Burrow Entrance Research Articles

Armadillos as taphonomic agents of archaeological sites in the Pampas Region, Argentina

Armadillos constitute a recurrent taphonomic agent in the disturbance of archaeological sites in the Pampas region of Argentina. Their burrows generate vertical and horizontal movement of archeological and modern materials, creating anomalous associations, both on the surface, as well as at the deep levels of a site. Measuring the potential impact of armadillo burrows on a local environment in direct proximity with an archaeological site may help to reconstruct its taphonomic history. The objective of this work is to evaluate the impact of armadillo burrows on the formation processes of the Hangar site. Point provenience and morphometric measurements were recorded on 169 armadillo burrows located in direct proximity to the Hangar site archaeological excavation. The mean length of the burrow entrances was 70.7 cm, and the mean slope was 40.4°. The armadillos excavated an average of 0.036 m3 from each burrow. Approximately 59% of the burrows surveyed presented material re-exposed by armadillos, including lithic, ceramic artifacts, prehistoric and modern faunal remains, and human bones. For the Hangar site, burrowing animals were signficant agents in the formation processes of the assemblage. Our results help explain the mixing of materials in the Hangar site, and could be used in the interpretation of other sites affected by armadillos in similar habitats.

Clipping by Plateau Pikas and Impacts to Plant Community

Plateau pikas (Ochotona curzoniae) often clip tall plants near active burrow entrances to detect and avoid predators. This clipping behavior influencing plant communities near active burrow entrances has not been well documented. A field experiment was conducted to investigate the effects of this clipping behavior on plant communities across three sites in the Qinghai-Tibetan Plateau by comparing plant communities near active burrow entrances with communities near abandoned burrow entrances. This study showed that the clipping behavior decreased plant community height and increased plant cover and species richness of the community and had no effect on plant community biomass across three sites or at each site. This study further showed that clipping behavior decreased the plant biomass of the graminoid group and had no effect on the plant species richness of the graminoid group, whereas it increased the plant biomass and plant species richness of the forb group across the three sites or at each site. These findings suggest that a general pattern concerning the effect of the clipping behavior can increase plant species richness and decrease the grazing quality of alpine meadows near active burrow entrances.

Amazon freshwater crab Dilocarcinus pagei (Decapoda: Trichodactylidae): a view about burrow construction behavior

Crabs use burrows to prevent predation, environmental interference and shelter. The present study investigated the excavation behavior of the trichodactylid crab Dilocarcinus pagei, considering the biometric aspects of the burrows, the excavation time, the amount of bioturbation and the excavation behavior of the two sexes. The burrows of males had a mean diameter larger than the females, although the depth was similar for both sexes. Females had higher bioturbation than males, and showed enlargement in a camera format at the bottom, even closing the entrance of the burrows with a "plug" after their construction. Both the camera and the presence of the "plug" in the burrows of the females may be associated with reproduction. The presence of pellets observed at the entrance of burrows is associated with the cleaning of the pereiopods by crabs after the excavation. The sequence of behaviors for the construction of the burrows is described in detail, contributing to the knowledge about the biology and ecology of freshwater crabs of the Amazon.

Effect of Crab Burrows on CO2 Flux from the Sediment Surface to the Atmosphere in a Subtropical Mangrove Forest on Ishigaki Island, Southwestern Japan

To clarify the effects of crab burrows on variation in sediment CO2 flux in mangrove forest, we measured the traits of crab burrows (density and entrance area size) and the CO2 flux rate from sediment surfaces, in areas with and without burrows, in a subtropical mangrove forest on Ishigaki Island, southwestern Japan. Burrow density and entrance area showed significant differences among seasons (warm, middle, and cool) and mangrove zones (upper-, middle-, and downstream), which may have depended on crab phenology, life cycle, and species composition. The sediment CO2 flux rate was significantly higher at plots with crab burrows (B+) than at those without burrows (B−) in each zone and season. However, standardized sediment CO2 flux rate by burrow surface area at B+ plots did not differ significantly from that at B− plots. In addition, there were no significant differences in sediment temperature and sediment water content between the two types of plots. Moreover, the level of microbial respiration differed significantly between sediments collected from the deep part and those collected from either the ground surface part or burrow walls. These results suggest that crab burrows increase sediment CO2 flux from the mangrove forest floor by increasing the sediment–atmosphere interface area, thereby inducing a change to aerobic conditions in the sediments around burrows. Therefore, the seasonal and spatial effect of crab burrows on the forest floor should be considered when evaluating sediment CO2 flux and examining the role of the mangrove ecosystem as a carbon sink.

