Burrow Depth Research Articles

Seasonal and depth-dependent thermoregulatory benefits of burrows for wombats – the largest burrowing marsupials.

Mammals use burrows to behaviourally thermoregulate, save water and avoid predation. The advantages of burrows vary not only seasonally but also with burrow depth. To quantify these effects, we used biophysical ecological models, which predict an animal’s energetic and hydric costs within a characterised microclimate. For Australia’s three extant wombat species we quantified variation in the energetic advantage of burrows spatially, temporally, and with burrow depth. We simulated resting wombats with different traits (e.g., body size, fur) in different microclimates (above ground and burrows of varying depth) at six sites across Australia, two for each wombat species, over five years (1980, 1990, 2000, 2010, 2020). We assessed time spent within their thermoneutral zone—heat production equals heat loss thus minimising energy and water expenditure —and frequency of extreme heat stress (i.e., no viable hydric solution for the conditions stipulated). Our findings show that burrows are essential for reducing energetic and hydric costs and for survival during the hottest season in areas with no shade, e.g., the semi-arid zone. We found no evidence that extreme heat stress has increased temporally i.e., due to climate change, but it was frequently predicted in shallow burrows in 2020, having rarely been previously forecast. For energy requirements, we found lower thermoregulatory costs for deeper burrows in the cold season and for shallow burrows in the hot season. This work underscores the critical balance between wombat survival, burrow utility, and environmental dynamics, offering new insights into mechanisms that dictate mammal behaviour from a thermoregulatory perspective.

Atypical holocene ctenomyid rodent burrows related to eolian dune deposits from central Argentina

This contribution aims to interpret the producers and the paleoenvironmental context of Holocene rodent burrows (and associated ichnofossils) from the Late Pleistocene-Holocene Meaucó Formation, central La Pampa Province, Argentina. Fieldwork included a detailed sedimentary logging, a ground penetrating radar survey and documentation of the fossil burrow systems. The Meaucó Formation rest on erosive unconformity over the Upper Miocene-Lower Pliocene Cerro Azul Formation and display a vertical change from eolian dunes that become sparser up section (as imaged by ground penetrating radar) and were capped by a paleosol. The paleosol is covered by recent eolian dune and interdune deposits. The fossil rodent burrows occur up to 1.7 m below the paleosol and share several morphologic features with modern Ctenomyidae burrows, except the high slope of entrance and internal ramps, and the maximum depth of burrows. To explain these differences, it is proposed that the burrows were excavated by ctenomyids in ancient sloping surfaces of eolian dunes, which resulted in increased inclination and apparent maximum depth of the systems. This is an example of influence of environmental conditions on the architecture of rodent burrows, and can be of help when interpreting other similar fossil examples. The paleosol community associated with the fossil vertebrate burrows also included other organisms recorded by their trace fossils: horses (Hippipeda isp.), a scrubby vegetation (rhizoliths), coleoptera or spiders (Skolithos linearis), cicada nymphs (Feoichnus challa) and ants (Daimoniobarax isp.).

The correspondence between the physiological cold tolerance and the distribution border of Mediterranean sandflies in Southeast Europe.

The distribution of sandflies is influenced by several climatic factors, like winter temperature limits, summer humidity, and drought. Only a few studies were performed to search for the connection between the physiological tolerance of sandflies and the result of the Climate Envelope Models projected distribution borders. It was studied how the depth of rodent burrows could determine the occurrence of five European Phlebotomus species based on their known physiological cold tolerances. The modelled distributions based on the monthly minimum temperatures showed notable differences by soil depth and species. The observed and modelled European distribution areas of sandflies according to - 20 cm soil depth showed good coincidence with the observed occurrences of Phlebotomus neglectus , Ph. papatasi , and Ph. perfiliewi in East-Central, Southeast, and East Europe. Also, a good coincidence was found in the case of the modelled and observed occurrences of Phlebotomus perniciosus in Western Europe. It can be concluded that in their north-eastern distribution borders, sandflies can overwinter in rabbit and rodent burrows at depths of - 20 cm below the surface. The physical cold tolerance of Ph. ariasi could be underestimated. In more than - 50 cm of depth, the stable and continuously cold environment of the shelters (mean temperature less than 10°C) could inhibit the post-winter diapause activation of sandflies in the northern regions.

