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New Jersey Endangered and Threatened Species Field Guide

Image of Timber rattlesnakes and other venomous snakes have a vertical pupils.Zoom+ Timber rattlesnakes and other venomous snakes have a vertical pupils. © George Cevera

Timber rattlesnake

Crotalus horridus horridus

Species Group: Reptile

Conservation Status

State: Endangered



Timber rattlesnake colors and patterns are highly variable geographically. In New Jersey, two color morphs occur - yellow or black. An average of 24 dark brown or black body blotches, crossbands or both are found from the neck to the base of the tail. Often the crossbands are not complete near the head but by mid-body they join to form crossbands having the shape of a chevron. A dark color (black or brown) is found on the last few inches of the tail. Black morphs have a black head and may have much black color throughout whereas yellow morphs have a yellow or light tan head color.

The timber rattlesnake’s most distinguishing characteristic is its rattle. The rattle is composed of interlocking segments of dry, horny, keratinized skin that are not lost during shedding. When frightened, rattlesnakes vibrate their tails making a buzzing sound. This acts as a warning signal to predators.

Image of Range of the Timber rattlesnake in New Jersey.Zoom+ Range of the Timber rattlesnake in New Jersey.

Distribution and Habitat

Timber rattlesnakes are found in two separate regions of the state. In northern NJ they are found in the mountainous portions of Warren, Sussex, Passaic, Morris and Bergen counties. In southern NJ they are found in the Pinelands region and nearby portions of Cumberland, Ocean, Burlington and Atlantic counties.

Timber rattlesnakes are ectothermic and therefore must hibernate during the winter to escape the cold. The den is central to each population’s habitat. In northern NJ, dens are typically located on rocky hillsides where underground crevices extend below the frost line. Dens are generally found in areas lacking significant tree canopies and usually occur on southeastern to southwestern facing slopes. In southern NJ, timber rattlesnakes use quite different denning habitat. Here timber rattlesnakes usually den along streams in white cedar swamps. They use crevices among the tree roots to access underground cavities just above the groundwater line. At least one southern NJ den occurred in an upland location associated with a tree stump.


Adult rattlesnakes have a varied diet. It may include shrews, moles, chipmunks, squirrels, and small rabbits. Baby rattlesnakes eat young shrews and moles.

Life Cycle

In New Jersey, rattlesnakes usually enter the den from mid-September to early November and emerge from hibernation between early April and mid-May. Rattlesnakes return to the same den, and often the same crevice, every year.

Upon emergence in the Spring, rattlesnakes remain in the vicinity of the den and bask when the weather is suitable. As the temperature warms and becomes more consistent, snakes begin to migrate away from the den and into the surrounding forest to forage. They tend to use the same general summer foraging habitat year after year.

Image of A black phase timber rattlesnake.Zoom+ A black phase timber rattlesnake. © George Cevera

Timber rattlesnakes have long life spans, often up to 25 years. However, they have a low reproductive rate. Females in NJ generally reproduce at three or four year intervals. Their age at first reproduction is generally nine or ten years. They have very small litters usually ranging from six to nine young.

Mating generally occurs from mid-July through early September. During this time male snakes will make long, straight-line movements in search of females. When they intersect with a female’s trail they follow her scent. The snakes may remain together for as little as a couple of days to more than a week. After mating occurs the snakes go their separate ways.

The sperm is stored within the female’s oviduct over the ensuing winter until the following spring when the eggs are fertilized and the snake becomes gravid (pregnant). Gravid females generally remain close to the den site and select open basking habitats for gestation. The normal gestation period is three months. When the fetuses are fully matured they are expelled one at a time in the fetal sacs. They soon break out of the sac and crawl to a nearby spot. The young remain with the female until their first shed, which occurs in 7 to 10 days. After shedding they disperse, as does the female. Juveniles have very high mortality rates (low survivorship).

Current Threats, Status, and Conservation

In NJ, timber rattlesnakes are listed as endangered and receive full protection under the law. Unfortunately, there is little protection for the critical habitat required by rattlesnakes. As human/snake encounters increase and as human encroachment into rattlesnake habitat, many populations that occur on private land will continue to decline.

The primary threats to timber rattlesnakes in NJ come from human-related factors. These include malicious killing, illegal collecting, human incursions into rattlesnake range, and behavioral disturbance by people.

Image of Timber rattlesnakes are very passive and will only strike when they are disturbed or threatened.Timber rattlesnakes are very passive and will only strike when they are disturbed or threatened. © George Cevera

Ignorant people that perceive them to be a threat often kill timber rattlesnakes. In fact, timber rattlesnakes, or any other snake, rarely if ever bite without being provoked. Nearly all cases of snakebites occur when untrained people attempt to handle them. Snakes will bite in self-defense but will never attack a person. If given the opportunity they will always attempt to escape.

Illegal collecting of timber rattlesnakes continues to be a problem throughout their range. The primary market for timber rattlesnakes is in the pet trade. They are desirable because of their striking coloration and their ability to adapt well to captivity.

As humans continue to encroach on timber rattlesnake habitat it is beginning to cause major problems. Pressures from new housing developments, golf courses, shopping centers, and the associated roads and increased traffic all contribute to increased mortality.

When timber rattlesnakes are continually disturbed in important habitats where they frequently congregate, such as basking areas, they may abandon the sites completely. These areas are often critical to the survival of the population. Such disturbances can have detrimental effects on populations that are often already under stresses from other human related factors.

Scientific Classification

Kingdom: Animalia
    Phylum: Chordata
       Class: Reptilia
          Order: Squamata
             Family: Viperidae
                Genus: Crotalus
                   Species: C. horridus horridus

Find Related Info: Endangered, Reptiles

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