Burrow fractal dimension and foraging success in subterranean rodents: a simulation

For animals that forage underground, the success with whichfood items are located may be closely related to burrow architecture.Fractal dimension, which describes how a burrow explores thesurrounding area in a way that is independent of burrow length,is an obvious choice for a single metric describing burrow shape.Although it is often assumed that burrows of high fractal dimensionwill be associated with greater foraging success, this has notpreviously been demonstrated. In this study, we use computersimulations to study the success with which burrows of differentfractal dimensions locate randomly distributed food items. Inaddition, we examine the effect of different patterns of fooddistribution (in particular the patchiness with which food itemsare distributed) and consider how using different criteria forlocating food items affects the relationship between fractaldimension and foraging success. We conclude that, under a widerange of plausible assumptions about the ways in which subterraneanrodents forage, burrows of high fractal dimension are more successfulat locating food items than burrows of lower fractal dimension.     

The trace fossil Sinusichnus from the Upper Ordovician of Anticosti Island,eastern Canada

Branched, sinusoidal burrows assigned to Sinusichnus cf. seilacheri Knaust et al. 2016; occur in Upper Ordovician (Hirnantian) carbonates on Anticosti Island. These are abundant and monospecific at the base of the Oncolite Bed of the uppermost Ellis Bay Formation, marking a regional discontinuity surface during the multiphase Ordovician mass-extinction event. In contrast to Mesozoic and Cenozoic records of Sinusichnus, commonly attributed to the activity of decapod and isopod crustaceans, the burrow systems from Anticosti Island were probably produced by other arthropods of unknown affinity. A combined dwelling, locomotion and feeding behaviour of their trace maker is assumed. This is the oldest record of the ichnogenus Sinusichnus, previously only known since the Triassic, and its first evidence from North America.     

The Role of Giant Armadillos (Priodontes maximus) as Physical Ecosystem Engineers

Through their excavations, giant armadillos (Priodontes maximus) alter their physical surroundings and create new habitats, which influence resources for at least 24 other species of vertebrates in the Brazilian Pantanal. The role of this poorly known species as an ecosystem engineer may be of high value to the community of vertebrates.     

Response of alpine meadow communities to burrow density changes of plateau pika (Ochotona curzoniae) in the Qinghai-Tibet Plateau

Plateau pika (Ochotona curzoniae) is a key component of alpine meadow ecosystem in the Qinghai- Tibetan Plateau, and the increase of its number leads plant components of alpine meadow ecosystem to adaptively response. A field survey was carried out to determine the response of alpine meadow community to population densities of plateau pika by using available burrow density to replace the population density of plateau pika. This study showed that the height of alpine meadow communities gradually increased, and the cover of alpine meadow communities firstly decreased, and then increased as the available burrow density increased. With the increase of available burrow density, the richness index of alpine meadow communities firstly decreased and then increased, and the evenness index of alpine meadow communities firstly increased and then decreased, however, the diversity index of alpine meadow communities firstly increased, and then decreased, finally increased. In the increasing process of available burrow density, the total plant biomass and the unpalatable plant biomass firstly decreased and then increased, and the palatable plant biomass firstly increased and then decreased, indicating that the palatable plant biomass was the highest and the unpalatable plant biomass was the lowest at 14 available burrow per 625 m². In the economic groups of plant biomass, the weed biomass was the highest and the legume biomass was the lowest at any available burrow densities, and the grass biomass and the sedge biomass were related to available burrow densities, indicating that the sedge biomass were bigger than the grass biomass at 3 available burrow per 625 m², inverse at 54 available burrow per 625 m², similar between 3 and 34 available burrow per 625 m². Accompanying by the increase of available burrow densities, the legume biomass and the sedge biomass significantly decreased (P < 0.05) and the legume became disappearance at 54 available burrow per 625 m²; the grass biomass firstly increased and then decreased, peaking at 14 available burrow per 625 m². The weed biomass firstly decreased and then increased, and was the lowest at 14 available burrow per 625 m². This study suggested that the responses of alpine meadow communities to population density of plateau pika at 14 available burrows per 625 m² were more sensitive than that at other available burrow per 625 m² from plant species diversity, biomass, height, cover and economic group.     

