Friday, January 31, 2025

Are dogs really bred for function? New Chapman study challenges the assumptions about certain breeds

Chapman University

Dog Skull — image:
canine skull illustrating morphological variations analyzed in the study. Findings challenge traditional assumptions of performance specialization resulting from selective breeding
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Credit: Worden Photography for Chapman University

Since their domestication millennia ago, dogs have been man’s best friend, and aside from friendship, centuries of selective breeding have tailored them for tasks like herding, hunting and guarding — or so we thought.

Now, the results of a new study challenge the prevailing belief that some breeds are inherently superior at specific tasks, based on their skull morphology. The study, led by Nicholas Hebdon and Lindsay Waldrop and published in Science Advances on January 29, used advanced 3D reconstruction techniques to analyze 117 skulls from 40 domestic dog breeds and 18 wild canid species. The researchers found substantial overlap in skull shapes across breeds and functional categories, but no clear evidence that breeds selected for bite work or scent work have developed distinct morphological traits that enhance these abilities. This suggests that humans have been breeding dogs primarily for preferred visible traits, and that other factors like individual personality affect dogs’ performance of tasks.

“In the past 200 years, humans have created hundreds of dog breeds that look really different and are pretty specialized at some tasks like herding, protecting, and detecting odors. We have assumed that these dogs look different because they are structurally specialized at these tasks, but our study shows that, at least for their skulls, they are not specialized for tasks that involve the skull, such as biting tasks and scent work,” notes Waldrop, who is an assistant professor of biological sciences at Chapman University.

The study examined dog breeds commonly used for tasks like bite work and scent work, such as those in law enforcement and military programs, where dogs are trained for patrol and detection. Researchers used advanced methods, including 3D skull analysis to compare breeds across various functional groups, as defined by organizations like the American Kennel Club (AKC) and the United Kennel Club (UKC).

The results showed that domesticated dog breeds exhibit exceptional diversity in their skull shapes, but have high overlap among the parts of the skulls that correspond with functional tasks. This indicates that specific breeds are not as morphologically specialized for such tasks as previously thought. For instance, bite-force measurements did not show any significant differences between breeds purpose-bred for bite work and those not.

“There are many news stories about dogs attacking people badly and often there are specific breeds that are targets of this reporting (such as pit bulls). Some people claim that these dogs will bite harder than other dogs of the same size, or they have special features like “locking jaws” that make them especially dangerous to people. Our study shows that this is simply not true; dogs bred to bite things aren’t structurally different than dogs that have bred to do other things,” said Waldrop.

Similarly, breeds selected for scent work did not demonstrate significantly enhanced olfactory morphology compared to other breeds. The lone group that showed distinct skull morphology was brachycephalic breeds (e.g., bulldogs), which are characterized by their shortened snouts, but this feature is not tied to functional specialization. Instead, human aesthetic preferences have played a larger role in shaping dog morphology.

According to lead author Nicholas Hebron, who completed the work as a postdoctoral research associate at Chapman University, “I was most surprised by the overall similarity we see in most of the dog skulls. Humans have done so much breeding work to alter the visual appearance of these animals that I honestly expected to see really marked groupings of some kind and we really didn't see much of that.”

However, researchers found that domesticated dog breeds’ morphologies differed greatly from wild canids, such as wolves and foxes, which tend to have skull shapes that align more closely with their natural functional needs. Wolves and foxes tend to possess elongated snouts relative to their cranial length, which is a typical feature of species that rely on keen senses like smell. Undomesticated animals, particularly wolves, show skull morphologies that reflect evolutionary adaptations for hunting and scent work, which contrasts with the lack of strong morphological specialization in domesticated breeds. Interestingly, foxes' skull shapes overlap significantly with some domestic dogs, particularly terrier breeds, which were historically bred for pest control, suggesting functional similarities in skull structure for small prey pursuit.

While these results run counter to the popular notion that purpose-bred dogs are better at biting or scenting than those not bred for that purpose, they suggest that observable behavior traits are associated with performance, rather than morphological traits. Recent research suggests that many breed-associated behaviors are partially heritable. This has important implications for how dogs are bred and selected for specific tasks in areas such as law enforcement and search and rescue — behavioral traits and individual trainability may be more important determinants of performance.

Researcher Lindsay Waldrop with her dog. Findings challenge traditional assumptions of performance specialization resulting from selective breeding

Credit

Worden Photography for Chapman University

Journal

Science Advances

DOI

10.1126/sciadv.adq9590

Method of Research

Meta-analysis

Subject of Research

Animals

Article Title

Dog skull shape challenges assumptions of performance specialization from selective breeding

Article Publication Date

29-Jan-2025

FEMICIDE

New national study finds homicide and suicide is the #1 cause of maternal death in the U.S.

