Assisted reproduction kids grow up just fine – but it may be better to tell them early about biological origins, twenty-year study suggests

Landmark study finds no difference in psychological wellbeing or quality of family relationships between children born by assisted reproduction (egg or sperm donation or surrogacy) and those born naturally at age 20

Peer-Reviewed Publication

UNIVERSITY OF CAMBRIDGE

Paper available at: https://drive.google.com/drive/folders/1y9GfgYkRdUtwyq6nBhySePTUHZYP6iAj?usp=share_link

• Landmark study finds no difference in psychological wellbeing or quality of family relationships between children born by assisted reproduction (egg or sperm donation or surrogacy) and those born naturally at age 20.
• However, findings suggest that telling children about their biological origins early – before they start school – can be advantageous for family relationships and healthy adjustment. 
• THIS ALSO APPLIES TO ADOPTED CHILDREN

The study, by University of Cambridge researchers, is the first to examine the long-term effects of different types of third-party assisted reproduction on parenting and child adjustment, as well as the first to investigate prospectively the effect of the age at which children were told that they were conceived by egg donation, sperm donation or surrogacy.

The results, published today in Developmental Psychology, suggest that the absence of a biological connection between children and parents in assisted reproduction families does not interfere with the development of positive relationships between them or psychological adjustment in adulthood. These findings are consistent with previous assessments at age one, two, three, seven, ten and 14.

The findings overturn previous widely held assumptions that children born by third-party assisted reproduction are at a disadvantage when it comes to wellbeing and family relationships because they lack a biological connection to their parents.

“Despite people's concerns, families with children born through third-party assisted reproduction – whether that be an egg donor, sperm donor or a surrogate – are doing well right up to adulthood,” said Susan Golombok, Professor Emerita of Family Research and former Director of the Centre for Family Research, University of Cambridge, who led the study.

However, they found that mothers who began to tell their children about their biological origins in their preschool years had more positive relationships with them as assessed by interview at age 20, and the mothers showed lower levels of anxiety and depression. Most of the parents who had disclosed did so by age four and found that the child took the news well. This suggests that being open with children about their origins when they are young is advantageous.

In addition, in the final stage of this 20-year study, mothers who had disclosed their child’s origins by seven years old obtained slightly more positive scores on questionnaire measures of quality of family relationships, parental acceptance (mother’s feelings towards young adult), and family communication. For example, only 7% of mothers who had disclosed by age 7 reported problems in family relationships, compared with 22% of those who disclosed after age 7.

The young adults who had been told about their origins before seven obtained slightly more positive scores on questionnaire measures of parental acceptance (young adult’s perception of mother’s feelings towards them), communication (the extent to which they feel listened to, know what’s happening in their family and receive honest answers to questions), and psychological wellbeing. They were also less likely to report problems on the family relationships questionnaire; whereas 50% of young adults told after age 7 reported such problems, this was true of only 12.5% of those told before age 7.

“There does seem to be a positive effect of being open with children when they’re young – before they go to school – about their conception. It’s something that’s been shown by studies of adoptive families too,” said Golmobok.

Researchers from the University of Cambridge followed 65 UK families with children born by assisted reproduction ­– 22 by surrogacy, 17 by egg donation and 26 by sperm donation – from infancy through to early adulthood (20 years old). They compared these families with 52 UK unassisted conception families over the same period.

“The assisted reproduction families were functioning well, but where we did see differences, these were slightly more positive for families who had disclosed,” said Golombok.

Reflecting on their feelings about their biological origins, the young adults were generally unconcerned. As one young adult born through surrogacy put it, “It doesn’t faze me really, people are born in all different ways and if I was born a little bit differently - that’s OK, I understand.”

Another young adult born through sperm donation said, “My dad’s my dad, my mum’s my mum, I've never really thought about how anything’s different so, it's hard to put, I don’t really care.”

Some young adults actively embraced the method of their conception as it made them feel special, “I think it was amazing, I think the whole thing is absolutely incredible. Erm…I don’t have anything negative to say about it at all.”

Researchers found that egg donation mothers reported less positive family relationships than sperm donation mothers. They suggest that this could be due to some mothers’ insecurities about the absence of a genetic connection to their child. This was not reflected in the young adults’ perceptions of the quality of family relationships.

