Glaucomys Volans Research Articles

Texas Ratsnake Predation on Southern Flying Squirrels in Red-Cockaded Woodpecker Cavities

Texas Ratsnake Predation on Southern Flying Squirrels in Red-Cockaded Woodpecker Cavities

EVIDENCE OF POSITIVE INDIRECT EFFECTS WITHIN A COMMUNITY OF CAVITY-NESTING VERTEBRATES

Abstract In a community of ≥3 competing species, one species may also have a positive indirect effect on another by suppressing a third, shared competitor. We examine the potential for similar interactions among Red-cockaded Woodpeckers (Picoides borealis) and two of its cavity kleptoparasites: southern flying squirrels (Glaucomys volans) and Red-bellied Woodpeckers (Melanerpes carolinus). We hypothesized that flying squirrels have a positive indirect effect on Red-cockaded Woodpeckers by suppressing Red-bellied Woodpeckers. We monitored occupancy of Red-cockaded Woodpecker cavities on 16 territories for one year, and then regularly removed flying squirrels from Red-cockaded Woodpecker cavities for one year on eight territories, each paired with a control. We predicted that flying squirrel removal would competitively release Red-bellied Woodpeckers, which in turn would preempt a positive occupancy response by Red-cockaded Woodpeckers. During the removal phase, flying squirrel occupancy decreased 53% on th...

Kinematics of turning maneuvers in the southern flying squirrel,Glaucomys volans

The ability to change direction is essential to any animal that moves around in a complex, 3D environment. In this study we present the first 3D description of body positions during gliding turns in a mammalian gliding specialist, the southern flying squirrel, Glaucomys volans. In addition, we used these kinematic data to estimate the aerodynamic forces generated by the animals and rotational velocities and accelerations of the body while turning. These results were compared with similar measurements of flying squirrels during straight glides. The two individuals used in this study differed significantly in limb position asymmetries between the two sides of their bodies and also were significantly different in measures of turning performance. The individual with better performance used limb positions consistent with a primarily lift-based turning mechanism (banked turn), whereas the individual with poorer performance used limb positions consistent with a primarily drag-based turning mechanism (crabbed turn). Both individuals employed limb movements continuously through the gliding turn, but these movements did not have any consistent relationships with body rotations or lateral acceleration. As compared with straight glides, squirrels used significantly higher angles of attack and had lower lift-to-drag ratios, but did not differ in glide angle. Contrary to the typical view of maneuvering during gliding as a simple, static form of locomotion, the results presented here indicate that mammalian gliding is a complex behavior comprising the interplay of many components of limb position and wing shape that affect the balance of forces that control the turn.

Cavity Number and Use by Other Species as Correlates of Group Size in Red-Cockaded Woodpeckers

I examined cavity number and use by other species as correlates of Red-cockaded Woodpecker (Picoides borealis) group size at Camp Blanding Training Site (CBTS) and Goethe State Forest (GSF), Florida. Group size was positively correlated with cavity number at CBTS but not at GSF. Other species occupied 1.75 (34%) and 1.19 (27%) cavities/territory at CBTS and GSF, respectively. Statistically controlling for use by other species yielded significant positive correlations between group size and cavity number in 4 of 5 years at CBTS and 2 of 4 years at GSF. Correlations between group size and total use by other species, controlling cavity number, were significantly negative at both sites. Separating total use by species, group size was negatively correlated only with southern flying squirrels (Glaucomys volans) at CBTS and only with Red-bellied Woodpeckers (Melanerpes carolinus) at GSF, as flying squirrels occupied >3 times more cavities/territory at CBTS than at GSF (0.87 vs. 0.28) while Red-bellied Woodpeckers occupied ∼0.75 cavities/territory at both sites. Flying squirrels may obscure the relationship between the two woodpecker species by limiting their cavity use.

