Let your imagination run wild with the group names of the following animals.
A cling of koalas - When a baby koala is born, it is about the size of a jellybean. It is totally dependent upon its mother for survival and will live in her pouch for the first five to seven months of life. When it does climb out, it clings fiercely to its mother. If the cub happens to fall off and is uninjured, the mom will pick it up. If it happens to be injured after the fall, it is out of luck. Therefore,it is literally holding on for its life. Your character could have a child, spouse, or significant other that clings. Or she could be a teacher who looks upon her students as a cling of koalas.
A cloud of bats, flies, gnats, or grasshoppers - On August 21, 1880, a cloud of flies was seen in Nova Scotia.
In Austin, Texas, so many people want to see the cloud of bats that flies out from under Congress Avenue Bridge that it has become a tourist attraction.
A cloud of gnats is not something that I would want to ever witness, but in Camilla, Georgia they have an annual Gnat Days Festival, part of which is the Gnat Days 5K. I wonder, to win the 5K would you have to run through a cloud of gnats?
Clouds of grasshoppers still make invasions today. These mostly take place in Africa and bring total destruction to an area. You can read accounts of invasions and devestation that took place in the U.S. during the 1800s and early 1900s when these creatures swarmed farms and devoured field after field of crops.
A cluster of spiders - Just as a baby koala cling to its mother, baby wolf spiders will ride around in a cluster on the back of their mother. Baby spiders that don't ride around on the back of their mother can still be found in a cluster. I can see actual clusters of spiders being used in a creepy setting. I, for one, would not want to encounter them.
A clutch of birds or chicks - The term clutch is normally used when referring to a batch of eggs laid by birds or a group of baby chickens. A clutch of chicks could be used to describe a group of young females.
A clutter of cats or spiders - I picture cats being found in a clutter when they are sleeping. They seem to have a fondness for wrapping around each other.
A clutter of spiders refers more to adult spiders than babies, who ball up in a cluster. I haven't decided which would be more frightening – to find a cluster of baby spiders or a clutter of adult spiders. Again, I see a clutter of spiders being used in a mystery, suspense, or horror novel.
A coalition of cheetahs - Have you ever seen footage of a coalition of cheetahs hunting a zebra or gazelle? With their skill and cunning, they work together flawlessly to take down prey that is far larger than they are.
Members of a feared gang could be referred to as a coalition of cheetahs, as could members of a police force or swat team. "The pack of paramedics worked together to save those who had been injured in a bomb attack as flawlessly as a coalition of cheetahs chased down a gazelle."
A cohort of zebras - A cohort of zebras gathering at a waterhole puts me in mind of a group of coworkers gathering around the water dispenser at work to talk and exchange gossip.
A coil of rattlesnakes - Snakes will coil, sometimes around something, when they are rest. How fitting that a group of rattlesnakes is called a coil. “Like a coil of rattlesnakes just out of view, the gang of arsonists prepared to strike.”
A colony of ants, auks, badgers, bats, beavers, chinchillas, frogs, gulls, penguins, rabbits, rats, termites, or weasels - As you can see, colony is used to describe many different groups of animals, many of which could appear just as themselves in a story. A colony of termites could be used to take down a house, a colony of ants to destroy a picnic, or a colony of rats could terrorize a village during the time of the bubonic plague.
A comfort of cats - Cats are rather comforting animals, unless you happen to be allergic to them. You could have a character allergic to felines of any size kept prisoner in a house filled with a comfort of cats.
A company of badgers, moles, parrots, or widgeons (freshwater ducks) - I see a company of moles plotting how to take over the business run by a company of badgers. All of them are dressed in business suits.
A company of parrots, very noisy parrots, are in charge of the theme park of birds, the main attraction of which is a company of widgeons that live on and around their pristine lake.
A confusion of guinea fowl - A confusion of guinea fowl make a lot of noise. Imagine your anger and outrage if your neighbor owned a confusion of guinea fowl that woke you up bright and early each morning. Or a confusion of guinea fowl could be used to describe any annoying sound, say, a noisy neighborhood group of children.