Science

• Lost to science for more than a century, the Omiltemi cottontail rabbit has been confirmed by scientists to be alive and hopping in southern Mexico.
• The species was rediscovered via interviews with local communities and footage from camera traps intended to photograph jaguars.
• Sierra Madre del Sur in the state of Guerrero is the only place in the world where the Omiltemi cottontail is known to exist.
• Satellite data show continued forest loss within its known range, while hunting for food by local communities remains another threat to the species.

Footage captured in 2024 of a small rabbit hopping about in front of a camera trap had scientists baffled. The juvenile, with gray-brown fur and a black tail, didn’t resemble any known species in the Sierra Madre del Sur, in the southern Mexican state of Guerrero.

Biologist Fernando Ruiz-Gutiérrez anxiously searched his records and consulted with colleagues to confirm his hypothesis. A few kilometers away, ecologist José Alberto Almazán-Catalán had the answer: having captured an adult specimen years earlier and conducted a series of studies, he now had irrefutable proof that the Omiltemi cottontail rabbit (Sylvilagus insonus), believed to be extinct for the past 120 years, was still alive.

The last time scientists knowingly encountered the Omiltemi cottontail was in 1904, when U.S. naturalist Edward William Nelson described it for the first time. Habitat loss, poaching and subsistence hunting have been the biggest threats to the species throughout its existence, which is why it took more than a century to rediscover the elusive rabbit, hidden in the forest.

“It was very exciting to pin down an animal that we not only believed to be extinct but that also has an almost mythical quality, because the furs we have in Mexico are not as precise as we would like since they were not taken by a mammalogist but donated by campesinos [small-scale farmers],” says Almazán-Catalán, president of the Institute for the Management and Conservation of Biodiversity (INMACOB), a Mexican NGO.

“We really weren’t sure this rabbit existed. It could’ve been an anomaly. Finding it was alive and that there were healthy populations was a great relief,” says Almazán-Catalán, who led a five-year investigation to discover the continued existence of the species.

The Omiltemi cottontail rabbit is endemic to the state of Guerrero. Its previously known distribution was restricted to the area around the village of Omiltemi, in the municipality of Chilpancingo. An elusive species with nocturnal habits and low population densities, it’s classified as endangered by Semarnat, Mexico’s environment ministry, and very little is known about its distribution, ecology and biology.

Ruiz-Gutiérrez, who led a team that helped rediscover the Omiltemi cottontail, calls it the most endangered rabbit in the world, saying the species was even considered to be an example of modern-day extinction.

Members of a research team walk through a pine-oak forest, one of the habitats in which they carried out monitoring activities. Image courtesy of Wild Felids Conservation México.

Like other rabbits, Omiltemi cottontails live in warrens, and primarily inhabit coniferous forests, but can also be found in some deciduous forests, at elevations ranging from 7,000-10,000 feet (about 2,100-3,000 meters).

“They are rich and generally very diverse territories, with a wide variety of plants and animals. This mountainous region is well preserved, with forests that haven’t been disturbed for many years, which still have primary forest cover and haven’t been greatly impacted by human activity,” Ruiz-Gutiérrez says.

“We’ve found areas with beautiful, pristine rivers, with an impressive quantity of crystal-clear water, with areas of very dense forest which are difficult to access and other areas where there is human intervention, but not very often. It’s in these places that we’ve had sightings of the Omiltemi rabbit,” Ruiz-Gutiérrez says.

The mountains of Guerrero are made up of rugged and varied landscapes that support a rich diversity of species. Image courtesy of Wild Felids Conservation México.

The Omiltemi cottontail is reddish-brown in color, and its body and ears are smaller than those of other rabbits that inhabit the area. But Almazán-Catalán says that the most obvious feature that distinguishes the species from the closely related Mexican cottontail (S. cunicularius), which inhabits the same area, is its small black tail.