A NEW RHABDITOID NEMATODE SPECIES IN ASIAN SCIURIDS, DISTINCT FROM STRONGYLOIDES ROBUSTUS IN NORTH AMERICAN SCIURIDS

Strongyloides callosciureus n. sp. (Nematoda: Rhabditoidea), from Asian sciurids, is described based on morphology, morphometry, and the small and large subunit (SSU/LSU) ribosomal RNA gene (rDNA) sequences. This new species was collected from Pallas's squirrels (Callosciurus erythraeus) in the central part of mainland Japan (Honshu), which were originally introduced from Taiwan some decades ago, and plantain squirrels (Callosciurus notatus) imported from Malaysia as personal pets. For comparison, Strongyloides robustus Chandler, 1942 was collected from American red squirrels (Tamiasciurus hudsonicus) and southern flying squirrels (Glaucomys volans) imported from the United States as personal pets. The parasitic females found in North American and Asian sciurids shared some key morphological features such as the ovary running spirally around the gut, and the shapes of the stoma in the apical view and the tail. However, morphometric features of parasitic females in North American and Asian sciurids differed significantly from each other; the former was larger than the latter, and the relative position of the vulva to the whole body length from the mouth was different. The SSU/LSU rDNA sequences supported the division of sciurid Strongyloides isolates by geographical distribution of the host and morphological features, leading us to propose the erection of new species.

Observations and Larval Descriptions of Fleas (Siphonaptera: Ceratophyllidae, Ctenophthalmidae, Ishnopsyllidae) of the Southern Flying Squirrel, Little Brown Bat, and Brazilian Free-Tailed Bat (Mammalia: Rodentia, Chiroptera)

Larvae of the four fleas infesting nests of the southern flying squirrel, Glaucomys volans colans (L.) [Conorhinopsylla stanfordi Stewart, Epitedia faceta (Rothschild), Opisodasys pseudarctomys (Baker), and Orchopeas howardi (Baker)], and of the bat fleas Myodopsylla insignis (Rothschild) and Sternopsylla distincta texana (C. Fox), associated with the bats Myotis lcifuigus (Le Conte) and Tadarida brasiliensis (I. Geof. St. Hilaire), respectively, are described. C. stanfordi has the second posterior-row seta on abdominal segments 1-5 at most one fourth the length of the first and third setae, but it is unique among the Leptopsyllini with five short setae in abdominal segment 9 anterior row. E. faceta has the straight line of anterior-row setae 2-5 on abdominal segment 1, which is diagnostic for Phalacropsyllini. O. howardi and O. pseudarctomys have three anterior-row setae on the anal comb, three ventrolateral setae on the anal segment (abdominal segment 10), and a narrow mandible with five or more teeth as other Ceratopyllinae, but O. pseudarctomys is distinguishable from O. howardi because the first setae on the posterior row of the head is long (greater than one half the length of the third posterior-row setae), the ventral setae on abdominal segment 7 are different sizes, and the third anterior-row setae on abdominal segment 8 does not extend past the spiracle posterior to it. Bat flea larvae have six posterior-row setae on abdominal segments 1-9 with the anal comb anterior row with two or more setae; M. insignis has eight mandible teeth and S. distincta texana three to four.

Explaining movement decisions of forest rodents in fragmented landscapes

Functional connectivity is a measure of the interaction of landscape structure and a species’ dispersal ability to determine the degree to which a landscape facilitates movement among patches. Dispersal through an inhospitable matrix requires that a species is willing to enter the matrix and can successfully colonize another habitat patch. Many connectivity indices have been developed which incorporate various attributes of the landscape, but little empirical evidence of the accuracy of these indices is available. We studied the ability of white-footed mice ( Peromyscus leucopus), eastern chipmunks ( Tamias striatus), and southern flying squirrels ( Glaucomys volans) to move through agricultural fields in west-central Indiana. Radio-collared animals were translocated into corridors that either were connected to or unconnected from an associated forest patch to determine their willingness to enter the matrix. Animals also were translocated into fields to determine how motivation to find resources influences movement through the matrix. All species demonstrated a strong motivation to find the forest. Animals were capable of moving through the matrix successfully, however, we were unable to determine whether they would do so willingly. Initial bearing was an important predictor for successfully reaching a forest patch, which has implications for modeling dispersal. Additionally, abiotic variables, such as temperature and precipitation, had a strong effect on latency to move from the release site. Although weather often correlates with seasonal migration, our study emphasizes the importance of weather in influencing short-term decisions on timing of movement.

