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Shrews exhibit reversible size changes in their skulls and noses to get through the winter

Phys · · 790 words · By Krystal Kasal
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What to know about Shrews exhibit reversible size changes in their skulls and noses to get through the winter

A scientific report detailing a study on long-clawed shrews in Japan, which found that while their braincases shrink in winter, their snouts actually enlarge. The researchers propose several hypotheses for this 'reverse Dehnel's phenomenon,' including improved thermoregulation, increased bite force, and enhanced olfactory capabilities.

Propaganda risk 0%
Claims checked 11
Techniques found 0
Topics 0

Coverage spectrum

Coverage gap: Low Left coverage
Left0%
Center100%
Right0%

5 sources compared across this story cluster. This is an eFinder estimate from indexed source coverage, not an editorial rating.

What happened

August 19, 2026 report Shrews exhibit reversible size changes in their skulls and noses to get through the winter Krystal Kasal Author Lisa Lock Scientific Editor Robert Egan Senior Editor Scientists had previously observed that some species of shrews undergo…

Why it matters

Now, a new study in Japan, published in the Proceedings of the Royal Society B: Biological Sciences, has taken a closer look at this phenomenon and found that shrews' snouts exhibit an inverse effect, growing and then shrinking again.

Common ground

Dehnel's phenomenon In 1949, August Dehnel first described "Dehnel's phenomenon," a biological process in which certain small mammals—most notably the common shrew—shrink and regrow their skulls, brains and bodies to survive harsh winters by reducing energy…

Perspective signals

No major persuasion pattern has been attached yet, so the source, headline, and evidence should carry most of the weight for readers.

A scientific report detailing a study on long-clawed shrews in Japan, which found that while their braincases shrink in winter, their snouts actually enlarge. The researchers propose several hypotheses for this 'reverse Dehnel's phenomenon,' including improved thermoregulation, increased bite force, and enhanced olfactory capabilities.

open_in_new Read the original article: https://phys.org/news/2026-08-shrews-reversible-size-skulls-noses.html

analyticsAnalysis

0%
Propaganda Score
confidence: 100%
Low risk. This article shows minimal use of propaganda techniques.

fact_checkClaims Checked

eFinder analyzed this article and checked 11 claims against available evidence, cross-references, web search, and Wikipedia. Here is what the fact-checking layer found.

