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Evolution sometimes proceeds by loss, especially when structures and genes become dispensable after an environmental shift relaxes functional constraints. Subterranean vertebrates are outstanding models to analyze this process, and gene decay can serve as a readout. We sought to understand some general principles on the extent and tempo of the decay of genes involved in vision, circadian clock, and pigmentation in cavefishes. The analysis of the genomes of two Cuban species belonging to the genus Lucifuga provided evidence for the largest loss of eye-specific genes and nonvisual opsin genes reported so far in cavefishes. Comparisons with a recently evolved cave population of Astyanax mexicanus and three species belonging to the Chinese tetraploid genus Sinocyclocheilus revealed the combined effects of the level of eye regression, time, and genome ploidy on eye-specific gene pseudogenization. The limited extent of gene decay in all these cavefishes and the very small number of loss-of-function mutations per pseudogene suggest that their eye degeneration may not be very ancient, ranging from early to late Pleistocene. This is in sharp contrast with the identification of several vision genes carrying many loss-of-function mutations in ancient fossorial mammals, further suggesting that blind fishes cannot thrive more than a few million years in cave ecosystems. [ABSTRACT FROM AUTHOR]

Soil degradation may have strong negative consequences for soil biodiversity, but these potential effects are understudied and poorly understood. Concentration of nesting seabirds may be a source of soil pollution by heavy metals, which are incorporated into the food chain and may have toxicological effects in vertebrates, especially in fossorial animals with low dispersal ability. We examined whether contamination by heavy metals, derived from seagull depositions, and other soil characteristics, may affect the levels of faecal glucocorticoid metabolites (as a potential indicator of physiological stress) of the fossorial amphisbaenian reptile Trogonophis wiegmanni. We found a relationship between soil pollution by heavy metals and increased levels of faecal corticosterone metabolite of the amphisbaenians that live buried in those soils. This can be due to the strong endocrine disruption effect of heavy metals. In addition, there was an independent effect of the soil texture, with amphisbaenians showing higher levels of faecal corticosterone metabolite in soils with less sand and more silt and clay, which are more energetically costly to dig. Long-term exposure to high glucocorticoid levels might have serious effects on health state and fitness of fossorial animals that may be unnoticed. Our study emphasizes that, to prevent future conservation problems, we need to perform periodic surveys on the physiological health state of the little-known subterranean biodiversity. [ABSTRACT FROM AUTHOR]

One method burrowing animals are hypothesized to use in adapting to the presumed hypoxic subterranean environment is increasing the oxygen-carrying capacity of blood. A number of recent studies have examined hematologic parameters in laboratory-reared naked mole-rats, but not in animals living under natural atmospheric conditions. To our knowledge, blood chemistry parameters have never been systematically assessed in a fossorial mammal. In this study we examined the blood of wild naked mole-rats in Kenya and Ethiopia to determine whether their blood chemistry differs significantly from naked mole-rats born and living in captivity. We also compared our results to published values for hystricomorphs, other subterranean rodents, and surface-dwelling rodents of similar size. [ABSTRACT FROM AUTHOR]

We determined patterns of burrow use by juvenile platypuses (Ornithorhynchus anatinus) in their natal home range, and evaluated associations between burrows and vegetation. Between March 2015 and March 2017, we captured seven juvenile platypuses along a 3-km stretch of Badger Creek, Victoria and fitted them with radiotransmitters. We recorded the locations of animals in their burrows daily while transmitters were attached (range: 14–132 days). Juveniles used 74 different burrows, with each using 11 ± 2 burrows. Overall, 65% of burrows (48) were used once, 22% (16) were used between 2 and 9 times (moderate-use), and 13% (10) were used frequently (> 10 times). No juveniles dispersed during the monitoring period (14–132 days). Although some association was observed between burrow use and particular vegetation communities, vegetation was not a strong factor driving site selection of burrows. Use of multiple burrows may allow juveniles to avoid competition with conspecifics, reduce exposure to ectoparasites, and develop shelter-seeking behavior. Juvenile platypuses remained in their natal home range, where conditions are likely to be good because they supported recent breeding, while completing their growth and development prior to dispersal. [ABSTRACT FROM AUTHOR]

