The Denobulans were a humanoid species from the planet Denobula.
Denobulans were typically polygamous, where a man typically had three wives, who each had three husbands. This created extremely large extended families; Phlox had 720 familial relationships, 42 with sexual possibilities. In addition, Denobulan marriages were not exclusive, and married Denobulans could be intimate with anyone they chose. The females emited powerful pheromones during their mating season. Male Denobulans often became combative during this time, and mating could require medical supervision. Denobulans typically preferred to be among large groups and found solitude uncomfortable. However, Denobulans, at least males, were uncomfortable being touched by persons they were not intimate with.
Among Denobulans, it was considered healthy for a person to hallucinate, as it was seen as a harmless way to release nervous energy.
The Denobulan lullaby was a form of song. In 2154, Phlox offered to sing one of these lullabies to Porthos, although the doctor remembered that his singing would often make his Denobulan children cry.
On their homeworld, Denobula, the twelve billion Denobulan inhabitants all shared one continent, resulting in living space being at a premium and Denobulan culture having come to embrace close, communal lifestyles, although this habitation arrangement was due to choice rather than necessity.
Denobulans had prominent facial ridges running down either side of the forehead to the cheeks, an enlarged brow ridge under a high receded hairline, a vertical crevice in the center of the forehead, and a ridged chin.
They also had ridges on their back, along the spine. Their toenails were dark brown and yellow striped, and they grew so rapidly that they needed to be groomed once a week. Denobulans also had very long tongues, and they used tongue scrapers. Denobulan males have a line of hair down the middle of their chest, up to their throat.
Denobulans females had very potent pheromones that the males could sense, and they released them when they were romantically interested in someone, and presumably during their mating season. Denobulan males were known to become violent during the mating season.
Denobulans had a unique ability to enlarge their faces. This was an instinct for when they feel threatened. It was likely similar to the defense mechanism of the blowfish, an aquatic lifeform native to Earth.
They also had an unusually wide smile for humanoids.
Denobulans seem to change their eye color depending on their moods.
Denobulans normally required very little sleep, but they did hibernate for five to six days each year. However, at a minimum, two days were sufficient. If a Denobulan was awakened prematurely, the results could be somewhat unpredictable - hibernating Denobulans, if woken, appeared extremely disoriented and confused, with oddly-pitched voices, and had difficulty maintaining normal motor skills and cognitive functions. Denobulans did not talk during meals, as they considered it a waste of time.
Denobulans had highly-efficient natural climbing abilities similar to those of Earth lizards, being capable of scaling vertical rock faces at a rapid speed with no equipment whatsoever, instead appearing to scuttle up the rock face without needing to find handholds.
They appeared to possess particularly powerful immune systems; when Phlox was nearly assimilation|assimilated by the Borg, his immune system was able to fight off the nanoprobes long enough for him to find a means of killing them, although he admitted that his immune system would not be able to hold them off indefinitely.
The exact life expectancy of Denobulans is not known, but indications suggest that lifespans are extremely long. Phlox, in the 22nd century, once stated that his grandmother lived through Denobula's last war with the Antarans, a war which ended while Earth was in the 19th century. This indicates that at least three generations of Denobulans had existed during the three-hundred-year span between the events, suggesting a long lifespan.
The Denobulans believed they were the only intelligent species in the Milky Way Galaxy|galaxy until the B'Saari made first contact.
Denobulans fought Denobulan-Antaran wars|several wars against the Antaran race. The last one was during the late 19th century. Denobulan battle tactics killed twenty million Antarans. The Denobulans demonized the Antarans and made them a faceless enemy. As of the 22nd century, there were still some Denobulans that hated Antarans, although most had outgrown the hatred.
The Denobulans first met the Human race sometime prior to the 2130s. This was around the time Nathan Samuels was 18, and when his father was killed in a crash involving a Denobulan pilot. By the 2130s, Denobulans and Humans had built the joint research station Cold Station 12. When the Vulcans formed the Interspecies Medical Exchange, Denobulans were involved and contributed medical personnel.
In 2155, a Denobulan ambassador was sent to Earth to join in talks of forming a Coalition of Planets.