“It’s difficult to see it in a camera trap, but with a good photo you might be able to recognize that it’s a different rabbit,” Almazán-Catalán says. “The first clear photo of the Omiltemi cottontail rabbit is from 2009, taken by photographer Stephen John Davies, from the United Kingdom, who came to Puerto del Gallo and created a controversy [about the rabbit’s continued existence] on the iNaturalistMX website, which is where the first debate about what animal it was took place.”

Photograph of an Omiltemi cottontail rabbit taken in 2009 by photographer Stephen John Davies, in Guerrero. Image courtesy of Stephen John Davies/iNaturalistMX.

Field crew members install and test a camera trap. Image courtesy of Wild Felids Conservation México.

The rediscovery of the Omiltemi cottontail after more than a century was accidental. Ruiz-Gutiérrez and his team had been setting up camera traps along wildlife trails to monitor jaguars (Panthera onca) in the central portion of the Sierra Madre del Sur as part of the National Jaguar Census (Cenjaguar).

“We use the camera trap to identify the presence of jaguars, but also any associated fauna, that is, its potential prey and other felines with which they cohabit,” Ruiz-Gutiérrez says. “From this we can generate estimates of species richness and biodiversity in general, and, in particular, population aspects of the jaguar in this region, which are then extrapolated to a state and national level, giving us the data we use for Cenjaguar.”

And then, one day in May 2024, a mysterious young rabbit appeared in front of a camera trap set up in the forest near the village of Jaleaca de Catalán.

“It really caught our attention because, when you compare it to other animals in footage from the same camera, the rabbit is tiny. We got a photo of a squirrel just opposite the place where the rabbit was and, when we put them next to each other, they were the same size,” Ruiz-Gutiérrez says. “So we began to talk about it seriously with Dr. Gerardo Ceballos, director of Cenjaguar; I sent him all the evidence and with it we were able to ascertain that it really was the mythical Omiltemi cottontail rabbit, and we began to get excited about this important discovery.”

A composite image showing a squirrel and the Omiltemi cottontail rabbit. Image courtesy of Wild Felids Conservation México.

When Ruiz-Gutiérrez and his team went over archive camera-trap footage from the past 11 years, they found additional photos and videos of Omiltemi cottontails captured in the municipalities of Atoyac, Chilpancingo and Técpan de Galeana. This footage indicates the distribution of the species extends 111 kilometers (69 miles) beyond what was previously known, from Omiltemi to the Técpan de Galeana mountains.

“We were delighted to be able to rediscover the presence of this species, to confirm that it’s still alive and continues to have small populations in the Guerrero mountains,” Ruiz-Gutiérrez says. “We need to redouble our efforts to conserve it in the medium and long term, working with communities on conservation strategies that will help us to protect it so that it won’t yet disappear from the face of the Earth.”

By analyzing their camera-trap footage more closely, Ruiz-Gutiérrez and his team were able to glean information about the behavior of the Omiltemi cottontail. For example, 68% of sightings were at night, indicating the species may be largely nocturnal.

Most images captured were of single individuals, suggesting the species is mostly solitary. There were sightings of juvenile individuals, or kits, in May and December, which indicates breeding activity may take place twice a year.

An Omiltemi cottontail rabbit foraging with its back to the camera trap. Image courtesy of Wild Felids Conservation México.

While camera-trap footage indicate the distribution of the Omiltemi cottontail is broader than previously expected, the threats facing the species — habitat loss driven by fires and agricultural clearing — still persist, and little is known about the impact of hunting by local communities, according to the research team.

Portions of the rabbit’s range fall within several protected areas, including the new Sierra Tecuani Biosphere Reserve. However, satellite data from Global Forest Watch show ongoing forest loss in the reserve, and there were “no special conservation measures to protect the species” as of January 2025, according to conservation NGO Re:wild.

Community technician Pascual Ramírez and Wild Felids Conservation México biologist Gricell Villegas install a camera trap. Image courtesy of Wild Felids Conservation México.

