The intake responses of three species of leaf-nosed Neotropical bats

Abstract

Flower-visiting bats encounter nectars that vary in both sugar composition and concentration. Because in the new world, the nectars of bat-pollinated flowers tend to be dominated by hexoses, we predicted that at equicaloric concentrations, bats would ingest higher volumes of hexoses than sucrose-containing nectars. We investigated the intake response of three species of Neotropical bats, Leptonycteris curasoae, Glossophaga soricina and Artibeus jamaicensis, to sugar solutions of varying concentrations (292, 438, 584, 730, 876, and 1,022 mmol L(-1)) consisting of either sucrose or 1:1 mixtures of glucose and fructose solutions. Bats did not show differences in their intake response to sucrose and 1:1 glucose-fructose solutions, indicating that digestion and absorption in bat intestines are designed under the principle of symmorphosis, in which no step is more limiting than the other. Our results also suggest that, on the basis of energy intake, bats should not prefer hexoses over sucrose. We used a mathematical model that uses the rate of sucrose hydrolysis measured in vitro and the small intestinal volume of bats to predict the rate of nectar intake as a function of sugar concentration. The model was a good predictor of the intake responses of L. curasoae and G. soricina, but not of A. jamaicensis.

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

“…This diet was designed by Mirón M et al (2006), and allowed us to maintain colonies of these species for up to 8 months previously (see Ayala-Berdon et al, 2008, 2009Rodríguez-Peña et al, 2007). Bat activity was monitored using infrared video (DigiOpG2 ® , USA).…”

“…While L. yerbabuenae reduces its energy intake by about 30% when nectar sugar concentration decreases from 35% to 5%, G. soricina decreases its energy intake by 60% in the same range of sugar concentrations (see AyalaBerdon et al, 2008AyalaBerdon et al, , 2009. In these species, the differences in monosaccharide absorption/transport rates and gut size are the main mechanisms controlling the amount of energy that the animals are able to process per unit of time (Martínez del Rio, 1990;Hernández and Martínez del Rio, 1992;Ayala-Berdon et al, 2008). We hypothesized that both species should use torpor when their physiological constraints limit their energetic intake to close-to or below the energetic costs imposed by T a .…”

“…Nectar abundance and quality and the T a they confront in the field limit their energetic budget. Ayala-Berdon et al (2008) found that the energy intake of three species of bats became limited when they fed on dilute nectar, and that in one species, this reduction in energy intake increased when facing low T a (Ayala-Berdon et al, 2009). While the effects that energetic constraints related to sugar concentration (Ramírez P et al, 2005;Ayala-Berdon et al, 2008, 2009, 2013, nectar availability (Kelm and von Helversen, 2007) and foraging behavior have on the physiological ecology of bats have been evaluated in the past, the role that the interaction between diet quality, which could limit energy acquisition (Martínez del Rio et al, 2001;Ayala-Berdon et al, 2008, 2009, and T a has on the use of torpor in tropical nectar-feeding bats remains poorly explored (but see Kelm and von Helversen, 2007).…”

“…However, because of dissimilarities in digestive physiology and body mass, we expected to find differences in the use of torpor by these two tropical bat species. Because of its lower digestive capacity (Ayala-Berdon et al, 2008;, L. yerbabuenae should be more prone to using torpor than G. soricina when feeding on low-quality diets when T a is not a limiting factor (i.e. high T a ).…”

“…Neotropical nectar-feeding bats (like G. soricina) are small-sized animals that live on the verge of a negative energetic balance (Cruz-Neto and Abe, 1997;von Helversen and Winter, 2003;Ayala-Berdon et al, 2008). Nectar abundance and quality and the T a they confront in the field limit their energetic budget.…”