Black squirrels are a captivating color morph, not a separate species, characterized by their dark fur. Their prevalence is influenced by the genetic basis of their unique coloration and environmental factors.
What Makes a Squirrel Black?
Black squirrels are melanistic, possessing an abundance of dark pigment in their fur. This coloration results from a genetic variation, most frequently observed in eastern gray squirrels (Sciurus carolinensis) and fox squirrels (Sciurus niger). Melanism in eastern gray squirrels is often linked to a 24 base-pair deletion in the melanocortin-1 receptor (MC1R) gene, which enhances dark pigment production. This genetic alteration is dominant, meaning a squirrel can exhibit black fur with one copy of the mutated gene. The mutation likely originated in fox squirrels and spread to gray squirrels through interbreeding.
Where Black Squirrels Are Most Common
Black squirrels are not uniformly distributed, with notable concentrations in specific regions. Eastern gray squirrel black morphs are most prevalent in the northern parts of their range, particularly around the Great Lakes Basin. Ontario, Canada, and Michigan, USA, show the highest frequencies, with black squirrels comprising a significant majority of the squirrel population in some areas (e.g., 66 percent in Ontario, 56 percent in Michigan). Other Great Lakes states, including Ohio, also have substantial melanistic populations, with approximately 15 percent of eastern gray squirrels in these regions being black.
South of the Great Lakes, black squirrel populations tend to be more localized. Kent, Ohio, for example, is known for its black squirrels, originating from a 1961 introduction of ten Canadian black squirrels to Kent State University. These squirrels thrived and interbred with the local population.
Marysville, Kansas, adopted the black squirrel as its city mascot in 1972, with folklore suggesting their presence stems from a 1912 carnival escape. About one-fifth of Marysville’s squirrel population is now black.
Black morphs of fox squirrels are most common in the southeastern United States, but they also form large localized populations, such as in Council Bluffs, Iowa, where roughly half of the fox squirrels are melanistic. Black squirrels have also been introduced to other areas, including the United Kingdom, during the 19th and 20th centuries.
Why Some Environments Favor Black Squirrels
Environmental factors influence the success of black squirrels. One theory suggests darker fur provides a thermoregulatory advantage in colder climates. Their darker coats absorb more solar radiation, helping them warm up efficiently and conserve energy during harsh winters. This thermal benefit may have contributed to the eastern gray squirrel’s northward range expansion.
Camouflage is another advantage. Black squirrels may blend more effectively into dimly lit or dense, dark forested environments, especially those with conifer trees. This improved concealment offers better protection from predators like hawks and owls.
However, in open, lighter environments, such as deciduous forests in winter, their dark coloration can make them more conspicuous. Black squirrels are often more common in urban areas, possibly due to reduced hunting pressures. Some studies also suggest they might be less prone to road mortality in cities because their darker color makes them more visible to drivers.
Current Population Trends
The population trends of black squirrels vary by region. While historical accounts suggest a decline in the black morph’s frequency in eastern gray squirrel populations since the late 1700s, especially south of the Great Lakes, their numbers appear stable or increasing in specific areas. In places like Ontario and Michigan, black squirrels remain the predominant color morph.
Ongoing research monitors these populations, with observations showing varying trends even within localized areas. Interbreeding between black and gray squirrels is common, as they are the same species, and the dominant black fur gene facilitates its spread. Habitat changes, including urbanization, and climate shifts continue to influence their numbers. The adaptability of black squirrels to urban environments suggests their continued presence and potential increase in human-dominated landscapes.