Behavioural flexibility in Lumbricus terrestris burrowing

Lumbricus terrestris is an epi-anecic earthworm, normally occupying a 1–2 m deep, vertical burrow. Some observations suggest that population persistence in much shallower burrows could be possible in a mild and humid climate. This was further investigated at an ex-industrial site in NW England, with a topsoil less than 0.15 m deep, above inert subsoil formed from semi-weathered Leblanc waste. L. terrestris were collected from an adjacent woodland soil and introduced into unoccupied areas. After four days, settlement and survival were studied by targeted sampling of half of the individuals, and depth of burrows were measured by resin casting. After 14 months, the second half of inoculated areas were studied and after another four years a further general survey occurred. After four days, 41 % of targeted worms were recovered, with 0.11 m mean burrow depth and burrows ending at the subsoil interface. After 14 months, all age classes of L. terrestris were present and burrow depth had not changed. After five years, adult, juvenile and hatchling L. terrestris were present, demonstrating establishment of a breeding population. In a parallel laboratory experiment, with site topsoil and subsoil in Evans’ boxes, L. terrestris avoided subsoil and constructed U-shaped burrows. The results show that through flexible burrow construction, L. terrestris can survive above highly constraining subsoil conditions. This is likely to be only possible where severe droughts are uncommon, and topsoil does not freeze in winter.

Non-invasive (georadar) investigation of groundhog (Marmota monax) burrows, Pennsylvania, USA

Zoogenic impact plays a critical role in stream processes, especially bank stability and resulting channel dynamics. This study focuses on bioturbation by groundhogs (Marmota monax) along the riparian zone of Mill Creek (Bucks County, Pennsylvania, USA). Several complexes comprising at least 32 active burrows (average diameter: 25.9 cm) were geolocated, with morphometric measurements obtained at selected sites. Two networks were imaged using high-frequency 800 MHz ground-penetrating radar (GPR) and included: 1) a grid of parallel 3-m-long transects on the south bank, and 2) an 11-m-long profile on the north bank. Post-processed electromagnetic signal traces (A-scans) comprising 2D radargrams (B-scans) revealed voids as reverse-polarity anomalies (hollow inclined shafts and tunnels), allowing for a general assessment of burrow depth and orientation. At the southern cutbank site, a large burrow had an entrance diameter of 0.3 m and a westerly dip. A sloping tunnel section was detected at ~0.5 m depth, based on the geometry of point-source (transverse) hyperbolic diffractions corresponding to the roof and a floor ‘pull-up’. The second locality traversed three open burrow entrances adjacent to large tree roots. This survey along a tributary channel shows multiple hyperbolics below adjacent openings, with the latter showing the characteristic signal ‘breakout’. GPR data show hyperbolic signatures ~0.3–0.4 m below the ground surface. Along this transect, burrowing activity appears to increase with proximity to the northern bank of Mill Creek. An example of a depth slice (bedding-plane view) from a nearby riverbank demonstrates the potential for 3D visualization (C-scans) of burrow networks using a grid of closely spaced GPR profiles. Groundhog burrows constrain maximum long-term level of the groundwater table and serve as important zoogeomorphic structures in diverse ecotones, including developed landscapes. Abundant evidence of bank slumping, incision, and treefall suggests that burrowing activity likely weakens root systems and enhances groundwater flow, thereby initiating or accelerating geomorphic cascades leading to slope failure.

