Ticks are ectoparasitic arachnids of the order Ixodida, and are closely related to mites. They are ecologically significant as parasites and can affect nearly every terrestrial vertebrate animal. All ticks are hematophagous, meaning they consume blood as food, and because of this diet they are vectors for at least twelve known blood-borne diseases.
These small animals are highly specialized as parasites; they have existed since at least the Cretaceous period, and are commonly found in amber. Some evidence suggests that they may have evolved as early as the Triassic period. At least one species, Deinocroton draculi, has been found alongside dinosaur feathers preserved in 99-million-year-old amber; this heavily implies that ticks fed upon dinosaur blood. Ticks can mostly be classified into one of two families: Ixodidae, or hard ticks, and Argasidae, or soft ticks. A third family, Nuttalliellidae, contains only one species (the South African Nuttalliella namaqua) and is considered to be the most primitive of all the ticks.
In Costa Rican Spanish, ticks are called garrapatas.
In order to avoid notice by the host, the majority of ticks are fairly small. They generally reach three to five millimeters in length, though a well-fed tick may appear bulbous and swollen to greater than its usual size.
Like mites, ticks have non-segmented abdomens; in addition, the abdomen of the tick is fused with the cephalothorax, giving the body a round or ovular outline when viewed from above. Unlike other arachnids, the body segments of the tick consist of the capitulum (the retractable mouthparts) and the idiosoma (the remainder of the body, including the brain and eyes).
The capitulum consists of only the mouthparts, which have three components. First is the basis capitulum, which is a support structure for the rest of the organ. Palps are also present, serving as sensory organs. Finally is the hypostome, a straw-like feature that is used to draw blood from the host. In the family Ixodidae, the capitulum projects forward from the body and is often described as being beak-shaped. This beaklike form helps to puncture the host’s skin.
Ixodid ticks can further be differentiated by their protective shell, or scutellum. This covers the whole back of the male, but in the female is considerably smaller. This allows the female’s body to become swollen with eggs. On the other hand, argasid ticks have more pear-shaped, leathery bodies and have their capitulum on the underside, where it is not visible when seen from above.
Ticks do have eyes, which are located on the sides of the body; however, they generally do not rely on eyesight to find hosts. Instead, they use their tactile sense to discern where to attach, and also use the Haller’s organ to detect smell, chemical signals, infrared radiation, and air pressure. Haller’s organs are located on the first leg pair; ticks, like other arachnids, have eight paired legs as adults. Each leg has seven segments and two claws at the end. They breathe through spiracles, which are located between the legs midway down the body.
All ticks go through four stages of life: egg, larva, nymph, and adult. To progress through each stage of life, the tick needs a blood meal. Larvae hatch with only six legs, gaining the final pair when they molt into nymphs. The growth stages differ somewhat between ixodid and argasid ticks; ixodid larvae start out by feeding on small mammals or birds, dropping to the ground once they are full and shedding their skin to become nymphs. The nymphs then feed on larger hosts, molting once more to become adults. The scutellum is reduced in size until the adult stage in the male; in the female it never grows as prominent. In the adult stage, females feed much more than males, who mostly remain on larger hosts to mate with females.
Argasid ticks have longer and slightly more complicated life cycles, molting several more times and going through as many as seven nymph stages. In these ticks, both the males and females feed on equal amounts of blood, and leave the host to mate.
Maturity in ticks may take months to years to complete. In particular, ixodids all take at least a year to fully mature.
Depending on the family, ticks may or may not exhibit sexual dimorphism. In the family Ixodidae, sexual dimorphism is fairly prominent; males are completely covered by the shell-like scutellum, while in females, the scutellum is reduced to a small plate in the capitulum. In the family Argasidae, sexual dimorphism is much less noticeable, and merely consists of the location of the reproductive organs.
Ticks are found in most parts of the world, but are most common and successful in warm and humid regions such as Central America. They need moisture in order to metamorphose, and colder temperatures can harm their eggs. Species of ticks are distributed alongside their host species, but many inhabit areas of tall grass and woodland where they may more easily attach to hosts without being noticed. Migratory birds may carry them far outside of their original range.
