Fossorial Herbivores Research Articles

Plateau pika bioturbation leads to lower soil organic nitrogen fractions of bare patches in alpine meadows

The small semi–fossorial herbivore bioturbation has been verified to affect available soil nitrogen in grasslands, but the effects of small semi–fossorial herbivore bioturbation on soil organic nitrogen (SON) fractions that are main compositions of soil total nitrogen and sources of soil available nitrogen remain poorly known. The plateau pika (Ochotona curzoniae) bioturbation creates numerous bare patches, which intersperse within vegetated surfaces in grasslands. In this study, plateau pika was considered as an example animal to examine the differences of SON fractions between bare patches and vegetated surfaces under the small semi–fossorial herbivore bioturbation across six sites. This study demonstrated that acid–hydrolysable nitrogen (AHN) was 27.58% lower in bare patches than in vegetated surfaces. Amino acid nitrogen (AAN), ammonium nitrogen (AN), amino sugar nitrogen (ASN) and unknown nitrogen (UN) in bare patches were 35.23%, 17.07%, 17.70% and 19.87% lower than those in vegetated surfaces, respectively. The contribution of AAN to AHN was 5.3% lower in bare patches than in vegetated surfaces, but the contributions of AN, ASN and UN to AHN were 2.42%, 1.11%, and 1.77% higher, respectively. The response of AAN to plateau pika bioturbation was more sensitive than AN, ASN and UN. These findings verify the plateau pika bioturbation leads to a lower potential capacity of soil nitrogen supply in bare patches than in vegetated surfaces, and present a possible pattern of SON fractions in relation to small semi–fossorial herbivore bioturbation in grasslands.

The Distinctive Biology and Characteristics of the Bare-Nosed Wombat (Vombatus ursinus).

The bare-nosed wombat is an iconic Australian fauna with remarkable biological characteristics and mythology. This solitary, muscular, fossorial, herbivorous marsupial from southeast Australia has continent and continental island subspeciation. Vombatiformes also contains hairy-nosed wombats (Lasiorhinus spp.); koala (Phascolarctos cinereus); and extinct megafauna, Phascolonus gigas (giant wombat), Diprotodon, and Thylacoleo (marsupial lion). Culturally important to Aboriginal people, bare-nosed wombats engineer ecosystems through digging, grazing, and defecation. Olfaction and cubic fecal aggregations appear critical for communication, including identity, courtship, and mating. Though among the largest fossorial herbivores, they have a nutrient-poor diet, a home range up to an order of magnitude smaller than expected, and a metabolism among the lowest extreme for mammals >10 kg. Metabolic depression may confer advantages over resource competitors and fossorial lifestyle protection from predators, fires, and climatic extremes. Bare-nosed wombats are loved and persecuted by European colonists. Recent population increases may reflect softening attitudes toward, and greater protections of, bare-nosed wombats.

Diet of two fossorial herbivores in a seasonally snow-covered environment

To understand the recent elevational range expansion of European rabbits (Oryctolagus cuniculus) with declining snow cover and earlier snow thaw we examined their diet in relation to that of long-term residents, common wombats (Vombatus ursinus). The colonisation of eastern Australia by rabbits was effectively completed by 1910 when they reached an elevation of 1500 m (the winter snowline). Rabbits began to penetrate higher elevations only from the 1970s in association with anthropogenic habitat modification. Since 2011, rabbits have occupied elevations to the alpine treeline (~1850 m) throughout the year without the ameliorating presence of infrastructure or anthropogenically modified vegetation. Rabbits and wombats are both grazers preferring grasses (largely inaccessible beneath winter snow) and are spatially restricted in their foraging by their need to return to their burrows. Wombats used a much wider foraging range, enabling them to select preferred food. Rabbits, with a much smaller range, were constrained in their choice of forage mainly to plants that projected above the snow. Unexpectedly, rabbits fed intensively on leaves of eucalypts, food not typically consumed in substantial quantities by this species. These leaves, on stems regenerating after fire, will diminish in availability as stems mature, possibly halting the range expansion of rabbits.

MOLECULAR SYSTEMATICS OF POCKET GOPHERS OF THE GENUS GEOMYS

Pocket gophers (Rodentia: Geomyidae) are fossorial herbivores, sister to the New World Heteromyidae, and, with one exception (Orthogeomys), are restricted in distribution to North America. Because they occur in small, isolated demes and possess an overall lack of vagility as well as conservative morphology, these rodents pose many problems with respect to their taxonomy, systematics, evolutionary history, and intrageneric affinities. Members of the genus Geomys are no exception. Species of Geomys occur in the southeastern United States and throughout much of the central and southern Great Plains westward to the eastern slope of the Rocky Mountains and south into northern Mexico (Fig. 1). Considerable uncertainty exists concerning the number of species present and the historical relationships among described taxa. Much of the confusion involves the presence of sibling species, with little or no morphological differentiation and, in some instances, high degrees of chromosomal diversification and allozymic variation. Merriam (1895), in his revision of pocket gophers of the family Geomyidae (exclusive of Thomomys), recognized 3 species groups within Geomys: the tuza (¼ pinetis) group including what is today recognized as G. pinetis; the bursarius

