Gry Gundersen

• Glorvigen, Petter; Gundersen, Gry; Andreassen, Harry Peter & Ims, Rolf Anker (2013). The role of colonization in the dynamics of patchy populations of a cyclic vole species. Oecologia. ISSN 0029-8549. 173(1), s. 161–167. doi: 10.1007/s00442-013-2614-y. Fulltekst i vitenarkiv
• Remy, Alice Melisande Jacynthe; Galliard, Jean-François Le; Gundersen, Gry; Steen, Harald & Andreassen, Harry Peter (2011). Effects of individual condition and habitat quality on natal dispersal behaviour in a small rodent. Journal of Animal Ecology. ISSN 0021-8790. 80(5), s. 929–937. doi: 10.1111/j.1365-2656.2011.01849.x. Fulltekst i vitenarkiv
• Hoset, Katrine S.; Galliard, Jean-François Le & Gundersen, Gry (2009). Demographic responses to a mild winter in enclosed vole populations. Population Ecology. ISSN 1438-3896. 51(2), s. 279–288. doi: 10.1007/s10144-008-0130-4. Fulltekst i vitenarkiv
• Rosell, F; Gundersen, Gry & Galliard, JF Le (2008). Territory ownership and familiarity status affect how much male root voles (Microtus oeconomus) invest in territory defence. Behavioral Ecology and Sociobiology. ISSN 0340-5443. 62, s. 1559–1568. doi: 10.1007/s00265-008-0585-5. Fulltekst i vitenarkiv Vis sammendrag

  Neighbour–stranger discrimination occurs when individuals respond with more aggression to strangers than to territorial neighbours—a phenomenon termed the “dear enemy phenomenon” (DEP). We investigated the DEP with male and female root voles (Microtus oeconomus Pallas 1776) using field dyadic arena tests conducted in enclosures where we could test for the effects of familiarity (familiar versus stranger), ownership (resident versus intruder status) and resource-holding potential (body mass) on territorial behaviours. The results showed that males put more effort into territorial defence than females, and males could discriminate between neighbours and strangers. In males, aggressiveness was influenced by a significant two-way interaction between treatment and ownership. Male residents were more aggressive towards stranger intruders than towards neighbour intruders, while male intruders were less aggressive towards stranger residents than towards neighbour residents. In females, neither treatment nor ownership status had a significant effect on aggressiveness. Familiar males performed more social behaviours but less non-social behaviours than stranger males. Furthermore, there was a clear dominance hierarchy between residents and intruders in stranger dyads, with the male territory holders dominating the intruder in pairwise interactions. To our knowledge, these results demonstrate for the first time DEP in a small mammal with a known pedigree and present the first evidence for “prior resident advantage” in voles. We argue that both ownership status and familiarity status affect how much an individual invests in territory defence. The benefits of neighbour–stranger discrimination for male root voles and the absence of neighbour–stranger discrimination in female root voles are discussed.

• Hoset, Katrine S.; Galliard, Jean-François Le; Gundersen, Gry & Steen, Harald (2008). Home range size and overlap in female root voles: effects of season and density. Behavioral Ecology. ISSN 1045-2249. 19. doi: 10.1093/beheco/arm112. Fulltekst i vitenarkiv
• Rosell, Frank; Rosell, Frank; Gundersen, Gry & Galliard, Jean F. Le (2008). Territory ownership and familiarity status affect how much male root voles (Microtus oeconomus) invest in territory defence. Behavioral Ecology and Sociobiology. ISSN 0340-5443. 62(10), s. 1559–1568. doi: 10.1007/s00265-008-0585-5. Fulltekst i vitenarkiv Vis sammendrag

  Neighbour-stranger discrimination occurs when individuals respond with more aggression to strangers than to territorial neighbours-a phenomenon termed the "dear enemy phenomenon" (DEP). We investigated the DEP with male and female root voles (Microtus oeconomus Pallas 1776) using field dyadic arena tests conducted in enclosures where we could test for the effects of familiarity (familiar versus stranger), ownership (resident versus intruder status) and resource-holding potential (body mass) on territorial behaviours. The results showed that males put more effort into territorial defence than females, and males could discriminate between neighbours and strangers. In males, aggressiveness was influenced by a significant two-way interaction between treatment and ownership. Male residents were more aggressive towards stranger intruders than towards neighbour intruders, while male intruders were less aggressive towards stranger residents than towards neighbour residents. In females, neither treatment nor ownership status had a significant effect on aggressiveness. Familiar males performed more social behaviours but less non-social behaviours than stranger males. Furthermore, there was a clear dominance hierarchy between residents and intruders in stranger dyads, with the male territory holders dominating the intruder in pairwise interactions. To our knowledge, these results demonstrate for the first time DEP in a small mammal with a known pedigree and present the first evidence for "prior resident advantage" in voles. We argue that both ownership status and familiarity status affect how much an individual invests in territory defence. The benefits of neighbour-stranger discrimination for male root voles and the absence of neighbour-stranger discrimination in female root voles are discussed.