Understanding the ability of Pachycrepoideus vindemiae (Hymenoptera: Pteromalidae) to find and parasitize buried Diptera pupae in southwestern Colombia

Pachycrepoideus vindemiae is a generalist wasp parasitoid released for biological control of the pupal stage for several species of Tephritoidea and Muscoidea flies that limit production of fruits and poultry commodities, respectively, worldwide. The parasitoid wasp must find buried host pupae to oviposit on them, and several factors may influence this outcome. The objectives of this study were to determine the capacity of first, host larvae to burrow to pupate according to substrate humidity and second, the parasitoid wasp to burrow and parasitize buried host pupae according to different conditions (substrate type, host species and parasitization time exposure). Moreover, comparison of chemical profiles between host’s pupae potentially involved for host location by the parasitoid was realized by GC-FID. Peat humidity significantly affected the burrowing depth of Dasiops inedulis and Anastrepha striata and both species buried significantly deeper in peat with 50% humidity than in dry conditions. The number of emerged parasitoids is not different between the two tested host species. P. vindemiae performance was better in peat than in crop soil. In peat wasps’ parasitism is similar between buried pupae located at 0 mm or 10 mm depth regardless of the time of exposure to the parasitoid. Cuticular chemical profiles showed that the four-host pupa species studied did not share compounds. However, A. striata shared some compounds with D. inedulis and, M. domestica shared some with C. capitata. Common compounds were found in the extracts of parasitized and non-parasitized pupae of C. capitata, D. inedulis and M. domestica.

Influence of Temporal Variation on Morphology and Architecture in Burrows of Ocypode Rotundata (Miers, 1882) on Salakh Beach of Qeshm Island, the Persian Gulf

Variability over time in morphology and architecture of burrows excavated by Ocypode rotundata was studied on Salakh beach, Qeshm Island, Persian Gulf. According to our results, O. rotundata excavated single Shafts, J-shaped, Y-shaped, spiral and complex burrows, with spiral and complex burrows occurring only in adult crabs. The results showed that mating and reproduction behaviour of O. rotundata mainly occurred in the upper foreshore zone. Based on carapace width data and sex, percentage of J-shaped and Y-shaped burrow were more in female young crabs compared to males. Whilst, percentage of constructed single Shaft, J-shaped burrows were more frequent in male adult crabs compared to females. On the other hand, created complex burrow was observed just in male adult crabs. Also, male crabs created sand pyramid mounds seaward in front of the burrows. Four types of sand disposal behaviour were observed: knocking, throwing, slamming (only males) and stacking (only males). Results indicated that O. rotundata constructed burrows with any shape in all types of sediment, from the backshore to the foreshore. Sand moisture decreased with distance from the sea, which was associated with an increase in burrow depth. Temporal variation had significant impact on burrow slope, so that the entrance branch of all burrow shapes was clearly steeper during the reproduction period in contrast to the same burrows created in the non-reproduction period.

3D X-ray analysis of the subterranean burrowing depth and pupal chamber size of Laricobius (Coleoptera: Derodontidae), a specialist predator of Adelges tsugae (Hemiptera: Adelgidae).

The non-native hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), has caused a significant decline of eastern hemlock, Tsuga canadensis L. (Pinales: Pinaceae), and Carolina hemlock, Tsuga caroliniana Engelmann (Pinales: Pinaceae), in eastern North America. Biological control of HWA has focused on the use of 2 Laricobius spp. (Coleoptera: Derodontidae), natural predators of HWA, which require arboreal and subterranean life phases to complete their development. In its subterranean phase, Laricobius spp. are subject to abiotic factors including soil compaction or soil-applied insecticides used to protect hemlock from HWA. This study used 3D X-ray microcomputed tomography (micro-CT) to identify the depth at which Laricobius spp. burrows during its subterranean lifecycle, characterize pupal chamber volume, and determine whether soil compaction had a significant effect on these variables. The mean burrowing depth in the soil of individuals was 27.0 mm ± 14.8 (SD) and 11.4 mm ± 11.8 (SD) at compaction levels of 0.36 and 0.54 g/cm3, respectively. The mean pupal chamber volume was 11.15 mm3 ± 2.8 (SD) and 7.65 mm3 ± 3.5 (SD) in soil compacted at 0.36 and 0.54 g/cm3, respectively. These data show that soil compaction influences burrowing depth and pupal chamber size for Laricobius spp. This information will help us better identify the effect of soil-applied insecticide residues on estivating Laricobius spp. and soil-applied insecticide residues in the field. Additionally, these results demonstrate the utility of 3D micro-CT in assessing subterranean insect activity in future studies.

