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Inventory of bat species of Niaouli Forest, Bénin, and its bearing on the significance of the Dahomey Gap as a zoogeographic barrier

  • Université Nationale d'Agriculture de Porto-Novo (Bénin)


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January 2008 vol. 15 African Bat Conservation News
ISSN 1812-1268
Page 4
West African forests are usually grouped into two blocks:
Upper Guinea (Guinea and Sierra Leone to Ghana; "Western
Region" according to GRUBB, 1978) and Lower Guinea
(Nigeria and eastward; "West Central Region" according to
GRUBB, 1978). The West African rainforest region is
characterized by a large number of species that are either
endemic to Upper or Lower Guinea or both of them (BAKARR
et al. 2004, KÜPER et al. 2004). The hiatus dividing both
blocks is called Dahomey Gap (Fig. 1), i.e. a stretch of
savanna reaching southward to the coast of the Gulf of
Guinea (Dahomey was the former name of Bénin). However, it
is still disputed whether this savanna-like vegetation exists
because of a climatic anomaly or due to anthropogenic land-
cover changes. DUPONT and WEINELT (1996) suggested
that it was caused by both factors. ROBBINS (1978)
considered human land use concentrated on the rich alluvial
soils between Lomé, Togo, and Lagos, Nigeria, as the main
driver of vegetation patterns (rather than climate) and
therefore a relatively recent impact. AKOEGNINOU (1998),
who investigated isolated forest stands within the savannas of
southern Bénin, assumed that the present rainfall is still
sufficient to allow the establishment of a dense semi-
evergreen forest, which would therefore represent the natural
vegetation of this region without anthropogenic influence. On
the contrary, SALZMANN and HOELZMANN (2005) reported
that the palaeorecord from Lac Sélé, situated about 60 km
northeast of Niaouli, suggests that the role of humans in
shaping the West African savannas has been overestimated.
Nowadays, this area is largely dominated by farms, fallows
and grasslands intermingled with small fragments of semi-
deciduous forest (ADOMOU, 2005). BOOTH (1958) also
indicated that at certain periods the Dahomey Gap had been
much wider than at present.
BOOTH (1954, 1958) considered the savanna vegetation
of the Dahomey Gap to be an important faunal barrier for
forest-dependent species, leading over evolutionary time to
endemic taxa on both sides of the Dahomey Gap. This view
was challenged by ROBBINS (1978), who demonstrated that
several forest-dependent mammal species can be found in
forest patches within the Dahomey Gap. In the course of
ongoing bat inventories throughout Bénin (BIOTA-project), we
sampled one of these areas falling within the gap, the Niaouli
Forest, to assess the composition of forest- vs. savanna-
dependent bat species and to evaluate the importance of
these forest fragments as stepping-stones connecting
populations on both sides of the Dahomey Gap.
Material and Methods
Niaouli Forest (6°44’N, 2°08’E) is located about 50 km
north of Cotonou and covers ca. 220 ha. Nowadays, only 65.5
ha of remnant dense forest remains that represent relatively
undisturbed forest. Part of this forest is classified as “forêt du
bas fond” and comprises 24.2 ha, which is intersected by the
Ava River (Fig. 2). The majority of this forest type is
permanently flooded. A second portion (41.3 ha) is located on
a plateau (“forêt du plateau”), which is surrounded by
We sampled bats in Niaouli Forest for 3 nights (5th, 6th and
7th of August) in 2003 with 2 mist nets (26 mist net-hours) and
1 night (1st of Jun) in 2007 with 5 mist nets (32.5 mist net-
hours). Mist nets employed measured 12 x 2.8 m (16 mm
mesh; 2 x 70 d netting), with 5 shelves. Nets were erected
between poles near ground level or slightly elevated above
the surrounding vegetation (herb layer). Mist nets were open
By: Bruno A. Djossa1,2; Brice A. Sinsin1; Elisabeth K.V. Kalko2,3 and Jakob Fahr2
1 Laboratoire d’Ecologie Appliquée-FSA/UAC/Bénin. 2 Institute of Experimental Ecology, University of
Ulm, Germany. 3Smithsonian Tropical Research Institute, Balboa, Panama
Figure 1: Potential extent of the forest biome in West Africa (OLSON et al. 2001), showing the Dahomey Gap (encircled), which
separates Upper and Lower Guinea. The point indicates the location of Niaouli Forest.
