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At the edge of a grove, away from the melee, a lonely bison mom and her calf were having a moment. The reddish brown calf was quite assertive, pushing its head into the mom’s groin, clearly letting her know what it wanted. I was probably not more than 25 meters from them, stuck in a bison traffic jam in the Bison Loop at Elk Island National Park. Mom and calf seemed not to mind my presence at all. I opened the sunroof of the truck and climbed out with my camera. This vantage point gave me an unobstructed view of the surroundings. As I was observing mom and calf I was surprised when I realize that the cow had horns, something I had assumed only male bison would have. It turns out that the physical differences that distinguish males (bulls) from females (cows) are quite subtle so determining a bison’s sex is not entirely trivial. Clearly the presence of horns cannot be used to tell males and females apart. Although a cow’s horns are slightly more curved and slender than a bull’s, one would likely have to be quite experienced to be able to pick up on this. Obviously a bison feeding a calf is one sure-way of positively identifying a female.

May the curiosity be with you. This is from “The Birds are Calling” blog (www.thebirdsarecalling.com). Copyright Mario Pineda.