Vocalization Analyses of Nocturnal Arboreal Mammals of the Taita Hills, Kenya

Hanna Rosti,Henry Pihlström,Simon Bearder,Petri Pellikka,Jouko Rikkinen

doi:10.3390/d12120473

Hanna Rosti, Henry Pihlström + Show 3 more

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https://doi.org/10.3390/d12120473

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Abstract

Three poorly known nocturnal mammal species from the montane forests of the Taita Hills in Kenya, were studied via vocalization analysis. Here, their acoustic behaviour is described. The studied animals were the tree hyrax (Dendrohyrax sp.), the small-eared greater galago (Otolemur garnettii), and the dwarf galago (Paragalago sp.). High-quality loud calls were analysed using RAVEN PRO, and compared to calls of presumed closest relatives. Our findings include the first detailed descriptions of tree hyrax songs. Moreover, our results suggest that the tree hyrax of Taita Hills may be a taxon new to science, as it produces a characteristic call, the ‘strangled thwack’, not previously known from other Dendrohyrax populations. Our data confirms that the small-eared greater galago subspecies living in the Taita Hills is Otolemur garnettii lasiotis. The loud calls of the elusive Taita Hills dwarf galago closely resemble those of the Kenya coast dwarf galago (Paragalago cocos). Thus, the population in the Taita Hills probably belongs to this species. The Taita Hills dwarf galagos are geographically isolated from other dwarf galago populations, and live in montane cloud forest, which is an unusual habitat for P. cocos. Intriguingly, two dwarf galago subpopulations living in separate forest patches in the Taita Hills, Ngangao and Mbololo, have clearly different contact calls. The Paragalagos in Mbololo Forest may represent a population of P. cocos with a derived call repertoire, or, alternatively, they may actually be mountain dwarf galagos (P. orinus). Hence, differences in habitat, behaviour, and contact call structure suggest that there may be two different Paragalago species in the montane forests of the Taita Hills.

Highlights

In the arboreal environment, visual signals are often difficult to perceive through the dense vegetation
This study focuses on the vocalizations of three poorly known, nocturnal, arboreal mammals in the moist montane forests of the Taita Hills, Kenya
The results provide insights into identifying and monitoring these animals, and are taxonomic tools that can be used to compare the Taita Hills animals with animals from other populations

Summary

Introduction

Visual signals are often difficult to perceive through the dense vegetation. This has led to the evolution of intraspecific vocal communication systems in many arboreal animals [1]. Prosimian primates [2,3,4] and tree hyraxes [5] rely extensively on acoustic communication, and have complex vocal repertoires. Paterson’s ‘recognition species concept’ predicts the importance of shared. Loud calls that are used in long-range advertising are qualitatively different between species [8]. Many recently described galago species have been originally identified by their advertisement calls [9,10,11,12,13]. In contrast to advertisement calls, alarm calls are conserved, phylogenetically homologous, and predicted to be less variable than those influenced by sexual selection, making them more useful as grouping criteria [15,16]

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