The biota of the tropical montane forest is very diverse and varied in endemic species (Gentry, 1995; Kessler and Kluge, 2008). These ecosystems are also amongst the most threatened globally (Hamilton et al., 1994; Doumenge et al., 1995), with the estimated rate of deforestation nearly double the rate of average global deforestation rates in the past few decades (Hamilton et al., 2012). Threats emanate from human activities such as the uphill expansion of shifting cultivation and the exploitation of natural resources. In Africa, the situation is further exacerbated by extreme poverty that drives the immigration of subsistence farmers into the montane forest from adjacent lowland areas (Körner and Ohsawa, 2006; Mugagga et al., 2012). Indeed, tropical moist forests are estimated to have reduced by half of their original distribution in the last two decades due to agricultural activities (Myers, 1991; Gibbs et al., 2010). Given the accentuating nature of these threats, tropical forests are a conservation priority globally (Edwards et al., 2019).

The Afrotropical Highlands biome of Cameroon that encompasses the highlands of western Cameroon contain large forested areas that harbor unique ecological and biological diversity across many taxa (Myers et al., 2000; Olson et al., 2001; Oates et al., 2004). The biome covers the western highlands of southwestern Cameroon and extends northeast to the Obudu and Mambilla Plateaus in Eastern Nigeria. The unique diversity and endemism in this biome are thought to be a result of the area being a major refugium during the Quaternary glaciation (Stuart, 1986; Lawson, 1993; Stattersfield et al., 1998; Myers et al., 2000). This rich diversity has also been attributed to the region’s wide variety of habitats resulting from its extensive highlands (Cronin et al., 2014). Indeed the montane forests of the Cameroon Highlands are considered a priority area for conservation globally (Myers et al., 2000), this results from the area’s high biodiversity and endemism (Maisels et al., 2001; Oates et al., 2004; Linder and Oates, 2011; Abernathy et al., 2013; Cronin et al., 2014). However, despite such important features, very few parts of the highland’s habitats are currently under formal protection status in Cameroon, which poses a challenge to its conservation (Bergl et al., 2007). Moreover, except for Mount Cameroon, these montane forests have been significantly degraded by human activities (Collar and Stuart, 1988; Gartlan, 1989; Alpert, 1993; Megevand et al., 2013), and most often comprise only forest fragments within montane grasslands grazed by cattle of the Fulani herdsmen (Ineich et al., 2015).

One way to mitigate the adverse effects of human activities in an ecosystem is the establishment of protected areas (Geldmann et al., 2013). Protected areas harbor higher species diversity than unprotected areas (Laurance et al., 2012; Geldmann et al., 2013; Gray et al., 2016), resulting from the reduction in human-induced land-use changes such as poaching, wildfires, and deforestation (Geldmann et al., 2013; Barber et al., 2014; Gray et al., 2016). Indeed, Razgour et al. (2020) pointed out that anthropogenic land-use changes are associated with a severe decline in the population of some Afromontane bat species. Unfortunately, most of the biodiversity hotspot of the Afromontane biome of Cameroon is devoid of any legal protection. Consequently, decades of intensive anthropization have reduced formerly continuous montane forests to isolated fragments, cultivated landscapes, grassland, human settlements, and industrial plantations.

Bats play an important role in tropical forest succession after disturbance. Frugivorous and nectarivorous bat species can explore a wide range of resources, providing several ecological services such as pollination, seed dispersal, and forest regeneration (Stevens et al., 2004; Willig et al., 2007). Additionally, insectivorous bats are important suppressors of agricultural pest insects (Kalka et al., 2008; Jones et al., 2009). In addition, because of their high species richness, abundance, and variety of functional guilds bats are considered as a good bioindicator taxon used to study various human-induced alterations of ecosystems, such as forest fragmentation and degradation (Jones et al., 2009; Meyer et al., 2010). Furthermore, sensitivity to habitat fragmentation can be attributed mainly to species-specific mobility-related traits (Law et al., 1999; Farneda et al., 2015; Moir et al., 2021).

