Tyrannosaurus rex (S/F)

Disambiguation Links – Tyrannosaurus rex (S/F-Ride) Tyrannosaurus rex (C/N)Tyrannosaurus rex (CB-Topps)Tyrannosaurus rex (JN)

The “tyrant reptile king” was first described by Henry Fairfield Osborn in 1905 from a partial skeleton found in eastern Montana. Tyrannosaurus was a bipedal carnivore that lived in the Late-Cretaceous Period about 68 to 65.5 million years ago. Tyrannosaurus rex represents perhaps the most well-known group of dinosaurs, the tyrannosaurids. This theropod was widespread across North America, with known fossil sites including the Hell Creek Formation (Montana, South Dakota, and North Dakota), the Livingston Formation, Ferris Formation, and Lance Formation (all in Wyoming), the Laramie Formation, Denver Formation (Colorado), the Javelina Formation (Texas), the McRae Formation (New Mexico), and North Horn Formation (Utah), all in the United States, as well as the Scolland Formation (Alberta) and Frenchman Formation (Saskatchewan), both in Canada. T. rex was the apex predator of its environment. It mainly hunted ceratopsians and hadrosaurs. Evidence of predation include part of the caudal vertebrae (tail bones) of an Edmontosaurus being bitten off and healed, as well as Triceratops horns being broken off and healed.

Sometime between 1985 and 1988, InGen succeeded in cloning Tyrannosaurus rex. While at least seven were originally cloned and at a few bred in the wild, most of the attention was devoted to the individual shipped to Isla Nublar for Jurassic Park in the 1990s. Ultimately, this specimen would end up having the longest confirmed lifespan of any of InGen’s animals. As of June 11, 1993, InGen had created only Version 1.0 of this animal.

Description

The largest-known of the tyrannosaurs, Tyrannosaurus rex was also the third-largest theropod cloned by InGen (slightly smaller than Spinosaurus, and significantly smaller than the projected adult size for the artificially-created Indominus rex). This animal grows to 12.3 to 13 meters (40 to 42 feet) long, 3.5 meters (12.5 feet) tall at the hip, and weighs between seven and twelve tons as an adult. A single exceptional female has been reported at up to 44 feet in length, exceeding known dimensions of fossil specimens.

Much of its bulk consists of its massive head, with gaping jaws that can open at an eighty-degree angle and clamp down with a bite force of 34,000 Newtons. The teeth are equally huge, reaching seven inches in length and featuring jagged serrations on the inner edge. The tooth tip is designed to puncture, not tear, and the serrations allow bacteria to flourish within its jaws. Lost teeth are replaced throughout its life. Its tongue is extremely muscular and, unlike what is known from the fossil record, highly dexterous. It is long and triangular, capable of extending outside of the mouth, which the tyrannosaur may use to try and extract prey from tight spaces. Above the eyes, it possesses bony protrusions; the male also has a bumpy keratinous growth on the snout.

Eye of a female T. rex reacting to light

The eyes are large, with yellow sclerae and round black pupils. The Tyrannosaurus has stereoscopic binocular vision, but is incapable of differentiating between stationary objects and a stationary background. This was in line with paleontological theory as of 1993 (though no such theories have ever existed in real life), but Dr. Laura Sorkin hypothesized that this disability was actually the result of DNA from frogs used to replace decayed segments of Tyrannosaurus genome by Dr. Henry Wu. Whatever the cause, the animal can still detect nearby animals using its excellent sense of smell; according to Drs. Sarah Harding and Robert Burke, the olfactory cavities of the Tyrannosaurus are surpassed in size only by those of the turkey vulture (Cathartes aura), and the tyrannosaur’s sense of smell covers an area with a radius of ten miles. It also has excellent hearing, demonstrated by a mated pair on Isla Sorna which were able to hear the sounds of their wailing infant from several miles away despite the sound of an approaching storm. It also has excellent hearing, according to the Jurassic World Facts mobile application; it is able to hear low-frequency sounds.

Typical footprint of a Tyrannosaurus rex. (Image from the Dinosaur Protection Group)

In addition to immensely powerful jaws, the limbs of Tyrannosaurus are also very muscular. Its massive legs allow it to run at a maximum speed of 32 miles per hour, though only for short bursts; it typically runs at a slower speed, estimated at slightly under 25 miles per hour according to the InGen IntraNet website. The feet have three toes, each of which has a large hooked talon. These give it traction, enabling it to run efficiently on both soil and vegetation; its toes can also spread apart to prevent it from sinking in mud. The arms are very small, a compensation for its enormous head. Despite this, the overall massive size of the Tyrannosaurus means that its proportionally weak arms can still lift up to five hundred pounds. The hands have two fingers each, which terminate in sharp claws. As with all InGen’s theropods, the hands are pronated, which is a phenotypic error not present in fossil specimens.

The tail is lengthy, which helps counterbalance the head. It lacks any distinguishing features and is mostly used for balance while running. While it is somewhat more flexible than those of fossil specimens, it is not suitable for use in combat. It may knock aside smaller animals, but only by accident, as the tail cannot flex far enough for the tyrannosaur to see what it is doing with it.

Sample of T. rex urine in a laboratory flask. The light yellow color suggests good hydration.

Coloration consists of earthy tones, usually with some striping on the snout. The male and female have very different coloration, but both are suited for camouflage in a forest environment. It has thick, scaly skin, with even the infant lacking feathers. An adult described in the Jurassic Park Adventures junior novel Survivor, the canon status of which has not been confirmed, appears gray in color with red splotches.

