By Claire Cameron Scientists have long known that women’s brains undergo substantial remodeling during puberty and pregnancy. These moments of hormonal upheaval are linked to a rewiring of neural networks and reductions in the volume of the brain’s outer, wrinkly layer—called cortical gray matter—which plays a role in memory, reasoning and movement. But far less is known about what happens to the brain in another major hormonal shift: menopause. Now a new study published in Nature Communications sheds some light on how the brain changes in menopause. Unlike during puberty and pregnancy, the menopausal transition—the moment the body is going through menopause—doesn’t appear linked to an overall decrease in cortical gray matter volume. The finding suggests the female brain responds in different ways to points of hormonal flux throughout the lifespan. “No one had looked at the changes in the whole brain matter in this menopause transition before,” said Sophie van ’t Hof, a Ph.D. student at the Amsterdam University Medical Center in the Netherlands, at a press conference discussing the results. Van ’t Hof is first author of the new study. Gray matter declines as people age, no matter their biological sex. But by comparing the brains of individuals who were transitioning through menopause with those of women who were premenopausal and postmenopausal, the researchers found little change in gray matter volume during menopause. The results suggest that sex hormone levels affect the brain in different ways at different times during the lifespan. “This is really fundamental research, and it’s really understanding the basic brain mechanisms of the female brain. It’s long been overlooked,” van ’t Hof said. © 2026 SCIENTIFIC AMERICAN INC.

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 30399 - Posted: 09.09.2026

Will Stone A few times, Dr. Jamin Brahmbhatt suspected he might have low testosterone. But when he checked his numbers, he discovered they were within a normal range. "Turns out it was more so my sleep and stress and everything else," says Brahmbhatt, a urologist at Orlando Health in Florida. Brahmbhatt treats men with low testosterone every day — meaning he's on the front lines of the current cultural fixation with testosterone. Social media is overflowing with testosterone content, from fears of "low T" to "T-maxxing" tutorials. Influential voices, including the podcaster Joe Rogan and Health Secretary Robert F. Kennedy Jr., are openly discussing their own use of testosterone therapy. And there's a huge industry of online clinics that make it easy for anyone to get a prescription. Brahmbhatt welcomes the increased attention to men's health — and hormone replacement therapy specifically — which he says has been "ignored" for too long. But he also sees men who've spent hours in online forums like Reddit, convinced they need testosterone even before they've spoken to a doctor or had their levels tested. "Not every guy needs to be on it," Brahmbhatt says. "Testosterone has gotten a bad rap because … you can walk into these clinics, go online, and get a prescription, they don't do all the testing, they don't do the follow up. That is the unsafe territory." © 2026 npr

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 30367 - Posted: 08.12.2026

By Clarissa Brincat To avoid ending up with a less committed mate, some female birds listen for red flags in their suitor’s song. Male pied flycatchers change their song after mating, and females use these song features to tell if a male is already paired, researchers report July 1 in Ethology. The results are consistent with earlier research showing that most female pied flycatchers prefer to settle with an unmated male. “The female doesn’t really care about the song,” says behavioral ecologist Stephen Nowicki of Duke University, who was not involved in the work. “She cares because the song is a reliable indicator of some quality of the male,” including whether it already has a mate. Once its first mate lays eggs, a male pied flycatcher (Ficedula hypoleuca) will often set up another nest several hundred meters away and court passing females. The stakes are high for the females, as a male splitting its time between two nests provides less help raising chicks. Ethologist Helene Lampe and her colleagues recorded 17 wild males twice — once while a male was a bachelor, and again after it had mated and moved to a second territory to woo another female. Using bioacoustics software, the team found that two things changed. The songs got shorter — from about two seconds to about 1.7 — and the male repeated itself less. “Usually, a male will cycle through his song syllables in an orderly manner — one or two syllables are usually repeated from one song to the next,” says Lampe, of the University of Oslo. “But when they become polyterritorial, they do it much less often.” © Society for Science & the Public 2000–2026.

