Night howlers

Night howlers (also known as Midnicampum holicithias) are toxic flowers that can turn civilized animals aggressive. Bellwether and Doug use the flower to concoct a drug to turn predator animals savage, including Mr. Manchas the black jaguar and Mr. Otterton the otter.

Description
The night howlers are small-medium flowers that have six violet petals and several yellow pistils and stamens. Night howlers are grown from root bulbs, which can be mistaken for onion bulbs.

Effects
Night howlers contain psychotropic chemicals that have deadly effects on animals exposed to them. However, concentrated amounts of the plant's chemicals will cause larger animals to become savage if they are exposed, causing them to lose higher reasoning functions and violently lash out at anything that moves. The night howler's chemicals can even affect animals that do not have a naturally violent or ferocious disposition - as evidenced by their ability to turn non-predator animals, such as rabbits, aggressive.

Bonnie and Stu Hopps mentioned that Bonnie's brother, Terry, once ate one whole and went berserk, attacking Bonnie and injuring her arm.

Usage
As natural flowers, night howlers can kill small animals such as insects, which makes them an effective pesticide. This does not mean they are no longer lethal towards mammals in this phase however, but it is not enough to revert them to a fixed state of violence. Stu uses the plants to scare off bugs from his crops, but has his children stay away from them to prevent exposure.

Bellwether orchestrated a plot to use night howler chemicals to make every predator in Zootopia savage, giving the illusion that they are biologically reverting back to their "primitive savage ways". One of her henchmen, Doug, uses his chemist expertise to modify the flower into a concentrated pellet, which can be loaded into a dart for long-range injections. Doug uses his sniper aim to dart every predator he can, especially ones that could risk exposing the plot. Duke Weaselton was paid to steal bulb roots of the plant for Doug to create night howler pellets.

After Bellwether was exposed and arrested, doctors created an antidote for the infected predator mammals, including Mr. Otterton, who was reunited with his wife.

Role in the film
The night howlers were mentioned early on as one of the last things Mr. Otterton said before going savage. At the time, Judy and Nick assumed that it meant that wolves were involved in the disappearances of the other animals around Zootopia. Judy also thwarted one of Duke Weaselton's thefts of night howler bulbs, although the owner of the store believed them to be onion bulbs at the time.

The flowers themselves first appeared at Bunnyburrow where Stu uses them to scare off bugs away from his crops. When she heard about the psychotropic effect they had on animals, Judy realized that she made an error - "night howlers" referred to the plant, not the wolves - and rushed back to Zootopia.

After reconciling with Nick, the duo get information from Duke, who was doing it for money. He states that he did it for Doug in an underground subway. Judy and Nick go to the subway, which is filled with night howlers being used in experiments, and they watch Doug liquefying them into a serum. Doug then gets a phone call informing him of his next target, making Judy realize that the night howler toxins are responsible for making Mr. Otterton (as well as Mr. Manchas whom she and Nick had met earlier) go savage.

At a museum, Judy and Nick discover that Bellwether is the mastermind behind the night howler plot. After getting them into a pit, she fires a dart at Nick, intending to make him go savage and kill Judy to conceal her role in the plot. The seemingly savage Nick appears to bite Judy, but it is all an act; the duo had replaced the night howler serum with blueberries from Judy's farm before Bellwether reclaimed them. Bellwether threatens to frame the two like she did with Mayor Lionheart, but Judy reveals that she has recorded the former's confession with the latter's carrot pen, just as Chief Bogo and his Zootopia Police Department forces arrive and arrest her.

At the end, an antidote for the night howlers was created, curing all infected predators, including Mr. Otterton.

Trivia

 * According to Judy, the night howlers are related to the variety and are a class C botanical.
 * The word "Midnicampum" is loosely derived from Latin meaning "between the fields", while "holicithias" has Greek connotations as "all shepherd", alluding to the plant's use as a field pesticide.
 * Alternatively, the plant's nomenclature parallels the colloquial name: "Midnicampum" is similar to "midnight", "holicithias" is close to the word "howl" when pronounced phonetically.
 * Victims of the night howlers cannot spread the savage disease into others. This was shown when a bite from a savaged rabbit did not affect Bonnie when she was younger, nor did Manchas become savage by an infected Mr. Otterton, despite sustaining severe cuts and slashes from the encounter.
 * In an early draft of Zootopia, night howlers only caused animals to revert to their feral instincts instead of making them mindlessly violent. In this draft, Nick was successfully infected by Bellwether, but did not attack Judy since his instincts saw Judy as something to protect, due to their established friendship.
 * Judy and Nick mistake the name "night howlers" to refer to the wolves who work at the Cliffside Asylum, since wolves tend to howl at night, hence the name "night howlers".
 * As a side effect of night howlers exposure, the eyes of infected animals will typically resemble those of their real-life counterparts.