No abstract

Some rodents gather and store seeds. How many seeds they gather and how they treat those seeds is largely determined by seed traits such as mass, nutrient content, hardness of the seed coat, presence of secondary compounds, and germination schedule. Through their consumption and dispersal of seeds, rodents act as agents of natural selection on seed traits, and those traits influence how rodents forage. Many seeds that are scatter hoarded by rodents are pilfered, or stolen, by other rodents, and seed traits also likely influence pilfering rates and seed fates of pilfered seeds. To clarify coevolutionary relationships between rodents and the plants that they disperse, one needs to understand the role of seed traits in rodent foraging decisions. We compared how the seeds of four species of plants that are dispersed by scatter-hoarding animals and that differ in value (singleleaf piñon pine, Pinus monophylla; desert peach, Prunus andersonii; antelope bitterbrush, Purshia tridentata; Utah juniper, Juniperus osteosperma) were pilfered and recached by rodents. One hundred artificial caches of the four seed species (25 per species) were prepared, and removal by rodents was monitored. Rodents pilfered high value seeds more rapidly than the other seeds. Desert peach seeds, which contain toxic secondary compounds, were more frequently recached. Relatively low value seeds like Utah juniper and antelope bitterbrush were pilfered more slowly, were sometimes left at cache sites, and seeds of the latter species were transported shorter distances to new cache sites. The background density of seeds also appeared to influence the relative value of seeds. This article is protected by copyright. All rights reserved.

No abstract

In extensive experiments during a period of 5 years we could prove that 1. the population density could not be substantially influenced by a massive and continuous mass trapping with pheromone baited traps neither of Ips ty ographus nor of Trypodendron lineatum; 2. the protection of an object by this method is in case o f t h e first-named insect possible but against the second one not; 3. the number of bark beetles on a given place is not exclusively decisive for the attack of trees; the monitoring in a certain time and the forecast based on this date have therefore a vague character; 4. there is a good correlation between the manner of forest management on the one hand and the PO ulation density of bark beetles or the number of attacked trees, respectively, on the other: the soc d e d clean-mana ement is the best, probably the most reliable and at long sight also the most reasonable methofi against the propagation and the attack of the bark beetles. MethodsIt has been proved that a great number of bark beetles can be captured by use of the three pheromonecompounds (PHEROPRAX, CHALCOPRAX and LINOPRAX) and of suitable traps (particularly the so-called three-trap-star). This fact seemed to demonstrate the applicability of the method for monitoring and prognosisi. e. we can obtain reliable dates about the begin of beetle-flight and about the aproximate density of beetle-population.

No abstract