Keyword: Animal Communication; Sexual Behavior
Link ID: 30356 - Posted: 08.05.2026

By Jackie Flynn Mogensen Lindsay Clancy, a 35-year-old former nurse, is on trial in Massachusetts for the murder of her three young children in 2023. The details of the case are disturbing—according to court records, Clancy strangled her children, aged five years, three years and eight months, to death before she attempted to take her own life. Clancy has pled not guilty to the murder charges on the basis that she suffered from a mental health disorder called postpartum psychosis. During this episode, Clancy’s lawyers have said, she was convinced by voices in her head to kill her children and herself. The prosecution has argued the killings were premeditated. The ongoing, high-profile trial has thrust the topic of maternal mental health—and postpartum psychosis in particular—into the national spotlight. But behind the headlines, maternal mental health experts say the disorder is nuanced, understudied and, importantly, treatable. Postpartum psychosis is a rare and severe mental disorder that occurs in people who have given birth. It occurs after about one to two of every 1,000 live births, explains Khatiya Moon, an assistant professor of psychiatry at the Zucker School of Medicine at Hofstra/Northwell. It’s different from postpartum depression—the onset of depression following childbirth—which is more common and can affect around one in five to 10 people who have given birth. The symptoms of postpartum psychosis are “variable,” Moon says, but may include delusions, paranoia, purposeless or repetitive behavior, as well as hallucinations—hearing voices, seeing things or even feeling sensations on the skin that aren’t there. © 2026 SCIENTIFIC AMERICAN INC.

Keyword: Depression; Hormones & Behavior
Link ID: 30351 - Posted: 08.01.2026

Maria Godoy School used to be pretty easy for Kate Jarvis when she was a little girl, back in the 1980s. She was a straight-A student, creative, and so organized that she'd even prep her toothbrush with toothpaste each night before school. She says her mother used to call her "bright-eyed and bushy tailed." Then puberty hit, and everything started to fall apart. She found it harder to focus in school, and her grades slipped. "It really hit my self-esteem badly. I felt pretty awful about myself," she says. In high school, she was diagnosed with anxiety and depression. She struggled to fit in. She says it stung when teachers would write comments like, "Kate has so much potential, if only she'd apply herself." "So it felt like character flaws rather than what it really was, which was undiagnosed ADHD," says Jarvis, who didn't get a diagnosis until her late 30s. Kate Jarvis says that her diagnosis of ADHD in her 30s felt revolutionary. “Something I had been wrestling with for 25 years had a name, causes, symptoms and effects.” However, the diagnosis came with challenges as well. “Just because you know what something is, doesn’t mean you can immediately fix it. And that’s what I felt, like I needed to fix myself.” Kate Jarvis says that her diagnosis of ADHD in her 30s felt revolutionary. "Something I had been wrestling with for 25 years had a name, causes, symptoms and effects." However, the diagnosis came with challenges as well. "Just because you know what something is, doesn't mean you can immediately fix it. And that's what I felt - like I needed to fix myself." Jarvis family © 2026 npr

Keyword: ADHD; Sexual Behavior
Link ID: 30348 - Posted: 07.29.2026

By Jake Currie Humans are social animals, so seeing a fellow human face triggers a cascade of activity in our brains. Information about the age, gender, familiarity, emotional state, and more get processed within milliseconds. Now, new research published in the journal Developmental Cognitive Neuroscience suggests how our brains respond to faces in our youth could impact our social lives later on. ​​“Faces contain a lot of social information, and perceptually or cognitively humans process that information really, really quickly,” study author Myles N. Arrington said in a statement. “That makes it great for neuroscience, because as soon as you show a face to a person it doesn’t take long for their brain to respond.” Arrington and his fellow neuroscientists at the University of California, Davis studied brain activity of almost 6,000 children between the ages of 8 and 11 from the Adolescent Brain Cognitive Development Study. The kids were shown pictures of faces displaying positive, negative, and neutral emotions (which contain loads of social information) and places (which contain none) while their brain activity was monitored on an fMRI machine. Combining the fMRI results with two-year follow-ups, they found that increased activity in the amygdala—the brain’s fight-or-flight center—in response to faces was correlated with changes in their social lives. Interestingly, boys and girls with heightened amygdala activity had much different results later in life. Girls with more active amygdalas tended to have more involvement with peers two years down the road, while boys showed less involvement. According to the researchers, this could be due to differences in how the two genders are socialized. For example, “boys may be socialized to withhold intimacy and distance themselves from their peers,” the team wrote. It’s possible that this socialization can impact how their developing young minds process the social information contained in faces. © Copyright 2026