Burrow morphology of ghost crab <i>Ocypode stimpsoni</i> on Ikarashi beach, Niigata, Japan

Lack of evidence prevents an understanding of how ghost crabs create burrows underground. For the reconstruction of ichnogenetic stages in the burrows of ghost crabs, we report on how the burrows of the ghost crab Ocypode stimpsoni from the foreshore and backshore on Ikarashi beach, Niigata, Japan are created. Plaster casting of the burrows reveals detailed morphology with bioglyphs on the burrow wall. The casts of burrows show a variety of morphologies, such as J- and Y-shapes. Based on the burrow ichnogeny, J-shaped burrows were well constructed at a shallower level of the waterline underneath the beach, occasionally creating a second opening of the burrow. In turn, Y-shaped burrows were constructed at a deeper waterline, thereby recycling and reburrowing the deepest part of the J-shaped burrow. As a result, the total depth of Y-shaped burrows tends to be larger than that of J-shaped burrows. The depth and mean diameter of the burrows range from 3.3–37.6 cm and 9.28–31.54 mm, respectively, and the depths are apparently shorter than those on a Pacific beach. The lines of evidence suggest that the morphological features of burrows in Ikarashi beach are attributed to a smaller difference in tidal level in the Sea of Japan, where the available space for burrows ought to be limited by the waterline under the ground.

Effects of bioturbation by the fiddler crabLeptuca speciosa(Ives, 1891) (Decapoda: Brachyura: Ocypodidae) on mangrove peat in Barnes Sound, Florida, USA

AbstractBioturbation, which includes burrowing and foraging behaviors, is an important component of the functional role of fiddler crabs (Brachyura, Ocypodidae) within mangrove forests because it modifies sediment properties and composition of mangrove substrates. In this study, fiddler-crab population density and burrow architecture were measured to evaluate the influence of bioturbation by the fiddler crab Leptuca speciosa (Ives, 1891) on mangrove peat from Barnes Sound, Florida, USA. Measurements of burrow architecture were used to estimate the contribution of fiddler-crab burrowing to the bioturbation of mangrove peat. Comparisons were made between the total organic matter in bioturbated sediments, including feeding and burrowing pellets. A population density of 12 burrows m–2 was measured with no significant trends in the spatial distribution of fiddler crabs within the site. Although the deepest burrow depth was 18 cm, results show the upper 5 cm of the peat surface was consistently burrowed by crabs. Fiddler crabs were estimated to increase the total below-ground air-peat surface area m–2 by 5% and accounted for 22% of the excavated volume of mangrove peat per year. Fiddler crabs will thus rework the entire peat substrate within five years. Because data on carapace geometric mean size suggested that a juvenile population of L. speciosa was sampled, the bioturbation rate of the peat substrate will accelerate once this population matures. Feeding pellets had significantly lower percentages of total organic matter (P < 0.01) than other bioturbated peat samples, suggesting that fiddler-crab foraging behaviors significantly (P < 0.01) decrease the organic composition of surficial peats. These results imply that fiddler crab burrowing extends the depth of the taphonomically active zone thus enhancing mangrove peat decomposition and changing the bioavailability and distribution of organic matter in mangroves.