The team also found that young adults conceived by sperm donation reported poorer family communication than those conceived by egg donation. This could be explained by the greater secrecy around sperm donation than egg donation, sometimes driven by greater reluctance of fathers than mothers to disclose to their child that they are not their genetic parent, and a greater reluctance to talk about it once they have disclosed.

In fact, researchers found that only 42% of sperm donor parents disclosed by age 20, compared to 88% of egg donation parents and 100% of surrogate parents.

“Today there are so many more families created by assisted reproduction that it just seems quite ordinary,” said Golombok. “But twenty years ago, when we started this study, attitudes were very different. It was thought that having a genetic link was very important and without one, relationships wouldn’t work well.

“What this research means is that having children in different or new ways doesn’t actually interfere with how families function. Really wanting children seems to trump everything – that’s what really matters.”

This research was funded by a Wellcome Trust Collaborative Award.

The Centre for Family Research is collaborating with the Fitzwilliam Museum on a new exhibition, Real Families: Stories of Change (October – 7 January 2024), curated by Professor Golombok. The exhibition will explore the intricacies of families and family relationships through the eyes of artists including Paula Rego, Chantal Joffe, JJ Levine, Lucian Freud and Tracey Emin.

Professor Susan Golombok is author of We Are Family: What Really Matters for Parents and Children (Scribe) which describes researching new family forms from the 1970s to the present day.

ENDS.

Reference:

Golombok, S., Jones, C., Hall, P., Foley, S., Imrie, S., &  Jadva, V. A longitudinal study of families formed through third-party assisted reproduction: Mother-child relationships and child adjustment from infancy to adulthood. Developmental Psychology DOI: 10.1037/dev0001526

Jadva, V., Jones, C. M., Hall, P., Imrie, S., & Golombok, S. “I know it’s not normal but it’s normal to me and that’s all that matters”: The experiences of young adults conceived through egg donation, sperm donation and surrogacy. Human Reproduction DOI: 10.1093/humrep/dead048

Contact details:

Charis Goodyear, University of Cambridge Charis.Goodyear@admin.cam.ac.uk

Professor Susan Golombok, University of Cambridge seg42@cam.ac.uk

About the University of Cambridge

The University of Cambridge is one of the world’s leading universities, with a rich history of radical thinking dating back to 1209. Its mission is to contribute to society through the pursuit of education, learning and research at the highest international levels of excellence.

Cambridge was second in the influential 2023 QS World University Rankings, the highest rated institution in the UK.

The University comprises 31 autonomous Colleges and over 100 departments, faculties and institutions. Its 20,000 students include around 9,000 international students from 147 countries. In 2022, 72.5% of its new undergraduate students were from state schools and more than 25% from economically disadvantaged backgrounds.

Cambridge research spans almost every discipline, from science, technology, engineering and medicine through to the arts, humanities and social sciences, with multi-disciplinary teams working to address major global challenges. In the Times Higher Education’s rankings based on the UK Research Excellence Framework, the University was rated as the highest scoring institution covering all the major disciplines.

The University sits at the heart of the ‘Cambridge cluster’, in which more than 5,200 knowledge-intensive firms employ more than 71,000 people and generate £19 billion in turnover. Cambridge has the highest number of patent applications per 100,000 residents in the UK.

www.cam.ac.uk

Real Families: Stories of Change

6 October – 7 January 2024

Real Families is a major exhibition exploring the intricacies of families and family relationships through the eyes of artists. The theme of the family has been interpreted and represented for centuries, but, especially during the last fifty years, Western ideas of what makes a family and how family life is experienced have been transformed by advances in science and by changes in social attitudes and law. Developed in collaboration with the world-leading Centre for Family Research at the University of Cambridge, the exhibition shows how the joys, tensions and transitions in families have little to do with conforming to traditional structures. Instead, acceptance, rejection, conflict and comfort arise from relationships within family groups of all kinds, and through connections with the outside world. Painting, photography, video, sculpture and installations by artists including Paula Rego, Chantal Joffe, JJ Levine, Lucian Freud and Tracey Emin tell moving and enduring stories of intimacy, alienation and everything in between.

