Tirten & Mettalus Species Guide

Mettalus and tirten (singular: tir) are two very closely related species, despite their drastic differences in appearance. Because they are so biologically similar, this guide describes them both, with distinctions made when necessary.

Tirten evolved from mettalus, and are considered a subspecies of mettalus. Theoretically, the two should be able to interbreed, but only one mettalus is alive in the current day, so it's difficult to test that assumption. Regardless, both can be mapped to the same general inheritance patterns (see Tirten and Mettalus Genetics).

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Basic Info

Physical Description

• Mettalus are bipedal, semi-furred, feline-like creatures with long, hairless tails and large manes. They have flexible hands that are capable of grasping and manipulating objects. These hands have four flexible digits, with a partially formed and mostly inflexible fifth digit. Unlike tirten, their hands are webbed.
• Tirten are maned bipeds that are mostly hairless. They have catlike eyes with slitted pupils, and teeth that resemble those of many carnivorous species. Like mettalus, they have flexible hands. However, theirs have five flexible digits.
  • A small subset of tirten, known as katiren (singular: katir), have furred, catlike ears and tails. Some of them have naturally curved claws that resemble those of mettalus. The genes that lead to this phenotype are tied to a natural ability to use forsen, allowing these individuals to shift between tir and kat forms.

Both species are around 5'4" tall on average, but mettalus have a range of height that leans a few inches shorter than tirten.

Scientific Names

• Mettalus: metafelis adamas (adamas)
• Tirten: metafelis (adamas) depilis

These names are exonyms, existing purely for the sake of my own entertainment, and are not known to tirten nor mettalus.

Typical Vitals

• HR: 50-80 BPM
• RR: 10-20 BPM
• Temp: 99-102 F
• Average Lifespan: 50-70 years
  • The average tir lives about a decade longer than the average mettalus.

Diet

Mettalus and tirten are obligate carnivores. They can eat grains, fruits, and other plants, but they are not their main source of sustenance. They require specific components from meat (arachidonic acid, taurine, and vitamin A) that they cannot convert from plants.

• It's thought that they gained an increased ability to digest plants due to a period of time where meat severely decreased in availability, which lines up with genetic studies that indicate a population bottleneck at some point in the past.
• Tirten tend to prefer meaty, salty, and fatty foods over sweet ones, though individuals can be exceptions. This is likely due to their nutritional needs and decreased ability to taste sweet foods.
  • Tirten's distant relatives, katen, yaketen, and ketnoen, cannot taste sweetness at all but have an incomplete gene for sweetness receptors. In tirten, an altered copy of the gene (theorized to have been brought in by a zoonotic virus) filled in the gaps.

  • Mettalus have a reduced ability to taste sweetness compared to tirten, but are still able to.
• Both species have high iron and protein requirements.
• Both species tend not to drink much water, and get the majority of their moisture from food.
• Fish is a staple of both species' diets.

Reproduction

Both species are monestrous and typically only give birth to one or two offspring at once. Heat usually occurs in warmer seasons, but is considered to be based on environmental conditions (food, water, presence of a potential partner, etc) rather than seasonal.

• They are induced ovulators.
• Estrus lasts 5-10 days without a partner, and 3-7 days with one. For tirten, prostitution and other forms of hired partners are a legal industry for this reason. Though there are no stigmas directed at prostitutes, some view those who require their services as unable to find a "real" partner.

Social Behaviors

Tirten and mettalus are highly social and live in societies with complex social structures (see Culture).

