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Cacomixtles in a changing world

Written by Madeleine E. Zuercher, Ph.D. candidate - Grether Lab, Department of Ecology and Evolutionary Biology, UCLA

Cacomixtles in a changing world

The cacomixtle

The Americas are home to incredibly diverse landscapes which host abundant biodiversity. However, human activities are altering ecosystems in drastic ways and impacting the wildlife that inhabit these landscapes. In response to these changes, it is thought that species can either move, adapt, or die. One species that has been challenged by global change is the charming, enigmatic cacomixtle.

The cacomixtle goes by many names: ringtail, bassarisk, ringtail cat, miner’s cat. The name “cacomixtle'' is from the Nahuatl word tlahcomiztli, which means “half-cat,” and its Latin name Bassariscus astutus means “little clever fox,” though it is actually more closely related to raccoons than cats or foxes. Like raccoons, the cacomixtle has a striped tail and is very agile. Its ankles can rotate 180 degrees, which is a special adaptation for swiftly climbing down trees and boulders. They are incredibly intelligent and playful, even learning to open zippers and using campers’ tents as slides.

The cacomixtle’s range spans throughout Mexico and the southwestern United States, where they live in deserts and forests. While cacomixtles are the state mammal of Arizona and are protected in California, we are still lacking critical information about its natural history. The cacomixtle is elusive, making it difficult to study, and has not been properly assessed to assign it a conservation status. Despite these obstacles, scientists know cacomixtle populations are struggling. In each part of its range, the cacomixtle suffers different consequences of human activities and adapts to these challenges in unique ways. Studying these adaptations gives us insight into what the future holds for our treasured wildlife.


Development of urban, suburban, and agricultural areas has degraded the habitats cacomixtles depend on. Cacomixtles have been pushed out of southern California’s vast cityscapes, and even in the less developed areas roads are a major threat. When they attempt to cross roads, they are likely to be hit by a car and die. Research led by the San Diego Zoo Wildlife Alliance is investigating how roads affect the movement of cacomixtles and if certain demographic groups are particularly at risk.

If they do not cross roads, populations become disconnected from other populations. This is likely the case for the cacomixtle population of the Santa Monica Mountains. Their carcasses are found in mountainous areas north of Malibu, though they are rarely detected in the more developed areas near the large US-101 freeway. This means that the population is likely genetically sequestered. In genomics, this type of isolation indicates that the population is susceptible to what we call inbreeding depression, or the development of dangerous mutations. Inbreeding depression has been a major threat to Florida panthers. After being isolated from other panther populations with higher genetic diversity, Florida panthers developed issues including low fertility and heart defects. By introducing panthers from other regions to Florida, conservationists were able to increase the genetic diversity of the population and save the panthers.

Conservationists around the world are working to solve the problems created by habitat degradation and isolation. One solution currently being implemented near Los Angeles is the creation of wildlife corridors above freeways. The new Liberty Canyon crossing will allow wildlife to safely cross over between the northern and southern parts of the US-101 freeway. The bridge is expected to help populations of mountain lions connect to sustain genetic diversity and access resources. It will likely facilitate the crossing of other species like the cacomixtle. However, for a small species that is not able to safely cross roads much smaller than the US-101 freeway, this effort might not be enough to prevent high road mortalities. Further, the damaging effects of genetic isolation may have already taken hold. Scientists and the local community eagerly await the completion of the crossing. With promising outcomes from other bridges built across the world, scientists remain hopeful that the crossing will help the wildlife community in the Santa Monica Mountains.

Mexico City

Near the southern border of the cacomixtle’s range, urban expansion has led to a different outcome. In Mexico City, cacomixtles are abundant. They eat pet food, dig into garbage, and have even crept into peoples’ beds during the night. While some residents adore the cacomixtles, others see them as pests; they leave out poisoned food and trap the animals to prevent them from interfering with their homes. Generally, the people of Mexico City are affectionate towards the curious cacomixtles. However, just because cacomixtles are abundant here does not mean they are thriving.

Cacomixtles are generalists, which means that they consume a variety of food items. Depending on their habitat, their diets include rodents, birds, insects, scorpions, fruits, seeds, and leaves. While they may find abundant food in urban areas, this food is likely much different than they would find in their natural habitat. Consuming food that contains high levels of fats, sugars, sodium, and other potentially harmful ingredients can affect their digestion and overall health. Some foods can even alter DNA methylation, which means that the animal’s body expresses different genes than it would naturally. Changes in DNA methylation can lead to various diseases, including cancers. Food poisoning has not yet produced any detectable health consequences for the cacomixtles of Mexico City, though monitoring their health is critical.

