Bats (Mammalia, Chiroptera) from Yuscarán in Eastern Honduras: Conservation and acoustic characterization for the insectivorous species

In Honduras, most bat inventories have been carried out with mist nets as the main sampling method, skewing knowledge towards the Phyllostomidae family, therefore the diversity and distribution of insectivorous bats is underrepresented. In order to have a more complete knowledge of the diversity of bats in the municipality of Yuscarán and mainly in the Yuscarán Biological Reserve, an inventory was carried out using the techniques of mist-netting and acoustic monitoring. The samplings were carried out between 910 and 1,827 m.a.s.l., covering agroecosystems, broadleaf forest, pine forest and urban environment. A total of 32 species of bats were registered, which represents 28% of the species diversity present in Honduras. Species belonging to five families were recorded: Emballonuridae (6.25%), Mormoopidae (15.22%), Phyllostomidae (56.25%), Molossidae (9.37%) and Vespertilionidae (12.5%). With the mist nets, a sampling effort of 7,128 m²/h was reached, which allowed the capture of 20 species and 186 individuals. Through the acoustic method, with 84 h/r, 13 species of insectivorous bats were recorded. The values of the acoustic parameters analysed from the search phase of each insectivorous species are provided, which can serve as a reference for the identification of species from Hondurans. To advance our understanding of the distribution patterns, composition, and vocal signatures of insectivore bats, we suggest the complementary use of mist nets and acoustic recorders in the inventories.

Cultural transmission of vocal dialect in the naked mole-rat

Naked mole-rats (Heterocephalus glaber) form some of the most cooperative groups in the animal kingdom, living in multigenerational colonies under the control of a single breeding queen. Yet how they maintain this highly organized social structure is unknown. Here we show that the most common naked mole-rat vocalization, the soft chirp, is used to transmit information about group membership, creating distinctive colony dialects. Audio playback experiments demonstrate that individuals make preferential vocal responses to home colony dialects. Pups fostered in foreign colonies in early postnatal life learn the vocal dialect of their adoptive colonies, which suggests vertical transmission and flexibility of vocal signatures. Dialect integrity is partly controlled by the queen: Dialect cohesiveness decreases with queen loss and remerges only with the ascendance of a new queen.

Individual vocal signatures show reduced complexity following invasion

The manner in which vocal learning is used for social recognition may be sensitive to the social environment. Biological invaders capable of vocal learning are useful for testing this possibility, as invasion alters population size. If vocal learning is used for individual recognition, then individual identity should be encoded in frequency modulation patterns of acoustic signals. Furthermore, frequency modulation patterns should be more complex in larger social groups, reflecting greater selection for individual distinctiveness. We compared social group sizes and used supervised machine learning and frequency contours to compare contact call structure between native range monk parakeets (Myiopsitta monachus) in Uruguay and invasive range populations in the U.S. Invasive range sites exhibited fewer nests and simpler frequency modulation patterns. Beecher’s statistic revealed reduced individual identity content and fewer possible unique individual signatures in invasive range calls. Lower estimated social densities and simpler individual signatures are consistent with relaxed selection on the complexity of calls learned for individual recognition in smaller social groups. These findings run counter to the traditional view that vocal learning is used for imitation, and suggest that vocal learning can be employed to produce individual vocal signatures in a manner sensitive to local population size.

Acoustic identification of two morphologically similar bat species, Miniopterus magnater and Miniopterus fuliginosus (Chiroptera, Miniopteridae)

Bats play important roles in ecosystems, and are thus considered bioindicators. Libraries of echolocation calls provide huge potential resources for bat species identifications, ecological studies and conservation surveys. Here, the echolocation calls of two morphologically similar bat species (Miniopterus magnater and Miniopterus fuliginosus) were recorded and described in order to characterize vocal signatures for field identification in China. Both M. magnater and M. fuliginosus emitted short frequency modulated echolocation calls with narrow bandwidths. Each call of the former species included two harmonics, with the first harmonic being the strongest, whereas calls of the latter species normally contained one harmonic. Although call durations were similar between the two species, there were significant differences in start, end and peak frequencies between M. magnater and M. fuliginous. The results showed that 92.3% of all calls recorded in China were attributed to the correct species based on spectral features of echolocation calls. We concluded that echolocation calls are valuable characters for the identification of morphologically similar bat species.