Sinusichnus, a trace fossil from Antarctica and Venezuela: expanding the dataset of crustacean burrows

The sinusoidal decapod crustacean burrow Sinusichnus sinuosus is documented from the Upper Cretaceous Hidden Lake Formation of James Ross Island (Antarctica), the Upper Oligocene-Lower Miocene Naricual Formation of the Eastern Venezuela Basin, and the Middle Miocene Socorro Formation of the Falcón Basin of Western Venezuela, significantly expanding its geographical and palaeolatitudinal range. These burrows may have served for bacterial farming in relatively stressful settings characterized by deltaic progradation. Sinusichnus sinuosus seems to display a broad latitudinal range, from low latitude tropical settings (Venezuela) to intermediate latitude temperate areas (Spain and France), and high latitude cold waters (Antarctica). The appearance of S. sinuosus in the Cretaceous reveals the acquisition of more sophisticated feeding strategies by decapod crustaceans, reflecting the dominance of the Modern Evolutionary Fauna.     

Paleoecology of the Zoophycos producers

Kotake, Nobuhiro 1989 07 15: Paleoecology of the Zoophycos producers. Lethaia , Vol. 22. pp. 327–341. Oslo. ISSN 0024–1164.
Well-preserved Zoophycos and Spirophyton- like burrows occur in the Upper Pliocene deep-sea sediments exposed along the southern coast of Boso Peninsula, central Japan. They consist of an axial tunnel and helically coiled spreite with fecal pellets. In most cases the two kinds of trace fossil are found separately. In several complete specimens, however, the upper and lower portions represent a Spirophyton- like burrow and Zoophycos , respectively. The downward increase in size of the spreite and fecal pellets in a single burrow suggests that the complete Zoophycos was built successively as the producing animal grew. The occurrence of incomplete Zoophycos may have resulted from post-mortem destruction by echinoid locomotion and turbidity currents. In some cases, the uppermost portion of the axial tunnel is covered with a thin tuff layer. Fecal pellets in such burrows consist of the same tuffaceous material which must have originated from the overlying tuff layer. This fact indicates that the burrow producer did not feed on organic matter within the sediments but foraged detritus on the sea floor. The animal could probably stretch a part of the body from the top of the axial tunnel for feeding and systematically pack the fecal pellets into the sediments. Such segregation between the feeding place and the excretory space is interpreted as an efficient feeding strategy for the detritus-feeding burrowers in the deep sea. D Zoophycos, Spirophyton-like burrow, paleoecology, feeding and excretory behavior, Boso Peninsula, Japan .     

New Insights into Polychaete Traces and Fecal Pellets: Another Complex Ichnotaxon?

Neoichnological observations help refine paleoichnological records. The present study reports extensive observations on the distribution, morphology, occurrence and association of burrows and fecal pellets of the polychaete Nereis diversicolor in the Kundalika Estuary on the west coast of India. Our holistic study of these modern-day traces suggests it to be a complex trace arising from domichnial, fodinichnial and possibly pascichnial behavior of polychaetes. The study for the first time reports extensive fecal pellet production, distribution and their preservation as thick stacks in modern estuarine environment. These observations testify the fossilization potential of pellets and provide an explanation to their origin in the geological record. Their occurrence as strings associated with mounds not only suggests pascichnial behaviour of polychaetes but also allows the assignment of post-Paleozoic Tomaculum to the activity of polychaete worms. The production of fecal pellets in such large quantities plays a major role in increasing the average grain size of the substrate of these estuarine tidal flats, thereby improving aeration within the substrate.     

Burrow construction and behavior of tilefish,Lopholatilus chamaeleonticeps,in Hudson Submarine Canyon

Synopsis During 22 daylight submersible dives in August 1979 numerous juvenile and adult tilefish, Lopholatilus chamaeleonticeps, were observed in and around vertical burrows in the clay substrate of portions of Hudson submarine canyon in depths from 110–230 m. The size and shape of the burrows varied considerably with the smallest juveniles occupying simple vertical shafts in the substrate. Larger fish were found in much larger burrows (up to 4–5 m in diameter and at least 2–3 m deep) that were funnel shaped in cross-section with the upper conical portions containing numerous smaller burrows of associated crabs. The range of burrow sizes observed suggests a regular sequence of burrow construction by tilefish and the associated crabs. Both juvenile and adult tilefish swam into the burrows head first and exited tail first. This behavior, which would preclude the possibility of ambushing prey, and evidence of predation by sharks and other tilefish, suggests that the burrow is a refuge from predators.Tilefish burrows appear to serve as a focus for biological activity. Species associated with the burrows included galatheid crabs, Cancer sp., Acanthocarpus alexandri, Homarus americanus, Heliocolenus dactylopterus and Conger oceanicus. Tilefish may play an important role in structuring outer continental shelf communities. They physically shape their environment and probably have significant biological interactions with the species that associate with their burrows.     

