The big brown bat (Eptesicus fuscus) reduces its body mass during winter in a tropical montane ecosystem of central Mexico

Most animals face changes in the availability of food and the environmental conditions in the places where they live. In response, they need to adjust their behavioral, physiological, and morphological traits. In temperate zones and high latitudes, bats increase their body mass (M b ) in autumn to store fat reserves and use them during hibernation. However, other small mammals decrease their M b prior to winter to reduce the energetic requirements of individuals. These changes are unknown for bats inhabiting other highly energetic demanding environments. We measured changes in M b of 84 non-reproductive males of Eptesicus fuscus inhabiting a tropical montane ecosystem in central Mexico over seasons. We also examined the relationship of bats’ M b with the minimum ambient temperature (T a , °C) and mean precipitation (mm). Bats presented an increase in M b from March to June, followed by a decrease from September to November and presented the lowest M b from November to March, in the dry-cold season. The results suggest that the pattern of changes in M b could be the result of two non-exclusive components related to the bats’ energy budget, the energetic demands experienced by the bats throughout the year and the morphological adaptations animals could display to reduce their energy requirements during the winter.

Effect of diet quality and ambient temperature on the use of torpor by two species of neotropical nectar-feeding bats

Neotropical bats use torpor as a strategy to save energy when they experience a low energy intake and/or low ambient temperature (T_a). Digestive physiology limits the energy intake of several glossophaginid bats, and could play an important role in the onset of torpor in these tropical animals. We measured the effect that diet quality and T_a had on the use of torpor by the nectar-feeding bats Glossophaga soricina and Leptonycteris yerbabuenae Captive bats were fed with 5% (low) or 35% (high) sucrose solutions while exposed to two different T_a (17.7 and 23.2°C; low T_a and high T_a) in four different treatments: (1) high sucrose:high T_a, (2) high sucrose:low T_a, (3) low sucrose:high T_a and (4) low sucrose:low T_a We measured their energy intake, changes in body mass (ΔM_b) and skin temperature (T_skin) as response variables. Energy intake (in 10 h) was limited when both species fed on 5% sucrose, but body mass gain was only affected in G. soricina. Energy intake and T_a had a negative effect on the minimum T_skin of both species, and ΔM_b affected the time that G. soricina used torpor. Both species remained normothermic on the high sucrose:high T_a treatment, but used torpor on the other three treatments. Bats used torpor during their resting and activity periods. Leptonycteris yerbabuenae spent more time in torpor in the low sucrose:high T_a treatment, while G. soricina used this strategy for longer periods of time in the high sucrose:low T_a treatment. We found that diet quality and T_a played an important role in the use of torpor by nectar-feeding bats.

Bat fauna associated with artificial ponds in La Malinche National Park, a mountain ecosystem of Mexico

An increase in water demand in mountains has reduced its availability for the fauna. As conservation tools, artificial ponds can be used to offer water to animals. Many studies have assessed the use of ponds by bats. However, most of them have been concentrated in the United States and Europe, while in regions with higher bat diversity the information is scarce. We captured the bat species associated with artificial ponds in a Mexican mountain where water was intubated 25 years ago. We identified and analyzed the bats’ species proportion and sex ratio and evaluated if species richness and abundance were affected by season, mean monthly precipitation, maximum monthly temperature and maximum monthly humidity. We captured 90 bats of seven species (Vespertilionidae), where