Unlike modern birds, the Tyrannosaurus secretes liquid urine which appears pale yellow in color.

Growth
Subadult male T. rex. Note the lighter green coloration in comparison to a fully mature adult, Isla Sorna (6/18/2001)

The infant and subadult stages of the male have been observed, but only the adult and senescent stages of the female have been observed. Infants appear to grow much more quickly than fossil evidence would indicate, likely due to genetic manipulation; a months-old infant in May 1997 was observed at a noticeably larger size than it would have been had it grown at a natural rate. This infant male could be seen to have a proportionally shorter snout, but already had the prominent brows and raised snout of the adult. Its coloration was a mixture of green and brown, ideal for camouflaging in a forest environment, with darker striping on its back.

According to the Jurassic World Facts application, juveniles have more narrow, pointed teeth than adults do; the application claims that adults have thicker and more rounded teeth.

Demonstration of senescence in a female T. rex. Upper image is a 5-year-old under the influence of growth-enhancing substances and a lifetime in captivity (6/12/1993); lower image is the same animal at age 27 after thirteen years in captivity (12/19/2015).

The subadult male seen in 2001 was proportionally much like the adult animal, but the coloration was noticeably a brighter shade of green. This shift from camouflaging green-and-brown to a vibrant green to the final coloration of dark green with yellow striping indicates that, despite their visual disabilities, InGen’s Tyrannosaurus do have excellent color vision and use bodily coloration as a form of signalling health and maturity. Both the adult male seen in 1997 and the subadult male seen in 2001 could be seen to have scarring on the right side of the muzzle. Males typically use deeper vocalizations than females, but females are not incapable of making these same sounds.

In females, only the adult and senescent stages have been demonstrated. The senescent female is generally thinner than the mature adult, with tighter skin and paler coloration. In particular, the stripes of the female appear to fade with senescence. Otherwise, both of these growth stages appear rather similar.

Sexual Dimorphism
Female (left) and male (right) T. rex adults. In the lower center is a juvenile male.

The most straightforward way to tell the difference between a male and female Tyrannosaurus is by bodily coloration. Females appear an earthy brown color, though they may have brown or gray striping on the back as well as the snout. Males, on the other hand, are green in color; in the subadult stage, they are a more vibrant shade, but become darker with maturity. Like the female, the male has striping on the back and snout, but it appears dark green in the subadult and pale yellow in the mature adult.

In addition, the male can be told apart by its skull ornamentation. The male’s brows are more prominent than those of the female, and the snout is adorned with a rugged keratinous growth. On the neck, the male can be seen to have a throat wattle. In males, scarring on the face is common, as are broken and missing teeth; this indicates a greater degree of combative behavior in males, though it is not known whether this is interspecific (conflict with other species) or intraspecific (conflict with others of the same species). Females, however, appear able to attain a larger size.

Habitat
Preferred Habitat
Tyrannosaurus rex hunting two Gallimimus bullatus on Isla Nublar. Image from the Dinosaur Protection Group.

In nearly every case, Tyrannosaurus rex favors the edges of forests as its habitat. This permits it to hide its bulk among plant growth, where its coloration helps it camouflage. From here it hunts via ambush. Nesting and feeding both occur in forested areas;  it will typically drag prey to a suitable area to eat. However, it is quite comfortable in the open; it is a very exploratory animal by nature, and often ventures into habitats that are not its typical hunting ground. However, it nearly always hunts from the cover of forested regions.

In the game Jurassic World: Evolution, the Tyrannosaurus requires 21,100 square meters of grassland and 5,200 square meters of forest in its habitat to be comfortable.

Isla Nublar

InGen constructed a paddock for Tyrannosaurus rex on Isla Nublar in a heavily-forested area. Despite being one of the island’s largest paddocks, it was intended to house one adult and one juvenile animal only; the juvenile did not reach the island before the incident occurred. In 1989, a one-year-old female Tyrannosaurus was introduced to the paddock, where she would remain for the next four years of her life.

Paddock range (red) of T. rex on Isla Nublar (prior to June 11, 1993)

On June 11, 1993, Jurassic Park’s power grid was sabotaged by a disgruntled employee, permitting the island’s only Tyrannosaurus to breach containment. The animal established new territory first in a westward direction, then northward. The 1994 survey carried out by InGen personnel reported on October 5 that the tyrannosaur had claimed the entire island as territory.

Known (red) and hypothetical (purple) range of T. rex on Isla Nublar on and after June 11, 1993 and before April 19, 2002

Under Masrani Global Corporation, InGen reclaimed Isla Nublar in 2002. On April 19, Week 3 of the operation, the tyrannosaur was recaptured by Vic Hoskins and InGen Security personnel. She was eventually held in Paddock 9 of Jurassic World, where she was exhibited in an attraction called T. rex Kingdom.

In addition, any surviving Tyrannosaurus from Isla Sorna were collected by InGen and transported to Isla Nublar in 2004. They were not exhibited in Paddock 9, but rather were held in a separate nearby paddock. The Jurassic World website’s IMAX Theater page describes subadult male tyrannosaurs, suggesting that at least two subadult males were present on the island in 2014 when the website went live. DNA belonging to Tyrannosaurus was in stock in the Hammond Creation Laboratory, where dinosaurs would be hatched; the Jurassic World website implies that Tyrannosaurus were actively being hatched during the park’s operational years. If any survived infancy, it is most likely that they would have been placed in the separate holding pen near Paddock 9 and the IMAX theater.

