Fitness of the pestiferous small rodent Mastomys natalensis in an agroecosystem in Mayuge district, Lake Victoria Crescent, Uganda

Abstract

A 2.5-year study was conducted to understand the fitness of Mastomys natalensis in an agroecosystem in relationship with environmental predictors. The study was conducted in Mayuge district, in the Lake Victoria Crescent zone in Eastern Uganda. Fitness was measured in terms of survival, maturation and capture probability and estimated using multi-event capture-recapture models. Survival rates were higher after high rainfall in the previous month and increased with increasing population density of the animals. Maturation rate, on the other hand, showed no significant association with any predictor variables, while capture probability was significantly associated with sex of the animals, with higher capture probability for males. The results demonstrate that the fitness of M. natalensis in an agroecosystem is dependent on rainfall, sex and current population density. The aforementioned results were associated with increasing vegetation which provides cover for animal nesting and abundant food for the animals during rainfall periods and thus increased survival, high mobility in males in search for mates thus exposing animals to high chances of being captured and increased prey saturation at high population density resulting in high animal survival. These results have important implications for the timing of management strategies, i.e. control efforts should be enforced during the rainfall seasons to prevent high population buildup in the succeeding seasons.

Effects of forest disturbance on the fitness of an endemic rodent in a biodiversity hotspot

“…The finding of the current study is consistent with Mayamba et al. (2019) who reported that habitat did not affect maturation of M. natalensis in Uganda; the animals had continuous access to food resources and in no way was their normal growth and development impeded. Another best supported model showed maturation rate of females to be lower compared with males which may be due to response to pre‐ or postnatal stress or secretion of puberty‐delaying pheromones in females (Oli & Dobson, 1999).…”

“…Survival and maturation probabilities were modeled in subsequent steps which reduced the amount of models that we needed to run. We first modeled survival after which we modeled maturation (Mariën et al., 2018; Mayamba et al., 2019; Sluydts et al., 2007). Models were ranked using the sample size corrected Akaike's information criterion (AIC; Burnham & Anderson, 2004), where the model with the lowest AIC value was the best fit for the data and selected as starting point for the next modeling step.…”

“…However, survival and maturation may vary between the wet and dry seasons, sexes, and age classes, as has been found in other small mammals (Eccard et al., 2002; Oli & Dobson, 1999; Previtali et al., 2010). Most research on the effects of habitat disturbance on the population dynamics in African small mammals focused on the pestiferous Mastomys natalensis (Julliard et al., 1999; Mayamba et al., 2019; Sluydts et al., 2007), and little information is available on P. delectorum . Our study will be the first to look at the effect of anthropogenic disturbance on both the population size and two demographic parameters of P. delectorum and is therefore important to fill this knowledge gap and will be useful to optimize the current conservation and management strategies of P. delectorum (Eberhardt, 1985; Oli & Dobson, 1999; Paradis et al., 1993).…”

Breeding and demographic aspects of Montemys delectorum, an East African endemic rodent

“…Therefore, a higher number of reproductive individuals and juveniles following the long rainy season in our study are likely associated with vegetation availability driven by rainfall. Generally, the proximate factor leading to the onset of reproduction is access to growing vegetation, which is similar to what many studies have found for other rodent species (Mayamba et al, 2019;Meheretu et al, 2015;Mulungu et al, 2013). On the other way, the lower proportion of reproductively active females and newborns in the dense forest sites may be attributed to the lower availability of food and ground cover due to forest canopy, which allowed animals to migrate in search of food and or left them exposed to direct and indirect effects of predation.…”

“…Furthermore, altitude and mosaic landscape type (swamp, near the river, position to sunlight) are known to influence rodent population size (Richard et al, 2022), but their relative contributions and effects may vary among species. Most studies on African rodent demographic aspects have focused on pest species (Mayamba et al, 2019; Meheretu et al, 2015; Mulungu et al, 2013), while ecology studies on non‐pest montane species, including M. delectorum , are scarce. The aim of the study was therefore to determine the breeding patterns and demographic aspects of M. delectorum which are vital factors in understanding the conservation status of a species (IUCN, 2001).…”