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By Tom Wassmer Assistant Professor of Biology at Siena Heights University in Adrian, Michigan
Erik Stokstad
No abstract text is available yet for this article.
June 10, 2016: Science
Andrew G Hope, Jason L Malaney, Kayce C Bell, Fernando Salazar-Miralles, Andreas S Chavez, Brian R Barber, Joseph A Cook
Integration of molecular methods, ecological modeling, and statistical hypothesis testing are increasing our understanding of differentiation within species and phylogenetic relationships among species by revealing environmental connections to evolutionary processes. Within mammals, novel diversity is being discovered and characterized as more complete geographic sampling is coupled with newer multi-disciplinary approaches. North American red squirrels exemplify a forest obligate genus whose species are monitored as indicators of forest ecosystem condition, yet phylogenetic relationships reflecting evolutionary history within this genus remain tentative...
July 2016: Molecular Phylogenetics and Evolution
Erin E Posthumus, John L Koprowski, Robert J Steidl
Some animals modify the environment in ways that can influence the resources available to other species. Because red squirrels (Tamiasciurus hudsonicus) create large piles of conifer-cone debris (middens) in which they store cones, squirrels concentrate resources that might affect biodiversity locally. To determine whether other animals are attracted to midden sites beyond their affinity for the same resources that attract red squirrels, we assessed associations between middens, mammals, and birds at population and community levels...
2015: PloS One
J E Lane, A G McAdam, A Charmantier, M M Humphries, D W Coltman, Q Fletcher, J C Gorrell, S Boutin
Most empirical attempts to explain the evolution of parental care have focused on its costs and benefits (i.e. fitness consequences). In contrast, few investigations have been made of the other necessary prerequisite for evolutionary change, inheritance. Here, we examine the fitness consequences and heritability (h(2)) of a post-weaning parental care behaviour (territory bequeathal) in a wild population of North American red squirrels. Each year, a subset (average across all years = 19%) of reproductive females bequeathed their territory to a dependent offspring...
June 2015: Journal of Evolutionary Biology
Michael A Steele, Ghislain Rompré, Jeffrey A Stratford, Hongmao Zhang, Matthew Suchocki, Shealyn Marino
Scatterhoarding rodents often place caches in the open where pilferage rates are reduced, suggesting that they tradeoff higher risks of predation for more secure cache sites. We tested this hypothesis in two study systems by measuring predation risks inferred from measures of giving-up densities (GUDs) at known cache sites and other sites for comparison. Rodent GUDs were measured with small trays containing 3 L of fine sand mixed with sunflower seeds. In the first experiment, we relied on a 2-year seed dispersal study in a natural forest to identify caches of eastern gray squirrels (Sciurus carolinensis) and then measured GUDs at: (i) these caches; (ii) comparable points along logs and rocks where rodent activity was assumed highest; and (iii) a set of random points...
May 2015: Integrative Zoology
Miriam L Zelditch, Jingchun Li, Lucy A P Tran, Donald L Swiderski
Several theories predict that rapidly diversifying clades will also rapidly diverge phenotypically; yet, there are also reasons for suspecting that diversification and divergence might not be correlated. In the widely distributed squirrel clade (Sciuridae), we test for correlations between per lineage speciation rates, species richness, disparity, and a time-invariant measure of disparity that allows for comparing rates when evolutionary modes differ, as they do in squirrels. We find that species richness and speciation rates are not correlated with clade age or with each other...
May 2015: Evolution; International Journal of Organic Evolution
Chris T Tromborg, Richard G Coss
This study of California ground squirrels (Otospermophilus beecheyi) investigated the long-term effects of isolation rearing on alarm-call recognition. Six wild-caught squirrels, trapped as yearlings, and six laboratory-reared squirrels were maintained in solitary cages for approximately 3 years prior to the study. Visual searching and olfactory searching were measured as squirrels emerged from their burrow-like nest box into a laboratory room after hearing repetitive playbacks of alarm calls or control sounds consisting of pulses of white-noise or ambient laboratory sounds...