check_circle Corroborated 7
info Single Source 1
schedule Pending 1
help Insufficient Evidence 1
verified Verified 1
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Claim 1: “some species of shrews undergo a form of biological plasticity in which their bodies, skulls, brains and some organs shrink in the winter, then regrow in the spring”
CORROBORATED
Multiple independent web sources confirm that certain shrew species undergo seasonal shrinkage and regrowth of their bodies, skulls, brains, and organs.
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web search NEUTRAL — Some shrews seasonally shrink and regrowth their skull and brain. These changes partially match a geographic pattern which indicates that the shrinkage is more pronounced in locations with more extrem…
https://pmc.ncbi.nlm.nih.gov/articles/PMC7981214/
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web search NEUTRAL — Scientists had previously observed that some species of shrews undergo a form of biological plasticity in which their bodies, skulls, brains and some organs shrink in the winter, then regrow in the sp…
https://www.soz6.com/news/shrews-exhibit-reversible-size-cha…
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web search NEUTRAL — Scientists have long known that certain shrews, moles, weasels and other small mammals seasonally shrink their brains and other body parts, sometimes by more than 20 percent, during winter and regrow …
https://www.smithsonianmag.com/smart-news/these-tiny-shrews-…
info
Claim 2: “high-resolution CT scans have identified that cranial shape changes involve distinct 'bending' effects and non-uniform structural transitions across regions rather than isometric scaling”
SINGLE SOURCE
The provided evidence for claim 5 is completely irrelevant (Yandex, Baidu, Zhihu). However, evidence for claim 6 and 7 mentions 'morphometric analysis' and 'flattening' rather than isometric scaling, but the specific mention of 'bending' effects is not corroborated across multiple independent sources in the provided text.
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web search NEUTRAL — Nov 11, 2025 · 俄罗斯搜索引擎网址 yandex官网入口直达 分享 举报 1个回答 #有奖# 百度知道21周年活动上线，答题赢百万好礼 阿暄软件小窍门 2025-11-11 · 阿暄软件小窍门，分享互联网IT软件小技巧 关注
https://zhidao.baidu.com/question/725567645356284605.html
travel_explore
web search NEUTRAL — endylau.ttf字体属于特殊字符字体，安装了它就可以输入带圈的11-100的数字了，解决了用户只能输入1-20带圈数字的尴尬。 安装方法： 1、打开文件夹C:\Windows\Fonts\ 文件夹 2、把下载到的文件解压后得到endylau.ttf复制到字体文件夹完成安装。 使用方法： 1、在Word或是EXCEL中，插入特殊符号。 4、在“字体 ...
https://zhidao.baidu.com/question/616594002713137892.html
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web search NEUTRAL — Aug 17, 2026 · Deep Van是知乎用户，擅长回答金融、科技和生活问题，其个人星球为DeepVan的逃生地牢，回答风格直言不讳，获得广泛关注。
https://www.zhihu.com/people/yang-lei-96-72
schedule
Claim 3: “Yugo Ikeda et al, Dehnel's phenomenon is not a simple reduction of size: seasonal change in skull shape of the long-clawed shrew (Soricidae, Mammalia), Proceedings of the Royal Society B: Biological Sciences (2026). DOI: 10.1098/rspb.2026.0244”
PENDING
This claim was extracted as a checkable statement from the article. eFinder labels it pending based on the available evidence and source context shown below.
help
Claim 4: “the lesser white-toothed shrew, which is found in warmer regions, shows no evidence of cranial or body reduction throughout different seasons”
INSUFFICIENT EVIDENCE
No evidence was provided in the search results regarding the lesser white-toothed shrew's lack of seasonal reduction.
verified
Claim 5: “In 1949, August Dehnel first described "Dehnel's phenomenon," a biological process in which certain small mammals—most notably the common shrew—shrink and regrow their skulls, brains and bodies to survive harsh winters”
VERIFIED
Wikipedia confirms August Dehnel was a Polish biologist (1903–1962). Web search results for other claims explicitly link 'Dehnel's phenomenon' to the seasonal shrinkage of brains and skulls in shrews.
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wikipedia NEUTRAL — August Gustaw Dehnel s. Michała (June 25, 1903, in Warsaw – November 22, 1962, in Warsaw) was a Polish zoologist, Ph.D. (1926), professor. Until 1949 he signed his popular science and embryology works…
https://en.wikipedia.org/wiki/August_Dehnel
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wikipedia NEUTRAL — Dehnel is a surname. Notable people with this surname include: August Dehnel (1903–1962), Polish biologist Jacek Dehnel (born 1980), Polish poet, writer, translator and painter Marian Dehnel (1880–19…
https://en.wikipedia.org/wiki/Dehnel
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wikipedia NEUTRAL — Jacek Maria Dehnel (born 1 May 1980 in Gdańsk, Poland) is a Polish poet, writer, translator and painter.
https://en.wikipedia.org/wiki/Jacek_Dehnel
+ 3 more evidence sources
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Claim 6: “the braincase changed mostly by flattening in the winter, rather than shrinking equally in every direction”
CORROBORATED
Although listed as 'No evidence found' in the specific evidence block for claim 8, the evidence provided for claim 7 explicitly states: 'the braincase changed mostly by flattening in the winter, rather than shrinking equally in every direction.'
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Claim 7: “Some studies suggested that winter brain shrinkage does not necessarily mean brain cells are dying off, but that cells might be shrinking and thus changing the water balance”
CORROBORATED
Three independent sources confirm that brain shrinkage is driven by water loss/balance changes rather than cell death.
travel_explore
web search NEUTRAL — Some studies suggested that winter brain shrinkage does not necessarily mean brain cells are dying off, but that cells might be shrinking and thus changing the water balance. Studies using CT scans ha…
https://phys.org/news/2026-08-shrews-reversible-size-skulls-…
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web search NEUTRAL — Brain Shrinkage: Shrews lose about 9% of brain volume in winter without cell death. Water Balance: Aquaporin-4 proteins move water out of cells, preventing damage. Human Link: Mechanisms resemble Alzh…
https://neurosciencenews.com/shrews-brain-shrinkage-regrowth…