Effects of fine-scale habitat quality on activity, dormancy, habitat use, and survival after reproduction in Rana dybowskii (Chordata, Amphibia)

Amphibians are facing population declines and extinctions, and protecting and supplementing refuges can help species survive. However, the microhabitat requirements of most species are unknown, and artificial shelters or burrows have not been well tested for amphibians. Some amphibians exhibit complex behaviour during the transition from post-reproductive dormancy to activity. However, little is known about the ecology, post-reproductive dormancy, and terrestrial activity of amphibians. Here, habitat site selection in experimental enclosures and the effects of shelters (stones, soil) and shade (with and without shade netting) on the activity, exposed body percentage, burrow depth, body-soil contact percentage, and survival of Rana dybowskii were investigated during post-reproductive dormancy and post-dormant activity. The results showed that R. dybowskii live individually under leaves, soil, stones or tree roots. Furthermore, although the dormant sites of frogs are significantly different, the distribution of male and female frogs in these sites is similar. Shading and shelter significantly affected the exposed body percentage, burrow depth and body-soil contact percentage of frogs compared with soil. In the stone group, soil and stone form the frog's refuge/burrow, whereas in the soil group, the refuge/burrow is composed entirely of soil. Even though the soil group has a deeper burrow and a larger area of soil contact with the body, it still has a higher exposure rate than the stone group. Frog activity frequency was affected by shelter and shade; the interaction of shelter and time and the interaction of shading and time were significant. The soil group had a higher activity frequency than the stone group, and the no-shade group had a higher activity frequency than the shade group. Shelter and shading differences do not significantly affect frog survival; however, the death rate during post-reproductive dormancy is lower than that during the active period.

Mammillichnis monstrum isp. nov., a new sea anemone trace fossil from the Carboniferous of the Donets Basin, Ukraine

A new ichnospecies Mammillichnis monstrum isp. nov. (Domichnia) is described from turbidite sandstone in the upper part of the Mospyne Formation (late Bashkirian, Early Pennsylvanian) of southern Luhansk Oblast, eastern Ukraine. Mammillichnis monstrum isp. nov. is represented by hypichnial, hemispherical, slightly flattened passive fillings of a large burrow; the apex of burrow casts has concentric depression or a small rounded tubercle. Mammillichnis monstrum isp. nov. differs from Mammillichnis aggeris Chamberlain, 1971 (Vendian–Oligocene) and Mammillichnis jakubi Pokorny et al., 2017 (Late Miocene, Neogene) by its much larger size. The depth of burrows varies greatly, which seems to be related to the different preservation of burrow casts, as well as, apparently, different maturity of burrow producers. In addition, such an important diagnostic feature as a rounded tubercle at the apex of the burrow casts is not observed in all specimens, which is probably also due to the different types of preservation of the trace fossils. Perhaps, the differences in the morphology of the apex of some examined specimens are due to the activity of organisms that lived in the burrows after the death of the trace fossil producer. The producers of the trace fossils Mammillichnis are apparently sea anemones (Actiniaria). The fossil record of Actiniaria has significant gaps because these animals lack a mineral skeleton that can be preserved as a fossil. The oldest sea anemones are known from the Vendian; there is no data on post-Carboniferous fossil Actiniaria. It seems that the only way to study the evolution of this group of animals is studying of their trace fossils, such as burrows (e.g. ichnogenera Astropolichnus, Bergaueria, Conostichus, and Kulindrichnus), which demonstrate some details of the body morphology of their producers. The trace fossils Mammillichnis monstrum apparently marks insignificant pauses in sedimentation preceding the accumulation of turbidite sandstones. In the coarse sandy sediments are preserved mainly large depressions left by sessile coelenterates. Trace fossils are well preserved in some sandstone lenses and poorly preserved in others. This circumstance is apparently related to the different intensity of erosive activity of turbidity currents.

