Rodents of Bahir Dar Blue Nile River Millennium Park, Ethiopia

Rodents are mammals of the order Rodentia, which are found in all continents except Antarctica. They are the most diverse groups of mammals representing 41% of all mammals and they are known with 33 families, 481 genera, and about 2277 species. The present study was conducted from December 2018 to August 2019 both during the dry and wet seasons using Sherman traps and live traps. Four trap sites namely forest, bushland, grassland, and sugarcane plantation were selected for data collection. Shannon-Wiener diversity index (H') was used to compute rodent species diversity, Simpson's index (D) to assess the number and abundance of rodents in the different habitats, and one-way ANOVA and independent samples t-test were used for data analysis.

A total of 163 individual rodents were captured in 1776 trap nights of which 125 individuals were captured using live traps in 1176 trap nights and 38 individuals using snap traps in 600 trap nights. Among the total individual rodents captured in the Bahir Dar Blue Nile River Millennium Park, 63.8% (n = 104) were males and 36.2% (n = 59) were females. Males outnumbered females in all the grids and the difference was significant (t = 31.5, df = 10, p < 0.05). The relative abundance of rodent species indicated that 42.4% (n = 53) were Arvicanthis niloticus, 26.4% (n = 33) Rattus rattus, 17.6% (n = 22) Mus musculus, 8% (n = 10) Mastomys natalensis, and 5.6% (n = 7) Arvicanthis abyssinicus. There are more individual specimens of A. niloticus than other species identified in the area (F = 698.22, df = 4, p < 0.05). Distribution of rodents varied among the different habitats. As a result, the bushland habitat showed more diversity of rodents (H = 0.98) and comprised relatively the highest (51.2%, n = 64) number of individuals captured, while the forest habitat supported the lowest number of rodents (4%, n = 5), and the difference showed a significant difference (F = 873.37, df = 3, p < 0.05). Population density with 95% confident interval estimated as 166 individuals/ha (95% CI:164.43-167.57).

The present study provides basic information about population dynamics of rodents and contributes to design conservation strategies for rodents in particular and other biota of the area in general.