Spelling suggestions: "subject:"[een] RODENTS"" "subject:"[enn] RODENTS""
141 |
The interplay of habitat and seed size on the shift in species composition in a fragmented Afromontane forest landscape: Implications for the management of forest restorationBabale, Aliyu January 2014 (has links)
The Cameroon Highlands that run along the Cameroon-Nigeria border are an important source of biodiversity. Not only are they rich in species and high in endemics, but biota from West Africa have not been studied as extensively relative to other parts of the Afrotropics, or the tropics in general. Threatening these rare and diverse habitats is anthropogenic pressure, which fragments forests and changes local animal communities. This thesis wished to address the impact of humans on seed dispersal and recruitment processes on selected tree species in forests on the Mambilla Plateau - a montane region in Nigeria's north-east. Research was conducted at Ngel Nyaki Forest Reserve, a conservation area established by the Nigerian Montane Forest Project. The reserve comprises a moderately-large forest patch (Ngel Nyaki Forest) and many small riparian fragments embedded in a grassland matrix. Cattle grazing and burning of this grassland are major threats to the survival of forest in this area.Hunting of local wildlife for bushmeat is also of concern, considering many of the region’s large-mammalian fauna are now locally extirpated (e.g. elephants) or at low abundances (many primate species). Loss of large-bodied frugivorous species has the potential to negatively impact the recruitment of large-seeded tree species that solely rely on them as seed dispersers. In this study, the ability for scatterhoarding rodents to act as surrogate dispersers for large-seeded species is tested. While much research has been carried out on secondary rodent dispersal in the Neotropics, work in the Afrotropics is still in its infancy. Because the outcome of plant-rodent interactions (i.e. predated or dispersed) may vary with season, habitat, or traits of the seed species in question, a number of experiments were established to quantify how local rodents at Ngel Nyaki may or may not be acting as effective dispersers. Additionally, the benefits of rodent dispersal were examined by creating an experiment that simulated secondary dispersal on seedling recruitment. The results of this study demonstrated that rodents can act as effective dispersers in Afromontane forests, but this is influenced by habitat, seasonal abundance of resources, and palatability of seed species. Furthermore, it was demonstrated that burial of seeds by rodents can increase the establishment probability of a seed by protecting it from removal by other rodents. However, while rodents play a strong driver of seed survival, it was also demonstrated that seedling mortality factors (such as herbivory) can also be heavy filters to seedling success. It is hoped that the results of this study will help to inform better management decisions and understand how the composition of the forest might change in the future.
|
142 |
Discrimination and preference to salivary olfactory cues in three species of rodentsFriedle, Robert Eugene January 1983 (has links)
This thesis examined the odiferous nature of rodent saliva for the male Mongolian gerbil, male and diestrous female golden hamsters, and male and female degus. Within each species,like-sexed pairs were dichotomized as to dominance or submissiveness and individual animals were presented with salivary samples from dominant pairings, an opposing gender, and a saline control; in an open field arena. Both degus and gerbils did not show any discriminative responding, via sniffs, time spent in proximity of and approaches to allstimuli. Degus discriminated salivary stimuli over the control when allowed to contact the stimuli. Degus preferred, via approaches, female samples. Male hamsters discriminated amongst all stimuli for the three behavioral measures. Dominant males preferred other male cues over diestrous female and saline samples via sniff. For approaches, dominant males preferred other dominant cues over submissive or female cues. Submissives preferred all salivary cues over the control via sniffs, but showed no individual preferences amongst the salivary cues. Female hamsters discriminated amongst all stimuli via sniffs. Dominant females preferred other submissive samples over those of a male and preferred dominant and submissive samples over the control, submissive females preferred all three salivary cues over the control; no other preferences were found. The importance of salivary cues and the odiferous nature of chemical cues of all secretory by-products of rodents are discussed.
|
143 |
The influence of abiotic processes, competition and predation on the community structure of rodents and shrews.Delcros, Gwenaelle. January 2012 (has links)
Predation and abiotic processes rather than competition should influence the community structure
of rodents and shrews with life histories characterised by high fecundity, short longevity and
unstable populations. I investigated the influence of abiotic processes, predation and competition
on three parameters of community structure (species composition, phenotypic and phylogenetic
niches) of rodents and shrews at Mkhuze and Kube Yini, two game reserves in KwaZulu-Natal,
South Africa, using null models and multivariate analyses. Rodents and shrews were sampled
between 2007 and 2009. Sample-based rarefaction curves indicated that rodent species richness
was higher at Mkhuze than at Kube Yini, while shrew species richness was identical at both
reserves. Species richness estimators indicated that estimates of species richness were fairly
accurate, hence strengthening the results from my null model analyses.