On December 18, 2015, Jurassic World technician Lowery Cruthers opened the Paddock 9 maintenance gates, permitting the park’s Senior Asset Manager Claire Dearing to lure the now-senescent female out of her paddock. After driving the escaped Indominus rex to its death in the Jurassic World Lagoon, the tyrannosaur made its way eastward to the forest. The island was abandoned by Masrani Global due to the incident, leaving the Tyrannosaurus to claim Sector 3 as territory and abandoning any remaining animals in the holding pen to starve. As of June 2016, she was still inhabiting Sector 3, being sighted on Main Street.

According to books released in promotion of Jurassic World: Fallen Kingdom, only the one female remained alive on the island in 2018. Despite competition for food and territory with numerous other large carnivores, the animal had survived up until the June 23 eruption of Mount Sibo; she was found to have migrated north, toward the volcano. During the eruption, she was driven toward the East Dock, where she was captured by mercenaries employed by Eli Mills under the direction of Ken Wheatley. From here, she was removed from Isla Nublar by means of the S. S. Arcadia.

Isla Sorna

The earliest-known date for Tyrannosaurus rex being hatched on Isla Sorna is 1988, when the animal destined for Jurassic Park was hatched. As of InGen’s last population survey reported in 1993, there were six Tyrannosaurus rex living on Isla Sorna, meaning that a total of seven had survived up until that point.

Dr. Robert Burke identifies fresh Tyrannosaurus rex footprints near a game trail, Isla Sorna (5/23/1997)

John Hammond continued to monitor populations on Isla Sorna for the next four years. Tyrannosaur populations appeared concentrated in the island interior, near the central channel, based on thermal readings in early 1997. On May 23, 1997, fresh Tyrannosaurus tracks were found at Isla Sorna’s northeastern game trail, confirming that tyrannosaurs were hunting there. A nest with a single infant male, estimated by Roland Tembo to be a few months old, was located in the forest several miles south of the game trail. Its mother and father hunted in the surrounding area.

 

Known (red) and hypothetical (purple) range of T. rex on Isla Sorna. Known range is prior to May 23, 1997; hypothetical range is extrapolated from 2001 and later.

The 1997 Isla Sorna incident altered the perceived territory of the tyrannosaur family involved, resulting in them no longer considering their nesting area safe. They first began defending the northeastern cliffs in a territorial manner after their infant was brought there, but then tracked the InGen “Hunter” team inland toward the Workers’ Village. Following the incident, the family remained a few miles north of this area, being sighted in the northern-central part of the island.

Known (red) and hypothetical (purple) range of T. rex on Isla Sorna as of May 25, 1997. Hypothetical range is extrapolated from 2001 and later.

While their film-canon status has been left ambiguous, the Jurassic Park Adventures junior novels have described several additional tyrannosaurs on Isla Sorna. Eric Kirby encounters one on May 23, 2001 on the western coast of the island; he later encounters a female in sickly condition at some point in June somewhere south of the tanker truck that he would eventually inhabit. This individual was possibly killed by a large Velociraptor pride. Finally, later in June, he witnessed one animal at a location south of the tanker truck. He would eventually obtain urine from one of the animals in that area, using its scent to frighten away smaller carnivores.

A subadult male was encountered north of the airfield on Site B on June 18, 2001. It was subsequently killed during a territorial dispute with a Spinosaurus. There has been some speculation that this was the male encountered in 1997 due to near-identical facial scarring, but this is highly unlikely due to the subadult’s vibrant coloration and slightly smaller size. It has also been speculated that this was the same animal that hatched in 1997, but this has not been officially confirmed.

In further Jurassic Park Adventures junior novels (which, again, have ambiguous canon status), a green theropod is partially seen on the western island. As subadult Tyrannosaurus are the only large theropods confirmed to have this particular shade of body coloration, this presumably was a subadult tyrannosaur. Later, a Tyrannosaurus is encountered in that same area, possibly the same individual.

With these sources combined, all six Tyrannosaurus initially known on Isla Sorna are accounted for:

  • Adult male encountered in 1997
  • Adult female encountered in 1997
  • Gray, red-spotted individual encountered in 2001
  • Adult female encountered in 2001; possibly deceased
  • Subadult male encountered in 2001; deceased later that year
  • Subadult male encountered in 2002

Additionally, a seventh adult female would have been transported to Isla Nublar in 1989, and a male was hatched sometime prior to May 1997. It is not known if any others were bred on the island following its abandonment.

Known (red) and hypothetical (purple) range of T. rex on Isla Sorna following interference by InGen under Masrani Global Corporation during 1998-1999. Known range is as of June 18, 2001; hypothetical range is extrapolated from May 25, 1997 and dates following 2001.

In 2004, Isla Sorna suffered an ecological catastrophe as a result of its burgeoning population; this had been hastened by the interference of Masrani Global Corporation, which illegally bred animals on the island between 1998 and 1999. Any surviving Tyrannosaurus would have been collected and transported to Isla Nublar in 2004, where they remained.

Other

In the very early morning of May 25, 1997, an adult and juvenile male were transported to San Diego, California by InGen under the direction of Peter Ludlow. The juvenile was brought by airplane to the Jurassic Park: San Diego construction site, while the adult was transported to the InGen waterfront complex via the S. S. Venture 5888 after being airlifted out of central Isla Sorna just north of the Workers’ Village. The male was unintentionally overdosed on naltrexone after having already overdosed on carfentanyl, and broke free of confinement; he was then confined within the ship’s cargo hold until it collided with the dock at the waterfront. InGen personnel then unknowingly released him from the ship, allowing him to roam the city in a confused state. He was lured back to the ship by Drs. Ian Malcolm and Sarah Harding, using the infant’s distress calls to draw him into the cargo hold. From here, both males were transported back to Isla Sorna.

