Inbreeding: An Example in San Francisco

I’ve been documenting this family, on the same territory, for over eleven years now.

When this fella turned four, he and his mother (her first mate having been killed by rat poison several years before) produced four pups, three of whom survived to adulthood. By fall of that year, his mother-turned-mate disappeared, possibly killed by a car. So their one daughter then became the fella’s mate the following year: i.e., this mated pair are 1/2 siblings sharing the same mother, and he is her father. Yikes! Of the four litters they have produced over the last four years, only one female has survived to full adulthood. You might want to read about inbreeding depression. The consequences of inbreeding include lower fertility, higher infant mortality, higher susceptibility to diseases and parasites, and generally weakened systems.

Coyotes returned to San Francisco in 2002. There were only a handful of coyotes early on. It is very likely there may have been inbreeding in the population here prior to the time I began documenting this family.

Photos of the evolving inbred family

In 2008 the territorial family consisted of Mom, Dad, and one pup who I simply called “Yearling”. This was the first family unit I ever documented. A year later, this same mated pair had a second litter.

Mom and Dad’s second litter consisted of two males. Within weeks of their birth, Dad was killed by rat poison, leaving Mom single. She and her two male pups, Bruno and Silver, formed a tight-knit family which always did things together, but the male siblings who began as best friends eventually turned into arch-enemies, with the stronger-willed Silver driving his brother out: it appeared they were rivals and jealous for their mother’s attention and affection. If their father had been around, both males would have been driven out, preventing what then happened.


When Silver turned four years of age in 2013, he and Mom produced four offspring: mother and son had become a mated pair. This was the first inbred litter I documented.

One of their pups died as an infant leaving three. Then one male, Acorn was harshly dispersed at 9 months of age. That left two offspring, Chert [female] and Gumnut [male] who remained with their parents until one day in early November in the year of their birth, Mom suddenly vanished, possibly hit by a car. So now these two youngsters, Chert and Gumnut, began living with only their father Silver, (who was also their 1/2 brother), on the territory.

Siblings Chert and Gumnut became BFF — extreme buddies who played together and groomed each other constantly — from all appearances, they were destined to become a pair.

But Chert was the only female around and her father decided she would be his next mate. For months he tried driving off Gumnut who wouldn’t leave. And Chert was definitely bonded to Gumnut, making Silver’s task extremely difficult.

Silver (right) is Chert’s 1/2 brother and her father. Their reproductive success has been very low.

Silver and Chert (who is Silver’s daughter and 1/2 sister) become a pair. When Chert is two years old, she produces a litter: now the close inbreeding has been doubled. There is only one pup, Scout.

In the summer after Scout was born, Silver finally forces Gumnut (his son and 1/2 brother) to leave. [There actually is a chance that Gumnut could have fathered Scout. Scout adored Gumnut and vice-versa, but Silver’s domination and put downs would have been hard to get around — Silver perpetually physically placed himself between Scout and Gumnut to keep them apart. Scat DNA, which is all we have, is only able to identify the maternal lines.]

Litters have been born every year for four years to Silver and Chert, but no pups ever survived except Scout from their first litter. Scout is the only one.

I hope the genealogy is clear here. If you have questions, please send them in a comment (can be kept private). For a couple of short easy-to-read articles about inbreeding see these two articles: and