Keyword: Emotions; Sexual Behavior
Link ID: 30324 - Posted: 07.15.2026

By Natalia Mesa If a longtime friend suddenly becomes a foe, like Brutus to Caesar or Iago to Othello, the brain must update the person’s feelings about the betrayer without altering memories of who that companion is. The hippocampus may sometimes store both pieces of information, but when it comes to updating feelings, it keeps identity and emotional valence separate, according to a mouse study published today in Science. “We found the neural mechanisms that underlie emotion toward others,” says study investigator Teruhiro Okuyama, professor at the Institute of Quantitative Biosciences at the University of Tokyo: Memory-storing neurons in the hippocampus remain relatively stable, but the strength of their connections to the basolateral amygdala neurons shift, the study shows. Okuyama and his colleagues used chemogenetics to induce aggression in previously docile mice and optogenetics to trace how hippocampal circuits change in the animal’s cagemate. They found that they could both “write and erase social memories” by targeting specific neuron populations. “It’s truly unbelievable how much they did in this paper,” says Robert Malenka, professor of psychiatry and behavioral sciences at Stanford University, who was not involved in the work. “They did a beautiful job of taking three brain areas and defining the connectivity and the cell-type-specific connections that are responsible for the phenomenon they’re studying.” Neurons in the hippocampus store social memories and segregate positive and negative ones, previous work shows. But most past work has studied how negative run-ins with unfamiliar animals affect behavior. © 2026 Simons Foundation

Keyword: Aggression; Sexual Behavior
Link ID: 30318 - Posted: 07.11.2026

By Amber Dance Motherhood creates a broad swath of long-term gene-expression changes in the brains of mice, according to a new study. This is accomplished by dopamine attaching to the histones of neuronal DNA and regulating gene expression, particularly in the hippocampus. The findings suggest that “pregnancy fundamentally changes the body and brain,” says study investigator Jennifer O’Chan, instructor in neuroscience at the Icahn School of Medicine at Mount Sinai. “And these are long-lasting effects.” Similar patterns of gene regulation appeared in postmortem samples from five women of varying ages who had all given birth in their past, O’Chan and her colleagues found. The work thus adds to a small but growing body of research on neurological changes linked to pregnancy, birth and parenting. “The maternal brain is woefully understudied, and so the molecular profiling that they do … it’s really an enormous resource,” says Catherine Peña, assistant professor of neuroscience at Princeton University, who was not involved with the paper. Of 11 brain regions linked to maternal behaviors in mice that the group studied, the dorsal hippocampus and associated subiculum—together called the dorsal hippocampal formation—exhibited the greatest differences in gene expression between virgin mice and those that experienced the full spectrum of motherhood, from mating to weaning. This region doesn’t usually top the list of brain areas linked with maternity, says Robert Froemke, professor of neuroscience at New York University Langone Health, who wasn’t involved in the study. But hippocampal functions such as temporal sequencing and synthesizing different memory streams could certainly apply to pup-rearing, he says. “It’s not a total surprise, but it’s fair to say this paper makes me consider its importance more strongly.” © 2026 Simons Foundation

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 30277 - Posted: 06.13.2026

By Jake Buehler A series of sharp cracks splits the nighttime air in a forest in the Andean foothills. But this isn’t the sound of boots snapping twigs underfoot. It’s a bird. Male scissor-tailed nightjars (Hydropsalis torquata) create these abrupt sounds by hitting the bones in their wings together in a forceful snap, researchers report in the May Journal of Avian Biology. Nightjars are largely nocturnal, insect-eating birds related to hummingbirds and swifts. H. torquata males are unusual for their exceptionally long, paired tail feathers. These males were already known to make explosive cracking noises at night as a mating signal to any nearby females. But little was understood about how they were doing it, says Juan Ignacio Areta, an evolutionary naturalist at Instituto de Bio y Geociencias del Noroeste Argentino in Salta, Argentina. “Many nocturnal animals are well known for being extremely silent, such as the ‘silent’ flight of owls,” Areta says. “We wanted to learn how it was possible for a nocturnal animal to make these loud sounds.” In late 2022, Areta and Christopher Clark — a behavioral ecologist at the University of California, Riverside — covertly filmed the male birds at night along a forest road near Salta. They used high-speed infrared cameras and then compared the footage to the sounds they were recording. Often, the nightjars would hop off the ground and swing their wings together behind their backs, creating a loud clack upon impact. Sometimes the males did this while flying or while mating with a female. The birds weren’t just hitting their feathers together. It was clear to the researchers that the snaps came from the wrist bones colliding just below the last bend in the wing. Areta and Clark think the bones vibrating from the forceful collision create the abrupt snapping sound. © Society for Science & the Public 2000–2026.

