The primary sense organ, Haller's organ, is common to both hard and soft-bodied ticks. There are slight differences in the organ from species to species, but it is generally located on the dorsal surface of the tarsi (leg segments closest to head of the tick). Haller's organ plays a key role in finding hosts as setae on the organ respond to changes in humidity, carbon dioxide levels, and olfactory stimuli. This organ is also important in pheromone detection during mating season. In addition to Haller's organ, these ticks also have many setae on their scutum and legs. Longer, curved setae on the ventral surface aid in chemosensory and tactile responses while shorter, straighter setae act as temperature receptors. Rocky mountain wood ticks have a pair of simple eyes that are more or less parallel to the second pair of legs, just past the head.
Communication Channels: visual ; tactile ; chemical
Other Communication Modes: pheromones
Perception Channels: visual ; infrared/heat ; tactile ; chemical
This species has no special conservation status.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
The life cycle of Rocky Mountain wood ticks is characterized by three stages: larval, nymph, and adult. Progression through these stages can take 1-3 years. Individuals usually take a single blood meal from a mammalian host before progressing to the next stage and the size of hosts increases along with the size of ticks. Host availability may cause variation in timing and duration of mating, ovipositing, egg hatching, molting, and overall growth. The life cycle begins when eggs are deposited on vegetation by engorged females during early summer. Larvae remain inactive until outside stimulation (i.e. temperature, light, humidity) cause them to seek their first mammalian host (usually some sort of rodent). Following a feeding period ranging from 2 to 6 days, larvae drop off and form nymphs via a molting process. Nymphs display behavior similar to larvae, remaining dormant until stimulated by the presence of a potential host. Following attachment to the second host, males and females demonstrate different behaviors. In preparation for mating, females feed on the host for long periods (5 to 15 days) while males feed for shorter periods and spend more time copulating with partially fed females. After females are fully engorged, they drop off their hosts and seek a place to deposit their eggs. Males and females die shortly after completing reproduction.
Development - Life Cycle: metamorphosis ; diapause
One of the important ecosystem roles carried out by Rocky Mountain wood ticks is that they serve as a vector for the tick-borne disease known as Rocky Mountain Spotted Fever (RMSF). Upon biting a host, the tick passes on the disease-causing gram-negative coccobacillus, Rickettsia rickettsii, which is an obligate intracellular parasite and is the true disease-causing agent. Symptoms characteristic of this disease include a rash beginning in the palms of the hands and soles of the feet, fever, nausea, emesis, severe headache, muscle pain, and loss of appetite. Although lethal in some cases, the disease is treatable. Taking antibiotics upon infection, for example, greatly reduces the mortality rate from an alarming 20% chance to a relatively low 5%. Although not known from this particular species, species in the genus Dermacentor are also known to serve as a vector to Tularemia, also known as Pahvant Valley plague or rabbit fever. As with RMSF, this disease is caused by a bacterial endosymbiont (Francisella tularensis), which is also a non-motile gram-negative coccobacillus. What makes this different from RMSF, however, is that it does not rely on direct contact in order to be spread. It can be waterborne, inhaled, or ingested (i.e. poorly-cooked meat).
Negative Impacts: injures humans (bites or stings, causes disease in humans ); causes or carries domestic animal disease
Rocky Mountain wood ticks provide no known economic benefit to humans.
As an obligate parasite, Rocky Mountain wood ticks rely on mammalian blood to provide the nutrition necessary to transition through their various life stages. During their lifespan, these ticks also play an important role as host to various types of bacteria, two of which are Arsenophonus and Wolbachia. Of the two, Wolbachia has a special relationship with many other arthropods and is noted for its ability to alter the reproductive abilities of its hosts by infecting the testes and ovaries. Such infections may result in "male killing" where males are killed during larval development, "feminization" where infected males develop as females or (infertile) pseudo-females, or sometimes leading to the development of parthenogenesis, where females reproduce without coming into contact with a male. The most important effect of hosting Wolbachia, however, is "cytoplasmic incompatibility", where Wolbachia-infected males are unable to reproduce with uninfected females. This has been suspected as a potential cause of speciation. Rocky Mountain wood ticks are also known hosts of Rickettsia bacteria, specifically R. prowazeki and R. rickettsii; infection with these bacteria is most often deadly for Rocky Mountain wood ticks and can be passed to host species as well. Rickettsia rickettsii, for example, is known as a cause of Rocky Mountain Spotted fever, the most common fatal tick-borne disease in humans found in the United States.
Ecosystem Impact: parasite
Species Used as Host:
Mutualist Species:
Rocky Mountain wood ticks are sanguivores (most typically of mammals) who take a single blood meal from their hosts at each of their three life stages.
Animal Foods: blood
Primary Diet: carnivore (Sanguivore )
Rocky Mountain wood ticks are mostly found in arid areas of the Rocky Mountain region (Nebraska, South Dakota, Arizona, New Mexico, etc.) including California, where it is only found east of the Sierra Nevada mountains. They can also be found in various parts of southwestern Canada, including British Columbia, Alberta, and Saskatchewan.
