Differences in fur cortisol levels of three migratory bats

Area of Science:

• Endocrinology and Wildlife Ecology
• Physiological responses to environmental factors in mammals

Background:

• Glucocorticoids (GCs) are key metabolic hormones reflecting an organism's physiological state and response to environmental changes.
• Measuring cortisol, a primary GC, in free-ranging mammal fur offers a non-invasive method to assess baseline hormone levels across different life stages.
• Bats, as the only flying mammals, present a unique model for studying environmental influences on metabolism and energetics.

Purpose of the Study:

• To determine baseline fur cortisol levels in three species of North American bats: hoary, silver-haired, and little-brown Myotis.
• To investigate interspecific differences in fur cortisol levels related to migration, hibernation, reproductive status, and age.
• To correlate cortisol levels with specific life history traits and environmental pressures in these bat populations.

Main Methods:

• Collection of fur samples from hoary (Lasiurus cinereus), silver-haired (Lasionycteris noctivagans), and little-brown Myotis (Myotis lucifugus) bats in southern Alberta and Saskatchewan.
• Analysis of fur samples to quantify baseline levels of cortisol, a primary glucocorticoid hormone.
• Comparison of cortisol levels across different species, sexes, age groups (adults vs. juveniles), and reproductive stages.

Main Results:

• Significant interspecific differences in baseline fur cortisol levels were observed among the studied bat species.
• Bats with longer migration distances exhibited higher fur cortisol levels compared to shorter-distance migrants that hibernate.
• Adults of silver-haired and hoary bats showed higher fur cortisol levels than juveniles, with no significant differences noted across reproductive stages.

Conclusions:

• Fur cortisol levels in bats can serve as a valuable indicator of physiological stress related to migration and energetic demands.
• Elevated cortisol in juvenile bats may reflect maternal hormonal transfer during lactation, highlighting the importance of maternal condition.
• Baseline cortisol measurements provide a non-invasive tool for assessing wildlife health and responses to environmental variability in undisturbed populations.