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JOURNAL

Developmental Psychology

DOI

10.1037/dev0001526 

SUBJECT OF RESEARCH

People

ARTICLE TITLE

A longitudinal study of families formed through third-party assisted reproduction: Mother-child relationships and child adjustment from infancy to adulthood.

ARTICLE PUBLICATION DATE

13-Apr-2023

SFU professor unearths the ancient fossil plant history of Burnaby Mountain

Peer-Reviewed Publication

SIMON FRASER UNIVERSITY

 

IMAGE: FIG. 4. REPRODUCTIVE PLANT MACROFOSSILS FROM THE SIMON FRASER UNIVERSITY EXPOSURE. A, PARTIAL TRILOBED FRUITING BRACT OF PALAEOCARYA CF. P. WOLFEI, SIMILAR TO BRACTS OF LIVING ENGELHARDIA. B, FRUIT VALVE OF THE MALVACEOUS CRAIGIA. C, LIQUIDAMBAR FRUIT CLUSTER SHOWING THE WOODY ELONGATED STYLES OF THE EMBEDDED CAPSULES. D, STERILE FLOWER OF HYDRANGEA. E, FLORAL CALYX OF FLORISSANTIA CF. F. SPEIRII. THE SPECIES IS UNCERTAIN BUT BASED ON THE LARGE SIZE OF THE CALYX (DIAMETER = 51 MM), WHICH IS MOST SIMILAR TO F. SPEIRII. ALL SCALES ARE IN MILLIMETERS. view more 

CREDIT: SIMON FRASER UNIVERSITY

New research led by Simon Fraser University paleobotanist Rolf Mathewes provides clues about what plants existed in the Burnaby Mountain area (British Columbia, Canada) 40 million years ago during the late Eocene, when the climate was much warmer than it is today. The results of their plant fossil analysis were recently published in the International Journal of Plant Sciences.

Mathewes as an undergraduate, and his supervisor at the time, professor Robert C. Brooke, found and collected plant fossils from a deposit exposed during the construction of the university in the late 1960s. The fossils were kept at SFU but remained locked away in cabinets for many years until Mathewes returned to the collection as a professor. He dedicates the paper to the memory of Brooke, his late supervisor and mentor.

One of the fossils identified by their colleague David Greenwood, from Brandon University, is of a palm leaf fragment. The team also identified a hydrangea flower and the flower of an extinct plant from the same family as the basswood, a tree native to Eastern North America. A microscopic analysis of fossil pollen extracted from the fine shale also reveals the presence of alders, ferns, elms, sweetgum, and many other plants.

 “These plant fossils tell us the climate was warm temperate to subtropical because of the presence of palms,” says Mathewes, study lead and SFU professor of paleoecology & palynology. “If you wanted an analogue for what the climate was like compared to today, the conditions would be similar to the East Coast of the United States somewhere around Wilmington, North Carolina, where palms are still native today.”  

Study co-author Tammo Reichgelt (University of Connecticut) used new climate modelling techniques to confirm the warmer conditions.

Although planted palms can be found growing in the Lower Mainland today, Mathewes notes that these plants would not survive here on their own as they did in the distant past.

“Even if they flowered and produced seeds, their young seedlings would never be able to compete with the seedlings of Douglas fir and hemlocks and alders that are our native vegetation and probably would die in the first hard frost of winter,” he says.

He explains that most of Burnaby Mountain is comprised of sandstone and gravel but the fossils are only preserved on shale or mudstone. In the late Eocene, Burnaby Mountain had not yet formed and was a floodplain, like the Fraser River Delta, with ponds and river channels with vegetation growing near sea level.

The plants and trees growing on the floodplain deposited their leaves, flowers and pollen into the fine sediment of a shallow lake or pond. Their fossils formed through a process of being compressed under layers of sediment for millions of years.

One of the fossil leaves clearly displays round feeding marks made by an insect, and Mathewes says there is still much to be discovered, identified and studied from the pollen samples and a second fossil deposit site.

