Black Berkshire Standard vs. Chocolate Berkshire Standard 5-month-old female rats. Rats owned and bred by Nicole Housel, Black Wolf Rattery. Photo ©2026 Karen Robbins.

Chocolate Variegated Standard (3 months) vs. Black Variegated Standard (7 months) male rats. Rats owned and bred by Nicole Housel, Black Wolf Rattery. Photo ©2026 Karen Robbins.

...and the back side of the Chocolate Variegated Standard (3 months) vs. Black Variegated Standard (7 months) male rats. Rats owned and bred by Nicole Housel, Black Wolf Rattery. Photo ©2026 Karen Robbins.

Silver Chocolate Dalmatian Standard female (9 months) vs. Silver Black Dalmatian Standard male (8 months) rats. Rats owned and bred by Nicole Housel, Black Wolf Rattery. Photo ©2026 Karen Robbins.

Black vs. Chocolate 24-day-old kitten rats, out of Chocolate and Black Berkshire (carried Chocolate). Rats owned and bred by Nicole Housel, Black Wolf Rattery. Photo ©2025 Nicole Housel.

Black vs. Chocolate 11-day-old kitten rats, out of Chocolate and Cinnamon (carried Chocolate). Rats owned and bred by Nicole Housel, Black Wolf Rattery. Photo ©2019 Nicole Housel.