Rat snakes eat exactly what their name suggests: rats, mice, and other rodents make up the bulk of their diet. But these snakes are opportunistic hunters that also take birds, bird eggs, chipmunks, moles, amphibians, lizards, and insects depending on their size and habitat. What a rat snake eats shifts considerably as it grows, and where it lives plays a major role in what ends up on the menu.
Primary Prey Items
Rodents are the cornerstone of a rat snake’s diet across every species in the group. Mice and rats are the most common targets, but rat snakes also regularly eat chipmunks, moles, and other small mammals. They hunt actively rather than ambushing, which means they follow scent trails into burrows, up trees, and through dense vegetation to find prey.
Birds and bird eggs round out the diet for adult rat snakes. They’re skilled climbers and frequently raid nests in trees and shrubs, eating both nestlings and eggs when they find them. Egg-eating is more common in larger adults because eggs are surprisingly difficult for snakes to swallow. The wide, round shape of an egg demands a bigger gape than soft-bodied prey of similar weight, so juvenile rat snakes generally can’t manage eggs at all. Adults swallow them whole and crush them internally. Reptiles, frogs, and insects fill in the gaps, though these tend to be secondary prey rather than staples for most adult rat snakes.
How Diet Changes With Age
A hatchling rat snake is far too small to tackle a mouse. Young rat snakes start with prey matched to their tiny body size: small lizards, tree frogs, insects, and newborn mice (called pinkies). As they grow through their juvenile stage, they graduate to larger mice and eventually to adult rats, birds, and eggs.
The general rule for prey size is that a rat snake can handle food roughly as wide as the widest part of its own body, or about 10% of its body weight. A hatchling might eat a single pinky mouse, while a full-grown eastern rat snake at five or six feet long can comfortably take an adult rat or a bird the size of a robin. This scaling means a rat snake’s ecological role shifts as it matures, from insect and lizard predator to a serious check on rodent populations.
How Rat Snakes Kill Their Prey
Rat snakes are constrictors. They strike, grab hold, and immediately wrap two or more coils around the prey’s chest. The process is fast: the momentum of the strike carries the snake’s body over and around the animal before it can escape.
What happens next is more sophisticated than simple squeezing. Research on constricting snakes has shown they can detect their prey’s heartbeat through their coils and adjust pressure in response. Snakes constricting prey with a detectable heartbeat made significantly more tightening adjustments (averaging about five per feeding event) compared to nearly zero when no heartbeat was present. They also held on nearly twice as long, around 22 minutes versus 12, and applied more than double the total pressure. In other words, the snake knows when its prey is still alive and keeps squeezing until the heart stops. Death comes from circulatory failure, not suffocation as was once believed.
For eggs and other non-living prey items, constriction obviously isn’t needed. The snake simply positions the egg in its jaws and works it backward into its throat using alternating movements of the left and right sides of its jaw.
Feeding Frequency and Energy Needs
Rat snakes don’t eat every day. Their cold-blooded metabolism is far more efficient than a mammal’s, so a single meal sustains them for a surprisingly long time. In general, adults eat once every 10 to 14 days, juveniles every 7 to 10 days, and hatchlings every 5 to 7 days. Smaller snakes eat more frequently because they’re growing rapidly and burn through their energy reserves faster relative to body size.
A rat snake’s caloric needs also fluctuate with temperature. Their metabolic rate is highest at warmer temperatures (around 86°F) and drops significantly in cooler conditions. During winter, many rat snakes brumate, a reptile version of hibernation, and stop eating entirely for weeks or months. In spring, they emerge hungry and feed more aggressively to recover lost body mass before breeding season.
Rat Snakes Near Homes and Chicken Coops
Rat snakes are common visitors to barns, sheds, and chicken coops, and their behavior in these settings reveals a lot about their dietary preferences. Chicken feed attracts mice and rats, which in turn attract rat snakes. Many backyard chicken keepers report that a resident rat snake dramatically reduces the rodent population around their coop within weeks.
The trade-off is eggs. A rat snake living near a chicken coop will typically eat one egg per visit, treating it as an easy supplement to its rodent diet. They pose no threat to full-grown chickens, which are far too large to be prey. Very young chicks, however, can be at risk. Most chicken keepers who understand this dynamic consider rat snakes net beneficial: the rodent control they provide outweighs the occasional lost egg, and some people deliberately leave rat snakes undisturbed for exactly this reason. Removing attractants like wooden decoy eggs (which snakes can’t digest) helps keep the arrangement manageable.
Water and Hydration
Rat snakes need fresh water to drink, and the moisture they get from prey alone isn’t enough to keep them hydrated. Research on related snake species has demonstrated that dietary water does not prevent dehydration on its own. Snakes become thirsty after losing roughly 4 to 5% of their body mass in water, at which point they actively seek out fresh water sources.
In the wild, rat snakes drink from streams, puddles, rain droplets on vegetation, and standing water in tree hollows. They don’t need large bodies of water, just periodic access to fresh water between meals. This is one reason rat snakes are commonly found near water sources, even though they aren’t aquatic snakes. If you keep one in captivity, a clean water dish available at all times is essential, not optional.