The crustaceans burrow Sinusichnus sinuosus from the Oligocene-Miocene carbonate deposits of eastern Amazonia

Abstract

Sinusichnus Gibert 1996 Gibert, J. M. d. 1996. “A New Decapod Burrow System from the NW Mediterranean Pliocene.” Revista Española de Paleontología 11: 251–254. [Google Scholar] is recorded for the first time in the Oligocene-Miocene Pirabas Formation of Northern Brazil. In these Oligocene-Miocene carbonate deposits, Sinusichnus sinuosus is characterized by horizontal, highly regular sinusoidal burrow systems with T- and H-shaped branching points. The main difference between the S. sinuosus described herein and other occurrences worldwide is the anomalous diameter of the burrows (4 to 10?cm). These trace fossils occur in organic matter-rich, wackestone/packstone and laminated mudstones interbedded with boundstones deposited in an inner carbonate platform paleoenvironment. The exceptional size of the studied S. sinuosus could have been associated to the producer’s size, which may be attributed to construction by large crustaceans, similar to fossils found within the Pirabas Formation. Also, the sinusoidal morphology and retrusive spreiten could be a result of the fodinichnial/domichnial behavior.     

The influence of drought,precipitation and fossorial mammal reintroduction on the density of fossorial arthropods and their burrows in arid Australia

The density and abundance of arid-dwelling taxa often change significantly in response to precipitation fluctuations and the abundance of their predators. The survival and density of burrowing arthropods and their burrows in arid environments following prolonged dry periods and subsequent rains is poorly understood, as is the potential influence of reintroductions of their predators, such as fossorial mammals. The persistence of these arthropods and their burrows may be important for other species that rely on them for food or use their burrows for shelter. In this study, we examined the density of burrowing and ground-nesting arthropods and their burrows in Australia's Strzelecki Desert over two years between 2019 and 2021. This period spanned the tail-end of the worst drought on record and subsequent drought-breaking rains. We employed a Before-After Control-Impact (BACI) study design to examine the short-term effects of a fossorial mammal reintroduction of the greater bilby (Macrotis lagotis) into predator-free fenced exclosures and used an inspection camera to detect the presence of spiders and other taxa within individually marked burrows. We observed the largest changes in arthropod abundance and burrow density between a period that encompassed a third consecutive summer in drought and the commencement of drought-breaking rains, with some taxa declining by as much as 77% (p < 0.001). While the density of harvester ant middens erupted over this time, the density of tarantulas, trapdoor spiders and scorpions declined significantly. The greater bilby reintroduction had no short-term effect on the densities of the arthropods or their burrows, but their arrival may have implications on their post-drought recovery. Further studies are needed to determine if the significant declines in arthropod populations and burrows are reflective of normal boom-bust population dynamics due to the poor natural history knowledge of the arthropods we examined.     

A comparison of crayfish burrow morphologies: Triassic and Holocene fossil,paleo‐ and neo‐ichnological evidence,and the identification of their burrowing signatures

The architectural and surficial morphologies of crayfish burrows from the Upper Triassic Chinle Formation and Holocene sediments were compared in order to determine: 1) if Triassic burrows could truly be attributed to crayfish activity; 2) how comparable the burrowing mechanisms are; and 3) whether or not a common set of burrowing signatures could be identified for both ancient and modern freshwater crayfish. Materials used in this study include burrows from the members of the Upper Triassic Chinle Formation, casts of modern burrows constructed by Procambarus clarkii Hobbs and Procambarus acutus acutus (Girard) in the laboratory, and casts of naturally constructed modern burrows of Cambarus diogenes di‐ogenes (Girard).

