AbstractFreeze‐branding has proven useful in managing and researching a captive group of beaver (Castor canadensis) at the Minnesota Zoological Garden. Over 24 mo, 13 freeze‐brands were applied to the tails of 11 beaver for varying application times. Permanence of brands increased with increasing distance from tail base. Because permanence of freeze‐brands on cattle is influenced by skin thickness, the tail of a male beaver was horizontally sectioned into nine roughly equidistant segments, photographed to scale, and the epidermal/dermal thickness of the dorsal side of each section was measured to determine if skin thickness affected freeze‐branding success in beaver. Thickness of the epidermal and dermal layers of the dorsal tail surface decreased 14‐fold from tail base to tip. Based on our preliminary finding that freeze‐brand permanence improved with decreased thickness of the epidermal/dermal layers of the tail, we recommend that beaver be freeze‐branded for 25 s on the lower half of the tail for
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