The Black Racer (Coluber constrictor) is a common, non-venomous snake species found across North America, known for its speed and active, diurnal nature. This reptile is frequently encountered in many different habitats, from open fields to suburban yards. Their size can sometimes be surprising to those who encounter them in the wild. This article details the typical and maximum sizes Black Racers attain and the factors that influence their final growth.
Identifying the Black Racer
The Black Racer is a slender snake with a long body and relatively large eyes, which aid in visual hunting during the day. Adult Black Racers are uniformly black on their dorsal side with smooth, unkeeled scales that give them a slightly glossy appearance. Their chin and throat are often a contrasting white or light gray, while the belly is typically a solid dark gray or black.
Juvenile Black Racers look quite different, possessing a blotched pattern that often leads to misidentification. These young snakes start out gray or tan with a series of reddish-brown or dark gray blotches running down the center of their back. This pattern gradually fades as they grow, and the snake achieves its solid black adult coloration when it reaches about 2 to 3 feet (60 to 90 cm) in length. Black Racers are highly active predators that pursue and subdue prey, such as small rodents, lizards, birds, and insects, without using constriction.
Typical and Record Measurements
The typical adult length for a Black Racer ranges from 3 to 5 feet (91 to 152 cm). Many individuals mature into an average size of around 4 feet (122 cm). Hatchlings are born small, measuring approximately 8 to 10 inches (20 to 26 cm).
The maximum verified length for a Black Racer is slightly over 6 feet (183 cm), with the record cited at 73 inches (185.4 cm). While reports of snakes exceeding 6 feet do occur, these are extremely rare and represent the maximum growth potential under ideal conditions. Compared to many other snakes of similar length, the Black Racer is notably slender, lacking the girth of constrictors like rat snakes.
A typical adult specimen weighs around 1.2 pounds (556 grams), with little difference in mass between adult males and females. Racers generally reach sexual maturity in about two years, and continued growth may take several years to approach their full adult size.
Geographic and Environmental Size Variation
The size an individual Black Racer reaches is significantly influenced by geographic location and environmental factors, which often correlate with different subspecies. The species Coluber constrictor is divided into several recognized subspecies across its vast range, such as the Northern Black Racer (C. c. constrictor) and the Southern Black Racer (C. c. priapus). Southern populations, particularly certain subspecies in warmer climates, have sometimes been observed to reach the greater lengths, contributing to the maximum size records.
Differences in size are not strictly genetic but also reflect the local environment’s capacity to support growth. A primary environmental factor is the availability of food; snakes in areas with abundant prey will generally grow faster and may achieve a larger adult size. Conversely, those in less productive habitats or with shorter active seasons may mature at the lower end of the typical size range. Age is also a factor, as the largest individuals are those that have survived the longest, allowing for continued, though slower, growth beyond maturity.