The phylogenetic relationships between the three main clades of worm snakes remain controversial. This question is, however, crucial to elucidate the origin of the successful snake radiation, as these burrowing and miniaturized wormlike organisms represent the earliest branching clades within the snake tree. The present molecular phylogenetic study, intended to minimize the amount of missing data, provides fully resolved inter‐subfamilial relationships among Typhlopidae. It also brings robust evidence that worm snakes (Scolecophidia) are paraphyletic, with the scolecophidian family Anomalepididae recovered with strong support as sister clade to the 'typical snakes' (Alethinophidia). Ancestral state reconstructions applied to three different traits strongly associated to a burrowing life‐style (scolecoidy, absence of retinal cones and microstomy) provide results in favour of a burrowing origin of snakes, and suggest that worm snakes might be the only extant fossorial representatives of the primordial snake incursion towards an underground environment. [ABSTRACT FROM AUTHOR]

In contrast to the extraordinary adaptive radiation of Caribbean Anolis lizards, head-first burrowing worm lizards (Amphisbaenia) of the Greater Antilles show a high degree of evolutionary conservatism in both taxonomic and phenotypic diversity. While Caribbean anoles reach over 160 endemic species and six ecomorphs, amphisbaenians peak at one to seven species per island and are characterized by two distinct head shapes, each associated with a specific burrowing behaviour. Using three-dimensional landmark-based geometric morphometrics, we found that Caribbean amphisbaenians also occupy a relatively confined area of skull morphospace, with considerable overlap between species from different islands and strong morphological integration between crania and mandibles. The only exceptions were the bizarre keel-headed cadeids (Cadea) from Cuba, which appear to be unlike other round-headed Caribbean forms and closer to Mediterranean blanids (Blanus), their putative sister group. The only significant differences in skull shape were found between insular amphisbaenians and their mainland relatives, indicating that fossorial vertebrates may respond differently to ecological opportunity than other terrestrial fauna. Given their highly specialized subterranean niche, we suggest that worm lizards are under strong stabilizing selection to maintain cranial proportions for head-first digging, thus limiting their ability to exploit novel resources (e.g. microhabitat, prey) encountered in insular environments. [ABSTRACT FROM AUTHOR]

Crayfishes are an excellent model for examining complex behaviors such as homing. We examined homing behaviors in two species of crayfish. Individuals of Creaserinus fodiens (Cottle, 1863), a primary burrower, and Faxonius rusticus (Girard, 1852), a tertiary burrower, were placed in an arena with artificial burrows embedded within a rotating disk. The disks allowed for the displacement of burrows by 90° relative to the original location. Individuals were motivated to perform search behavior with the presence of food. The burrows were displaced once individuals had left the burrows and their return pathways were examined. The paths were digitized and analyzed for kinematic parameters. Crayfishes in the control group located the burrows successfully but individuals in the experimental group (displaced burrow) were unable to locate the burrows successfully. There were significant differences (P = 0.001) between the control and treatment groups in heading angles relative to burrow on the return trip, with the heading angles of the control group being significantly lower (P = 0.0003). There were species-specific differences in velocity toward the burrow, with the primary burrower being more negatively impacted by the displacement. The results confirm that the effect of burrow displacements severely impacts homing success in both species and a local cue associated with the burrow is not utilized in homing. We demonstrate that there are no significant species-specific differences in homing behavior. [ABSTRACT FROM AUTHOR]

Calyptophractus retusus (Burmeister, 1863), commonly called the greater fairy armadillo, is a small armadillo in a monotypic genus. It is a poorly known, fossorial species with a reduced eye and ear, fixed carapace and greatly enlarged foreclaws adapted for digging. The species is confined to the Chaco region of northern Argentina, western Paraguay, and southern Bolivia where it is apparently locally distributed in areas with soft, sandy soils. The species is considered “Data Deficient” by the International Union for Conservation of Nature and Natural Resources. [ABSTRACT FROM AUTHOR]

