The role of competition and habitat in structuring small mammal communities in a tropical montane ecosystem in southern India

Abstract

Small mammals were sampled in two natural habitats (montane stunted evergreen forests and montane grassland) and four anthropogenic habitats (tea, wattle, bluegum and pine plantation) in the Upper Nilgiris in southern India. Of the species trapped, eight were in montane evergreen forests and three were in other habitats. Habitat discrimination was studied in the rodents Rattus rattus and Mus famulus and the shrew Suncus montanus in the montane forest habitat. Multivariate tests on ®ve variables (canopy cover, midstorey density, ground cover, tree density, canopy height) showed that R. rattus uses areas of higher tree density and lower canopy cover. Suncus montanus and M. famulus use habitat with higher tree density and ground cover and lower canopy height. Multivariate tests did not discriminate habitat use between the species. Univariate tests, however, showed that M. famulus uses areas of higher tree density than R. rattus and S. montanus. Rattus rattus was the dominant species in the montane forest, comprising 60.9% of total density, while the rodent Millardia meltada was the dominant species in the grassland. Studies of spatial interaction between these two species in habitats where they coexisted showed neither overlap nor avoidance between the species. Rattus rattus, however, did use areas of lower ground cover than did M. meltada. The analysis of spatial interactions between the species, habitat discrimination and use, and the removal experiments suggest that interspeci®c competition may not be a strong force in structuring these small mammal communities. There are distinct patterns in the use of different habitats by some species, but microhabitat selection and segregation is weak. Other factors such as intraspeci®c competition may play a more important role in these communities.

Non-volant small mammals of the Western Ghats of Coorg District, southern India

“…The dominance of the white-bellied form of Rattus rattus in the semi-evergreen forests of Mudumalai (Venkatraman et al 2005), montane evergreen forests of Nilgiris (Shanker 2001(Shanker , 2003, tropical rainforests of Anamalais (Prabhakar 1998), and middle elevation evergreen forests of the Anamalais (Chandrashekar-Rao & Sunquist 1996), while in our study the white-bellied form of Rattus rattus was dominant only in human habitations and bamboo. In one highly disturbed forest fragment near Ponnampet, with heavy logging and lopping of trees and higher density of bamboos, we recorded only the white-bellied form.…”

Use of arboreal and terrestrial space by a small mammal community in a tropical rain forest in Borneo, Malaysia

“…We estimated whether pairs of species avoided using the same trap or overlapped in trap use with a simple approximation (see Shanker, 2001): the probability of captures of two common species at particular traps was used to calculate the expected number of traps that would capture both species during the entire trapping effort (except for Lenothrix canus and Tupaia gracilis , which were only trapped in area 1): where exp is the expected number of traps that capture both species, a the total number of traps capturing species 1, b the total number of traps capturing species 2, and n the total number of traps ( n 1 = 31 or n 1+2 = 62).…”

Shrew species diversity and abundance in Ziama Biosphere Reserve, Guinea: comparison among primary forest, degraded forest and restoration plots

“…These environmental variables were selected because they were previously shown to potentially influence small-mammal species abundance (Ford et al 1997;Malcolm and Ray 2000;Lehtonen et al 2001;Schmid-Holmes and Drickamer 2001;Shanker 2001;Lambert et al 2003;Greenberg et al 2007). …”

“…These human-induced changes of the forest habitats have many direct and indirect effects on animal communities, such as changes in species richness or species abundance (Bentley et al 2000;Shanker 2001;Estrada and Coates-Estrada 2002;Mathieu et al 2005;Pineda et al 2005). The impact of deforestation on communities depends on the forest type, the size and shape of the deforested patch (Bentley et al 2000;Goodman and Rakotondravony 2000;Laidlaw 2000;Ramanamanjato and Ganzhorn 2001;Watson et al 2004a), the intensity of the disturbance (Struhsaker 1997;Lewis 2001) and the landscape context (Saunders et al 1991;Malcolm and Ray 2000;Putz et al 2001;Watson et al 2004b).…”