Reindeer and the quest for Scottish enlichenment

Area of Science:

• Animal behavior
• Visual ecology
• Mammalian physiology

Background:

• Reindeer (Rangifer tarandus) possess unique traits, including a color-shifting tapetum lucidum and a lichen-dominated diet.
• Their ocular media transmit significant ultraviolet (UV) light, potentially enabling UV vision.
• The adaptive advantage of UV sensitivity in a day-active, circum-Arctic mammal remains unclear.

Purpose of the Study:

• To investigate the potential role of UV vision in reindeer's ability to detect UV-absorbing lichens.
• To enhance the understanding of reindeer visual ecology, particularly in relation to their diet and environment.
• To explore how UV sensitivity might aid foraging in challenging Arctic conditions, such as during winter twilight.

Main Methods:

• Recorded reflectance spectra of various terricolous and fruticose lichens consumed by reindeer.
• Focused on lichens found in the diet of reindeer populations in Cairngorms National Park, Scotland.
• Analyzed spectral properties to determine UV absorption and reflection characteristics of key food sources.

Main Results:

• Lichens in the reindeer diet exhibit significant UV absorption.
• Snow surfaces reflect UV light, creating a contrast with UV-absorbing food sources.
• This spectral contrast is most pronounced under conditions with UV light availability.

Conclusions:

• UV visual sensitivity in reindeer could facilitate the detection of UV-absorbing lichens against snow.
• This adaptation may be particularly advantageous during periods of low light, such as winter twilight.
• The findings suggest a specialized visual system supporting survival and foraging in the Arctic environment.