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Black Rat Snake

Overview:

Scientific Name: Pantherophis obsoletus

Size: 40 – 101” (adult total length)

Status: Historically abundant throughout its range but have declined or been extirpated in much of its range over the past couple decades

Michigan State Status: Special Concern

MDNR Wildlife Action Plan Status: Species of Greatest Conservation Need

Habitat:

Inhabits open areas such as shrubby fields, pastures, hedgerows, and bog or marsh edges located adjacent to woodlands. They also commonly utilize abandoned agricultural fields and associated structures like barns or farmhouses. Black rat snakes will even occupy artificial cover objects as well as other structures near human development and waste centers.  

Conservation:

Despite inhabiting a vast distribution, black rat snake populations in Michigan are relatively scarce, which puts them at increased risk of threats such as habitat destruction. Activities like extensive deforestation and urbanization that alter the landscape are especially harmful to small, localized populations. Persecution is also another factor influencing declines in black rat snake populations as they are often mistaken for rattlesnakes and are discriminately killed. Another growing issue that is impacting this species is collection for the pet trade due to the black rat snake’s popularity in the market.  

Best Management:

Identify and protect Black rat snake habitat containing extant populations. Avoid extensive tree harvest but, if necessary, conduct harvest during late fall to early winter. Consider utilizing various tree harvest techniques paired with an appropriately timed rotation as opposed to clearcutting. Use coarse woody debris to create habitat structures as well as maintain the litter layer and understory vegetation. Provide hibernacula structures by excavating a pit to a depth of at least 8’, then place rocks, logs, tubing, pipes, concrete, rubble, and/or other objects into the pit to allow for interspatial gaps. Once filled with objects, cover the pit with soil while allowing small openings to remain to act as entry ways. Provide basking structures typically constructed by piling wood or rocks and allow for gaps. If mowing is required, mow infrequently and during the hottest times of the year. Either set mower decks high (>6”) to allow room for wildlife under the mower or set the deck low (<2”) to discourage the movement of herpetofauna into mowed areas if desired. It’s important to note that wildlife clearance surveys must be conducted prior to any mowing operations in areas containing rare herpetofauna. Provide nesting structures if naturally occurring features are not present. 

Adult Coloration:

Overall dark brown or black dorsally, while the throat, chin, and labial (lip) are white. Ventral scales are cream white to yellow but is obscured with gray or brown pigment towards the tail and a dark checkerboard pattern towards the head. Blotched patterning containing hints of white, yellow, or orange flecks present in juveniles may faintly persist into adulthood 

Adult Characteristics:

Considered one of the longest snakes in North America, this species is capable of reaching great lengths. Despite this, the black rat snake is slender with an elongated and flattened head with no distinct snout. The scales of their upper body are slightly keeled, and their anal plate is divided.  

Mass: 600 – 1000 g 

Typical lifespan in wild: 16 – 33 years in captivity 

Breeding interval: Multiple times annually  

Breeding season: April to June 

Range number of offspring: 4 – 44 

Average number of offspring: 15 

Range time to hatchling: 65 – 70 days (incubation) 

Average age at sexual/reproductive maturity (females): 3 – 7 years 

Average at sexual/reproductive maturity (Male): 3 – 7 years 

Diet: Prairie Voles, Pine Voles, Western Harvest Mice, White-footed Mice, House Mice, Eastern Cottontails, Hispid Cotton Rats, Eastern Woodrats, and Northern Short-tailed Shrew 

Predators: Red-tailed Hawk, Broad-winged Hawk, Eastern Screech Owl, raccoon, coyote 

Juvenile Characteristics:

Juveniles are pale grey with a distinct dark grey or brown band pattern running along their back which alternates with smaller side markings. They have a black band in the front of their eyes as well as a black eye stripe that extends to the back of the jaw.   

Species Confused With:

This species may be confused with racers; however, unlike the black rat snake, racers have unkeeled scales and a rounded body. Juvenile racers also lack a black eye stripe that extends to the back of their jaw.  

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