Society for Maternal-Fetal Medicine

Denver, Colo. -- In the medical community, research has traditionally focused on how to prevent and treat the leading medical causes of maternal mortality, which include bleeding, infection, hypertension, and cardiovascular disease. However, new research reveals deaths by homicide and suicide are the leading causes of maternal death in the United States.

In a study to be presented today at the Society for Maternal-Fetal Medicine’s (SMFM) annual meeting, The Pregnancy Meeting™, researchers will unveil findings that suggest that nationwide more pregnant people die from homicide and suicide than any medical cause, and that firearm legislation is associated with fewer maternal deaths.

Researchers reviewed CDC data from 2005-2022 on the deaths of pregnant people and people within the first 42 postpartum days ranging in age from 15-44, making this the most extensive study of a national database on maternal deaths. Researchers note that past studies either have been done at the state level or use data from multiple databases, which can result in inconsistencies in how information is reported.

Findings show that over the 18-year period, 20,421 pregnant people died. Of that number, 11 percent (2,293) of deaths were due to homicide and suicide. More specifically, 61 percent (1,407) of those deaths were the result of homicides and 39 percent (886) were the result of death by suicide. Fifty-five percent of violent deaths (1,261) involved firearms.

“Many people are surprised when they hear that violence is the leading cause of death in pregnancy,” says the study’s lead author Hooman Azad, MD, MPH, a fourth-year resident in the Department of Obstetrics & Gynecology at New York’s Columbia University Irving Medical Center. “Right now, the definition of maternal mortality does not include death by homicide. I’m not sure this is correct — being pregnant or postpartum significantly increases the risk of death by homicide, and more pregnant women die of violence than any individual medical cause. Part of the reason violence is not recognized as the leading cause of death during pregnancy is because we don’t include homicide and suicide in the definition of maternal mortality.”

The study also found that Black birthing people, ages 18-24, experience death due to homicide at a rate of almost eight deaths per 100,000, nearly four times the national average.

Researchers also looked at the impact of the passage of firearm legislation on maternal deaths and found a 20-30 percent reduction in firearm deaths and firearm homicides in states that had enacted firearm legislation.

“There’s a misconception that most maternal deaths happen in hospitals or healthcare settings, and that’s simply not the case,” says another study author Mary D’Alton, MD, a maternal-fetal medicine subspecialist and chair of the Department of Obstetrics & Gynecology and professor of Obstetrics & Gynecology at Columbia University Irving Medical Center. D’Alton also serves as director of services at the Sloane Hospital for Women at New York-Presbyterian. “We need more education about this serious national issue so we can begin to take steps to address it as clinicians as well as at the policy level.”

The abstract was published in the January 2025 issue of Pregnancy, a new open-access journal and the first official journal for the Society for Maternal-Fetal Medicine.

Additional news releases about select SMFM research being presented are posted on AAAS’s EurekAlert (subscription needed) approximately one week in advance of embargo lifting. Embargoes lift on the date and start time of the abstract presentation.

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About the Society for Maternal-Fetal Medicine

he Society for Maternal-Fetal Medicine (SMFM), founded in 1977, is the medical professional society for obstetricians who have additional training in high-risk, complicated pregnancies. SMFM represents more than 7,000 members who care for high-risk pregnant people and provides education, promotes research, and engages in advocacy to reduce disparities and optimize the health of high-risk pregnant people and their families. SMFM and its members are dedicated to optimizing maternal and fetal outcomes and assuring medically appropriate treatment options are available to all patients. For more information, visit SMFM.org and connect with the organization on Facebook, X, and Instagram. For the latest 2025 Annual Meeting news and updates, follow the hashtag #SMFM25.

Genomic evidence confirms white shark liver is on Australian killer whales' menu

Flinders University

For the first time, DNA evidence has confirmed killer whales in Australia hunted a white shark for its liver.

Based on DNA analysis from the bite wounds on the carcass of a large white shark washed ashore near Portland in Victoria in 2023, the Flinders University-led study identified that killer whales were responsible for consuming the mid-section containing the nutritionally rich liver.

Around the world, killer whales (Orcinus orca) have been observed preying on various shark species including white sharks (Carcharodon carcharias) – as previously documented in California and South Africa.

The discovery of a 4.7 metre white shark missing its liver on a beach in southeastern Australia offered a rare opportunity to analyse distinctive bite wounds and unravel the predator’s identity.