SURVEY FOR ZOONOTIC RICKETTSIAL PATHOGENS IN NORTHERN FLYING SQUIRRELS, GLAUCOMYS SABRINUS, IN CALIFORNIA

Epidemic typhus, caused by Rickettsia prowazekii, is maintained in a southern flying squirrel (Glaucomys volans) sylvatic cycle in the southeastern United States. The northern flying squirrel (Glaucomys sabrinus) has not been previously associated with R. prowazekii transmission. A second rickettsial pathogen, Anaplasma phagocytophilum, infects dusky-footed woodrats (Neotoma fuscipes) and tree squirrels in northern California. Because northern flying squirrels or their ectoparasites have not been tested for these rickettsial pathogens, serology and polymerase chain reaction (PCR) were used to test 24 northern flying squirrels for R. prowazekii and A. phagocytophilum infection or antibodies. Although there was no evidence of exposure to R. prowazekii, we provide molecular evidence of A. phagocytophilum infection in one flying squirrel; two flying squirrels also were seropositive for this pathogen. Fleas and ticks removed from the squirrels included Ceratophyllus ciliatus mononis, Opisodasys vesperalis, Ixodes hearlei, Ixodes pacificus, and Dermacentor paramapertus.

How to Make a Flying Squirrel:GlaucomysAnatomy in Phylogenetic Perspective

Molecular evidence strongly supports the derivation of flying squirrels from tree squirrels, with the sister group being the Holarctic tree squirrels (Sciurus) and their close relatives. We present a rationale for the hypothesis that the transition occurred among small squirrels, and we propose using the northern flying squirrel (Glaucomys sabrinus) and the southern flying squirrel (Glaucomys volans) as models. Thus, we compare their morphologies with similar-sized tree squirrels (the Central American dwarf squirrel [Microsciurus alfari] and the western dwarf squirrel [M. mimulus]). We compare body proportions of Glaucomys with those of Microsciurus, considering differences as potential adaptations for gliding associated with wing loading, aspect ratio, and parasitic drag. We use the following measurements: lengths of the centra of the thoracic, lumbar, sacral, and caudal vertebrae; and lengths of the long bones (humerus, radius, femur, and tibia), metacarpals, metatarsals, and proximal phalanges of the hands and feet. We then compare these proportions of Microsciurus with those of other species of Sciurini, and the proportions of Glaucomys with other species of Pteromyini, to determine if each is representative or derived within its clade. Members of the genus Glaucomys exhibit relative elongation of the lumbar vertebrae and the forearm, relevant to wing loading and aspect ratio, relative lengthening of the midcaudal vertebrae, and relative shortening of the more distal caudal vertebrae, perhaps of importance for stability and control. Members of the genus Glaucomys also have shorter hands and feet, but these appeared to be elongated in Microsciurus, rather than shortened in Glaucomys, leaving the issue of parasitic drag moot. Finally, we speculate on the genetic changes that have produced these morphological modifications and may facilitate the evolution of gliding flight.

Aerodynamic force generation, performance and control of body orientation during gliding in sugar gliders (Petaurus breviceps)

Gliding has often been discussed in the literature as a possible precursor to powered flight in vertebrates, but few studies exist on the mechanics of gliding in living animals. In this study I analyzed the 3D kinematics of sugar gliders (Petaurus breviceps) during short glides in an enclosed space. Short segments of the glide were captured on video, and the positions of marked anatomical landmarks were used to compute linear distances and angles, as well as whole body velocities and accelerations. From the whole body accelerations I estimated the aerodynamic forces generated by the animals. I computed the correlations between movements of the limbs and body rotations to examine the control of orientation during flight. Finally, I compared these results to those of my earlier study on the similarly sized and distantly related southern flying squirrel (Glaucomys volans). The sugar gliders in this study accelerated downward slightly (1.0+/-0.5 m s(-2)), and also accelerated forward (2.1+/-0.6 m s(-2)) in all but one trial, indicating that the body weight was not fully supported by aerodynamic forces and that some of the lift produced forward acceleration rather than just balancing body weight. The gliders used high angles of attack (44.15+/-3.12 degrees ), far higher than the angles at which airplane wings would stall, yet generated higher lift coefficients (1.48+/-0.18) than would be expected for a stalled wing. Movements of the limbs were strongly correlated with body rotations, suggesting that sugar gliders make extensive use of limb movements to control their orientation during gliding flight. In addition, among individuals, different limb movements were associated with a given body rotation, suggesting that individual variation exists in the control of body rotations. Under similar conditions, flying squirrels generated higher lift coefficients and lower drag coefficients than sugar gliders, yet had only marginally shallower glides. Flying squirrels have a number of morphological specializations not shared by sugar gliders that may help to explain their greater lift generating performance.

