Journal of Experimental Biology and Agricultural Sciences, November - 2013; Volume – 1(5) Journal of Experimental Biology and Agricultural Sciences http://www.jebas.org ISSN No. 2320 – 8694 ASPECTS OF THE ECOLOGY OF THE TULLBERG’S SOFT-FURRED MOUSE (PRAOMYS TULLBERGI: THOMAS 1894) IN MOUNT AFADJATO, GHANA Benjamin Yeboah Ofori*, Daniel Korley Attuquayefio and Erasmus Henaku Owusu Department of Animal Biology and Conservation Science, University of Ghana, Legon, P.O. Box LG67, Legon, Accra, Ghana. Received: September 01, 2013; Revision: October 16, 2013; Accepted: November 20, 2013 Available Online November 30, 2013. KEYWORDS ABSTRACT Relative abundance The relative abundance, age-structure, sex-ratio, biomass and breeding activity of Praomys tullbergi Age structure (Tullberg’s soft-furred mouse) were studied over an eight-month period (June 2008 to January 2009) at Mount Afadjato Conservation Area in the Volta Region of Ghana. The methodology involved the use of Sex ratio live-trapping techniques using Sherman collapsible traps. There were 183 captures of 80 individual mice in 3,360 trap-nights, giving overall trapping success and relative abundance of 5.4% and 2.4%, Small mammals respectively. Adults constituted about 93% of the total number of individuals captured, while the remaining 7% were all sub-adults. Majorities (59%) of the individuals recorded were males, and these Species complex were generally slightly heavier than their non-pregnant female counterparts. Breeding activity was evident throughout the study period, peaking during the wet season. All the captured female individuals showed evidence of breeding activity (perforate vaginas, enlarged nipples, pregnancy), whereas 84% of the males had scrotal testes. The highest number of individuals was recorded in August. The year-round breeding activity of P. tullbergi may, to a large extent, account for their dominance in most forests in Ghana. * Corresponding author E-mail: [email protected] (Benjamin Yeboah Ofori) Peer review under responsibility of Journal of Experimental Biology and Agricultural Sciences. Production and Hosting by Horizon Publisher (www.my-vision.webs.com/horizon.html). All _________________________________________________________rights reserved. Journal of Experimental Biology and Agricultural Sciences http://www.jebas.org 399 Ofori et al 1 Introduction understanding of the factors contributing to their proliferation and mono-dominance. Rodents play critically important roles in forest ecosystems, and contribute to biological and functional diversity of many Effective forest management requires that potential effects of ecosystems (Nicolas et al., 2010). They influence the structure management practices on small mammals and the processes and composition of the environment through consumption and dependent upon them are considered (Pearson, 2000). distribution of foliage, seeds and fungal spores (Angelici & Knowledge of the ecology of P. tullbergi can inform Luiselli, 2005). They also serve as prey for carnivorous conservation measures aimed at increasing the diversity of mammals, birds and reptiles, particularly snakes, helping to small mammals inhabiting the West African sub-region maintain energy flow and material recycling. The composition through the promotion of coexistence of the species with other of rodent communities in many vegetation types in Ghana is forest-specialists. however poorly known despite numerous attempts to bridge this knowledge gap (Decher & Bahian, 1999; Barriere et al., The present study investigated aspects of the ecology of P. 2009; Ofori et al., 2013). The main reason for this is the tullbergi at Mount Afadjato Conservation Area in Ghana. difficulty in correctly identifying rodents due to low levels of Recent studies (Ofori, 2009) at the site recorded two small morphological differentiation among species, particularly mammal species, P. tullbergi and Crocidura olivieri, with the sibling ones (Nicolas et al., 2005). former comprising 98% of the total number of captured individuals. Mount Afadjato therefore provides a suitable Currently, the systematics and taxonomy of many genera of environment for studying the ecology of P. tullbergi. The murid rodents are shrouded in controversy (Nicolas et al., objective of the present study was to determine the relative 2010). Recent technological and analytical advances in abundance, age structure, sex ratio, biomass, breeding activity molecular genetics present an invaluable opportunity to resolve and temporal distribution of P. tullbergi at Mount Afadjato. these discrepancies. Already, some studies have succeeded in separating and providing detailed descriptions of some closely- 2 Materials and Methods related and sibling species (Nicolas et al., 2008, Nicolas et al., 2010). 