What is Rutting?
Rutting is the mating season for certain mammals, particularly ungulates, which are hoofed animals such as deer, elk, and moose. This period marks a significant shift in animal behavior, transforming typically cautious animals into bold and active participants in reproduction. During the rut, males undergo heightened hormonal activity, leading to increased aggression and a pronounced interest in females. The term “rut” itself derives from the Latin word “rugire,” meaning “to roar,” reflecting some of the vocalizations common during this time.
It is a biologically defined period where competition among males intensifies to gain access to receptive females.
Why Animals Rut
The underlying purpose of the rut is to maximize reproductive output and ensure the continuation of the species. This annual physiological shift is primarily triggered by changes in photoperiod, the amount of daylight in a 24-hour period. As daylight hours decrease in autumn, a hormonal cascade begins, starting with increased melatonin production in the pineal gland. This rise in melatonin subsequently stimulates the production of other hormones, including a significant surge in testosterone in males.
This testosterone surge fuels muscle growth, thickens necks, and initiates antler hardening in males. It also rewires the brain for competition, leading to the aggressive and courtship behaviors observed during the rut. The females’ reproductive cycles are also precisely timed by photoperiod, ensuring they are receptive when males are most active. This synchronization allows fawns or calves to be born in the spring when food is plentiful and temperatures are favorable, increasing their chances of survival.
Observable Rutting Behaviors
During the rut, animals exhibit a range of distinct behaviors as males compete for breeding rights. Vocalizations are common, with elk known for their loud bugling, a drawn-out, high-pitched squeal that often ends with grunting. Moose produce grunting sounds, and red deer stags emit roars that carry over long distances. These calls serve to warn rival males and attract potential mates.
Antler use is prominent, as males spar and engage in direct fights to establish dominance. They also rub their antlers on trees and bushes, a behavior known as “rubbing” or “thrashing,” which helps shed velvet and marks their territory by depositing scent from glands on their heads.
Scent marking also involves urinating in scrapes, which are bare patches of ground, and depositing secretions from glands on their legs and between their toes. These scent posts convey information about the buck’s identity, age, health, and breeding condition. Males will also actively chase and herd females, attempting to keep them within their territory for mating. The intense activity and reduced feeding during this period can lead to significant weight loss in males, sometimes up to 20-30% of their body mass.
When and Which Animals Rut
The timing of the rut varies by species and geographic location, but it typically occurs in autumn in temperate regions. For instance, elk generally rut from mid-September to mid-October, while deer, including white-tailed and mule deer, often rut from late October through early December. Moose rutting usually takes place from mid-September through October.
Beyond these well-known species, many other ungulates exhibit rutting behavior. Bighorn sheep rut from late November through January, and mountain goats rut from late October through December. Pronghorn enter their rut from September to October, and bison engage in their breeding season from June to September. The exact timing can be influenced by factors such as climate and food availability, although photoperiod remains the primary trigger.