In appearance, Arboreals were covered with hair (at least their hands and heads were) and had long, sharp fingernails, dark eyes, and a ridge running from their noses to the back of their heads. (ENT: "The Xindi", et al.)
Arboreals were susceptible to a certain type of mutagenic virus created by the Loque'eque. (ENT: "Extinction") Arboreals had a dislike and perhaps even a fear of large amounts of water. (ENT: "Countdown") Arboreals were considered to be lethargic by the other Xindi species. They were also extremely calm, even when taken hostage. (ENT: "The Shipment")
Arboreals were intelligent enough that some worked on manufacturing kemocite, in a facility specifically for doing so, which was on an Arboreal colony. The Arboreals who labored there sold the kemocite to many species. (ENT: "The Shipment")
The Arboreals utilized a diversity of spacecraft, such as a type of Xindi-Arboreal starship and a form of landing craft. (ENT: "The Council", "Countdown", "Extinction") Arboreal ships also included a vessel that was small, incapable of outmatching an Osaarian merchant ship, and contained a component that had Xindi writing on it. This Xindi craft also carried fuel, supplies, and the Xindi database. (ENT: "Anomaly (ENT)", "Extinction") Hand-held technology used by the Arboreals included a type of scanner. (ENT: "The Shipment")
History and culture
As the third species of Xindi discovered by the crew of Enterprise NX-01, it was believed by Doctor Phlox that this species probably evolved from some sort of arboreal sloth. (ENT: "Extinction") As with the other Xindi species, the Arboreals originated on the planet Xindus, before that planet's destruction. (ENT: "The Shipment", "The Council")
Two Arboreals, including Jannar, sat on the Xindi Council. (ENT: "The Xindi", "Rajiin", "The Council") In 2153, many more Arboreals lived on Azati Prime, whose population of Arboreals and Primates numbered over 1000. (ENT: "Stratagem")
The small, aforementioned Arboreal craft was on an interstellar voyage for at least a few months. At one point in the journey, the Arboreal crew visited the Loque'eque homeworld, where an Arboreal landing craft departed from the ship and traveled to the planet's surface, where it remained. (ENT: "Extinction") The Loque'eque homeworld was the larger ship's last destination before, in the same week or thereabouts, it was attacked and overpowered by an Osaarian merchant ship which stole fuel, supplies, and the Xindi database from the Arboreal vessel. (ENT: "Extinction", "Anomaly (ENT)") The Arboreals resisted the Osaarian pirates, so the Osaarians destroyed their ship. (ENT: "Anomaly (ENT)")
There were fewer than a hundred Arboreal colonists who resided on the planet where the kemocite refinery was located, approximately eighty of whom worked inside the facility itself. During the construction of the Xindi weapon, the Arboreals were requested by Xindi-Primate Degra to produce shipments of highly refined samples of the substance. The laborers regarded this as a cause for celebration, realizing the wealth this operation would bring to their colony. Although Degra claimed the kemocite would be used for research, the workers never considered why such pure kemocite was requested, and the facility's primary technician, Gralik Durr, later admitted that the greed of the Arboreal colonists may have blinded them from realizing the kemocite was to be used in the construction of a weapon to destroy Earth.
After about six months in which they produced the shipments of purified kemocite, the workers were being pressured by the other Xindi species into continuing to use the facility to manufacture huge amounts of kemocite. Although there were impurities in three of the kemocite production cycles, the Arboreals found a ruptured seal which was thereafter repaired before another production cycle began. Their efforts to make up for the error included assigning two additional teams of workers to assist in synthesizing kemocite. The Arboreals expected that Degra and a Xindi-Reptilian crew wouldn't arrive for the last shipment until three days after the Reptilians and Degra actually returned to the colony. The Arboreal colonists were surprised by the advanced schedule and delayed their turnover of the final shipment, causing the Reptilians considerable annoyance. The Arboreals were regarded as a somewhat positive example by Degra, however, who observed the Reptilians could learn qualities such as patience from them.
