When eyeing a predator, horses keep a poker face as their hearts race

Study: Equines recognize friend v. foe with visual cues alone

Ohio State University

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A handler holds onto a horse while a researcher sets up the projector and videos. The handler will turn her back to the stimulus during videos while still holding the horse by the animal’s harness. The researcher will leave the stall before the video presentations begin to operate the equipment remotely.

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Credit: Photo: Zeynep Benderlioglu

COLUMBUS, Ohio – Horses know a predator when they see one – even if it’s only on a video screen they’re watching in a stall, with no sounds, smells or previous experience providing context to what they’re viewing, a new study suggests.

And though sensors indicated the horses’ heart rates increased when they were looking at wolves on the screen, they otherwise kept a poker face. They didn’t bob their heads or swish their tails, and their gaze wasn’t fixed in a way that would indicate their brain was processing a threat, results showed.

“Rather than just spooking, horses show remarkable cognitive restraint when evaluating a potential threat,” said lead author Zeynep Benderlioglu, a senior lecturer in evolution, ecology and organismal biology at The Ohio State University. “And not all fear or stress will result in overt behavior. They’re not in fight-or-flight mode, but they’re assessing, and they’re doing it in a remarkably fast way. But their hearts are racing at the same time.”

The findings are relevant to horse and human welfare, Benderlioglu said: Riders and handlers may not be able to tell when a horse is agitated.

“This visual recognition means horses may be experiencing an internal state of agitation while remaining physically still,” she said. “Understanding this disconnect is vital for ensuring both rider safety and the welfare of a horse that is processing a threat, especially if that threat is a canid – any dog.”

The research was published today (July 15, 2026) in the journal PLOS One.

Eighteen horses of both sexes and a range of ages were involved in the study. The animals watched a brief silent video in a standard stall while wearing an equine heart monitor and being recorded on a video camera.

Benderlioglu said that to the best of her knowledge, this research represents a novel approach in testing equine predator recognition by isolating visual cues from other sensory inputs like scent or sound.

The video showed three scenes for 20 seconds each: A control stimulus featuring free-ranging wombats grazing, followed by videos of groups of wolves either interacting aggressively or grooming. Half of the horses saw wolves fighting first and then grooming, and the wolf sequence was reversed for the other half.

Separately, researchers collected data from handlers on the animals’ age, sex, social status in the herd, social dependency and temperament – such as social anxiety or fearfulness.

Heart rates remained at baseline when the horses were viewing the wombats, but significantly increased when they were viewing the wolves, no matter which behavior the predators were engaged in, fighting or grooming – a surprising finding.

“I expected the horses would differentiate the fighting videos from the grooming videos, but they didn’t. They had high alertness and a higher heart rate, compared to baseline and wombats, when looking at both grooming and fighting wolves,” said Benderlioglu, also director of the Undergraduate Research Lab in Ohio State’s Department of Evolution, Ecology and Organismal Biology.

Heart rate increases were more pronounced in male horses and in horses with higher social status.

“Males had the same baseline heart rates compared to females, but males reacted more. They had heightened heart rate responses, higher arousal,” she said. “High-status horses showed heightened heart rate responses during predator stimuli, likely because they play an important role in collective decision-making and leading the herd. High-status horses are often followed by others because the herd places increased trust in them to make collective decisions, especially when it comes to safety.”

The gaze-related findings were of particular interest to the team, and could help explain why the horses didn’t show their hypervigilance cards by displaying any physical behavior.

Previous research has suggested that horses and most vertebrates use left-eye gazing to assess a threat because that function is based in the right side of the brain. A right-eye gaze suggests animals are engaged in a cognitive assessment, more of a left-brain task.

In this study, the horses showed no gaze preference while viewing the wolves, and when they were viewing wombats, they watched intently with binocular vision – both eyes, straight on.

