Differentiation Of Food Hoarding Behavior And Microhabitat Selection Between Niviventer Confucianus And Apodemus Peninsulae:Implication To Coexistence

Niche differentiation is one of the important reasons for species coexistence in sympatric animals.Chinese white-bellied rats(Niviventer confucianus CWR)and Korean field mice(Apodemus peninsulae KFM)are dominant rodent species that share similar habitat(e.g.,shrub,abandoned farmland and secondary forests),diet(e.g.,plant seeds)and rhythm(nocturnal)in Donglingshan area,western Beijing city,China.They eat and hoard seeds of the common local trees(e.g.,Armeniaca sibirica),and therefore have important effects on plant regeneration and structure.However,the mechanism of their coexistence is unclear.In this study,niche differentiations of behavior of seed hoarding,pilferage,pilferage avoidance and microhabitat selection between the CWR and KFM were tested both under the semi-natural conditions and in the field.I wanted to argue that the differentiations of food hoarding behavior and microhabitat selection of the two rodent species contribute to their coexistence.Under the semi-naturals enclosure conditions(9.0 x 9.0 m enclosures),pairwised individuals of CWR and KFM were tracked using infrared camera when they competed for plant seeds(A.sibirica)for eating,hoarding and subsequently pilfering.The purpose of this experiment was to explore the following questions:(1)Do CWR and KFM adopt different patterns of hoarding(scatter hoarding vs.larder hoarding)?(2)Do CWR and KFM pilfer caches each other?(3)Do CWR and KFM have different behavioral responses to interspecific pilferage?And(4)from the point view of relative energy consumption(total calorie of consumed seeds/body mass of animal)and energy gaining(total calorie of gained seeds/body mass of animal),can CWR and KFM achieve balanced budges that meets the needs for survival under the conditions of inter-pilferage.The results showed that(1)CWR primarily hoarded seeds in larder(in the nests),whereas KMF hoarded seeds both in larder and in scatter.(2)Asymmetrical cache pilferage exhibited between CWR and KFM,in which CWR could pilfer(13.6 ± 2.2%,Mean ± SE,n=15)caches from KFM,but the converse is(10.3±2.6%).Ultimately,seed loss of CWR(4.9 ± 1.2%)could be compensatd by pilfering from KFM(13.6 ±2.2%)and/or harvesting from the seed source(64.2 ± 3.6%),wherease,seed loss of KFM by pilferage(25.6±4.1%)could not be compensated by pilfering from CWR(10.3 ±2.6%)and/or harvesting from the seed source(47.9±4.5%).This result implies that CWR had distinct advantages over KFM within the asymmetrical interaction of food sharing and pilferage,and derives the interested questions of their coexistence.(3)KFM increased the proportion of scatter-hoarding,eating,harvested from the seeds source,and hoarded more seeds in the low pilferage risk areas when they faced the pressures of CWR pilferage,wherease CWR increased the proportion of larder-hoarding in the presence of KFM pilferage.(4)The proportion of total seeds finally occupied(78.9 ± 2.5%,proportion of seed number)and seeds finally relative occupied(0.4±0.01,seed number/body mass)of CRW were significantly higher than those of KFM(21.1±2.5%,proportion of seed number;0.3± 0.01,seed number/body mass).However,in terms of energy consumption,significant differences were not found in relative daily energy consumption(CWR:0.917±0.074 KJ;KFM:0.599±0.074 KJ)and relative daily energy distribution(CWR:1.197 ± 0.095 KJ;KFM:1.013 ± 0.096 KJ)between the two rodent species.This result suggests that the energy gaining of KFM could meet the needs of survival under the higher risk of pilferage,promoting its coexistence with C WR.In order to explore the microhabitat selection differentiation.we studied microhabitat selection of CWR and KFM in different habitats and seasons during May to October in 2016 and 2017.The results show that,(1)in shrub,in spring,CWR preferred to habit in places with higher arbor density,higher herb coverage and relatively lower litter coverage,while KFM selected higher diameter at breast height(DBH)and litter coverage,but lower herb coverage microhabitats.The principal component analysis showed that surface cover was the key factor affecting microhabitats choice of the two species.In shrub,in autumn,CWR preferred to select microhabitats with more arbor species,higher shrub density and herb coverage microhabitats,while KFM preferred for microhabitats with larger DBH,longer shrub distances,higher ratio of open field and litter coverage.Food abundance was the key factor in determining the microhabitats selection of them.(2)In abandoned farmland,in spring,CWR selected microhabitats with higher shrub density and herb coverage,whereas KFM preferred to select higher canopy coverage,DBH and litter coverage,but lower herb coverage microhabitats.Surface cover was the key factor that affected the microhabitats choice of them.In abandoned farmland,in autumn,CWR preferred microhabitats with relatively low canopy coverage and litter coverage,while KFM's selection was on the opposite.Food abundance was the main factor that determined their microhabitats selection.(3)In secondary forests,in autumn,CWR preferred to select microhabitats with higher shrub density,shrub base diameter and herb coverage,while KFM liked microhabitats with higher DBH and litter coverage,but lower shrub density and herb coverage.Surface cover was the key factor that influenced the microhabitats selection of them.The case in spring in secondary forest was not analyzed due to the small sample size.In summary,the results showed that coexistence between CWR and KFM might be achieved by differentiations of hoarding and pilferage behavior,energy allocation and utilization,and microhabitat selection.Although these results need further studies in multiple species and systems in the natural conditions,they may also be reference in exploring coexistence mechanism among sympatric animals.