Comparison of the healing process in hot and cold brands applied to harbour seal pups (Phoca vitulina)

Abstract

Hot branding has been used for many years by researchers to identify seals from a long distance. In livestock, cold branding has been proposed as an alternative because it is thought to be less painful. The purpose of this study was to compare the healing process of hot and cold brands applied to harbour seal pups (Phoca vitulina). A total of 306 animals was branded with a unique set of four characters: three applied for 3–5 s with an iron heated to 500°C, and one applied for either 10 or 20 s with an iron frozen to –175°C. At three subsequent times over 10 weeks, 43, 41 and 51 animals, respectively, were recaptured, the macroscopic appearance of their brands recorded, and biopsies taken for microscopic examination. Cold brands had a faster healing rate than hot brands. However, they resulted in less destruction of hair follicles, and cold brands applied for 20 s caused more depigmentation. Regrowth of hair follicles could subsequently obscure brands, while depigmentation reduces the contrast between the brand and the surrounding fur. Cold brands applied for 20 s also caused more extensive deep vascular damage, which subsequently may have resulted in deeper wounds in some of these brands. Yet, macroscopically, other cold brands, or portions thereof, were almost invisible. On the basis of this short-term study, the technique of cold branding that we used in harbour seals does not appear to be as reliable as that of hot branding to provide permanent legible brands.

Permanent marking in an endangered species: physiological response to hot branding in Steller sea lions (Eumetopias jubatus)

“…Public concerns over the visually unappealing method have halted research programs with multiple pinniped species (e.g. Jabour- Green and Bradshaw 2004;Dalton 2005;Daoust et al 2006). However, the current study indicates that sea lions are fully capable of rapid recovery from the process, and evidence of high survival rates in other branded pinnipeds suggests a similar capacity for recovery in other species (e.g.…”

Branding the seal branders: what does the research say about seal branding?

“…It has been suggested that cryo‐ or freeze branding may be a less painful and more effective way to mark seals, but this has been questioned in two recent studies 12,17 . The efficacy of cryo‐branding was trialled at Macquarie Island but all cryo‐brand marks were lost after one year, and no seals were identified in subsequent years from these marks 12 .…”

Maternal and offspring effects on the timing of parturition in western Steller sea lions (Eumetopias jubatus)

“…Adult females (n = 152) with unique brands, tags, or natural markings were tracked throughout the breeding season and across multiple years in most cases. Hot-iron branding is widely accepted as the safest and most appropriate means to permanently mark pinniped species (Merrick et al 1996;Daoust et al 2006;McMahon et al 2007). Branding and all related work was conducted in accordance with Alaska SeaLife Center's IACUC Animal Use Protocol No.…”