“They were investigating, it seems, the point being they’re immediately, within 20 seconds, they’re assessing,” Benderlioglu said. “You cannot be in the head of the horse, but the gaze and their hearts, those are giving something away. It’s like the horse thinks, ‘Here is a wolf.’ Wait a minute, the horse thinks again, ‘What is that fluffy thing?’”

Horses evolved as prey animals, which is why this level of discernment was unexpected, she said.

“People don’t necessarily attribute a high level of cognition to prey animals,” she said. “But the horses are engaging in a really unexpectedly high level of cognitive processing. They are on high alert, and then the threat didn’t materialize, so behavioral manifestations are not occurring because they’re cognitively assessing.

“So if they’re not showing any overt stress signs, you don’t realize they might be in a high-alert state.”

The study took place at the Ohio State Equine Center operated by the Department of Animal Sciences.

Co-authors, all from Ohio State, were Rachel Hofacker, Natalie Sebunia (now at Cornell University) and Jessica Pihlblad (now at the University of Arizona).

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Contact: Zeynep Benderlioglu, Benderlioglu.1@osu.edu

Written by Emily Caldwell, Caldwell.151@osu.edu; 614-292-8152

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Journal

PLOS One

DOI

10.1371/journal.pone.0349298 

Article Title

Recognition of unfamiliar predators in domestic horses through only visual predator cues

Article Publication Date

15-Jul-2026

A view of the heart-rate monitor applied to each horse during the experiment.

Credit

Zeynep Benderlioglu

Parasitic Tapeworm — A Risk To Domestic Dogs And Humans — Found In Washington State  Coyotes

A new University of Washington study detected a parasitic tapeworm that can infect domestic dogs and humans in the intestines of one-third of coyotes surveyed in Washington. This coyote (not part of the study) was spotted in Seattle’s Discovery Park last fall. CREDIT: Samantha Kreling/University of Washington

 April 7, 2026  

By Eurasia Review

New evidence suggests that a disease-causing tapeworm that has been spreading across the United States and Canada has arrived in the Pacific Northwest. The tapeworm, called Echinococcus multilocularis, lives as a parasite in coyotes, foxes and other canid species and can cause severe disease if passed to domestic dogs or humans

E. multilocularis has long been recognized as a public health threat in parts of the Northern hemisphere, including Europe and Asia, but was considered extremely rare in North America until approximately 15 years ago, when cases in humans and dogs began cropping up in Canada and the midwestern U.S., indicating that the parasite was spreading.

This study, led by University of Washington researchers, is the first to detect E. multilocularis in a wild host on the west coast of the contiguous U.S. Researchers surveyed 100 coyotes in the Puget Sound region, and found E. multilocularis in 37 of them. The results were published in PLOS Neglected Tropical Diseases.

“This parasite is concerning because it has been spreading across North America. There have been numerous cases of dogs getting sick, and a handful of people have also picked up the tapeworm,” said lead author Yasmine Hentati, who recently graduated from the UW with a doctorate in environmental and forest science. “The fact that we found it here in one-third of our coyotes was surprising, because it wasn’t found anywhere in the Pacific Northwest until earlier this year.”

When E. multilocularis infects an animal or person, it causes cancer-like cysts to form in the liver and sometimes other organs. If untreated, infection can be fatal.

However, not all carriers become sick. E. multilocularis has a complex life cycle that involves multiple hosts. Canids, which host adult parasites, can support thousands of worms in their intestines without becoming sick. The worms shed eggs that are then passed in their feces.

Rodents — another host — become infected by eating food contaminated with coyote feces. Once consumed, the parasite eggs migrate to the liver and form cysts, ultimately weakening or killing the rodents. The parasite’s life cycle begins again when coyotes prey upon infected rodents.

Humans and domestic dogs are categorized as accidental hosts. Humans may pick up the parasite by consuming tapeworm eggs — in food that is contaminated with coyote or dog feces, for example — and can develop a disease called alveolar echinococcosis, characterized by slow-growing metastatic cysts. Symptoms may not appear for five to 15 years after exposure, which complicates diagnosis and treatment.

