Dog bites are one of the most common injuries in the United States, yet most research has focused on a deceptively simple question: how often do they happen? A new study shifts the focus to a more consequential one — when bites do happen, what makes them worse? Analyzing 1,116 reported dog bite incidents from 2019 to 2021 in Southern Colorado, researchers Michael D. Briscoe of Colorado State University Pueblo and Shay Reszka of Colorado Mesa University found that the sex of the biting dog and the age of the human victim are strongly linked to how severe the resulting injury becomes. Their findings, published in the journal Discover Animals, challenge several long-standing assumptions about which dogs are most dangerous and offer a data-driven roadmap for reducing the worst outcomes of human-animal conflict.
The scale of the problem is enormous. The American Veterinary Medical Association estimates that more than 4.5 million people in the United States are bitten by dogs every year, and the Centers for Disease Control and Prevention reports that roughly 20 percent of those bites require medical attention. Beyond the human toll, the economic burden is substantial: a 1999 estimate placed the annual cost of medical care for dog bite victims between 235.6 and 253.7 million dollars, a figure that rises to between roughly 471.5 and 507.7 million dollars when adjusted to 2026 dollars. And victims are not only human. Dogs bite other dogs, and cats — because of their small size — can suffer devastating injuries from the same bite that would leave a human moderately hurt.
The researchers drew their data from the Humane Society of the Pikes Peak Region (HSPPR), the agency responsible for animal law enforcement in El Paso and Pueblo counties, home to Colorado Springs and Pueblo. HSPPR responds to around 2,300 calls each year about aggressive companion animals and publishes reported bites on a public “Bite Blotter.” Each victim in an incident receives a separate record, and HSPPR classifies severity in three tiers: moderate, meaning one deep puncture or multiple moderately deep punctures and lacerations; severe, meaning multiple punctures, deep gashes, serious bodily injury, or permanent disfigurement; and fatal, meaning the death of a human or domestic animal. The study region is also demographically diverse, with El Paso County’s 757,040 residents contrasting with Pueblo County’s 169,277, roughly half the bachelor’s degree attainment and double the poverty rate, which the authors argue improves the generalizability of their findings.
The analytical approach was deliberately more nuanced than most prior work. Instead of treating bite outcomes as a simple yes-or-no event, the researchers used ordered logistic regression on the full sample of human, dog, and cat victims, with severity as a three-level ordinal outcome. They tested the sex of the biting dog, whether the dog was spayed or neutered, an interaction between those two variables, victim species, and the location of the bite on the victim’s body. A Brant test confirmed the proportional odds assumption held for the model. For the human-only subsample, where no bites proved fatal, severity became a binary outcome of moderate versus severe, and the team turned to logistic regression, adding victim age and a quadratic age term to probe for nonlinear effects.
The first major result was a surprise. Across the full sample, neither the sex of the biting dog nor its alteration status showed any statistically significant association with bite severity, and the models’ near-zero pseudo R-squared values confirmed that these variables were poor predictors of how bad a bite would be. What did matter enormously was the species of the victim. Compared with cat victims, dog victims had 92.8 percent lower odds of a more severe bite (odds ratio 0.072), and human victims fared even better, with odds 97.9 percent lower (odds ratio 0.021). The authors caution that reporting bias likely inflates this gap: a moderate bite to a cat may simply go unnoticed or unreported, while the same injury to a person almost certainly reaches animal control. Bite location also mattered — injuries to the torso or to multiple areas of the body were roughly three times more likely to be severe than bites to the hands, paws, arms, or front legs.
When the analysis narrowed to human victims only, a clearer picture emerged. Bites from male dogs carried 81.5 percent higher odds of being severe rather than moderate compared with bites from female dogs (odds ratio 1.815), an association that held consistently across every model specification. Intriguingly, whether the dog was neutered made no difference to severity — a finding that complicates the widespread assumption that spaying and neutering uniformly reduce bite risk. Prior research has documented that intact male dogs bite more often, with one study reporting an incidence rate of 55.1 bites per 1,000 unneutered males versus 3.0 per 1,000 spayed females, and testosterone described as a behavior modulator that makes dogs react more quickly, more intensely, and for longer. But frequency and severity, this study suggests, are governed by different dynamics.