Triassic and Holocene crayfish burrow morphologies exhibit simple to complex architectures, varying degrees of branching, chamber, and chimney development. They also exhibit relatively textured surficial morphologies (bioglyphs) such as scrape and scratch marks, mud‐ and lag‐liners, knobby and hummocky surfaces, pleopod striae, and body impressions. Holocene crayfish construct distinctive burrows due to their conservative limb arrangement, functional morphology, and behavior with respect to environmental stimuli. Similarities between Holocene and Triassic crayfish burrows suggest that extant and Triassic crayfish employed identical burrowing mechanisms. Features of the surficial and architectural morphologies impart a distinctive signature to burrows of both ancient and modern freshwater burrowing crayfish.

Burrowing signatures of crayfish can be used to identify new and previously misinterpreted continental trace fossils. These are useful in studies of the paleohydrogeology, paleoclimatology and paleoecol‐ogy of burrow‐bearing deposits.     

Dispersal and social organization of the northern hairy-nosed wombat Lasiorhinus krefftii

Burrows of the northern hairy-nosed wombat were arranged in loose clusters, each of which was used in common by a group of up to 10 wombats. However, individual wombats rarely used the same burrows on the same days and feeding ranges tended to be separate within each sex. The incidence of breeding dispersal among females was quite high (at least 50%); dispersal distances ranged up to almost the full extent of the population's range. Dispersal by adult males was rare, and no juvenile males were observed to disperse.     

Burrow morphology and utilization of the goby (Parapocryptes serperaster) in the Mekong Delta,Vietnam

Some fish species living in mudflats construct burrows for dwelling and hiding. The goby Parapocryptes serperaster is a burrowing fish in mudflats of many estuaries in South East Asia. This study was carried out in the Mekong Delta, Vietnam, to examine burrow morphology and usage by this species. Morphology of the burrows constructed by P. serperaster was investigated by resin castings in situ to obtain the physical structure and configuration of each burrow. Fish from the burrows were caught and measured before burrow casts were made. Fish burrows comprised several openings, a few branching tunnels and multi-bulbous chambers. The surface openings were circular, and the shapes of branching tunnels were nearly round. The burrows had interconnected tunnels and various short cul-de-sac side branches. The burrow structure differed between fish sizes, but burrow dimensions were positively correlated with fish size, indicating that larger fish can make larger and more sophisticated burrow. The burrow structure and dimensions were not different between the dry and wet seasons. Laboratory observations showed that P. serperaster used body movements to dig burrows in the sediment. Burrows could provide a low-tide retreat and protection from predators, but were not used for spawning and feeding for this goby species. This study indicates that the burrowing activity of gobies is an important adaptation for living in shallow and muddy habitats.     

The relative importance of substratum characteristics and recruitment in determining the spatial distribution of the fiddler crab Uca uruguayensis Nobili

The roles of sediment characteristics and the pattern of recruitment in influencing the abundance of the fiddler crab Uca uruguayensis on Argentinean mudflats were evaluated. The density of adult crabs showed a patchy distribution related to the sediment thickness (depth at which a layer of fossil shells are buried), but the density of juvenile crabs was not coupled with the density of adult crabs. In a field experiment, fossil shells were removed and the density of crabs significantly increased, which demonstrates that the presence of the layer of shells is a structure that may hinder the establishment of burrows. The density of crabs was related to sediment thickness, sediment torque and organic matter content. The importance of each of these variables was different for adult and juvenile crabs, indicating that the distribution of adult crabs may be caused by mechanisms affecting adult crabs themselves and is not established by the recruitment pattern. Moreover, in a field experiment, the density of juveniles decreased when adult crabs were added, and increased when adult crabs were removed.The morphology of burrows was related to sediment characteristics. Burrows were deeper, longer and more voluminous when sediment thickness was high. The volume of burrows decreased with increasing sediment torque. These results suggest that the morphology of burrows is related to the space available and the ease with which sediment it can be excavated. However, an important amount of variability remained unexplained, suggesting the presence of additional environmental variables or behavioural plasticity not considered by this study. Together, these results demonstrate that the spatial heterogeneity in the environmental factors can be translated to a spatial heterogeneity in the distribution of fiddler crabs.     

