Happily together forever: temporal variation in spatial patterns and complete lack of territoriality in a promiscuous rodent

Abstract

The availability of resources, their effect on population density and territoriality, and the ways in which these factors are interwoven with mating systems are important determinants of small mammal space use. It is often difficult to study these patterns in an integrated way, however, especially because long‐term data are needed but not readily available. In this paper, we investigate effects of population density, season and breeding status on home range patterns of the promiscuous rodent Mastomys natalensis using monthly capture‐mark‐recapture data collected over 17 years in a 3‐ha grid. Home ranges were estimated using minimum convex polygons bounded by trap locations, and home range overlap and visitation rates were calculated as a measure of territoriality. As higher population densities coincide with increased resource availability, we predicted that home range sizes would correlate negatively with density. Furthermore, as M. natalensis is promiscuous and population densities are generally high, we predicted that territoriality would be low, and home range overlap would therefore be high. Contrary to expectations the home ranges of female adults increased with population density, although those of male adults and subadults followed the expected decrease. Home range overlap and visitation rates were generally high, and increased significantly with population density. More importantly, they were never lower than those of simulated datasets consisting of randomly moved home ranges. These results therefore suggest that M. natalensis displays a complete lack of territoriality that is rarely seen in small mammals but still meets predictions based on knowledge of density and mating system.

Density dependence and persistence of Morogoro arenavirus transmission in a fluctuating population of its reservoir host

“…The mathematical model suggests that the seasonal seroprevalence pattern is best explained by a density‐dependent transmission component ( q = 0). Density‐dependent transmission was already expected for M. natalensis , as it is a non‐territorial generalist species of which the contact rate is likely to increase with density (Borremans et al, ). We do emphasize, however, that it remains difficult to infer the exact transmission–density function based solely on serology data and that controlled field experiments are necessary for more definite answers.…”

“…Mastomys natalensis has a promiscuous mating system and is not territorial or aggressive towards conspecifics (Kennis, Sluydts, Leirs, & Hooft, ). Home range overlap is generally high and increases significantly with abundance, suggesting contact rates to be density‐dependent, probably nonlinearly (Borremans et al, , , ). Given that MORV transmission is most likely density‐dependent, infection is predominantly acute, and the immune response is lifelong, it is surprising that MORV can persist during low host density periods, when host density would be expected to be below the N T (Goyens, Reijniers, Borremans, & Leirs, ).…”

“…The parameter β represents the transmission coefficient, which is depended on the contact rate to a given density and the probability of transmission when an I individual contacts an S (Begon et al, ). Given that M. natalensis is not territorial and its home range overlap is generally high, we assumed a homogeneously mixed community in which all individuals are also identical with respect to susceptibility and infectivity (Borremans et al, ).…”

Relationship between population density and viral infection: A role for personality?

“…Martin and Réale (, ) found that Eastern chipmunks ( Tamias striatus ) whose home range overlapped with their neighbor, spend more time grooming during a hole‐board test than individuals without a neighbor, suggesting that social individuals groom more than others. If this would be the case in M. natalensis , we would expect to catch more individuals that groomed longer at higher density, since home range overlap and visitation rates increases with density (Borremans et al, ). However, larger home range overlaps do not necessarily imply more social contacts.…”

“…Exploration has previously been described in M. natalensis (Vanden Broecke et al, ) and may provide the individual with information about the environment such as the availability of food. This is especially true during the breeding season when food is abundantly available (Leirs, ) and due to their lack of territoriality (Borremans et al, ) and generalist diet (Mulungu et al, ). It may also provide information about the availability of mates, specifically in males who use a scramble mating competition (Kennis et al, ), which could explain our results that males were significantly more explorative than females.…”