Fig. 6. Series of thermograms of the harbour seal Henry obtained in summer (A–D) and winter (E–F). Note that the temperature range represented by the colour scale has been altered (16.8–37.0°C in A–D versus 6.0–33.0°C in E–F) in order to guarantee the best temperature resolution. (A) Arrangement of thermograms recorded after 10 min. Thermal windows have appeared on the hind flippers and in the dorsal neck/shoulder region (temperature range, 29.9–33.7°C), some comparatively small thermal windows have just appeared on the seal's back (31.1–32.6°C), while the other body regions are clearly colder (25.1–29.0°C). (B) Arrangement of thermograms recorded after 20 min and 21 min. Thermal windows have enlarged with slightly increased temperatures (30.2–35.1°C), and thermal windows are also visible on the right fore flipper (31.3–33.8°C). Although the area between thermal windows on the seal's back is already comparatively warm (approximately 29.3°C), the remaining body surfaces are still rather cold (25.6–28.1°C). (C) Arrangement of thermograms recorded after 29 min and 30 min. Thermal windows fuse to a rather coherent area (temperature range, 30.9–35.6°C), while the remaining body surfaces are still clearly colder (26.3–28.3°C). (D) Arrangement of thermograms recorded after 44 min and 45 min. Thermal windows have completely fused to a coherent area covering the seal's back and flippers (30.4–37.1°C). The lateral body regions clearly remain colder (26.2–28.1°C). (E) Arrangement of thermograms recorded after 44 min and 48 min. Some rather small thermal windows are visible on the seal's head and hind flipper region, while a fully developed thermal window covers the dorsal neck region (22.4–30.3°C). (F) Arrangement of thermograms recorded after 75 min and 77 min. While thermal windows seem not to have changed size, the thermal window covering the dorsal neck region shows a similar range of temperatures (22.3–30.1°C) but, on average, has become clearly cooler because high temperature areas within the thermal window have decreased in size. It can be speculated that this thermal window has already been closed and the respective body surface is now being cooled by the rather cold ambient air.