I found evidence that immigration and extinction operating at a regional scale influenced rodent
species composition. Moreover, habitat filtering operating at a local scale influenced rodent and
shrew species composition. These processes produced nested assemblages: species present at
species-poor sites were subsets of species present at species-rich sites. Habitat filtering also
influenced the phenotypic niche of rodents and shrews: sympatric species showed similar
phenotypic adaptations (phenotypic niches were underdispersed), probably in response to similar
food requirements. Furthermore, shrew phenotypic traits showed a convergent evolution, and local
assemblages comprised distantly related species (phylogenetic evenness), suggesting the influence
of habitat filtering on the phylogenetic niche structure of shrews.
Predation influenced shrew phenotypes. Bullae and ears were underdispersed and larger than
expected by chance, probably to reduce predation risk through increased hearing sensitivity. In
contrast, I found no evidence that predation influenced the rodent phenotypic niche.
Competition influenced the phenotypic niches of rodents and shrews in species-rich assemblages
(phenotypic niches were overdispersed). In these assemblages, the coexistence of species was
facilitated by dietary and microhabitat partitioning. Competition also influenced the phylogenetic
niche of rodents: phenotypic traits showed a convergent evolution, and local assemblages
comprised closely related species (phylogenetic clustering).
In conclusion, both abiotic and biotic processes influenced different parameters of the community
structure of rodents and shrews. However, despite similar life-history traits, the community
structure of local assemblages differed between rodents and shrews. Comparing patterns and
processes of community structure across taxa would help find general trends of community
organisation. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2012.
|
144 |
Ecological impacts of Highveld gerbils (Tatera Brantsii) on a rehabilitated ash disposal site / Nevil Ian WrightWright, Nevil Ian January 2006 (has links)
Tatera brantsii was numerically dominant in the small mammal community on the plateaux
of the rehabilitated ash disposal sites of ESKOM's Hendrina Power Station in 1998 and 1999
(Vermaak 2000). The species seemed well adapted to exploit this environment and, through
biopedturbation, had altered the topsoil structure and chemistry. The consequences of this and
other activities also affected the rehabilitated plant community of the PFA-dam habitat.
Burrowing appeared limited to just under the topsoil layer, and seemed more extensive than
burrows of this species in natural ecosystems. The burrow system architecture was mapped
and quantified, and localised increases in nitrates, phosphorous and organic carbon in
immediately associated substrate were noted. However, this substrate enrichment was
transient, and disappeared following the abandonment, and subsequent collapse of burrow
systems, when gerbil colonies migrated away from the area. The mixing of soil horizons also
resulted in a more homogeneous substrate, which was more friable, and thus drier. The high
pH and salinity of the topsoil layer in areas undisturbed by gerbil burrowing, and
concentrations of particular elements associated with either the topsoil covering or the ash,
were reduced as a consequence of substrate mixing in disturbed areas. Gerbil impacts on the
substrate of this habitat seemed to promote pedogenesis, eliminating the sharp distinction
between the topsoil covering and the ash below, but the re-exposed ash of the burrow mounds
would become subject to erosion, and reduce the effectiveness of the rehabilitation effort.