January 2008 vol. 15 African Bat Conservation News
ISSN 1812-1268
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between 19:15 and 20:00 until 00:00 hrs during the first half of
the night and re-opened in the early morning from 4:00 to 6:30
hrs. Sites were selected in both “forêt du plateau” and “forêt
du bas fond”. Species were identified with keys of HAYMAN
and HILL (1971) and BERGMANS (2002) as well as the
reference collection recently established at the University of
Abomey-Calavi. To identify Epomops spp., we mainly relied
on forearm length, body mass, and the pattern of the third
palatal ridge to distinguish between E. buettikoferi (Matschie,
1899) and E. franqueti (Tomes, 1860). Two specimens of
Hypsignathus montrosus H. Allen, 1862 (1 , field number [F-
N°] 1850; 1 , F-N° 11b) and one specimen of Hipposideros
cyclops (Temminck, 1855) (, F-N° 1867) were collected and
deposited in the reference collection at the University of
Abomey-Calavi, all other bats were released.
We captured 55 bats in total (34 in 2003 and 21 in 2007)
comprising six species (Table 1). Records of Hypsignathus
monstrosus and Megaloglossus woermanni Pagenstecher,
1885 constitute the first published records for Bénin. Based on
their general distribution patterns, habitat preferences of
species recorded during the present survey can be
characterized as follows. Epomophorus gambianus (Ogilby,
1835) is a savanna species that invades the forest zone
where rainforest has been converted to farmbush
(BERGMANS, 1988; FAHR and EBIGBO, 2003). In West
Africa, Epomops franqueti is mostly confined to rainforest
(BERGMANS, 1989). Hypsignathus monstrosus is mainly
found in the forest zone, but extends into savannas along
gallery forests and forest islands (BERGMANS, 1989; FAHR
et al. 2006). Megaloglossus woermanni is mostly confined to
rainforest (BERGMANS, 1997; FAHR and EBIGBO, 2003).
Eidolon helvum is a migratory species, which, depending on
season, is found both in rainforest and savanna habitats
(BERGMANS, 1991). Hipposideros cyclops (Fig. 3) is mostly
found in the rainforest zone but extends into the forest-
savanna mosaic along gallery forests and forest islands
(DECHER and FAHR, 2005). Overall, four species (H.
monstrosus, E. franqueti, M. woermanni and H. cyclops) or
67% of the species total are those that are mainly found within
the forest zone.
Epomops, Hypsignathus and Megaloglossus were listed by
BOOTH (1954) as genera occurring in rainforest east and
west of the Dahomey Gap, and BERGMANS (1997) mapped
the Dahomey Gap as a barrier for Hypsignathus and
Megaloglossus. These conclusions are not supported by our
data as they were found to occur within the Dahomey Gap.
Figure 2: Two different views of the flooded part (“forêt du bas
fond”) of Niaouli Forest and Ava River.
(sample size),
Forearm (mm)
x ± SD
Body mass (g)
x ± SD
Epomophorus gambianus ♂♂ (n =3) 88.3±1.2 (87.0-89.2) 117.3±16.4 (105-136)
♀♀ (n =10) 81.6±3.5 (75.2-86.0) 83.4±9.3 (74-103)
Epomops franqueti ♂♂ (n =3) 89.7±3.4 (86.8-93.5) 111.0±9.6 (100-118)
♀♀ (n = 4) 80.3±3.5 (75.2-82.7) 83.5±11.3 (73-99)
Hypsignathus monstrosus (n =1)
subadult 109.7 161
♀♀ (n= 2) 111.1 (110.5-111.7) 212.5 (201-224)
Megaloglossus woermanni ♂♂ (n = 9) 40.5±0.8 (38.6-41.5) 13.0±0.7 (12-14)
♀♀ (n= 4) 40.2±0.6 (39.7-41.0) 12.8±1.5 (11-14)
Eidolon helvum ♂♂ (n =3) 116.8±1.4 (116.0-118.5) 218.0±14.1 (205-233)
(n =1)
subadult 100.7 107
Hipposideros cyclops (n =1) 68.2 34
Table 1: Bat species recorded during this study from Niaouli Forest, southern Bénin. Measurements include only adult specimens
(n=39) except for two subadult specimens as indicated.