Fig. 7. A, Large leaf of cf. Anacardites franklinensis, a species defined by Wolfe from the Eocene Puget Group. B, One of several leaf fragments of an uncertain Myrtaceae (Syzgoides), based on an entire-margined leaf with a strong midvein and thin, closely spaced eucamptodromous secondaries that connect to an intramarginal vein (arrow). C, Unidentified cordate leaf with actinodromous venation, entire margin, and fimbrial vein visible along lower margin, suggestive of Menispermaceae. D, Insect body fossils have not been found in the Burnaby Mountain sediments, but some examples of insect leaf damage are present, like this unidentified dicot leaf with rounded skeletonized feeding spots. All scales are in millimeters.

Fig. 6. Selected dicot leaves. A, Dryophyllum pugetensis leaf confirming craspedodromous venation, with teeth concentrated in distal portion of lamina, and showing a slight trend to falcate curvature. B, Leaf of Platanus with distinctive platanaceous teeth at leaf tip. C, Basal portion of cf. Acer leaf, with long petiole and basal actinodromous primary venation. D, Leaf of cf. Alnus, craspedodromous with two tooth sizes. Alder pollen is also present. E, Leaf of cf. Rhamnus, with dense apically curving semicraspedodromous secondary veins. This leaf closely matches morphology of extant Rhamnus purshianus but does not show the minute teeth at the leaf edge. All scales are in millimeters.

CREDIT

Simon Fraser University

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JOURNAL

International Journal of Plant Sciences

DOI

10.1086/724156 

ARTICLE TITLE

Plant Megafossils, Palynomorphs, and Paleoenvironment from the Late Middle to Late Eocene Burnaby Mountain Flora, Huntingdon Formation, British Columbia, Canada

Oldest bat skeletons ever found

described from Wyoming fossils

52-million-year-old fossils support idea that bats diversified rapidly on multiple continents during the Eocene

Peer-Reviewed Publication

AMERICAN MUSEUM OF NATURAL HISTORY

 

IMAGE: A PHOTO OF ONE OF THE TWO NEWLY DESCRIBED BAT SKELETONS REPRESENTING ICARONYCTERIS GUNNELLI. THIS SPECIMEN, THE HOLOTYPE, IS NOW IN THE AMERICAN MUSEUM OF NATURAL HISTORY’S RESEARCH COLLECTIONS. view more 

CREDIT: MICK ELLISON/©AMNH

Scientists have described a new species of bat based on the oldest bat skeletons ever recovered. The study on the extinct bat, which lived in Wyoming about 52 million years ago, supports the idea that bats diversified rapidly on multiple continents during this time. Led by researchers at the American Museum of Natural History and Naturalis Biodiversity Center in the Netherlands, the study is published today in the journal PLOS ONE.

There are more than 1,460 living species of bats found in nearly every part of the world, with the exception of the polar regions and a few remote islands. In the Green River Formation of Wyoming—a remarkable fossil deposit from the early Eocene—scientists have uncovered over 30 bat fossils in the last 60 years, but until now they were all thought represent the same two species.

“Eocene bats have been known from the Green River Formation since the 1960s. But interestingly, most specimens that have come out of that formation were identified as representing a single species, Icaronycteris index, up until about 20 years ago, when a second bat species belonging to another genus was discovered,” said study co-author Nancy Simmons, curator-in-charge of the Museum’s Department of Mammalogy, who helped describe that second species in 2008. “I always suspected that there must be even more species there.”

In recent years, scientists from the Naturalis Biodiversity Center started looking closely at Icaronycteris index by collecting measurements and other data from museum specimens.

“Paleontologists have collected so many bats that have been identified as Icaronycteris index, and we wondered if there were actually multiple species among these specimens,” said Tim Rietbergen, an evolutionary biologist at Naturalis. “Then we learned about a new skeleton that diverted our attention.”

The exceptionally well-preserved skeleton was collected by a private collector in 2017 and purchased by the Museum. When researchers compared the fossil to Rietbergen’s expansive dataset, it clearly stood out as a new species. A second fossil skeleton discovered in the same quarry in 1994 and in the collections of the Royal Ontario Museum was also identified as this new species. The researchers gave these fossils the species name Icaronycteris gunnelli in honor of Gregg Gunnell, a Duke University paleontologist who died in 2017 and made extensive contributions to the understanding of fossil bats and evolution.