Alveolar echinococcosis is considered the third most important food-borne illness globally, and one of the top 20 neglected tropical diseases by the World Health Organization. Many countries have developed robust protocols for tracking it.

Domestic dogs that are exposed to E. multilocularis may or may not become sick, depending on where the parasite is in its life cycle at exposure. It is more common for dogs to carry the parasite and shed eggs without developing disease, but dogs that are exposed to parasite eggs may develop the same cancer-like cysts as other infected animals.

“To minimize the risk of dogs getting infected with E. multilocularis, owners should not let them prey on rodents or scavenge their carcasses,” said co-author Guilherme Verocai, an associate professor and director of the Parasitology Diagnostic Laboratory at the Texas A&M University College of Veterinary Medicine and Biomedical Sciences.

Owners can also give dogs preventative medication for worms and ticks and ensure routine veterinary care, which should include diagnostic tests for parasites, Verocai said.

Although the researchers found E. multilocularis in more than one-third of local coyotes tested, there is little evidence of the infection spreading to other hosts. One study reported seven cases of the parasite in dogs in Washington, Oregon and Idaho since 2023, five of which were in Washington. Few human cases have been reported in the U.S., and none on the West Coast.

“The reason that it’s so high in coyotes is because they are regularly eating raw rodents, and that is the primary way for them to get infected. Most domestic dogs are not eating the raw livers of wild rodents,” Hentati said.

Before the uptick in the 2010s, there were several reports of E. multilocularis on remote islands in northwestern Alaska. Those cases were caused by a parasite with different origins than the current outbreak. Genetic analysis pins the earlier cases to a tundra variant while these recent cases are driven by a more infectious variant with European origins. The coyotes in this study carried the newer variant, now thought to be the predominant variant in the U.S. and Canada.

Neither Canada nor the U.S. require dogs to undergo deworming upon arrival, which may explain the spread. Previous studies also proposed that E. multilocularis could have come over in red foxes imported for hunting 100 years ago, but no one knows for sure.

“The main takeaway is that Echinococcus multilocularis is here, it’s pretty prevalent in the local coyote population and people should be aware of potential risks,” Hentati said.

 

Mosquitoes’ thirst for human blood has increased as biodiversity loss worsens

Scientists found that some mosquitoes really are targeting humans more than other food sources, but it could be a matter of convenience as biodiversity dwindles and other food sources are displaced

Peer-Reviewed Publication

Frontiers

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Reserva Ecológica do Guapiaçu (REGUA), Cachoeiras de Macacu, Rio de Janeiro.

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Credit: Cecilia Ferreira de Mello.

Stretching along the Brazilian coastline, the Atlantic Forest is home to hundreds of species of birds, amphibians, reptiles, mammals, and fishes. However, due to human expansion, only about a third of the forest’s original area remains intact. As human presence drives animals from their habitats, mosquitoes that once fed on a wide variety of hosts might be finding new, human targets to quench their thirst for blood, a new Frontiers in Ecology and Evolution study found.

“Here we show that the mosquito species we captured in remnants of the Atlantic Forest have a clear preference for feeding on humans,” said senior author Dr Jeronimo Alencar, a biologist at the Oswaldo Cruz Institute in Rio de Janeiro.

“This is crucial because, in a environment like the Atlantic Forest with a great diversity of potential vertebrate hosts, a preference for humans significantly enhances the risk of pathogen transmission,” added co-author Dr Sergio Machado, a researcher who studies microbiology and immunology at the Federal University of Rio de Janeiro.

Humans preferred

For their study, the researchers used light traps to capture mosquitoes at the Sítio Recanto Preservar and the Guapiacu River Ecological Reserve, two natural reserves in the state of Rio de Janeiro. In the lab, engorged female mosquitoes were separated for analysis. The researchers extracted DNA from the blood and used DNA sequencing to analyze a specific gene that functions as a unique ‘barcode’ for each vertebrate species. By comparing barcodes found in the blood to a database, the researchers could determine which animal the mosquito had fed on.