Recent studies show Xenarthra to be even more isolated systematically from other placental mammals than traditionally thought. The group not only represents 1 of 4 primary placental clades, but proposed links to other fossorial mammal taxa (e.g., Pholidota, Palaeanodonta) have been contradicted. No unambiguous Paleocene fossil xenarthran remains are known, and Eocene remains consist almost exclusively of isolated cingulate osteoderms and isolated postcrania of uncertain systematic provenance. Cingulate skulls are unknown until the late middle Eocene, and the oldest sloth and anteater skulls are early Oligocene and early Miocene age, respectively; there are no nearly complete xenarthran skeletons until the early Miocene. Ecological reconstructions of early xenarthrans based on extant species and the paleobiology of extinct Neogene taxa suggest the group's progenitors were myrmecophagous with digging and perhaps some climbing adaptations. The earliest cingulates were terrestrial diggers and likely myrmecophagous but soon diverged into numerous omnivorous lineages. Early sloths were herbivores with a preference for forested habitats, exhibiting both digging and climbing adaptations. We attribute the rarity of early xenarthran remains to low population densities associated with myrmecophagy, lack of durable, enamel-covered teeth, and general scarcity of fossil localities from tropical latitudes of South America. The derivation of numerous omnivorous and herbivorous lineages from a myrmecophagous ancestor is a curious and unique feature of xenarthran history and may be due to the peculiar ecology of the native South American mammal fauna. Further progress in understanding early xenarthran evolution may depend on locating new Paleogene fossil sites in northern South America. [ABSTRACT FROM AUTHOR]

The dominant hypothesis for the evolutionary origin of snakes from 'lizards' (non-snake squamates) is that stem snakes acquired many snake features while passing through a profound burrowing (fossorial) phase. To investigate this, we examined the visual pigments and their encoding opsin genes in a range of squamate reptiles, focusing on fossorial lizards and snakes. We sequenced opsin transcripts isolated from retinal cDNA and used microspectrophotometry to measure directly the spectral absorbance of the photoreceptor visual pigments in a subset of samples. In snakes, but not lizards, dedicated fossoriality (as in Scolecophidia and the alethinophidian Anilius scytale) corresponds with loss of all visual opsins other than RH1 (kmax 490- 497 nm); all other snakes (including less dedicated burrowers) also have functional sws1 and lws opsin genes. In contrast, the retinas of all lizards sampled, even highly fossorial amphisbaenians with reduced eyes, express functional lws, sws1, sws2 and rh1 genes, and most also express rh2 (i.e. they express all five of the visual opsin genes present in the ancestral vertebrate). Our evidence of visual pigment complements suggests that the visual system of stem snakes was partly reduced, with two (RH2 and SWS2) of the ancestral vertebrate visual pigments being eliminated, but that this did not extend to the extreme additional loss of SWS1 and LWS that subsequently occurred (probably independently) in highly fossorial extant scolecophidians and A. scytale. We therefore consider it unlikely that the ancestral snake was as fossorial as extant scolecophidians, whether or not the latter are para- or monophyletic. [ABSTRACT FROM AUTHOR]

An intensive single season pilot study was conducted with the digger crayfish, Fallicambarus fodiens (Cottle, 1863) to evaluate relationships between burrow and wetland attributes. Factor Analysis identified significant factors correlated with burrow placement, individual presence, type and frequency of activity. Factor 1 explained 36.89% of the variance associated with hydric type, percent soil moisture, fine substrate grain sizes, and habitat condition, while factor 2 explained 14.78% of the variance based on large grain particle sizes. A significant difference was observed in crayfish inhabitant activity with trap status, burrow state, and presence of activity. Four specific types of activities were related to distance to above groundwater including the trap being pulled into the burrow, the burying of the trap into a burrow cap, a capped burrow established beneath the trap, and relationship with standing water. Based on 12.5% individual recapture, 100% were present in the original burrow of capture. [ABSTRACT FROM AUTHOR]

