Rodents are the most abundant and diversified order of living mammals in the world. Already since the Middle Ages we know that they can contribute to human disease, as black rats were associated with distribution of plague. However, also in modern times rodents form a threat for public health. In this review article a large number of pathogens that are directly or indirectly transmitted by rodents are described. Moreover, a simplified rodent disease model is discussed.

Rodent-borne diseases and their risks for public health

▪ Abstract Animal species have evolved different diel activity rhythms that are of adaptive value. Theory suggests that diel temporal partitioning may facilitate coexistence between competitors and between predators and prey. However, relatively few studies demonstrate a temporal shift that is predation- or competition-induced. Recorded shifts are usually within the preferred activity phase of animal species (day or night), although there are some inversions to the opposite phase cycle. Temporal partitioning is not perceived as a common mechanism of coexistence. This rarity has been variously ascribed to theoretical considerations and to the rigidity of time-keeping mechanisms, as well as to other physiological and anatomical traits that may constrain activity patterns. Our decade-long study of spiny mice of rocky deserts demonstrates that, while different factors select for activity patterns, endogenous rhythmicity may be an evolutionary constraint.

/pdf/partitioning-of-time-as-an-ecological-resource-3ix8n6icc0.pdf

Partitioning of Time as an Ecological Resource

The ecosystem engineering concept focuses on how organisms physically change the abiotic environment and how this feeds back to the biota. While the concept was formally introduced a little more than 10 years ago, the underpinning of the concept can be traced back to more than a century to the early work of Darwin. The formal application of the idea is yielding new insights into the role of species in ecosystems and many other areas of basic and applied ecology. Here we focus on how temporal, spatial and organizational scales usefully inform the roles played by ecosystem engineers and their incorporation into broader ecological contexts. Two particular, distinguishing features of ecosystem engineers are that they affect the physical space in which other species live and their direct effects can last longer than the lifetime of the organism – engineering can in essence outlive the engineer. Together, these factors identify critical considerations that need to be included in models, experimental and observational work. The ecosystem engineering concept holds particular promise in the area of ecological applications, where influence over abiotic variables and their consequent effects on biotic communities may facilitate ecological restoration and counterbalance anthropogenic influences.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1461-0248.2006.00997.x

Ecosystem engineering in space and time.

We experimented on how illumination, habitat structure, and three different species of owls affected the foraging behavior of Gerbillus allenbyi and G. pyramidum, two gerbil species that coexist on sand dune habitats in the Negev Desert, Israel. We also tested how illumination and habitat structure affected rates of predation by owls on the two gerbil species. In a large aviary, we manipulated presence and absence of owls, owl species, presence and absence of illumination, and shrub cover. In response to the presence of owls or to increased illumination, gerbils foraged less, shifted foraging activity to the bush microhabitat, and quit patches at a higher giving-up density of resources. In accord with moonlight avoidance, both gerbil species suffered higher predation rates under illumination than in the absence of illumination. In addition, G. pyramidum distinguished among owl species, as indicated by changes in patch use and habitat selection. Habitat structure also affected foraging behavior and rates of predation. Gerbils foraged less in the open than in the bush microhabitat, foraged less when there was no cover present, and foraged less in the bush microhabitat when patches were encumbered by entangling branches. In accord with avoidance of open areas, both gerbil species suffered higher rates of predation when shrub cover was 0% than when shrub cover was 10%. With 0% cover, G. allenbyi suffered higher predation rates than G. pyramidum, but with 10% cover, rates of owl predation did not differ between gerbil species. Rates of owl predation on the two species corresponded to their natural patterns of macro- and microhabitat partitioning; relative to G. allenbyi, G. pyramidum predominates on open sand dunes and biases its behavior toward the open microhabitat. The results suggest that predation interacts with resource competition to determine the distribution and habitat separation of G. allenbyi and G. pyramidum.

Factors Affecting Gerbil Foraging Behavior and Rates of Owl Predation

The Negev. The Challenge of a Desert

We tested the hypothesis that diversity and productivity of herbaceous plant communities in disturbed soil are related to the physical and biological heterogeneity of the landscape. Our study was carried out on vegetation responses in porcupine diggings on a rocky slope in the central Negev desert in Israel. We measured aboveground biomass and plant density per species in 150 porcupine diggings (15 cm deep and 15 to 20 cm wide) and in equally sized adjacent control samples in the undisturbed soil matrix. We calculated mean annual biomass production, plant density and species richness for 10 sample areas along the slope. In addition, we divided the plants into groups according to propagule size and dispersal mode. We denoted two types of landscape heterogeneity, which we called physical and biological patchiness. Physical patchiness was measured as the ratio of bare rock to soil surface. Biological patchiness was the area of the soil covered by shrubs with associated soil mound and under-story relative to the total soil surface. We also measured disturbance density, as the long term (17 yr) average density of newly made porcupine diggings. We found that 1) the physical patchiness explained 30% of the variation of biological patchiness along the slope, while 2) the pattems of disturbance intensity and biological patchiness were similar (R 2 =0.386). 3) Biomass, density and species richness were significantly higher in diggings than in the soil matrix. 4) Plant density in the matrix, but not in the diggings, was significantly correlated with physical patchiness, 5) species richness in diggings was significantly correlated with biological patchiness, but 6) biomass production in diggings and matrix was not affected by either physical or biological patchiness of the landscape. 7) Disturbance density did not affect vegetation responses in diggings and matrix. 8) A shift in the plant communities in the matrix towards plants with smaller seeds was associated with increasing physical patchiness, while in diggings there was an opposite shift. 9) The proportion of wind dispersers was higher in diggings than outside, while the proportion of runoff dispersers was lower, 10) the densities of runoff dispersers in diggings and matrix were positively correlated with physical and biological patchiness. 11) Physical and biological patchiness formed the two major gradients of species composition, explaining 30 and 25% respectively. We conclude that the network of physical and biological patchiness and soil disturbance are important in the redistribution of resources and seeds, which control plant biomass, density, species richness and diversity. The bare rock surface is the main source for runoff flow with associated soil, organic matter and nutrients. The understory vegetation of shrubs provides seeds for creating and maintaining diversity. The soil matrix absorbs runoff flow, and disturbances absorb runoff and trap seeds. Thus, differences in landscape heterogeneity and their effects on resource and seed movement interact in controlling plant community productivity and diversity in the landscape.