Notable Features

• Both species have vertical pupils and can see well in the dark. Tirten exhibit widely distributed wakefulness patterns, but mettalus are almost all nocturnal.
• Both species have 38 chromosomes.
• They lack collar bones, and instead have immensely strong ligaments and muscles around their shoulders (this leads to most tirten and mettalus appearing to be slim compared to bipedal collar bone bearing species like humans). This lack of a collar bone makes them better able to fit into small spaces. While it isn't particularly pleasant, an individual can make their own shoulders touch from either direction with practice.
• Mettalus are clear and obvious digitigrades. Meanwhile, tirten are cryptic digitigrades. They have a "hidden" joint in their legs that goes mostly immobile shortly after young tirten learn to walk bipedally. The flexibility of this joint can be trained, but this training is typically only pursued by athletes.
• The teeth of both species resemble the teeth of domestic cats. They also have spiny papillae on their tongues like domestic cats.
• Both species are extremely sensitive to caffeine, to the point that human-level highly caffeinated drinks never took off with them. Compared to the recommended safe dosage of 400mg for humans, the safe maximum dosage for tirten and mettalus is closer to 100mg. This is partially because caffeine lingers in their system longer than it does in humans.
• Theobromine is also a cause for concern in tirten and mettalus, similar to the way it is in cats and dogs. Because of this, their chocolate equivalent is quite dilute and is often used as part of other dishes rather than eaten on its own. The generally recommended safe maximum dosage of theobromine for both species is around 3g (which is just over the amount found in approximately 50g of human milk chocolate).
  • Since this amount is rarely even touchable by tirten or mettalus foods, theobromine is often used as a poison in fiction. It's just plausible enough to be used, but well known enough that no one would think twice about an author writing about it.
• Tirten and mettalus have many natural/common hair and eye colors that may be considered atypical to other species. The manes of tirten may have naturally occurring patterns such as streaks, stripes, and faded tips. Telling the difference between dyed and undyed hair can be somewhat difficult because of this.
  • Eye colors: blue, green, brown, orange, yellow, violet, red/pink (uncommon; typically associated with albinism)
  • Hair colors: red, orange, black, brown, gray, green, blue, pink/magenta
• Their sense of smell is stronger than a human's, but worse than a cat's. Like cats, they have a Jacobson's organ and exhibit the flehmen response. Pheromones are an important part of everyday communication.

Common Health Conditions

Arthritis: Due to their flexible skeletal structures, tirten and mettalus often develop arthritis. The average age of onset is 28 years, but it can appear as early as the late teens. The most common sites are the back, and the leg and shoulder joints.

Asthma: Asthma impacts roughly 15% (3 out of 20) tirten and 8% (2 out of 25) mettalus. The majority of cases are mild, but they tend to worsen with age.

Kidney disease: Tirten and mettalus are very prone to many forms of kidney disease. Renal failure is one of the leading causes of death for both species.

Urinary calculi: Specifically, they are prone to struvite and calcium oxalate stones.

Wrist bone collapse, missing wrist bones, and wrist osteoarthritis: Mainly in tirten due to the lack of an inflexible digit occasionally resulting in extra loss of bone. Wrist bone collapse is similar to Kienbock's disease in humans, but it typically strikes earlier (late childhood rather than early adulthood). Although rarer than the other conditions listed here, it's quite well-known. Being born without some bones of the wrist entirely is commonly screened for due to its prevalence, and when screening does not occur or was not sufficient, it may be mistaken for wrist bone collapse. Many tirten who are more reluctant to visit a specialist may mistake wrist bone collapse or a missing wrist bone for wrist osteoarthritis.

Culture

Government

Tirten

Tirten are governed by the Yakom, which is helmed by a council, members of which are referred to as yakomtiren. Aside from that, their society is organized into komen, which are comparable to guilds.

Mettalus

Mettalus were governed by a totalitarian government led by a single appointed individual.

Technology

Tirten

Tirten have an odd mixture of technologies. They do not have cars, nor do they have widely available motorized transport, preferring to navigate the world on foot or by bike. Motorized carts exist, but they are typically used to assist manual transport of large amounts of goods, rather than as transport themselves. Motorized chairs are available as mobility aids.

Plant agriculture is utilized, but not very extensive due to their limited ability to digest plants. Most of the plants they grow are used to feed animals rather than directly eaten. Hunting is quite popular.