Development of an index of abundance for pygmy rabbit populations

The pygmy rabbit (Brachylagus idahoensis) is a cryptic, burrowing lagomorph of conservation concern for which an efficient method to monitor populations is needed for conservation planning. We developed an index of abundance based on density of active burrow systems at 7 sites (57.2–118.5 ha) in east central Idaho. We conducted censuses of burrow systems and used mark-resight surveys of 80 radio-collared individuals to estimate density of rabbits. At 5 sites, we also used a second method to estimate rabbit numbers based on presence of tracks in snow around burrow systems. We evaluated patterns of burrow use by individuals and examined the relationship between vegetation structure and density of rabbits. Density of active burrow systems varied from 0.19 to 3.46 per ha, and density of rabbits ranged from 0.02 to 0.46 per ha. Number of burrow systems used by individuals increased with density of available burrows, which supported a nonlinear relationship between abundance of burrows and rabbits. Population density increased curvilinearly with density of active burrows accounting for >75% of the variation (r² = 0.79) in population estimates across sites. We documented a positive relationship between visual obstruction of vegetation and density of rabbits across 6 of the study sites. Our results suggest that density of burrows can serve as an index for monitoring changes in abundance of pygmy rabbits in east central Idaho and that this index also might be useful for monitoring changes in relative abundance over time at other locations. To assess abundance at larger spatial scales or across different regions, the index should be calibrated under regional conditions and site-level covariates should be evaluated. © 2011 The Wildlife Society.     

Burrow webs: Clawing the surface of interactions with burrows excavated by American badgers

Ecosystem engineers are organisms that influence their environment, which includes alterations leading to habitat provisioning for other species. Perhaps the most well‐examined guild of species provisioning habitat for other species is tree cavity excavators or woodpeckers (Picidae). Many studies have examined the suite of secondary cavity users that rely on woodpeckers, and how the ecological network of secondary users, collectively referred to as the nest web, changes across communities. Despite similar habitat provisioning processes, fewer studies have assessed the suite of species associated with burrowers providing access to subterranean habitat. Here, we begin to characterize the burrow web provisioned by American badgers (Taxidea taxus) and evaluate the diversity and frequency of species interactions we detected at abandoned badger burrows in Wyoming, USA. We deployed camera traps at 23 badger burrows and identified interactions with the burrow by birds, mammals, and reptiles. Overall, we discovered 31 other species utilizing badger burrows, consisting of 12 mammals, 18 birds, and 1 reptile. Mammals, other than American badgers themselves and other fossorial species such as ground squirrels (Urocitellus sp.), frequently using burrows included mice (Peromyscus sp.), long‐tailed weasel (Mustela frenata), pygmy rabbit (Brachylagus idahoensis), and desert cottontail (Sylvilagus audubonii). Of the 18 bird species detected, most accounted for <5% of overall detections, besides chipping sparrows (Spizella passerina) at 7.2%–11.5% of detections. The most common category of detection by bird species was foraging, contrary to mammals, which used the burrow frequently and were commonly observed entering and exiting the burrow. This work provides additional context on the ecological role of American badgers within their environment. More broadly, this work scratches the surface of many remaining questions to explore with the aim of advancing our understandings about burrow webs across the diversity of burrowing species and the communities in which they occur.     

Female within-nest spawning-site preference in a paternal brooding blenny and its effect on the female mate choice

Female spawning-site preference within a nest and its effect on the female mate choice in a paternal brooding blenny Rhabdoblennius ellipes , were examined in rocky intertidal pools using artificial nests. The number of eggs deposited at the nest entrance site was lower than the number deposited at the center and at deep sites. Moreover, the within-nest difference in the egg developmental stage indicated that eggs at the nest entrance site were deposited after those at the center and deep sites. These results indicated that females prefer to spawn eggs in the center and deep sites rather than at the entrance site. Owing to the higher egg mortality rate at the entrance site, females may avoid spawning at such sites. An analysis of the nests in the study area suggested that the within-nest site preference affects female mate choice that is females avoided nests where only the entrance site was available for spawning and instead spawned in nests where the center and deep sites were available.     

Urban badger setts: characteristics, patterns of use and management implications

Damage caused by badger setts is an important source of human–carnivore conflict in urban areas of the UK, yet little is known about the spatial distribution of urban badger setts or their pattern of occupation. We compared the density, spatial distribution and size of setts in four urban and two rural study areas in the UK and assessed the applicability to urban systems of distinguishing between 'main' and 'outlier' setts. In addition, we used radio-telemetry to investigate diurnal patterns of sett use in one urban area (Brighton). It was possible to distinguish between main and outlier setts in urban environments, and local sett densities were comparable in urban and rural areas. However, urban badgers used substantially fewer setts than did a nearby rural population, and they spent a smaller proportion of days in outlier setts. Social groups with larger ranges had more setts available to them and, within groups, individuals with larger ranges used more setts. Outliers appeared to serve multiple functions, including allowing efficient and safe travel to important parts of the home range. We conclude that sett densities can be high in urban habitats, suggesting significant potential for sett-related problems to arise. The fact that urban main setts can be distinguished from outliers enables management actions to be tailored accordingly. In particular, because main setts seem to represent a particularly valuable resource to urban badgers, alternatives to the closure of problem main setts need to be considered.