Two biologists seem to have figured out why large dogs seem to live shorter than smaller breeds. And it has nothing to do with the aging of these animals, but with their likelihood of getting cancer.
This is not new : large dogs live on average shorter than smaller breeds. A Yorkshire or a Dachshund can live up to 16 years, a Chihuahua up to 20 years. Larger dog breeds, such as the Saint Bernard, Mastiff or Newfoundland dog, generally do not live longer than 10 years. Researchers from Australia's University of Adelaide think they know why. For a new study published in The American Naturalist, two biologists looked at the main reasons that could explain these striking differences in life expectancy. For this, they analyzed the common causes of death in 164 breeds of dogs of different sizes. And one stands out particularly in big dogs : cancer.
"When we analyzed these datasets, we found that large dogs were more likely to die from cancer at a younger age than small dogs," the study's lead author told the Daily Mail. Doctor Jack da Silva. "Large dogs don't necessarily age faster than smaller breeds, but research has shown that as average breed body weight increases, cancer rates also increase."
Selective breeding of large dogs in question
According to the biologist, the natural defenses against cancer of these dog breeds have not kept pace, as selective breeding has produced ever more large dogs. This would be an evolutionary lag, given how quickly kennels shaped the appearance of big dogs over time. "Most of the approximately 400 dog breeds we know today were only established in the last 200 years," says Jack da Silva. But genetics takes time, unlike the fashions and criteria of humans, who wanted bigger animals for hunting, herding cattle, or for competitions. Large dogs thus reached extreme sizes faster than their natural evolution would have allowed. And their defenses against disease would not have evolved proportionally.
The results of this study match a theory established by biologist Thomas Kirkwood in 1977 that animals optimize their energy use throughout their lives, reports Newsweek magazine. So if they invest a lot of their energy in reproduction, early in life, then they will produce a large number of offspring, but will not invest that energy in defending against cancer or repairing damage caused by cancer diseases to their cells and their DNA. For large dogs to manage to live on average a few more years, they would therefore have to have smaller litters, and for breeding to focus on selecting animals that live longer. Over time, Cane Corsos, Leonbergers or Great Danes could end up evolving to regain their defenses against cancer.
Why Small Dogs Live Longer Than Big Dogs ?
Introduction
The phenomenon of small dogs living longer than their larger counterparts has long piqued the interest of veterinarians, researchers, and pet owners alike. While genetics, environment, and lifestyle play significant roles in a dog's lifespan, several factors contribute to the disparity in longevity between small and large dog breeds. In this article, we will explore the various reasons behind this intriguing phenomenon.
1. Metabolic Rate
One of the primary reasons small dogs tend to live longer than large dogs is their metabolic rate. Smaller breeds have faster metabolisms, which means they process nutrients and energy more efficiently. This efficiency often leads to less strain on their organs and body systems, reducing the risk of various health issues associated with aging. In contrast, larger dogs have slower metabolisms, putting more stress on their organs and contributing to a higher risk of diseases, particularly those related to obesity.
2. Size-Related Health Issues
Large dog breeds are predisposed to specific health issues linked to their size. Joint problems, such as hip dysplasia and osteoarthritis, are more common in larger dogs due to the pressure exerted on their joints. Moreover, large dogs are more susceptible to cardiac issues, like dilated cardiomyopathy, owing to the strain on their hearts to support their larger bodies. These health concerns can significantly impact the lifespan of larger breeds, often reducing their life expectancy.
3. Developmental Stages
The developmental stages of small and large dog breeds also play a role in their lifespan discrepancy. Smaller breeds tend to mature faster, reaching adulthood at an earlier age compared to larger breeds. This accelerated development can translate to a longer period of being in prime health, while larger breeds may take longer to reach their prime and spend a proportionally shorter time in their healthiest state.
4. Growth Rates and Cellular Replication
The growth rates of small and large dogs differ significantly. Smaller breeds generally experience slower growth rates, while larger breeds undergo rapid growth during their early stages of life. This rapid growth can lead to an increased risk of developmental abnormalities and orthopedic issues in large dogs. Additionally, the higher rate of cellular replication during growth phases may contribute to an accelerated aging process, leading to a shorter lifespan.
5. Evolutionary Factors
The varying lifespans of small and large dog breeds can be linked to their evolutionary origins. Smaller dog breeds have historically been more adaptable and resilient, surviving in diverse environments and harsh conditions. Over time, these characteristics may have been selected for, resulting in a more robust genetic pool and increased longevity. In contrast, larger dog breeds were often bred for specific purposes like hunting, guarding, or pulling, leading to a narrower gene pool and increased susceptibility to certain health issues.
6. Cancer Susceptibility
Cancer is a significant factor affecting the longevity of dogs, and research has shown that larger breeds tend to have higher cancer rates compared to smaller breeds. It is believed that the accelerated growth and larger number of cells in large dogs may increase the likelihood of genetic mutations, leading to a higher risk of cancer development. Moreover, larger breeds have a higher chance of developing aggressive forms of cancer, further impacting their life expectancy.
7. Environmental Factors
Environmental factors also contribute to the lifespan discrepancy between small and large dogs. Smaller dogs, being more compact and less weighty, are generally better suited to living in confined spaces, like apartments, where larger dogs might struggle. The living environment can significantly impact a dog's overall health and well-being, affecting their longevity.
Conclusion
While genetics, environment, and lifestyle all influence a dog's lifespan, the fact remains that small dogs tend to live longer than their larger counterparts. Their faster metabolic rates, reduced size-related health issues, and genetic adaptability are some of the key factors contributing to this phenomenon. Understanding these factors can help pet owners make informed decisions about their dog's health, nutrition, and overall care, ensuring a longer and healthier life for their beloved companions.
Comments
Post a Comment