CHARACTERISTICS OF SMALL RODENT COMMUNITY IN DIFFERENT AGED CUT-OVER AREAS IN DAILING MOUNTAIN

The field investigation of small rodent community was made in Liangshui Reserve, Heilongiiang Province, in 1992. Species composition and percentage of each species of the small rodents in different aged clear-cut-over areas were analyzed. The change of rodent community was associated with the change of vegetation cover. Forest harvest, which results in change of light, temperature, water and othcr ecological factors, made change of vegetation cover and was the main cause for the change of small rodent community. The small rodents were low in number of species population and diversity index in the inatial stages after clear cutting. The diversity index of rodents in order of different aged cut-over areas were 5-year-old area >20-year-old area > 28-year-old area > 1 -year-old area > 10-year-old area.

Rodent community structure in tropical forests in south Vietnam:comparative ecology of two dominant species and implications for conservation

Rodents were sampled using the capture-mark-recapture technique along transects in disturbed and undisturbed tropical forest in Cat Tien National Park in south Vietnam.The transects comprised two strata:traps were placed on the ground and in the canopy 2–12 m above the ground.At the main transect,which was 1500 m long and located in undisturbed forest,a total of 438 rodents(173 squirrels and 265 murids)of 12 different species(one Scuridae sp.;11 Muridae spp.)were marked between January 2005 and January 2006.At this study site and at another undisturbed tropical forest site in the same area,two species dominated:the rat Maxomys surifer(Miller,1900)and the squirrel Callosciurus flavimanus(Geoffroy,1831).During the study period we observed no significant difference between the average abundances of the two species(4.67±0.86 and 3.1±0.85 individuals per 100 trap nights,respectively)or between the average proportions of resident squirrels and rats(60.0±24.1 and 62.5±11.5,respectively).The number of squirrels that were permanent residents(i.e.dwelling in the same habitat for 1 year)was eightfold the number of rats that were permanent residents.In addition,there was some synchrony in the daily capture dynamics of squirrels and of rats.We observed no significant difference in the total abundance of small mammals between the arboreal and ground strata.At two disturbed tropical forest sites in the same area,however,no such balance between squirrels and rats was observed,and the density of C.flavimanus was very low.We suggest that the relationship between these two dominant species can act as an indicator of the integrity of tropical forest ecosystems in south Vietnam.

Deciphering the effects of disperser assemblages and seed mass on patterns of seed dispersal in a rodent community

The sizes of both seed dispersers and seeds are traits that are likely to interact to influence seed fate in many synzoochoric plant species.Here,we examined whether members of a granivorous rodent community consist­ing of species of different body size vary in their effectiveness as seed dispersers,and how this relationship may be altered by seed size.We marked northern red oak(Quercus rubra)acorns with plastic tags and placed them in size-selective rodent exclosures.The exclosures allowed differential access of rodent groups based on dif­ferent body size:(i)small(e.g.Peromyscus spp.);(ii)small and medium(e.g.Tamias striatus);and(iii)small,medium and large(e.g.Sciurus carolinensis)species of rodents.Acorn removal did not differ among exclosure types,but more seeds were missing when removed by small rodents,probably because of larderhoarding.The treatments did not influence the relative frequency of acorn consumption.However,small rodents cached con­siderably fewer and partially ate more acorns than the other 2 groups.The mean dispersal distance was the lon­gest for cages with medium openings,intermediate for cages with large openings and the shortest for cages with small openings.Acorn mass positively affected the probability of caching and this relationship was unaffected by exclosure type.In conclusion,granivorous rodents of different body sizes strongly differed in their interac­tions with acorns,with small rodents acting primarily as acorn predators and medium and large species contrib­uting significantly more to dispersal of red oaks.

Social and cultural dimensions of rodent pest management

Rice production in Vietnam is threatened by rodent pests, with a significant increase in impact reported from 1990through to the early 21st century. Pre-harvest rice losses are typically 5–10%, with losses of >20% occurring insome years in some regions. Farmers’ rodent control practices are generally reactive and rely essentially on chemicaland physical methods. Ecologically-based rodent pest management (EBRM) was developed in the late 1990s tomanage rodents in rice-based farming systems in Vietnam and other parts of South-East Asia. EBRM combinesboth cultural and physical rodent management practices such as synchrony of cropping, short 2-week rat campaignsat key periods in key habitats, increasing general hygiene around villages, and use of a communitytrap-barrier system. Although EBRM has been reported to be economically profitable, the successful adoption ofthis set of technologies requires community participation. In this paper we address issues relating to the adoptionand sustainability of EBRM in lowland irrigated rice fields in the Mekong Delta in Vietnam. We particularly explorethe social and cultural mechanisms involved in maintaining community participation to further understandthe conditions under which EBRM works and does not work. Positive indications of sustained use of community-based EBRM include: a policy pronouncement from the prime minister directing the use of integrated rodentmanagement;the use of existing cooperatives for developing community actions;budgetary allocation fromprovincial and local governments;diffusion of EBRM to provinces in the south and north that are not involved infarmer participatory field trials;and the adoption of EBRM by a non-governmental organization, World VisionVietnam, in their area-development programs.