Ixodid ticks have no dwelling place other than their host, while argasid ticks make their living in small spaces where they will return after feeding.
These arthropods are common throughout the world and are some of the most notorious parasites in the Americas in particular. Over millions of years, they have evolved to suit particular hosts, so the species of ticks found in a given region depend on the host species also found there. For example, Costa Rica has numerous species of ticks, and those found on its offshore islands such as Isla Nublar and the Muertes Archipelago are naturally those that affect its indigenous animal life. Brown pelicans, found commonly in this region, are affected by seabird ticks belonging to the genera Carios and Ornithodoros, which likely impact other seabirds that migrate to and from the island as well as birds that live there year-round. Meanwhile, nearly all boa constrictors found in northern South America bear the tick Amblyomma dissimile, and occasionally Amblyomma rotundatum. Mammals are also found on Isla Nublar, including native species including mantled howler monkeys, collared peccaries, and the endemic Nublar tufted deer as well as introduced species such as cattle, pigs, goats, and rats. Ticks that are found on these mammals include members of the genera Dermacentor, Amblyomma, Otobius, Rhipicephalus, Hyalomma, Boophilus, Haemaphysalis, Ixodes, and others. Because some of the animals found on the island are endemic, there is a good possibility that some tick species were endemic as well.
Most of these islands are superb habitats for ticks, which flourish in warm humid environments like the mist-shrouded tropical mountains and sun-drenched valleys of Isla Nublar and Isla Sorna. Dense undergrowth is present all over these islands, giving native ticks many places to hide in wait of passing hosts. Isla Sorna is a larger island than Isla Nublar and has a more diverse range of habitats, from the redwood and pine forests of the northeast to the central tidal rivers and wet western jungles. Grasslands and mountains abound throughout, and fields of tall elephant grass provide excellent habitat for ticks to hide in wait for passing hosts. This diverse group of arachnids would be able to thrive in most of Isla Sorna’s habitats. In Eric Kirby‘s account of Isla Sorna in the junior novels Survivor and Prey, ticks are among the small invertebrates mentioned as inhabiting the island. This would imply that some of the species found on Isla Sorna use humans as hosts. Most, however, infest birds, reptiles, and amphibians, and they are probably found on all islands in the Gulf of Fernandez.
Invasive ticks are mostly caused by the introduction of livestock or other domestic animals to new regions, and the expansion of suitable tick habitats. Climate change can lead to areas becoming warmer and more humid, allowing for tick populations to boom. The islands in the Gulf of Fernandez are an interesting example of introduced animals impacting the number and species of ticks in an ecosystem. Humans historically inhabited the islands for thousands of years, introducing mammalian livestock (in the form of goats) to Isla Nublar. In more recent times, larger livestock such as cattle and pigs as well as invasive brown rats were introduced to the island, and to a lesser degree Isla Sorna.
De-extinction caused massive changes to the islands’ ecology as new animals found nowhere in the modern world were introduced to the ecosystems. Isla Sorna was less developed than Isla Nublar, being used as a research and testing facility rather than a fully-functional theme park, so on Isla Sorna the de-extinct animals were more directly involved with the ecosystem. The first animals were cloned on Isla Sorna in 1986, and some were moved to Isla Nublar in 1988. Parts of Isla Nublar were destroyed and rebuilt during this time, decreasing native animal habitat, but the massive de-extinct creatures introduced in their place would have made excellent hosts for huge numbers of ticks. The new animals were mostly dinosaurs, so the bird- and reptile-infesting ticks probably thrived on them.
