Meet the northwestern garter snake – a mysterious serpent that mesmerizes with its beauty and resilience. Get ready to unravel the secret facts of this enchanting reptile, as we delve into its fascinating world of patterns and adaptability.
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Colubridae
Genus: Thamnophis
1. They are colorful
The northwestern garter snake possesses a range of colors and patterns, giving it a distinct appearance. ts dorsal coloring can vary and include shades of black, brown, slate gray, or dark brown, sometimes accompanied by a hint of bluish or green hues. The adults have a size of about 24 inches (61 cm) in length.
Typically, this snake displays three stripes. A narrow vertebral stripe runs along its back, while two thin lateral stripes grace its sides. However, it’s important to note that some individuals may lack these stripes altogether. The coloration of the vertebral stripe can span a spectrum from green, yellow, tan, red, and orange, to turquoise, white, and blue. Similarly, the lateral stripes can be observed in shades of turquoise, yellow, blue, white, or green. The lower surface exhibits hues of gray, yellowish, brown, or black, frequently adorned with red specks or dark spots.
These garter snakes exhibit a combination of stripes and spots on its body. In addition to the stripes, it may also have dark spots located between the vertebral stripe and the lateral stripes. However, these spots do not extend into the dorsal stripe. A distinguishing feature of this snake is the presence of white flecks on the edges of its dorsal scales.
Besides these white flecks, you can distinguish northwestern garter snakes from other garter snake species by the numbers of their scale. They typically have 17 rows of scales at the mid-body, occasionally 19. On the upper jaw, they have 7 upper labial scales, and 8 to 9 lower labial scales. In contrast, Western garter snakes generally have 19 or 21 rows of scales at the mid-body and more labial scales (8 upper and 10 lower scales.) These numbers in the common garter snakes are 19, 7, and 19, sequentially.
2. Banana slugs are their favorite
The northwestern garter snake is also called a slug specialist. You can know what they eat based on their name. They predominantly feed on slugs and terrestrial earthworms, particularly favoring banana slugs. In addition, their diet also includes salamanders ( like Pacific giant salamanders), small frogs, and other amphibious species. To find the potential prey, northwestern garter snakes as a method to detect chemical cues left behind by potential prey.
These snakes are threatened by many predators like northwestern crows, American crows, and hawks. To protect themselves from predators, the snakes come up with key strategies relying on their striped pattern.
They’ll do their evasive maneuvers called reversals, where they swiftly change direction when being chased. By coupling these reversals with their striped dorsal patterns, these snakes create an optical illusion that effectively confuses predators.
If they are caught, they will use their final defense mechanism. They will release venomous fluid and excrement from their anal glands when being touched, like other garter snake species. Some individuals might even vomit or resort to biting.
However, these northwestern garter snakes are not dangerous to humans. Although their mild venom is usually not fatal or capable of causing severe illness or injury in the majority of humans, you should steer clear of their bite.
3. Habitat
The northwestern garter snake inhabits the Nearctic region, spanning from the northern portion of Humboldt County, California, all the way up to Washington and Oregon in the northwestern US. This species can also be observed in southwestern Canada, with its distribution ranging from British Columbia to include Vancouver and Vancouver Island.
They can be found in a diverse range of habitats, such as shrublands, wetlands, forests, the edges of woodlands or thickets, and grasslands. Although they are not typically found in open water environments like other species of garter snakes, there have been occasional sightings of them in close proximity to such areas.
4. They live a lonely life
Northwestern garter snakes prefer a solitary lifestyle, devoid of social interactions or hierarchies. Their interactions with each other are limited to mating purposes alone. These diurnal snakes are always on the move, actively exploring their surroundings in search of food. Despite being terrestrial animals, they can swim.
In colder regions, they undergo hibernation throughout the winter season and emerge from their slumber in the spring, ready for the mating season. Upon leaving their winter dens, they may spend a few weeks in the neighborhood of their hibernation sites, completing the mating rituals before separating. This dispersal is dependent on favorable weather conditions.
Northwestern garter snakes rely on a combination of pheromones, sight, and touch to communicate with each other. To woo the males, females emit pheromones from their skin. The males detect these chemical signals through tongue-flicking. They can also find females by following her scent trail. These snakes make use of the sun as a navigational tool to enhance their ability to locate den sites.
When engaging in the mating process, both male and female northwestern garter snakes utilize tactile responses as a means of communication.
5. Reproduction
The Northwestern garter snakes engage in 2 breeding cycles per year. The initial breeding season takes place between late March and early April, while the second season occurs from late September to early October. Each breeding season typically spans about 3 weeks.
Male snakes emerge from their hibernation state and spend up to a week basking in the sun. They patiently await the awakening of the females to rouse from hibernation later. Once the females are awake, they release pheromones into the environment, which attracts hundreds of male snakes simultaneously.
This intriguing behavior, known as polygynandry, allows females to attract and mate with numerous male snakes. By doing so, they can store sperm from multiple males until ovulation occurs. This reproductive strategy ensures the fertilization of all eggs produced by the females.
Mating timing in Northwestern garter snakes is primarily affected by the temperature increase towards the end of hibernation, rather than by escalating levels of sexual hormones. Once the mating process is complete, snakes disperse to their summer foraging grounds.
Females experience ovulation between late May and early June. Their gestation period lasts around 9 weeks. Unlike the majority of snake species, garters do not lay eggs. Instead, they give birth to live offspring after the eggs hatch internally within their bodies. This usually occurs in late August.
They give birth to a clutch of 5 – 9 offspring. These newborns typically measure around 12.7 cm in length and weigh approximately 2 grams. They have the same coloration and patterning as the adult snakes. Upon birth, the babies are immediately on their own.
Male snakes typically achieve sexual maturity at approximately 12 months. On the other hand, the females need a bit longer to mature, about 2 years. In captivity, Northwestern garter snakes have been known to live up to 15.8 years. However, in the wild, their lifespan is shorter, approximately 4 to 6 years.
6. Conservation Status
The northwestern garter snake is categorized as “Least Concern” on the IUCN Red List, but it remains susceptible to various threats. Predation by avian predators and human activities such as excessive hunting, indiscriminate killing, the destruction of overwintering sites, and collecting pose significant risks to this species. Furthermore, the snake faces a threat of road mortality in regions where it needs to traverse roads to reach its overwintering or foraging habitats.
References:
- https://animaldiversity.org
- https://wdfw.wa.gov