Previous records of bats in the Cameroon Highlands were mostly in the form of pioneer faunistic expeditions and collection of specimens (Eisentraut, 1942, 1956, 1963, 1964, 1968, 1973; Hill, 1968; Fedden and MacLeod, 1986). Recently, surveys by Mongombe et al. (2019, 2020), Manfothang et al. (2020, 2021) added some recent information about bats of the Cameroon Highlands. However, none of these studies evaluated the effect of anthropogenic activities on bat diversity in the biome.

Several studies in a variety of biomes and taxa have revealed that the number of species that inhabit remnant patches of forest decreases significantly as habitat patch size decreases (Debinski and Holt, 2000; Devictor et al., 2008). Habitat fragmentation, because of agricultural activities is known to alter bat assemblages (Walsh and Harris, 1996; Cleary et al., 2016). However, the response of bat communities to fragmentation can be positive or negative depending on whether the bat species is a specialist or a generalist. Some generalists can better persist in anthropogenically altered environments due to the ability to exploit additional resources such as man-made habitats (secondary vegetation and cultivated farms) and food resources (Coleman and Barclay, 2012). On the other hand, habitat fragmentation can reduce bat species richness and abundance by reducing roosts and the availability of resources (Schulze et al., 2000). Even though the montane forest of the Cameroon Highlands continues to diminish because of significant human pressure, our knowledge on changes in bat communities induced by anthropogenic activities and how human activities affect bat diversity in the area is still limited. This data is imperative to predict the long-term consequences of fragmentation on the montane forest biodiversity and to mitigate any effects. Therefore, there is a need to collect such scientific information in the area before the opportunities diminish completely due to the ever-accelerating deforestation in the region. Determining the species that either become extinct or can persist in disturbed areas is crucial to developing conservation management strategies.

Herein, our main goal was to analyze bat communities in two areas of the Afromontane forest biome of Cameroon (undisturbed area and disturbed areas) to assess bat response to habitat degradation. Our objective was to compare species richness and abundance between these two habitat types. Studies that compare bat communities in pristine forests and human-disturbed forests in similar life zones can provide insight into the original bat communities of an area and the effect that deforestation and fragmentation have on bat communities. Such studies are important to determine the extent of human influence in the spatial and temporal variations of biodiversity in an ecosystem. This information can also throw more light on the habitat preferences of some bat species and hence understand the potential risk of local extinction and community homogenization (Henle et al., 2004; Myers et al., 2015). Furthermore, comparing bat communities across different habitats can enable researchers to assess the health of an ecosystem given that bats are suitable indicator species that show sensitivity to human induce disturbances (Medellín et al., 2002; Jones et al., 2009; Meyer et al., 2016). We expect species richness, relative abundance, and the number of forest specialist species to be higher in undisturbed areas than in disturbed areas.

In this study, we surveyed bats in pristine and disturbed vegetations of the Afromontane biome of western Cameroon. Our study revealed that the disturbed forest supported larger populations and more species than the undisturbed forest sites, although the species richness did not differ significantly between the two forest types. There was a significant change in bat composition from mostly widespread generalists in the disturbed forest, to forest species in the undisturbed forest. This difference in species richness and abundance could likely be explained by greater habitat heterogeneity of the disturbed forests (Estrada and Coates-Estrada, 2002; Ramos Pereira et al., 2009). Indeed, the disturbed forests were more heterogeneous comprising of areas with secondary forest patches, gallery forests, coffee plantations, palm plantations, orchards, and cultivated farmlands. On the other hand, the undisturbed forest was characterized by primary growth with large trees, continuous canopy, dense understory, and a patchier understory cover at the ecotone montane forest/montane grassland. Both forest types were located in a volcanic landscape with numerous extinct volcanic vents that probably provided day roosts for obligate cave roosters (Glover and Altringham, 2008).