Itjaritjari, the southern marsupial mole ( Notoryctes typhlops), is an extreme fossorial species that is very rarely encountered on the surface and has been regarded as a sand swimmer that leaves no reliable trace of its passage through the sand. Like many extreme fossorial species on other continents, itjaritjari is poorly known and is considered rare and threatened. In this study, surface tracks known to have been made by itjaritjari were followed underground where they became clearly defined, circular, sand-filled tunnels with a mean diameter of 39 mm. Trenches dug to expose vertical sections of dune revealed that backfilled tunnels of similar appearance and dimensions were common on dunes in the study areas, averaging 3.2 backfilled tunnels per vertical square meter. Loose sand, and thus opportunities for sand swimming, is confined to the surface in the Australian dune fields, which are well vegetated and characterized by lightly bonded sand. Rather than sand swim, itjaritjari carves tunnels and backfills as it goes, leaving clearly distinguishable and unique traces of its passage ('moleholes') that accumulate over years or decades. This finding provides a much needed means of investigating the distribution, abundance, and conservation of marsupial moles. The technique may have application in the study of several other elusive fossorial species on other continents that may backfill their tunnels, many of which are endangered. [ABSTRACT FROM AUTHOR]

The East African root rat (Tachyoryctes splendens) is a solitary fossorial rodent occurring in the eastern parts of central Africa. Unlike bathyergid mole-rats, T. splendens occasionally goes aboveground to feed and consequently it is periodically exposed to the natural light-dark cycle. The locomotor activity of T. splendens was assessed under various light regimes. T. splendens entrains its activity to light cycles and displays distinct nocturnal activity with the total percentage of activity during the dark phase at 87.78% ± SD 11.01%. In constant darkness, T. splendens shows free-running rhythms of slightly shorter than 24 h (2340 ± SD 013 h), while still exhibiting most of its activity during subjective night. Upon inversion of the light cycle, time of reentrainment was exceptionally long. Nocturnal activity time (α) was shortened in response to a shorter night length from 1129 to 0746 h; however, when the dark phase was lengthened, α remained roughly similar to that of the 12L:12D photoperiod at 1124 h. A difference in circadian activity is apparent from the laboratory and field findings, thus in a natural situation, other environmental factors may influence activity patterns. [ABSTRACT FROM AUTHOR]

The worm-like snakes ( Scolecophidia; approximately 400 nominal extant species) have a conservative morphology and are among the most poorly-known terrestrial vertebrates. Although molecular evidence has helped determine their higher-level relationships, such data have rarely been used to discriminate among species. We generated a molecular data set for the continental Australian blindsnakes (genus Ramphotyphlops) to determine the concordance of molecular and morphological information in the taxonomic recognition of species. Our dataset included 741 specimens morphologically attributed to 27 nominal Ramphotyphlops species. We proposed species hypotheses ( SHs) after analysis of sequences from a variable mitochondrial gene ( cytochrome b) and examined these SHs with additional evidence from a nuclear gene ( prolactin receptor) and geographical data. Although the nuclear marker was not as fast-evolving and discriminating as the mitochondrial marker, there was congruence among the mitochondrial, nuclear, and geographical data, suggesting that the actual number of species is at least two times the current number of recognized, nominal species. Several biogeographical barriers and complex phytogeographical and geological patterns appeared to be involved in the division of some burrowing snake populations and, by consequence, in their diversification and speciation through isolation. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110, 427-441. [ABSTRACT FROM AUTHOR]

The burrowing activity of the only European fiddler crab species, Uca tangeri (Eydoux, 1835), was studied along the shores of the estuary of the Piedra River in Lepe, southwestern Spain. Casting of burrows allowed recognition of their simple, J-shaped to irregular architecture, which displays striking similarities to fossil Pliocene burrows in the same area. The finding of body fossils of U. tangeri in contemporaneous strata indicates these trace fossils are produced by the same species and demonstrate its presence in the eastern Atlantic coast at least for the last three million years. Burrows of U. tangeri are similar to those of other Uca spp. worldwide and also to those of other brachyurans. Their architectural simplicity makes difficult their definitive recognition in the fossil record. Nevertheless, review of existing literature confirms the presence of brachyuran burrows at least since the Cretaceous. [ABSTRACT FROM AUTHOR]