Biogeographic Regions: nearctic (Native )
Adult Rocky Mountain wood ticks are generally found in elevations of 2100 m to 2500 m. Temperature may be important in determining its geographic range as these ticks show a preference for lower elevations (1600 m to 2200 m) at higher temperatures and higher elevations (2350 m to 2500 m) at lower temperatures. This species also prefers brushy areas of foothills and mountains as these areas host small mammals and other host organisms.
Range elevation: 1600 to 2500 m.
Average elevation: 2300 m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: forest ; scrub forest ; mountains
The primary determinant of lifespan for Rocky Mountain wood ticks is the availability of the blood meal required to reach each life stage. Larvae can survive up to a month without a blood meal; however, with a single meal they are able to molt into nymphs, which can then survive upwards of a year before needing another blood meal. With yet another single feeding, nymphs are able to morph into adults, which can survive up to 2 years without feeding. Members of this species will typically live 1-3 years total in the wild. The longest recorded lifespan in captivity for this species is 4 years. Variation in life span may be influenced by external factors such as humidity, temperature, and host availability, which may cause these ticks to be dormant for longer periods of time between life stages.
Range lifespan
Status: wild: 1 to 4 years.
Average lifespan
Status: wild: 3 years.
Range lifespan
Status: captivity: 3 to 4 years.
Typical lifespan
Status: wild: 1 to 4 years.
Average lifespan
Status: wild: 2 years.
Typical lifespan
Status: captivity: 2 to 4 years.
Rocky Mountain wood ticks are generally brown or reddish brown in color. Females have a distinct dorsal silver-gray ornamentation (known as the 'shield') which turns more gray when the tick feeds, while males are spotted gray and white with no distinctive shield marking. Both sexes are mottled in this fashion over portions of their legs and mouthparts (basis capitulum). Their bodies are flat and pear-shaped, ranging anywhere from 2 to 5.3 mm in length, though fully engorged females may reach up to 16.5 mm. This species is sexually dimorphic; in addition to the marking differences mentioned above, females range from 2.8-5.4 mm long (13.8 to 16.5 mm when fully engorged) while males range from 2.1 to 6.1 mm. Body mass ranges from .005 to .7 g. This species is also polymorphic, with a lot of physical variation between individuals. Features that distinguish this species from other ticks include the number and size of goblets (used in aeration/respiration) on its spiracular plates, with this species having 100-200 goblets on average. Females produce a neurotoxin in their oral secretions that prevents the release of acetylcholine, a neurotransmitter necessary for muscle contractions, often causing paralysis even in larger mammals such as dogs and humans.
Range mass: .005 to .7 g.
Range length: 2.1 to 16.5 mm.
Other Physical Features: endothermic ; polymorphic
Sexual Dimorphism: female larger; sexes colored or patterned differently; female more colorful
The main defensive mechanism of this species against typical tick predators such as ants, beetles and spiders is the secretion of allomones, a special set of substances which influence predator behavior in favor of the tick (i.e. discouraging pursuit if following scent). The main component (nearly 25% of mass) of these allomones is squalene, a biochemical precursor to steroids. These allomones are secreted by large wax glands on the underside of the tick's legs. Once depleted, these wax reservoirs take up to 10 days to replenish, a period during which the tick has little defense against predation.
Known Predators:
This species has a polygynous mating system, where males disrupt their adult stage feeding period to begin copulation with partially fed females. Mating occurs in the third and final life stage. Females release 2,6-dichlorophenol during feeding, allowing males to identify them as potential mates. Once females have consumed enough blood, they release cholesteryl oleate, signaling that they are ready to mate. These two chemicals are common to hard ticks (Family Ixodidae).
Mating System: polygynous
These ticks are reproductively active from May through June, with some variation possible due to host availability, temperature, humidity, and other environmental factors. This species is known to have a single breeding season in late spring with adults dying soon after copulation. When grown in ideal conditions in a lab, maturation and reproduction have come to completion in approximately 68 days; in the wild, it takes both males and females approximately a year to reach sexual maturity. Females may lay anywhere between 2500 and 7400 eggs, depending on their nutrition levels, over the course of 10 to 33 days.
Breeding interval: Rocky Mountain wood ticks breed once yearly between the months of May and June.
Breeding season: This species breeds from late spring through early summer.
Range number of offspring: 2500 to 7400.
Average number of offspring: 4000.
Range age at sexual or reproductive maturity (female): 1 to 3 years.
Average age at sexual or reproductive maturity (female): 1 years.
Range age at sexual or reproductive maturity (male): 1 to 3 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: semelparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
Neither males nor females invest in their young beyond females' investments in their eggs.
Parental Investment: no parental involvement; female parental care ; pre-fertilization (Provisioning)
