Garter snakes are common reptiles found across North America. Many people wonder if these striped snakes lay eggs, as egg-laying is a common reproductive method among many snake species.
Garter Snake Reproductive Strategy
Garter snakes do not lay eggs. Instead, they exhibit ovoviviparity, meaning they give birth to live young. This distinguishes them from oviparous snakes, which lay eggs that hatch outside the body, and viviparous snakes, where young develop inside the mother with direct nourishment, similar to mammals.
The Live Birth Process
The reproductive cycle for garter snakes typically begins in the spring, shortly after they emerge from hibernation. Males will seek out females, often forming large “mating balls” around a single female. After successful internal fertilization, the female carries the developing embryos within her oviducts. Gestation usually lasts for about two to three months, although this can vary.
During this period, the developing young receive nourishment primarily from the yolk sacs within their individual eggs, which lack hard shells. The female may bask in the sun to maintain an optimal body temperature for the internal incubation of her offspring. A female garter snake can give birth to a litter typically ranging from 10 to 40 offspring, with some litters reaching 80 babies. The birthing process can take several hours. The newborn garter snakes are fully independent at birth, ready to hunt and care for themselves without parental involvement.
Why the Confusion About Snake Eggs?
The common misconception that garter snakes lay eggs stems from the fact that a majority of snake species globally, approximately 70%, are oviparous. These egg-laying snakes, such as pythons, kingsnakes, and corn snakes, deposit their eggs in sheltered locations like burrows or under leaf litter, where the eggs incubate externally. This widespread reproductive method leads many people to assume all snakes reproduce in the same way.
While most reptiles lay eggs, some, including garter snakes, have evolved different strategies. The terms oviparous, ovoviviparous, and viviparous describe these distinct reproductive approaches.
Ecological Advantages of Live Birth
Live birth offers several ecological advantages for garter snakes, particularly in certain environments. Retaining the developing young inside the mother’s body provides increased protection from external threats like predators, which might otherwise consume vulnerable eggs. This internal development also shields the offspring from harsh environmental conditions and temperature fluctuations.
The ability of the mother to move to warmer or cooler locations allows her to regulate the temperature for her developing young, enhancing their chances of survival. This adaptation is especially beneficial for snakes living in colder climates or at higher altitudes, where ground temperatures might be too low for external egg incubation. Live birth also allows the female to be more mobile while gravid, potentially aiding in predator avoidance.