BEKKER and EKOUÉ (2004), who also reported
Epomophorus gambianus from Niaouli Forest, additionally
found Nanonycteris veldkampii (Jentink, 1888) (a migratory
species occurring in both forest and savanna habitats) as well
as Hipposideros caffer (Sundevall, 1846) (a species found
both in forest and savanna habitats). Both E. franqueti and H.
cyclops were previously recorded from Kpodave (ROBBINS,
1980), which is located about 40 km west of Niaouli. Epomops
franqueti, M. woermanni and H. cyclops were also captured in
Lama Forest (VOGLOZIN, 2005; WEBER, 2005), another
fragment situated about 25 km north of Niaouli. These
different collections from several forest remnants within the
Dahomey Gap confirm the presence of forest-dependent bat
species in the Dahomey Gap as already reported by
January 2008 vol. 15 African Bat Conservation News
ISSN 1812-1268
Page 6
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Submitted: 30 August 2007
Accepted: 16 November 2007
Figure 3: Hipposideros cyclops (F-N° 1867) from Niaouli
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ROBBINS (1978). We therefore agree with ROBBINS (1978)
that the presence of forest-dependent mammals within the
Dahomey Gap necessitates a re-evaluation of its importance
as a zoogeographic barrier, and in particular for mobile
mammals like bats.
We appreciate funding by the German Ministry of Education and
Science through the BIOLOG-program (BMBF; project W09 BIOTA-
West, 01 LC 0411). We thank the authorities of Niaouli Forest for
granting the permit to conduct this survey.
... 2010; Kunz et al., 2011;N'zuki et al., 2011;Kadjo, 2015) [3,4,1,5,2] . Fruit bats or Megachiroptera play a key role in the maintenance and regeneration of forests after natural or anthropogenic disturbances Djossa et al., 2008Djossa et al., , 2010Kunz et al., 2011) [6,7,8,1] . Unfortunately, they are rarely taken into account in the management of protected areas and in biological inventories of these environments (Bakwo et al., 2014) [9] . ...
... On the other hand, the sites surveyed to study them remain limited and are mainly protected areas. These include the Lamto Reserve in the preforest savannah zone (Bergmans et al., 1974;Thomas, 1983) [11,12] , the Taï National Park (Gordon, 2001;Henry et al., 2004;Koné, 1996) [15,16,17] and Azagny (Nesi et al., 2013) [18] in the evergreen forest zone, the Comoé and Mont Sangbé National Parks in the Sudanian savannah zone (Fahr and Ebigbo, 2003) [12] , the Mont Nimba Integrated Reserve in the mountain forest zone (Brosset, 1985;Denys et al., 2013;Monadjem et al., 2013Monadjem et al., , 2016Simmons et al., 2021) [18,19,20,21,22] and the breeding colonies of the African straw bats (Eidolon helvum) in the Plateau-Abidjan commune (Niamien et al., 2010(Niamien et al., , 2015(Niamien et al., , 2017 [5,13,23] . Studies carried out in the Taï and Comoé National Parks and those from other sources estimate the species richness of chiropterans in Côte d'Ivoire to be between 42 and 87 species in these richest massifs in Côte d'Ivoire (Brosset, 1985;Fahr and Kalko, 2010;Kadjo, 2015) [18,24,2] . ...
... Les activités qui y sont menées, surtout celles qui procurent des revenus aux ménages telles que les exploitations d'espèces végétales à des fins commerciales sans oublier les activités de pêche sont autant de pressions qui mettent à mal la conservation desdites ressources. Cette situation a besoin d'être considérée avec attention pour éviter de perdre totalement ces écosystèmes précieux et rares dans cette partie du pays couverte par le « Dahomey Gap » qui, on le sais, est pauvre en écosystèmes forestiers (Grubb, 1978 ;Bakarr et al., 2004 ;Küper et al., 2004 ;Djossa et al., 2008 ;Adomou et al., 2009). La création de parcs nationaux dans cette partie méridionale du pays ou tout au moins des réserves de faunes serait donc un moyen efficace pour soustraire ces écosystèmes aux pressions anthropiques sévères qui finiront par les faire disparaître. ...
