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The lesser pouched rat, Beamys hindei, is a small rodent that is patchily distributed in the Eastern Arc Mountains and coastal forests in East Africa. The ecology of this species and its current distribution in coastal forests is not well known. Therefore, we conducted a study in selected coastal forests to assess the current distribution of the species and to investigate the population ecology in terms of abundance fluctuations and demographic patterns. Assessments of the species distribution were conducted in 5 forests through trapping with Sherman live traps. Data on ecology were obtained from monthly capture-mark-recapture studies conducted for 5 consecutive nights per month in two 1 ha grids set in Zaraninge Forest over a 2-year period. The results indicate the presence of B. hindei in 3 forests where it was not previously recorded. The population abundance estimates ranged from 1 to 40 animals per month, with high numbers recorded during rainy seasons. Reproduction patterns and sex ratios did not differ between months. Survival estimates were not influenced by season, and recruitment was low, with growth rate estimates of 1 animal per month. These estimates suggest a stable population of B. hindei in Zaraninge Forest. Further studies are recommended to establish the home range, diet and burrowing behavior of the species in coastal forests in East Africa. [ABSTRACT FROM AUTHOR]

Resistance of rodents to anticoagulant rodenticides has emerged in several areas across the world. Single nucleotide mutations in the vkorc1 gene have been shown to elicit various levels of anticoagulant resistance, and these mutations are prevalent in several Rattus and Mus musculus populations. In sub-Saharan Africa, the Natal multimammate mouse, Mastomys natalensis, is one of the most damaging pests to crops, and anticoagulant poisons such as bromadiolone are frequently used to control these rodents in agricultural fields. Here, we investigate if vkorc1 shows any polymorphism in natural populations of M. natalensis. We sequenced the third exon of vkorc1 of 162 M. natalensis captured from 14 different agricultural sites in Morogoro Region, Tanzania. In addition to 6 SNPs in the noncoding flanking region, we detected 3 nonsynonymous SNPs in this exon: 10 animals (6.2%) carried a Leu108Val variant, 2 animals (1.2%) an Ala140Thr variant, and 1 animal (0.6 %) an Arg100His variant, all 3 in heterozygous form. Ala140Thr is just one residue from a mutation known to be involved in anticoagulant resistance in Rattus and Mus. While in vitro or in vivo experiments are needed to link vkorc1 genetic polymorphisms to level of VKOR activity and anticoagulant susceptibility, our results suggest that M. natalensis individuals may vary in their response to anticoagulant rodenticides. This is the first vkorc1 sequence data from a species outside the Rattus or Mus genera, and for the first time from a rodent species endemic to Africa. [ABSTRACT FROM AUTHOR]

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Differences in the ecological niche requirements among rodent species competing in the same habitat may result from differences in the use of one to three resources: space, time and food or some combination of these. Alternatively, differences in resource use utilization among animal species may simply reflect availability of food, and when food is limited, different animal species compete. In this study, the diet of two rodent pest species, Mastomys natalensis and Gerbilliscus vicinus, coexisting in fallow land in central Tanzania were studied to assess the degree of diet differentiation among them. Dietary niche breadth of G. vicinus was greater than that of M. natalensis in all stages of the maize cropping seasons. The rodent species studied overlapped considerably in the food items consumed ranging from niche overlap (Ojk) of 0.77-0.89. Grains/seeds featured high in the diet of M. natalensis while plant material occurrence was high in G. vicinus. These two food categories may have contributed to differences in diet partitioning, which may, in turn, facilitate their coexistence in fallow land. [ABSTRACT FROM AUTHOR]

The dynamics of infestation and losses of stored maize due to the larger grain borer (Prostephanus truncatus Horn) and maize weevils (Sitophilus zeamais Motschulsky) were investigated in Tanzania. In single species populations, significantly higher maize damage (P ≤ 0.05) was caused by P. truncatus (23.3%) compared to S. zeamais (6.4%). Weight losses caused by P. truncatus were higher (12.7%) than for S. zeamais (6.7%) under similar conditions. A higher proportion of P. truncatus in the initial infestation population led to significantly higher (≤0.05) maize damage compared to equal or higher proportions of S. zeamais. Irrespective of the initial number of S. zeamais, population size increased to levels higher than for P. truncatus. Maize losses in unimproved storage structures were >80% compared to <2.5% in improved structures under natural infestation. Inter-specific competition appeared to influence the dynamics of infestation, damage levels and weight losses. The first two months of storage were critical for damaging insect populations to build up. [ABSTRACT FROM AUTHOR]