Influence of Resource Removal on Demography of Attwater's Pocket Gopher

Nutrient balancing is a foraging strategy whereby herbivores ingest a mixture of dietary items to ensure an adequate intake of nutrients to maintain individual health and reproduction. Recent findings indicate that terrestrial herbivorous rodents select dietary items from both dicotyledonous (dicots) and monocotyledonous (monocots) plants to obtain requisite nutrients, which may, in turn, influence demographic processes within the population. We investigated how availability of a major food source, dicots, affected population dynamics of Geomys attwateri , a fossorial herbivore. We removed dicots from the habitat in four plots and compared body mass, density, reproduction, recruitment, age-class, sex ratio, length of residency, and spatial distribution of pocket gophers in these areas to pocket gophers in areas with dicots. Removal of dicots reduced the proportion of reproductive females and average length of time in residency within a plot for both sexes. These effects, in turn, resulted in reduced density of pocket gophers in areas having lowered dicot availability. Spatial arrangement of pocket gophers within plots was not affected by removal of dicots but differed by season. Our experiment demonstrates the mechanism for reduction in density of pocket gophers and shows a link between foraging strategy, intake of dietary items, and demographic processes.

A spatially-explicit model of search path and soil disturbance by a fossorial herbivore

Spatially-explicit movement models are useful tools for elucidating how well we understand a consumer species' behavioral responses to landscape structure, as well as for exploring hypotheses concerning the factors underlying such responses. In the case of fossorial herbivores, these responses can lead to significant changes in soil properties, vegetation, and even topography. These animals search for food plants by digging tunnels through soil at plant rooting depth. I developed a spatially-explicit, stochastic movement model (SEARCH3, written in FORTRAN) to simulate the search path and associated tunnel construction undertaken by a pocket gopher (Rodentia: Geomyidae) searching for food plants. SEARCH3 assumes a landscape uniform except for number and location of plants. Input parameters include soil properties, animal size, and plant locations. Model output includes tunnel segment coordinates, positions of plants disturbed, and volume and mass of soil disturbed. Coordinates can be input into graphics software or a GIS to create line maps. The present model incorporates the three methods of segment construction presented in Andersen (1988, J. Mammal., 69: 565–582), construction parameters (e.g., tunnel size, segment length, and directionality angles) empirically described for the plains pocket gopher ( Geomys bursarius), and both random and area-restricted search. SEARCH3 invokes the latter for a set period after a palatable plant is detected. The geometric attributes of paths generated by SEARCH3 conform to those of real tunnel systems at coarse scales, with the exception that looping paths from simulations featuring high plant density are uncommon among most geomyid species' systems. Results of simulations in which sensory ability and plant dispersion patterns were systematically changed support the hypothesis that area-restricted search is adaptive in this taxon. The simulation effort also suggests that research on sensory abilities and excavation mechanics would contribute greatly to understanding how these organisms both affect, and are affected by, the ecosystems in which they reside.

Effects of Subterranean Mammalian Herbivores on Vegetation

Fossorial herbivores are common in Eurasia, North and South America, and Africa, particularly in arid and semiarid regions. There is ample evidence, although often indirect and semiquantitative, that they have local and broad-scale effects on vegetation. These effects arise from feeding, harvesting, and caching, local soil disturbances, and longer-term changes in soil structure and topography, many aspects of which are similar among the diversity of fossorial herbivores. Often, the net effect of these animals' activities is alteration of composition of plant species and increased plant diversity. Standing crop of plants often is reduced, and long- and short-term changes in productivity can occur. Better understanding of the rules that govern diet selection and burrow size, dynamics, and geometry are needed to predict effects of these animals under specific environmental conditions.

Distinct Animal‐Generated Edge Effects in a Tallgrass Prairie Community

EcologyVolume 74, Issue 4 p. 1281-1285 Article Distinct Animal-Generated Edge Effects in a Tallgrass Prairie Community O. J. Reichman, O. J. ReichmanSearch for more papers by this authorJ. H. Bendix, J. H. BendixSearch for more papers by this authorT. R. Seastedt, T. R. SeastedtSearch for more papers by this author O. J. Reichman, O. J. ReichmanSearch for more papers by this authorJ. H. Bendix, J. H. BendixSearch for more papers by this authorT. R. Seastedt, T. R. SeastedtSearch for more papers by this author First published: 01 June 1993 https://doi.org/10.2307/1940496Citations: 37AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume74, Issue4June 1993Pages 1281-1285 RelatedInformation