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Résumé Les analyses des données démographiques de l’INSAE, complétées par les prospections et les enquêtes de terrain ont permis d’analyser la pression anthropique qui pèse sur les sites à ériger en réserves de faune dans la partie méridionale du Bénin. Des investigations ont été faites sur des sites échantillons comme les marécages de Sèmè-Djèrègbé (Sèmè-kpodji) et de Yovocodji (Kpomassè), la forêt marécageuse de Lokoli (Zogbodomey), la forêt marécageuse de Gnanhouizounmè (Bonou), l’estuaire maritime de la bouche du Roy (Grand-Popo) et le Lac Doukon et ses corridors dans la vallée du fleuve Mono. Il ressort de ces analyses que l’aire d’étude bien qu’elle présente une diversité faunique non négligeable, elle est fortement anthropisée et si rien n’est fait pour arrêter ce processus de dégradation, les chances de création de réserves sera compromise. Mots clés : Réserves de faune, milieux humides, pression anthropique, Sud-Bénin. Analysis of the effect of anthropogenic pressure on the biodiversity of sites that will be ranked as fauna reserve in the Southern Benin Abstract The recent population census coupled with the field investigations allowed to analyse the anthropogenic pressure on the sites dedicated to be raised to fauna reserve level in the in the southern Benin. Investigations were conducted on selected sites like the marshlands of Sèmè-Djèrègbé (Sèmè-kpodji District) and Yovocodji (Kpomassè District), the swampy forest of Lokoli (Zogbodomey District), the marshy forest of Gnanhouizounmè (Bonou District), the maritime estuary named “Bouche du Roy” (Grand-Popo District) and the Lake Doukon in the Mono valley. It comes out from these surveys that although the study area hosts a meaningful fauna diversity, if nothing is done to alleviate the anthropogenic pressure the chance to conserve these habitats will be vanished. Key words: Fauna Reserves, marshlands, anthropogenic pressure, Southern Benin.
... This savannah corridor represented a dispersal barrier for many forest-dwelling species [70,72,73], but mammalian and bird species inhabiting savannahs and more arid regions have also shown high genetic differentiation between north/west and south/east African populations747576. Bats are hypothesized to be able to cross the Dahomey Gap [64,77,78]; but establishing populations within the gap would be unlikely for forest-dwelling species with small ranges [64,79]. Moreover, the Niger Delta or the Cameroon volcanic line have also been hypothesised to act as environmental barriers for some pteropodid populations from West and Central Africa [64]. ...
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The Vespertilionidae is the largest family of bats, characterized by high occurrence of morphologically convergent groups, which impedes the study of their evolutionary history. The situation is even more complicated in the tropics, where certain regions remain under-sampled. Two hundred and thirteen vespertilionid bats from Senegal (West Africa) were studied with the use of non-differentially stained karyotypes and multi-locus sequence data analysed with maximum likelihood and Bayesian methods. These bats were identified as 10 different taxa, five of which were distinctive from their nominate species (Pipistrellus hesperidus, Nycticeinops schlieffenii, Scotoecus hirundo, Neoromicia nana and N. somalica), based on both karyotypes and molecular data. These five cryptic taxa are unrelated, suggesting that these West African populations have long been isolated from other African regions. Additionally, we phylogenetically analysed 166 vespertilionid taxa from localities worldwide using GenBank data (some 80% of the genera of the family) and 14 representatives of closely related groups, together with our Senegalese specimens. The systematic position of several taxa differed from previous studies and the tribes Pipistrellini and Vespertilionini were redefined. The African Pipistrellus rueppellii was basal to the Pipistrellus/Nyctalus clade and the Oriental species Glischropus tylopus was basal to the East Asian pipistrelles within the tribe Pipistrellini. The African genus Neoromicia was confirmed to be diphyletic. Based on GenBank data, Eptesicus was polyphyletic, with the Asian E. nasutus and E. dimissus both supported as phylogenetically distinct from the Eptesicus clade. The subfamily Scotophilinae was confirmed as one of the basal branches of Vespertilionidae. New taxa and new systematic arrangements show that there is still much to resolve in the vespertilionids and that West Africa is a biogeographic hotspot with more diversity to be discovered.
... azagnyi. In addition, it has been demonstrated that Megaloglossus populations occur in remaining patches of forest present in the Dahomey Gap (Djossa et al., 2008). The phylogenetic relationships of these populations with Me. woermanni and Me. ...
