Moulting matters: the importance of understanding moulting cycles in bats when using fur for endogenous marker analysis

Abstract

Endogenous markers are a valuable indicator of individual animal ecology, but data interpretation requires a detailed understanding of the timing of tissue formation. Fur is commonly used in bat research using endogenous markers, but the moulting cycles of most bat species are not well documented. In this review, we (i) describe methods of investigating bat moulting; (ii) summarize the current literature on bat moulting cycles, highlighting broad trends; (iii) discuss knowledge gaps; and (iv) make recommendations for optimal fur sampling protocols. Three characteristics may indicate moulting in bats: changing skin pigmentation; visible fur growth and colour changes; and endogenous markers. Most studies reported new fur growth once annually during summer-fall, although there were exceptions. The timing of new fur growth varies among species, sexes, and age classes. Individuals commonly experience asynchronous new fur growth, with dorsal fur growth occurring before ventral. Specific moult progressions vary among species. Knowledge gaps include moulting cycles in tropical species and in subadult and yearling bats; migration during new fur growth; and the timing of fur growth compared with shedding. We recommend that fur samples taken dorsally from adult males are the most likely to be representative of the bat's site of summer residency.Résumé : Si les marqueurs endogènes constituent un indicateur utile de l'écologie individuelle des animaux, l'interprétation de ces données nécessite une compréhension détaillée du moment de la formation des tissus. Bien que le poil soit couramment utilisé dans la recherche sur les chauves-souris axée sur des marqueurs endogènes, les cycles de mue de la plupart des espèces de chauves-souris ne sont pas bien documentés. Dans le présent article, nous (i) décrivons des méthodes permettant d'étudier la mue des chauves-souris, (ii) présentons une synthèse des travaux existants sur les cycles de mue des chauves-souris pour en faire ressortir de grandes tendances, (iii) abordons les lacunes sur le plan des connaissances et (iv) formulons des recommandations relatives à des protocoles optimaux d'échantillonnage du poil. Trois caractéristiques pourraient indiquer qu'une chauve-souris est en mue, à savoir : un changement de la pigmentation de la peau, la croissance et des changements de couleur visibles des poils, ainsi que des marqueurs endogènes. Bien qu'il existe des exceptions, la plupart des études font état d'une croissance de nouveaux poils une fois l'an, à l'été-l'automne. Le moment de la croissance de nouveaux poils varie selon l'espèce, le sexe et la classe d'âge. Les individus présentent souvent une croissance non synchrone de nouveaux poils, la croissance des poils dorsaux étant plus hâtive que celle des poils ventraux. La progression de la mue varie également selon l'espèce. Les lacunes sur le plan des connaissances touchent notamment aux cycles de mue des espèces tropicales et des chauves-souris subadultes et d'un an, à la migration durant la croissance de nouveaux poils et au mo...

Origins and migratory patterns of bats killed by wind turbines in southern Alberta: evidence from stable isotopes

“…This timing of molt is similar to that observed in other bat species (Cryan et al 2012, Fraser et al 2012, Fraser et al 2013). Thus, fur collected along the migratory route is fur grown on the summering grounds during the current year's molt.…”

“…Although no formal studies have been conducted on the molting patterns of either hoary or silver-haired bats (but see review by Fraser et al 2013), observational and isotopic data suggest that both species molt on their summering grounds just prior to migration, thus between late June and early August (Cryan et al 2004; E. F. Baerwald and B. J. Klug, personal observation). This timing of molt is similar to that observed in other bat species (Cryan et al 2012, Fraser et al 2012, Fraser et al 2013).…”

Getting ready for the winter: Timing and determinants of molt in an alpine ungulate

“…Most studies on mammals assessed histological processes and provided descriptive analyses of hair follicle growth (Blix et al, ; Cuyler & Øritsland; Nixon, Gurnseyb, Betteridgec, Mitchellc, & Welchc, ). Some studies, however, also investigated the factors affecting molt timing, such as age class, reproductive status (Cowan & Raddi, ; Fraser, Longstaffe, & Fenton, ; Zimova et al, ), individual condition, or access to food resources (Heydon, Milne, Brinklow, & Loudon, ; Macdonald & Stewart, ). In addition, photoperiod has been found to influence mammalian molt processes (Lynch, ; Nixon, Ashby, Saywell, & Pearson, ), especially in high‐latitude environments (Ling, ).…”

Habitat use of migratory bats killed during autumn at wind turbines

“…), which is most often finished in mid‐summer in bats of the Northern hemisphere (Fraser et al. ). In N. noctula and P. nathusii , fur changes between late June/early July and mid‐August (Heise , Schmidt , Ilyin , Gebhard and Bogdanowicz , Spitzenberger ), which suggests that these two species have new fur when migrating to their wintering sites in autumn.…”