It turns out that one of the smallest dog breeds, the chihuahua, is part wild coyote, according to recently published genetic research. The chihuahua breed originated in Mexico but is now a popular canine companion worldwide.
Author
- Jacqueline Boyd
Senior Lecturer in Animal Science, Nottingham Trent University
Coyote genes may have been introduced into ancestors of the chihuahua accidentally. It may also be a result of deliberate attempts to cross the two animals – perhaps many generations ago.
Coyotes are a wild canine species, slightly smaller than the grey wolf and native to North America. The presence of coyote genes in the much smaller chihuahua – among the most popular dogs in the UK and the US – highlights the incredible diversity of domestic dogs and their varied histories.
Coyotes are untamed and territorial, while anyone who has lived with a chihuahua knows that their small bodies house big canine personalities.
Chihuahuas are the archetypal “small but mighty” dogs: bold, independent, agile, but also capable of obedience. Small, sedentary lapdogs they are not. These findings might partly explain why.
The recent study explored ancient genetic signatures in dog and human genomes to validate the effectiveness of new genetic techniques. The genome is the full complement of DNA in living cells.
The researchers demonstrated their methods on dog breeds with links to the Americas, such as the chihuahua and another Mexican breed, the xoloitzcuintli (often shortened to xolo). The xolo is typically characterised by a lack of hair and an often aloof
personality.
Many dogs in the Americas today are descended from European breeds, an
outcome of colonisation from the 15th century onwards. However, previous research showed that the chihuahua and xolo preserve a small amount of ancestry – 4% in the
chihuahua and 3% in the xolo – from pre-contact dogs, those that lived in the
Americas before Europeans arrived.
Genetic analysis of the xolo in the recent study suggests that
European and pre-Columbian dogs were mixing around 1700. This aligns with evidence suggesting that Europeans and Indigenous populations mixed around the same time in early Mexico.
Reconstructing origins
Researchers previously found evidence of coyote ancestry in DNA from the remains of ancient domestic dogs from the Americas. It’s a reminder that dogs are not that far removed from other canid species, and can breed with them successfully.
Wild coyotes and wolves have been found to hybridise naturally , especially in geographical areas where “wolf-like” behavioural traits are beneficial. There was even a recent report of a dog-fox hybrid being identified in Brazil .
It remains unclear when exactly the coyote genes entered the chihuahua lineage. The precise histories of different dog breeds are hard to reconstruct because detailed documentary evidence is often lacking.
So how did the chihuahua end up being so small, despite those coyote genes? This question should be seen through the lens of selective breeding, where humans choose different dogs to breed from based on characteristics they prefer.
Genetic analysis reveals that almost all small dog breeds share a mutation in the insulin like growth factor 1 (IGF1) gene, which affects cell growth and thus body size . Selection for small dogs with this mutation appears to have occurred very early in dog domestication .
There is some evidence for the presence of diminutive dogs among pre-contact Mesoamerican cultures , but how these relate to chihuahuas is unknown.
Extreme variation
Some dogs such as the Czechoslovakian wolfdog look visibly
more like their wild and ancestral canid counterparts , such as the grey wolf. They have pricked ears , muscular, athletic bodies and coats that provide camouflage and protection from environmental extremes.
Other dogs show extreme variation: exaggerations such as long backs or short legs. In some cases, these physical characteristics come with significant consequences for health and wellbeing .
Overall body size is particularly variable in dogs, with a 40-fold difference across different breeds and types . Imagine the diminutive chihuahua standing next to an imposing Great Dane , for example.
There are also important differences in behaviour . If you want to live
harmoniously with a dog, or train or work a dog in a specific activity, this is important to acknowledge. Indeed, meeting an individual dog’s physical, psychological and emotional needs is essential for both dog and human wellbeing, as well as training success .
As with appearance, natural and human-driven selection have combined to influence these traits. This has produced generations of dogs with specific behavioural characteristics .
The dog was one of the earliest animals to be domesticated by humans – the
earliest examples are more than 15,000 years old . They are also one of the most successful domesticated species .
Dogs are found on every continent except for Antarctica, and the global dog population is thought to number between 700 million and 1 billion .
They exist either embedded within human society, or living on the fringes of it .
Throughout history, natural selection on dogs with characteristics that confer survival advantages will have occurred. At the same time, humans will have selected individual dogs based for desired attributes, leading to the breed development and classifications that we see across the world.
As well as furthering our capacity to explore genetic ancestry of species, the latest study adds detail to our understanding of how and when the domestic dog evolved, and became so diverse.
It might also mean we think less about the “wolf in our living rooms”, and more about the “coyote in our chihuahuas”.
