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Long-term data for endemic frog genera reveal potential conservation crisis in the Bale Mountains, Ethiopia

Published online by Cambridge University Press:  08 January 2013

David J. Gower*
Affiliation:
Department of Zoology, The Natural History Museum, London SW7 5BD, UK.
Roman K. Aberra
Affiliation:
Ethiopian Wildlife Conservation Authority, Addis Ababa, Ethiopia
Silvia Schwaller
Affiliation:
University of Basel, Institute of Biogeography, Department of Environmental Sciences, Basel, Switzerland
Malcolm J. Largen
Affiliation:
Formby, UK
Ben Collen
Affiliation:
Institute of Zoology, Zoological Society of London, London, UK
Stephen Spawls
Affiliation:
Spixworth, Norwich, UK
Michele Menegon
Affiliation:
Sezione di Zoologia dei Vertebrati, Museo Tridentino di Scienze Naturali, Trento, Italy
Breda M. Zimkus
Affiliation:
Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, USA
Rafael de Sá
Affiliation:
Department of Biology, University of Richmond, Richmond, Virginia, USA
Abebe A. Mengistu
Affiliation:
University of Basel, Institute of Biogeography, Department of Environmental Sciences, Basel, Switzerland
Fikirte Gebresenbet
Affiliation:
Department of Biology, Addis Ababa University, Addis Ababa, Ethiopia
Robin D. Moore
Affiliation:
Conservation International, Arlington, Virginia, USA
Samy A. Saber
Affiliation:
Department of Biology, Addis Ababa University, Addis Ababa, Ethiopia
Simon P. Loader
Affiliation:
University of Basel, Institute of Biogeography, Department of Environmental Sciences, Basel, Switzerland
*
(Corresponding author)E-mail d.gower@nhm.ac.uk
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Abstract

Populations of many frogs have declined alarmingly in recent years, placing nearly one third of the > 6,000 species under threat of extinction. Declines have been attributed largely to habitat loss, environmental degradation and/or infectious diseases such as chytridiomycosis. Many frogs undergo dramatic natural population fluctuations such that long-term data are required to determine population trends without undue influence of stochastic factors. We present long-term quantitative data (individuals encountered per person hour of searching) for four monotypic frog genera endemic to an Afromontane region of exceptional importance but growing conservation concern: one endemic to the Ethiopian highlands (Spinophrynoides osgoodi) and three endemic to the Bale Mountains (Altiphrynoides malcolmi, Balebreviceps hillmani, Ericabatrachus baleensis), collected during 15 field trips to the Bale Mountains between 1971 and 2009. Only a single confirmed sighting of S. osgoodi has been made since 1995. The other three species have also declined, at least locally. E. baleensis appears to have been extirpated at its type locality and at the same site B. hillmani has declined. These declines are in association with substantial habitat degradation caused by a growing human population. Chytrid fungus has been found on several frog species in Bale, although no dead or moribund frogs have been encountered. These results expose an urgent need for more amphibian surveys in the Bale Mountains. Additionally, we argue that detrimental human exploitation must be halted immediately in at least some parts of the Harenna Forest if a conservation crisis is to be averted.

Information

Type
Conservation issues in Africa and Cape Verde
Copyright
Copyright © Fauna & Flora International 2013
Figure 0

Fig. 1 Map of the Bale Mountains National Park, Ethiopia showing Park boundary, local villages and towns (squares), and sampling localities A–H (dots) referred to in the text and Table 1. The dots labelled A2 to A5 are based on coordinates given in error by Grandison (1978) and Largen (2001); these localities are actually close to the Goba–Rira road, approximately within the area marked by the ellipse labelled A2–A5. Rira, in the centre of the Park, is at 6.771°N, 39.725°E.

Figure 1

Plate 1 The four endemic Ethiopian monotypic frog genera studied: (a) Spinophrynoides osgoodi, (b) Altiphrynoides malcolmi, (c) Ericabatrachus baleensis, and (d) Balebreviceps hillmani. S. osgoodi is endemic to the highlands of Ethiopia; the others are endemic to the Bale Mountains. (a) by S. Spawls, (b–d) by M. Menegon.

Figure 2

Fig. 2 Quantitative decline of frogs in the Bale Mountains (Fig. 1), shown as generalized additive modelling trends (lines) fitted to abundance (as sightings per person hour of searching; Table 1) data for focal species of frogs: (a) Spinophrynoides osgoodi 1971–2009, (b) Altiphrynoides malcolmi 1971–2009, (c) Balebrevicpes hillmani 1986–2009, and (d) these three species plus Ericabatrachus baleensis 1971–2009.

Figure 3

Table 1 Numbers (and individuals per hour in parentheses) of the four species of frogs surveyed in the Bale Mountains across eight localities (A–H; see Methods for further details and Fig. 1) during 15 numbered field trips between 1971 and 2009.

Figure 4

Plate 2 Habitat degradation in the Harenna Forest, Bale Mountains (Fig. 1): (a) stream trampled by cattle in Erica forest at the type locality (Tulla Negesso) of Balebreviceps and Ericabatrachus, September 2006, (b) livestock trails, cut wood and lack of ground cover in Erica forest between Tulla Negesso and Fute, December 2010, (c) collection site of Balebreviceps under rotten wood forming part of old livestock fence (new bamboo fence in background) in heavily grazed clearance just below Rira, December 2010, and (d) house and bamboo fencing in man-made clearance in Erica forest, Fute, June 2009.

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