A Capture-Mark-Recapture study was undertaken in Central Tanzania to compare variations in community structure and population dynamics of rodents in two types of habitats. The study was conducted in fallow field mosaic habitat dominated by perennial and annual grasses (grid BEA) and a more heterogeneous habitat (grid BEB) which was previously woodland cleared of most trees with vegetation dominated by shrubs, bushes, scattered trees and perennial grass. The relative abundance of rodents in BEA was: Mastomys natalensis (73.5%) > Aethomys chrysophilus (8.9%) > Gerbilliscus vicina (7.3%) > Arvicanthis neumanni (6.1%) > Acomys spinosissimus (4.1%) and for grid BEB: M. natalensis (67.6% ) > G. vicina (11.2%) > A. neumanni (10.3%) > A. chrysophilus (7.6%) > A. spinosissimus (2.9%). Graphiurus sp., Mus minutoides, Saccostomus mearnsi, Lemniscomys striatus and L. griselda were rare and only occasionally trapped in BEB. Spatial variations in population density were non-significant except for A. chrysophilus. Significant temporal variations within grids were observed, with synchrony of population peaks for some species. The rare species boosted species richness of grid BEB rather artificially, without significantly contributing to higher species diversity. Temporal variations in Simpson’s Diversity indices between grids were non-significant except for three out of twenty-one trapping sessions. [ABSTRACT FROM AUTHOR]

The multimammate rat, Mastomys natalensis Smith 1834, is a dominant species in agro-ecosystems in Sub-Saharan Africa, but adapts quickly to changes in non-agricultural landscape, particularly woodlands and forests. In this study we report on reproduction and population dynamics of M. natalensis in deforested high elevation localities in the Usambara Mountains, north-east Tanzania. We conducted Capture-Mark-Recapture studies in 2002-2004, and established that reproduction of M. natalensis takes place in the extended wet season between February and June, and the population density peaks in June-August. Reproduction cease in July to January and population density drops from July onwards. Reproduction and population density fluctuations are linked to the duration and amount of rainfall. In years when rainfall was below average and the wet season was short, the population density was significantly lower (below 10 animals/ha and 60 animals/ha in 2003 and 2004 respectively, compared to >100 animals/ha in 2002 when rainfall was above the seasonal average) (Fdf 2,13= 9.092, p < 0.01 for in between years variations and Fdf 12,15= 5.389, p < 0.01 for effect of cumulative annual rainfall on population density). These densities were much lower than in the lowland savannah habitats in central and southwest Tanzania. A comparison between the farmland/fallow mosaic fields and agro–forestry areas showed higher population densities in the former, which have similarities to the preferred habitats in the lowland savannahs. The increasing abundance of M. natalensis in the Usambara could have some consequences: M. natalensis is major pest and is involved in the plague cycle in the western Usambara Mountains. Mastomys natalensis is also a strong competitor and the impact on endemic rodent species, e.g. Lophuromys flavopunctatus and Praomys delectorum is unknown. [ABSTRACT FROM AUTHOR]

We investigated breeding seasonality and population dynamics of three rodent species, Lophuromys flavopuncatus, Grammomys dolichurus and Praomys delectorum, in the Magamba Forest, Western Usambara Mountains, north-east Tanzania. Capture–mark–recapture studies were conducted in 2002–2004. Reproductive conditions of males and females showed temporal variations, an indication of breeding seasonality. Animals were reproductively active between February and May. Rainfall in November–January was instrumental for the onset of breeding and continued throughout the wet season. The recruitment of new individuals born during the season led to highest population densities between end of May and August. Populations declined progressively towards the end of the dry season (September–October). Only P. delectorum showed a marked density increase during January–February, indicating greater survival and/or recruitment during the November–January rains. The study shows that despite a relatively stable environment of the forest reserve, rainfall has strong influence on reproduction and population dynamics, probably because of its effect on primary food resources. [ABSTRACT FROM AUTHOR]

