Demography and reproductive seasonality of small terrestrial mammals in two forest ecosystems in Ghana

Abstract

We examined the effects of habitat types (farmlands, open forests and closed forests) and seasons on the population demography and reproduction of small terrestrial mammals in two tropical evergreen forests [Atewa Range Forest Reserve (ARFR) and Bimpong Forest Reserve (BFR)] environments in 2018 and 2019. Small mammals were trapped with Sherman's collapsible traps on transects across land use types and seasons to measure change in the relative density, sex ratio, age structure, juvenile recruitment and breeding probability. Twenty-two (22) species of 506 small mammals (16 rodents and six shrews) were recorded in this study. Relative density of small mammals (captures/100 trap nights) was highest (p < 0.05) in the farmland [ARFR (3.48); BFR (2.36)] than the open forest [ARFR (1.96); BFR (0.65)] and closed forest [ARFR (1.13); BFR (0.98)] habitats in both forest ecosystems. Overall sex ratio was male-skewed (1.03:1) in the study. ARFR recorded higher female ratios in all habitat types [farmland (1:1.2); open forest (1:1.04); closed forest (1:1.3)] and seasons than males. Male sex ratio was high in all habitat types and seasons in the BFR. Majority of individuals captured in the habitat types [farmland (1.5:1); open forest (1.1:1); closed forest (1.5:1)] and seasons were adults. Over 90% of all captured adults in the study areas were actively breeding. The closed forest habitat type had the highest proportion (0.93) of actively breeding small mammals in the study forests. Seasonally, there were more species actively breeding in the wet season in ARFR and dry season in BFR. Majority of the small mammal captured (n = 268 recorded for ARFR and n = 168 for BFR) were adults. Juvenile recruitment (proportion of juveniles/total capture) was low for all the study forests (with mean proportions of 0.11, 0.04 and 0.03 for closed forest, farmland and open forest, respectively, in ARFR and 0.05, 0.03 and 0.07 for closed forest, farmland and open forest, respectively, in BFR) and seasons. Anthropogenic activities degrade ecosystems, change population demography and favour habitat generalists and pest species.