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The tribe Myonycterini comprises five fruit bat species of the family Pteropodidae, which are endemic to tropical Africa. Previous studies have produced conflicting results about their interspecific relationships. Here, we performed a comparative phylogeographic analysis based on 148 complete cytochrome b gene sequences from the three species distributed in West Africa and Central Africa (Myonycteris torquata, Lissonycteris angolensis and Megaloglossus woermanni). In addition, we investigated phylogenetic relationships within the tribe Myonycterini, using a matrix including 29 terminal taxa and 7235 nucleotide characters, corresponding to an alignment of two mitochondrial genes and seven nuclear introns. Our phylogenetic analyses confirmed that the genus Megaloglossus belongs to the tribe Myonycterini. Further, the genus Rousettus is paraphyletic, with R. lanosus, sometimes placed in the subgenus Stenonycteris, being the sister-group of the tribes Myonycterini and Epomophorini. Our phylogeographic results showed that populations of Myonycteris torquata and Megaloglossus woermanni from the Upper Guinea Forest are highly divergent from those of the Congo Basin Forest. Based on our molecular data, we recommended several taxonomic changes. First, Stenonycteris should be recognized as a separate genus from Rousettus and composed of S. lanosus. This genus should be elevated to a new tribe, Stenonycterini, within the subfamily Epomophorinae. This result shows that the evolution of lingual echolocation was more complicated than previously accepted. Second, the genus Lissonycteris is synonymised with Myonycteris. Third, the populations from West Africa formerly included in Myonycteris torquata and Megaloglossus woermanni are now placed in two distinct species, respectively, Myonycteris leptodon and Megaloglossus azagnyi sp. nov. Our molecular dating estimates show that the three phases of taxonomic diversification detected within the tribe Myonycterini can be related to three distinct decreases in tree cover vegetation, at 6.5-6, 2.7-2.5, and 1.8-1.6Ma. Our results suggest that the high nucleotide distance between Ebolavirus Côte d'Ivoire and Ebolavirus Zaire can be correlated with the Plio/Pleistocene divergence between their putative reservoir host species, i.e., Myonycteris leptodon and Myonycteris torquata, respectively.
... The occurrence of M. woermanni in this region is thus noteworthy as this species is otherwise distributed throughout the forest zone of tropical West and Central Africa. In Benin, it is only known from one additional locality about 25 km to the southwest, the Niaouli Forest (Djossa et al., 2008). ...
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We investigated spatial use and foraging behaviour of the nectarivorous African long-tongued bat, Megaloglossus woermanni (Chiroptera: Pteropodidae), in the Lama Forest Reserve, southern Benin, West Africa. We monitored movement and activity patterns of two males and two females that were fitted with position-sensitive radio transmitters for five to nine nights within a three-month study period. The study site comprised the central patch of relatively undisturbed forest (‘Noyau Central’), and a mosaic of orchards, agroforestry plantations, and degraded forests surrounding the central patch. Spatial use of M. woermanni was characterized by small home ranges and high site-fidelity. Mean home range sizes (minimum convex polygon) were larger in females (139.0 and 146.8 ha) than in males (99.8 and 102.9 ha). Throughout the study period, long-tongued bats were frequently observed visiting flowers of cultivated bananas. The mean foraging areas (95% density kernel) of females (39.0 and 109.4 ha) were much larger than in males (12.3 and 14.1 ha). Difference in core areas (50% density kernel) between the sexes was less marked (both females: 6.8 ha, males: 2.7 and 2.9 hectares). Core areas constituted only a small part of home ranges (2.64.9%). Large segments of the home ranges were only used for commuting flights between discrete resource patches. Our study provides, for the first time, information on home ranges and foraging behaviour of the sole obligate nectar-drinking bat in Africa.