Isla Nublar was abandoned for several years after 1993, and Isla Sorna was abandoned not long after; the latter island experienced an ecological catastrophe in the early 2000s in which most of the de-extinct life died out. Ticks that had fed on these animals would have become less common. However, many of the animals were relocated to Isla Nublar as that island was built up even further; after a few years of animals being shipped back and forth, plus more Isla Nublar construction, nearly all the animals were housed in captivity on Isla Nublar. While ticks would have thrived between 1994 and 2002, after this point the animals were cared for by Jurassic World staff as the field of paleoveterinary science advanced. For the next ten years, park staff used environmentally-friendly anti-tick sprays and other medicine to keep parasites away from the animals. Between veterinary care and the continued decrease in natural habitats on the island, the tick population here probably dwindled, while the Isla Sorna population is mostly uncontrolled.
After Jurassic World’s closure in 2015, animals were allowed to roam into the wild, establishing a strange kind of unstable ecology on the island. Although the animal population was initially high, environmental conditions and overpopulation caused them to steadily decline. A boom in the tick population probably occurred initially but decreased alongside the populations of their hosts. Volcanic activity began to plague the island in early 2017, culminating with a disastrous eruption on June 23, 2018 which did not subside until 2022. The terrestrial animals of Isla Nublar were largely eliminated, some having been poached while the rest died in the eruption or its aftereffects. With the megafauna extinct, only seabird ticks and those that feed on small, opportunistic survivors such as rats still have hosts on Isla Nublar.
Behavior and Ecology
Ticks, depending on the species, may be active at many times of day and night. They are not primarily visual, instead relying on chemical and tactile cues to move about. Their behavior is highly regulated by that of their hosts, but once they are attached, ixodids may remain in place feeding for days or weeks at a time while argasids usually feed for only a few minutes.
In general, ixodids engage in “questing” activity (seeking hosts) during the day while argasids bite their hosts during the night, but these are not strict guidelines for tick behavior.
Diet and Feeding Behavior
All tick species are obligate hematophage ectoparasites, meaning they cannot survive without a host from which they drink blood. While they can go long periods of time without feeding, they are unable to molt without a blood meal, so they must feed in order to mature. The preferred hosts and exact feeding strategies of ticks vary from one species to another, but follow a similar general pattern.
Ixodid ticks are long-term feeders. To find a host, most ixodids will position themselves in tall grass or dense foliage and reach two legs outward. When they feel something brush against their perch, they will grab onto it, crawling about on the surface of the skin in search of an ideal place to attach. The tick, once it finds a suitable spot, will use its mouthparts to pierce the skin and insert its hypostome to drink blood. In ixodid ticks, the bite is painless due to the small size and specialized anatomy of the tick, so the host may not even notice. These species will stay embedded in the host’s skin until they are full, which may take weeks. Ixodid ticks actually grow new cells to accommodate their expanding bodies during feeding; a full meal may see the tick increase its weight by as much as six hundred times.
On the other hand, argasid ticks will come out when their hosts are resting, often at night, and deliver a painful bite that lasts only a few minutes before the tick detaches and leaves for the safety of its home.
Ticks are not naturally social animals, approaching one another only to mate. It is fairly common to find large numbers of ticks all in once place (unfortunate animals that stumble across such places may find themselves infested with dozens or even hundreds of ticks all at once), but this is not due to a social tendency. Instead, an ideal habitat may simply attract huge groups of ticks that are all seeking hosts at once.
Adult ixodid ticks will usually mate on their hosts; this is the main reason that the male, who does not feed as much as the female during adulthood, remains on the host. Because he keeps himself in this risky position in order to find mates, his exoskeleton has evolved to include a carapace-like scutellum which protects him. Sex roles are less gendered in argasid ticks, which exhibit very little sexual dimorphism and both feed on larger hosts as adults. Argasids leave their hosts to mate, because they do not usually remain attached for more than a few minutes when feeding.
An adult female tick may lay around three thousand small, spherical eggs in a single sitting. The incubation period differs between species, but no parental care is provided; the larvae are able to seek out hosts and feed shortly after hatching.
Ticks do not make any noises to communicate, and beyond using chemical signalling to locate mates, they do not communicate with one another in any noticeable way.
