Snakes are often viewed solely as predators, equipped with specialized senses, constriction, or venom. Yet, these reptiles are constantly exposed to a wide array of threats throughout their lives, making them prey or victims in various circumstances. Mortality factors span the biological world, the physical environment, and the increasing influence of human activity. The serpent’s survival is a perpetual challenge.
Biological Adversaries and Natural Predators
A snake’s greatest danger often comes from other living organisms, including specialized predators. Mammals such as the mongoose are renowned for their ability to hunt venomous snakes, a feat accomplished by speed and a biological defense. Mongooses possess a mutation in their nicotinic acetylcholine receptors, the target of neurotoxins in snake venom, granting them a partial resistance that prevents paralysis from most bites.
Birds of prey, including hawks, eagles, and owls, use their superior aerial perspective and powerful weaponry to neutralize a snake’s defenses. These raptors strike with sharp talons, often aiming for the head or spine. Their scaly legs can provide protection against defensive bites. On the ground, species like the coyote and bobcat employ quick reflexes and strategic attacks, relying on flawless timing to kill a snake before it can strike.
The most unexpected adversaries are often other snakes, a phenomenon known as ophiophagy. Kingsnakes, for instance, are non-venomous constrictors that routinely prey on rattlesnakes and copperheads. They are protected by a natural immunity to the venom of snakes in their geographical range, allowing them to subdue their prey using powerful constriction. The King Cobra, the world’s longest venomous snake, also has a diet consisting almost exclusively of other snakes.
Lethal Environmental Conditions
As ectotherms, snakes depend on external heat sources to regulate their body temperature, making them highly vulnerable to thermal extremes. In cold climates, a sudden temperature drop can be lethal, as temperatures consistently below 50 degrees Fahrenheit (10 degrees Celsius) begin to shut down bodily functions. If a snake is unable to find a safe hibernaculum for brumation, it risks freezing to death or developing fatal respiratory infections.
A snake’s digestive process is also temperature-dependent, requiring an internal temperature of about 80 to 85 degrees Fahrenheit (27 to 29 degrees Celsius) for efficient function. If an animal consumes prey and the ambient temperature drops too low, the food can rot in its stomach, leading to sepsis and death. Conversely, extreme heat can cause rapid mortality through overheating and dehydration, especially when temperatures exceed 104 degrees Fahrenheit (40 degrees Celsius).
Natural disasters pose a direct threat by altering the environment. Floods do not necessarily drown all snakes, as many are capable swimmers, but they displace the animals from their established territories. This displacement exposes them to predators and often drives them into human-occupied areas, increasing the likelihood of fatal conflict. Similarly, fast-moving wildfires can trap and incinerate snakes, or destroy the crucial cover and burrow systems they rely on for thermoregulation and safety.
Pathogens and Internal Threats
Snakes are susceptible to a range of diseases and parasites that compromise their health and lead to death. Snake Fungal Disease (SFD), caused by the fungus Ophidiomyces ophidiicola, manifests as facial swelling and skin lesions. It can progress to internal infections like pneumonia. This disease is a growing concern for wild snake populations across multiple continents.
Viral infections also present a significant internal threat, most notably Inclusion Body Disease (IBD), which is highly contagious and affects boas and pythons. IBD causes severe neurological symptoms, such as the characteristic “stargazing” posture where the snake stares upward, along with chronic regurgitation and a weakened immune system. The disease is invariably fatal and there is currently no cure.
Parasites contribute to mortality by draining resources and acting as vectors for disease. Heavy infestations of the common snake mite, Ophionyssus natricis, can cause anemia due to blood loss and are known to transmit IBD between snakes. Internal parasites, such as pentastomes or lungworms, feed directly on lung tissue, leading to pneumonia, chronic inflammation, and eventual death through starvation or systemic failure.
Direct Human Impact
Human activity is responsible for a major source of snake mortality, both intentionally and accidentally. Road mortality is a significant threat to many species; studies suggest that in high-traffic areas, up to 10 to 20 percent of a local snake population can be killed by vehicles annually. Snakes are particularly vulnerable when crossing roads, as they often warm themselves on the asphalt and their slow movement makes them difficult for drivers to avoid.
The widespread use of anticoagulant rodenticides, or rat poison, creates a lethal scenario known as secondary poisoning. Snakes consume rodents that have ingested the poison, and the toxins—which prevent blood from clotting—are transferred up the food chain. Studies have found high exposure rates to these rodenticides in wild snakes that prey on mice and rats, resulting in fatal internal hemorrhaging.
Intentional killing, often driven by fear or a mistaken perception of threat, accounts for a large number of snake deaths. Attempts to kill a snake are a leading cause of defensive snakebites in humans, as the interaction is provoked and the snake is forced to defend itself. Another source of mortality is the use of glue traps, which are designed for rodents but are indiscriminate. Snakes get stuck to the adhesive and die slowly from exhaustion, dehydration, starvation, or severe injuries from struggling to escape.