Excerpt from Peel et al (2017)

See Peel et al (2017) for full listing of locations.

Location: In mid-May 2010 (dry season), two colonies were identified in the south of the island (Figure S2.10), the first, at Adjo (where sampling occurred: 1.58971, 7.3373), north-east of M‡bana, and another nearby at VitŽ, on the path between M‡bana and Aual. The terrain precluded accurate roost or nightly emergence counts, however population sizes at Adjo and VitŽ were estimated at approximately 1000 Ð 1500 bats and 600 Ð1500 bats, respectively. A site where bats had previously been seen roosting near San Juan in the north of the island was empty
In late October/early November 2011 (wet season) six roosts were located, all of them of small size (10-80 bats). Two roosts were observed in the northwest of the island: one near Pali‡ cove (where sampling occurred: 1.4181389 S, 5.6188391 E), and another by a stream 600 m to the south of Pali‡. Another small roost was located in the San Juan valley, in the northeast of the island. One small roost was also located in the centre-west of the island, 1.5 km to the north of Aual. The roosts in the south that harboured hundreds of bats in May 2010 (VitŽ and Adjo) were occupied again but this time only a few dozen bats were present.
In mid-June 2014 (dry season), the roosts in the north of the island were vacated, with only the VitŽ and Adjo roosts being occupied. The large colony of VitŽ (1.459736 S, 5.630429 E) was sampled and its population size estimated at 1,000-1,500 bats.
The island is very small but rugged and other small colonies are likely to exist but we think the existence of undetected large colonies is less likely.
Bats can be seen flying over most of the island and they have also been observed feeding on fruiting trees (e.g. breadfruit, mangoes, bananas) in many areas of the island, including the town of PalŽ. Even at times when the roosts are concentrated in the south of the island some bats are still observed feeding on trees in the northern areas.

Reproductive seasonality: In mid-May 2010, adult females were in very early or early stages of pregnancy and no juveniles were observed in the colony. In mid-June 2014 there were some females in mid stage of pregnancy while others were still in very early to early stages. Based on a gestation period of 4 months, the birthing time was estimated as mid- September. In late October and early November 2011 several females were observed carrying neonates in flight, and one of these pairs was captured in the nets. The proportion of females carrying neonates from the total of flying bats observed appeared to decrease from late October to early November; we made three sampling counts in the north of the island on 25th October (27% of flying bats were females with neonates attached; n = 15), 8th November (5% were females with neonates attached; n = 20), and 10th November (no females carrying neonates were observed; n = 19). While simple sizes are small, this observation likely corresponds with females leaving their juvenile pups at the roost site overnight.
The birthing season seems to occur just before the onset of the wet season. There are two climatological seasons in Annob—n; the dry season from March/April to September/October and the wet season from October/November to February/March. The wet season is when most fruits ripen (e.g., mangoes ripen between October and January).

The climatological seasons and/or the reproductive stages also seem to govern the distribution of roosts in the island. Around the beginning of the birth pulse, when females are lactating, (at the start of the wet season) bats are spread in small roosts (less than 100 individuals) dispersed throughout the island (Similar to observations on S‹o TomŽ). However, in the dry season, when females are in the early stages of pregnancy, most of the bats seem to be concentrated in just two large colonies in the southern area of the island. The South, with its cloud-catching peaks is the wettest part of the island due to the southerly nature of the prevailing winds in this oceanic region. It is also the area where the fruiting season of trees extends beyond that of the northern areas (e.g. mangoes season ends in December in the north while one month later many are still ripping in the south).

Roost structure: The proportion of adults vs. sexually immatures among captured individuals was similar for May 2010 and June 2014 in the southern large roosts, with around 60% adults vs. 40 % SI. A higher proportion of adults were captured in the Pali‡ roost in October/November 2011 (86% adults vs. 14% SI). One neonate bat was also captured attached to its mother in 2011.
The proportion of males vs. females varied from 56% males and 44% females in May 2010 and October/November 2011 to 66% males vs. 34% females in June 2014.

Bat-human interactions: Domestic pigs were observed foraging under a breadfruit tree and banana plantation where E. helvum bats were observed feeding during the night. People also regularly collect fruits from and under the same trees where bats feed. Informal investigations revealed that E. helvum bats are eaten infrequently in Annob—n. Children or teenagers have been observed playfully using stones to harass bats feeding in mango trees in the town (PalŽ), and they were reported to occasionally kill bats feeding close to urban areas with slingshots for consumption. Adults reported that they would not eat bats, either because of a dislike of the taste and smell, or because of an association with witchcraft.

Isolation and differentiation: Juste et al. (2000) established that the E. helvum population on Annob—n is significantly smaller in body size than populations on the nearest islands or on continental Africa. This was supported in this study. Additionally, strong genetic differentiation (Juste et al. 2000; Peel et al. 2013) is apparent and it has been proposed that Annob—nÕs geographic isolation has resulted in sufficient genetic differentiation of E. helvum on the island for its designation as a separate subspecies, E. helvum annobonensis (Juste et al. 2000).

Refs:
Peel, A. J., J. L. N. Wood, K. S. Baker, A. C. Breed, A. de Carvalho, A. Fern‡ndez-Loras, H. S. Gabrieli, G. Gembu, V. A. Kakengi, P. M. Kaliba, R. M. Kityo, T. Lembo, F. Esono Mba, D. Ramos, I. Rodriguez-Prieto, R. Suu-Ire, A. A. Cunningham, D. T. S. Hayman 2017 How does AfricaÕs most hunted bat vary across the continent? Population traits of the straw-coloured fruit bat (Eidolon helvum) and its interactions with humans. Acta Chiropterologica 19(1)

http://www.bioone.org/doi/abs/10.3161/15081109ACC2017.19.1.006