• Galliard, Jean-François Le; Gundersen, Gry & Steen, Harald (2007). Mother-offspring interactions do not affect natal dispersal in a small rodent. Behavioral Ecology. ISSN 1045-2249. 18, s. 665–673. doi: 10.1093/beheco/arm023. Fulltekst i vitenarkiv
• Galliard, Jean-Francois Le; Gundersen, Gry & Steen, Harald (2007). Mother-offspring interactions do not affect natal dispersal in a small rodent. Behavioral Ecology. ISSN 1045-2249. 18(4), s. 665–673. Fulltekst i vitenarkiv Vis sammendrag

  According to kin selection and inbreeding avoidance hypotheses, natal dispersal should be facultatively adjusted to balancing the costs and benefits of mother?offspring interactions. In polygynous mammals, it is hypothesized that female offspring should seek to avoid local resource competition with their mother, whereas male dispersal should be determined by inbreeding avoidance. We tested these hypotheses with a field experiment investigating the relationship between territory acquisition and mother's presence in the root vole Microtus oeconomus. This species has a flexible social system in which sisters' and mother's home ranges overlap substantially, whereas sons disperse to a greater extent. Immature sibling voles aged 20 days were released for 20 days together with an unrelated adult male in a 2-patch system either in the presence of their mother or in the presence of an unrelated adult female. Offspring movements were not influenced by mother's presence, but offspring, especially females, avoided the patch occupied by the adult female irrespective of kinship. Offspring remaining in contact with their mother were reproductively suppressed at the middle, but not by the end, of the experimental period. These results indicate that juvenile root voles adopted an opportunistic settlement strategy where they avoided the adult female irrespective of kinship and inbreeding risks. doi:10.1093/beheco/arm023

• Andreassen, H. P. & Gundersen, Gry (2006). Male turnover reduces population growth: An enclosure experiment on voles. Ecology. ISSN 0012-9658. 87(1), s. 88–94. Fulltekst i vitenarkiv
• Galliard, Jean F. Le; Gundersen, Gry; Andreassen, Harry P. & Stenseth, Nils Christian (2006). Natal dispersal, interactions among siblings and intrasexual competition. Behavioral Ecology. ISSN 1045-2249. 17(5), s. 733–740. Fulltekst i vitenarkiv Vis sammendrag

  According to the classical model of a polygynous mating system, male-biased dispersal is a consequence of inbreeding avoidance and sexual asymmetries in competition. However, kin cooperation can change the costs and benefits of dispersal to each sex and may also select for philopatry in females. Here, we report from an experimental study designed to tease apart the effects of competition, cooperation, and inbreeding avoidance on natal dispersal in juvenile root voles (Microtus oeconomus). We manipulated the presence of opposite-sex littermates and tested how interactions among siblings influence dispersal and sexual maturation. We also manipulated the juvenile sex ratio to compare the strength of intrasexual versus intersexual competition. Natal dispersal was unrelated to the juvenile sex ratio, females aggregated in space, and there was a consistent spatial overlap among sisters. Males dispersed more in the absence of their sisters, resulting in stronger spatial segregation between sexes, than in the presence of their sisters. Thus, natal dispersal did not reduce the risks of interactions with siblings and intrasexual competition. We suggest that kin clusters in females function as a defense against aggressive or infanticidal behavior by unfamiliar males.

• Andreassen, Harry P. & Gundersen, Gry (2006). Male turnover reduces population growth: An enclosure experiment on voles. Ecology. ISSN 0012-9658. 87(1), s. 88–94. Fulltekst i vitenarkiv Vis sammendrag

  Turnover of individuals is assumed to cause disruptions of social organization, followed by reduced reproduction and survival. We tested how male turnover (removal of resident males and their replacement by unfamiliar males) affected population performance in experimental root vole (Microtus oeconomus) populations. The treatment simulated predation of adult males, with the subsequent replacement by immigrants, and provided insight into the interaction between extrinsic (i.e., predation) and intrinsic (i.e., social organization) factors. We showed that recruitment and female survival dramatically declined and that reproduction commenced slightly later in treatment populations compared with control populations. The treatment nearly halved the population growth rate. We suspect that recruitment failed due to infanticidal immigrating males. Reduced female survival was particularly apparent in treatment populations in which females exhibited a high degree of spatial overlap. Our experimental results show how males may significantly shape population dynamics and suggest how predation and social factors interact mechanistically.