Gerbil activities increased the number of plant species, especially ruderal forbs, comprising
the plant community of the PFA-dam habitat, but plant community diversity was not
significantly increased. However, numerical dominance by few tussock grass species was
diminished , possibly reflecting burial under mounds of excavated substrate. The biomass and
cover of some grass species were reduced in areas of gerbil impacts, and plant lifecycles
appeared to be completed sooner in areas affected by gerbil activities. These effects may be as
a result of the drier substrate produced following the collapse of the extensive network of
abandoned burrows. The succession of this plant community towards an underutilised
grassland state, the expected outcome of the rehabilitation effort, was minimally affected by
gerbil activities. The effects of T.brantsii activities in this PFA-dam habitat were not as
distinct as the effects noted by other authors studying fossorial rodent impacts in less
disturbed habitats. This could be because further disturbances in this habitat would merely
add to the currently disturbed state, whereas disturbance in more natural habitats, would show
more of a change from the initial state. / Thesis (M.Sc. (Zoology))--North-West University, Potchefstroom Campus, 2007.
|
145 |
Laukinių pelinių graužikų užsikrėtimas kaspinuočių metacestodais Lietuvoje / Metacestode infection in free living rodent populiations in LithuaniaUrbelytė, Danguolė 05 March 2014 (has links)
Šio darbo tikslas buvo nustatyti gamtoje gyvenančių pelinių graužikų populiacijos sudėtį ir jų užsikrėtimą kaspinuočių metacestodais centrinėje ir pietvakarinėje Lietuvos dalyje. Tyrimas atliktas 2013 metų pavasario ir rudens laikotarpiais. Graužikų gaudymui vietovės pasirinktos keturiuose rajonuose. Graužikai buvo gaudomi mušamaisiais spąstukais, juos dėliojant kvadratais pasirinktose vietovėse. Nustatyta, kad Lietuvos centrinėje ir pietvakarinėje dalyse vyraujančios graužikų gentys yra Microtus spp. Apodemus agrarius, Sorex spp., Myodes glareolus, Apodemus flavicolis. Smulkieji graužikai buvo tiriami parazitologijos laboratorijoje, vizualiai apžiūrimos kepenys. Nustatyta, kad labiausiai paplitusi ir daugiausiai rasta kaspinuočių metacestodų pas Microtus spp. genties graužikus, kurių pagauta 314 vnt. Jų užsikrėtimas gausiausias 10,5 proc. (95 %; PI 7,3-14,4), Myodes spp. užsikrėtimas siekė 8,2 proc. (95 % PI 2,3-19,6), Sorex spp. 7.3 proc. (95%; PI 2,0- 17,6), Apodemus spp. 1,6 proc. (95 %; PI 0,2-5,6), Arvicola spp. 50 proc. (95 %; PI 1.3-98.7), Talpa europea 4.5 proc. užsikrėtimas (95 %; PI 0,1-22,8). / The aim of this study was to identify the composition of free living rodent populations and their infection with metacestodes in central and south-west Lithuania. The study was performed in spring and autumn of 2013. Sampling sites were selected in four different districts. Rodents were caught using snap trappings by setting them in squareswithin chosen areas. Small rodents were investigated by visual examination of livers in the laboratory of parasitology. It was found that dominated genus of rodents were Microtus spp., Apodemus agrarius, Sorex spp., Myodes glareolus and Apodemus flavicolis. Microtus spp.(n=314) were the most frequently (10.5 %; 95 % CI 7,3-14,4) infected species with metacestodes. Other species infected were Myodes spp.(8,2 %; 95 % CI 2,3-19,6), Sorex spp. (7,3 %; 95% CI 2,0- 17,6), Apodemus spp. (1,6 %; 95 % CI 0,2-5,6) and Arvicola spp. (50 %; 95 % CI 1,3-98,7).