Keyword: Animal Communication; Sexual Behavior
Link ID: 30273 - Posted: 06.10.2026

By Hannah Thomasy Prairie voles have a reputation as one of the most social rodents, but when Aubrey Kelly tried to use them to study the neurobiology of group dynamics, she discovered limits to their sociability. “Prairie voles are indeed super social with their pair-bond partner and with their offspring,” says Kelly, associate professor of psychology at Emory University. “But if an adult prairie vole encounters a stranger, they’re going to fight—oftentimes to the death.” She shifted her focus to paternal care in the voles but stayed on the lookout for a truly social rodent that lived in rich, complex communities. As a graduate student, she had studied the neural circuitry that contributes to such societies in zebra finches, and she hoped to make similar inroads in mammalian brains. “I got really into the idea of animal societies and how individuals can just get along in big groups, which is something that we do ourselves,” Kelly says. About four years later, a colleague introduced her to spiny mice. Despite their name, these animals are more closely related to gerbils than to laboratory mice. They live in large, flexible, mixed-sex groups and rarely brawl, the colleague told her. Kelly was intrigued—perhaps these groups were the miniature mammal societies she had been searching for. Her subsequent work has demonstrated that, indeed, these critters not only tolerate groups but actually prefer them: When given a choice between associating with two peers or eight peers, they spend the majority of their time with the larger group. Now Kelly is digging into the neural mechanisms underlying this communal lifestyle. Kelly spoke with The Transmitter about spiny mouse “friendships,” custom CRISPR tools and the neurobiology of coexistence. © 2026 Simons Foundation

Keyword: Aggression; Hormones & Behavior
Link ID: 30266 - Posted: 06.03.2026

By Helena Kudiabor Microglia, known for scavenging debris and attacking pathogens, may also help regulate the hypothalamic-pituitary-gonadal axis, a new study shows. The findings, published in March in Science, suggest that microglia interact with and influence the function of hypothalamic neurons that release gonadotropin-releasing hormone (GnRH), which stimulates the pituitary to produce the hormones that spark ovulation and spermatogenesis. “One of the biggest surprises was the role of microglia in controlling the GnRH neurons, because this is a link that hadn’t been seen before,” says study investigator Alejandro Collado-Solé, a postdoctoral researcher in Eva González-Suárez’s group at the Spanish National Cancer Research Center. Microglia express a protein called RANK that is crucial to their effects on the hypothalamic-pituitary-gonadal axis. Knocking out RANK in mice reduces microglia’s interactions with GnRH neurons, lowers sex hormone levels and renders some of the animals infertile, the new study found. “The fact that these specific interactions in such a small region of the brain can have such profound effects on fertility—a very fundamental aspect of the survival of a species—was quite unexpected,” says Annie Ciernia, assistant professor of biochemistry and molecular biology at the University of British Columbia, who was not involved in the research. Microglia have been widely studied for their role in brain development, but the new study is the first to explore how these cells support the reproductive system. © 2026 Simons Foundation

