Predators, starvation, weather, disease, poison, and even their own neighbors all take turns killing voles and moles. Despite often being lumped together as “lawn pests,” these two groups of small mammals lead very different lives and face overlapping but distinct threats. Voles are rodents that eat plants and live in grassy runways or shallow burrows; moles are insectivores that tunnel through soil hunting earthworms. What unites them is a remarkably high mortality rate, with most individuals dying within their first year of life. The forces behind that mortality are more varied and interconnected than most people realize.
Predators Take the Biggest Bite
For voles, predation is the single most important source of mortality in many habitats. Hawks, owls, foxes, coyotes, weasels, snakes, and domestic cats all eat voles regularly. A single barn owl family can consume thousands of voles in a breeding season. Because voles are small, abundant, and active near the surface, they sit at the base of many food chains, and predator populations often rise and fall in sync with vole numbers. Weasels and other small mustelids are especially effective because they can follow voles directly into their burrow systems.
Moles face less predation overall because they spend most of their time underground. Still, owls and hawks occasionally catch them at the surface, and domestic cats and dogs dig them out. Foxes and coyotes will eat moles when they find them. The mole’s main defense is simply being underground and hard to reach, but that protection comes with its own set of costs.
Starvation and Winter Food Shortage
Voles often die of starvation, particularly during winter. Because they do not hibernate, voles must eat constantly through cold months. Multiple field experiments have demonstrated that when vole populations are protected from predators, the next limiting factor on their numbers is winter food supply. One long-term study found that supplementing food in predator-free enclosures prevented winter population crashes and boosted overwinter survival, while identical food supplements in unfenced areas exposed to predators had no detectable effect because predators were already keeping numbers down.1Ecology. Winter food supply limits growth of northern vole populations in the absence of predation In other words, predation and starvation work as a one-two punch: predators claim most voles first, and food shortage finishes off the survivors.
A separate experiment tracking bank voles over two consecutive winters drove this home. Survival on food-supplemented plots was roughly four and a half times higher than on control plots across both winters. In one particularly harsh winter, survival was about 30 times higher on fed plots at low elevation and about 20 times higher at high elevation.2PubMed Central. Surviving winter: Food, but not habitat structure, prevents crashes in cyclic vole populations Habitat structure, like adding logs and brush for shelter, did not help. Food was the bottleneck.
Moles face a different version of this problem. They eat invertebrates, primarily earthworms, which become harder to find in frozen or drought-hardened soil. Moles have unusually high metabolic rates for their size. The star-nosed mole, for instance, burns energy at a rate substantially higher than predicted for a land mammal of its weight, likely because of its active, semi-aquatic lifestyle.3Comparative Biochemistry and Physiology Part A. Fasting metabolism and thermoregulatory competence of the star-nosed mole, Condylura cristata (Talpidae: Condylurinae) A metabolism that hot demands constant fueling. Even brief interruptions in food supply can be fatal for moles, which is why prolonged freezes or severe droughts can wipe out local populations even though no predator or disease is involved.
Flooding and Extreme Weather
Flooding is devastating for burrowing animals. When water fills tunnel systems, residents either drown or are forced to the surface, where they become easy prey. A study tracking small mammal populations after a major flood found that every ground-dwelling species experienced significant population declines, and their numbers stayed depressed for at least a full year afterward. The only species that escaped this pattern was the arboreal western gray squirrel, which could simply climb above the water.4River Research and Applications. DECLINE AND RECOVERY OF SMALL MAMMALS AFTER FLOODING: IMPLICATIONS FOR PEST MANAGEMENT AND FLOODPLAIN COMMUNITY DYNAMICS
Subterranean mole rats, close relatives of true moles ecologically if not taxonomically, have evolved some tolerance for the low-oxygen, high-carbon-dioxide conditions that develop in flooded burrows. Researchers have recorded oxygen levels dropping as low as about 7% and carbon dioxide rising to about 6% in flooded clay-soil burrows, conditions that would be dangerous for most mammals.5Comparative Biochemistry and Physiology Part A. Oxygen and carbon dioxide fluctuations in burrows of subterranean blind mole rats indicate tolerance to hypoxic–hypercapnic stresses True moles likely have some tolerance as well, but they are not immune. A sustained flood event is a mass mortality event for any burrowing mammal that cannot escape to higher ground.
Drought matters too, though it kills more slowly. Dry conditions reduce both the plant material voles rely on and the earthworm populations moles depend on. In prolonged droughts, both animals may be forced to travel farther on the surface, increasing their exposure to predators.
