Emigration behavior of Clark's Nutcracker

Journal ArticleEruptive movements of the Clark's Nutcracker (Nucifraga columbiana) were observed during the late summer and fall of 1977, 1978 and 1979 in northern Utah and adjacent states. Over 2,000 emigrating nutcrackers were seen during these periods. Eruptions began in mid to late August, about the time nutcrackers began foraging on developing conifer cones, and continued until early October. Nearly all nutcrackers traveled in small, loose flocks (x = 10.1 individuals). During 1977-1978, most emigrating nutcrackers appeared to winter in p&on-juniper woodlands of Utah and adjacent states and no nutcrackers were reported outside their normal breeding range. A northward movement of nutcrackers, presumably the same population observed emigrating southward in fall 1977, was noted in summer 1978. Evidence for breeding of nutcrackers on their wintering areas is presented. A compartmental model summarizes current knowledge on the temporal and spatial aspects of nutcracker emigration

The Mismatch in Distributions of Vertebrates and the Plants that they Disperse

© 2018 The Authors Little is known about how mutualistic interactions affect the distribution of species richness on broad geographic scales. Because mutualism positively affects the fitness of all species involved in the interaction, one hypothesis is that the richness of species involved should be positively correlated across their range, especially for obligate relationships. Alternatively, if mutualisms involve multiple mutualistic partners, the distribution of mutualists should not necessarily be related, and patterns in species distributions might be more strongly correlated with environmental factors. In this study, we compared the distributions of plants and vertebrate animals involved in seed-dispersal mutualisms across the United States and Canada. We compiled geographic distributions of plants dispersed by frugivores and scatter-hoarding animals, and compared their distribution of richness to the distribution in disperser richness. We found that the distribution of animal dispersers shows a negative relationship to the distribution of the plants that they disperse, and this is true whether the plants dispersed by frugivores or scatter-hoarders are considered separately or combined. In fact, the mismatch in species richness between plants and the animals that disperse their seeds is dramatic, with plants species richness greatest in the in the eastern United States and the animal species richness greatest in the southwest United States. Environmental factors were corelated with the difference in the distribution of plants and their animal mutualists and likely are more important in the distribution of both plants and animals. This study is the first to describe the broad-scale distribution of seed-dispersing vertebrates and compare the distributions to the plants they disperse. With these data, we can now identify locations that warrant further study to understand the factors that influence the distribution of the plants and animals involved in these mutualisms

Effects of Rodent Abundance and Richness on Cache Pilfering

© 2018 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd Scatterhoarding is a common behavioral strategy to conserve food during periods of scarcity, but this type of food storage is vulnerable to theft or pilferage. A variety of environmental factors and cache characteristics influence the rate of pilferage. Here we investigate 2 environmental factors, which heretofore have not received much attention: the abundance and species richness of scatterhoarding animals in the vicinity of scatterhoarded seeds. We measured the rate of cache pilferage at 7 sites that differed in the number and species composition of granivorous rodents in western Nevada using local native seeds and sunflower seeds. We found that there was no difference between the pilferage rate of native seeds and sunflower seeds, but that sites with different rodent abundances had different pilferage rates. Pilferage rates were proportional to the abundance of scatterhoarding rodents. Scatterhoarding rodents removed seeds at the rate of 1.3%/day/rodent individual. Species richness of scatterhoarding rodents was not correlated with rates of pilferage. These results suggest that density-dependent competition for scatterhoarded seeds is a strong determinant of pilferage rates

Substrate type affects caching and pilferage of pine seeds by chipmunks

The abiotic environment often influences the ways in which animals interact. By affecting the cues associated with buried seeds, the type of substrate used by seed-caching rodents may alter the relative probabilities of cache pilferage and cache retrieval. We predicted that, after a wildfire, the presence of ash would impair rodents' ability to smell pine seeds on the forest floor. In a laboratory experiment, we compared the foraging success, caching frequency, and cache recovery of chipmunks (six Tamias amoenus and six T. quadrimaculatus) in ash versus sand substrates. Initial results supported our hypothesis: chipmunks found only 2.3% of 108 caches of Jeffrey pine (Pinus jeffreyi) seeds that we buried in ash but found 98% of caches in sand. However, chipmunks made as many or more of their own caches in ash compared with sand (48% for T. amoenus, 73% for T. quadrimaculatus.) When foraging for seeds cached in ash by themselves and by other individuals, they found significantly higher proportions of their own caches (62%) than of caches made by others (25%). However, when foraging in sand, they found high proportions both of their own caches and those of others (86 versus 81%). These results suggest that olfaction is less effective in ash than in sand, that spatial memory enables chipmunks to recover their own caches in ash, and that caching in ash may allow animals to avoid pilferage of stored food. As chipmunks are important dispersers of seeds, changes in their foraging patterns or competitive interactions after fire could significantly affect pine regeneration. Copyright 2004.ash; caching; chipmunks; foraging; Jeffrey pine; olfaction; pilferage; Pinus jeffreyi; spatial memory; scatter hoarding; Tamias

CHEEK POUCH CAPACITIES AND LOADING RATES OF DEER MICE (PEROMYSCUS MANICULATUS)

Volume: 59Start Page: 278End Page: 28

Reciprocal pilfering in a seed-caching rodent community: implications for species coexistence

© 2017, Springer-Verlag GmbH Germany. Abstract: Cache pilfering rates have been reported to be unsustainably high in many seed-caching rodent communities, but the dynamics of pilfering is largely unknown at the community level. In this study, we examined rates of seed-cache pilfering in a species-rich community of granivorous rodents in pair-wise trials. We compared the ability of each species to pilfer from conspecifics as well as heterospecifics to determine if pilfering is symmetrical or asymmetrical in the community. During the study, pilfering was more or less symmetrical among three scatter-hoarding species of rodents, averaging 28% (SD = 26%) of caches pilfered in 24 h, while the lone larder-hoarding species was unable to pilfer and experienced cache loss at the rate of 16 ± 14% of caches in 24 h to the other species. Pilfering was reciprocal among the scatter-hoarding species among conspecifics and heterospecifics despite differences in caching behavior (cache depth, size, and location). These finding support the hypothesis of reciprocal pilfering and are consistent with theories of the coexistence of ecologically similar species by lessening the effects of competition among species at the resource level and demonstrate that species with a pilfering disadvantage may need to exhibit different caching behaviors (e.g., larder-hoarding) to prevent competitive exclusion. Significance statement: Many rodents scatter-hoard seeds to survive periods when other food is scarce. Because these caches are usually undefended, individuals may experience significant theft of seeds. We reasoned that individuals that scatter-hoard seeds extensively are likely to have many of their caches pilfered, and that to counteract this loss, they should also be very effective pilferers of other animal’s caches. Conversely, animals that seldom scatter-hoard seeds are likely to be poor pilferers. This suggests that the ability to pilfer is part of the adaptive strategy of scatter-hoarding animals and that the more they scatter-hoard, the more they pilfer. Individuals that are unable to replace lost caches may not survive periods of food scarcity. There should be intense competition for stored seeds within communities of scatter-hoarding rodents, and this competition is manifested not only at the time of seed harvest but also as pilferage of cached seeds. In such communities, we expect pilferage to be reciprocal, or nearly equal among scatter-hoarding species, and thereby contribute to coexistence