Quantification of pumping rate of <Emphasis Type="Italic">Chironomus plumosus</Emphasis> larvae in natural burrows

This paper investigates and compares experimentally determined water velocity field above natural macrozoobenthos burrows generated by Chironomus Plumosus larva during their bio-irrigation activity. All experiments were carried out using particle image velocimetry and performed in mesocosms filled with sediment burrowed by larvae, and the water velocity fields near the inlets and outlets of the U-shaped burrows were measured. From water velocity data the average volumetric flow rates between 54.6 and 61.1 mm³/s were calculated. Assuming an average burrow diameter of 2.25 mm, the volumetric flow rates suggest the average flow velocities through burrows during the pumping period between 13.7 and 15.4 mm/s. Two additional interesting phenomena could also be shown by analyzing the flow field generated by the larva. The analysis of the amount of tracers used for visualizations revealed that some of the tracer particles added to the water must have been consumed along their path from the inlet toward the outlet, hinting clearly to the so-called filter-feeding action of C. plumosus. The second phenomenon is due to the form of motion C. plumosus generates. By careful flow visualizations it was found that unlike other organisms such as Urechis caupo that use peristaltic body contractions, C. plumosus worms its body sinusoidally catapulting the fluid far into the overlying water body. This action is of ecological advantage for it avoids generating short oxygen circuits for their respiration and filter feeding.     

The effect of microhabitats on the leaf litter decomposition and on the distribution of soil animals

Earthworm burrows as microhabitats for other soil fauna were studied in a hornbeam-oak mixed forest in Hungary. Comparative chemical analysis and feeding experiments were carried out to find out whether the leaves in the burrows of large-bodied earthworms are more decomposed than those from the surrounding areas. The total organic matter content, the C/N ratio, the stability coefficient and the percentage of tannins and lipids indicate that the chemical breakdown of the litter material is more advanced in the burrows than on the other parts of the forest floor especially in autumn. No consistent differences were observed in the amounts of other organic components. Feeding experiments showed that three species of the fauna preferred the leaves pulled into the burrows to those from the surrounding areas and the preference was greater in autumn than in spring.
It is suggested that the high density of some soil animals in the burrows in autumn is due to the more palatable food there; in summer the microclimate of the burrows is favoured, whereas spring can be considered as a transition period.     

Activity patterns, feeding and burrowing behaviour of the crab Ucides cordatus (Ucididae) in a high intertidal mangrove forest in North Brazil

Activity patterns, feeding and burrowing behaviour of the economically important semi-terrestrial mangrove crab Ucides cordatus (Ucididae, L. 1763) was studied in a high intertidal Rhizophora mangle forest stand in Bragança, North Brazil. Video observations in the rainy and dry season were conducted over 24 h cycles at different lunar phases to investigate the behaviour of these litter-feeding crabs outside their burrows. During the rainy season, crabs stayed inside their burrows for 79% and 92% of the time during day and night, respectively. Time spent for feeding, burrowing and other activities outside their burrows was significantly longer during the day with 9.9% (night: 1.7%) and at waning and waxing moon with 9% (full and new moon: 0.9%). At neap tides (no tidal inundation) foraging and feeding activities outside burrows were clearly light-dependent, increasing at dawn and decreasing at dusk. Highest activities during daytime relate to the visual localisation of food. During the dry season, crabs spent less time inside burrows at neap tides than during the rainy season (80% and 91%, respectively). However, time spent for feeding activities was similar during both seasons. During almost all observation periods crabs collected leaf litter, but rarely fed on it outside burrows. At neap tides nearly all available litter was collected, suggesting that the U. cordatus population is litter-limited during these times. At spring tides (regular tidal inundation) the surface activity of U. cordatus was tide-dependent. Crabs closed their burrow entrances 2-3 h before flooding and re-emerged as soon as the tide retreated. During the day, burrow maintenance was the second most frequent behaviour after feeding. Agonistic interactions were regularly observed and were mainly related to burrow defence. The mean foraging radius of the crabs was only 19 cm (max: 1 m) underneath high Rhizophora mangle trees where crab densities were high. The results point to a high competition for burrows and show that U. cordatus is territorial. It is concluded that several exogenous factors, in particular light, leaf litter availability, flooding of burrows and the presence of conspecifics are important in controlling the crabs' activity patterns.     

