Postnatal growth and age estimation in the broad-tailed bat (Nyctinomops laticaudatus)

Abstract

Postnatal growth in bats has been studied in various species, but its documentation often depends on access to roosts, the ability to handle pups, and reliable marking systems for recapture. We examined the postnatal growth and development of the Broad-eared Free-tailed Bat (Nyctinomops laticaudatus) in a colony at the Governor’s Palace, Uxmal Archaeological Zone, Yucatán, Mexico. Marked pups were measured from birth until the onset of flight for forearm length, body mass, and fourth digit length. Growth curves were generated, from which growth rates and age-prediction equations were derived. At birth, forearm length, fourth digit length, and body mass were 45%, 29%, and 31% of postpartum female values, respectively. These traits grew linearly up to 40 days, with average rates of 0.44 mm/day (forearm), 0.54 mm/day (fourth digit), and 0.14 g/day (body mass). Growth rates slowed after the onset of flight. Forearm length provided a reliable predictor of age for pups between 1 and 40 days old when measurements were ≥37 mm. Flight trials indicated that pups began flapping and short horizontal movements at 15 days and achieved sustained flight by day 40. The growth rates observed in N. laticaudatus exceeded those reported for many other tropical insectivorous bats. Documenting postnatal development in molossids enhances our understanding of this critical stage in bat life history, and comparative studies across tropical species will provide valuable insights into the evolution of bat growth strategies.