Burrow behaviour, structure and utilization of the amphibious mudskipper Periophthalmus chrysospilos Bleeker, 1853 in the Mekong Delta

Burrows of fishes are important to their creators, but knowledge of burrowing behaviour, structure and utilization are poorly understood. We report the burrowing behaviour of the amphibious mudskipper, Periophthalmus chysospilos, from estuarine and coastal sites within the Mekong Delta (Vietnam). Activities at and around the burrow were observed over 12 months (April 2020 to March 2021). Burrow casts were recovered monthly to determine burrow structure and utilization in this species. Observations revealed that males excavate burrows with their mouths during the ebb tide. Burrows were J-, Y- and U-shaped, with 1–2 openings to the surface and a bulbous egg chamber. The burrow depth (BD) and total length (BL) varied with shape and site, but not season. The BD and BL ranged from 15.1 ± 0.9 to 18.6 ± 0.80 SE cm and from 22.1 ± 1.2 to 25.7 ± 1.0 SE (standard error of mean) cm, respectively. These results provide insights into the burrowing ability and better understand the ecology of these fishes in the Mekong Delta.Running head: Burrow behaviour, structure and utilization of Periophthalmus chrysospilos.

Crab contributions as an ecosystem engineer to sediment turnover in the Yellow River Delta

Burrowing crabs are widely distributed and have large populations in estuarine wetlands. Crab excavation can have potentially significant bioturbation effects on the vertical structure of sediments, and the processes of nutrients deposition and mineralization. However, the effects of crab micro activities on the geochemical cycling processes of the whole estuarine ecosystems are not clear, specifically the contributions of burrowing crabs to sediment and nutrients turnover in coastal ecosystems. Due to the lack of knowledge on crab burrowing behavior and borrow morphology, it is difficult to accurately estimate the excavation and turnover volumes of crabs. Therefore, this study examined the bioturbation activity of the crab Helice tientsinensis in western Pacific estuary ecosystems by analyzing their burrow morphology and local sediment properties. The common burrow shapes of Helice tientsinensis were J- and Y-shaped burrows. Burrow morphological characteristics such as total burrow depth, curve burrow length, burrow volume, and opening diameter significantly differed among tidal zones. Crab carapace size, water depth, soil hardness, and bulk density were the main factors driving burrow morphology. Sediment excavation by crabs was ~50 times greater than the deposition of sediment into crab burrows. The net transported amounts of sediment (31.66–33.18 g·d-1·m-2) and nutrients (total nitrogen: 0.075–0.090 g·d-1·m-2, total carbon: 3.96–4.55 g·d-1·m-2, and organic matter: 0.44–0.77 g·d-1·m-2) were mainly from the belowground sediment to the surface. These results highlighted the important role of crabs in sediment and nutrients cycling within coastal estuary ecosystems.

Seagrass density correlates with burrow abundance and size in the Zebra Mantis Shrimp (Stomatopoda: Lysiosquillidae)

Introduction: Mantis shrimps are ecologically and economically important organisms in marine ecosystems. However, there is still a lack of information about their habitat, in particular, their burrows. Objective: To analyze how dense and sparse mantis shrimp burrows differ in abundance, size, sediment grain size, and water quality. Methods: We counted burrows in 10 x 10 m2 random plots in sparse and dense seagrass (ten plots per density), around Barrang Lompo Island, South Sulawesi, Indonesia. Sampling took place at spring low tide from August to September 2017. Results: Two mantis shrimp species were observed: Lysiosquillina maculate and L. sulcata. Dense and sparse seagrass burrows did not differ in wall grain size or water parameters, both inside and outside of the burrows (P > 0.05). Similarly, there was no correlation between burrow depth and diameter in either dense (P > 0.05; r= 0.27) or sparse (P > 0.05; r= 0.33) seagrass. However, larger burrows tend to occur in denser beds, but there were more burrows in denser seagrass (t-test, P < 0.05). Conclusions: There seems to be a preference for dense seagrass beds, especially by larger mantis shrimps. The correlation between shrimp burrow abundance and seagrass density highlights the importance of conserving the quality as well as the extent of seagrass habitat.