Mexico City is a unique example of cacomixtles surviving in extremely urban landscapes. This begs the question, why do cacomixtles not inhabit all cities? The answer may lie in their genetics. If individuals are genetically predisposed to neophilia (tendency to explore new things) and boldness (tendency to engage in risky behaviors), those animals might succeed better in urban landscapes and pass their genes on to the next generation. In evolutionary biology, this is called natural selection. If this has occurred, we would expect urban cacomixtles to be genetically distinct from the rest of the species; this research has not yet been done. The reason for urban success in Mexico City may actually have little to do with genetics, and more to do with the rest of the mammal community. For example, cacomixtles in Los Angeles would be possible prey for the coyotes, mountain lions, and bobcats that live in and around the city. Without big teeth, big claws, or other deterrents, they are very vulnerable to predation. There are no such predators in Mexico City, which has possibly allowed the cacomixtle to flourish there. Regardless of the reason, the abundant cacomixtles in Mexico City give us hope for their ability to survive and adapt to change.

Isla Espíritu Santo

In the Gulf of California, near the southern tip of Baja California Sur, lie three islands inhabited by cacomixtles. Here, scientists have designated each island’s population of cacomixtles as a subspecies based on their physical features differing from cacomixtles on the mainland. They are beloved to the people there as well, who affectionately call them “babisuris” to distinguish them from mainland cacomixtles. Babisuris are the mascot of Isla Espíritu Santo, which is a protected area by Comisión Nacional de Áreas Naturales Protegidas, a government department in Mexico that manages natural areas. The babisuri subspecies on Isla Espíritu Santo, along with several other small mammals, are endemic to the island because they occur nowhere else on the planet.

While the island has extremely minimal development and restricted tourism, it has been greatly affected by human activity, particularly by invasive species. Invasive species are animals that humans have introduced to an environment, which then prosper and negatively affect the native species. Domestic goats and cats were introduced to the island around a century ago and have become abundant. Goats are frequently introduced to islands to supply fishing communities with meat. Where introduced, goats graze native vegetation, thereby affecting soil health and habitat structure. Controlling their populations by hunting has had limited success, as goats are able to quickly retreat up rocky terrain that is difficult for people to access. Goats are likely affecting the babisuris indirectly, by mowing the plants babisuris eat from and degrading their habitats.

Cats also arrive on islands by way of fishing ships, where they are recruited to control the rodent pest populations. Cats are exceptionally good predators and have evolved hyper-carnivory, or exclusive meat-eating. They are especially harmful to naive prey populations on islands that do not have many natural predators. Cats alone have caused over sixty extinctions of small mammals, birds, and lizards globally. Efforts to remove them have also had limited success. Their secretive, nocturnal nature makes them difficult to capture, and their rapid reproductive rate makes their populations difficult to suppress. Babisuris and cats are both nocturnal carnivores, so they are likely competing in multiple ways. Indirectly, cats eat the same food as babisuris. Directly, cats might be marking territories and fighting, or even killing, babisuris which can limit the babisuris’ ability to use the already limited island habitat. Indeed, guides have seen cats and babisuris fighting on the beaches for food.

My research aims to investigate how the presence of invasive cats is affecting the native mammal community on Isla Espíritu Santo. We use wildlife cameras to detect which species are present in different locations across the island. By comparing habitats, nocturnal activity, and behaviors at the camera traps, we can evaluate how cats are affecting babisuri behavior and ecology. Any negative impact cats have on babisuris can pose a great threat to their existence on the island. As an endemic subspecies, protecting this population is especially important to conserving this island’s ecosystem.

The future of cacomixtles in a changing world

Cacomixtles are subject to many anthropogenic disturbances. These disturbances are likely affecting the species in ways we cannot yet detect. However, this does not mean that the species is doomed. Around the world, people are taking action to conserve species and communities so they will be resilient to continued change. These actions would not be possible without the partnerships between local peoples, government agencies, nonprofit organizations, and academic researchers. From large projects, like the Liberty Canyon wildlife crossing, to community projects, like surveys of urban cacomixtles in Mexico City, people continually show their passion for conservation of our cherished ecosystems.

What does the future hold for cacomixtles? This depends heavily on our ability to mitigate impacts of development, hold governments and corporations accountable for climate change, and fund local projects. Engaging and empowering the public to support conservation actions is our best opportunity to protect cacomixtles and ensure the resilience of the remarkably biodiverse ecosystems of the Americas.


Pictures by Madeleine E. Zuercher



The opinions expressed in this blog post represent the views of the author and not of the UCLA Latin American Institute.