Perhaps the study’s most striking discovery concerns victim age. Rather than a simple linear decline in risk with each passing year, the relationship between age and bite severity turned out to be distinctly U-shaped. Each additional year of age was associated with a 5.6 percent decrease in the odds of a severe bite (odds ratio 0.944), while the quadratic term was also highly significant, indicating the risk curve bends back upward. The turning point sits at just over 47 years old: before that age, risk of severe injury falls as people get older; after it, risk climbs again. A sensitivity analysis excluding the oldest one percent of victims — those over 86 — confirmed the pattern was not an artifact of a few extreme cases. Even after controlling for bite location, the U-shaped age effect remained significant, suggesting that the very young and the elderly are intrinsically more vulnerable, not merely more likely to be bitten in dangerous places like the head and neck.
The authors frame these findings through a harm reduction lens, an approach borrowed from public health strategies that accept a behavior will persist and aim instead to blunt its worst consequences. Dog bites, they argue, will never be eliminated as long as humans keep companion animals, so the priority should be preventing the bites that cause the most damage. This matters legally as well as medically: under Colorado law, euthanasia becomes mandatory for dogs whose bites cause serious bodily injury or death, whereas France has adopted a more rehabilitative model requiring veterinary evaluation of biting dogs within 15 days to identify triggers and prevent recurrence. In Pueblo, a new ordinance creating a “potentially dangerous animal” category now gives enforcement officers flexibility to intervene before minor incidents escalate into tragic ones.
The practical implications are clear. Guardians, shelters, and adoption counselors should pay particular attention to households with young children and elderly members, the two groups at the highest risk of severe injury, and supervision of dogs around these vulnerable populations should be treated as a community responsibility rather than a burden placed on individual owners. The authors also recommend that policymakers consider making responsible pet ownership education mandatory at the point of adoption or purchase, rather than only after a court order following an incident. At the same time, the study acknowledges its limits: the administrative data lacked information on breed, dog size, victim sex, and race, and many bites — especially minor ones and those involving animal victims — go unreported, sometimes because people fear that reporting could doom a dog to euthanasia. Biting, the researchers emphasize, is a natural behavior with many motivations, from fear to territoriality to predatory instinct, and understanding the patterns behind the most severe outcomes is the first step toward a world where fewer bites turn tragic.
Subject of Research: Predictors of dog bite injury severity among human, dog, and cat victims in Southern Colorado
Article Title: Predictors of reported dog bite injury severity among human, dog, and cat victims in Southern Colorado
Article References: Briscoe, M. D., & Reszka, S. (2026). Predictors of reported dog bite injury severity among human, dog, and cat victims in Southern Colorado. Discover Animals, 3(1), Article 97. https://doi.org/10.1007/s44338-026-00256-1
Image Credits: AI Generated
DOI: 10.1007/s44338-026-00256-1
Keywords: dog bites, injury severity, public health, harm reduction, animal behavior, Colorado, logistic regression, victim age, neutering, animal law enforcement, veterinary science, risk factors
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William Thompson. (September 26, 2026). Male Dogs and the Very Young and Old Face Higher Risk of Severe Bites, Colorado Study Finds. Scienmag. https://scienmag.com/male-dogs-and-the-very-young-and-old-face-higher-risk-of-severe-bites-colorado-study-finds/
William Thompson. “Male Dogs and the Very Young and Old Face Higher Risk of Severe Bites, Colorado Study Finds.” Scienmag, 26 September 2026, https://scienmag.com/male-dogs-and-the-very-young-and-old-face-higher-risk-of-severe-bites-colorado-study-finds/. Accessed 26 September 2026.
William Thompson. “Male Dogs and the Very Young and Old Face Higher Risk of Severe Bites, Colorado Study Finds.” Scienmag. September 26, 2026. https://scienmag.com/male-dogs-and-the-very-young-and-old-face-higher-risk-of-severe-bites-colorado-study-finds/
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Tags: age-related vulnerability to dog bitesanalysis of dog bite incidents in ColoradoAnimal Behavioranimal law enforcementcharacteristics of high-risk dog bite casesColoradodata-driven insights into dog bite severitydog bite severity risk factorsdog bitesepidemiology of severe dog bites in the USfactors influencing dog bite injury severityharm reductionhuman-animal conflict and injury preventionimpact of dog sex on bite outcomesinjury severitylogistic regressionmale dogs and vulnerable human age groupsneuteringPublic healthpublic health implications of dog bite risksresearch on dog-human interaction and bite severityrisk factorsveterinary sciencevictim age