Parental care and reproductive behavior of the clown goby, <Emphasis Type="Italic">Microgobius gulosus</Emphasis>, with observations on predator interactions

Describe reproductive behavior and mating system of the clown goby from field observations. Clown gobies exhibit a loosely haremic mating system. Pairs construct burrows at the base of cattails, the roots of which provide structural support and a spawning substrate. Larger males monopolize multiple burrows, each with an individual female. After spawning, males camouflage burrow entrances with sand and females brood developing young for 4 days. Males continue to guard the covered nests in 50% of observed brooding periods. Burrows are also used as shelter from predators. Both sexes confront intruders but only males exhibit a distinct color response to juvenile blue crabs, Callinectes sapidus, the most significant predator. The male color response appeared to mimic the color of adult blue crabs, a known predator of juvenile crabs, perhaps acting as a deterrent. The presence of the predatory blue crab may require one parent to perform deterrent displays, promoting female care in this mating system.     

The effects of conspecifics on burrow selection in juvenile spotted salamanders (<Emphasis Type="Italic">Ambystoma maculatum)</Emphasis>

Spotted salamanders (Ambystoma maculatum) are pond-breeding amphibians that disperse into terrestrial habitat from natal wetlands after undergoing metamorphosis, relying on small-mammal burrows and coarse woody debris for refugia. The effect of conspecifics on burrow use in juvenile salamanders is poorly understood. Determining how the presence of conspecifics influences the settlement decisions of juvenile salamanders can increase our understanding of amphibian dispersal and our ability to predict population dynamics. We conducted behavioral laboratory trials using 58 recently metamorphosed salamanders to examine how salamanders selected burrows in the presence of conspecifics. Salamanders were more likely to settle in a burrow that was occupied by a conspecific versus an unoccupied burrow. Our results indicate that juvenile salamanders may show conspecific attraction and/or trailing behavior during the dispersal phase.     

Burrow structure and use in the sand fiddler crab, Uca pugilator (Bosc)

Uca pugilator, the sand fiddler crab, constructs two kinds of burrows in protected, sandy upper-intertidal and supratidal substrates on the west coast of Florida. Temporary burrows are built and used as a refuge by non-breeding crabs during high tide periods and at night when crabs cease feeding in the intertidal zone. Breeding burrows are constructed and defended by courting males and are the site of mating, oviposition and the incubation of eggs by females. Up to three ovigerous females may be accommodated in a single breeding burrow, each female sequestered in a separate terminal chamber. The construction and defence of burrows specialized for breeding may be an adaptive response by males to the preferences females exhibit when selecting a breeding site.     

Feeding response of the Aldabra giant tortoise (Geochelone gigantea) to island plants showing heterophylly

Aim Heterophylly is present in many plant species on oceanic islands. Almost all of these plants are island endemics, and heterophylly may have evolved as a response to feeding from large insular browsers such as giant tortoises and flightless birds. We tested this anti‐browser hypothesis by feeding Aldabra giant tortoises (Geochelone gigantea) with leaves of native Mauritian plants to see if they distinguished between juvenile and adult leaves and between heteophyllous and homophyllous species. Location Mauritius. Methods In a choice experiment we recorded feeding response of four captive Aldabra giant tortoises to 10 species of Mauritian plants, of which seven were heterophyllous and three homophyllous. Results In general, juvenile leaves of heterophyllous species showed convergence in shape and midrib coloration. Homophyllous foliage was preferred to heterophyllous, and among heterophyllous species adult foliage was preferred to juvenile. Main conclusions Several Mascarene heterophyllous plants show convergence in morphology of juvenile leaves and these are avoided by giant tortoises. This indicates a strong selection history from large browsers such as the giant tortoises. The Mascarene example is in accordance with several other comparable cases of plant‐large browser interactions from other archipelagos.     

Burrow morphology and dynamics of mudshrimp in Asian soft shores

Mudshrimps are important soft shore bioturbators but research on the ecology of tropical species has received less attention when compared with their temperate counterparts. The mudshrimp Austinogebia edulis is common on Asian soft shores and lives in burrows for its entire adult life. Epoxy resin casting of A. edulis burrows showed that they were approximately Y-shaped, with an upper U-part and the lower central shaft part. The burrows had two openings extending to the surface; the mean distance between the two openings was 11.0 cm in Hong Kong and 26.4 cm in Taiwan. Openings of the burrows had small chimneys. The tunnels of the burrows were circular, narrow and with a smooth surface (tunnel diameter corresponded to shrimp carapace width). Each burrow was inhabited by a single shrimp and burrows were inter-connected during the mating and reproductive season. Each burrow had four to 12 spherical chambers, which were free of detritus. The chambers were thought to be used for suspension feeding, current generation and as turning points. The depth of burrows was up to 1.1 m. Multivariate analysis on various burrow parameters showed that burrows collected on a mud flat in Taiwan were deeper, had a wider distance between the openings and a larger volume than burrows collected from a sandy shore in Hong Kong, suggesting that burrow architecture is variable between shore types. Burrow architecture, however, did not vary between tidal levels, seasons and shrimp density on the shores in Hong Kong, indicating that the burrows were quite stable within the substratum and were not affected by environmental and biological factors.     