Habitat structural heterogeneity is associated with an increase in bat species activity and species occurrence (Jung et al., 2012). The heterogeneous landscape offered more resource opportunities for open-adapted species in these modified habitats, due to their ability to access extra resources such as artificial shelters and food resources (Loeb et al., 2009; Coleman and Barclay, 2012). Indeed, bats are specially adapted to access a wide diversity of habitats, occupying many ecosystems (Schnitzler and Kalko, 2001). An alternative explanation is the presence of more open water bodies in the disturbed areas which provided drinking and foraging sites for bats (Grindal et al., 1999; Campbell, 2009), leading to increased bat activity and their subsequent capture in mist-nets. The species accumulation curves did not show a tendency toward plateauing, suggesting that our surveys did not capture all species present in the study area. However, 75.84% of the estimated species richness was sampled, indicating that more species will be recorded with a greater sampling effort.

Our findings concur with other studies that demonstrated the positive effects of human disturbances on species richness and abundance of species adapted to forage in open areas, but that fragmentation negatively affects bat species that depend on pristine habitats (Klingbeil and Willig, 2009; Estrada-Villegas et al., 2010). Greater species richness and abundance in the disturbed forest can also be attributed to the greater amount of forest edge in the disturbed habitats. According to Fried et al. (2005), edge habitats contain more flying insects, hence attracting more foraging insectivorous bats, and subsequently allowing some to be captured in mist-nets. Hence a possible consequence of the continuous deforestation and fragmentation will be the replacement of forest-interior species by more adaptable and opportunistic forest edge frugivorous bats such as Eidolon helvum, Micropteropus pusillus, Myonycteris angolensis, and edge tolerant insectivorous bats such as Glauconycteris argentata (Webala et al., 2019). Understory frugivorous bats such as Scotonycteris zenkeri and Megaloglossus woermanni are also sensitive to fragmentation, and thus will be negatively impacted by deforestation than larger canopy foragers (Cosson et al., 1999). On the other hand, our findings contrast, some studies in the Neotropics by Gorresen and Willig (2004) in Paraguay, which concluded that bat community diversity was highest in relatively undisturbed forests, and findings by Estrada and Coastes-Estrada (2001) which concluded that bats within the continuous forest and forest fragments in Mexico had similar species richness.

Guild structure differs between the two forest habitat types, probably indicating the uneven distribution of resources. According to Hodgkison et al. (2004), the abundance of bats is influenced by the temporal and spatial variation of food resources, which then influence the number of species within a particular habitat (Duchamp et al., 2007; Pinto and Keitt, 2008). While the number of frugivorous bats did not differ significantly between the habitat types, there was a higher proportion of frugivorous bat species in the disturbed habitat than in the undisturbed habitat. This can probably be explained by the presence of many forest tree species such as Ficus spp., Prunus africana, Annona senegalensis, Borassus aethiopum, Hymenocardia acida, Nauclea diderrichii, Musanga cecropioides, and Caloncoba welwitschii, among species of fruiting trees planted by humans such as Persea americana, Carica papaya, Anonidium mannii, and Dacryodes edulis. The presence of more closed-spaced forager insectivorous bat species in the undisturbed habitat can probably be attributed to the nature of their echolocation calls. These species use low-intensity, high-frequency echolocation calls, characterized by low wing loadings, appropriate for foraging and commuting in cluttered habitats close to vegetation (Law et al., 2011). Therefore, the increase in anthropogenic disturbances can significantly reduce the resource availability for these species (Threlfall et al., 2012). This is consistent with findings by Webala et al. (2019) who captured more closed-space insectivorous bat species in the less-disturbed forest interior with little human disturbance in a Kenyan forest. In addition, the capture of more edge-space insectivorous bat species in the disturbed forest can be attributed to their flexible commuting traits, which enabled them to adapt to cleared environments, including agricultural areas and residential spaces. Thus, these open-adapted species are relatively insensitive to human modification, and in many cases, can exploit man-made structures (Kirsten and Klomp, 1998; Threlfall et al., 2012). Indeed, the fact that some close-space forager insectivorous bat species persist in human-dominated environments is an indication of the versatility and adaptability of some bat species.