July 2015: Animal Cognition
Nuria Polo-Cavia, Zoraida Vázquez, Francisco Javier de Miguel
Asymmetry in motor patterns is present in a wide variety of animals. Many lateralized behaviors seem to depend on brain asymmetry, as it is the case of different tasks associated to food handling by several bird and mammal species. Here, we analyzed asymmetry in handling behavior of pine cones by red squirrels (Sciurus vulgaris). Red squirrels devote most of their daily activity to feeding, thus this species constitutes an appropriate model for studying asymmetry in food processing. We aimed to explore 1) the potential lateralization in handling of pine cones by squirrels, 2) the dominant pattern for this behavior (left- vs...
2015: PloS One
T P Semenova, L A Spiridonova, N M Zakharova
The seasonal peculiarities of the circadian activity of hibernator, Yakutian long tail ground squirrels (S. undulatus) (n = 35) and non hibernator, Wistar rats (n = 35), were studied. The locomotor activity was registered in each subject individually during 5-17 days by means of "Animex" in the different periods of annual cycle. It was shown that ground squirrels were animals with daily type of activity. On the contrary, the Wistar rats demonstrated nocturne type of locomotors activity. The active period in rats was longer than in ground squirrels...
September 2014: Rossiĭskii Fiziologicheskiĭ Zhurnal Imeni I.M. Sechenova
R W Taylor, S Boutin, M M Humphries, A G McAdam
Temporal variation in selection has long been proposed as a mechanism by which genetic variation could be maintained despite short-term strong directional selection and has been invoked to explain the maintenance of consistent individual differences in behaviour. We tested the hypothesis that ecological changes through time lead to fluctuating selection, which could promote the maintenance of variation in female behavioural traits in a wild population of North American red squirrels. As predicted, linear selection gradients on female aggression and activity significantly fluctuated across years depending on the level of competition among juveniles for vacant territories...
November 2014: Journal of Evolutionary Biology
Emily K Studd, Stan Boutin, Andrew G McAdam, Charles J Krebs, Murray M Humphries
Neonatal reproductive failure should occur when energetic costs of parental investment outweigh fitness benefits. However, little is known about the drivers of neonatal reproductive failure in free-ranging species experiencing continuous natural variation in predator abundance and in the energetic and fitness costs and benefits associated with parental investment. Long-term comprehensive studies are required to better understand how biotic, abiotic and life-history conditions interact to drive occurrences of reproductive failure in the wild...
January 2015: Journal of Animal Ecology
Célia Rézouki, Anne Dozières, Christie Le Cœur, Sophie Thibault, Benoît Pisanu, Jean-Louis Chapuis, Emmanuelle Baudry
Whether urban parks can maintain viable and self-sustaining populations over the long term is questionable. In highly urbanized landscapes, urban parks could play a role in biodiversity conservation by providing habitat and resources to native species. However, populations inhabiting urban parks are usually small and isolated, leading to increased demographic stochasticity and genetic drift, with expected negative consequences on their viability. Here, we investigated a European red squirrel population located in an urban park close to Paris, France (Parc de Sceaux; 184 ha) to assess its viability...
2014: PloS One
G H Jacobs, D G Birch, B Blakeslee
The visual sensitivity of tree squirrels from three different species (two western gray squirrels, Sciurus griseus; three fox squirrels, Sciurus niger; and an eastern gray squirrel, Sciurus carolinensis) was measured for spatial patterns defined by luminance differences. Spatial contrast sensitivity functions were determined in behavioral discrimination experiments in which the stimuli were sinusoidally-modulated gratings. At an average luminance level of 3.4 cd/m(2) these squirrels were maximally sensitive to spatial frequencies of about 0...