Search Path of a Fossorial Herbivore, Geomys bursarius, Foraging in Structurally Complex Plant Communities

The influence of habitat patchiness and unpalatable plants on the search path of the plains pocket gopher ( Geomys bursarius ) was examined in outdoor enclosures. Separate experiments were used to evaluate how individual animals explored (by tunnel excavation) enclosures free of plants except for one or more dense patches of a palatable plant ( Daucus carota ), a dense patch of an unpalatable species ( Pastinaca sativa ) containing a few palatable plants ( D. carota ), or a relatively sparse mixture of palatable ( D. carota ) and unpalatable ( Raphanus sativus ) species. Only two of eight individuals tested showed the predicted pattern of concentrating search effort in patches of palatable plants. The maintenance of relatively high levels of effort in less profitable sites may reflect the security afforded food resources by the solitary social system and fossorial lifestyle of G. bursarius . Unpalatable plants repelled animals under some conditions, but search paths in the sparsely planted mixed-species treatment suggest animals can use visual or other cues to orient excavations. Evidence supporting area-restricted search was weak. More information about the use of visual cues by G. bursarius and the influence of experience on individual search mode is needed for refining current models of foraging behavior in this species.

Tunnel-Construction Methods and Foraging Path of a Fossorial Herbivore, Geomys bursarius

Abstract.—The fossorial rodent Geomys bursarius excavates tunnels to find and gain access to belowground plant parts. This is a study of how the foraging path of this animal, as denoted by feeding-tunnel systems constructed within experimental gardens, reflects both adaptive behavior and constraints associated with the fossorial lifestyle. The principal method of tunnel construction involves the end-to-end linking of short, linear segments whose directionalities are bimodal, but symmetrically distributed about 0°. The sequence of construction of left- and right-directed segments is random, and segments tend to be equal in length. The resulting tunnel advances, zigzag-fashion, along a single heading. This linearity, and the tendency for branches to be orthogonal to the originating tunnel, are consistent with the search path predicted for a “harvesting animal” (Pyke, 1978) from optimal-foraging theory. A suite of physical and physiological constraints on the burrowing process, however, may be responsible for this geometric pattern. That is, by excavating in the most energy-efficient manner, G. bursarius automatically creates the basic components to an optimal-search path. The general search pattern was not influenced by habitat quality (plant density). Branch origins are located more often than expected at plants, demonstrating area-restricted search, a tactic commonly noted in aboveground foragers. The potential trade-offs between construction methods that minimize energy cost and those that minimize vulnerability to predators are discussed.

Below-Ground Herbivory in Natural Communities: A Review Emphasizing Fossorial Animals

Roots, bulbs, corms, and other below-ground organs are almost universally present in communities containing vascular plants. A large and taxonomically diverse group of herbivores uses these below-ground plant parts as its sole or primary source of food. Important within this group are plant-parasitic nematodes and several fossorial taxa that affect plants through their soil-disturbing activities as well as by consuming plant tissue. The fossorial taxa are probably best exemplified by fossorial rodents, which are distributed on all continents except Australia. All other fossorial herbivores are insects. The impact of below-groud herbivory on individual plant fitness will depend upon the extent to which, and under what circumstances, the consumption of plant tissue disrupts one or more of the six functions of below-ground plant parts. Below-ground herbivory is probably more often chronic than acute. Indirect evidence suggests that plants have responded evolutionarily to herbivory by enhancing the functional capacities of below-ground organs, thus developing a degree of tolerance, and by producing compounds that serve as feeding deterrents. Many plant species respond to the removal of root tissues by increasing the growth rate of the remaining roots and initiating new roots. Soil movement and mixing by fossorial rodents infleuce the environment of other below-ground herbivores as well as that of plants and plant propagules. The relationships among the various groups of below-ground herbivores, and between below-ground herbivores and plants, are at best poorly known, yet they appear to have major roles in determining the structure and regulating the functioning of natural communities.

Nutritional ecology of a fossorial herbivore: protein N and energy value of winter caches made by the northern pocket gopher, Thomomys talpoides

Northern pocket gophers (Thomomys talpoides) are fossorial herbivores that excavate belowground plant parts for food. In subalpine areas during autumn and winter, pocket gophers hoard plant parts in caches placed in or under snow. We examined the size and composition of 17 nival caches and tested the hypotheses that (i) cached food can provide complete energy and protein N sustenance during typical periods when burrowing is precluded by soil conditions, and (ii) cached food is a random sample of items encountered by burrowing gophers during tunnel excavation. Our data indicate that caches provide substantially more energy than protein in terms of a pocket gopher's daily maintenance requirements. Nevertheless, quantities stored are sufficient to allow individuals to endure commonly encountered adverse environmental conditions without entering negative energy or protein balance. Analysis of stomach contents and a comparison of cache composition to availability of plant species suggests that gophers consume high-protein items as they are encountered, and store low-protein items in caches.