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ОглавлениеEidolon helvum (Kerr 1792)
African straw-coloured fruit bat Near Threatened
Description: Eidolon helvum is a very large fruit bat with a mass of around 170 g, making it the second-largest fruit bat on mainland Africa after Hypsignathus monstrosus. The pelage is typically pale yellow-brown to orange-brown with paler underparts. A distinct orange collar is present in most individuals that extends from the sides of the neck to the throat. The wings are dark brown and contrast strikingly with the pale underparts. There are no shoulder epaulettes and the ears do not have a patch of white fur at their base. The muzzle is dog-like and rather short and broad. A short tail is present.
The skull is massive with moderate zygomatic arches. The cranium is distinctly arched with the rostrum tapering rapidly anteriorly from orbit and the posterior braincase strongly deflected downwards. The auditory meatus opens into a long neck (Rosevear 1965). The sagittal crest is low, but usually clearly visible. The lambdoid crest is fairly well developed. The palatal ridges have been illustrated by Happold (1987). The dental formula is 2132/2133 = 34 with the first upper premolar reduced in size, but larger than the incisors.
Key identification features: The combination of large size (FA > 105 mm) and lack of white ear patches separates Eidolon from all other African fruit bats. Its pale colouring with contrasting dark wings distinguishes it from very large specimens of Rousettus (which can marginally overlap in size with juvenile E. helvum). Hypsignathus monstrosus is similar in size, but has white patches of fur at the base of the ears and a cylindrical muzzle.
Echolocation call: This bat does not echolocate.
Distribution, habitat and roosting: Eidolon helvum occurs widely in the region as a non-breeding migrant. There are numerous individual records from the central plateaus of South Africa and Namibia. The species has also been widely recorded in Zimbabwe, Zambia, southern DRC and Malawi. There are scattered records from western Angola. The type specimen is from Senegal.
This species is relatively well represented in museums, with more than 100 specimens examined for this book.
Little is known about its roosting behaviour across the region. Two large colonies have been described from southern Africa: a probable breeding colony at Marromeu, Mozambique, that supports hundreds of bats (Cotterill 2001c), and a massive colony at Kasanka National Park, Zambia. The latter is the best studied population of this species. This site sees an influx of 1.5 million non-breeding bats between November and January (Sorensen and Halberg 2001), with significant local impacts on the ecology of the landscape (Byng et al. 2010). Based on four bats from the Kasanka colony radio-tracked using satellite telemetry, large-scale feeding and migratory movements were documented (Richter and Cumming 2008). Bats foraged at distances of up to 59 km from their roost. One migrating bat moved 370 km in one night, and one individual travelled a cumulative 2,518 km in 149 days. This Kasanka population depends critically on a functional network of roosting and foraging sites, and intact fruit-producing woodlands, throughout Zambia and the DRC.
The diet of E. helvum, when resident in Kasanka, includes the fruits of savanna trees – Parinari curatellifolia, three species of Syzygium, and four species of Uapaca (Richter and Cumming 2006). They also forage on the flowers of Isoberlinia angolensis; this species of Fabaceae occurs widely across the mesic miombo woodlands, and its phenology is unusual as it flowers in mid-summer, which suggests a co-evolutionary relationship with pteropid bats (F. Willems, Ecologist, Kasanka National Park, personal communication December 2014). Eidolon helvum has come under intense pressure from humans, who hunt it for food across tropical Africa, as well as recent persecution related to its perceived role in the transmission of diseases, especially Ebola (Peel et al. 2013, 2017, Hayman and Peel 2016, Hayman et al. 2012).