Keyword: Development of the Brain; Glia
Link ID: 30239 - Posted: 05.09.2026

By Lauren Schenkman More than 3,000 genes are differently expressed in the cerebral cortex of people with XX versus XY sex chromosomes, according to a single-cell transcriptomics study published last month in Science. The differences could help explain why certain neurodegenerative and neurodevelopmental conditions affect one group more than the other, or vice versa. The results present “a pretty dramatic shift in how we’re thinking about sex differences,” says Tomasz Nowakowski, associate professor of neurological surgery, anatomy and psychiatry, and of behavioral sciences, at the University of California, San Francisco. He was not involved in the new work but uncovered gene expression differences in prenatal developing brains last year. Previous research traced sex differences to subcortical structures, where sex hormone receptors are expressed, but “the cortex is not the part of the brain that you typically think of when you think about sex differences,” he says. “I think it’s a landmark.” Of the thousands of genes flagged in the new study, 133 showed consistent sex differences across all brain cell types in six cortical regions sampled from postmortem brains, donated by 15 men (who all had XY sex chromosomes) and 15 women (who all had XX sex chromosomes), aged 26 to 78 years. Two of these regions—the fusiform gyrus and the inferior lateral temporo-occipital cortex—have more gray-matter volume in men, previous MRI studies suggest; two others, the caudal insula and intraparietal sulcus, have more gray matter in women; and the final two regions, the angular gyrus and the retrosplenial cortex, show no sex bias in gray-matter volume. Intriguingly, 119 of the 133 genes are autosomal, meaning men and women should have, at least in theory, an equal dose. That makes them “ground zero for molecular sex differences in the brain,” says study investigator Armin Raznahan, chief of the Section on Developmental Neurogenomics at the U.S. National Institute of Mental Health. © 2026 Simons Foundation

Keyword: Sexual Behavior; Genes & Behavior
Link ID: 30235 - Posted: 05.06.2026

Mariana Lenharo Is testosterone the next miracle drug? That seemed to be the consensus of an expert panel convened by the US Food and Drug Administration (FDA) in December. It argued for major changes in policy that would expand access to the hormone for people with a range of conditions. Committee members called testosterone replacement “a cornerstone of preventive health” and “a multibillion-dollar preventive-care opportunity”. Testosterone is already available in the United States for people who have low levels of the hormone owing to a known medical issue, such as testicular damage. But evidence is growing that more men — and women — might benefit from the hormone, which is delivered through injections, patches, subcutaneous implants or gels. (This article uses ‘men’ and ‘women’ to reflect the language used by the panels and studies cited, while recognizing that trans, non-binary and intersex people are also affected by this issue.) The panel’s recommendations intensify a debate that has been brewing about who might benefit from the treatment. Some clinicians say that most men with low testosterone, especially young ones with no medical issue contributing to the problem, don’t need supplemental treatment at all and should be able to raise their testosterone levels by adopting a healthier lifestyle and losing weight. Others argue that men with low testosterone who have symptoms such as low libido, fatigue and irritability could gain from the therapy. More-enthusiastic proponents, including many members of the FDA panel at the December meeting, take a third view: that all cis men should be tested, and those with low testosterone levels should be treated even if they have no symptoms. “You could make a very strong argument that having a normal testosterone level is important for health and prevention of illness,” says Abraham Morgentaler, a urologist at Harvard Medical School in Boston, Massachusetts, who took part in the December panel. © 2026 Springer Nature Limited

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 30233 - Posted: 05.06.2026

Miryam Naddaf By analysing more than a million brain cells, researchers have uncovered widespread differences in patterns of gene activity between male and female brains. The work, which defined sex on the basis of a person’s combination of sex chromosomes, could help to explain why the risk of developing some brain conditions — such as schizophrenia and Alzheimer’s disease — differs between males and females. Although the differences were subtle, the team identified more than 100 genes that showed consistent variation in their expression between males and females across several brain regions. The work was published on 16 April in Science1. “Having these gene-expression signatures provides a molecular handle to understanding the biology of how the brains of men and women might be functioning slightly differently in the context of the different hormonal environments that their bodies produce,” says Jessica Tollkuhn, a neuroscientist and molecular biologist at Cold Spring Harbor Laboratory in New York. She adds that “understanding sex differences in disease susceptibility could lead to better treatments to benefit everyone”. Subtle differences Previous studies2,3 have documented sex differences when it comes to a person’s risk of developing various neurological conditions. For example, schizophrenia, attention deficit hyperactivity disorder (ADHD) and Parkinson’s disease are more common in biological males — who typically have XY sex chromosomes. By contrast, Alzheimer’s disease and mood disorders such as depression and anxiety tend to be more common in females, whose sex chromosomes are usually XX. © 2026 Springer Nature Limited