T. rex would reach California again on June 23, 2018, this time at the behest of Eli Mills. The sole surviving Tyrannosaurus was transported via the S. S. Arcadia to Benjamin Lockwood‘s estate just outside of Orick, California. She remained there for the night and was released in the early morning of June 24 by Maisie Lockwood. She ventured away into the forest. She was last seen breaking into a zoo, engaging in a territorial display with a lion.

Behavior and Ecology
Daily Activity

While the Tyrannosaurus is primarily active during the daytime, it may become active at any time, meaning it is cathermal. During the 1993 incident, the tyrannosaur engaged in exploratory and playful behavior at dusk and shortly after sunset, and engaged in hunting behavior shortly after. It also engaged in hunting behavior throughout the following day: it had a meal late in the morning, but fed again around midday; a third time, it attempted to hunt in the evening. It was again spotted hunting at dusk that day. During the third day of the incident, it hunted at dawn.

During the 1997 incident, the tyrannosaurs’ behavior was drastically impacted by human interference and thus data may be unreliable. They were seen acting primarily at night, engaging in territorial behavior against the invading human presence. The infant, however, was seen feeding during the day. After being released back into the wild, the tyrannosaur family was observed to be active during the daytime, engaging in social behavior.

In 2001, observed tyrannosaur activity was mostly diurnal. The junior novels describe one tyrannosaur engaging in territorial patrolling activity during the day, with another eventually being observed hunting at dusk. Another, in a later book, appears hunting at dawn. During the 2001 incident, a subadult male was seen feeding and resting during the daytime.

Tyrannosaur behavior was also heavily modified by humans in Jurassic World, where T. rex Kingdom featured a feeding show every two hours. The earliest show was at 8:00 AM, when the park opened for the day; this would mean feeding occurred until 10:00 PM, when the park closed. In all, the Tyrannosaurus was fed seven times each day. This individual was apparently awake and alert late at night on December 18, 2015, and also early in the morning the following day; on both occasions, it was establishing territory. Further territorial and hunting behavior was observed in the early afternoon during the eruption of Mount Sibo on June 23, 2018; the animal was also active late that night due to human interference and then the following morning, where she exhibited exploratory and territorial behaviors. Later, after escaping confinement, she engaged in more territorial behavior in the morning.

In the mobile game Jurassic Park Builder, the Tyrannosaurus is active for four hours at a time; in the sequel Jurassic World: The Game, it is active for eight-hour periods instead.

Diet and Feeding Behavior
Artwork by DPG personnel of a Tyrannosaurus ambushing a herd of Parasaurolophus and Gallimimus. Several Compsognathus are present fleeing the resultant stampede.

The Tyrannosaurus is an opportunistic generalist carnivore: it is not a matter of what it will eat so much as what it can fit in its mouth. While wild on Isla Nublar, the individual there was known to primarily prey on Parasaurolophus and Gallimimus, also feeding on the goats that were left on the island. It was also seen to prey on Triceratops, Velociraptor, and at least one human. On Isla Sorna, there is further evidence of Parasaurolophus predation; in addition, Edmontosaurus remains can be seen in the tyrannosaur nest, as well as what appear to be Pachycephalosaurus remains. The tyrannosaurs on Isla Sorna did also prey on humans, but this was mostly out of retaliation and defense of their territory. An adult male released into San Diego by accident preyed on a domestic dog and at least one human before using another human to teach his son how to hunt. The original script and junior novelization of Jurassic Park /// describe a tyrannosaur feeding from a small sauropod carcass, and the original storyboards explicitly label the carcass as tyrannosaur kill. This implies that Tyrannosaurus can take down small sauropods, though InGen reports from October 5, 1994 describe the tyrannosaur of Isla Nublar as failing to kill adult Brachiosaurus. The Jurassic Park Adventures junior novels describe Tyrannosaurus attempting to prey on Triceratops, exhibiting aggressive behavior toward a Brachiosaurus, and attempting to prey on Pteranodons.

Tyrannosaurus rex swallowing a goat by tilting its head upward, Isla Nublar (6/11/1993)

InGen’s Tyrannosaurus are unable to distinguish stationary objects from a stationary background, meaning they can only perceive objects that are moving. This may be due to genetic hybridization with amphibians, according to Dr. Laura Sorkin. However, the extraordinary sense of smell of this animal gives it an easy advantage when hunting; a prey animal may freeze as a defense mechanism, but it cannot stop exhibiting its natural scent when surprised. Thus, a tyrannosaur can still track prey very easily. Furthermore, some tyrannosaurs have developed another technique to spot prey; if unable to detect nearby animals by scent, for example if another more overpowering smell is nearby, the tyrannosaur can give a deafening roar to startle prey into movement.

Both Jurassic Park and Jurassic World fed their tyrannosaur a steady diet of live goats. In both cases, the goats were left tethered and unable to escape; this deprived the tyrannosaur of the stimulation provided by active hunting. This was criticized by Dr. Alan Grant during his 1993 visit to Isla Nublar. In Jurassic World, there would be seven feedings of one goat each per day; if this were carried out every day, the tyrannosaur would actually be extremely overfed. Like the Mosasaurus, it is highly likely that the animal sometimes refused food if it had already eaten. According to the Jurassic World website, a Tyrannosaurus consumes roughly 22 tons of meat per year; the Jurassic World Facts mobile application states that it eats 308 pounds of meat daily, which is closer to 56 tons per year. Presumably, it does not normally feed every single day, consuming large amounts all at once rather than daily.