The Arboreal workers meanwhile were unknowingly (with the exception of Gralik Durr) visited by an away team from Enterprise and even faced obliteration by the Starfleet officers, though Captain Jonathan Archer ultimately decided not to annihilate them. Also unbeknown to most of the laborers was that Gralik Durr secretly sabotaged the final dispatch of kemocite which was shipped by the Xindi visitors. (ENT: "The Shipment")
Once Degra discovered the Sphere-Builders had lied to the Xindi and manipulated them into building the Xindi weapon, the Arboreals were the only species he initially reckoned had any probability of realizing the treachery of the Sphere-Builders, when provided evidence of this from Enterprise. Arboreals contributed to a protective fleet (also including Xindi-Primates and -Aquatics) which escorted Enterprise to the Xindi Council planet. Shortly thereafter, the Arboreals eagerly listened to and considered the facts about the Sphere-Builders, as proposed to the Council (including the pair of Arboreal representatives) by Captain Archer. As Degra had suspected, the Arboreals were indeed fairly easily persuaded to accept the truth about the deceitful Sphere-Builders. Arboreals even helped form an armada that fought against the Xindi-Reptilians and -Insectoids, after those two species launched the Xindi weapon in opposition to the Council having officially agreed to postpone the weapon's launch. (ENT: "The Council") Although the fleet was left behind in favor of tracking the weapon with the relative quickness of Degra's ship, three Arboreals were aboard that vessel when it approached Earth and when the speedy craft took part in ultimately successful efforts to destroy a Xindi-Reptilian warship guarding the weapon and to prevent the weapon from annihilating Earth. (ENT: "Countdown", "Zero Hour")
Arboreals wore belts that seemed to indicate their position. For example, the Arboreal representatives to the Xindi Council wore five belts whereas the Arboreals who were assigned to the kemocite refinery wore three belts. An Arboreal who became infected with the Loque'eque mutagenic virus and was then incinerated to death by Commander Tret's people also wore three belts. (ENT: "The Xindi", "The Shipment", "Extinction")
Each of the two Arboreals who sat on the Xindi Council wore a soft-looking full-length coat which was primarily gold-colored. White furry material was at the shoulders, which were ruffled, as well as at the sleeves and at the borders of the coat's insides in the middle of the front, where the sides of the coat crossed over a black undershirt. The shirt was occasionally visible at the neck. The coats also had detailed gold and black ribbon trim. The belts on these coats were wide and in varying metallic hues, as Jannar's belt was mainly colored gold and his aide's was silver-colored. Also, each of the belt's five buckles matched the color of the surrounding belt fabric. Another difference between the outfits was that Jannar's coat alone incorporated a decorative, seemingly gold broach attached to the front, with a chain that stretched over the right shoulder and was affixed to a second metallic clasp on the back. (ENT: "The Xindi", "The Council", et al.)
Each of the Arboreal refinery workers who were assigned to the kemocite mining facility typically wore a less decorative uniform. These were long-sleeved, predominantly pale green jumpsuits, with beige trim accents. A wide, brown belt with three strips was wrapped all the way round the waist, fastened in three places with a vertical series of three metallic buckles. Each of the suits' shoulders was emblazoned with a red and white mining colony uniform patch showing Xindi iconography. Each shoulder patch consisted of a red-colored triangle with rounded sides, containing a white background on which was a red, three-pointed icon centered with rounded blade shapes wheeling out from its points and a white Xindi icon in the middle. (ENT: "The Shipment")
|Aquatic • Arboreal • Avian • Insectoid • Primate • Reptilian|
In the final draft scripts of third season Star Trek: Enterprise episodes "The Xindi" and "Rajiin", the Xindi-Arboreals were commonly referred to as "Xindi-Sloths". This was also how the species was referred to in the final draft script of "Extinction" (though the infected Arboreal who transformed into a Loque'eque was much more commonly referred to simply as a "Humanoid"). The way the species was referred to was changed by the end of the third season, as scripts for installments such as "Countdown" and "Zero Hour" instead referred to them as "Xindi-Arboreals". The first time the species was specifically named "Arboreal" in canon was in "Proving Ground".
