Discussion
During the current study period, a total of 10 species were identified. This result is comparable to the report of Kabeta et al ., (2019) from Wabe fragmented forest, Atnafu & Yihune (2018) from communal forest of northern Ethiopia and Geleta & Bekele (2016) from Wacha protected forest in the western Ethiopia. But, the mammalian species diversity recorded in the current study area is very low compared to other protection areas found across the country (Meseret and Solomon, 2014; Gonfa et al ., 2015; Negari et al ., 2015). The low mammalian species diversity of the present study area might be associated with a limited survey period, variation in the size of the study areas, and severe habitat loss and fragmentation by various anthropogenic pressures.
Vervet monkey (Chlorocebus aethiops ) and guereza (Colobus guereza ) were the most abundant mammals identified in the current study area. Similar result was also reported by several studies conducted in different parts of Ethiopia (Gonfa et al ., 2015; Geleta and Bekele, 2016). This high abundance of these primates may be also associated with the wide distributional range of the species (Boboet al ., 2014) and their more adaptive nature to different habitats (Gonfa et al ., 2015). In addition, this is may be due to the high reproductive successes, diversified foraging behavior and high tolerance level of primates to human disturbances (Bobo et al ., 2014).
The overall difference in abundance of medium and large mammal species among three habitats was not statistically significant. But, natural forest harbored more mammalian records (424), followed by Open grassland (114) and the least was in Human plantation (15). The possible reason for this distribution and diversity of medium and large-sized mammal species might be due to the presence of food and water and stability of the area from disturbances. Several mammalian studies, revealed that there is a tendency of mammals to favor one habitat over the other following the change in the abundance and quality of resources (Yimer and Yirga, 2013; Atnafu and Yihune, 2015; Gonfa et al ., 2015; Negeri et al ., 2015; Geleta and Bekele, 2016). Similar studies conducted in different part of the world showed that mammalian distribution and their habitat association correlated mainly with better availability of water, foraging opportunity and protection (Mekonnenet al ., 2011; Yaba et al ., 2011). For instance, in the current study, Vervet monkey (C. aethiopis ) was mostly seen at the edge of the forest closer to the river forests and at the center of the natural forest. Similar result is reported by Meseret & Solomon, (2014). The presence of this species at the edge of the riverine forest might be associated with a system of feeding on crops from shorter distance and easier sheltering when back off. According to the finding of Fetene et al ., (2011) and Geleta & Bekele, (2016) guereza (C. guereza) largely selected riverine and large trees, but was totally absent in the scrublands. Particularly, they dwelled the top canopy ofJuniperus, Podocarpus (the dominant tree) and Bamboo tree of natural forest. This could be probably due to relatively surplus fruits and leaves and better protection provided by those tall tree species. According to Gonfa et al ., (2015), this is riverine habitats and large trees are inaccessible to humans. In addition, since, the forest habitat is relatively less disturbed, it might have also contributed a refuge for the shy behavior of Guereza.
The low diversity and abundance of mammals in human plantation area suggests that mammals prefer relatively less human disturbed areas. This might be due to the small proportion of sampling, and the dominance of homogenous plant species, Eucalyptus species that provide low foraging and protection opportunity for large mammals (Gonfa et al ., 2015; Negeri et al ., 2015; Geleta and Bekele, 2016). According to Matias et al ., (2011), there is positive correlation between habitat heterogeneity and animal species diversity. Furthermore, habitat homogeneity was reported for lower diversity (Mekonnen et al ., 2011).
Though, Yotyet/Yewezera community forest is given to Atrifo Kidus Giorgis church to be conserved, it is not free from the anthropogenic activities pressure. Human activities such as illegal logging of trees for fuel wood, extraction of construction materials, grazing by livestock, human encroachment, were recorded during Field observations. These human activities may alter this natural environment. Anthropogenic activities affect the interactions, distribution and diversity of species through habitat loss and modifications (Torres et al ., 2016). Deforestation and habitat loss threaten mammals by decreasing area, connectivity, and fragment size, and increasing edge effects and number of fragments of the natural landscapes (Bernardo and Melo, 2013). Livestock were also seen in certain part of the habitats competing for food with mammalian species particularly. Other studies (Gonfa et al ., 2015; Kabeta et al ., 2019) also report the adverse effects of livestock on wildlife. If these threats continue, there might be no more chance to see the present floras and faunas of the study area. Recently, numerous anthropogenic factors have promoted habitat loss and fragmentation, and the decline and losses of global mammalian biodiversity (Bernardo and Melo, 2013; Geleta and Bekele, 2016). Change in vegetation community structure due to human activities could be altering the availability and quality of food, shelter and water. This might be lead to alter the diversity, abundance and distribution of population of a particular habitats or it may lead to additional problems such as risk of predation or cost of migration for searching food (Mengesha et al ., 2011). Habitat disturbance has also a negative impact for forest specialist species as they do not have any alternative foraging or breeding sites (Asefa et al ., 2017). According to Asefa et al ., (2015) allowing large and repetitive livestock population in to unprotected area will also lead to los of grassland specialist species.