|
146 |
Rattus tanezumi in the upland rice terraces of Banaue, Philippines: demography, habitat use, crop damage and yield assessment.Miller, Rachel Weslie, Biological, Earth & Environmental Sciences, Faculty of Science, UNSW January 2007 (has links)
Rodents cause significant damage to agricultural crops throughout the world, including rice, the staple food for the increasing population of Southeast Asia. Little is known about the ecology of pest rodent species, resulting in much effort being concentrated on ineffective, time consuming control practices. This research was designed to understand the demography and habitat use of the major pest rodent (Rattus tanezumi) of the Banaue rice terraces in order to identify the most efficient time and location to undertake pest control. Rodent crop damage and associated yield loss was also assessed in order to provide information for a cost : benefit analysis of rodent control practices. And the beliefs, perceptions and practices of Banaue rice farmers were investigated to assist in identifying future compatible rodent control programs. Replicated cage trapping was undertaken for a twelve month period over the entire rice cropping season in two study sites in the Municipality of Banaue Philippines. The breeding season of R. tanezumi corresponded with periods of food availability from the transplanted to ripening stages of the rice crop. A non-breeding season occurred from the fallow to seedling stages. The distinct breeding season occurred within the rice fields and adjacent village and scrub habitats. Radio-tracked and spool-and-line tracked R. tanezumi moved from adjacent habitats into the rice field during the breeding season, and individuals persisted in all habitat types, including the rice field, during the fallow, nonbreeding season. Overall rice yield was significantly greater (43%) in areas where rodents were excluded by fencing compared to areas where rodents were not excluded. More rodent damage to rice tillers occurred at the booting than at the ripening stage of the rice crop. These results suggest that to prevent rodent damage, control should be undertaken at the end of the R. tanezumi non-breeding season (prior to transplanting), before rodent numbers multiply and crop damage occurs. Further, the cost-benefit analysis of non-chemical rodent control programs in Banaue, suggests that benefits accrue once yield loss is likely to exceed 5%.
|
147 |
Rattus tanezumi in the upland rice terraces of Banaue, Philippines: demography, habitat use, crop damage and yield assessment.Miller, Rachel Weslie, Biological, Earth & Environmental Sciences, Faculty of Science, UNSW January 2007 (has links)
Rodents cause significant damage to agricultural crops throughout the world, including rice, the staple food for the increasing population of Southeast Asia. Little is known about the ecology of pest rodent species, resulting in much effort being concentrated on ineffective, time consuming control practices. This research was designed to understand the demography and habitat use of the major pest rodent (Rattus tanezumi) of the Banaue rice terraces in order to identify the most efficient time and location to undertake pest control. Rodent crop damage and associated yield loss was also assessed in order to provide information for a cost : benefit analysis of rodent control practices. And the beliefs, perceptions and practices of Banaue rice farmers were investigated to assist in identifying future compatible rodent control programs. Replicated cage trapping was undertaken for a twelve month period over the entire rice cropping season in two study sites in the Municipality of Banaue Philippines. The breeding season of R. tanezumi corresponded with periods of food availability from the transplanted to ripening stages of the rice crop. A non-breeding season occurred from the fallow to seedling stages. The distinct breeding season occurred within the rice fields and adjacent village and scrub habitats. Radio-tracked and spool-and-line tracked R. tanezumi moved from adjacent habitats into the rice field during the breeding season, and individuals persisted in all habitat types, including the rice field, during the fallow, nonbreeding season. Overall rice yield was significantly greater (43%) in areas where rodents were excluded by fencing compared to areas where rodents were not excluded. More rodent damage to rice tillers occurred at the booting than at the ripening stage of the rice crop. These results suggest that to prevent rodent damage, control should be undertaken at the end of the R. tanezumi non-breeding season (prior to transplanting), before rodent numbers multiply and crop damage occurs. Further, the cost-benefit analysis of non-chemical rodent control programs in Banaue, suggests that benefits accrue once yield loss is likely to exceed 5%.
|
148 |
Telomerase expression in the adult rodent central nervours system and telomeric characteristics of neural stem cells from adult brainWu, Gang, January 2008 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 100-122) Also available in print.
|
149 |
Chromosomes, sex-cells, and evolution in a mammal based mainly on studies of the reproductive glands of the gerbil, and a new list of chromosome numbers of mammals.Tobias, Phillip V. January 1956 (has links)
Thesis--University of the Witwatersrand. / Bibliography: p. [363]-384.
|
150 |
Small mammal communities in the transformed landscapes of the Western Cape Lowlands and their role in alien invasion into Fynbos remnants /Mugabe, James Chapangara. January 2008 (has links)
Thesis (MScConEcol)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.
|
Page generated in 0.0497 seconds