In our surveys family, Pteropodidae represented the largest number of captures. This pattern can be attributed both to the high abundance of pteropodid bats in the surveyed area and the use of ground-level mist-netting method, which tends to be more effective at capturing low-foraging frugivorous bats (Meyer et al., 2011). Moreover, it is well documented that fast-flying insectivorous bat species that forage higher at the middle-story and canopy levels, above the height of mist-nets, and adept at detecting and avoiding mist-net due to their very efficient echolocation calls are undersampled in ground-level mist-net surveys, resulting in underestimates of the actual species richness and abundance (Kalko and Handley, 2001; Kalko et al., 2008). This probably explains the absence of molossids, emballonurids, nycterids, and the capture of only a few vespertilionids during our surveys. It is, therefore, imperative to employ different sampling methods such as sub-canopy and canopy nets, acoustic detectors, and harp traps to complement ground-level mist nets for the detection of species that are considered rare or difficult to capture (Kunz and Parsons, 2009; Estrada-Villegas et al., 2010; Fahr and Kalko, 2010) and to obtain more complete inventories of bats (Bergallo et al., 2003; MacSwiney et al., 2008; Furey et al., 2009; Meyer et al., 2011; Silva and Bernard, 2017).

While the majority of bat species were captured in only one habitat type, some species were captured in both the pristine and disturbed habitats, e.g., Megaloglossus woermanni, Myonycteris angolensis, Rousettus aegyptiacus, Rhinolophus landeri, Macronycteris gigas, Miniopterus sp., Afronycteris nana, and Pipistrellus nanulus. The fact that these species were captured in both habitat types suggested that they are probably generalist species that can tolerate and forage in modified habitats. These species can therefore access additional resources outside of remnant forest patches, such as artificial shelters and food resources (Gehrt and Chelsvig, 2003; Duchamp and Swihart, 2008; Loeb et al., 2009; Coleman and Barclay, 2012).

Megaloglossus woermanni was mostly recorded in the undisturbed (primary) forest during our surveys. However, a single individual was recorded over a stream at a high elevation site on Mt. Manengouba. This nectarivorous bat is common in closed forests but may enter cultivated areas adjacent to the forest to feed on flowers. It is common in areas where flowers persist throughout the year. This species has also been recorded in disturbed areas in the Center Region of Cameroon (Waghiiwimbom et al., 2019), as well as in relatively undisturbed forest in the Mpem and Djim National Park by Atagana et al. (2018) and in the Dja biosphere reserve by Bakwo Fils (2009). The fact that this species has been recorded in both habitat types is an indication that it might benefit when natural areas are converted to agricultural landscapes. For example, Weber et al. (2009) captured this species, while it fed on flowers of cultivated bananas around a forested area in Benin.

Rousettus aegyptiacus and Myonycteris angolensis are large cavernicolous frugivorous bat species that were recorded in both pristine and disturbed habitats. The distribution of these species is largely dependent on the availability of suitable caves as day roost (Weber and Fahr, 2006; Monadjem et al., 2010). These species are known to have a broad habitat tolerance and probably have generalist-feeding habits. The capture of these species at disturbed habitats suggests that they are relatively tolerant to habitat fragmentation and may take advantage of the seasonal fluctuation in fruit production by fruiting trees such fig (Ficus sp.), apricot (Prunus sp.), peach (Prunus sp.), mango (Mangifera indica) mostly present in disturbed areas. These species have also been recorded in disturbed areas in Cameroon (Mongombe et al., 2019; Waghiiwimbom et al., 2019; Manfothang et al., 2020, 2021), and undisturbed areas (Bakwo Fils, 2009; Atagana et al., 2018).

The presence of Macronycteris gigas in undisturbed forest patches is not that surprising given that this species forages around the edges of clutter, where it often intercepts large flying insects from a foraging perch (Vaughan, 1977). Monadjem et al. (2016) also recorded this species in forested and disturbed habitats in the Guinean Mount Nimba. The presence of Rhinolophus landeri, Afronycteris nana, and Pipistrellus nanulus in both habitat types was not that surprising because these species are associated with primary and secondary forest habitats (Monadjem et al., 2010).

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding authors.

The animal study was reviewed and approved by the Cameroon Ministry of Scientific Research and Innovation permit (Ref: 0000011/MINRESI/B00/C00/C10/C14).

E-MB and BB designed the study. MM, DM, AG-D, and JT conducted the fieldwork. MM and E-MB analyzed the data and wrote the manuscript. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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