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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

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  • 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
Introduction
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
savanna.
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
INVENTORY OF BAT SPECIES OF NIAOULI FOREST, BÉNIN,
AND ITS BEARING ON THE SIGNIFICANCE OF THE DAHOMEY
GAP AS A ZOOGEOGRAPHIC BARRIER
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
Page 5
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.
Results
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.
Discussion
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.
Species
Sex,
(sample size),
age
Forearm (mm)
x ± SD
(min-max)
Body mass (g)
x ± SD
(min-max)
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
BERGMANS, W., 1991 [for 1990]. Taxonomy and biogeography of
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Scotonycteris Matschie, 1894, Casinycteris Thomas, 1910,
Pteropus Brisson, 1762, and Eidolon Rafinesque, 1815.
Beaufortia 40(7): 111-176.
BERGMANS, W., 1997. Taxonomy and biogeography of African fruit
bats (Mammalia, Megachiroptera). 5. The genera Lissonycteris
Andersen, 1912, Myonycteris Matschie, 1899 and
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geographic barriers. Evolution 12(1): 48-62.
DECHER, J. and FAHR, J., 2005. Hipposideros cyclops. Mammalian
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savanna corridor between the Guinean and the Congolian rain
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classified forests, southeastern Guinea; including a review of
the distribution of bats in Guinée Forestière, in: A Rapid
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Mammals of Africa, an Identification Manual, (eds. MEESTER,
J. and SETZER, H. W.), 1-73. Smithsonian Institution,
Washington, D.C.
KÜPER, W., SOMMER, H., LOVETT, J. C., MUTKE, J., LINDER, H.
P., BEETJE, H. J., VAN ROMPAEY, R. S. A. R., CHATELAIN,
C., SOSEF, M. and BARTHLOTT, W., 2004. Africa's hotspots of
biodiversity redefined. Ann. Missouri Bot. Gard. 91(4): 525-535.
OLSON, D. M., DINERSTEIN, E., WIKRAMANAYAKE, E. D.,
BURGESS, N. D., POWELL, G. V. N., UNDERWOOD, E. C.,
D'AMICO, J. A., ITOUA, I., STRAND, H. E., MORRISON, J. C.,
LOUCKS, C. J., ALLNUTT, T. F., RICKETTS, T. H., KURA, Y.,
LAMOREUX, J. F., WETTENGEL, W. W., KURA, Y., HEDAO,
P. and KASSEM, K. R., 2001. Terrestrial ecoregions of the
world: A new map of life on Earth. BioScience 51(11): 933-938.
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Bull. Carnegie Mus. nat. Hist. 6: 168-174.
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VOGLOZIN, N. C. A., 2005. Influences des systèmes agro-forestiers
sur la diversité des communautés de chauves-souris dans la
forêt classée de la Lama. DEA-Thesis, Faculté des Sciences
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WEBER, N., 2005. Raumnutzung und Fouragierverhalten des
afrikanischen Langzungenflughundes Megaloglossus
woermanni (Chiroptera: Pteropodidae) im Lama-Wald, Bénin,
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Erlangen-Nürnberg. 84 pp.
Submitted: 30 August 2007
Accepted: 16 November 2007
Figure 3: Hipposideros cyclops (F-N° 1867) from Niaouli
Forest.
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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.
Acknowledgements
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] . ...
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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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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.
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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.
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