13. It's hard to figure out this connection, but what is a group of rattlesnakes?
From Quiz Unusual Collective Terms 2
Answer:
A rhumba
Rattlesnakes are venomous, creepy looking creatures from the family of pit vipers. There are at least 36 different species of them, and their favourite treats are small birds and rodents. Rattlesnakes do give predators, including man, the courtesy of warning them first with their distinctive rattle sound, and this can deter some attackers. Otherwise, they're goners. Rattlesnakes seldom bite unless threatened though, and you'll be pleased to know that their bites are seldom fatal for humans. Some consolation. I'd drop dead from the shock regardless of the bite.
Aha, here's a possible explanation for their collective term: During mating season, a receptive female leaves a trail of pheromones behind her and the male, once he picks up that scent, follows her around for days until she invites him in. However, if there are two males, they will often fight one another for that right, and, when they do get into a scuffle, they twist and intertwine around one another, darting and moving their heads about, until one cedes the battle. This is called a combat dance, and the rhumba grouping term followed on from that.