I was taking a photo of “our” backyard squirrel and decided to do a little research. Apparently these squirrels are highly territorial. They are also ummm…ahem…reproducers, shall we say.
American red squirrels are spontaneous ovulators. Females enter estrus for only one day, but venture from their territory prior to ovulation, and these exploratory forays may serve to advertise their upcoming estrus. On the day of estrus, females are chased by several males in an extended mating chase. Males compete with one another for the opportunity to mate with the estrous female. Estrous females will mate with 4 to 16 males. Gestation is 31 to 35 days.
Red squirrels are highly territorial and asocial with very few non-reproductive physical interactions The majority of physical interactions are in male-female matings and between females and their offspring before the offspring disperse to their own territories. The non-reproductive physical interactions recorded were all instances of chasing an intruder from a territory.
This explains why every time the cat stands at the door, the squirrel yells at him.