Although there are fossil bat teeth from Asia that are slightly older, the two I. gunnelli fossils represent the oldest bat skeletons ever found.

“The Fossil Lake deposits of the Green River Formation are simply amazing because the conditions that created the paper-thin limestone layers also preserved nearly everything that settled to the lake’s bottom,” said Arvid Aase, park manager and curator at the Fossil Butte National Monument, in Wyoming. “One of these bat specimens was found lower in the section than all other bats, making this species older than any of the other bat species recovered from this deposit."

While the I. gunnelli skeletons are the oldest bat fossils from this site, they are not the most primitive, supporting the idea that Green River bats evolved separately from other Eocene bats around the world.

“This is a step forward in understanding what happened in terms of evolution and diversity back in the early days of bats,” Simmons said.

 

ABOUT THE AMERICAN MUSEUM OF NATURAL HISTORY (AMNH)

The American Museum of Natural History, founded in 1869 to advance research in science and education, is one of the world’s preeminent scientific, educational, and cultural institutions. The Museum encompasses more than 40 permanent exhibition halls, galleries for temporary exhibitions, the Rose Center for Earth and Space including the Hayden Planetarium, and the Richard Gilder Center for Science, Education, and Innovation, opening May 4. The Museum’s scientists draw on a world-class permanent collection of more than 34 million specimens and artifacts, some of which are billions of years old, and on one of the largest natural history libraries in the world. Through its Richard Gilder Graduate School, the Museum offers two of the only free-standing, degree-granting programs of their kind at any museum in the U.S.: the Ph.D. program in Comparative Biology and the Master of Arts in Teaching (MAT) Earth Science residency program, whose graduates make up approximately half of New York City’s certified Earth Science teachers. Visit amnh.org for more information.

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JOURNAL

PLoS ONE

DOI

10.1371/journal.pone.0283505 

ARTICLE TITLE

The oldest known bat skeletons and their implications for Eocene chiropteran diversification

ARTICLE PUBLICATION DATE

12-Apr-2023

Sex of blood donor has no effect on recipient survival

Innovative clinical trial answers long-standing question and paves the way for lower-cost pragmatic trials

Peer-Reviewed Publication

THE OTTAWA HOSPITAL

 

IMAGE: DR. DEAN FERGUSSON HOLDING A UNIT OF BLOOD view more 

CREDIT: THE OTTAWA HOSPITAL

A large clinical trial of more than 8,700 patients published in the New England Journal of Medicine concluded that the sex of a donor has no effect on the survival of recipients of red blood cell transfusions.

“Some observational studies had suggested female donor blood might be linked with a higher risk of death among recipients compared to male donor blood, but our clinical trial found that isn’t the case,” said co-lead author Dr. Dean Fergusson, a senior scientist at The Ottawa Hospital, Director of the hospital’s Clinical Epidemiology Program and professor at the University of Ottawa.

The possible impact of the sex of a blood donor on recipient survival has been an unanswered question in transfusion medicine since 2015, when the American National Heart, Lung and Blood Institute identified it as a research priority. Some evidence suggested that sex-related differences such as hormone levels in male and female blood might affect recipient survival, but the results of observational studies have been conflicting.

“To answer this question definitively we needed a large, randomized clinical trial, but those studies are incredibly expensive,” said Dr. Michaël Chassé, co-lead author of the study and intensivist at Centre hospitalier de l'Université de Montréal and associate professor at Université de Montréal. “By embedding this trial in real-world practice and using practical methods, we answered this question for a fraction of what a trial would normally cost.”

The research team estimates that using typical trial methods, this trial would have cost $9 million, but with their innovative approach, it only cost $300,000. The approach involved enrolling every adult patient at The Ottawa Hospital who might need a transfusion, randomizing them to receive male or female blood, and then collecting data from existing hospital databases and provincial registries. As male and female blood were considered equivalent treatments, patients did not need to provide written consent to join the trial, but were given the option to opt out after the first transfusion. With this pragmatic approach, the team was able to enroll 8,719 participants into their double-blind, randomized trial in just over two years.

The study did not include patients without an Ontario Health Insurance Plan number, those who were massively bleeding and needed blood right away, and those with a complex antibody profile which made blood unit matching difficult.