Use of Small-volume Nest Boxes by Apis mellifera L. (European Honey Bees) in Alabama

Previous studies have documented that cavities < 10 liters are consistently rejected as nest sites by Apis mellifera (European honey bees). During a study of Glaucomys volans (southern flying squirrel) ecology in Alabama, however, honey bees occupied a total of 10 nest boxes with volumes of 5–6.7 liters. These observations are significant because they represent the smallest documented cavity volume accepted by honey bees, and also because they lend support to the theory that minimum acceptable cavity volume varies geographically. Small volume cavities may be accepted in the southeastern United States due to milder climates, a paucity of natural cavities, genetic differences in honey bees among regions, or some combination of these factors. Consequently, there may be increased potential for competition between honey bees and other cavity-nesting species in the Southeast.

Northern and southern flying squirrel use of space within home ranges in central Ontario

Partial harvesting can reduce the supply of dead and diseased trees in forests and as a result is predicted to negatively influence flying squirrel habitat. In this study, we measured the home range and habitat use of 13 radio-collared southern flying squirrels ( Glaucomys volans) in selection logged and uncut hardwood forests, and 14 radio-collared northern flying squirrels ( G. sabrinus) in unlogged coniferous forest in Algonquin Provincial Park, Ontario. Locations were collected on southern flying squirrels in 2003, and on northern flying squirrels in 2004. Southern flying squirrel home range and core area size showed no differences between unlogged and recent selection-harvested sites. Compared to available locations, southern flying squirrels radio-locations in uncut sites were associated with higher densities of decayed and mast trees, and greater overstory tree diversity, whereas in recent cuts, they were associated with higher densities of mast producing shrubs. Northern flying squirrel used locations that were characterized by older, decaying conifer trees with high understory sapling density and abundant spruce trees. Southern flying squirrel core areas were near nests, whereas northern flying squirrel core areas appeared to be used for foraging activity. Selection harvesting appears to support sufficient food resources for southern flying squirrels in the short term to maintain populations. However, we obtained evidence that the supply of nest trees may be limited in cuts, which may negatively impact future flying squirrel populations. The close association between northern flying squirrels and decayed trees may explain why we found no northern flying squirrels in two partially logged stands, where logging reduced the number of decaying trees.

Morphology, locomotor behaviour and microhabitat use in North American squirrels

AbstractThe rodent family Sciuridae (squirrels) presents an ideal system for examining the morphological, behavioural and ecological correlates of locomotor novelty. Ancestrally, sciurids were arboreal, a condition retained by modern tree squirrels. Two major transitions from the arboreal condition are hypothesized to have occurred in the sciurid clade: (1) flying squirrels evolved gliding from arboreal leaping (parachuting) and (2) chipmunks and ground squirrels became semiarboreal/terrestrial. This study examines morphology, locomotor behaviour and microhabitat use under controlled laboratory conditions in three North American sciurids: eastern chipmunkTamias striatus, red squirrelTamiasciurus hudsonicusand southern flying squirrelGlaucomys volans. Multivariate space was defined using a series of morphological measurements and by continuously sampling individuals moving under identical conditions in a naturalistic enclosure, controlling for the proximate effects of microhabitat structure. Morphospace was characterized by a contrast between proximal and distal limb elements – flying squirrels exhibited elongated forelimbs and shanks and shortened forefeet and hindfeet, while chipmunks exhibited the opposite pattern. Ethospace was characterized by a contrast between aerial locomotion in flying squirrels and ground‐based locomotion in chipmunks. In both instances, red squirrels occupied intermediate positions, as predicted on the basis of retention of ancestral features. Despite significant differences among species at morphological and behavioural levels, ecospace was characterized by overlap between flying squirrels and red squirrels in the use of high supports, and between flying squirrels and chipmunks in the use of large‐diameter supports. The lack of concordance at the ecological level underscores the difficulty in making predictions based solely upon organismal design.