Keyword: Sexual Behavior; Genes & Behavior
Link ID: 30207 - Posted: 04.18.2026

By Erin Garcia de Jesús My early days of nursing a newborn felt like I’d transformed into a 24-hour diner. A demanding yet adorable customer flagged me down with piercing cries to demand milk around the clock. Unfortunately, I was also on clean-up duty, wiping spit-ups and poopy butts. Breastfeeding is hard work. But after reading science journalist Elizabeth Preston’s book The Creatures’ Guide to Caring, I’m glad I’m not a burying beetle. The critters use mouth and anal secretions to knead small dead animals into slick balls of meat. Parent beetles then bury the smothered carcasses and lay their eggs nearby. Some species even feed their brood regurgitated bits of carcass, helping the young beetles grow to 200 times their original size in just six days. “A newborn human growing at that rate would be the size of a beluga whale in less than a week,” Preston writes. Suddenly my own kid doesn’t seem so heavy. The Creatures’ Guide to Caring was born out of Preston’s growing fascination with the biology of parenting after having her first child. “If so many people have done it before you, and are doing it right now — if so many animals are doing it without books or apps or advice to heed — why is it the hardest thing you’ve ever done?” she writes. Perhaps by finding kinship in the animal world, Preston could learn something about her new role as a parent. Each chapter dissects the benefits and drawbacks of parenting, piecing together how it evolved in humans and other creatures. © Society for Science & the Public 2000–2026

Keyword: Sexual Behavior; Evolution
Link ID: 30191 - Posted: 04.08.2026

By Catherine Offord For most people, Oktoberfest means guzzling liters of beer inside a giant tent. But for one research group in Denmark, it’s a chance to study how our bodies know when we’ve had enough. In a preprint posted on bioRxiv last week, researchers combined a small study of people at Germany’s fall beer festival with mouse experiments, genetic analyses, and blood tests from drunk medical students as well as people with alcohol dependence. Their findings, though preliminary, hint that a hormone commonly associated with morning sickness might also have a role in limiting humans’ alcohol consumption. “I found it fascinating,” says Marlena Fejzo, a women’s health scientist at the University of Southern California who has studied GDF15, the hormone involved. Though the study relies mostly on associations and can’t prove cause and effect, it “lends support” to the idea that GDF15 stops us from overconsuming harmful substances, she adds. GDF15 rises sharply during early pregnancy and is thought to contribute to vomiting and feelings of sickness. Some researchers think it evolved as a protective mechanism: Nausea may help an expectant parent avoid unfamiliar or spoiled food that could harm the fetus. But GDF15 is also present in people who aren’t pregnant and has been linked to appetite suppression. It has even attracted interest from the pharmaceutical industry as a potential antiobesity drug. Matthew Gillum, an endocrinologist at the University of Copenhagen, began to wonder about the hormone’s effect on alcohol intake after collaborating on a study of revelers at the Roskilde music festival. That research measured blood hormone levels in young men who’d spent a week binge drinking and eating junk food and found multiple changes—including a rise in GDF15. © 2026 American Association for the Advancement of Science.

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 30168 - Posted: 03.21.2026

By Viviane Callier The difference between a doting dad and a deadbeat one may come down to a molecular switch in the brain — at least in African striped mice. Boosting activity of a particular gene in part of the brain known for regulating maternal care turned nurturing males into standoffish ones and even, in some cases, into mouse pup killers, researchers report February 18 in Nature. The findings reveal how social context can alter gene activity in the brain and thereby shape male caregiving. Male caregiving is prevalent in fish and amphibians, suggesting that it is a very ancient behavior in vertebrates. Among mammals, however, fewer than 5 percent of species have fathers that stick around to raise their young. Male African striped mice (Rhabdomys pumilio) are one of the exceptions to the rule, though they vary a lot in their nurturing tendencies, making them an ideal species in which to study the factors that influence this behavior. Some look after the young and groom them; others ignore the pups or even attack them. The same male could become aggressive or doting. To understand that behavior, comparative neurobiologist Forrest Rogers and his colleagues observed the mice’s social environment. In laboratory settings, group-housed males tended to be aggressive toward mouse pups when introduced to them. But surprisingly, when these males were moved to be housed alone, they became very paternal. “I thought clearly something must be wrong, because all the work we know of in mice and rats is that if you socially isolate them, they become very anxious and often not the most caring of individuals,” says Rogers, of Princeton University. But the lone African striped male mice didn’t seem anxious at all. © Society for Science & the Public 2000–2026.