Study participants were randomly assigned to receive either male or female donor blood at all visits to The Ottawa Hospital during the study period. Eighty per cent of patients received their first transfusion while they were an inpatient, and 42 per cent of those received it during surgery.

Patient characteristics, laboratory and clinical data, and blood bank data were obtained from The Ottawa Hospital Data Warehouse. Blood donor data from Canadian Blood Services was linked with hospital data and health administrative data at ICES.

The study found no statistically significant differences in overall survival between recipients of male donor blood and recipients of female donor blood.

“Blood is the most common life-saving treatment given in hospital,” said Dr. Jason Acker, senior scientist at Canadian Blood Services. “As a blood provider, we were happy to help answer this very important question in transfusion medicine. We hope the findings encourage all eligible donors to continue to donate.”

Full reference: The effect of donor sex on recipient mortality in transfusion. Michaël Chassé, Dean A Fergusson, Alan Tinmouth, Jason P Acker, Iris Perelman, Angie Tuttle, Shane English, Steven Hawken, Alan J Forster, Nadine Shehata, Kednapa Thavorn, Kumanan Wilson, Nancy Cober, Heather Maddison, Melanie Tokessy. New England Journal of Medicine. April 12, 2023.

Funding: This study was funded by the Canadian Institutes of Health Research. All research at The Ottawa Hospital is also enabled by generous donors to The Ottawa Hospital Foundation. 

Core resources: Ottawa Methods Centre, The Ottawa Hospital Data Warehouse, ICES

About The Ottawa Hospital 
The Ottawa Hospital is one of Canada’s top learning and research hospitals, where excellent care is inspired by research and driven by compassion. As the third-largest employer in Ottawa, our support staff, researchers, nurses, physicians, and volunteers never stop seeking solutions to the most complex health-care challenges. Our multi-campus hospital, affiliated with the University of Ottawa, attracts some of the most influential scientific minds from around the world. Backed by generous support from the community, we are committed to providing the world-class, compassionate care we would want for our loved ones. www.ohri.ca

About the University of Ottawa
The University of Ottawa is home to over 54,000 students, faculty and staff, who live, work and study in both French and English. Our campus is a crossroads of cultures and ideas, where bold minds come together to inspire game-changing ideas. We are one of Canada’s top 10 research universities—our professors and researchers explore new approaches to today’s challenges. One of a handful of Canadian universities ranked among the top 200 in the world, we attract exceptional thinkers and welcome diverse perspectives from across the globe. www.uottawa.ca

About the CRCHUM

The University of Montreal Hospital Research Centre (CRCHUM) is one of North America’s leading hospital research centres. It strives to improve adult health through a research continuum covering such disciplines as the fundamental sciences, clinical research and public health. Over 2,300 people work at the CRCHUM, including more than 500 researchers and more than 520 graduate students. chumontreal.qc.ca/crchum @CRCHUM

About Université de Montréal

Deeply rooted in Montreal and dedicated to its international mission, Université de Montréal is one of the top universities in the French-speaking world. Founded in 1878, Université de Montréal today has 13 faculties and schools, and together with its two affiliated schools, HEC Montréal and Polytechnique Montréal, constitutes the largest centre of higher education and research in Québec and one of the major centres in North America. It brings together 2,400 professors and researchers and has more than 67,000 students. umontreal.ca

ICES is an independent, non-profit research institute that uses population-based health information to produce knowledge on a broad range of health care issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting health care needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy. In October 2018, the institute formerly known as the Institute for Clinical Evaluative Sciences formally adopted the initialism ICES as its official name. For the latest ICES news, follow us on Twitter: @ICESOntario

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JOURNAL

New England Journal of Medicine

DOI

10.1056/NEJMoa2211523 

METHOD OF RESEARCH

Randomized controlled/clinical trial

SUBJECT OF RESEARCH

People

ARTICLE TITLE

The effect of donor sex on recipient mortality in transfusion

ARTICLE PUBLICATION DATE

12-Apr-2023

Timing of snowshoe hare winter color swap may leave them exposed in changing climate, study finds

Peer-Reviewed Publication

UNIVERSITY OF FLORIDA

 

IMAGE: SNOWSHOE HARE IN WINTER COAT IN A SNOWY LANDSCAPE IN KLUANE, YUKON, CANADA. PURE WHITE WINTER COAT PROVIDES CAMOUFLAGE AGAINST SNOW, WHICH REDUCES RISK OF BEING SEEN AND CAUGHT BY PREDATORS. view more 

CREDIT: ALICE KENNEY

Like many animals in the far north, snowshoe hares change their coats from brown to white each autumn. Come winter, these all-white hares are harder for predators to spot against the snowy landscape, helping ensure their survival.