Out of a total of 1,714 captured mosquitoes belonging to 52 species, 145 females were engorged with blood. Blood meals consumed by 24 of those mosquitoes could be identified and were sourced from 18 humans, one amphibian, six birds, one canid, and one mouse. Some blood meals were made up of multiple sources: the meal of a mosquito identified as Cq. Venezuelensis was made up of amphibian and human blood. Mosquitoes belonging to the species Cq. Fasciolata had fed on both a rodent and a bird as well as a bird and a human, respectively. 

The researchers hypothesized that multiple factors could play a role in their preference for our blood. “Mosquito behavior is complex,” Alencar said. “Although some mosquito species may have innate preferences, host availability and proximity are extremely influential factors.”

Disease spreads

As the Atlantic Forest dwindles due to deforestation and humans keep pushing into previously forested areas, many plants and animals disappear. As a result, mosquitoes change their habits and habitats and get closer to humans. “With fewer natural options available, mosquitoes are forced to seek new, alternative blood sources. They end up feeding more on humans out of convenience, as we are the most prevalent host in these areas,” explained Machado.

Bites are more than itchy. In the study regions, mosquitoes transmit a variety of viruses – such as Yellow Fever, dengue, Zika, Mayaro, Sabiá, and Chikungunya – which cause diseases that seriously threaten human health and can have long-term adverse consequences. Investigating mosquito foraging behavior is fundamental for understanding the ecological and epidemiological dynamics of the pathogens they transmit, the researchers said.

The relatively low rate of engorged mosquitoes – just under 7% – as well as the low percentage of cases in which blood meals could be identified – around 38% – highlight the need for more data rich studies. Those studies should also use methods more suited to identifying mixed blood meals to determine all food sources.

Already, the study can aid in the development of more effective policies and strategies to control disease-carrying mosquitoes and help predict and prevent future disease outbreaks. “Knowing that mosquitoes in an area have a strong preference for humans serves as an alert for transmission risk,” Machado pointed out.

“This allows for targeted surveillance and prevention actions,” concluded Alencar. “In the long term, this may lead to control strategies that consider ecosystem balance.”

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Journal

Frontiers in Ecology and Evolution

Sítio Recanto Preservar, Silva Jardim, Rio de Janeiro.

Credit

Cecilia Ferreira de Mello.

DOI

10.3389/fevo.2025.1721533 

Method of Research

Experimental study

Subject of Research

Animals

Article Title

Aspects of the blood meal of mosquitoes (Diptera: Culicidae) during the crepuscular period in Atlantic Forest remnants of the state of Rio de Janeiro, Brazil

Article Publication Date

15-Jan-2026

 

Humans rank between meerkats and beavers in monogamy ‘league table’

University of Cambridge

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Humans are far closer to meerkats and beavers for levels of exclusive mating than we are to most of our primate cousins, according to a new University of Cambridge study that includes a table ranking monogamy rates in various species of mammal.

Previous evolutionary research has used fossil records and anthropological fieldwork to infer human sexual selection. While in other species, researchers have conducted long-term observations of animal societies and used paternity tests to study mating systems.

Now, a new approach by Dr Mark Dyble from Cambridge’s Department of Archaeology analyses the proportions of full versus half-siblings in a host of species, as well as several human populations throughout history, as a measure for monogamy.

Species and societies with higher levels of monogamy are likely to produce more siblings that share both parents, says Dyble, while those with more polygamous or promiscuous mating patterns are likely to see more half-siblings.

He devised a computational model that maps sibling data collected from recent genetic studies onto known reproductive strategies to calculate an estimated monogamy rating.

While still a rough guide, Dyble argues this is a more direct and concrete way to gauge patterns of monogamy than many previous methods when looking at a spectrum of species, and human societies over thousands of years.    

“There is a premier league of monogamy, in which humans sit comfortably, while the vast majority of other mammals take a far more promiscuous approach to mating,” said Dyble, an evolutionary anthropologist at the University of Cambridge.