Nest-Tree Use by Northern and Southern Flying Squirrels in Central Ontario

Little is known about nest use by flying squirrels (Glaucomys) in partially harvested forests, especially for northerly populations where cavity use is prevalent. We used radiotelemetry to examine nest use by 24 southern flying squirrels (G. volans) in 2003 in logged and unlogged hardwood forests, and by 18 northern flying squirrels (G. sabrinus) in 2004 in conifer forests, in Algonquin Provincial Park, Ontario, Canada. Of 76 nest trees used by G. volans, 71% were in declining trees and 22% were in snags. Sixty tree nests used by G. sabrinus included 28% snags, 46% declining trees, and 25% healthy trees, although nearly one-half of nests of G. sabrinus that were used on more than 3 occasions were in snags. G. volans used larger-diameter trees and American beech (Fagus grandifolia) more often than expected by chance, whereas G. sabrinus used trembling aspen (Populus tremuloides), white birch (Betula papyrifera), and yellow birch (B. alleghaniensis) more than expected by chance. Both species used a high proportion of cavity nests, few external nests, and trees that were decayed or diseased. We found indications that nest supply was limited in recently harvested sites, where there were fewer cavity trees and snags; however, G. volans may compensate by using abandoned yellow-bellied sapsucker nests and by nesting in aggregations. Hardwood snags and decaying trees appear to provide crucial nesting habitats for both squirrel species, particularly for females.

Flexible use of spatial cues in the southern flying squirrel (Glaucomys volans)

Insects, birds, and mammals have been shown capable of encoding spatial information in memory using multiple strategies or frames of reference simultaneously. These strategies include orientation to a goal-specific cue or beacon, to the position of the goal in an array of local landmarks, or to its position in the array of distant landmarks, also known as the global frame of reference. From previous experiments, it appears that birds and mammals that scatter hoard rely primarily on a global frame of reference, but this generalization depends on evidence from only a few species. Here we examined spatial memory in a previously unstudied scatter hoarder, the southern flying squirrel. We dissociated the relative weighting of three potential spatial strategies (beacon, global, or relative array strategy) with three probe tests: transposition of beacon and the rotation or the expansion of the array. The squirrels' choices were consistent with a spatial averaging strategy, where they chose the location dictated by at least two of the three strategies, rather than using a single preferred frame of reference. This adaptive and flexible heuristic has not been previously described in animal orientation studies, yet it may be a common solution to the universal problem of encoding and recalling spatial locations in an ephemeral physical landscape.

Reproductive and resource benefits to large female body size in a mammal with female-biased sexual size dimorphism

Factors underlying the evolution of female-biased sexual size dimorphism in mammals are poorly understood. In an effort to better understand these factors we tested whether larger female southern flying squirrels, Glaucomys volans, gained reproductive advantages (larger litters or more male mates) and direct resource benefits, such as larger home ranges or access to more food (i.e. mast-producing trees). As dimorphism can vary with age in precocial breeding species, we compared females during their first reproduction and during a subsequent breeding attempt. Females were not significantly larger or heavier than males at first reproduction, but became about 7% heavier and 22% larger than males at subsequent breeding. Larger females produced larger litters and had home ranges containing a greater proportion of upland hardwood trees. Female body size was not associated with either multiple male mating or home range size, but females with larger home ranges had higher indexes of body condition. Females in precocial breeding flying squirrels initiate reproduction before sexual size dimorphism is evident, and thus, may be allocating resources to both reproduction and growth simultaneously, or delaying growth entirely. Larger females produce more pups and have access to more food resources. Thus, selection for increased female size may partly explain how female-biased sexual size dimorphism is maintained in this species.