Keyword: Sexual Behavior; Aggression
Link ID: 30159 - Posted: 03.14.2026

By Phie Jacobs Talk about an odd couple. At least 100,000 years ago, a female Atlantic molly (Poecilia mexicana) living in the fresh waters near what is now Tampico, Mexico, mated with a male sailfin molly (Poecilia latipinna). The offspring of this cross-species coupling ought to have been sterile, like a mule. But this particular hybrid went on to birth a brood of daughters—all of which were genetic clones of their mother. Scientists have long assumed this reproductive strategy of birthing clones to be an evolutionary dead end among vertebrate animals, with offspring inevitably succumbing to genomic degradation over time. But the Amazon molly (Poecilia formosa), named for the fierce female warriors of Greek mythology, has kept on defying the odds. According to research published today in Nature, it all comes down to a quirk of genetics that helps reverse harmful mutations. “This is a very cool story,” says University of Oklahoma biologist Ingo Schlupp, who provided the study authors with samples but otherwise wasn’t involved in the new work. Researchers who study asexual animals, he explains, have been “scratching our heads” trying to figure out how some species manage to avoid what evolutionary theory predicts to be certain doom. Although asexual reproduction is common in bacteria and plants, it only rarely occurs in vertebrate animals. Often, these “virgin births” involve a process called parthenogenesis, in which an embryo develops from an unfertilized egg cell—no contribution from the other sex required. The Amazon molly, however, is far from celibate. These fish still mate with males from closely related species because they need sperm to kick-start the development of their embryos. But none of the male’s genetic material gets passed on to the next generation. © 2026 American Association for the Advancement of Science.

Keyword: Sexual Behavior; Evolution
Link ID: 30158 - Posted: 03.14.2026

By Emma Gometz Caribou, large deer that are native to the northernmost parts of the world (and sometimes called reindeer), are the only deer whose females grow antlers. In a study published today, researchers observed behavior that might explain why: female caribou appear to gnaw on shed antlers as a kind of postbirthing supplement. Caribou migrate huge distances every year between the places where they graze during the winter and the grounds where they calve in the spring. They can walk thousands of miles per year and likely have the longest terrestrial migration of any animal. Caribou mothers complete these extremely long migrations with antlers on their head and a calf in their womb. The period is very nutritionally demanding for them but culminates with a reserve stock of supplements when they need it the most. The researchers behind the new study figured this out when they observed bite marks in more than 80 percent of the 1,500 caribou antlers that littered the part of the Arctic National Wildlife Refuge in northeastern Alaska where the deer give birth. “[Caribou] are just really going after the antlers. They are highly selective,” says study co-author Joshua Miller, a paleoecologist at the University of Cincinnati. Female caribou shed their antlers just days before giving birth. Miller and co-author Madison Gaetano, a conservation paleobiologist, say that the findings suggest that female caribou are essentially banking nutrients in the form of antlers before they give birth and then gnawing on their freshly shed antlers to get a boost of protein, calcium and phosphorus they need to make up for having less time to graze as they nurse their calves. © 2025 SCIENTIFIC AMERICAN,

Keyword: Sexual Behavior
Link ID: 30136 - Posted: 02.25.2026

By Natalia Mesa Most male mammals do not dote on their young and may even attack them, but some African striped mice actively feed, groom and nuzzle their own and even others’ pups. These profound behavioral differences come down to a single gene: agouti. This gene controls pigment production in the hair or skin of many animals. But in African striped mice, it also acts as a volume knob to silence caregiving circuits in the brain, according to a study published today in Nature. “It’s remarkable that this one gene is able to lead to a dramatic change in behavior,” says Robert Froemke, professor of genetics, neuroscience and otolaryngology at New York University, who was not involved in the work. Male African striped mice that live in isolation for roughly 2 months after weaning tend to nurture pups later in life, even those that are not their own, whereas their peers that live with other mice tend to be indifferent fathers or even infanticidal, the study found. The fatherly mice express lower levels of agouti in the brain compared with their more aggressive counterparts, the study shows. “Agouti, we think, is a molecular integrator of environmental experience,” says study author Ricardo Mallarino, associate professor of molecular biology at Princeton University. Despite the fact that only about 5 percent of mammalian species show fatherly behavior, parental care may be the default mode in striped mice, the research suggests. Both males and females use the same brain circuitry to care for their young, but enhanced agouti expression in the brain suppresses these instincts in the former. © 2026 Simons Foundation

Keyword: Sexual Behavior; Aggression
Link ID: 30133 - Posted: 02.21.2026