Tick species are widely distributed around the world, but they tend to flourish more in countries with warm, humid climates, because they require a certain amount of moisture in the air to undergo metamorphosis, and because low temperatures inhibit their development from egg to larva. Ticks of domestic animals are especially common and varied in tropical countries, where they cause considerable harm to livestock by transmission of many species of pathogens and also causing direct parasitic damage.
For an ecosystem to support ticks, it must satisfy two requirements: the population density of host species in the area must be high enough, and humidity must be high enough for ticks to remain hydrated. Due to their role in transmitting Lyme disease, ixodid ticks, particularly I. scapularis, have been studied using geographic information systems (GIS), to develop predictive models for ideal tick habitats. According to these studies, certain features of a given microclimate – such as sandy soil, hardwood trees, rivers, and the presence of deer – were determined to be good predictors of dense tick populations.
Ticks satisfy all of their nutritional requirements as ectoparasites, feeding on a diet of blood in a practice known as hematophagy. They are obligate hematophages, needing blood to survive and move from one stage of life to another. Ticks unable to find a host to feed on will die. This behavior is estimated to have evolved approximately 120 million years ago through adapative pressures to a blood-feeding environment. Evidence suggests this behavior evolved independently in the separate tick families, with differing host-tick interactions driving the adapative change.
Ticks extract the blood by cutting a hole in the host's epidermis, into which they insert their hypostome, and keep the blood from clotting by excreting an anticoagulant or platelet aggregation inhibitor.
Ticks find their hosts by detecting animals' breath and body odors, or by sensing body heat, moisture and vibrations. They are incapable of flying or jumping, but many tick species wait in a position known as "questing". While questing, ticks hold on to leaves and grass by their third and fourth pair of legs. They hold the first pair of legs outstretched, waiting to climb on to the host. When a host brushes the spot where a tick is waiting, it quickly climbs onto the host. Some ticks will attach quickly while others will wander looking for thinner skin like the ear. Depending on the species and the life stage, preparing to feed can take from ten minutes to two hours. On locating a suitable feeding spot, the tick grasps the skin and cuts into the surface.
Like all arachnids, adult ticks have eight legs. The legs of Ixodidae and Argasidae are similar in structure. Each leg is composed of six segments: the coxa, trochanter, femur, patella, tibia, and tarsus. Each of these segments is connected by muscles which allow for flexion and extension, but the coxae have limited lateral movement. When not being used for walking, the legs remain tightly folded against the body. Larval ticks hatch with six legs, acquiring the other two after a blood meal and molting into the nymph stage.
The best way to remove an adult tick is by freezing it off with a medical wart remover or the like. Mechanical removal with household tweezers is contraindicated as it may result in squeezing of the contents of the tick into the bloodstream.
To facilitate prompt removal, fine-tipped tweezers can be used to grasp the tick as close to the skin as possible and detach it by applying a steady upward force without crushing, jerking or twisting, in such a way as to avoid leaving behind mouthparts or provoking regurgitation of infective fluids into the wound. Proprietary tick removal tools are also available. It is important to disinfect the bite area thoroughly after removal of the tick. The tick can be stored and, in case of signs or symptoms of a subsequent infection, shown to a clinician for identification purposes together with details of where and when the bite occurred. If the tick's head and mouthparts are no longer attached to its body after removal, a punch biopsy may be necessary to remove any parts that have been left behind.