Due to its immense dietary needs, the Tyrannosaurus must feed from a variety of food sources, and therefore must utilize multiple strategies to obtain food. When hunting, it primarily relies on ambush techniques. Despite its massive bulk, it is well-camouflaged against the forested environments where it normally conceals itself. When prey ventures close, it lunges out, typically engaging in a brief pursuit before delivering a crushing bite with its jaws. It can shatter bone when it clamps down, causing debilitating internal injuries and often killing its prey within seconds. The Jurassic World Facts application claims that juvenile Tyrannosaurus hunt by pursuit rather than simple ambush, as the adults have difficulty turning at high speed; it also states that there is evidence that Tyrannosaurus engage in cooperative hunting.

Game trails such as the one in Isla Sorna’s northeast are typical hunting grounds for this animal. From here, it can position itself in a prime spot to ambush prey, dashing out from the treeline before its victims can react. However, it may also take advantage of other environmental features to capture prey. When prey items are distracted, they are easier to kill; one Tyrannosaurus was witnessed using such a technique to kill a Velociraptor it had been stalking during the 1993 Isla Nublar incident. Tyrannosaurs are modestly intelligent and can adapt to the situation when hunting; this enables them to bring down more well-defended prey such as Triceratops. During combat, they are able to test their enemies for weak points, such as the necks of better-armored prey that simple biting techniques might not immediately best. Smaller prey items provide it with much less food, but are easier to kill; the tyrannosaur simply picks them up in its jaws and thrashes them back and forth. This causes severe internal injury to the prey, which the tyrannosaur then either drops to the ground or slams into any nearby object to finish the kill. During such attacks, it is common for body parts to fly off of the prey.

Even if a prey item escapes, the tyrannosaur’s teeth are designed to cause death by sepsis. The tips of the teeth puncture the prey’s flesh, and the serrations on the inner edges cause tearing wounds on the way out. Flesh caught in the wounds provides food for symbiotic bacteria in its mouth. These bacteria are then transmitted to prey via biting; a bitten prey item will quickly succumb to the septic bite, making it too weak to continue fleeing. The tyrannosaur can track the prey item and kill it in its weakened state.

In addition to both ambush and pursuit hunting, the Tyrannosaurus will scavenge carrion. This, in fact, is a better use of its energy; eating prey that is already dead is much less energetically expensive than chasing down and killing another animal. It also practices kleptoparasitism, or the stealing of other animals’ kills. According to the mobile game Jurassic World Alive, it particularly targets Carnotaurus, bullying the smaller animal away from kills it has made. It was also observed performing this behavior with Velociraptors which had killed a Parasaurolophus during the 1993 incident; in this case, not only did the tyrannosaur steal the kill, it also killed one raptor. The sheer size of the tyrannosaur permits it to dominate any carcasses it finds, and it will aggressively chase away any animals that approach it while it is feeding.

Tyrannosaurus tearing off a bite-sized chunk of meat from a Gallimimus, a common prey item, Isla Nublar (6/12/1993)

Once it has secured a food source, the tyrannosaur will usually pin the carcass down with a foot and tear off large chunks of meat using its jaws. It cannot chew, and simply swallows pieces of meat whole; it will consume muscle, organs, and bone alike. However, it cannot actually digest bone; Dr. Laura Sorkin noted in her journal that bone fragments can be found in tyrannosaur dung. Small enough prey items, such as goats, may simply be swallowed whole. The tyrannosaur will raise its head upward, allowing prey to slide into its throat easily; if there is not enough room for this, it may use its muscular tongue to draw prey into its throat instead.

Social Behavior
A family group of Tyrannosaurus. The mother (right) shows affection toward her son (middle), while the father (left) stands lookout as a herd of Stegosaurus passes by (not pictured), Isla Sorna, (5/25/1997)

Because of their large food requirements and highly territorial nature, Tyrannosaurus are typically solitary animals. However, they will tolerate the presence of others under some circumstances. The most obvious case is a mated pair and offspring; family bonds between Tyrannosaurus are extremely strong, even leading to emotional behavior overriding logical behavior. Jurassic World also succeeded in keeping multiple Tyrannosaurus together; there were at least two subadult males, though the actual number of animals in the park is not known. According to the park website, no aggressive disputes had ever been observed between the captive animals. However, they were not exhibited in T. rex Kingdom alongside the eldest female, suggesting that she would not permit her territory to be shared. Additionally, the website acknowledges that fossil evidence suggests that this species often engaged in intraspecific combat; it is not known if the social behavior in Jurassic World’s younger tyrannosaurs was naturally-occurring or if their tolerance of one another was enforced by park staff.

Physical contact between even friendly tyrannosaurs is still fairly low. Parents will comfort and encourage their young by nudging with their snouts and making eye contact. Males and females also utilize different vocalizations to communicate, presenting the possibility of socially-established roles for male and female animals. However, these have not been detailed. In mated pairs, the male appears to be responsible for hunting and defense of the family, as males are usually seen with scarring and broken teeth. Females in familial groups are usually more responsible for providing emotional care for the offspring. Despite this, however, both the male and female will provide their offspring with care and protect them from danger, so these roles are not without exceptions. Hunting between mated pairs appears to be a joint effort, raising the possibility that mature animals from the same family groups could hunt cooperatively to bring down prey.

