Territorial Behaviour and Reproductive Success of Bank Vole Clethrionomys glareolus Females

Abstract

1. Although spacing behaviour in small mammals has been studied extensively, the ultimate function of territoriality in females is frequently under debate. Furthermore, almost no data exists on how territorial behaviour of females changes during reproductive cycles and how that affects their reproductive success. We studied these questions in large outdoor enclosures using the bank vole Clethrionomys glareolus as a study species. 2. Home range dynamics of females and behaviour of territory owners against intruder females were determined during four distinct periods of the reproductive cycle: (i) when females were non-pregnant, (ii) in early pregnancy, (iii) in late pregnancy and (iv) when females were lactating. 3. Home range size and home range overlap of females decreased from period (i) to period (iv) simultaneously when nearest neighbour distance increased. So, at the time of parturition female home range size (foraging area) was at its smallest but territory size (breeding area) at its largest. 4. Attacks of owner females increased and amicable behaviour decreased during the reproductive cycle. Attacks tended to correlate positively and amicable behaviour negatively with home range size. 5. The size of a female's home range significantly correlated with her litter size. However, the weight of females did not correlate with their home range size or litter size. 6. During lactation, nearest neighbour distance correlated negatively with the number of weanlings. Further, home range overlap did not have an effect on the number of weanlings. So, in contrast to an earlier study by Mappes et al. we did not find support for infanticide directly affecting reproductive success of females. That might be due to synchronous breeding in our study females in contrast to females in Mappes et al. 7. Our results indicate that space-resource (large home range) and thus probably food may be an important determinant of litter size in the bank voles. Aggressive defence of a territory may have a role in determining the amount of resources available for reproduction and thus the reproductive success. 8. Our study gives new evidence both for and against the two hypotheses for function of female territoriality and suggests that they are not necessarily mutually exclusive.