This document summarizes a study monitoring the endangered Mexican long-nosed bat at a maternity cave in Mexico. The researcher conducted visual counts and captured bats using mist nets in May and June 2013 to understand the species' population size, reproductive conditions, and timing of migration to the cave. Results showed bats arriving later than previous years, with few observed in May but numbers increasing in mid-June. This suggests a delay in migration that may have been caused by drought conditions reducing food availability until rains in May. Continued monitoring is still needed to accurately assess the population.

1. Results
Monitoring the endangered Mexican long-nosed bat
(Leptonycteris nivalis) at a maternity cave in Nuevo Leon, MX
Rachel Saker
Applied Biodiversity Science, Texas A&M University, College Station, TX
Abstract / Introduction
• Mexican long-nosed bats (Leptonycteris nivalis)
• Specialized desert & forest dwelling cave bat
• Feed on nectar of flowering plants
• Range from Mexico to southwestern USA
• Important pollinators of Agave spp.
• Migrate north in summer, following agave bloom
• Females give birth in specific maternity caves
• Endangered species
• Dramatic population declines (50% in 10 years)
• Habitat loss & roost disturbance most damaging
• Two known maternity caves for entire species
• Protection of maternity caves critical
• Mt. Emory Cave, Big Bend Nat’l Park, TX, USA
• Consistently monitored via thermal cameras
• El Infierno Cave, Nuevo Leon, MX
• Digital monitoring not appropriate
• All monitoring by visual observation only
• Specimens captured for measurement
Objectives
• Monitor the remotely located Infierno cave
• Conducted during
migration
• Utilize visual counts and
mist net “traps”
• Purpose of Observations
• Better understand
species’ fitness
• Determine arrival time to
maternity cave
• Record nightly
emergence activity
• Estimate population size
• Assess colony’s reproductive condition
• Site selection: Infierno cave
• Only known maternity roost in Mexico
• Located in Parque Nacional Cumbres
de Monterrey, near northern end of the
species’ migration range
• Potential final destination of migration
• Not frequently monitored
• Timing of study
• Conducted during May & June, 2013
• Dates selected based on population
peaks during annual migrations from
previous years
• Visually observing emergence
• Red spotlights used at dusk/dawn
• Two observers stationed at cave
entrance
• Recorded number of bats exiting
& entering the cave
• Trends in population over time
• Capturing specimens for assessment
• Mist nets used for live-trapping
• Placed along entrance of cave
• Opened at dusk & before dawn
• Also helps identify other species
using the cave
• Physical measurements recorded per captured specimen
• Approximate age (adult vs. subadult)
• Sex & reproductive status
• Evaluate current breeding cycle of
colony (i.e.: active pregnancy, post-
birth, inactive; sexually immature)
• Weight
• Length of forearm
• Additional qualitative observations
conducted inside the cave (May only)
• Auditory (by human ear)
• Active colonies are noisy, “chatter”
• Examination of guano as well as the
presence and condition of bat remains
• L. nivalis guano is easily distinguished from insectivore bats’ guano due
to its bright yellow coloration (from nectar/pollen diet)
• Guano freshness subjectively estimated by amount of mold growth
• Some dying/dead bats on the floor of a cave with active colonies is common
Methods & Materials
Location of El Infierno Cave within Parque Nacional
Cumbres de Monterrey; indicated by pointer.
Survey map (profile, cut-away) of El
Infierno Cave. L. nivalis known to roost
along ceiling on the western side.
Number per sex / age:
Dates, Species
Total
captured:
♀
adult
♀
juv.
♂
adult
♂
juv.
May 17-20
Myotis thysanodes 3 2 1
Myotis californicus 1 1
Leptonycteris nivalis 3* 2
Myotis spp. 2 1 1
May 25
Myotis spp. 1 1
June 15-16
Leptonycteris nivalis 25* 7 5 3 9
Myotis thysanodes 3 3
Lasiurus cinereus 1 1
* indicates one specimen escaped before measurements were taken
Acknowledgements
This opportunity was only possible through the generous small research grant awarded
by the Applied Biodiversity Sciences Department of Texas A&M and by the constant
guidance of Emma Gomez-Ruiz. Mrs. Gomez-Ruiz was and still is an invaluable resource
for my developing academic career; her patience and altruism is without match. I would
also like to thank Dr. Thomas Lacher and Leslie Ruyle for their guidance throughout
this experience. Additional funding was provided by the Mohammed bin Zaved Species
Convservation Fund and Bat Conservation International. Equipment and vehicle support
was made possible by Especies, Sociedad, y Habitat, A.C., Jim “Crash” Kennedy, and
the Aggie Speleological Society. Field assistance was provided by Emma Gomez-Ruiz,
Citlally Jimenez, and Scott “Get-a-Watch” Grimes.
I am examining an L. nivalis after removing it from the mist
nets. The bat was measured then released into the cave.
On rope and ready to descend the 180ft pit into the cave.
Specialized caving equipment and training is required
for accessing the inside of the cave.
Conclusion & Discussion
• L. nivalis arrived later in the summer this year
• Previous studies: colony size peaks May to June; numbers
taper off by late-June
• Current study: observed bats very low until mid-June, then
significant increase in activity; follow-up conducted in late-July
observed few bats
• Observations within cave (conducted in May) found little bat
activity during daytime and evening hours.
• Results suggest a delay in that summer’s migration
• Hypothesized causes for migration delay
• Ranchers in area reported drought in spring, continued into
early summer
• Agave bloom delayed due to dry conditions
• Limited locally available food for nectar bats
• Multiple rainstorms occurred during May
• Possible the migration began after the rains, coinciding with
an increase in local agave blooms
• Survey cannot provide an accurate estimation of the size &
wellbeing of the population due to the poor sample size
• Continuation of monitoring needed for more accurate
evaluation of the L. nivalis population
Date Start time
East West
May 18 20:40 2 out, 1 in 3 out
May 24 Rained no bats
May 25 21:00 8 out, 3 in 3 out, 1 in
June 14 21:00 8 out, 3 in 2 out
June 15 20:45 18 out, 8 in 10 out, 3 in
June 16 21:00 136 out, 30 in 19 out, 14 in
Visual observations, exiting/entering cave
Counts per stationed observer:
Tally of bats caught with mist nets