The influence of time of sowing on the level of infestation of beans, Phaseolus vulgaris (L), by two species of the bean stem maggot (BSM), Ophiomyia spencerella (Greathead) and O. phaseoli (Tyron) (Diptera: Agromyzidae) was investigated during off-season cropping of beans at Madira Farm, Arusha Region, in northern Tanzania. Two bean varieties, Lyamungu 90 and ZPV 292, which are commonly cultivated in the area, were sown and their susceptibility to BSM was assessed. Three sowing dates were adopted; early, normal calendar and late sowing in a split-plot design. The abundance of BSM pupae in bean stems and the number of cracked stems (stem lodging) due to infestation were established. O. spencerella were the dominant bean stem maggots infesting the crop, whereas O. phaseoli infestation was relatively low. Sowing dates had significant (p < 0.001) influence on BSM infestation. The early-sown beans experienced low BSM infestation while the late-sown beans had significantly higher infestation levels. The bean variety ZPV 292 was relatively less infested compared to Lyamungu 90 and was considered tolerant to BSM infestation. Since sowing time had significant effects on BSM infestation, sowing of beans early in the season would enable the crop to escape the peak population of BSM during the most vulnerable growth stage and therefore reduce the effects of the pest on the crop significantly. [ABSTRACT FROM AUTHOR]

Aethomys is a common and widespread rodent genus in the African savannas and grasslands. However, its systematics and taxonomy are still unclear as no study has covered the entire range. In fact it might not be a monophyletic genus and perhaps should be split into two subgenera, Micaelamys and Aethomys. In this paper, we present findings based on the cytogenetics and the entire cytochrome b sequence of two species from Zambia ( A. kaiseri) and Tanzania ( A. chrysophilus), and we compare them with the sequences of a South African species ( A. namaquensis) and other allied muroid genera. Comparison of the banded chromosomes revealed complete G-band homology between the autosomes of the two species. However, the X and Y chromosomes clearly differ in size and in C- and G-banding, being much larger in A. kaiseri. Comparison of the cytochrome b sequences places the separation between A. kaiseri and A. chrysophilus at 4.49 Mya, a period of intense speciation in other African muroids. The resulting phylogeny strongly supports the idea of a paraphyletic group, suggesting the need to elevate the previously described subgenera to the genus rank. [ABSTRACT FROM AUTHOR]

Mice, rats, and other rodents threaten food production and act as reservoirs for disease throughout the world. In Asia alone, the rice loss every year caused by rodents could feed about 200 million people. Damage to crops in Africa and South America is equally dramatic. Rodent control often comes too late, is inefficient, or is considered too expensive. Using the multimammate mouse (Mastomys natalensis) in Tanzania and the house mouse (Mus domesticus) in southeastern Australia as primary case studies, we demonstrate how ecology and economics can be combined to identify management strategies to make rodent control work more efficiently than it does today. Three more rodent-pest systems--including two from Asia, the rice-field rat (Rattus argentiventer) and Brandt's vole (Microtus brandti), and one from South America, the leaf-eared mouse (Phyllotis darwini)--are presented within the same bio-economic perspective. For all these species, the ability to relate outbreaks to interannual climatic variability creates the potential to assess the economic benefits of forecasting rodent outbreaks. [ABSTRACT FROM AUTHOR]

Three sequential plantings of rice were made under irrigated lowland conditions in order to understand the role of insect vectors and the dynamics of Rice yellow mottle virus (RYMV) spread at the Mkindo Irrigation Scheme, Morogoro, Tanzania. Regular samplings of vectors and observations on RYMV throughout the year provide1 information on the abundance of vectors and occurrence of the disease in relation to each of the three traditional rice seasons. Vectors are important in the spread of RYMV and differences in vector population can explain the disease situations in each season. The Masika (February-May) rice was the most infected with RYMV. Also, vector population and RYMV infection increased with crop age. [t is not clear how weather factors relate to the vector population and the disease. Suggestions for future studies are made. [ABSTRACT FROM AUTHOR]