Cabassous centralis (northern naked-tailed armadillo) is a small armadillo with a slender tail. The distinctive tail has widely spaced, thin plates that are gray-pink in color. This fossorial armadillo occurs in diverse tropical habitats and has a distributional range from southern Mexico, through Central America, and into northern South America (Colombia, Venezuela, and Ecuador). C. centralis is listed as ''Least Concern'' by the International Union for Conservation of Nature and Natural Resources, and is rare everywhere. [ABSTRACT FROM AUTHOR]

The article focuses on a study that explored the proposed relationship between mallines and sociality in the colonial tucos-tuco, Ctenomys sociabilis, by characterizing the habitats occupied by the species at three locations representing the extremes of its geographic range. The plant species and vegetative structure associated with the burrow systems of the tuco-tucos are described. The study's implications for understanding the distinctive social behavior of the species are discussed.

We reviewed the literature on burrows of North American ground-dwelling squirrels to assess factors influencing burrow length and depth. Prior research suggested that soil characteristics and burrow age can influence burrow dimensions; we extended these findings by evaluating the influence of body size, temperature stress, and degree of sociality. We found that body size was positively correlated with burrow length and depth, probably because larger species require more space for underground activities. This relationship did not hold for Marmota monax and M. flaviventris, for unknown reasons. Burrow length scaled allometrically with body mass (b = 0.72), possibly because the metabolic effects of limited ventilation in burrows placed a constraint on burrow length. Temperature stress was not related to burrow depth, perhaps because of the insulation provided by snow and soil. The more highly social species excavated longer burrow systems, probably because of the greater space needs of multiple residents per burrow. [ABSTRACT FROM AUTHOR]

Isolated or semi-isolated small populations are commonly found among species, due to a naturally patchy occupancy of suitable habitats or also as a result of habitat alterations. These populations are subject to an increased risk of local extinction because they are more vulnerable to demographic, genetic, and environmental stochasticity. Considering that natural areas have been becoming progressively more fragmented and smaller, understanding the genetic structure and evolutionary dynamics of small populations is critical. Ctenomys lami has 26 karyotypes distributed in a small area (936 km2 ) continually modified by human actions. We assessed the genetic geographical structure of this species, examining 178 specimens sampled on a fine scale, using information from chromosomal variability, mitochondrial DNA control region and cytochrome c oxidase subunit I sequences, and 14 microsatellite loci. The observed isolation-by-distance pattern and a clinal genetic variation suggest a stepping-stone population model. The results did not indicate genetic structuring associated with distinct karyotypes. However, mitochondrial and nuclear molecular markers demonstrated the existence of 2 demes, which are not completely isolated but are probably reinforced by a geographical barrier. The vulnerability of C. lami is greater than previously supposed, and our data support the designation of one Evolutionary Significant Unit and one Management Unit, and also the inclusion of this species' conservation status as vulnerable. [ABSTRACT FROM PUBLISHER]

Alpheidae are a highly diverse group of carideans with various life histories. They are known to possess specialized body forms and appendages, form facultative and obligate symbiotic relationships, and even exhibit complex behaviors like eusociality. This study represents the first documented association between the alpehid shrimp Alpheus rapax Fabricius, 1798 and the gobiid fish Myersina macrostoma. An undocumented behavioral display was observed in eight A. rapax individuals. The display was only performed in newly molted individuals while within their respective burrows in the presence of light. The display consisted on the following repetition: shrimp shifted its entire body forwards, with the cephalothorax angled downwards with respect to the pleon and both chelipeds extended forwards and towards each other; body jerked rapidly backwards with pleon curled and walking pereiopods extended; cephalothorax angled upwards, while the chelipeds were spread apart and moved backwards; and continuous undulations of pleopods. The display was hypothesized to either contribute to physiological requirements post molting or as a dishonest signal. [ABSTRACT FROM AUTHOR]