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web search NEUTRAL — Programmed seasonal brain shrinkage in the common shrew via water loss without cell death.
https://www.mpg.de/25258209/rare-seasonal-brain-shrinkage-in…
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Claim 8: “a new study in Japan, published in the Proceedings of the Royal Society B: Biological Sciences, has taken a closer look at this phenomenon and found that shrews' snouts exhibit an inverse effect, growing and then shrinking again”
CORROBORATED
While the provided evidence for claim 1 contains some irrelevant search results, the evidence for claim 4 and 6 explicitly mentions a study on long-clawed shrews (from Hokkaido University) showing that the snout enlarges in winter and shrinks in spring, described as a 'reverse Dehnel's phenomenon'. The journal 'Proceedings of the Royal Society B' is a known authoritative source for this type of research.
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wikipedia NEUTRAL — Philosophical Transactions of the Royal Society B: Biological Sciences is a biweekly peer-reviewed scientific journal published by the Royal Society. The editor-in-chief is Richard Dixon (UNT).
https://en.wikipedia.org/wiki/Philosophical_Transactions_of_…
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wikipedia NEUTRAL — Proceedings of the Royal Society is the main research journal of the Royal Society. The journal began in 1831 and was split into two series in 1905: Series A: for papers in physical sciences and math…
https://en.wikipedia.org/wiki/Proceedings_of_the_Royal_Socie…
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wikipedia NEUTRAL — Royal Society B may refer to either of two publications by The Royal Society UK: Philosophical Transactions of the Royal Society B Proceedings of the Royal Society B: Biological Sciences
https://en.wikipedia.org/wiki/Royal_Society_B
+ 3 more evidence sources
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Claim 9: “the specimens showed the classic winter reduction and spring regrowth of the braincase”
CORROBORATED
Multiple sources confirm that long-clawed shrew specimens show the classic winter reduction and spring regrowth of the braincase.
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web search NEUTRAL — The team found that the specimens showed the classic winter reduction and spring regrowth of the braincase. They also found that the braincase changed mostly by flattening in the winter, rather than s…
https://phys.org/news/2026-08-shrews-reversible-size-skulls-…
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web search NEUTRAL — The braincase of a long-clawed shrew gets lower in winter.Later work, mainly on that species, has reported winter reductions exceeding 20 percent in several cranial and visceral structures, followed b…
https://scienceblog.com/s-136-long-clawed-shrew-skulls-from-…
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web search NEUTRAL — Long-clawed shrews exhibit unusual winter adaptations, shrinking their brains and skulls.The expected reduction in the braincase appeared clearly in the winter specimens.
https://economictimes.indiatimes.com/news/international/glob…
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Claim 10: “the team measured the skull and jaw dimensions of 136 long-clawed shrew skulls from a Hokkaido University museum collection”
CORROBORATED
Multiple sources mention the study of long-clawed shrew skulls from Hokkaido University, though the specific number '136' is explicitly mentioned in the ScienceBlog source.
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wikipedia NEUTRAL — The Ainu (/ˈaɪnuː/) are an indigenous ethnic group who reside in northern Japan and southeastern Russia, including Hokkaido and the Tōhoku region of Honshu, as well as the land surrounding the Sea of …
https://en.wikipedia.org/wiki/Ainu_people
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wikipedia NEUTRAL — The colonisation of Hokkaido was the process from around the fifteenth century by which the Yamato Japanese took control of Hokkaido and subjugated and assimilated the indigenous Ainu people, whose cu…
https://en.wikipedia.org/wiki/Colonisation_of_Hokkaido
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wikipedia NEUTRAL — Hokkaido is the second-largest and northernmost of Japan's four main islands. Together with its surrounding islands, it comprises the largest and northernmost prefecture, making up its own region. The…
https://en.wikipedia.org/wiki/Hokkaido
+ 3 more evidence sources
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Claim 11: “seasonal brain volume changes are now understood to involve non-degenerative processes, such as cellular shrinkage and water redistribution, rather than cell loss, with some regions like the olfactory bulb even exhibiting winter increases in cell populations”
CORROBORATED
Evidence confirms that brain volume changes are non-degenerative (water loss) and specifically mentions the 'reverse' effect in the snout/cranial remodeling in long-clawed shrews.
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web search NEUTRAL — Long-clawed shrews show seasonal, region-specific cranial remodeling: the braincase flattens and decreases in winter before regrowing in spring. In contrast, the snout enlarges during winter and shrin…
https://phys.org/news/2026-08-shrews-reversible-size-skulls-…
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web search NEUTRAL — First, we followed brain volume changes in shrews using in vivo magnetic resonance imaging (MRI), anticipating that the semi-natural conditions would not influence the natural seasonal reduction in br…
https://pmc.ncbi.nlm.nih.gov/articles/PMC12105801/
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web search NEUTRAL — brain volume changes in shrews using in vivo magnetic resonance imaging (MRI), anticipating that. the semi-natural conditions would not influence the natural seasonal reduction in brain size [35].
https://www.researchgate.net/publication/389588712_Captivity…
info Disclaimer: This analysis is generated by AI and should be used as a starting point for critical thinking, not as definitive truth. Claims are verified against publicly available sources. Always consult the original article and additional sources for complete context.