All ticks are parasites. Ixodids remain painlessly attached to their hosts for days or weeks at a time, while argasids scurry out while their hosts sleep to deliver a bite, drink for a few minutes, and retreat. In both cases, the interaction can be unpleasant for the host; argasid bites tend to be painful, and ixodids remain attached for long periods of time and can be a nuisance. More worryingly, many tick species can harbor blood-borne pathogens that they pick up from infected hosts. These can include bacteria, viruses, and other microorganisms that cause diseases such as Rocky Mountain spotted fever, Lyme disease, typhus, rickettsialpox, and others. One tick may contain multiple pathogenic microorganism species.
The hosts of ticks are also very diverse, and include all terrestrial vertebrate animals. Ticks are known from mammals, birds, reptiles, and amphibians. Coevolution between ticks and their hosts has resulted in a great diversity of tick feeding strategies, as well as defense mechanisms employed by the hosts. The relationship between ticks and hosts goes back at least 120 million years; the earliest currently-known ticks are believed to have been parasites on feathered animals, so birds and other theropod dinosaurs would have been common hosts. In the Genetic Age, de-extinct dinosaurs are affected by modern species of ticks, which have the deleterious effect of introducing diseases that the dinosaurs’ immune systems have no defenses against.
In rare cases, tick infestation can lead to a condition called tick paralysis. This is the only disease spread by ticks that is not a result of a blood-borne organism. There are at least forty-three species of ticks that can cause this condition, which is brought on by neurotoxins in the tick’s saliva. In North America, the best-studied species that cause tick paralysis are the American dog tick (Dermacentor variabilis) and the Rocky Mountain wood tick (Dermacentor andersoni), the latter of which is commonly found in the region of Western North America were numerous dinosaurs were released into the wild on June 24, 2018. Without paleoveterinarians to remove ticks, this condition could be fatal within days.
There are predators of ticks, however. Certain mites and nematode worms prey upon them, and small vertebrates such as lizards and birds may feed on ticks as well. Some birds will even pluck ticks from the bodies of larger animals, also feeding on blood that leaks from the fresh wound. Several species of birds found in the Gulf of Fernandez are frequently seen alongside herbivorous dinosaurs, sometimes even perching on them, and may potentially serve to remove ticks from these animals. Ticks of many genera are used as hosts by the parasitoid wasp Ixodiphagus hookeri, which is found worldwide except for Antarctica. This wasp uses a symbiotic bacteria, Wolbachia pipientis, to weaken the immune system of the tick before laying its egg into the tick’s body; the egg hatches after a time and the larva feeds on the blood the tick has consumed before killing the tick as it emerges.
Well-known parasites, ticks are frequently used as metaphors for social or economic forms of parasitism. This occurs in literature, political cartoons, and other forms of media. While ordinary people are more likely to use ticks to describe unwanted guests and those who take advantage of others, wealthy people in capitalist or corporatist societies commonly use ticks to describe the poor.
Ticks are sometimes kept for medical research, but hardly ever long-term. This is because of the need to provide them with a diet of fresh blood, which they can only consume from a host. Keeping animals specifically as tick hosts is unethical, and few human volunteers can be found, so ticks are generally collected from the wild and kept for observation and study until they expire. Care should be taken not to allow any to escape, particularly if they are being studied for the dangerous diseases they are harboring.
Many diseases carried by microorganisms in ticks are medically significant to humans and livestock, so scientific study of these parasites and their microbiomes is beneficial to civilization. Wildlife ecologists, pathologists, microbiologists, and scientists of various other disciplines all study the spread and impact of ticks, as well as patterns that regulate their behavior. The main goal of tick research is to determine how best to prevent overpopulation and to reduce the rates of infection, both in bite victims and the ticks themselves.
While tick population control is so far still experimental (other than the use of traditional chemical and biological control agents), some headway has been made into means of controlling the spread of diseases. For example, the blood of the western fence lizard (Sceloporus occidentalis) contains a protein that is fatal to Borrelia, the bacterium which causes Lyme disease. When ticks feed on the blood of the western fence lizard, they effectively purge this bacterium from their bodies, and are no longer vectors for Lyme disease.