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L’élevage des petits ruminants est une activité culturelle pratiquée par la grande majorité (90 %) de la population béninoise. C’est un élevage familial avec un effectif moyen de 2 à 10 têtes. Hormis les fonctions de prestige et d'épargne, ces animaux interviennent pour augmenter le revenu des éleveurs àtravers d'une part, la vente des animaux et de leurs sous-produits (peau, lait) et d'autre part à travers l'utilisation du fumier pour la fertilisation des exploitations agricoles. Au Bénin, les races locales sont inféodées à l’écosystème du milieu. Les ovins et les caprins sont les espèces représentatives des petits ruminants. Dans les deux espèces, les animaux (moutons et chèvres) appartiennent pour la plupart à la race guinéenne ou Djallonké originaire du Fouta-Djallon dispersés à travers tout le pays. La race Djallonké constitue la plus importante partie du cheptel des petits ruminants Béninois, avec une prédominance des caprins dans la zone sud alors que les ovins prédominent dans la zone nord. Le taux de croît du cheptel est estimé sur une période 35 ans (1960-1994) à 3% pour les ovins et 4,5% pour les caprins. Cependant on enregistre d’autres races telles que les ovins sahéliens (mouton Peul), les chèvres mossi et des chèvres bariolées et rousses de Maradi le long du fleuve Niger (Karimama et Malanville). Les modes d’élevage sont variés et tiennent compte de la variété des zones agroécologiques, des comportements ethniques et sociaux et du niveau technique des éleveurs. Le faible niveau de connaissance des principales races élevées dans notre pays et la non organisation des acteurs de la filière et leur faible niveau de professionnel s’ajoutent aux contraintes. La principale menace de distribution contre les espèces d’élevages est l’érosion génétique. Certaines races locales réputées pour leur résistance ou leur résilience (trypanosomes, parasitoses, …) font aujourd’hui objet de croisement anarchique dans une vision étriquée d’amélioration de format. Sur le plan sanitaire l’absence de spécialistes en santé animale près des éleveurs, la cherté des produits vétérinaires, la non valorisation de la tradithérapie vétérinaire augmentent le taux de mortalité des animaux. L’amélioration des procédés de vaccination et la valorisation de quelques recettes endogènes pour le traitement des maladies (traitement de la diarrhée, la gale etc..) est en cours et des enquêtes menées sur l’utilisation des produits pharmaceutiques et traditionnels dans le traitement des maladies des petits ruminants ont révélé que la phytothérapie vétérinaire est riche au Bénin.
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A key problem for conservation is the coincidence of regions of high biodiversity with regions of high human impact. Twenty-five of the most threatened centers of plant diversity were identified by Myers et al., and these “hotspots” play a crucial role in international conservation strategies. The primary goal of the hotspots is to cover the most threatened centers of plant diversity, but their efficacy has not yet been tested empirically. For sub-Saharan Africa, our study evaluates the hotspots postulated by Myers and compares them to a set of redefined hotspots proposed on the basis of mapped distribution data for 5985 plant species. The two sets of hotspots overlap by 48%. Our redefined hotspots include 80% of the species and 66% of the range-restricted species of the sub-Saharan flora in areas under high humanimpact, whereas these values are 15% and 11% lower for Myers’s hotspots. Despite having equal size and a considerable spatial overlap with Myers’s hotspots, our redefined hotspots include further highly threatened centers of plant diversity in the Maputaland Pondoland Region, in Katanga, the East African Afromontane region, the Lower Guinea Region, and the Albertine Rift. Many of these redefined hotspots are poorly protected centers of plant and animal diversity. Their conservation is essential for a comprehensive coverage of Africa’s centers of biodiversity.
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We report on the results of a bat survey of the Pic de Fon, Simandou Range, southeastern Guinea. This bat survey was part of a larger Rapid Assessment Program (RAP) study conducted by Conservation International in an area currently explored for iron-ore mining by an international company. We document a speciose bat assemblage characterised by forest species, including bats such as Epomops buettikoferi, Rhinolophus guineensis and Hipposideros jonesi that are endemic to Upper Guinea or West Africa. The sympatric occurence of three species of Kerivoula is noteworthy, with K. phalaena representing the first record for Guinea. Moreover, three individuals of Welwitsch's Mouse-eared bat, Myotis welwitschii, were captured during the survey. This is the first record for West Africa and represents a range extension of minimally 3400 km to the northwest from the nearest known localities. We review the distribution of this species in Africa and conclude that the species shows a paramontane distribution pattern (sensu Koopman, 1983). We also report M. welwitschii for the first time from Burundi. Our results of the RAP survey as well as the occurrence of bat species that are endemic to the Upper Guinea Highlands highlight the outstanding regional importance of the montane habitats of West Africa in general, and of the Simandou Range in particular for the conservation of bats in Africa.
