Flying bats use serial sampling to locate odour sources

Olfactory tracking generally sacrifices speed for sensitivity, but some fast-moving animals appear surprisingly efficient at foraging by smell. Here, we analysed the olfactory tracking strategies of flying bats foraging for fruit. Fruit- and nectar-feeding bats use odour cues to find food despite the sensory challenges derived from fast flight speeds and echolocation. We trained Jamaican fruit-eating bats (Artibeus jamaicensis) to locate an odour reward and reconstructed their flight paths in three-dimensional space. Results confirmed that bats relied upon olfactory cues to locate a reward. Flight paths revealed a combination of odour- and memory-guided search strategies. During 'inspection flights', bats significantly reduced flight speeds and flew within approximately 6 cm of possible targets to evaluate the presence or absence of the odour cue. This behaviour combined with echolocation explains how bats maximize foraging efficiency while compensating for trade-offs associated with olfactory detection and locomotion.

Social behaviour and vocalizations of the tent-roosting Honduran white bat

Bats are highly gregarious animals, displaying a large spectrum of social systems with different organizational structures. One important factor shaping sociality is group stability. To maintain group cohesion and stability, bats often rely on vocal communication. The Honduran white bat, Ectophylla alba, exhibits an unusual social structure compared to other tent-roosting species. This small white-furred bat lives in perennial stable mixed-sex groups. Tent construction requires several individuals and, as the only tent roosting species so far, involves both sexes. The bats´ social system and ecology render this species an interesting candidate to study social behaviour and vocal communication. In our study, we investigated the social behaviour and vocalizations of E. alba in the tent by observing two stable groups, including pups, in the wild. We documented 16 different behaviours, among others play and fur chewing, a behaviour presumably used for scent-marking. Moreover, we found 10 distinct social call types in addition to echolocation calls, and for seven call types we were able to identify the corresponding broad behavioural context. Most of the social call types were affiliative, including two types of contact calls, maternal directive calls, pup isolation calls and a call type related to the fur-chewing behaviour. In sum, this study entails an ethogram and describes the social vocalizations of a tent-roosting phyllostomid bat, providing the basis for further in-depth studies about the sociality and vocal communication in E. alba.

The complete mitochondrial genome of the Honduran white bat Ectophylla alba (Allen 1982) (Chiroptera: Phyllostomidae)

The Honduran white bat, Ectophylla alba (Allen 1982), is one of eight species belonging to the family Phyllostomidae that exclusively roosts in tents. Due to its restricted distribution, habitat specificity, and diet requirements, E. alba has been strongly affected by habitat loss and fragmentation during the last decade. In this study, we developed the first genomic resource for this species; we assembled and analyzed in detail the complete mitochondrial genome of E. alba. The mitogenome of E. alba is 16,664 bp in length and is comprised of 13 protein coding genes (PCGs), 2 ribosomal RNA genes, 22 transfer RNA genes (tRNAs), and a putative Control Region (CR) 1,232 bp in length. Gene arrangement in the mitochondrial chromosome of E. alba is identical to that reported before in other species of co-familiar bats. All PCGs are under purifying selection, with atp8 experiencing the least selective pressure. In all PCGs, codons ending with adenine are preferred over others ending in thymine and cytosine. Except tRNA-Serine 1, all tRNAs exhibit a cloverleaf secondary structure. The CR of E. alba exhibits three domains commonly described in other mammals, including bats; extended terminal associated sequences (ETAS), central, and conserved sequence block (CSB). A ML phylogenetic reconstruction of the family Phyllostomidae based on all 13 mitochondrial PCGs confirms the monophyletic status of the subfamily Sternodermatinae and indicates the close relationship between E. alba and the genus Artibeus. This is the first genomic resource developed for E. alba and represents the first step to improving our understanding of the genomic underpinnings involved in the evolution of specialization as well as acclimatization and adaptation to local and global change of specialist bats.

Socio-spatial organization reveals paternity and low kinship in the Honduran white bat (Ectophylla alba) in Costa Rica

Ectophylla alba is a tent-making bat that roosts in mixed-sex clusters comprising adults and offspring. Our goal was to determine the genetic identity of individuals belonging to different roosting groups. We tested the hypothesis of kin selection as a major force structuring group composition. We used 9 microsatellites designed for E. alba to determine the genetic identity and probability of parentage of individuals. We analyzed parentage and kinship using the software ML-Relate, GenAIEx, and Cervus. The obtained relationship probabilities (0.5) revealed a clear maternal relationship between female adults and offspring with allele compatibility, and at least 5 relationships between male adults and pups. We found a low degree of relatedness within roosting groups. Between roosting groups at different sites, the mean probability of a half-sibling relationship ranged from 0.214 to 0.244 and, for full-sibling relationship, from 0.383 to 0.553. Genetically, adult individuals were poorly related within clusters, and kinship as an evolutionary force could not explain group membership.

Nocturnal scent in a 'bird-fig': A cue to attract bats as additional dispersers?

The plant genus Ficus is a keystone resource in tropical ecoystems. One of the unique features of figs is the diversity of fruit traits, which in many cases match their various dispersers, the so-called fruit syndromes. The classic example of this is the strong phenotypic differences found between figs with bat and bird dispersers (color, size, presentation, and scent). The 'bird-fig' Ficus colubrinae represents an exception to this trend since it attracts the small frugivorous bat species Ectophylla alba at night, but during the day it attracts bird visitors. Here we investigate day to night changes in fruit scent as a possible mechanism by which this 'bird-fig' could attract bats despite its fruit traits, which should appeal solely to birds. Analyses of odor bouquets from the bat- and bird-dispersal phases (i.e. day and night) differed significantly in their composition of volatiles. We observed a significant increase in relative amounts of sesquiterpene and aromatic compounds at night while relative amounts of two compounds of the fatty acid pathway were significantly higher during day. This finding raises the question whether Ficus colubrinae, a phenotypically classic 'bird-fig', might be able to attract bat dispersers by an olfactory signal at night. Preliminary observations from feeding experiments which indicate that Ectophylla alba is capable of finding ripe figs by scent alone point in this direction. However, additional behavioral experiments on whether bats prefer the 'night-bouquet' over the 'day-bouquet' will be needed to unequivocally answer this question.