“The finding that human rates of full siblings overlap with the range seen in socially monogamous mammals lends further weight to the view that monogamy is the dominant mating pattern for our species.”

The question of human monogamy has been debated for centuries. It has long been hypothesised that monogamy is a cornerstone of the social cooperation that allowed humans to dominate the planet.

However, anthropologists find a wide range of mating norms among humans. For example, previous research shows that 85% of pre-industrial societies permitted polygynous marriage – where a man is married to several women at the same time.

To calculate human monogamy rates, Dyble used genetic data from archaeological sites, including Bronze Age burial grounds in Europe and Neolithic sites in Anatolia, and ethnographic data from 94 human societies around the world: from Tanzanian hunter-gatherers the Hadza, to the rice-farming Toraja of Indonesia.

“There is a huge amount of cross-cultural diversity in human mating and marriage practices, but even the extremes of the spectrum still sit above what we see in most non-monogamous species,” said Dyble.

The study, published in Proceedings of the Royal Society: Biological Sciences, has humans at an overall 66% rate for full siblings, placing us seventh of eleven species in the study considered socially monogamous and preferring long-term pair bonds.

Meerkats come in at a 60% full sibling rate while beavers just beat humans for monogamy with a 73% rate. As with humans, this suggests a significant trend towards monogamy for these species, but with a solid amount of flexibility.

The white-handed gibbon comes closest to humans in the study, with a monogamy rate of 63.5%. It’s the only other top-ranked “monotocous” species, meaning it usually has one offspring per pregnancy, unlike the litters had by other monogamous mammals.

The only other non-human primate in the top division is the moustached tamarin: a small Amazonian monkey that typically produces twins or triplets, and has a full sibling rate of almost 78%.   

All other primates in the study are known to have either polygynous or polygynandrous (where both males and females have multiple partners) mating systems, and rank way down the monogamy table.  

Mountain gorillas manage a 6% full sibling rate, while chimpanzees come in at just 4% – on a par with dolphins. Various macaque species, from Japanese (2.3%) to Rhesus (1%), sit almost at the bottom of the table.

“Based on the mating patterns of our closest living relatives, such as chimpanzees and gorillas, human monogamy probably evolved from non-monogamous group living, a transition that is highly unusual among mammals,” said Dyble.  

Among the few with a similar evolutionary shift are species of wolf and fox, which have a degree of social monogamy and cooperative care, whereas the ancestral canid was likely to have been group-living and polygynous.

The Grey Wolf and Red Fox sneak into the upper league with full sibling rates of almost half (46% and 45% respectively), while African species have much higher rates: the Ethiopian wolf comes in at 76.5%, and the African Wild dog is ranked second for monogamy with a rating of 85%.

Top of the table is the California deermouse that stays paired for life once mated, with a 100% rating. Ranked bottom is Scotland’s Soay sheep, with 0.6% full siblings, as each ewe mates with several rams.

“Almost all other monogamous mammals either live in tight family units of just a breeding pair and their offspring, or in groups where only one female breeds,” said Dyble. “Whereas humans live in strong social groups in which multiple females have children.”

The only other mammal believed to live in a stable, mixed-sex, multi-adult group with several exclusive pair bonds is a large rabbit-like rodent called the Patagonian mara, which inhabits warrens containing a number of long-term couples. 

Dyble added: “This study measures reproductive monogamy rather than sexual behaviour. In most mammals, mating and reproduction are tightly linked. In humans, birth control methods and cultural practices break that link.”

“Humans have a range of partnerships that create conditions for a mix of full and half-siblings with strong parental investment, from serial monogamy to stable polygamy.”

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Journal

Proceedings of the Royal Society B Biological Sciences

DOI

10.1098/rspb.2025.2163 

Method of Research

Data/statistical analysis

Article Title

Human monogamy in mammalian context

Article Publication Date

10-Dec-2025