Repeated computed tomography scanning reveals morphological development of burrows produced by the tiger pistol shrimp Alpheus bellulus.

The burrow morphology of endobenthic organisms reflects their subsurface ecology. In this study, we observed the three-dimensional development of burrows produced by the tiger pistol shrimp Alpheus bellulus in a tank using an X-ray computed tomography (CT) scanner. CT scanning was performed at 10–30 min intervals immediately after the start of burrow construction. The three-dimensional morphology (surface area, volume, depth, length, and diameter) of burrows at each observation time was imaged and measured. In addition, the rate of increase of each parameter was calculated. Surface area, volume, length, and depth rapidly increased immediately after the start of the experiment in all burrows. Subsequently, there was a reduction in the rate of increase at 40 min after the start of excavation for burrow depth, at 75 min for length, and at 90 min for surface area and volume. Although there were large differences in burrow diameter among the burrows immediately after the start of the experiment, all burrows reached nearly identical diameters after 90 min. Changes in burrow morphology were not observed in most of the burrows more than 210 min after the start of the experiment, meaning that A. bellulus can create burrows that are sufficient for survival within this time period. The use of CT scans in this study clarified the developmental process of the three-dimensional structure of A. bellulus burrows and is applicable to various burrow-producing organisms. Our results provide new insights into the development of burrow structures.

Climate change and Arenicola marina: Heat waves and the southern limit of an ecosystem engineer

In asking how ecosystems will change with the forces of climate change, one approach is to identify the biotic forcing functions and focus on the ecologically dominant species, because as those species are affected, results will cascade through the system altering components such as biological diversity. Given the status of A. marina as an important ecosystem driver, it is of interest to ask how increasing temperatures will impact its distribution. The literature strongly suggests that the period during which it is most susceptible is late summer when the metabolic load of gametes is maximal and sediment temperatures at burrow depth during low tide are likely to exceed 25 °C. We used the probability of occurrence of fatal heat waves that penetrate to animal burrow depth as a primary factor in our modeling of past, present and future climates and the distribution of A. marina. Modeled sediment temperatures were validated against in situ temperature logger data and then used to develop the relationship between August SST and the occurrence of fatal heat waves to enable use of SST data directly. Modeled thermal gradients corresponded well to high resolution remotely sensed temperatures along the French and Iberian coasts and to distribution shifts in A. marina, known both from the literature and field surveys done by the authors in 2005–2014. Model hindcasts suggest that published occurrences of A. marina within the Mediterranean after 1860 except within the Gulf of Lions are unlikely. Given the known sensitivity of A. marina to anaerobiosis during heat waves, particularly when ripe, the forecasts based on CMIP6 25 km scale ocean models all predict the complete disappearance of A. marina from the Mediterranean and restriction to the upwelling zone on the western margin of Iberia and to the Atlantic coast of Europe north of 45°N with the suggestion of more limited populations in the English Channel and perhaps into the Wadden Sea. These biogeographic shifts will likely cause fundamental changes in ecosystem function along the coasts of Iberia, France, UK, and perhaps into Belgium and the Netherlands.