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The Dahomey Gap, a savanna corridor interrupting the zonal West African rain forest, did not exist during the mid-Holocene. The pollen diagram from Lac Sélé (7°9'N, 2°26'E) indicates that in southern Benin a semi-evergreen rainforest prevailed between c. 8400 and 4500 cal. yr BP. The mid-Holocene marine transgression caused a spread of mangrove forest along the inland lagoons. Pollen analysis and geochemistry indicate that the Dahomey Gap became established at the onset of the late Holocene due to an abrupt climatic change between c. 4500 and 3400 cal. yr BP. Drier climatic conditions led to a rapid deterioration of the rain forest and subsequent spread of Sudano-Guinean savannas. A return to wetter climatic conditions between c. 3300 and 1100 cal. yr BP resulted in a rise in the lake level and a renewed spread of forests into the savanna. During this time the Dahomey Gap consisted of a forest-savanna mosaic with a high number of pioneer tree taxa including the oil palm Elaeis guineensis After c. 1100 cal. yr BP the lake level dropped again and the Lac Sélé profile indicates drier environmental conditions resulting in the establishment of an open savanna which persists until present. The palaeorecord from Lac Sélé suggests that the role of humans in shaping the West African savannas has been overestimated. The opening of the Dahomey Gap and spread of the oil palm E. guineensis can now be confidentially attributed to climatic change and was not initiated by humans.
1. The distribution of species-groups of Primates, Sciuromorpha, Artiodactyla and Hyracoidea in West African High Forest is given in detail. 2. Four types of distribution are recognized: a) ambisilvan, groups which occur both east of the Niger and west of the Volta. b) central, groups which occur only east of the Niger. c) occidental, groups which occur only west of the Volta. d) interfluvial, groups which occur between the Niger and the Volta, and which may have their origin from groups of type a), b) or c). 3. The central fauna is much richer than the occidental, which, though it contains a small number of endemic groups, is nevertheless thought to have been derived originally from the former. 4. The interfluvial fauna is remarkably poor. The zoogeographic data tend to corroborate geological evidence for the periodic deterioration of the climate between the Niger and the Volta during the Quaternary, which probably deprived the area of its High Forest several times, either partially or completely. 5. Climatic fluctuation has resulted in the Dahomey Gap acting as an important isolating mechanism in the past. Today, it is probably less important than the Volta and Niger rivers.
Pollen and spores from a deep-sea core located west of the Niger Delta record an uninterrupted area of lowland rain forest in West Africa from Guinea to Cameroon during the last Interglacial and the early Holocene. During other periods of the last 150 ka, a savanna corridor between the western — Guinean — and the eastern — Congolian — part of the African lowland rain forest existed. This so-called Dahomey Gap had its largest extension during Glacial Stages 6, 4, 3, and 2. Reduced surface salinity in the eastern Gulf of Guinea as recorded by dinoflagellate cysts indicates sufficient precipitation for extensive forest growth during Stages 5 and 1. The large modern extension of dry forest and savanna in West Africa cannot be solely explained by climatic factors. Mangrove expansion in and west of the Niger Delta was largest during the phases of sea-level rise of Stages 5 and 1. During Stages 6, 4, 3, and 2, shelf areas were exposed and the area of the mangrove swamps was minimal.
Taxonomy and biogeography of African fruit bats (Mammalia, Megachiroptera). 1. General introduction; material and methods; results: The genus Epomophorus Bennet, 1836
BERGMANS, W., 1988. Taxonomy and biogeography of African fruit bats (Mammalia, Megachiroptera). 1. General introduction; material and methods; results: The genus Epomophorus Bennet, 1836. Beaufortia 38(5): 75-146.
Small mammals of Togo and Bénin. I. Chiroptera
ROBBINS, C. B., 1980. Small mammals of Togo and Bénin. I. Chiroptera. Mammalia 44(1): 83-88.
The Dahomey gap-a reevaluation of its significance as a faunal barrier to West African forest mammals
ROBBINS, C. B., 1978. The Dahomey gap-a reevaluation of its significance as a faunal barrier to West African forest mammals. Bull. Carnegie Mus. nat. Hist. 6: 168-174.
Taxonomy and biogeography of African fruit bats (Mammalia, Megachiroptera). 2. The genera Micropteropus Matschie, 1899, Epomops Gray
BERGMANS, W., 1989. Taxonomy and biogeography of African fruit bats (Mammalia, Megachiroptera). 2. The genera Micropteropus Matschie, 1899, Epomops Gray, 1870, Hypsignathus H. Allen, 1861, Nanonycteris Matschie, 1899, and Plerotes Andersen, 1910. Beaufortia 39(4): 89-153.