, information about road accidents by the public taught us where it had spread, demonstrating the power of citizen science to help demons, "adds Dr. Fox.
In the curious case of the Tasmanian devil, much remains to be learned about cancer biology and the evolving arms race between malignant cells and their hosts.
The speed of decline has created a strong selective pressure on the largest remaining carnivorous marsupial in the world, but it now seems that hope could lie in coexistence.
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Max Stammnitz
Once the samples are taken, the devils are then released into the wild
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