Rediscovery of the critically endangered Hill's horseshoe bat (Rhinolophushilli) and other new records of bat species in Rwanda

Abstract

Background: For forty years, there has been growing uncertainty about whether Hill's horseshoe bat (Rhinolophushilli) still persists in Nyungwe National Park, Rwanda. Only known from one small area within the National Park, R.hilli is listed as Critically Endangered by the International Union for the Conservation of Nature (IUCN), based on its extremely small geographic range and presumed low number of mature individuals. Here, we present and describe bat species occurrence data contributed to the Global Biodiversity Information Facility (GBIF) that we collected as part of a long-term collaborative project to rediscover this lost species. This data paper describes the survey methods and findings resulting from cave roost surveys, capture surveys, and acoustic sampling of bat echolocation activity in Nyungwe National Park and surrounding areas in south-western Rwanda from 2013-2020 and their conservation relevance.

New information: We report the discovery of an extant population of Hill's horseshoe bat (Rhinolophushilli) in Nyungwe National Park, Rwanda, 40 years since the last reported observation of the species in 1981. We also report the first record of Lander's horseshoe bat (Rhinolophuslanderi) in Nyungwe National Park and the first record of the Damara woolly bat (Kerivoulaargentata) in Rwanda. The dataset contributed to GBIF and described in this paper includes 278 occurrence records from 10 bat species of five families detected at 71 locations in or near Nyungwe National Park, Rwanda. We include a description of the morphological descriptions of R.hilli and present the first acoustic echolocation signatures and phylogenetic information for this species.

Keywords: Afromontane rainforest; Albertine Rift; Nyungwe National Park; Rwanda.

Figure 1.

Location of survey efforts undertaken to rediscover Rhinolophushilli in Nyungwe National Park, Rwanda. A Initial reconnaissance surveys (2013-2015); B Cave reconnaissance surveys (2018); C main expedition cave and forest surveys (2019).

Figure 2.

Notable records of bat species encountered in Nyungwe National Park. A, B Rhinolophushilli, first observation of this species since 1981; C Rhinolophuslanderi, first record of this species in Nyungwe National Park; D Rhinolophusclivosus, congeneric species found in Nyungwe for comparison; E Kerivoulaargentata, first record of this species in Rwanda.

Figure 3.

Location of acoustic surveys for Rhinolophushilli conducted from July 2019 to November 2020 in Nyungwe National Park, Rwanda. Locations where R.hilli were detected and frequency in which R.hilli calls were identified (measured by number of positive triggering events/night, inset) are shown.

Figure 4.

Spectrogram of echolocation calls emitted by Rhinolophushilli (FFT size 2048, Hanning window; sampling rate of 500 kHz). Color scale represents amplitude of sound in decibels (dB). Mean peak frequency 35.4 kHz, call duration 49.5 ms, interpulse interval 82.25 ms.

Figure 5.

Sketches of noseleaf morphology of Rhinolophushilli from photographs of the two individuals captured during this study. Drawings by Fiona Reid.

Figure 6.

Bayesian phylogeny of selected indivduals from the genus Rhinolophus using an alignment of 490 base pairs of mitochondrial gene cytochrome b. Black circles at nodes represent Bayesian posterior probabilities (PP) ≥ 0.95, and grey circles represent PP < 0.95. Tip labels represent major clades and more detailed breakdown of species names for R.maclaudi group. Species used in the phylogenetic analysis, including GenBank accession numbers are outlined in Suppl. material 2.