When designing the Xindi-Arboreals, there was only enough time to draw a tiny pen sketch of the facial design; most of the work that went into conceiving it was done by sculpting clay, which was begun after the makeup artists realized which direction they wanted to take the design in. Although Makeup Supervisor Michael Westmore found that the Xindi-Arboreal makeup was one of the easiest to put together in general, the design ended up involving prosthetic masks whose frontal hair was a large challenge and presented him with much work. Each mask included not only facial hair but also some head-hair. Westmore implied that the Arboreals were probably vegetarians by giving them large teeth, which were almost like horse teeth and were twice the size of Human teeth. Contact lenses were not deemed necessary, as at least most of the actors who were cast to play the Arboreals had very dark eyes.
For each of the Arboreal-playing performers, nails – similar to those of a sloth – and hair were crafted into a pair of gloves. "So they can literally put their arms on and go to work," Michael Westmore said of the actors. "This is the first time we've done that with [an alien] [...] this complex."
The Arboreals were made to feature a variety of shades. "They range from light beige to darker brown undertones on the skin," noted Michael Westmore, "and then the hair that grows over them is different – from gray to blond, red to gray, like there's an underbase and an overbase to the hair."
For the Arboreals' head-hair, Hair Designer Michael Moore obtained fur fabric samples from National Fiber Technology. "I started looking at 'em and began to think, 'Hmm, this'd work.' It was more like a hood than a wig; I basically put it on a head form upside down to put it together, and then when I reversed it the hair was all on the outside." During production on Enterprise's third season, the makeup and hair departments blended their two respective types of head-hair. Any potential of a hard line between these was avoided by covering a strip of hair – which looked virtually Human and was at the front edge of the wig – with the hair Michael Westmore had crafted into the back of the mask's top. Moore's main concern with the wig was maintaining the stripe down the middle of the head.
The duration it took to apply the Xindi-Arboreal make-up is uncertain. Jannar actor Rick Worthy once suggested that the time it took to apply this make-up was about as long as it took to apply a typical layout of Klingon facial prosthetics.  Focusing on the Arboreal make-up, Worthy said, "The makeup process was long, maybe 2-3 hours usually early in the morning."  In another interview, he repeated this estimate exactly and added, "It took half that time to take it off in the evening."  However, in yet another interview, Worthy reduced the duration significantly, saying, "For Enterprise, they had me in the makeup chair for probably 1.5 hours or less." 
Executive Producer Rick Berman once commented that, of all the Xindi species, he thought "the Xindi-Sloth" looks especially good. (Star Trek: Communicator issue 147, p. 16) With similar gusto, Archer actor Scott Bakula praised the Xindi-Arboreals as "quite wonderful." (Star Trek Magazine issue 113, p. 7) Rick Worthy has repeatedly likened the look of Jannar to the design of the Star Wars character Chewbacca.  
Several Arboreal scientists' costumes from "The Shipment" were sold off on the It's A Wrap! sale and auction, including those worn by Sam Witwer, Louis Ortiz, Clynell Jackson III, and Jack Alsted. Each of the suits incorporated their own costume tag. Confirmed sales were between US$260 and US$324, although the costumes worn by Witwer and Alsted both required a second effort to sell them before they were bought.       A uniform patch from one of the Arboreal scientist costumes was also sold off on It's A Wrap!, as was Rick Worthy's costume as Jannar, the latter of which fetched US$360.88.   It's A Wrap! Project Manager Colin Warde once described Jannar's costume as "one of the most elaborate costumes" included in the entire auction. (Star Trek Magazine issue 139, p. 50) Furthermore, two Arboreal outfits were combined in a group of four Xindi costumes which were sold as part of the 40 Years of Star Trek: The Collection auction. The Arboreal costumes were Gralik's jumpsuit worn by John Cothran, Jr. in "The Shipment" and, as worn by Aldric Horton, a leather coat (presumably for Jannar's aide) which had white imitation fur lining and silver trim. 
The novelization of The Expanse refers to the Xindi-Arboreals as "Xindi-Marsupials." It describes them as being very slow-moving and says the Xindi-Humanoids regarded them as having thoughts mainly about napping upside down in trees. An account in the book says, "It was easy to believe, given the marsupials' tendency toward torpor, that they were harmless and stupid, but such was not the case [....] While they much preferred the company of family, [they] were shrewd when it came to politics, and had proven themselves fierce fighters when attacked." The novelization goes on to explain how, using their thick claws, the Arboreals were capable of violently tearing a Xindi-Humanoid's body with a single, strong swipe, even though Arboreals were inherently affable.