Dietary composition and echolocation call design of three sympatric insectivorous bat species from China

The Consumption and Diversity Variation Responses of Agricultural Pests and Their Dietary Niche Differentiation in Insectivorous Bats

Insectivorous bats are generalist predators and can flexibly respond to fluctuations in the distribution and abundance of insect prey. To better understand the effects of bats on arthropod pests, the types of pests eaten by bats and the response of bats to insect prey need to be determined. In this study, we performed DNA metabarcoding to examine prey composition and pest diversity in the diets of four insectivorous species of bats (Hipposideros armiger, Taphozous melanopogon, Aselliscus stoliczkanus, and Miniopterus fuliginosus). We evaluated the correlation between bat activity and insect resources and assessed dietary niche similarity and niche breadth among species and factors that influence prey consumption in bats. We found that the diets of these bats included arthropods from 23 orders and 200 families, dominated by Lepidoptera, Coleoptera, and Diptera. The proportion of agricultural pests in the diet of each of the four species of bats exceeded 40% and comprised 713 agricultural pests, including those that caused severe economic losses. Bats responded to the availability of insects. For example, a higher abundance of insects, especially Lepidoptera, and a higher insect diversity led to an increase in the duration of bat activity. In areas with more abundant insects, the number of bat passes also increased. The dietary composition, diversity, and niches differed among species and were particularly significant between H. armiger and T. melanopogon; the dietary niche width was the greatest in A. stoliczkanus and the narrowest in H. armiger. The diet of bats was correlated with their morphological and echolocation traits. Larger bats preyed more on insects in the order Coleoptera, whereas the proportion of bats consuming insects in the order Lepidoptera increased as the body size decreased. Bats that emitted echolocation calls with a high peak frequency and duration preyed more on insects in the order Mantodea. Our results suggest that dietary niche differentiation promotes the coexistence of different bat species and increases the ability of bats to consume insect prey and agricultural pests. Our findings provide greater insights into the role of bats that prey on agricultural pests and highlight the importance of combining bat conservation with integrated pest management.

Food habits of two species of tube-nosed bats, Murina hilgendorfi and Murina ussuriensis, in Hayakawa, central Japan

Knowledge of food habits is essential for understanding the life history of a species; however, such information about the enigmatic Murina genus of bats is little known. In this study, we examined the food habits of Murina hilgendorfi and Murina ussuriensis over four years in Hayakawa, central Japan, using traditional morphological fecal analysis. Fragments of arthropods of six orders (five identified families), and of five orders (five identified families), were found in the feces of M. hilgendorfi and M. ussuriensis, respectively. Both species consumed wingless arthropods (caterpillars and spiders), insects that rarely fly (ground beetles and bush crickets), or diurnal insects (dragonflies and hoverflies; i.e., that are resting at night) during the night, which is a clear indication of gleaning behavior in these bats. In spring, the large-bodied M. hilgendorfi more frequently consumed hard-bodied insects such as beetles and bush crickets, whereas the small-bodied M. ussuriensis more frequently consumed soft-bodied insects such as caterpillars, moths, spiders, and dipterans, suggesting that the body size difference influences their food habits, which may have contributed to food resource partitioning between these closely related bats. For M. hilgendorfi, beetles were the main prey in spring and autumn, while caterpillars and grasshoppers were more frequently consumed in spring and autumn, respectively, suggesting that they may have changed prey items according to seasonal fluctuations in food availability. To our knowledge, this study provides the first record of differences in the food habits of these two species.

Differences in Diet and Gut Microbiota Between Lactating and Non-lactating Asian Particolored Bats (Vespertilio sinensis): Implication for a Connection Between Diet and Gut Microbiota

In mammals, lactation is considered the most energetically costly phase for females. To meet nutritional and energy demands, lactating females usually change feeding patterns by eating food that is higher in protein and calories. Their gut microbes respond accordingly to help adapt to the changes in diet. In this study, we examined differences in diet and gut microbial composition between lactating and non-lactating Asian particolored bats (Vespertilio sinensis) using COI and 16S amplicon sequencing. When compared with non-lactating bats, we found that the diversity and composition of lactating bats' diets differed; the proportion of Diptera increased and Coleoptera and Orthoptera decreased significantly. This could be attributed to the easy availability and high protein content of Diptera. Comparative analysis of the gut microbiota of lactating and non-lactating females showed that although the diversity of gut microbiota did not change, the relative abundance of specific gut microbiota associated with a particular diet did change. For example, when the consumption of Coleoptera decreased in lactating bats, the relative abundance of Lactobacillaceae was also reduced. Lactobacillaceae are thought to be involved in the digestion of Coleopteran exoskeletons. This study suggests that during lactation, Asian particolored bats eat a diet that yields higher levels of protein, and at the same time, the abundance of specific gut microbes change to help their hosts adapt to these changes in diet.