2.1 Study Area Praomys tullbergi is an eight-species complex, notably P. Mount Afadjato (0o 15’- 0o 45’E; 6o 45’- 7o 15’N) (Fig. 1), at tullbergi, P. misonnei, P. morio, P. petteri, P. rostratus, P. about 900 m above sea level, is the highest mountain in Ghana hartwigi, P. obscures and P. coetzeei (recent addition from the (Owusu et al., 2006). It forms part of the Akuapim-Togo northwest Angola) (Van der Straeten, 2008). Praomys Ranges together with the Agumatsa range, and both are located tullbergi, P. misonnei, P. morio, and P. petteri occur in the in the Hohoe District of the Volta Region of Ghana. primary and secondary lowland forests of West, Central and East Africa (Nicolas et al., 2008; Nicolas et al., 2010), whereas Mount Afadjato and part of the Agumatsa range together P. rostratus, P. hartwigi, P. obscures are found in the constitute an area of about 12km2, are currently being managed mountain forests of West Cameroon (Missoup et al., 2012). collaboratively as a conservation area by the Gbledi and Praomys tullbergi and P. misonnei are believed to co-occur in Fodome-Ahor traditional authorities in Hohoe in the Volta eastern Guinea and Cote D’ ivoire (Nicolas et al., 2008), but Region of Ghana (Owusu et al., 2006). only the former has been reported in Ghana (Akpatou et al., 2007). In their study of the small mammal fauna of the Volta Region of Ghana (including the Agumatsa Range), Decher & Abedi-Lartey (2002) confirmed that all the Praomys species they captured were P. tullbergi despite apparent individual differences in size and pelage colour. Recent studies in both primary and secondary forests in Ghana have reported disproportionately high numbers of P. tulbergi (Yeboah, 1998; Decher & Bahian, 1999; Barriere et al., 2009; Garshong & Attuquayefio, 2013). This mono-dominance of P. tullbergi could have conservation implications by largely impoverishing the diversity of the country’s forest-specialist small mammals. The loss of some species and over-abundance of others could have potent negative impacts on a wide range of ecological processes, because of the diverse ecological roles played by different small mammal species in the forest ecosystem (Chung & Corlett, 2006; Nicolas et al., 2010). There Figure 1 A Topographic Map of the Mount Afadjato- is therefore a pressing need for studies of the ecology of the Agumatsa Area species in as many forests as possible to enable a better _________________________________________________________ Journal of Experimental Biology and Agricultural Sciences http://www.jebas.org Aspects of the Ecology of the Tullberg’s Soft-furred Mouse (Praomys tullbergi: Thomas 1894) in Mount Afadjato, Ghana. 400 The climate of the area is typically Dry Semi-deciduous forest, 2.4.2 Relative Abundance (Ar) with Moist Semi-deciduous Forest in a few specific areas. Rainfall is single-peak between April and October, with June, This was estimated as the total number of individuals captured September and October having a higher precipitation. Rainfall per 100 trap-nights. Thus, figures range from 1,594.8mm to 1,762.2mm (mean: 1,650mm). Prevailing winds blow north-south, and average relative humidity is 90%. Annual temperature ranges from 19oC and 29oC (Hawthorne & Abu-Juam, 1993). Vegetation follows a characteristic pattern of relief and exposure, with Dry Semi-deciduous forest occupying the western slopes, and the Where: steeper eastern side dominated by savanna and tree steppe Ar = relative abundance (Hall & Swaine, 1981; Hawthorne & Abu-Juam, 1993). A Ts = trap-success baseline survey of the area recorded over 450 plant species, Nc = total number of captures 350 butterfly species with significant degree of endemism, Ni = total number of individuals captured over 112 bird species, and 33 mammal species including bats, Tn = total number of trap-nights rodents and shrews (GWS, 2007). 2.4.3 Age 2.2 Selection of Study Sites The weight of individuals was used as an index of age. In order to obtain a representative sample of P. tullbergi at the Following Garshong & Attuquayefio (2013), individuals study area, we surveyed three different zones at the Mount weighing 30 g and more were considered adults, those Afadjato as follows: (i) Lowland Zone (LLZ), an area at the weighing between 20 g to 30 g sub-adults and those weighing foot of the mountain, (ii) Midslope Zone (MSZ), middle-level below 20 g juveniles. area between the foot and summit, and (iii) Submontane Zone (MSZ), an area just below the summit. 2.4.4 Biomass 2.3 Live-trapping of P. tullbergi The fresh biomass of each small mammal species was estimated as the mean weight (mass) of adult males and non In each zone, two permanent 100 m long transects were pregnant females to avoid biases due to overweight imposed by established to the left and right of Mount Afadjato, using a pregnancy. Total biomass was estimated as the product of the hiking trail as a reference point. Each transect was supplied mean weight and the number of adult individuals recorded. with 10 standard Sherman live-traps placed at about 10 m intervals along its length. Traps baited with a mixture corn 2.5 Statistical Analysis meal and peanut butter were set during the day and checked from 07:30 to 10:00 hours GMT the following morning. The test of variance (one-way ANOVA) was used to establish significant differences in mean weight of individuals. Traps were set for seven consecutive nights per month for eight consecutive months (June 2008 to January 2009).