Ticks eat blood, and only blood. Every tick species feeds exclusively on the blood of vertebrate animals throughout its entire life cycle, from the larval stage through adulthood. This makes ticks obligate blood feeders, meaning they cannot survive on any other food source. Despite blood being their only meal, it’s nutritionally incomplete, so ticks rely on symbiotic bacteria living inside their bodies to fill in the gaps.
Blood Is Their Only Food
Unlike mosquitoes, which supplement blood meals with plant nectar, ticks have no alternative diet. Vertebrate blood is rich in proteins, iron, and salts but low in carbohydrates, fats, and vitamins. To compensate, ticks carry inherited bacterial partners that manufacture B vitamins like biotin, riboflavin, and folate on their behalf. These bacteria are passed from mother to offspring and are essential for survival. Ticks also lack most of the genes other animals use to produce and break down heme, a critical molecule found in red blood cells, so they depend on their host’s blood as the sole source of this compound.
What Hosts Do Ticks Feed On
Ticks feed on every class of land-dwelling vertebrate on Earth. Mammals, birds, reptiles, and amphibians are all fair game. A single study of tick diversity in the Neotropics documented 41 tick species feeding on 68 different vertebrate host species across 17 animal orders. Some ticks are generalists, latching onto whatever warm body passes by. Others are more selective, preferring specific hosts at different life stages.
Deer ticks, for example, often feed on mice and small mammals as larvae and nymphs, then target larger animals like deer as adults. Other species parasitize birds, lizards, or even tortoises. Humans are incidental hosts for most tick species, not their preferred target.
How Ticks Feed
A tick’s mouthparts work like a barbed ratchet. It has two main tools: a pair of cutting structures called chelicerae and a barbed, straw-like tube called a hypostome. The chelicerae are tipped with sharp digits and can telescope outward to nearly twice their resting length, powered by internal hydraulic pressure. During the initial bite, the two chelicerae move in alternating strokes, piercing the skin and creating an anchor point. Then, in a coordinated motion resembling a breaststroke, both chelicerae flex and retract simultaneously, pulling the barbed hypostome into the wound. The hypostome’s backward-facing barbs lock it in place, making the tick very difficult to remove.
Once anchored, the hypostome serves as a two-way channel. Blood flows in through it, while saliva is pumped back into the wound. That saliva is a cocktail of compounds that widen blood vessels, prevent clotting, reduce inflammation, and suppress the host’s local immune response. Without these countermeasures, the host’s body would form a clot, constrict nearby blood vessels, and mount an inflammatory response that would either push the tick out or cut off its blood supply.
How Much Blood They Consume
Hard ticks, the family that includes most species people encounter, are marathon feeders. They stay attached for days, slowly engorging until they’ve consumed enormous quantities of blood. A fully fed hard tick can ingest over 100 times its own unfed body weight in a single meal. For context, that’s like a 150-pound person drinking roughly 1,800 gallons of liquid in one sitting.
This prolonged attachment is part of what makes ticks effective disease carriers. Pathogens like the bacteria that cause Lyme disease or ehrlichiosis travel from the tick’s gut to its salivary glands during feeding, then get injected into the host along with saliva. Research on ehrlichiosis transmission found that ticks attached for fewer than 36 hours rarely transmitted the pathogen, which is why prompt tick removal matters so much.
One Blood Meal Per Life Stage
Ticks go through four life stages: egg, larva, nymph, and adult. Eggs don’t feed, but every stage after hatching requires exactly one blood meal to advance to the next. A larva feeds once, drops off its host, molts into a nymph, then waits (sometimes for months) before finding a new host for its next meal. The nymph feeds once, drops off, molts into an adult, and the cycle repeats. Adult females take one final, massive blood meal before laying eggs and dying.
This means a typical tick feeds on just three separate hosts over a life cycle that spans two to three years, depending on the species. Blacklegged ticks on the East Coast of the United States complete their cycle in about two years. Western blacklegged ticks take closer to three. Between meals, ticks spend the vast majority of their lives sitting in leaf litter or low vegetation, waiting.
How Ticks Stay Hydrated Between Meals
Since ticks may go many months between blood meals, dehydration is a constant threat. They solve this with an unusual trick: absorbing water vapor directly from the air. Ticks secrete a slightly concentrated fluid from their salivary glands onto their mouthparts. This fluid attracts moisture from the surrounding atmosphere, and the tick then swallows the water-enriched liquid using a powerful pharyngeal pump. Specialized water-attracting surfaces on the hypostome may also help condense water from humid air. This mechanism works best in relatively humid environments, which is why ticks thrive in wooded, shaded habitats and tend to die quickly in dry indoor air.
This atmospheric water absorption is the only thing ticks take in besides blood. They don’t eat plant material, dead insects, or any solid food at any point in their lives.