Population Booms and Density-Driven Crashes
Voles are famous for dramatic population cycles. In some regions, their numbers explode every three to five years, then crash. What causes the crash is one of the more debated questions in ecology, and the answer is not always the same everywhere. A study of common voles in central Europe found something counterintuitive: during winter crashes, mortality did not actually increase at higher densities. Instead, the crash was driven by a collapse in reproduction and recruitment. At low density, about half the population was lost over winter. At high density, roughly 95% disappeared, but this was because animals simply stopped breeding and replacing themselves, not because they were dying at higher rates.6Population Ecology. Density‐dependent reproduction causes winter crashes in a common vole population
This is an important nuance. When people see a vole population collapse, they assume something killed them all. Sometimes that is true: predators or disease can trigger a crash. But in other cases, the population simply stops producing young at a rate that can outpace normal background mortality. The population dwindles not because more individuals are dying, but because fewer are being born. Crowding-related stress, competition for food, and reduced body condition during the boom phase all contribute to this reproductive shutdown.
Disease and Parasites
Disease kills individual voles and moles, and when vole populations boom, disease can become a major factor. Voles serve as reservoir hosts for a number of pathogens that also affect humans. One of the most striking examples is tularemia, caused by the bacterium Francisella tularensis. In northwestern Spain, every human tularemia outbreak recorded between 1997 and 2019 coincided with peak-phase vole abundances. The two largest epidemics, with over 500 confirmed human cases each, occurred in 1997–1998 and 2007–2008, both during vole population booms. When vole numbers peaked but stayed below a certain density threshold, no outbreaks were recorded.7Frontiers in Veterinary Science. Linking Zoonosis Emergence to Farmland Invasion by Fluctuating Herbivores: Common Vole Populations and Tularemia Outbreaks in NW Spain
This dynamic works both ways. The pathogen circulates within the vole population, causing mortality among the voles themselves, and then spills over to humans when vole numbers are high enough for transmission chains to sustain themselves. Other diseases that cycle through vole populations include hantaviruses and various bacterial infections. Parasites, including fleas and intestinal worms, are constant companions. While a healthy adult vole can tolerate moderate parasite loads, heavy infestations combined with food stress or cold weather can tip the balance toward death.
Moles are less implicated in disease outbreaks because they live solitarily and rarely reach high densities. They do carry their own parasites, including mites and internal worms, but these tend to be less consequential at the population level compared to what voles face.
Human Pest Control Methods
Humans kill enormous numbers of voles and moles intentionally. Voles damage crops, orchards, and turf, while moles tear up lawns and golf courses. The toolkit for killing them ranges from traps and fumigants to rodenticides, and each method comes with complications.
Zinc phosphide is one of the most commonly used acute rodenticides for voles. It works fast, breaking down into toxic phosphine gas in the stomach. But voles are remarkably good at learning to avoid it. When researchers tested zinc phosphide bait at concentrations between 0.4% and 3.2%, voles reduced their consumption by 87% to 98% compared with untreated bait. Doubling the concentration of zinc phosphide cut consumption roughly in half again, and even the red dye used in commercial bait reduced consumption by about 10%.8PubMed. Efficacy and attractiveness of zinc phosphide bait in common voles (Microtus arvalis) On top of that, voles develop bait shyness: after experiencing mild poisoning symptoms, they associate the flavor of the bait with sickness and refuse to eat it again. This learned avoidance can be triggered by many different components of the bait formulation, not just the active ingredient.9Crop Protection. Assessment of zinc phosphide bait shyness and tools for reducing flavor aversions
Anticoagulant rodenticides, which work by preventing blood from clotting, are another common approach. These are often considered more reliable because they act slowly enough that the animal does not associate the bait with its illness. But they carry a serious secondary poisoning risk. A global review of published studies found that various raptor species had over 60% detection rates for anticoagulant residues, meaning most predatory birds tested had measurable levels of rodenticide in their bodies.10PubMed Central. A review: poisoning by anticoagulant rodenticides in non-target animals globally
The real-world consequences of this secondary poisoning can be severe. When brodifacoum bait was used to control voles in orchards, researchers tracking radio-tagged eastern screech-owls found that minimum mortality was 58% among owls whose home ranges overlapped heavily with treated areas, compared with 17% among owls with less exposure. Secondary brodifacoum poisoning was the most probable cause of death in several of those owls.11Environmental Toxicology and Chemistry. Potential hazard to eastern screech-owls and other raptors of brodifacoum bait used for vole control in orchards At least one long-eared owl in the same study area also died of probable secondary poisoning. The irony is hard to miss: the very raptors that naturally control vole populations are being killed by the chemicals used to do the same job.