“It’s a huge opportunity for us to be able to contribute to the conservation of such an enigmatic species,” Ruiz-Gutiérrez says. “All this work has been thanks to conservation of the jaguar, which was the flagship species that opened the door to us beginning to study and protect it, but most of the conservation work we can do must be done together with the ejidos [community-managed farmland] and communities.”

The Omiltemi cottontail is the 13th species rediscovered as part of Re:wild’s “Search for Lost Species,” a project aiming to find and protect plant, animal and fungi species that have been lost to science for years but not yet been declared extinct.

When Almazán-Catalán and his team began searching for the rabbit in 2019 in the forests of Chilpancingo, they didn’t find any sign of the species. So from 2020-2022, they refocused their search to high-altitude coniferous forests. There, in the Filo Mayor region, they consulted with local communities where they suspected the Omiltemi cottontail and another rabbit species were hunted for food by community members.

“The campesinos had three specimens of S. insonus in their possession and gave them to us for scientific purposes when we explained why we wanted the fur and their tissues,” Almazán-Catalán says. “They had the animals for personal consumption and donated them to the investigation. The community weren’t to blame; they simply didn’t know it was Sylvilagus insonus.”

• The Wild Felids Conservation México technical team and the Jaleaca de Catalán community team, who participated in the fieldwork that led to the rediscovery of the Omiltemi cottontail rabbit. Image courtesy of Wild Felids Conservation México.

1

2

3

4

When the research team compared the communities’ rabbits with the furs available in collections and descriptions in the scientific literature, their morphological characteristics matched those of the Omiltemi cottontail rabbit first described by Nelson in 1904.

“This finding suggests that we still have a lot of fieldwork to do because although we think we have all the species documented, this really isn’t the case. We need to get more people involved, more specialists in this area,” Almazán-Catalán says. “It was a joy to behold this small animal and to discover that it’s there, alive, that it’s still hopping about, and we hope that there will be many more sightings and that it will continue to inhabit this region of the Guerrero mountains.”

Banner image: Omiltemi cottontail rabbit foraging in front of a camera trap. Image courtesy of Wild Felids Conservation México.

This story was first published here in Spanish on April 5, 2025.

Sihao Cheng at the Institute for Advanced Study in Princeton, New Jersey, and his colleagues first detected the object, known as 2017 OF201, as a bright spot in an astronomical image database from the Victor M. Blanco Telescope in Chile.

2017 OF201 is about 700 kilometres across – big enough to qualify as a dwarf planet like Pluto, which has a diameter about three times as big. The object is currently about 90.5 astronomical units (AU) away from us, or roughly 90 times as far from Earth as the sun is.

Because 2017 OF201’s average orbit around the sun is greater than that of Neptune, it is what’s known as a trans-Neptunian object (TNO). It passes through the Kuiper belt, a disc of icy objects in the outer solar system beyond the orbit of Neptune.

The researchers looked back over 19 observations, taken over seven years by the Canada France Hawaii Telescope, to determine that the closest 2017 OF201 gets to the sun – its perihelion – is 44.5 AU, which is similar to Pluto’s orbit. The furthest it gets from the sun is 1600 AU, way outside the solar system.

This far-flung orbit may be the result of an encounter with a giant planet, which ejected the candidate dwarf planet out of the solar system, say the researchers.

“It’s a really cool discovery,” says Kevin Napier at the University of Michigan. The object would go so far outside the solar system that it could be interacting with other stars in the galaxy just as strongly as it interacts with some of the planets in our solar system, he says.

The orbits of many extreme TNOs seem to cluster in a specific orientation. This has been interpreted as evidence that the solar system contains a ninth planet hidden in the Oort cloud, a vast cloud of icy rocks encircling the solar system. The idea is that Planet 9’s gravity pushes the TNOs into their specific orbits.

But the orbit of 2017 OF201 doesn’t fit this pattern. “This object is definitely an outlier to the observed clustering,” says team member Eritas Yang at Princeton University.