Roosting ecology of endangered plant-roosting bats on Okinawa Island: Implications for bat-friendly forestry practices

Roosting information is crucial to guiding bat conservation and bat-friendly forestry practices. The Ryukyu tube-nosed bat Murina ryukyuana (Endangered) and Yanbaru whiskered bat Myotis yanbarensis (Critically Endangered) are forest-dwelling bats endemic to the central Ryukyu Archipelago, Japan. Despite their threatened status, little is known about the roosting ecology of these species and the characteristics of natural maternity roosts are unknown. To inform sustainable forestry practices and conservation management, we radio-tracked day roosts of both species in the subtropical forests of Okinawa's Kunigami Village District. We compared roost and roost site characteristics statistically between M. ryukyuana nonmaternity roosts (males or nonreproductive females), maternity roosts, and all M. yanbarensis roosts. Generalized linear models were used to investigate roost site selection by M. ryukyuana irrespective of sex and age class. Lastly, we compiled data on phenology from this and prior studies. Nonreproductive M. ryukyuana roosted alone and primarily in understory foliage. Murina ryukyuana maternity roosts were limited to stands >50 years old, and ~60% were in foliage. Myotis yanbarensis roosted almost entirely in cavities along gulch bottoms and only in stands >70 years old (~1/3 of Kunigami's total forest area). Murina ryukyuana maternity roosts were higher (4.3 ± 0.6 m) than conspecific nonmaternity roosts (2.3 ± 0.5 m; p < .001) and M. yanbarensis roosts (2.7 ± 0.5 m; not significant). Model results were inconclusive. Both species appear to be obligate plant roosters throughout their life cycle, but the less flexible roosting preferences of M. yanbarensis may explain its striking rarity. To conserve these threatened bats, we recommend the following forestry practices: (a) reduce clearing of understory vegetation, (b) refrain from removing trees along streams, (c) promote greater tree cavity densities by protecting old-growth forests and retaining snags, and (d) refrain from removing trees or understory between April and July, while bats are pupping.

Body mass explains digestive traits in small vespertilionid bats

Bats are unique among mammals in that they have evolved the capacity to fly. This has generated strong selective pressure on the morphology and function of their digestive system. Given that in bats intestinal length and nominal surface-area are proportional to body mass, this trait importantly relates to explaining some of their digestive characteristics. We described the relationship between digestive traits and body mass of four species of bats of the family Vespertilionidae living in a montane ecosystem in central Mexico. We calculated food transit time, apparent dry matter digestibility, and defecation rate in feeding trials under captive conditions. We also: (1) built a model of the relationship between digestive traits and body mass to determine if this association was consistent within the members of the family Vespertilionidae, and (2) mapped these traits along the phylogeny to explore how digestive characteristics may have evolved. In our feeding trials, body mass was positively related to transit time and negatively related to apparent dry matter digestibility. The model predicted accurately the transit time in bats with body mass < 20 g. The phylogenetic approach suggested that over the evolutionary history of the family, transit time decreased as digestibility increased. Because of the results obtained here, it is likely that for most bats of the family Vespertilionidae, adaptations in digestive traits to process food have followed evolutionary changes in their body mass. We discuss these findings in a physiological and ecological context.

Comparative echolocation and foraging ecology of horseshoe bats (Rhinolophidae) and Old World leaf-nosed bats (Hipposideridae)

Horseshoe (Rhinolphidae) and Old World leaf-nosed (Hipposideridae) bats are high duty cycle (HDC) echolocators sharing a suite of adaptations including long duration signals relative to their signal periods, peak energy concentrated in a narrow spectral band dominated by a constant frequency (CF) component, ‘auditory fovea’ (over-representation and sharp tuning of neurons responsible for frequencies at or around the CF) and ability to compensate for Doppler shifts in echoes. HDC bats separate signals from returning echoes in the frequency domain. Rhinolophids are more specialised neurobiologically than hipposiderids, producing longer duration signals at higher duty cycles, and have narrowly tuned auditory fovea and almost full Doppler shift compensation. Here, I examine whether these differences have produced ecological divergence between the families by testing predictions of differences in prey perception, prey capture behaviour, foraging habitat and diet. I found no discernible differences in these variables between the two families. Rhinolophids and hipposiderids both forage close to vegetation, capture prey by aerial hawking and gleaning from surfaces, and consume mostly flying insects with spiders and terrestrial, flightless arthropods taken occasionally. The data presented here show that the two families are similar in foraging ecology despite differences in echolocation and audition.