Fig. 3. Series of thermograms of the harbour seal Nick showing the process of fusion of thermal windows in detail. (A) Thermogram recorded after 7 min. Two solitary thermal windows with surface temperatures 15 K higher than those in the surrounding areas have appeared on the left lateral neck region. A temperature profile line (inset) shows the first stage of fusion of these thermal windows. The surface temperature between thermal windows is elevated (approximately 21°C) but is clearly lower than temperatures within the thermal windows (approximately 29–31°C; see inset). (B) Thermogram recorded after 11 min. Fusion of thermal windows 1 and 2 is almost complete, but both thermal windows can still be identified. A temperature profile line shows only a slight decrease of temperatures between thermal windows (see inset). (C) Thermogram recorded after 50 min. Fusion is complete, the resulting thermal window has further enlarged and former thermal windows 1 and 2 can no longer be identified. A new thermal window (No. 3) with slightly elevated surface temperatures (see also inset) has just appeared. (D) Thermogram recorded after 55 min. Thermal windows have further enlarged. The new thermal window, No. 3, almost reaches the peak temperature of the old thermal window, while the region in between the thermal windows is still cold (see inset).