Obligate crayfish burrow use and core habitat requirements of crawfish frogs

Crawfish frogs (Lithobates areolatus) have experienced declines across large portions of their former range. These declines are out of proportion to syntopic wetland-breeding amphibian species, suggesting losses are resulting from unfavorable aspects of non-breeding upland habitat. Crawfish frogs get their common name from their affinity for crayfish burrows, although the strength of this relationship has never been formally assessed. We used radiotelemetry to address 4 questions related to upland burrow dwelling in crawfish frogs: 1) what burrow types are used and how do they function to affect crawfish frog survivorship; 2) what are the physical characteristics and habitat associations of crawfish frog burrows; 3) what are the home range sizes of crawfish frogs when burrow dwelling; and 4) where are crawfish frog burrows situated with respect to breeding wetlands? We tracked crawfish frogs to 34 burrows, discovered another 7 occupied burrows, and therefore report on 41 burrows. Crawfish frogs exclusively occupied crayfish burrows as primary burrows, which they inhabited for an average of 10.5 months of the year. With one exception, crawfish frogs also used crayfish burrows as secondary burrows—temporary retreats occupied while exhibiting breeding migrations or ranging forays. Burrows were exclusively located in grassland habitats, although crawfish frogs migrated through narrow woodlands and across gravel roads to reach distant grassland primary burrow sites. Home range estimates while inhabiting burrows were 0.05 m² (the area of the burrow entrance plus the associated feeding platform) or 0.01 m³ (the estimated volume of their burrow). Crawfish frog burrows were located at distances up to 1,020 m from their breeding wetlands. To protect crawfish frog populations, we recommend a buffer (core habitat plus terrestrial buffer) of at least 1.2 km around each breeding wetland. Within this buffer, at least 3 critical habitat elements must be present: 1) extensive grasslands maintained by prescribed burning and/or logging, 2) an adequate number of upland crayfish burrows, and 3) no soil disturbance of the sort that would destroy crayfish burrow integrity. © 2012 The Wildlife Society.     

Underground mating in the fiddler crab Uca tetragonon: the association between female life history traits and male mating tactics

Brood size and other life-history traits of females affect male investment in mating. Female Uca tetragonon, producing relatively small broods, were attracted to the burrows of males for underground mating (UM) while carrying eggs. Most UM females released larvae and ovulated new broods during the pairing, averaging 3.9 days. While a female was incubating one brood, another brood was developing within the ovaries because the females were feeding adequately during incubation. These findings suggest that in U. tetragonon, a small-brood species, females increase the total number of broods produced by breeding continually. In contrast, in large-brood species, feeding by ovigerous females is relatively brief and not enough to prepare the next brood during incubation, inducing temporal separation between incubation and brood production. Unlike females in other ocypodids where females with large broods remain in the breeding burrows of males, most female U. tetragonon left the male after UM. Wandering in female U. tetragonon after the pairs separate may occur because their small broods are adequately protected by an abdominal flap. Relative brood size probably determines the vulnerability of the incubated broods to the females' surface behavior. Hence, male reproductive success in large-brood species may decrease greatly if males expel their mates after ovulation, although this is not necessarily so in small-brood species. Whether the male drives away the female or not may depend on which behavior within either small- or large-brood species yields the greater male reproductive success. In U. tetragonon some females extruded eggs in their own burrows after surface mating as well as in males' burrows after UM. It was unclear whether females chose a male with a larger burrow as an UM mate unlike several large-brood species. Burrows of both UM males and ovigerous females in U. tetragonon were relatively smaller than those in some large-brood species, indicating that incubation of small broods does not require large burrows. Rather than benefits of UM by female choice, wandering resulting from intersexual conflict, and sperm competition may explain why some females mate in males' burrows in this small-brood species.