An Experimental Test of Snake Skin Use to Deter Nest Predation

Abstract Abstract Some bird species utilize snake skins as nesting material, possibly to decrease predation. We constructed 60 artificial nests simulating the nests of Great Crested Flycatchers (Myiarchus crinitus) in nest boxes to test the prediction that snake skins deter nest predators. Twenty of the boxes lacked rat snake (Elaphe obsoleta) skins (control), 20 had a single skin in the nest, and 20 had a skin in the nest and another displayed outside the box. Five of the control boxes were depredated (20%), while none of the experimental boxes were depredated. Our results supported our prediction that use of snake skins would deter mammalian predators, particularly the southern flying squirrel (Glaucomys volans). Although our results suggest a potential adaptive explanation for this behavior, our design did not allow us to address the degree of olfactory or visual detection by the squirrels, and left other potential explanations untested.

Mechanisms of Cache Retrieval in the Group Nesting Southern Flying Squirrel (Glaucomys volans)

AbstractWe examined the proximate mechanisms of cache retrieval in the group‐living, southern flying squirrel,Glaucomys volans, through a series of behavioral experiments conducted in a large indoor arena. The effectiveness of several retrieval mechanisms was determined including spatial memory, olfaction, random searching and a heuristic under different environmental conditions. Our goal was to elucidate the hoarding strategy of individuals in a nest group and to address whether food storing individuals possess a retrieval advantage over pilfering nestmates. A storer's retrieval advantage is necessary for scatter hoarding to be an evolutionarily stable strategy (ESS) within aggregations of unrelated individuals. Our previous work has shown that,G. volanslives in such groups, and consequently it was important to address the storer's retrieval advantage under a range of environmental conditions. Initially in our baseline experiment, we developed methods to eliminate olfactory‐based retrieval and to control for random searching. Subsequently, we experimentally determined the effectiveness of cache retrieval via spatial memory, a heuristic and olfaction. We examined the mechanisms of cache retrieval in three additional experiments using two independent subject populations and found that under dry, odorless conditions spatial memory was the most effective retrieval mechanism in support of a storer's retrieval advantage. In a fifth experiment we examined cache retrieval under wet environmental conditions and showed that olfactory‐based retrieval was effective and the storer's advantage was reduced. We interpret these laboratory results based on considerations of natural environmental conditions and game theory. We propose a conditional ESS strategy where animals store and retrieve their own caches as the primary food hoarding tactic and opportunistically pilfer caches as a secondary tactic.

Keeping Tabs: Are Redundant Marking Systems Needed for Rodents?

We use survival analysis to compare failure of passive integrated transponder (PIT) tags and loss of metal ear tags in 2,277 southern flying squirrels (Glaucomys volans), 124 house mice (Mus musculus), 112 hispid cotton rats (Sigmodon hispidus), and 374 deer (Peromyscus maniculatus) and cotton mice (P. gossypinus). With the exception of cotton rats, failure rates between ear and PIT tags differed by species. Flying squirrels exhibited the highest proportional loss of both tag types and lost ear tags more readily than PIT tags failed. The opposite was true for cotton rats and deer and cotton mice. Most PIT tags appeared to fail shortly after implantation (≤3 days), except for flying squirrels and, to a lesser extent, cotton rats. Ear tags exhibited a consistent rate of loss in flying squirrels. Body mass did not influence failure of PIT tags; however, flying squirrel body mass was associated with increased loss of ear tags. For flying squirrels PIT tag failure increased with the number of times an individual had already received a PIT tag that failed. We provide recommendations for using PIT and ear tags in marking rodents based on species-specific patterns and suggest the combined use of external and internal markers to obtain the most reliable estimates of population parameters.

Use of Fungal Rhizomorphs as Nesting Material by Glaucomys volans (Southern Flying Squirrels)

We examined 53 nests of southern flying squirrels constructed within nest boxes in Mobile County, AL. Of those containing a bedding layer (n = 35), 80% contained fungal rhizomorphs of Marasmius brevipes. Rhizomorphs of this genus have been reported in bird-nest descriptions, but have not been documented in flying squirrel nests. M. brevipes was common on our study site, and its use by flying squirrels may be unique to the area. Nevertheless, this and similar species of rhizomorph-producing fungi occur in other portions of the flying squirrel's range, and the nondescript nature of rhizomorphs may lead to their misidentification. Our observations appear to constitute the first description of an ecological relationship between this fungus and a mammalian species.