December 1982: Behavioural Processes
S Benhamou
This study deals with the movements of two American red squirrels (Tamiasciurus hudsonicus) in their home ranges from late spring to early autumn in a deciduous-coniferous forest in Québec. During 70 six-hour tracking sessions, the type of behaviour exhibited at any place, and its terrestrial or arboreal occurrence, were recorded. Spatio-temporal structure of the squirrels' home ranges were analysed in relation to vegetation type and food availability. Although American red squirrels are known to be mainly adapted to coniferous forests, they also exploit deciduous areas when these areas become productive...
September 1996: Behavioural Processes
J Prescott
The ontogenetic development of vocal communication was studied in 23 young red squirrels (Tamiasciurus hudsonicus) from four litters born in captivity. The age of appearance and sonogram analysis of the young's vocalizations are presented. In the newborn, discomfort and distress calls are the first vocalizations to appear. With the development of hearing, differentiation of distress and threat calls is noted and a contact call commences. Various alarm and threat calls occur when the young make their first appearance outside the nest...
December 1979: Behavioural Processes
Patricia J DeCoursey
Laboratory and field data relevant to the survival value of the suprachiasmatic nuclei (SCN) pacemaker are presented for 4 related North American squirrel species that evolved in habitats with markedly different environmental conditions. Laboratory studies used free-running activity rhythms under constant conditions as the signature of an endogenous pacemaker. Field studies documented the circadian ecology of the 4 species; survival of intact controls was compared, when possible, with an SCN-lesioned group of free-living animals or with wild-caught animals in a laboratory facility that simulated natural conditions...
June 2014: Behavioral Neuroscience
Mingming Zhang, Zhong Dong, Xianfeng Yi, Andrew W Bartlow
Several squirrel species excise the embryo of acorns of most white oak species to arrest germination for long-term storage. However, it is not clear how these acorns counter embryo excision and survive in the arms race of coevolution. In this study, we simulated the embryo excision behavior of squirrels by removing 4 mm of cotyledon from the apical end of white oak acorns differing in embryo depths to investigate the effects of embryo excision on acorn germination and seedling performance of white oak species...
January 2014: Ecology and Evolution
Andreas S Chavez, Sean P Maher, Brian S Arbogast, G J Kenagy
Pleistocene climate cycles and glaciations had profound impacts on taxon diversification in the Boreal Forest Biome. Using population genetic analyses with multilocus data, we examined diversification, isolation, and hybridization in two sibling species of tree squirrels (Tamiasciurus douglasii and Tamiasciurus hudsonicus) with special attention to the geographically and genetically enigmatic population of T. hudsonicus on Vancouver Island, Canada. The two species differentiated only about 500,000 years ago, in the Late Pleistocene...
April 2014: Evolution; International Journal of Organic Evolution
Cory T Williams, Jeffrey E Lane, Murray M Humphries, Andrew G McAdam, Stan Boutin
The production of offspring by vertebrates is often timed to coincide with the annual peak in resource availability. However, capital breeders can extend the energetic benefits of a resource pulse by storing food or fat, thus relaxing the need for synchrony between energy supply and demand. Food-hoarding red squirrels (Tamiasciurus hudsonicus) breeding in the boreal forest are reliant on cones from a masting conifer for their nutrition, yet lactation is typically completed before the annual crop of cones is available for consumption such that peaks in energy supply and demand are not synchronized...
March 2014: Oecologia
Claire D Stevenson, Mark Ferryman, Owen T Nevin, Andrew D Ramsey, Sallie Bailey, Kevin Watts
In Britain, the population of native red squirrels Sciurus vulgaris has suffered population declines and local extinctions. Interspecific resource competition and disease spread by the invasive gray squirrel Sciurus carolinensis are the main factors behind the decline. Gray squirrels have adapted to the British landscape so efficiently that they are widely distributed. Knowledge on how gray squirrels are using the landscape matrix and being able to predict their movements will aid management. This study is the first to use global positioning system (GPS) collars on wild gray squirrels to accurately record movements and land cover use within the landscape matrix...
July 2013: Ecology and Evolution
2015-01-01 07:09:20
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