We conducted laboratory experiments to compare the efficacy of four commercial neem, Azadirachta indica, formulations and the synthetic acaricide, Amitraz, against the two spotted spider mites, Tetranychus urticae (Acari: Tetranychidae) and its mite predator, Phytoseiulus persimilis, on tomatoes. Mortality, repellence, feeding deterrence and effects on the predatory mites were established. Among the neem formulations, Neemroc EC at a dose of 20ml/l caused mortality of T. urticae equivalent to the synthetic acaricide (> 93%). Neemros WP gave higher levels of repellence, but relatively lower mortality of T. urticae than any or the other neem formulations. Saroneem and Mitac mixed with Neemros deterred Feeding more than the other formulations, where as Neemros alone did not show any strong feeding deterrence, Neemroc EC deterred feeding more effectively after 72h and compared favourably with the synthetic acaricide. All the neem formulations causes some mortality of the predatory mite, P. persimilis, but it was significantly lower than that by Mitac. The efficacy of the neem products was higher for the oil based formulation (e.g. Neemroc EC) indicating that the activity of azadirachtin, the principal active component of neem extracts, is enhanced by the type of formulation. The study further shows that the neem formulations will be ecologically less disruptive in protecting the tomato crop because they are less toxic to the natural enemy of T. urticae, the predatory mite, P. persimilis. [ABSTRACT FROM AUTHOR]

Rice yellow mottle virus (RYMV) is specific to Africa and has been reported in some countries in East Africa and almost all the countries in West Africa. At present, it is undoubtedly the most important disease of rice in Tanzania. It was first reported in the 1980's. It has spread fast and is now found in almost all the rice growing areas. In view of the increasing incidence and importance of RYMV on rice production in Tanzania, studies on the epidemiology of the disease were initiated in order to find ways of controlling the disease. Transmission studies were carried out on seventy-seven species of beetles and grasshoppers collected from different rice growing locations to determine vector identity. Four vectors have been identified (three chrysomelids; Dactylispa sp.. Chaetocnema sp. and Chaetocnema pulla) and one tetrigid grasshopper. The wide distribution of Chaetocnema spp. in the RYMV endemic areas suggests that the species are the most important vectors responsible for infections in these areas. [ABSTRACT FROM AUTHOR]

Evolutionary information on the greater cane rat (Thryonomys swinderianus) in the Eastern and Southern African regions is scarce, making population management and conservation of the species challenging. We studied T. swinderianus populations from two spatially isolated Eastern Arc Mountains in Tanzania to link molecular and geometric–morphological evidence to characterize these populations' diversity. Fecal samples (n = 50) and skulls (n = 99) of T. swinderianus were collected from Udzungwa (north and south) and Uluguru mountains (urban and rural sites) and analyzed using molecular and geomorphometry techniques. Molecular analysis grouped the population into three distinct clades based on the location where the samples were collected, while the morphometric method was not able to distinctively separate the populations. Both methods revealed that the population obeyed the isolation by distance model with higher genetic distance between the Udzungwa and Uluguru populations and lower distance between Uluguru urban and rural populations. Both Mahalanobis and Procrustes distances in skull landmarks between the Udzungwa and Uluguru populations were significantly higher across the dorsal, ventral, and lateral views of the skulls, suggesting strongly that molecular and morphometric methods applied together can be useful in characterizing the population traits of the least known species. Our study suggests genetic and morphometric methods could complement each other in understanding the evolutionary biology and within-species diversity of vertebrate species that do not exhibit strong intra-species differentiation. [ABSTRACT FROM AUTHOR]

