Social calls used by a leaf-roosting bat to signal location

Social calls in bats have many functions, including mate attraction and maintaining contact during flight. Research suggests that social calls may also be used to transfer information about roosts, but no studies have yet demonstrated that calls are used to actively attract conspecifics to roosting locations. We document the social calls used by Spix''s disc-winged bat (Thyroptera tricolor) to actively recruit group members to roosts. In acoustic trials, we recorded two sets of calls; one from flying individuals termed ‘inquiry calls’, and another from roosting bats termed ‘response calls’. Inquiry calls were emitted by flying bats immediately upon release, and quickly (i.e. 178 ms) elicited production of response calls from roosting individuals. Most flying bats entered the roost when roosting individuals responded, while few bats entered the roost in the absence of a response. We argue that information transfer concerning roost location may facilitate sociality in T. tricolor, given the ephemeral nature of roosting structures used by this species.     

Social Calls Produced within and near the Roost in Two Species of Tent-Making Bats,Dermanura watsoni and Ectophylla alba

Social animals regularly face the problem of relocating conspecifics when separated. Communication is one of the most important mechanisms facilitating group formation and cohesion. Known as contact calls, signals exchanged between conspecifics that permit group maintenance are widespread across many taxa. Foliage-roosting bats are an excellent model system for studying the evolution of contact calling, as there are opportunities to compare closely related species that exhibit major differences in ecology and behavior. Further, foliage-roosting bats rely on relatively ephemeral roosts, which leads to major challenges in maintaining group cohesion. Here, we report findings on the communication signals produced by two tent-making bats, Dermanura watsoni and Ectophylla alba. We found that both species produced calls in the early morning near the roost that were associated with roostmate recruitment. Calling often ended once other bats arrived at the tent, suggesting that calls may be involved in roostmate recruitment and group formation. The structure and function of these calls are described and future research directions are discussed.     

Social communication in bats

Bats represent one of the most diverse mammalian orders, not only in terms of species numbers, but also in their ecology and life histories. Many species are known to use ephemeral and/or unpredictable resources that require substantial investment to find and defend, and also engage in social interactions, thus requiring significant levels of social coordination. To accomplish these tasks, bats must be able to communicate; there is now substantial evidence that demonstrates the complexity of bat communication and the varied ways in which bats solve some of the problems associated with their unique life histories. However, while the study of communication in bats is rapidly growing, it still lags behind other taxa. Here we provide a comprehensive overview of communication in bats, from the reasons why they communicate to the diversity and application of different signal modalities. The most widespread form of communication is the transmission of a signaller's characteristics, such as species identity, sex, individual identity, group membership, social status and body condition, and because many species of bats can rely little on vision due to their nocturnal lifestyles, it is assumed that sound and olfaction are particularly important signalling modes. For example, research suggests that secretions from specialized glands, often in combination with urine and saliva, are responsible for species recognition in several species. These olfactory signals may also convey information about sex and colony membership. Olfaction may be used in combination with sound, particularly in species that emit constant frequency (CF) echolocation calls, to recognize conspecifics from heterospecifics, yet their simple structure and high frequency do not allow much information of individual identity to be conveyed over long distances. By contrast, social calls may encode a larger number of cues of individual identity, and their lower frequencies increase their range of detection. Social calls are also known to deter predators, repel competitors from foraging patches, attract group mates to roost sites, coordinate foraging activities, and are used during courtship. In addition to sound, visual displays such as wing flapping or hovering may be used during courtship, and swarming around roost sites may serve as a visual cue of roost location. However, visual communication in bats still remains a poorly studied signal modality. Finally, the most common form of tactile communication known in bats is social grooming, which may be used to signal reproductive condition, but also to facilitate and strengthen cooperative interactions. Overall, this review demonstrates the rapid advances made in the study of bat social communication during recent years, and also identifies topics that require further study, particularly those that may allow us to understand adaptation to rapidly changing environmental conditions.     

Roosting Ecology of the Tent‐Roosting Bat Artibeus watsoni (Chiroptera: Phyllostomidae) in Southwestern Costa Rica1

We described the plants used as roost resources by Artibeus watsoni in southwestern Costa Rica, assessed roost fidelity, and compared roosting ecology between two sites, Golfito and Corcovado, which vary in the degree of human influence. A total of 349 tents from 25 different plant species were used by A. watsoni as roosts; some plant species (e.g., Carludovica palmata, Asplundia alata, Heliconia imbricata and Calathea lutea) were modified into tents with significantly higher frequency than others. The highest tents above the ground were observed in Philodendron popenoei and Rhodospatha wendlandii, whereas tents in Philodendron grandipes and A. alata were significantly lower than any other species. Asplundia alata and R. wendlandii also had the highest frequency of leaves modified per plant. Fidelity of bats to tents was low, although bats used several tents intermittently within a restricted area. Males generally were more faithful to tents than females, although not significantly so. This observation, along with indirect evidence of leaf modification, suggests that males are primarily responsible for tent construction. The two study sites differed in the plants used for roosting and in tent fidelity. Bats in Corcovado used a greater variety of plant species for tent roosting, whereas bats in Golfito were more faithful, suggesting that roosting resources were scarcer at the latter site.     

Effect of dietary supplements of mussel and polychaetes on spawning performance of captive sole, Solea solea (Linnaeus, 1758)

Three diets were compared for the feeding of captive common sole broodstock (Solea solea) kept under ambient photoperiod and temperature conditions. A group of 70 adults were caught in the wild and the 38 males and 32 females distributed at random in six tanks. All the fish were acclimated to the same semi-moist diet (M) in the pre-experimental period from December to February. Three dietary treatments were offered in the experimental period from March to May with two replicates (tanks) per treatment. The treatments were M alone, M supplemented with fresh mussels (Mytilus edulis) (M+M), and M supplemented with live polychaetes (Perinereis cultrifera) (M+P). Spawning occurred during April and May when water temperature was 17 and 18 degrees C, respectively, and salinity around 34-35ppt. Average daily dry matter intake expressed as a proportion of body weight was M 0.65+/-0.34%, M+M 0.43+/-0.18%, and M+P 0.56+/-0.27%, and differed significantly (P<0.05) between treatments. The average daily dry matter intake within a tank ranged from 0.31+/-0.04% in February to 0.98+/-0.26% in May (P<0.05), apparently due to changes in the photo-thermal regime. Diet significantly affected the number of days when spawning occurred, the number of days when hatched eggs were produced, and the proportion of fertilized eggs (P<0.05); and affected the number of days on which viable eggs were produced during April (NS). In all cases, the results were lowest for M+M, while those for the other two treatments did not differ significantly. Differences in hatching rate were not significant in April. During May, no spawning occurred in fish given the M+M treatment, and the differences between the other two treatments were not significant. Values for all variates tended to be higher for M+P than M+M in April and lower for M+P and M in May. These results suggest that supplementing the semi-moist diet with mussels depressed feed intake and, consequently, reproductive performance; the semi-moist diet alone and semi-moist diet supplemented with polychaetes allowed satisfactory food intake and reproductive performance in broodstock sole.