Patagonian mara: The monogamous rodents that mate only a few times a year but pee on each other constantly

Name: Patagonian mara (Dolichotis patagonum)

Where it lives: Arid grasslands and brush lands in central and southern Argentina

What it eats: Grasses, cacti, seeds, fruits, flowers and its own dung

Why it's awesome: Patagonian maras mate for life, and males are fiercely protective of their partners, following them wherever they go to shield them from other males and from predators. 

Despite their lifelong bond, mara pairs display virtually no physical contact apart from that seen during sex or when they're huddling together when it's cold.

Males occasionally sniff their partner's genitals, to which the female "usually responds by abruptly presenting her rump toward the male's face and discharging a jet of urine," according to a 1974 study.

Males also pee on their partners, all the while rubbing their anal glands and feces on the ground that the female previously occupied, to deter rival males. A male will "stand up on his hind legs and project a powerful jet of urine forwards onto the rump of the female, and she immediately responds by producing a jet of urine backwards onto the male's face," researchers wrote in the study. 

Related: Tufted ground squirrel: The Borneo rodent once believed to disembowel deer and feast on their organs

Patagonian maras — which grow to just under 30 inches (76 centimeters) in length — also have a unique breeding strategy, which involves rearing their young in communal dens shared by up to 22 pairs. Females are only sexually receptive three to four times a year during a 30-minute window known as estrus, which may explain why the species is monogamous. 

Estrus in Patagonian maras is so short that a male trying to mate with several females would struggle to strike while they were hot. Monogamy, on the other hand, helps ensure successful mating by keeping bonded members of a pair close together. 

The bond between a Patagonian mara couple is so strong that they can struggle to find a new mate if one of them dies, according to a 1987 PhD thesis, which documented a male "still alone" six weeks after his mate died, "despite the fact that there were several single females available."