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

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.

Habitat preferences, estimated abundance and behavior of tree hyrax (Dendrohyrax sp.) in fragmented montane forests of Taita Hills, Kenya

“…We repeatedly observed tree hyraxes feeding and resting close to calling animals, and completely ignoring them. 75% of calling sequences in Taita Hills are countercalls between 2 and 6 animals, typically 4 12 . Some animals from the group are counter calling, while others keep feeding or resting.…”

“…1 ). Across Africa, four species, western tree hyrax D. dorsalis , eastern tree hyrax D. validus , southern tree hyrax D. arboreus , and Benin tree hyrax D. interfluvialis , are currently recognized; however, additional undescribed species probably await scientific discovery 8 – 12 . Previously the Taita Hills tree hyraxes were supposed to represent eastern tree hyrax D. validus 13 .…”

“…However, the Taita Hills tree hyraxes differ from typical D. validus in many respects. For example, their vocalizations include distinctive songs, and their most frequently used call is the unique and earsplitting “strangled thwack” 12 . Rosti et al 12 suggested that the Taita Hills hyraxes may belong to a previously unrecognized taxon and here, we provisionally refer to these animals as “ Dendrohyrax sp.”.…”

“…Tree hyraxes are thought to be mainly solitary animals that maintain social relationships by calling and scent-marking signals 16 . They are highly vocal and calling seems to be their primary means of communication 10 , 12 , 13 , 23 . Tree hyraxes in Taita Hills also sing 12 in a similar manner as rock hyraxes 24 – 26 .…”

“…They are highly vocal and calling seems to be their primary means of communication 10 , 12 , 13 , 23 . Tree hyraxes in Taita Hills also sing 12 in a similar manner as rock hyraxes 24 – 26 . They call most actively immediately after dusk and before dawn 23 and urinate and defecate from particular places up in the trees 10 , 16 .…”