• Galliard, Jean-François Le; Gundersen, Gry; Andreassen, H. P. & Stenseth, Nils Christian (2006). Natal dispersal, interactions among siblings and intrasexual competition. Behavioral Ecology. ISSN 1045-2249. 17, s. 733–740. Fulltekst i vitenarkiv
• Gundersen, Gry; Andreassen, Harry Peter & Ims, Rolf Anker (2002). Individual and population level determinants of immigration success on local habitat patches: an experimental approach. Ecology Letters. ISSN 1461-023X. 5(2), s. 294–301. Fulltekst i vitenarkiv Vis sammendrag

  The effect of population density on immigration success of young root voles was studied in a factorial experiment where immigrants of three different types were translocated from donor populations to recipient habitat patches with experimentally manipulated population sizes. The different types of immigrants were 1) Residents: animals that had remained in their natal patch, 2) Colonists: animals that already had successfully dispersed and settled in a new patch, and 3) Transients: animals roaming around in a non-habitable matrix area of the donor population. Generally, we found evidence for a negative density-dependent immigration success in terms of survival, rate of sexual maturation and body growth rate. With respect to the survival rate, the degree of density-dependence differed among the three immigrant types. Our findings are discussed with respect to the degree of rescue effect immigrants may provide on a recipient population depending on population density, and also its relevance concerning translocation of individuals for conserving endangered populations.

• Gundersen, Gry; Andreassen, Harry P. & Ims, Rolf A. (2002). Individual and population level determinants of immigration success on local habitat patches: An experimental approach. Alces. ISSN 0835-5851. 5, s. 294–301. Fulltekst i vitenarkiv
• Gundersen, Gry (2002). Atferdsbiologiske hensyn viktig i forvaltningen; illustrert ved infanticide atferd. Biolog. ISSN 0801-0722. 1, s. 2–3. Fulltekst i vitenarkiv Vis sammendrag

  Hos mange pattedyrarter utføres infanticide (ungedrap) av voksne hanner. Atferden antas å ha evolvert som en strategi for å fremme utøverens egen reproduktive suksess ved å drepe avkom de selv ikke er far til. På den måten fremskyndes tidspunktet da moren igjen vil bli mottakelig for parring og kan få nye avkom. Under normale forhold kan en slik situasjon eksempelvis finne sted ved at en ung fremmed hann utfordrer en gruppes dominante leder for å overta hans harem. Hvis han lykkes vil han avlive de av flokkens unger som fremdeles befinner seg på die-stadiet og dermed starte egen produksjon av avkom i løpet av kort tid. I dette innlegget vil jeg fokusere på populasjoner som grunnet ulik menneskelig inntreden kan bli utsatt for faretruende høye rater av infanticide.

• Gundersen, Gry; Johannesen, Edda; Andreassen, Harry P. & Ims, Rolf A. (2001). Source-sink dynamics: how sinks affect demography of sources. Ecology Letters. ISSN 1461-023X. s. 14–21. Fulltekst i vitenarkiv
• Gundersen, Gry; Ims, Rolf A.; Aars, Jon & Andreassen, Harry P. (2001). Inbreeding in the field: An experiment on root vole populations. Canadian Journal of Zoology. ISSN 0008-4301. 79, s. 1901–1905. Fulltekst i vitenarkiv
• Gundersen, Gry; Aars, Jon; Andreassen, Harry Peter & Ims, Rolf Anker (2001). Inbreeding in the field: an experiment on root vole populations. Canadian Journal of Zoology. ISSN 0008-4301. 79, s. 1901–1905. Fulltekst i vitenarkiv Vis sammendrag

  We used a field experiment with replicate populations of a particular geographic race of root voles (Microtus oeconomus) with different degrees of inbreeding to test whether inbreeding effects were expressed in demographic parameters. This geographic race had been shown to exhibit reduced reproductive rate in the laboratory as resulting from inbreeding depression. There were no effect of inbreeding on population growth rate or any demographic parameter. Inbreed animals grew less than outbred early in the summer, but this had no demographic consequences. Our study is one of the few comparing the performance of the same species or race with respect to extent inbreeding depression in the laboratory and the field. More such comparisons will be needed to decide whether inbreeding is more detrimental in the field than in the laboratory.

• Gundersen, Gry; Johannesen, Edda; Andreassen, Harry Peter & Ims, Rolf Anker (2001). Source-sink dynamics: how sinks affect demography of sources. Ecology Letters. ISSN 1461-023X. 4, s. 14–21. Fulltekst i vitenarkiv Vis sammendrag

  Models of source-sink population dynamics have to make assumptions about whether, and eventually how, demographic parameters in source habitats are dependent on the demography in sink habitats. However, the empirical basis for making such assumptions has been weak. Here we report a study on experimental root vole populations, where estimates of demographic parameters were contrasted between source patches in source-sink (treatment) and source-source systems (control). In the presence of a sink patch (simulated by a pulsed removal of immigrants), source-patch populations failed to increase over the breeding season, mainly due to a high spatially density-dependent dispersal rate from source to sink patches. The per capita recruitment rate was almost two times higher in source-sink than in the source-source systems, but this did not compensate for the loss rate due to dispersal from source to sink patches. Sex ratio in the source-sink systems became less female biased, probably as a result of an enhanced frequency of dispersal movements in females. Good knowledge of the degree of density- and habitat-dependent dispersal is critical for predicting the dynamics of source-sink populations.