Over the past decades, the number of arthropod-borne virus (arbovirus) outbreaks has increased worldwide. Knowledge regarding the sylvatic cycle (i.e., non-human hosts/environment) of arboviruses is limited, particularly in Africa, and the main hosts for virus maintenance are unknown. Previous studies have shown the presence of antibodies against certain arboviruses (i.e., chikungunya-, dengue-, and zika virus) in African non-human primates and bats. We hypothesize that small mammals, specifically rodents, may function as amplifying hosts in anthropogenic environments. The detection of RNA of most arboviruses is complicated by the viruses' short viremic period within their hosts. An alternative to determine arbovirus hosts is by detecting antibodies, which can persist several months. Therefore, we developed a high-throughput multiplex immunoassay to detect antibodies against 15 medically relevant arboviruses. We used this assay to assess approximately 1,300 blood samples of the multimammate mouse, Mastomys natalensis from Tanzania. In 24% of the samples, we detected antibodies against at least one of the tested arboviruses, with high seroprevalences of antibodies reacting against dengue virus serotype one (7.6%) and two (8.4%), and chikungunya virus (6%). Seroprevalence was higher in females and increased with age, which could be explained by inherent immunity and behavioral differences between sexes, and the increased chance of exposure to an arbovirus with age. We evaluated whether antibodies against multiple arboviruses co-occur more often than randomly and found that this may be true for some members of the Flaviviridae and Togaviridae. In conclusion, the development of an assay against a wide diversity of medically relevant arboviruses enabled the analysis of a large sample collection of one of the most abundant African small mammals. Our findings highlight that Mastomys natalensis is involved in the transmission cycle of multiple arboviruses and provide a solid foundation to better understand the role of this ubiquitous rodent in arbovirus outbreaks. Author summary: One of the main causes of zoonotic related human morbidity and mortality is the transmission of arthropod-borne viruses such as dengue virus, Yellow Fever virus, and chikungunya virus. These viruses cannot only infect humans but also livestock, pets, and wildlife, though our understanding of their non-human hosts remains limited. Rodents are thought to be an important host for these viruses because they can be abundant, often live near humans, and some are already known to be viral hosts. However, research has focused mostly on non-human primates, neglecting other potential wild hosts. To address this gap, we have developed a high-throughput antibody test to screen rodent blood against 15 different arboviruses. Our findings reveal that Mastomys natalensis, a common African rodent species, carries antibodies that (cross-)react against these viruses. We hypothesize that immunologically naïve juveniles may drive transmission, particularly during population outbreaks. These outbreaks coincide with environmental conditions that are favorable for mosquitoes, thus increasing the risk of spillover to humans, livestock, and wildlife. Understanding the role of rodents in arbovirus transmission dynamics is crucial for mitigating zoonotic disease risks. [ABSTRACT FROM AUTHOR]

Rodent population dynamics and survival in semi-arid areas of Tanzania were investigated in fallow land and maize fields (land use) and two soil types (sandy loam and black clay). Capture-Mark-Release (CMR) methods with four 60 m × 60 m trapping grids, (two in maize and two in fallow mosaic fields) were used. Mastomys natalensis comprised >94% of the total captures, and the remaining six percent comprised 11 other small mammals species. The number of M. natalensis was higher in sandy loam (7.82) than in black clay (2.89) soils and higher in fallow land (40.25) than in maize fields (26.49). Highest rodent abundance was observed during the dry season (from June to August) of each year, while the lowest abundance was recorded during the wet seasons (February to April) in both habitats. A significantly different proportion of reproductively active female M. natalensis was observed in sandy loam than in black clay soils. It was observed that female M. natalensis are found to breed almost throughout the year. Survival of M. natalensis differed between dry and wet seasons and was lower in clay soils during the wet season compared to sandy soils. However, there were no significant effects with respect to interactions between soil type and land use, soil type and month, land use and month and soil type, land use and month. Management strategies should therefore, be aimed at emphasizing the importance of targeting March-May in order to interrupt reproduction and young rearing. • We found that Mastomys natalensis was the dominant rodent pest in the study area. • Highest abundance of M. natalensis was observed during the dry season and lowest in the wet season. • More reproductively active females were observed in sandy loam than in black clay soils. • Survival of M. natalensis was higher during the wet than during the dry season. • Survival of M. natalensis was higher in sandy soils than in clay soils. [ABSTRACT FROM AUTHOR]