The biology and behaviour of a free-living population of black rats (Rattus rattus)

• Main Author: Ewer, Rosalie F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2010
• Subjects: ddc:590; Rattus rattus
• Online Access: http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/19882; https://nbn-resolving.org/urn:nbn:de:hebis:30-81175; http://publikationen.ub.uni-frankfurt.de/files/19882/E000007664_1.pdf

A population of wild Rattus rattus living in the roofs of the laboratory buildings was studied by supplying food every evening and watching the behaviour of the animals at the feeding place. Some observations were also made on caged animals. The rats were predominantly of the black rattus variety but white-bellied greys appeared now and then. In breeding tests the grey colour behaved as though determined by a single recessive gene. The study covered two periods of approximately 9 months each, separated by an interval of 3 months during which a reduced quantity of food was provided and the rat population underwent a major decline. During the two periods of richer feeding the population first increased and then stabilized at a level where the animals remained in good condition and there was no starvation. In the first 9-month period, stabilization was achieved by emigration of young adults who colonized neighbouring buildings. Towards the end of the second period, stabilization was achieved by limitation of breeding. The rats accepted a wide variety of foods, including meat, and a number of instances of predation were seen. Small vertebrates as well as insects were killed and eaten. Small pieces of food were usually eaten in situ but large bits were taken up to the nests in the roof. Such differential treatment in relation to size may be a factor of some importance in the evolution of hoarding. The rats visiting the feeding place formed a unit with a definite social structure. A single dominant male and never more than one, was always present and in certain circumstances a linear male hierarchy was formed. There were usually two or three mutually tolerant top ranking females who were subordinate to the top male but dominant to all other members of the group. Within the group attacks were directed downwards in the social scale. An attacked subordinate either fled or appeased and serious fights therefore did not develop. The most essential component of the appease. ment appeared to be a mouth to mouth contact which ...