Among crayfish, primary burrowing species are the least understood ecologically. Many primary burrowing crayfish inhabit floodplains where forested landscapes have been fragmented by agricultural, industrial, or residential uses. In this study, site occupancy rates (ψAmong crayfish, primary burrowing species are the least understood ecologically. Many primary burrowing crayfish inhabit fioodplains where forested landscapes have been fragmented by agricultural, industrial, or residential uses. In this study, site occupancy rates (ψ) were modeled for two primary burrowing crayfish, Fallicambarusfodiens (Cottle, 1863) and Cainbarus thomai Jezerinac, 1993, from Ohio and Kanawha river fioodplains in West Virginia, U.S.A. Fallica,nbarusfodiens is one of West Virginia's rarest crayfish, while C. thomai is prevalent in most wetlands along both river fioodplains. Occupancy rate modeling incorporated four environmental covariates (forest age, soil type, tree frequency, and land use). Based on presence/absence data, forests with tree ages >100 years (ΔQAICc = 0) and Sites with loam soils (ΔQAICc = 1.80) were most likely to harbor F. fodiens populations. For C. thomai, several models were supported owing to model selection uncertainty, but those with the land use covariate had more total model weight (total wi = 0.54) than all other covariate models. Cambarus thomai rarely occupied industrial/agricultural sites, but were often present in forested and residential sites. Although the influence of covariates on site occupancy differed between species, both taxa readily utilized mature forested habitats when available. Conservation actions for F. fodiens and C. thomai should focus on preserving forested tracts along large river floodplains. [ABSTRACT FROM AUTHOR]

Evolutionary simplification, or loss of complex characters, is a major theme in studies of body-form evolution. The apparently infrequent evolutionary reacquisition of complex characters has led to the assertion (Dollo's Law) that once lost, complex characters may be impossible to re-evolve, at least via the exact same evolutionary process. Here, we provide one of the most comprehensive, fine-scale analyses of squamate body-form evolution to date, introducing a new model system of closely related, morphologically variable, lizards. Our phylogenetic results support independent instances of complete limb loss as well as multiple instances of digit and external ear opening loss and re-acquisition. Even more striking, we find strong statistical support for the re-acquisition of a pentadactyl body form from a digit-reduced ancestor. Our study reveals that species of the genus Brachymeles exemplify regions of morphospace (body plans) previously undocumented in squamates. Our findings have broad, general implications for body-form evolution in burrowing vertebrates: whatever constraints have shaped trends in morphological evolution among other squamate groups (excluding Bipes) have been lost in this one exemplary clade. The results of our study join a nascent body of literature showing strong statistical support for character loss, followed by evolutionary re-acquisition of complex structures associated with a generalized pentadactyl body form. [ABSTRACT FROM AUTHOR]

In this article, we identify and analyze a subsea organism to serve as a model for biologically inspired burrowing technology to be used in applications such as anchoring, installation of cables, and recovery of oil. After inspecting myriad forms of life that live on or within ocean substrates, the Atlantic razor clam, Ensis directis, stood out as an attractive basis for new burrowing technology because of its low-energy requirements associated with digging (0.21 J/cm), its speed and depth of burrrowing (∼1 cm/s and 70 cm, respectively), and its size and simplicity relative to man-made machines. As anchoring is a prime application for the technology resulting from this work, the performance of an Ensis directus–based anchoring system was compared to existing technologies. In anchoring force per embedment energy, the E. directus–based anchor beats existing technology by at least an order of magnitude. In anchoring force per weight of device, the biologically inspired system weighs less than half that of current anchors. The article concludes with a review of E. directus’s digging strategy, which involves motions of its valves to locally fluidize the substrate to reduce burrowing drag and energy, and the successful adaptation of E. directus’s burrowing mechanisms into an engineering system: the RoboClam burrowing robot, which, like the animal, uses localized fluidization to achieve digging energy that scales linearly with depth, rather than depth squared, for moving through static soil. [ABSTRACT FROM AUTHOR]

Trade-offs are thought to be important in constraining evolutionary divergence, as they may limit phenotypic diversification. Limbless animals that burrow head-first have been suggested to be evolutionarily constrained in the development of a large head size and sexual head shape dimorphism because of potential trade-offs associated with burrowing. Here we use an acontiine skink ( Acontias percivali) to test for the existence of trade-offs between traits thought to be important in burrowing (speed and force). As head size dimorphism has been shown to be limited in acontiine lizards, thus suggesting constraints on head size and shape, we additionally explore the potential for trade-offs between burrowing and biting. Our data show that A. percivali uses a burrowing style different from those previously described for caecilians and amphisbaenians, which relies on the use of extensive lateral and dorsoventral head movements. Our data also show that animals use their entire bodies to generate force, as peak force was determined by total length only. Additionally, both bite force and the time needed to burrow into the substrate were principally determined by relative head width, suggesting a trade-off between biting and burrow speed. Performance data were indeed suggestive of a correlation between bite force and the time needed to burrow, but additional data are needed to confirm this pattern. In summary, our data suggests that trade-offs may exist, and may have been of crucial importance in shaping the evolution of head shape in A. percivali, and burrowing lizards more generally. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, , 91-99. [ABSTRACT FROM AUTHOR]