Jurassic World: Evolution portrays this animal as solitary, not tolerating any others of its own kind within its territory. As all of the animals (excepting the Indoraptor) in this game are females, no mated pairs can be established, so the solitary behavior follows what is depicted in the films.

Reproduction
Cloaca of a female Tyrannosaurus rex. Note the position posterior to the hips.

Tyrannosaurus mating behaviors are unknown, but the reproductive anatomy of the female is featured in Jurassic Park: The Game‘s tyrannosaur model. It has a cloaca located on the base of the tail. It is unknown if the male has the same structure.

Biologists referenced by the Dinosaur Protection Group suggest that tyrannosaurs mate for life. Only one instance of reproduction has been reported, but the rearing behavior exhibited in that family is highly detailed. The adults had nested within a large depression in northeastern Isla Sorna, away from most of the central island’s predators. Only one infant survived as of May 23, 1997; it is not known how many eggs were laid, or how they were incubated. Roland Tembo estimated that the infant was only a few months old at the time; however, it was already several feet long. This suggests that the early-life growth rate of InGen Tyrannosaurus is exceptionally rapid, or that Tembo’s age estimate was incorrect. If he was correct, then the juvenile would have hatched early in the year, during the dry season.

Depiction of a male and female Tyrannosaurus confronting a pack of V. a. nublarensis and several Compsognathus over a Parasaurolophus carcass. The tyrannosaurs’ offspring appears to have become surrounded by raptors.

Both adults participated in the rearing process. By the time of the 1997 incident, the juvenile was old enough to be left on its own for periods of time; however, Tembo noted that the nest was constructed in such a way that it was mainly approachable from downwind, so the adults would be able to scent the nest even while away from it. With an ability to scent for up to ten miles, they could easily detect any threat to their nest and make a quick return. They also stockpiled food within the nesting area for their offspring to feed on; carcasses in various states of decay could be seen around the nest perimeter, ensuring that the juvenile always had food readily available.

Any threat to their offspring would be dealt with swiftly and aggressively. The mother was the main source of comfort to the infant, and also typically the initiator in lethal attacks against threats. She could be seen comforting her infant through eye contact and by making cooing sounds. The father’s role was defense of the family; his scars and broken teeth suggest that he often engaged in combat with other dinosaurs, so he may also have been the family’s main hunter. Emotional bonds between parents and offspring are strong enough to override logic; when they scented their offspring’s blood, they responded by chasing it across the island despite knowing that their offspring was in the nest. A tyrannosaur’s sense of smell, of course, is more powerful than its vision; this is likely why they responded more strongly to the smell of their infant than the sight of it. The infant communicates fear or discomfort to its parents using a unique distress call, which both adults respond to vigorously.

Juvenile Tyrannosaurus makes its first kill while encouraged by its father, San Diego, CA (5/25/1997)

The father gave his offspring an opportunity to hunt live prey on May 25, though this was done outside of their natural environment. He cornered a small prey item (in this case, InGen CEO Peter Ludlow), broke the prey’s leg to prevent escape, and knocked it down. He then encouraged his offspring to move in for the kill by nudging with his snout.

In the wild, once they were free of human interference, the mother was seen nuzzling her son using her snout while the father kept a watchful eye on a passing herd of Stegosaurus accompanied by a Pteranodon flock.

The natural growth rate of InGen’s Tyrannosaurus is not known. Under the influence of growth boosters, an individual hatched in 1988 reached adult size by 1993, or about five years. Other adults had reached sexual maturity by 1997; assuming they were also hatched in 1988, this would make them nine years old.

Vocalizations

The vocalizations of the Tyrannosaurus are highly diverse. Perhaps the most famous is the iconic territorial bellow, a deafening and unmistakable ringing sound that can carry for quite a distance. When giving this roar, the animal usually assumes one of two poses: lowering the head to the ground, or raising the head skyward. Typically, the head-lowered pose is used when entering a new territory, while the head-raised pose is used after defeating a territorial rival. This suggests that the former is used for warning potential territorial rivals, whereas the latter is used to reinforce dominance.

Jurassic Park’s resident Tyrannosaurus breaches containment, giving a characteristic territorial bellow, Isla Nublar (6/11/1993)

A variety of other roars and growls are used to frighten and intimidate rivals during combat situations and in defense of resources or territory, but they are also used to scare victims into running during play activity. Tyrannosaurus are intelligent and require stimulation, but victims may freeze in self-defense; therefore, the tyrannosaur uses loud vocalizations to frighten its playthings into motion.

Other sounds it makes are involuntary; when angry or frustrated, such as when it sustains an injury or is unable to reach prey, it can be heard making moaning and groaning sounds, and occasionally screaming when particularly angry. When lunging for prey, it can sometimes be heard making an apparently involuntary trumpeting noise just before it bites.

Tyrannosaurus rex is, as per the Jurassic World Facts application, able to hear very low-frequency sounds. This suggests that it uses such sounds to communicate. There is some evidence that the Tyrannosaurus utilizes very low-frequency noises to establish territory. On occasion, the approach of a tyrannosaur is heralded by ripples in pools of water and low-pitched booming sounds. These are generally assumed to be the animals’ footfalls, but when the animals are close by, these ripples and booming sounds are usually absent. In fact, a tyrannosaur in real life would not be capable of causing these effects with its feet, as despite its size, it is not bulky enough. The interesting possibility has been raised that the ripples and booms are actually the result of low-frequency sounds made by the animals as they enter new territory, a suggestion that is supported by the lack of such effects when the animals are visible and the fact that these effects have, so far, only been observed when tyrannosaurs are coming into territory that they did not previously inhabit: the exterior of the tyrannosaur paddock on Isla Nublar, and the area north of the Workers’ Village on Isla Sorna following the alteration to perceived territory during the 1997 incident.

