Estimates of home range sizes of Arvicanthis niloticus Desmarest, 1822 (Muridae) in savannah fields near Kano, Nigeria
Determination of rodent home range (HR) is invaluable for characterizing population distribution and strategies for accessing food, mate and nest sites, as well as, dispersal into new fields. The present study, in savannah fallow fields near Kano, Nigeria, was aimed at estimating HR sizes of Arvicanthis niloticus, a species widespread in much of Africa. By Capture-Mark-Recapture (CMR) in a five to six-day/month sessions on replicate grids during 1990-1992; and 25 years later followed by a one year, quarterly, appraisal surveillance during 2015-2016, the movement patterns of A. niloticus were analyzed by means of Minimum Convex Polygon (MCP) calculations. With GLM ANOVA, comparisons between sexes, seasons and periods of study were made. Further HR comparisons were made with Kruskal-Wallis tests. Predictors (year of study, sex of the rodent and season) which contributed to significant differences in HR sizes were also identified with stepwise regression. Overall, ANOVA results showed that sex had significant effect (p<0.05) on HR, larger (1,036 m2) mean HR sizes than that of females (850 m2). Seasonal differences were also significant (p<0.05). Kruskal-Wallis tests also indicated significant (p<0.05) differences between sexes, seasons and age groups, being higher in males than females; greater in dry than in rainy season; but marginally greater in adults than juveniles (p=0.056). Generally, HR size values for 2015-2016, the second segment of the study, had shown similar patterns as those of the 1990s, again with significant (p<0.05) differences between sexes, seasons, and between sexes within seasons. However, overall HR values in 2015-2016 were lower than those of 1990-1992 composite year. From the forgoing, we may conclude that though long-term temporal lapse and ensuing environmental degradation may reduce HR sizes in A. niloticus, the general patterns of age-sex and seasonally related differences do not change.
Keywords: Africa; grassfields; home range; Nile rat; movement; rodents.