**Author details**

*Rodents*

**Figure 4.**

**30**

**5. Conclusion**

low and flat Mukojima Islands [27]. Therefore, Norway rats probably thrive better

*Comparison of body weight in grams (*Y*) and log value of age in months (*X*) and resulting regression lines for male and female Norway rats from the Hahajima Islands, Yururi-Moyururi, and a business district in Yokohama excluding pregnant females, showing infection with rat lungworms (*Angiostrongylus cantonensis*) [7]. Circles and triangles show rats that were negative and those that were positive for the infection, respectively.*

Renal structures show that the ability to concentrate urinary water in Norway rats is like that in roof rats [59]. However, protein-rich diets demand a larger turnover of water than diets rich in carbohydrates or fat [48], and Norway rats feed on protein-rich diets, whereas roof rats prefer plant matter to animal matter [6]. Therefore, Norway rats require more water intake than roof rats. This difference in water requirements is probably one of the factors that separate the two species in the geographical distribution especially in tropical and subtropical climate zones [15]. Mild temperature is a secondary factor in determining the Norway rat distribution, after water balance and an appropriate diet. Even in the tropical climate zone, Norway rats are prosperous in large cities such as Bangkok (13° 44′ N, 100° 29′ E) and Chanthaburi (12° 36′ N, 102° 06′ E) in Thailand, which are surrounded by networks of watercourses and damp environments [15, 60]. Generally, in these habitats, there are protein-rich diets including garbage and invertebrates such as earthworms and insects [6]. Therefore, protein-rich diets and the means for avoiding dehydration such as creeks and sewage provide Norway rats with thriving habitats in large cities. These facts suggest that diets rich in animal matter or protein are associated with water balance, which are essential factors in the geographical distribution of Norway rats.

Mild temperature is a secondary factor in the reproductive activities of Norway

rats as was proved by the results in Yururi-Moyururi in the subarctic zone and

in the Hahajima Islands than in the others.

Tatsuo Yabe Rat Control Consulting, Yamato, Japan

\*Address all correspondence to: rccty@js8.so-net.ne.jp

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