“The liver, digestive and reproductive organs were missing, and there were four distinctive bite wounds, one of which was characteristic of liver extraction by killer whale, similar to what has been observed in South Africa,” says lead author Isabella Reeves, a PhD candidate with Flinders University’s Southern Shark Ecology Group and the West Australian Cetacean Research Centre (CETREC).

“Swabs were taken from bite wounds on the white shark and sequenced for remnant genetic material from the shark’s predator. We were able to confirm the presence of killer whale DNA in the primary bite area, while the other three wounds revealed DNA from scavenging broadnose sevengill sharks.

“These findings provide compelling evidence of killer whale predation on white sharks in Australian waters, with a strong indication of selective liver consumption. This suggests that such predation events may be more widespread and prevalent across the globe than previously believed.”

The study, published in Ecology and Evolution, used wildlife forensic techniques to confirm killer whales were responsible for excising and consuming the liver from the white shark. Civilian bystanders had witnessed several killer whales, including locally known individuals called ‘Bent Tip’ and ‘Ripple, catching a large prey in Bridgewater Bay two days before the white shark carcass washed ashore.

The beached large white shark carcass was collected by state government fisheries officers for investigation.

Killer whales in Australia have occasionally recorded preying on various shark species, including blue shark (Prionace glauca), porbeagle (Lamna nasus), shortfin mako (Isurus oxyrinchus), ground sharks (most likely school shark, Galeorhinus galeus), and tiger shark (Galeocerdo cuvier). But white shark liver consumption had yet to be observed in Australia – despite numerous reports of such behaviour in California and by notorious duo ‘Port’ and ‘Starboard’ in South Africa.

Several interactions between killer whales and white sharks have been reported in Australia, including at least one suspected kill at the Neptune Islands Group Marine Park in South Australia in February 2015. On that occasion, an oil slick indicative of a successful predation was observed following the interaction, although no carcass was recovered to confirm the kill.

Rhodes University (South Africa) marine biologist, Dr Alison Towner, an author in the study, says similar killer whale predation on white sharks have led to disruptions in local shark populations in both South Africa and California. “However direct observations of these interactions remain rare and their frequency is poorly understood,” she says.

Senior author, Flinders adjunct Associate Professor Adam Miller, says: "We don’t know how frequently these events occurred in Australian waters and therefore how significant these findings are," says Associate Professor Miller, who is also a senior ecologist with Cesar Australia.

"Evidence suggests that the white sharks being displaced or directly killed as a result of the killer whale predation in South Africa has led to cascading shifts in the wider marine ecosystem.

"We know that white sharks are key regulators of ecosystem structure and functions, so it's very important we preserve these top predators. Therefore, it is important that we keep a tab on these types of interactions in Australian waters where possible.”

Another author, Flinders University Research Fellow Dr Lauren Meyer, adds, “This study also provides DNA evidence that scavenging is facilitated by killer whales’ tissue selection, whereby the liver and internal organs are consumed, but much of the carcass remains as a nutrient source benefiting local ecosystems.”

The ‘Nature Notes’ article ‘Genetic Evidence of Killer Whale Predation on White Sharks in Australia’ (2025) by Isabella MM Reeves, Andrew R Weeks, Alison V Towner, Rachael Impey, Jessica J Fish, Zach SR Clark, Paul A Butcher, Lauren Meyer, David M Donnelly, Charlie Huveneers, Nicky Hudson and Adam D Miller has been published in Ecology and Evolution (Wiley) First published: 27 January 2025 https://doi.org/10.1002/ece3.70786

The study was supported by experts from Victoria’s EnviroDNA, The University of Melbourne, Rhodes University in South Africa, the South African International Maritime Institute, Deakin University’s EcoGenetics Lab, the NSW Department of Primary Industries National Marine Science Centre, Killer Whales Australia and Dolphin Research Institute in Victoria and the Gunditj Mirring Traditional Owners Aboriginal Corporation, Victoria.

Images & captions: https://drive.google.com/drive/folders/14dzGYj5_lzHyD2jh0ADnA_AcnuKaNGtm?usp=drive_link

Acknowledgements: Researchers acknowledge the Traditional Owners of the land on which this research was conducted, the Gunditjmara and Wurundjeri peoples. Thanks to Cameron McCallum and John Melis from the Victorian Fisheries Authority and the Gunditj Mirring Traditional Owner Aboriginal Corporation. The carcass is now held by Museums Victoria.

Infographic of Reeves et al. 2025 study based on using DNA to identify that killer whales killed white shark carcass for liver.