Probability of competition between introduced and native rodents in Madagascar: An estimation based on morphological traits

Abstract

An ecomorphological approach was used to estimate the probability of interspecific competition between introduced and native rodents in Madagascar. Comparison of body size, body construction, and craniodental characters leads to the conclusion that there is a high probability of competition between introduced Rattus rattus and the following native taxa: all species of Nesomys, larger semiarboreal Eliurus species (e.g. E. tanala, E. webbi), and especially Gymnuromys roberti. The competitive relationships between introduced rodents and the remaining species of the Nesomyinae have a low probability or are improbable, except possibly for Mus musculus and the so far poorly studied Monticolomys koopmani and Voalavo species.

Broad and flexible stable isotope niches in invasive non-native Rattus spp. in anthropogenic and natural habitats of central eastern Madagascar

“…[18], and they might compete with these species for resources. Indeed, inference of diet overlap has been found based on seeds excavated from burrows of nesomyines and R. rattus in natural forest of the Parc National d’Andringitra, in central southern Madagascar [17].…”

“…negatively impact native communities (reviewed in [ 16 ]). In Madagascar, dietary overlap [ 17 ], as well as external and craniodental morphological characteristics [ 18 ], suggest interference and exploitation competition for the same resources between rats and indigenous rodents. Hence, invasive rats may affect endemic species by the combined effects of predation, competition, and disease transmission.…”

“…In areas where R. rattus have colonized natural habitats, which range from degraded to intact forests, there is an apparent concordant decline in endemic rodents of the subfamily Nesomyinae, which are strictly forest dwelling. However, direct impact of R. rattus on the endemic Malagasy mammalian fauna has been difficult to assess to date [ 18 , 19 ], partly due to a lack of information on diet composition and habitat use of R. rattus . The main aim of this study was to investigate the trophic ecology of invasive R. rattus and R. norvegicus in natural humid forests, where they coexist with native mammals, and in anthropogenic village settings by using stable carbon and nitrogen isotope values of hair to assess indirectly trophic niche variation.…”

“…rattus (Madagascar adult animals, mean total body length 365.0 mm, mean body mass 116.2 g, [ 22 ]) has a wider stable isotope niche than the larger R . norvegicus (Madagascar adult animals, mean total body length 405.0 mm, mean body mass 259.0 g, [ 22 ]) [ 18 ].…”

Phylogeny and extinction risk in mammals

“…We collated measurements for 146 rodent species, using data from previous studies (Miljutin, 1997;Miljutin, 1998Miljutin, , 1999Miljutin, , 2006Miljutin, , 2008Miljutin & Lehtonen, 2008;Miljutin, 2011) and from 584 specimens measured at the mammal collections of the Queensland Museum, Australian Museum, and the ''Alfonso L. Herrera'' Zoology Museum (UNAM, Mexico). The choice of species was opportunistic, based on data availability and how much material was available in collections in good condition.…”