Mettalus

Mettalus utilized a unique, forsen integrated form of technology. Metal plates were installed on the palms and face, allowing for individuals to directly interface with devices or with each other. The latter was secretly used as a means of mind control. Because they interfaced directly with their technology, they often viewed themselves as one with it.

Pawplates were placed during youth, typically around the fifth birthday. Faceplates were installed at the start of adulthood, and could be placed anywhere on the face, but were typically on the cheeks or forehead. Both pawplates and faceplates were fully customizable.

Aside from that, mettalus had extensive animal agriculture, especially surrounding aquatic life. Similarly to tirten, they did not have widely available motorized vehicles, preferring to use them sparingly. However, bicycles and other non-motorized means of transport were significantly less popular than just walking.

Spoken Language and Vocalizations

Due to being isolated to a single continent and experiencing multiple population bottlenecks, tirten speak a single language, known as Tirnuk. It is outlined in a separate guide. Mettalus spoke a proto-Tirnuk, typically referred to as Alf.

Aside from speaking, both species make several notable vocalizations:

• Bii - a trill-like noise that signals alertness. Often used as a greeting or made mistakenly when startled.
• Ca - an open-mouthed hissing noise/loud exhale. Almost always an expression of anger, typically made in close range during a fight.
• Eca - a hissing noise made through closed teeth. Typically an expression of anger or anxiety.
• Mreme - a quiet, chatter-like noise used to draw attention at a close range, typically only used in situations that require quietness or stealth.
• Mri - the vocalized version of a mreme. A chirplike noise. Used to draw attention to oneself at a short distance, often as a greeting. Usually responded to with a bii.
• Ria - a meow-like noise typically made when a tir is in distress. It is most frequently made by young tir as a way to get their parents' attention.
• Riau - a mixture between a growl and a meow, made almost exclusively when a tir is in heat.
• Riu - a growl-like noise typically made to signal anger or disapproval.
• Rrurru - a noise that resembles a cheetah's purr. Used to relax/comfort others or oneself.

Due to their resemblance to humans and vocal abilities, it's important to note human vocalizations they specifically do not make.

• Laughter - Tirten and mettalus do not laugh. In situations where a human would laugh, a tirten will typically mri, mreme, or bii.

Body Language and Interactions

Body language:

• An open-lipped, closed-mouth smile is an indicator of discomfort, fear, or hostility. Whether it is an act of appeasement or one of provocation depends on context.
• An open-lipped, open-mouthed smile is an indicator of excitement or alert. Since both species have a vomeronasal organ, they often open their mouths to catch scents they wouldn't pick up on otherwise.
• A closed-lipped, closed-mouthed smile is an indicator of comfort. It is considered friendly.
• They will show their teeth when they feel threatened, and may emphasize any s-like and h-like noise in words they speak to appear more intimidating in place of an eca or ca. They also tend to bend their knees, as it's easier for an individual to fling themselves at or away from their attacker if their knees are bent. Their head will lean toward their attacker to make the abdomen harder to reach. They may curl their fingers or show off their hands, especially if they have claws.
• Tail and ear positioning language resembles that of domestic cats.

Interactions:

• They are very touchy with friends and family, especially when around strangers. An individual leaning their head on another's shoulder or multiple individuals walking shoulder to shoulder are fairly common.
• Scent marking/face rubbing is not uncommon among family and friends.
• Touching a katir's or mettalus's ears or tail is considered extremely rude. Doing so is typically reserved for private grooming sessions or sexual activity.
• Tirten and mettalus do not kiss. They're much more likely to nibble or bite affectionately.
• They like to allogroom, with both their fingers and their tongues. Typically, tongue-based allogrooming only occurs when food is involved, or in private. Tongue-based allogrooming does not have sexual or romantic connotations, but it's generally considered awkward for strangers to witness.