| External and cranial measurements (mm) and mass (g) for Eidolon helvum, males and females presented separately | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean | Min | Max | SD | N | Mean | Min | Max | SD | N | ||
| Males | Females | ||||||||||
| Mass 1 | 196.4 | 140.5 | 252.5 | - | 2 | Mass 1 | 158.2 | 117.0 | 196.0 | - | 3 |
| FA 1 | 112.5 | 103.6 | 130.0 | 8.75 | 9 | FA 1 | 119.3 | 110.7 | 135.0 | 10.28 | 5 |
| Total 1 | 197.0 | 140 | 240 | 40.80 | 6 | Total 1 | 215.0 | 160 | 270 | 43.1 | 5 |
| Tail 1 | 17.0 | 9 | 20 | 4.20 | 6 | Tail 1 | 18.0 | 12 | 22 | 4.40 | 5 |
| Tibia | - | - | - | - | - | Tibia | - | - | - | - | - |
| Ear 1 | 22.0 | 10 | 29 | 8.50 | 4 | Ear 1 | 26.0 | 23 | 28 | 2.20 | 5 |
| CI 1 | 50.8 | 45.8 | 55.1 | 3.91 | 8 | ci 1 | 50.2 | 46.0 | 53.0 | 3.08 | 8 |
1 Specimens measured by the authors
Figure 47. Skull and teeth of Eidolon helvum: (a) dorsal view, (b) ventral view, (c) lateral view, and (d) lateral view of mandible (SMM 6848).
Extralimital: Eidolon helvum is widespread in sub-Saharan Africa, occurring from Senegal in the west to Kenya in the east, south into southern Africa and north to the Sahel (DeFrees and Wilson 1988, Bergmans 1990).
Foraging ecology: Eidolon helvum has broad wings with high wing loading (30.6 N.m-2) and low aspect ratio (6.9) (Norberg and Rayner 1987). There is no information on the diet or foraging behaviour of this species in southern Africa, but elsewhere it feeds on the following fruits (both wild and cultivated) and on some flowers (Fujita and Tuttle 1991): Anacardium occidentale, Mangifera indica, Pseudospondias spp., Spondias mombin, Annona spp., Kigelia aethiopica, K. pinnata, Adansonia digitata, Bombax buonopozense, Ceiba pentandra, Ochroma pyramidale, Carica papaya, Musanga cecropioides, Parinari excelsa, Terminalia spp., Bridelia ferruginea, Sapium ellipticum, Persea americana, Albizia spp., Erythrina spp., Parkia clappertoniana, P. filicoidea, P. roxburghii, Antiaris africana, Artocarpus spp., Chlorophora spp., C. excelsa, Ficus exasperata, F. leprieurii, F. mucosa, F. natalensis, F. thonningii, F. umbellata, F. vogelii, Musa sapientum, M. paradisiaca, Pycnanthus angolensis, Eucalyptus spp., Psidium guajava, Syzygium spp., Borassus aethiopum, Elaeis spp., Phoenix dactylifera, Adenia cissampeloides, Passiflora spp., Maesopsis spp., Eriobotrya spp., Vitellaria paradoxa, Solanum anomalum, Cola spp., Theobroma cacao, and Celtis spp. Richter and Cumming (2006, 2008) suggest that the annual migration to Kasanka is driven by seasonal variations in food supply.
Reproduction: At present, only a single probable breeding colony is known from southern Africa at Marromeu, central Mozambique. However, the collection of females, both full-term and those carrying neonates, from Chiniziwa, central Mozambique, and Mutare in eastern Zimbabwe, confirm that this species breeds in southern Africa. Several hundred bats are present at the Marromeu colony throughout the year, including sexually active adults and subadults, suggesting that breeding is taking place (Cotterill 2001c). Breeding in Uganda occurs in April–June; the bats then migrate away until August and September when they start returning; births are recorded in December–February (Kingdon 1974).
Figure 48. Eidolon helvum: (a) portrait showing orange collar, (b) group of roosting adults showing dark wings and face contrasting with orange-brown body (Maputo), and (c) a remarkable spectacle in tropical Africa – the crepuscular emergence of several million straw-coloured fruit bats at their roost, Kasanka National Park, Zambia (a: © Merlin D. Tuttle, Bat Conservation International, www.batcon.org; b: © Ara Monadjem; c: © F. P. D. Cotterill).
SYSTEMATIC NOTES
1792.Vespertilio vampyrum helvus Kerr, Linnaeus’s Animal Kingdom 1(1): xvii, 91. Senegal.
Only the nominate subspecies occurs in Africa; E. h. sabaeum K. Andersen 1912 occurs in Arabia.
The diploid number in E. helvum is 2n = 34 (Matthey 1962).
1 Specimens measured by the authors