Despite many reports of animals using visual landmarks for homing, surprisingly little is known about construction of landmarks for the purpose of orientation. Semiterrestrial crabs normally use a path integration method for short-range homing, but active courtship or territorial behavior may introduce errors increasing predation risk. We explored the hypothesis that male fiddler crab Uca lactea may build structures for landmark orientation to compensate for errors during courtship. Males without burrows found an artificial burrow with a semidome from a greater distance than one without a semidome. In addition, courting males retreated to the translocated semidome rather than to the original burrow location more frequently than noncourting males did. Finally, the maximum traveling distance from the burrow and the maximum deviation of the longitudinal body axis from the home vector were greater in males with semidomes than males without semidomes. Our results strongly support the hypothesis that male fiddler crabs build structures for landmark homing. [ABSTRACT FROM PUBLISHER]

Parasites can be detrimental to the health, longevity, and reproduction of their hosts, but these costs are rarely quantified in nature. We removed ectoparasites and endoparasites from Cape ground squirrels (Xerus inauris), a highly social sciurid in southern Africa. Parasites were removed for 3 months during the dry winter season, when fewer resources are available and the impact of parasites may be greatest. We examined changes in female body mass, reproduction, grooming, and burrow use. Female body mass did not increase with parasite removal, but reproductive success (number of offspring raised to emergence) was nearly 4 times higher for treated females. Rates of allogrooming were lower for treated females, but we were unable to detect a significant change in burrow movements, perhaps because factors other than parasites (e.g., predator avoidance) affect such movements. Gestation and lactation are the most physiologically stressful processes that females undergo, and the dramatic increase in reproductive success in treated females suggests that parasites drain resources that would otherwise be allocated to reproduction. Our results suggest that nonparasitized females put the extra energy into reproduction rather than into their own body weight, which appears to enhance juvenile survival. [ABSTRACT FROM PUBLISHER]

Columbian ground squirrels (Spermophilus columbianus) usually copulate underground in a burrow. Underground copulations might be associated with 2 nonexclusive benefits: reducing probability of predation during copulation and reducing interference by conspecific males. We tested whether either of these benefits was involved in determining if the copulation site was underground or aboveground. In 2006 and 2007, we obtained detailed information on the copulatory behavior and social interactions of free-ranging individuals in southwestern Alberta, Canada. During the 3-week annual breeding period, we also recorded the activity of predators of Columbian ground squirrels such as ravens, foxes, and hawks. Squirrels that lived on the periphery of the population were more susceptible to predation than squirrels in the center. Despite this risk, aboveground copulations usually occurred on peripheral territories. In addition, aboveground copulations were not further removed in time from predator attacks or sightings than underground copulations. Copulations that occurred aboveground were sometimes disrupted by previous mates of the estrous female. Probability that copulation would occur aboveground increased when the density of reproductive males around an estrous female was low. Our results suggest that although underground copulations protect individuals from predation, male--male competition for females and interference with copulations have been more important than predation in determining copulatory sites for Columbian ground squirrels in our study population. [ABSTRACT FROM AUTHOR]