Agricultural Practices and Habitat Change
Farming practices shape vole and mole populations in ways that go beyond intentional pest control. A study of water voles and European moles in eastern France found that more intensive production indicators, such as heavy organic fertilization and frequent mowing, correlated with the early growth of vole populations. Fertilization encourages lush plant growth, which feeds voles, while mowing keeps vegetation at the short height voles prefer. In contrast, activities that physically disturb the soil, like grazing by livestock and tillage, correlated with lower vole abundance during the high-density phase of their population cycle.12Agriculture, Ecosystems & Environment. Responses of Arvicola terrestris scherman populations to agricultural practices, and to Talpa europaea abundance in eastern France
For moles, tillage is directly destructive. Plowing collapses tunnel systems that may represent months of digging effort. Moles that survive must rebuild from scratch, burning energy they may not have. Conversion of permanent pasture to cropland tends to reduce mole populations over time, while undisturbed grasslands and orchards support higher densities. Urbanization is similarly disruptive: paved surfaces and compacted soil eliminate habitat entirely.
This creates a paradox for farmers. The very practices that increase crop yields, like fertilization and irrigation, can also promote vole outbreaks that damage those crops. And the most effective non-chemical way to keep voles in check, which is grazing and soil disturbance, is not compatible with all farming systems.
Infanticide and Aggression Within the Colony
Voles also kill each other. Infanticide, the killing of pups by unrelated adults, is surprisingly common in meadow vole populations. Pregnant females are the most frequent offenders, often killing and consuming unfamiliar pups. Breeding males are also frequently infanticidal toward pups they encounter in unfamiliar territory, and at least half of them cannibalize their victims. Lactating females, by contrast, almost never commit infanticide, likely because they are invested in caring for their own young and the hormonal state of lactation suppresses aggressive behavior toward pups.
The motivation appears to be partly nutritional and partly competitive. A pregnant female gains both calories and the elimination of a future competitor’s offspring. For males, killing unrelated pups may increase their own reproductive success by freeing up the mother to breed again sooner. Whatever the reason, infanticide represents a meaningful source of pup mortality, particularly when population densities are high and encounters between unrelated animals are frequent.
Moles are also aggressive toward each other. They are largely solitary outside the breeding season, and territory disputes can result in serious injuries or death. Male moles in particular fight viciously when their tunnel systems intersect, and these encounters occasionally prove fatal.
Pollution and Heavy Metal Accumulation
A slower, less visible killer lurks in contaminated soil. Because moles eat earthworms, and earthworms accumulate heavy metals from the soil they pass through, moles can build up startling concentrations of toxic metals in their organs. Research comparing moles from the Helsinki metropolitan area with moles from rural Finland found that urban moles had significantly higher concentrations of cadmium, lead, and mercury, and lower body weight. The kidney cadmium levels in most Helsinki moles exceeded the threshold known to cause kidney damage in mammals. Lead concentrations in both mole livers and earthworms decreased with distance from highways, confirming the dietary pathway: contaminated soil leads to contaminated worms, which leads to contaminated moles.13Environmental Pollution. Accumulation of heavy metals in the mole in Finland
Voles face similar risks in polluted environments, though their plant-based diet means they accumulate somewhat different contaminant profiles. Pesticide exposure from treated agricultural fields is a particular concern, especially during and immediately after application when voles may eat freshly sprayed vegetation or seeds.
Heavy metal poisoning does not usually kill quickly. It erodes organ function over time, reducing an animal’s ability to reproduce, fight off infections, or survive cold weather. For short-lived animals like voles and moles, this chronic damage may not manifest as an obvious die-off, but it depresses the population quietly by reducing the fitness of every individual in a contaminated area. Urban and roadside mole populations, in particular, carry a toxic burden that their rural counterparts largely avoid.
Why Most Voles and Moles Die Young
The typical lifespan of a vole in the wild is measured in months, not years. Most never see their first birthday. Moles live somewhat longer, with some species reaching three to five years, but even they face constant attrition. The combination of predation pressure, seasonal food scarcity, weather disasters, density-dependent reproductive failure, disease, human control efforts, and environmental contamination means that most individuals encounter at least one of these threats before they have a chance to grow old.
What makes voles and moles ecologically resilient despite this carnage is their reproductive output. Voles can produce multiple litters of several pups each per year, beginning when they are just a few weeks old. Moles have smaller litters but reproduce reliably in spring. As long as habitat exists and food is available, these populations bounce back quickly from crashes, whether those crashes were caused by a harsh winter, a flood, a predator boom, or a round of rodenticide. The real threat to long-term population health is not any single source of mortality but rather the permanent loss of habitat through development, large-scale contamination of soil, or the chronic removal of the predators that keep boom-and-bust cycles from spiraling into agricultural damage. For homeowners and farmers dealing with these animals, understanding the full range of what kills them helps explain why a single control method rarely provides a lasting solution: remove one threat, and another fills the gap almost immediately.