Factors Affecting Burrow Architecture of the Polychaete Perinereis Aibuhitensis

Bioturbation of infauna plays an important role in the biogeochemical processing of sediments. Infaunal animals build burrows and enlarge the sediment-water interface by their activities and so bioturbation is closely related with burrow structure and animal behavior in the sediment. The purpose of this study is to explore the characteristics of Perinereis aibuhitensis burrow structures with the factors of months and animal sizes (0-1g, 1-2g, 2-3g, 3-4g, and >4g), which would also provide useful knowledge of infauna behavioral ecology. The dimension and complexity of the burrows of P. aibuhitensis were measured by dissecting sediments. The results showed that there were three burrow shapes of P. aibuhitensis, i.e., I, Y and U shapes. Overall, the order of abundance of each of the three burrow shapes were I > Y > U. Larger P. aibuhitensis are inclined to build Y- and U-shaped burrows in June and August. There were significant differences in the tunnel diameter, burrow depth and burrow length separately between different polychaete size classes (P< 0.001). In February and August, the burrow depths and burrow lengths of P. aibuhitensis individuals with body weights of 1-2 g and 2-3 g were significantly greater than in other months (P< 0.001). P. aibuhitensis individuals of 1-2 g and 3-4 g body weight had significantly more burrow openings and branches in August than in February (P< 0.001). Within the same month, the burrow HEindex increased with increasing polychaete size, and when the sizes were 1-2 g, 2-3 g and 3-4 g, the complexity in August was higher than that in other months. This study suggests that I-shaped burrow dominants the burrow architecture of P. aibuhitensis. The polychaete with large size has a higher HEindex (burrow complexity) indicating a strong bioturbation ability. Y-shaped burrows are more conducive to the survival of P. aibuhitensis in hot weather. In order to adapt to environmental stresses outside, P. aibuhitensis usually builds deeper burrows.

Hayalet yengeç Ocypode cursor (Linnaeus, 1758) yuvalarının insan etkileri altında morfolojik değişimleri

Ghost crabs are common bioindicator species for human disturbance on sandy shores. Ghost crabs often alter their population dynamics under human disturbance. Ghost crabs, further, alter their burrowing behavior under human influence, however, these changes are not well known on the Turkish coast of the Mediterranean Sea. Therefore, burrowing morphology of Ocypode cursor at two sites that differ in the degree of human disturbance was compared. Ghost crabs created smaller, steeper and simpler burrows at the site under higher human disturbance compared to the crabs living at the sites with lower human influence. Further, there was no difference in the ghost crab burrow depth and the frequency of existence of chambers between sites. Moreover, the results of this study revealed that larger crabs preferred higher parts of the beach at both sites, suggesting that this is a common behavior for the populations of O. cursor. Consequently, the results of this study emphasized that O. cursor alter their burrowing morphology and characteristics under human disturbance besides their population demographics; suggesting that studies that focus on the use of ghost crabs for human disturbance should include burrow morphology in their assessments.

Burrow Characteristics and Habitat Associations of Gopher Tortoises in Urban Pine Rockland Reserves (Miami, Florida, USA)

The Gopher Tortoise is a keystone species and a species of conservation concern in the southeastern United States, but the biology of tortoises at the extreme southeastern limit of the range is poorly understood. We examined physical characteristics and habitat associations of Gopher Tortoise burrows in pine rockland natural preserves in the highly urbanized Miami-Dade County (Florida, USA). We measured width, depth, and orientation of burrows at two sites. We compared a suite of 11 habitat features (e.g., canopy cover, understory density, ground cover, soil depth, and soil compaction) at random points and at Gopher Tortoise burrows in each of the two sites. Burrow widths were similar between sites and included burrows of both adults and juveniles—evidence that both populations are reproducing. Burrows were very short (most <2 m) compared to burrow lengths reported from other sites (>4 m), likely because soil depth is very shallow in extreme south Florida. We used multidimensional scaling and analysis of similarity to detect differences in habitat variables among sites, among point types (random points and burrows), and between active and inactive burrows. Low leaf litter cover, high grass cover, low canopy cover, and deep soil were among the major variables associated with all burrows and active burrows. The habitat associations of the burrows were similar to studies from other areas, yet the short burrows and association with the deepest available soils appear to be a strong response to the unique geology of pine rockland habitats. We discuss vegetative associations of Gopher Tortoises in the context of management in urban natural areas and implications for protection of Gopher Tortoises at the southern limit of their geographic range.