Like all ecological problems, ticks do not respect national borders and will occur in any suitable region that they are capable of entering. They may arrive in new areas by hitching rides on animals such as livestock and migratory creatures, making it impossible to completely bar their entry into a country. However, some efforts can be made to mitigate their impact and keep them under control. Inspecting livestock and pets and providing for their health can help reduce the amount of ticks being accidentally imported and exported between areas where animal trade occurs. Ensuring healthy ecology can also reduce tick numbers by bolstering the populations of animals that feed on ticks.
Climate also plays a role in tick populations. Mild winters can allow large numbers of the ticks’ preferred hosts to survive, which will then result in larger numbers of ticks as well the following spring and summer. The ticks themselves benefit from warm weather and flourish when climate trends favor warm conditions. Over time, this has caused ticks carrying diseases such as Lyme to spread farther north, into areas where the disease was not as prevalent before. This is particularly impactful in the United States, where the fossil fuel industry holds a large amount of political power and climate change denialism is espoused as a result. The United States also has underdeveloped healthcare and poor ecological management practices, making it especially vulnerable among developed countries.
In terms of de-extinction, ticks are significant as a source of diseases that de-extinct animals may not have defenses against. While ticks did exist in at least the Cretaceous period of the Mesozoic era (and could have been used by InGen to obtain ancient DNA), the diseases borne by Cretaceous ticks are likely very different from those borne by ticks in the modern day. In Jurassic World, paleoveterinarians would be on site at all times to inspect dinosaurs for signs of infestation; anti-tick medications were used to deter the arachnids from attaching. In more recent times, anti-tick sprays have become ecologically friendly, ensuring that deterring ticks did not otherwise negatively impact Isla Nublar’s ecosystem. The Dinosaur Protection Group also prepared for the possibility of ticks infecting dinosaurs at any location that the animals might be safely transported, and promoted the use of the aforementioned anti-tick sprays as well as a more traditional manual inspection of each animal.
Many of the species of mammal-infesting ticks can be parasites on humans. These parasites can spread disease to humans by biting, introducing microorganisms that can then wreak havoc on the body.
However, humans are exceptionally capable of fighting tick infestations. Like many primates, their increased social behaviors allow them to inspect one another, and humans have access to specialized tools that can be used to remove ticks from the body. Medicine has been developed to combat the diseases that ticks may spread, though there are still many tick-borne diseases that cannot be cured and have lifelong impacts. Like with mosquitoes, solving the problem of tick-borne disease often comes down to removing the populations of ticks themselves.
When removing a hard tick, use tweezers or narrow forceps to grasp it by the “head” (the area near the front of the body behind the beak-like mouthparts) and pull straight out. If it is not pulled cleanly out, the mouthparts may break and remain lodged in the skin; take care to remove these, as they can cause infection of they stay embedded. Unlike mosquitoes, which are lightweight and will probably be gone before you know they have bitten, ticks are slow-moving and take time to locate a suitable feeding site. After any foray into wooded areas, especially in spring and summer, look yourself over for ticks seeking out places to bite; you may be able to remove most or all of them before they settle in. Be sure to check places you might normally not look, or have another person check places you cannot see yourself. They will try to attack wherever they can go unnoticed. Also check your clothing for ticks, and wash your clothes thoroughly if you believe any may be hiding there. Ticks that you remove should be killed; burning, suffocation, or crushing are the recommended methods to ensure the parasites actually die. Drowning is ineffective and not recommended.
If any ticks have bitten you, and you live in a disease-affected area, it may be pertinent to keep the tick preserved (for example in a vial or sealed bag, or simply stuck to a piece of tape). Be vigilant for any unusual symptoms occurring near the site of the bite, such as discoloration of the skin. If you show symptoms of disease, immediately see a medical professional and show them both the symptom and the preserved tick; this will help them diagnose the infection and provide you with the proper medication. While some tick-borne diseases can be life-altering or fatal, many can be stopped in their tracks with medicine before the devastating effects occur and are irreversible.