Burrow

Wombats are large marsupial grazers native to Australia. They are 'ecosystem engineers' due to their burrowing, impacting rates of soil turnover, assisting with nutrient cycling and water infiltration, and creating habitat for other species. The aim of this review is to provide an overview of available information on the habitat and distribution, abundance and threats to bare-nosed wombats (Vombatus ursinus), and to provide a critical review of the current gaps in our knowledge to aid future management of the species. Bare-nosed wombats were previously widespread. Since European settlement their range has reduced. While habitat loss and contraction impact population numbers, bare-nosed wombat populations are also threatened by roadkill, introduced species, legal and illegal human persecution, and disease. Further research is required to understand the historic range of bare-nosed wombats, as well as current population numbers, so that we can determine the threats that most significantly impact this species. Increasing our understanding of habitat requirements, distribution and population numbers, as well as how to mitigate threats, will aid future management and conservation strategies for the species.

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.

The Tibetan Ground Tit Pseudopodoces humilis is a high-altitude passerine endemic to the Tibetan Plateau. A 4-year study in alpine meadows in Northern Tibet at 4300 m asl demonstrated that rather than using Pika Ochotona spp. holes as previously reported, the birds excavated one nest burrow themselves in spring and another after breeding, which they used for roosting in winter. Both the nesting and winter-roosting burrows comprised a straight tunnel leading to an ellipsoid chamber. There were no significant differences in placement or structural characteristics between the two types of burrows, except that winter-roosting burrows had a significantly smaller entrance diameter. Most burrows were 100–160 cm long and their chambers 20–40 cm deep. Tibetan Ground Tits tended to maximize the thermal benefits of their burrows by adjusting their spatial and structural characteristics in response to local solar radiation and wind regimes. Burrows tended to be oriented towards the sun and away from prevailing winds, presumably to maintain burrow temperature. Longer tunnels could function to save heat from solar radiation or reduce wind-disturbance, while shorter tunnels allow chambers to be warmed sooner in situations where wind potentially reduced soil temperatures. The thermal benefits to the birds of burrow architecture are likely to play a crucial role throughout the year in these extreme alpine environments.

Body size, nuptial gift characteristics and courtship behaviour, among other traits, can reflect the quality of a potential mate and, thus, might be under sexual selection. To maximize their mating success, individuals can show behavioural plasticity in sexual context. Allocosa senex is a burrow-digging wolf spider that exhibits reversal courtship roles and in sexual size-dimorphism expected for spiders. Males construct the mating refuge and females prefer males that build longer burrows, which are considered as nuptial gifts because they are delivered to them after mating. This study aims to determine whether male body size and female reproductive status influence burrow dimensions, courtship displays, female preferences and cannibalism rate in A. senex. For that purpose, we allowed males to construct burrows and performed sexual trials under laboratory conditions. Larger males were more courted by females, and in turn, they expressed more vibratory behaviours during courtship. However, and contrary to our expectations, smaller males constructed longer burrows. We suggest that males of A. senex exhibit size-dependent behavioural plasticity, and when they are smaller, they invest more in burrow construction to compensate their lower opportunities of courting intensively as larger males. In addition, females courted differentially according to their reproductive status, overriding male preferences for virgin females. This study opens several doors to future research regarding mutual choice in A. senex and the traits assessed by males and females during courtship, as well as about the influence of intrinsic and extrinsic factors shaping reproductive decision-making in this and other wandering spider species.

Burrow morphology and mating behaviour of Upogebia noronhensis was studied using resin casting of burrows in the field and observation of laboratory maintained animals. Burrows of U. noronhensis showed a typical Y-shaped pattern in over 70% of the cases analysed. The remaining 30% comprised U-shaped burrows lacking the lower tunnel (shaft) and burrows with long additional branches projecting from the U portion. Results from animals left to construct burrows in the aquarium closely matched those found in nature. Field and laboratory burrows showed that different shapes are related to the collapse of the burrow walls, the burrowing activities of other individuals and species, and to the behaviour of the species itself. U-shaped burrows form as a result of the partial construction of the burrow (the U part is always built first) or owing to the collapse of the shaft. Burrows with additional branches always belonged to males and result from their search for a female with which to reprod...

Observational data collected in the field and in enclosures show that diurnal, burrow-dwelling European ground squirrels (Spermophilus citellus) never were above ground during twilight at dawn or at dusk. The animals emerged on average 4.02 h (SD = 0.45) after civil twilight at dawn and retreated in their burrows on average 2.87 h (SD = 0.47) before civil twilight at dusk. Daily patterns of light perceived by these burrowing mammals were measured with light-sensitive radio collar transmitters in an enclosure (the Netherlands) and in the field (Hungary). The observational data are corroborated by the telemetry data, which show clear daily patterns of timing of light perception including light perceived from the burrow entrances. The first light was observed by the animals on average 3.54 h (enclosure, SD = 0.45) and 3.60 h (field, SD = 0.31) after civil twilight at dawn, whereas the final observed light was on average 3.04 h (enclosure, SD = 0.64) and 2.02 h (field, SD = 0.72) before...

Quantification of mangrove crabs is notoriously difficult. Several techniques have been applied in the past, but have rarely been tested. This paper looks at the use of burrow counts (BUR), binocular counts (BIN) and excavation (EX) for quantifying the fiddler crab Uca annulipes (H. Milne Edwards). Fieldwork took place at Maruhubi mangrove (Zanzibar, Tanzania). Twelve 1 m2 quadrats were assessed on one spring cycle and one neap cycle. The results showed a strong correlation between carapace width (CW) and burrow diameter (BD), namely CW (mm) = 1.37BD (mm) -0.64 (r2=0.98; p-2 (EX), 43.3 m-2 (BIN) and 104.8 m-2 (BUR). Of these, 37% (EX), 19% (BIN) and 42% (BUR) were juveniles (U. annulipes. Whilst binocular census may be most appropriately carried out on spring tides, burrow quantification may be better on neap tides. A major reason for BIN underestimates and BUR overestimates were discrepancies in juvenile counts. Thus, 28% (spring) to 39% (neap) of adults, but 72% of excavated juven...