Patchiness and disturbance: plant community responses to porcupine diggings in the central Negev

L'etude porte sur six especes appartenant aux genres Gerbillus et Acomys et vivant dans des sites sableux ou rocheux. Comparaison de deux methodes permettant d'etudier le choix de l'habitat (methode de regression et methode de repartition)

Habitat selection of Israel desert rodents: comparison of a traditional and a new method of analysis

Recensement des populations d'une guilde de Gerbillus du sud d'Israel et mesure simultanee d'une serie de 22 variables de l'habitat pour tester la methode de Pimm-Schoener de mesure des coefficients d'interactions au niveau de l'espece. L'heterogeneite de l'habitat est le principal probleme a considerer et necessite des modifications de la methode

Estimating species interactions in heterogeneous environments

In the Negev Desert, Israel, the Indian crested porcupine, Hystrix indica, digs similar sized, discrete, elongated pits (257±21.3 cm3; n=144) while foraging for below-ground plant storage organs. In these digs, soil moisture content is higher than in the surrounding soil matrix. The digs disturb population and community structure due to porcupine consumption or damage of 18 species of plants, and repopulation by 55 plant species. Over the past 14 years we have studied dig dynamics on a rocky hillslope with three distinct habitats as regards soil moisture content. Midslope soil moisture is the highest, decreasing towards upper and lower slope. We have counted a total of 6,609 digs in the area: 2141 on the upper, 3211 in the middle and 1257 on the lower part of the slope. The number of digs at midslope is significantly higher than on the other parts of the slope (ANOVA; P<0.0001). There is a significant (P<0.05) correlation between the mean number of porcupine digs and the cumulative rainfall amount for the 2 years prior to dig formation. To study plant repopulation in digs, all plants in 144 digs along the slope and from equal sized plots in the undistarbed soil matrix were collected. In all, 288 samples with 20 584 plants were collected, 2042 from the matrix and 18,542 from digs. Of the 55 species, we focused on the abundance patterns of Filago desertorum, Picris cyanocarpa and Bromus rubens, which made up 69.5% of all the individuals in the digs and 68.3% in the matrix. Our results showed that all three species increased in abundance in the digs as compared to the matrix. F. desertorum density increased by a factor of 2.9, P. cyanocarpa by 9.5 and B. rubens by 12.0. There were species-specific responses in abundance to the location of the digs along the moisture gradient. The only species whose abundance responded to the moisture gradient was F. desertorum. P. cyanocarpa demonstrated peak abundance in the location with the poorest moisture regime, while B. rubens showed peak abundance at the intermediate part of the moisture gradient. We suggest a scheme for integrating the increase in density and the species-specific responses to the digs along a water gradient based on R.H. Whittaker's view of individual species abundances along an environmental gradient.

Porcupine disturbances and vegetation pattern along a resource gradient in a desert

We examine the role of the sit and wait foraging strategy and of the stability and predictability of the biotic environment in shaping population biology and life history traits of the desert scorpion, Scorpio maurus palmatus. The study was carried out in a loessial plain in the Negev desert, Israel. We used a grid system (5x80 m) within the Hammada scoparia plant association. The area was divided into 1,600 squares (50x50 cm) and the presence (within ±5 cm) and width of each scorpion burrow was recorded for eight years (1973–1980). It was found that: (1) Dispersal is a common phenomenon for all S. maurus palmatus age groups and takes place only after a heavy rainfall when soil moisture is high. (2) Dispersion patterns change from clumped to random as a function of age. (3) Dispersal is age specific and density dependent. (4) During the dry seasons a high percentage of the population goes into the resting stage. In order to integrate the above findings, a graphical model was constructed with the main assumption that the S. maurus palmatus prey availability relationship is a decreasing function between the scorpion burrow and its food resources. Data and model analysis led to the conclusion that the desert scorpion, S. maurus palmatus, is confronted with a relatively predictable physical environmeent and unpredictable biological environment. Two alternative strategies are available for S. maurus palmatus to overcome prey unpredictability; dispersal during the rainy season and inactivity during the dry seasons. We suggest that many other burrowing desert animals may face the problem of unpredictability of biological resources. Thus it seems that the S. maurus palmatus biological relationship model can be applied, with modifications, to a wide spectrum of desert burrowing animals.

The relationship between sit and wait foraging strategy and dispersal in the desert scorpion, Scorpio maurus palmatus.

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