Life traits of Rattus norvegicus and Mus musculus in different habitats and geographic regions

VADELL, MARÍA VICTORIA; CAVIA, REGINO

Congreso; 10th International Mammalogical Congress; 2009

In order to relate life traits of R. norvegicus and M. musculus with the environmental characteristics of their habitats we sampled two urban sites in the city of Buenos Aires and we compiled demographic information available in bibliography. Habitats were classified as urban, rural and natural and climatograms of each of the studied localities were constructed. We analyzed those variables most found in bibliography including estimated abundance, changes in abundance and reproductive activity through out the year, presence or absence of a reproductive break, number of embryos per pregnant female and growth rates. None of the urban populations of R. norvegicus and M. musculus studied showed a break in their breeding cycles. In both species pregnancy prevalences and abundance changed through out the year, pregnacy peaking in spring and summer and abundance generally in autumn. Rural populations of R. norvegicus living in regions where freeze and frost occur showed breaks in there breeding cycle while these breaks were absent in rural populations living in warm regions. In rural populations pregnancy prevalences peaked in spring and summer. Rural populations of M. musculus did not interrupt its breeding cycle in farms while they did so in most crop fields. Pregnancy prevalences were highest mostly in spring. Little demographic information of these species in natural habitats was available. These species showed two life history strategies characterized by: 1) an interruption of their reproduction during the cold season in the least favorable habitats or 2) a decrease in the reproductive investment during the cold season in more favorable habitats. According to the data found, we can conclude that these species always show seasonality in their reproductive investment, even in those habitats which appear more favorable for them such as urban areas in template regions.