Of particular note are the sex-specific noises which can be heard being made by male and female tyrannosaurs. The male makes a variety of lower-pitched calls and roars, while the female can be heard to make higher-pitched yowls and screeches. The female may also make softer cooing sounds when comforting its infant; the infant itself has a unique wailing distress cry that it makes to alert its parents when it is frightened or in pain. The sex-specific cries, however, appear not to be physiologically mandated, but rather socially taught. The female tyrannosaur from Jurassic Park has been observed making the male’s characteristic calls, despite having hatched long before the introduction of Hyperolius viridiflavus DNA that inadvertently caused the affected dinosaurs to become capable of sequential hermaphroditism. This rules out the possibility of the animal having changed sex. Instead, it appears that sex-specific vocalizations are ingrained into the tyrannosaurs by social conditioning. Since the Tyrannosaurus from Jurassic Park would not have had exposure to others of her kind from the time she was introduced to Isla Nublar in 1989 until the Isla Sorna animals were shipped to Isla Nublar in 2004, she would not have socialized normally, and therefore could develop behaviors that are outside the norm for her species.

Ecological Interactions

As an apex predator, the Tyrannosaurus has a drastic impact on its environment. Its predatory activity regulates the populations of smaller animals, including but not limited to Triceratops, Gallimimus, Velociraptor, Parasaurolophus, Edmontosaurus, Pachycephalosaurus, and goats. Eating these animals actually reduces predatory pressure on their prey, most of which consists of local plant life; however, eating small carnivores such as Velociraptor can also reduce pressure on animals as well. The Tyrannosaurus also scavenges carrion, which can become a potent source of disease if left unchecked.

A typical “victory pose” after defeating a territorial rival; in this case, a Carnotaurus, Isla Nublar (6/23/2018)

On such a small island as Isla Nublar or Isla Sorna, however, Tyrannosaurus is also fiercely competitive with other carnivores for food. It has been shown engaging in territorial conflict on repeated occasions, and is usually the first to strike during these disputes. Velociraptors are often seen as prey items, but can also be competition for food. Baryonyx, Carnotaurus, and Allosaurus introduced to Isla Nublar following 2004 have been suggested by the Dinosaur Protection Group as potential competitors for food for the Tyrannosaurus, and the films have already established Spinosaurus as a fearsome territorial competitor. In particular, a Baryonyx was seen being killed by the Tyrannosaurus in the virtual-reality film Jurassic World: Blue, and two Carnotaurus have been seen being fought by the same Tyrannosaurus in Jurassic World: Fallen Kingdom. In one case, the attack was fatal for the Carnotaurus. The mobile game Jurassic World Alive states that it is common for Carnotaurus to have their kills stolen by Tyrannosaurus, implying that these two species are frequently at odds. Kleptoparasitism has already been documented in Tyrannosaurus in Jurassic Park: The Game, in which a Tyrannosaurus not only steals a Parasaurolophus carcass from a Velociraptor, but also kills the raptor itself.

Dominance is established via prolonged eye contact.

However, not all ecological interactions between Tyrannosaurus rex and other species are predatory or competitive. During the 2015 incident which marked the end of Jurassic World, the park’s senescent female Tyrannosaurus had been released to drive back the escaped Indominus rex, with park staff hoping her territorial instincts would cause her to fight this rival. During combat, a genetically-modified Velociraptor named “Blue” joined in, attacking the Indominus in retaliation for her pack being killed. The tyrannosaur tolerated the raptor’s presence, and after firmly establishing dominance via eye contact once the hybrid animal had been killed, both animals parted ways. In the following years, however, there is no sign of any friendly relationship; Jurassic World: Blue depicts a mild fight over food between these same two animals.

It lives in heavily-forested areas, with trees such as pines and redwoods commonly growing in places where it hunts. The activity of such a large animal would topple smaller trees and crush other plants, but the largest flora would remain mostly unharmed.

Symbiosis in Tyrannosaurus is firmly established. In Jurassic Park: The Game and Jurassic World: Fallen Kingdom, groups of Compsognathus appear near a Tyrannosaurus. In the latter case, the smaller carnivores opportunistically devoured a scrap of food that the tyrannosaur had killed. The compies do recognize the threat posed by this much larger creature, though, and in both cases scatter at the tyrannosaur’s approach. Compies also can be seen fleeing as a Tyrannosaurus engages in a territorial dispute with a Spinosaurus.

The relationship between Compsognathus and Tyrannosaurus is parasitic, as the compies steal food from the larger animal. However, a commensal relationship between Tyrannosaurus and flies also exists. Flies eat carrion and lay their eggs in rotting meat, a substance which the tyrannosaur leaves behind in abundance. When the tyrannosaur makes a large kill, it rarely eats the entire thing; any meat left behind attracts swarms of flies. Tyrannosaur nests in particular feature stockpiles of food for the infants, which are usually left partially-eaten. Vast swarms of flies gather around these nests. Flies may also gather near the jaws of tyrannosaurs, attracted by the smell of rotting meat caught in their teeth. In the event that a tyrannosaur does eat any flies or maggots, it is unlikely to be harmful, and would merely be some additional protein.

Mutual symbiosis exists between Tyrannosaurus and bacteria that live in its mouth. When the tyrannosaur feeds on meat, some gets caught in the serrations of its teeth. Bacteria feed on these, flourishing in the mouth. Then, when the animal bites a prey item, these bacteria are transmitted into the wound and cause sepsis. The prey dies due to this, allowing the tyrannosaur to feed and continue to support its oral flora.