• Gundersen, Gry; Moe, Jannecke A.; Andreassen, Harry Peter; Carlsen, Rine G. & Gundersen, Hege (1999). Intersexual attraction in natal dispersing root voles Microtus oeconomus. Acta Theriologica. ISSN 0001-7051. 44(3), s. 283–290. Fulltekst i vitenarkiv
• Gundersen, Gry; Moe, Jannecke A.; Andreassen, Harry P.; Carlsen, Rine G. & Gundersen, Hege (1999). Intersexual attraction in natal root voles Microtus oeconomus. ?. 44(3), s. 283–290. Fulltekst i vitenarkiv Vis sammendrag

  By an enclosure experiment we tested whether natal dispersing root voles Microtus oeconomus (Pallas 1776) were prevented from colonising already of habitat patches or if they were attracted to habitat patches by potential mates. The treatment consisted of manipulating the presence of animals in immigration patches, either with the presence of solitary sexuallymature male or female, whereas empty patches were used as control. Immigration patches were separated from a patch used to release a matriline (mother with her newly weaned litter) by a semipermeabel fence allowing only interpatch movements of young animals. We predicted that either a social fence would prevent immigration to treatment patches, or that potential mates would attract dispersing individuals. In particular we expected fewer dispersing males to colonise male occupied patches, and fewer dispersing females to colonise female occupied patches due to intersexual competition, ie an intrasexual social fence. We found that a higher proportion of females settled in male treatment patches than in female patc

• Andreassen, Harry Peter; Bjørnbom, Erik; Carlsen, Rine G.; Gundersen, Gry & Gundersen, Hege (1998). Visual cues as determinants of perceptual range in root voles Microtus oeconomus. Acta Theriologica. ISSN 0001-7051. 43(4), s. 371–378. Fulltekst i vitenarkiv
• Gundersen, Gry & Andreassen, Harry Peter (1998). Causes and consequences of natal dispersal in root voles, Microtus oeconomus. Animal Behaviour. ISSN 0003-3472. 56, s. 1355–1366. Fulltekst i vitenarkiv
• Andreassen, Harry P. & Gundersen, Gry (1998). Causes and consequences of natal dispersal in root voles, Microtus oeconomus. Animal Behaviour. ISSN 0003-3472. 56(6), s. 1355–1366. Fulltekst i vitenarkiv Vis sammendrag

  To test the causes and consequences of variation in natal dispersal i n root voles we released 53 matrilines (mothers with newly weaned lit ters) separately in field enclosures, during nine consecutive periods . The matrilines could disperse and distribute themselves among three pre-emptied habitat patches. Two dispersal measures were recorded: s hort-distance dispersal defined as individuals immigrating to a neigh bouring patch, and long-distance dispersal defined as unsettled indiv iduals captured along the fence of the enclosures. We analysed the ro le of social factors (i.e. maternal and litter characteristics), habi tat quality (i.e. seasonal effect) and experimentally manipulated sha pe of the natal patch in dispersal. The consequences of dispersal wer e analysed with respect to the spatial distribution of kin, and to pr egnancy in females and sexual maturation in males. Dispersal was unre lated to patch shape. In agreement with the inbreeding avoidance hypo thesis, long-distance dispersal was male biased and philopatric males were most frequently reproductively inactive. Whilst young males avo ided their mother, they seemed to disperse, settle and mature sexuall y independently of their si

• Andreassen, Harry P.; Bjørnbom, Erik; Carlsen, Rine G.; Gundersen, Gry & Gundersen, Hege (1998). Visual cues as determinants of perceptual range in root voles Microtus oeconomus. ?. 43(4), s. 371–378. Fulltekst i vitenarkiv Vis sammendrag

  We tested whether the perceptual range of male root voles Microtus oeconomus (Pallas, 1776) could be determined by visual objects in the landscape. This was done by giving single males the choice between three different sized visual cardboard patches randomly arranged around the perimeter of a circle located in agricultural fields. Effects of distance were tested by varying the diameter of the circle. The root voles were able to orient towards patches, but did not choose patches relative to their size. The ability to orient towards patches decreased with increasing distance between the release point and the patches.

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• Gundersen, Gry (2001). DEMOGRAPHIC EFFECTS OF MALE TURNOVER ON VOLE POPULATIONS. Fulltekst i vitenarkiv

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