Whisker growth in wild Eurasian badgers Meles meles: implications for stable isotope and bait marking studies

The use of biomarkers such as stable isotopes to study the foraging ecology and movement of animals is a rapidly expanding area of research. With respect to mammals, the analysis of inert keratinous tissue such as whiskers (vibrissae) is particularly attractive as they can be sequentially sampled to provide a long-term time series of individual movement or diet. However, in order to interpret data from such tissues researchers require details of growth rates and patterns, and also how these vary within populations. In this study, we use the fluorescent biomarker Rhodamine B to measure vibrissa growth rate and patterns in a wild population of Eurasian badgers. In addition, we compare stable isotope ratio values of blood and vibrissae in order to test whether vibrissae are retained for long periods following growth. We found that badger vibrissae grow at an average rate of 0.43 mm?day^?1 (range 0.23–0.83) such that single vibrissae sampled for stable isotope analysis contain an average of 104 days of ecological data. Age, sex and body condition did not affect growth rate, and there was no evidence of consistent individual differences in growth rate or long-term retention of vibrissae following growth. However, variation in growth rate within the population suggest that the temporal scales reflected in vibrissae may vary both between and within individuals, such that results are not always directly, temporally comparable. This research provides useful information for any future research using vibrissae in combination with biomarkers to study mammalian ecology.