But as global warming reduces snowfall in the region, will the hares’ seasonal color swap continue to keep them safe?

Scientists from the University of Florida and Canada are beginning to answer that question. Their new study, which used 44 years of data on snowshoe hares in Canada’s Yukon Territory, shows that as the region has warmed, hares are waiting longer to turn pure white.

However, the data also suggest that waiting too long can be deadly. The scientists found that hares that were more brown than white in autumn were less likely to survive the winter  

“When it comes to the switch from brown to white, which we call molting, timing is everything. We can see in this study that climate change is making it harder for the hares to get that timing just right.” said Madan Oli, first author of the study and a professor in the UF/IFAS wildlife ecology and conservation department.  “Hares begin to change color based on environmental cues such as temperature and snow depth, but the change doesn’t happen overnight. The whole molting process takes about a month. So, if hares are beginning to molt later in the year, there is a greater chance they will not be fully white by the time their environment is white. These hares are then more vulnerable to predators.”

Snowshoe hares are what ecologists call a keystone species because so many other animals depend on them for food, said Charles Krebs, senior author of the study and a professor emeritus at the University of British Columbia.

If the snowshoe hare population takes a nosedive, this could affect the entire ecosystem, he said.

“Practically everything eats snowshoe hares in the boreal forest. A big change in the number that survive the winter impacts their ability to replenish themselves over the summer breeding season, which could disrupt the whole food web,” Krebs said. The boreal forest, or taiga, rings the norther part of the globe and includes parts of Alaska, Canada, Europe and Asia. 

Snowshoe hares are among 21 bird and mammal species in boreal forest that turn white for winter, which scientists call seasonal molting. This study is the first to track how seasonal molting has shifted with rising global temperatures.

The decades of data collection by Krebs and colleagues also makes the study unique, Krebs said.

“When you look over a forty-four-year span, you can really document a pattern. This study demonstrates the value and importance of long-term ecological monitoring,” Krebs said.

Between 1977 and 2021, Krebs and his collaborators went to the Kluane National Park and Reserve in Canada’s Yukon Territory each autumn and spring to study snowshoe hares. In the remote, often extremely cold wilderness they trapped snowshoe hares, recorded the percentage of white and brown in each hare’s coat, tagged each hare (or noted if it was already tagged) and set it free.

The researchers recorded observations for nearly 4,500 hares, with some caught multiple times over the years. Oli, who specializes in evaluating animal populations from a statistical and modeling perspective, and then wildlife ecology doctoral candidate Vratika Chaudhary, analyzed this massive dataset. The current study presents the results of that analysis.  

The team isn’t done studying snowshoe hares in the Yukon, Krebs said. The scientists are currently recording the hare coat color and behavior using motion activated cameras. Images captures by these cameras will show how much — or how little — the hares coats are helping them match their environment in real time.

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JOURNAL

Proceedings of the Royal Society B Biological Sciences

DOI

10.1098/rspb.2022.1421 

ARTICLE TITLE

Does coat colour influence survival? A test in a cyclic population of snowshoe hares

A mismatched snowshoe hare in winter coat in a snow-free landscape in Kluane, Yukon, Canada. Pure white winter coat against snow-free landscape makes snowshoe hares easily detectable by predators, which can reduce their survival during the winter. The study found, however, that hares that wait longer to turn white in autumn face the greatest chance of being eaten by predators during the winte

White snowshoe hare.

CREDIT

Photo credit: Lance Goodwin

Brown snowshoe hare. Hares turn brown for the summer when the snows recede.

Brown snowshoe hare. Hares turn brown for the summer when the snows recede.

CREDIT

Photo credit: Alice Kenney