Not all microorganisms in the mouth are healthy, however. When a tyrannosaur breaks a tooth, microbes may invade the injury from inside the gum line. This causes a disease known as ragged tooth, which can lead to tissue breakdown in the jaw. Eventually, death by starvation may occur as the dinosaur’s ability to hunt is impaired. Jurassic World’s paleoveterinarians would regularly inspect the Tyrannosaurus for signs of common oral infections.

In Jurassic World: Evolution, the Tyrannosaurus (as with most theropods) is a host to Campylobacter, a bacterium that affects modern birds. This can lead to campylobacteriosis.

Interactions with Humans

Tyrannosaurus is one of the most well-known dinosaurs in the public eye, and so upon creating them, it is understandable that InGen intended this animal to be one of the star attractions at Jurassic Park. The tyrannosaur would have been visible from the main tour road, where one of the restrooms was located. It was, however, deprived of the opportunity to hunt, instead being fed live but tethered goats. This resulted in the animal lacking stimulation. Furthermore, its expansive, naturalistic paddock gave it plenty of space to hide, which it took advantage of. This resulted in it not showing itself during the tour, only emerging much later when its hunger drew it to the goat it was presented. During the park’s second incarnation, Jurassic World, the visibility issues were addressed by placing the animal in a significantly smaller paddock and filling it with redwoods. However, it still lacked significant stimulation, as it was fed tethered goats as in the original park.

Tyrannosaurus attempts to use Dr. Alan Grant as a source of stimulation. Note that the eyes are not focused on him; she locates him using her sense of smell. Moments after this image, she became frustrated at his lack of movement and rammed the nearby vehicle instead, Isla Nublar (6/11/1993)

As an intelligent animal, the Tyrannosaurus is naturally curious and exploratory, investigating any new environment it finds itself in. It may view humans as food when hungry, but does not single them out as prey over more readily-available species. Instead, it appears to find humans and artificial objects highly entertaining. Upon breaking free of confinement in 1993, Isla Nublar’s Tyrannosaurus established territory and was then drawn to one of the electric Ford Explorers by a bright flashlight. She made the Explorer and its two human passengers into a much-needed plaything, ramming and eventually flipping the vehicle. She attempted to extract the humans from inside, but failed, instead pushing the vehicle over a cliff. During the encounter, she also became fascinated with the light and smoke given off by road flares, which she chased after. Road flares were also used in Jurassic World to direct her to consume goats for the entertainment of tourists, and later by Claire Dearing to direct her attention to the escaped Indominus. In June 2016, this same tyrannosaur encountered a vulnerable human, roaring at him to get him to run so she could chase him down Main Street.

However, the sheer size and power of the Tyrannosaurus means that even playful interactions can be fatal. During her initial foray outside of her paddock, Jurassic Park’s Tyrannosaurus severely wounded Dr. Ian Malcolm after ramming him through a faux-thatch restroom wall, and then gripped Donald Gennaro and flung him back and forth until his body flew apart. As she did not eat him, this behavior was not predatory but instead a form of play, much like with the Ford Explorer. Lacking powerful hands, this animal mostly interacts with its environment using its mouth, which is filled with seven-inch serrated teeth, and so it usually kills what it is playing with.

The fame and awe-inspiring nature of this huge predator has led to its exploitation by humans on numerous occasions, more than most other dinosaurs. Aside from its understimulating existence in both Jurassic Park and Jurassic World, it was targeted by big-game hunter Roland Tembo as the ultimate game; Tembo was only prevented from killing a male tyrannosaur by the interference of wildlife activist Nick Van Owen. Even after the animal was tranquilized rather than killed, InGen’s CEO at the time Peter Ludlow had it and its son transported to San Diego for use in a resurrected earlier incarnation of the failed Jurassic Park. They were not originally planned for use in this park, but following the loss of his intended display pieces, Ludlow decided to use the tyrannosaurs to save InGen from bankruptcy. A lack of understanding of the animal’s biology led to its falling into a coma and subsequently being given an excessive dose of stimulants, causing it to go into a drug-induced hyperactive state. The resulting damage to person and property was eventually used by anti-dinosaur groups such as Extinction Now! as evidence that dinosaurs should not be allowed to live, though some San Diego citizens were more sympathetic to the animals’ plight despite their encounter with this dangerous predator. The Dinosaur Protection Group frequently used imagery of the park’s senescent female to lobby for the rescue of Isla Nublar’s animals, and she featured heavily in a June 5, 2018 article by Klayton S. entitled “Saving the Carnivores of Isla Nublar.”

Promotional poster released by the DPG

Ken Wheatley, a mercenary hired in 2018 by Eli Mills to retrieve Isla Nublar’s dinosaurs, also saw the potential monetary value in this animal. When the eruption of Mount Sibo drove the last known Tyrannosaurus eastward, his mercenaries subdued and captured her in short order, placing her on board the S. S. Arcadia for transport to Lockwood Estate. She was not presented for sale during the auction before it was disrupted, and was instead released by Maisie Lockwood in order to save her from death by hydrogen cyanide poisoning.

She was inadvertently responsible for releasing Isla Nublar’s Mosasaurus maximus into the ocean by disrupting the lagoon gate closing sequence, and also for preventing the creation of new hybrids using an Indominus bone sample by stepping on it after killing Eli Mills. Both of these events have notable implications for the human species.