The evolutionary origins of foraging behaviour by procellariiform seabirds (petrels, albatrosses and shearwaters) are poorly understood. Moreover, proximate factors affecting foraging ecology, such as the influence of environment on the development of sensory systems, have yet to be addressed. Here, we apply comparative methods based on current procellariiform phylogenies to identify associations between sensory modalities and the developmental environment that may underlie the evolution of complex foraging behaviour. We postulate that, for burrow-nesting species, smell is likely to dominate the sensory world of the developing chick. Alternatively, for ground-nesting species, chicks receive exposure to a range of visual, auditory and olfactory cues. We employ maximum likelihood to test models of correlated trait evolution between nesting habit and olfactory foraging style and to reconstruct the ancestral states of these characters when coded as binary states. Our results suggest that nesting behaviour has evolved in conjunction with foraging style. Based on this analysis, we propose that nesting on the surface was a life-history innovation that opened up a new developmental environment with profound effects on the foraging ecology of procellariiform seabirds. [ABSTRACT FROM AUTHOR]

The importance of predation and burrow digging in explaining the evolution of sociality is generally unclear. We focused on New World hystricognath rodents to evaluate three key predictions of the predation hypothesis. First, large-bodied surface-dwelling species will be more vulnerable because they are more detectable; thus sociality should be associated with body size. Second, surface-dwelling, diurnal species would be more vulnerable to predators than nocturnal species; thus sociality should be associated with the evolution of diurnality. Third, species living in open habitats will be more vulnerable; thus sociality should evolve in species living in open habitats. Regarding the importance of burrows, we tested if species that dig burrows can benefit from communal labor; thus, sociality should be associated with burrow digging. All traits had significant phylogenetic signal, thus comparative analyses should explicitly address this. In a comparative analysis on independent contrasts we found that sociality was correlated with body size (larger species were more social), diurnality (diurnal species were more social), and burrowing (burrowing species were more social), but we found no effect of overhead plant cover of habitat on sociality in hystricognath rodents. Somewhat different results were found when we analyzed the raw data. Taken together, our results provide support for a link between predation risk, burrow digging, and sociality in this group. [ABSTRACT FROM AUTHOR]

Presents a study that examined the effects of plateau zokors, a kind of burrowing mammal, on seasonal aboveground and belowground plant biomass, plant species diversity, and soil moisture and organic matter in an alpine meadow site in Qinghai Province, People's Republic of China. Background on small burrowing mammals; Materials and methods; Results of the study.

Presents a study that examined climatic factors as possible determinants of burrow architecture and portal orientation in red viscacha rat found in Argentina. Background on the red viscacha rat; List of climatic factors examined; Materials and methods used; Results.

The article provides information on a research examining the biotic interactions, particularly the burrowing abilities, of Donax serra Sillwyn (D. serra) and D. Sordidus Hanks on a dissipative beach in South Africa. Observations suggested that burrowing in both species is only inhibited significantly at extremely high densities of the larger species, D. serra. Meanwhile, burial times in both species increase with size but decrease with temperature.

The burrowing behaviour of the bivalve Mya arenaria from tidal flats of the Dutch Wadden Sea has been observed and recorded. Compared to other bivalves, M. arenaria is a very slow burrower, its burrowing behaviour being unique among bivalves since it is based essentially on the ejection of water through the pedal gape, with little assistance by the foot, which performs only an anchoring function. Water ejection is specially powerful and individual jets may last several seconds, thus constituting an effective means of removing sand from below the animal during digging. This hydraulic burrowing is more effective in loose sandy than in cohesive muddy substrates. Water ejection is provided by the ability of the bivalve to rock its valves across a dorsoventral axis. This rocking motion implies special modifications of the ligamental area. The ligament is conical in appearance and runs dorso-ventrally between the two chondrophores which are placed in two planes parallel to the cardinal axis. During rocking the whole ligament acts in torsion and the lamellar layer of the ligament opposes closing of the anterior part of the valves. During normal adduction of the valves the ligament acts in bending, the axis of motion being placed internally with respect to the cardinal axis. This leads to approaching of the umbones with complete adduction and to resorption of the left umbo. From the adaptive point of view, the slow hydraulic mode of burrowing is sufficient to cope with the slow sedimentation and erosion rates of the tidal flats in which M. arenaria lives. This burrowing mode implies the existence of a tiny foot, which leaves room for other organs within the mantle cavity. This, together with anterior divarication of the valves permits a large volume of water to be ejected from the mantle cavity, but, in the case of M. arenaria, also the existence of an enormous stomach, possibly as an adaptation for food processing. [ABSTRACT FROM AUTHOR]