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

 

Ancient wolves on remote Baltic Sea island reveal link to prehistoric humans

Scientists have found wolf remains, thousands of years old, on a small, isolated island in the Baltic Sea – a place where the animals could only have been brought by humans. The study, published in Proceedings of the National Academy of Sciences by rese

Stockholm University

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Detail of one of the upper arm bones from one of the wolves included in the study. Photo: Jan Storå/Stockholm University

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Credit: Jan Storå/Stockholm University

Scientists have found wolf remains, thousands of years old, on a small, isolated island in the Baltic Sea – a place where the animals could only have been brought by humans. The study, published in Proceedings of the National Academy of Sciences by researchers at the Francis Crick Institute, Stockholm University, the University of Aberdeen and the University of East Anglia, suggest that grey wolves may have been managed or controlled by prehistoric societies.

The discovery of the 3,000–5,000-year-old wolf remains was made in the Stora Förvar cave on the Swedish island of Stora Karlsö, a site known for its intensive use by seal hunters and fishers during the Neolithic and Bronze Ages. The island, which covers only 2.5 square kilometres, has no native land mammals, meaning that any such animals must have been brought there by people.

Genomic analysis of two canid remains confirmed they were wolves, not dogs, with no evidence of dog ancestry. However, they exhibited several traits typically associated with life alongside humans. Isotope analysis of their bones revealed a diet rich in marine protein, such as seals and fish, aligning with the diet of the humans on the island and suggesting they were provisioned. Furthermore, the wolves were smaller than typical mainland wolves, and one individual showed signs of low genetic diversity, a common result of isolation or controlled breeding.

“The discovery of these wolves on a remote island is completely unexpected,” said Dr. Linus Girdland-Flink of the University of Aberdeen, a lead author of the study. “Not only did they have ancestry indistinguishable from other Eurasian wolves, but they seemed to be living alongside humans, eating their food, and in a place they could have only have reached by boat. This paints a complex picture of the relationship between humans and wolves in the past.”

The finding challenges the conventional understanding of wolf-human dynamics and the process of dog domestication. While it remains unclear if these wolves were tamed, kept in captivity, or managed in some other way, their presence in a human-occupied, isolated environment points to a deliberate and sustained interaction.

“It was a complete surprise to see that it was a wolf and not a dog,” said Pontus Skoglund of the Ancient Genomics Laboratory at the Francis Crick Institute and senior author. “This is a provocative case that raises the possibility that in certain environments, humans were able to keep wolves in their settlements, and found value in doing so.”

Anders Bergström of the University of East Anglia and co-lead author, commented: “The genetic data is fascinating. We found that the wolf with the most complete genome had low genetic diversity, lower than any other ancient wolf we’ve seen. This is similar to what you see in isolated or bottlenecked populations, or in domesticated organisms. While we can’t rule out that these wolves had low genetic diversity for natural reasons, it suggests that humans were interacting with and managing wolves in ways we hadn’t previously considered.”

One of the wolf specimens, dated to the Bronze Age, also showed advanced pathology in a limb bone, which would have limited its mobility. This suggests it may have been cared for or was able to survive in an environment where it did not need to hunt large prey.

The combination of osteology and genetic analyses have provided unique information not available separately. “The combination of data has revealed new and very unexpected perspectives on Stone Age and Bronze Age human-animal interactions in general and specifically concerning wolves and also dogs,” says Jan Storå, Professor of Osteoarchaeology at Stockholm University.  

The study suggests that human-wolf interactions in prehistory were more diverse than previously thought, extending beyond simple hunting or avoidance to include complex relations and interactions that, in this case, mirrors new aspects of domestication without leading to the canines we know as dogs today.

  

View from the cave Stora Förvar on the island of Stora Karlsö in Sweden. 

Photo: Jan Storå/Stockholm University

  

The entrance to the Stora Förvar cave on the island Stora Karlsö. The cave was explored between 1888 and 1893. The limestone-rich bedrock has contributed to the skeletal material found there being very well preserved. 

Photo: Jan Storå/Stockholm University

View towards the Stora Förvar cave on the island of Stora Karlsö. 

Photo: Jan Apel/Stockholm University

Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2421759122 

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Gray wolves in an anthropogenic context on a small island in prehistoric Scandinavia

Article Publication Date

24-Nov-2025