Cheng and his colleagues also modelled simulations of the object’s orbit, and how it might interact with Planet 9. “In the one with Planet X, the object gets ejected after a couple of hundred million years, and without Planet X, it stays,” says Napier. “Certainly, this is not evidence in favour of Planet 9.”

But until there is more data, the case isn’t closed, says Cheng. “I hope Planet 9 still exists, because that’ll be more interesting.”

The candidate dwarf planet takes roughly 25,000 years to complete an orbit, which means it spends only about 1 per cent of its time close enough to Earth for us to detect it. “These things are really hard to find because they’re faint, and their orbits are so long and skinny that you can only see them when they’re really close to the sun, and then they immediately head right back out and they’re invisible to us again,” says Napier.

That means there might be hundreds of such objects out there. The Vera C. Rubin Observatory, due to go online later this year, will look deeper into space and will potentially detect many more objects like this, which should tell us more about them – and whether Planet 9 actually exists.

Living within one mile of a golf course doubles the risk of developing Parkinson’s, a new study suggests.

US researchers believe pesticides used to keep greens and fairways in immaculate condition could be triggering the condition by leaching into water supplies or becoming airborne.

In new research, a team from the Barrow Neurological Institute, Arizona analysed health data from people living near 139 golf courses in southern Minnesota and western Wisconsin.

They discovered that living within one mile of a golf course was associated with a 126 per cent higher risk of developing Parkinson’s compared with individuals living more than six miles away.

The study also found a linear relationship between the chance of developing Parkinson’s and distance from the greens, with each mile away reducing the chances of diagnosis by 13 per cent.

Writing in the journal Jama Network Open, Dr Brittany Krzyzanowski said: “These findings suggest that pesticides applied to golf courses may play a role in the incidence of Parkinson’s disease for nearby residents.

“Public health policies to reduce the risk of groundwater contamination and airborne exposure from pesticides on golf courses may help reduce risk of Parkinson’s disease in nearby neighbourhoods.”

The overall chance of developing Parkinson’s is small, with about 0.005 per cent of people in their 30s diagnosed, rising to about 1.7 per cent of people in their 80s.

Previous studies have suggested that exposure to pesticides such as organophosphates raise the risk of the condition, and in 2011 the US National Institutes of Health warned that rotenone and paraquat in particular multiply the risk of Parkinson’s by 2.5.

That study found the pesticides can inhibit the function of the mitochondria, the structure responsible for making energy in the cell, as well as causing oxidative stress that can harm cellular structures. Seven pesticides in groundwater

There is also evidence that pesticides from golf courses can pollute groundwater. A study of water courses surrounding four different golf courses in Cape Cod, Massachusetts discovered that they were contaminated with seven different pesticides including those linked to Parkinson’s.

But although there has been anecdotal evidence that living near golf courses may increase the chance of Parkinson’s and cancer, there have been no major studies until now.

The latest research looked at nearly 4,500 people who lived in the vicinity of golf courses, including 418 Parkinson’s patients.

It found a clear link for those living within three miles of a golf course, with the risk decreasing as people moved farther away. The effects were strongest in residential areas that shared their groundwater with a golf course.

Britain has traditionally used fewer pesticides on golf courses than the US, and recently banned the most harmful chemicals.

Experts at the charity Parkinson’s UK also pointed out the disease starts in the brain 10 to 15 years before diagnosis, so the seeds may have been planted long before people moved near a golf course.

Dr Katherine Fletcher, the research lead at Parkinson’s UK, said: “Parkinson’s is complex. The causes of the condition are unclear and are likely to involve both genetic and environmental factors.

“Many studies have investigated whether pesticides increase the risk of developing Parkinson’s in different populations around the world. The results have been varied, but overall suggest that exposure to pesticides may increase the risk of the condition.

However, the evidence is not strong enough to show that pesticide exposure directly causes Parkinson’s. In Europe and the UK, the use of pesticides is strictly controlled, and some – like paraquat – are banned, due to concerns about their wider health and environmental impacts.

“So, the risk of exposure to these for most people is extremely low.”