Body size and habitat use of the common weasel Mustela nivalis vulgaris in Mediterranean farmlands colonised by common voles Microtus arvalis

Small mustelids such as weasels are highly specialized predators of small rodents. Their diminutive size allows hunting for prey underground, but also means that they are “bite-sized” predators, preyed upon by other larger predators. Habitat use by weasels is therefore expected to depend not only on prey abundance, but also on predation risk. We report here on the body size and habitat use of common weasels Mustela nivalis vulgaris captured in intensive farmlands of northwest Spain during 2009–2015. We show that weasels’ capture rate was higher in field margins than in other habitats (cereal and alfalfa fields, fallows) irrespective of season. All small mammals (common vole, wood mouse, Algerian mouse, and greater white-toothed shrew) were consistently more frequently captured in field margins than other habitats. Weasel capture rate in each habitat was proportional to that of prey in these (alfalfa > fallows > cereal), except for field margins, which were used more intensively than expected from prey capture rate. Weasel capture rate was 37% lower in areas provided with nest boxes to increase local raptor abundance, a reduction that occurred in all habitats and was significant when correcting for prey capture rate. Weasel habitat use reflected a trade-off between prey abundance (bottom-up control) and predation risk (top-down control), with a preferential use of field margins that offer not only more prey but also permanent vegetation cover and protection from avian predators throughout most of the annual crop cycles. Weasel and vole head width data show that voles are not safe underground from smaller female weasels and that burrow entrances were wide enough for weasels to escape underground from predators. In NW Spain, common voles are a main farmland pest causing significant impacts. We discuss the implications of current vole control measures for weasels in areas recurrently affected by vole outbreaks.

Burrowing Invasive Species: An Unquantified Erosion Risk at the Aquatic‐Terrestrial Interface

AbstractInvasive nonnative species acting as “ecosystem engineers” or “geomorphic agents” can represent a major landscape disturbance. Quantification of their biogeomorphic impacts remains a key knowledge gap, and aquatic‐terrestrial transition zones may be particularly exposed to impacts. We demonstrate how burrowing invasive species represent a potentially significant but unquantified erosion risk at aquatic margins. We reveal a lack of quantitative research on geophysical impacts, despite increasing concerns over threats to waterways and flood defense infrastructure. We explore example animals of global interest, comprising crustaceans, fish, reptiles, and mammals and reveal the global nature of the issue: over 100 countries, states, or territories where at least one example species is established, and over 20 with 3‐6 species present. We present a conceptual model for the impacts of burrows on stability and erosion at aquatic margins using established models of geotechnical, hydrological, and hydraulic drivers. Burrows are hypothesized to (i) alter failure plane position, decrease failure plane length, and increase failure plane angle (thereby decreasing bank shear strength); (ii) modify the spatial distribution of porewater pressure, thereby increasing subsurface flow (seepage), reducing cohesion, and increasing the likelihood of slip failures at the bank face; (iii) increase turbulence and sediment entrainment at burrow entrances; and (iv) alter flow resistance at the bank face. Most effects are expected to increase bank instability/erosion with the exception of (iv) which has the potential to offer protection from fluvial action. We call for further research in these areas to quantify impacts for different environments and different invasive species.

NEW METHODS FOR STUDYING THE ACTIVITY OF SEMIAQUATIC MAMMALS

A new method for studying the activity of semiaquatic mammals using digital portable voice recorders has been developed. Previously, actographs and night-vision devices were used to study semiaquatic mammals near their burrows. This method allows the mammal activity registration directly in the burrows. The use of voice recorders makes it possible to accurately determine whether the burrow system is inhabited or non-inhabited. In addition, it has become possible to identify the day-night time intervals during which the animals are the most or least active. The new method was tested on the Russian desman (Desmana moschata). Therefore, to identify the burrows in which the recorders were to be installed, the burrows were probed. A probe is a pole pointed at one end with a T-shaped handle at the other end. The researcher's task is to detect the entrance to the burrow, usually under water. And then the direction of the underground passage is determined by means of the probe. For this purpose, the ground is pierced to detect the hollows in the burrow with the probe starting from the burrow entrance (the probe falls through unevenly). At a distance of 2–3 meters from the burrow, in some cases largely depending on the burrow length, the ground is dug up above the burrow in the form of a small well, 10–15 cm in diameter. A digital voice recorder was placed vertically in this well, so that the microphone was directed down towards the burrow. Desman noises can be characterized as short series formed as a sequence of contiguous short peaks of 15–25 seconds with 5 second interruptions formed by regular waves of breathing and its movement noises. Desman noises differ by mean amplitude and duration on oscillograms. As a rule, the noise audibility ranges from 1 to 3 minutes.

On three symbiotic species of the alpheid shrimp genus Salmoneus Holthuis,1955 from the Indo-West Pacific, including one new to science (Malacostraca: Decapoda: Caridea).

Three species of the alpheid shrimp genus Salmoneus Holthuis, 1955 associated with burrows of other decapod crustaceans are reported from various Indo-West Pacific localities. Salmoneus venustus sp. nov. is described based on material collected at two distant localities, Nha Trang Bay, southern Vietnam, the type locality of the new species, and the Yiti-Sifah region east of Muscat, northern Oman. Both specimens were collected with the aid of a suction pump applied to burrow entrances or mounds in muddy sand; the holotype was possibly associated with burrows of the callianassid ghost shrimp, Glypturus sp. Salmoneus venustus sp. nov. shares many characteristics with S. latirostris (Coutière, 1897), including the red banding of the pleon, but can be distinguished from S. latirostris and all other species of the genus by a unique combination of morphological characters. The large-sized Salmoneus brucei Komai, 2009 is reported from Sumba, central Indonesia, representing a significant southward extension of the species' previously known distribution range and the first record since its original description. The callianassid ghost shrimp Lepidophthalmus cf. rosae (Nobili, 1904) is recorded as a new host of S. brucei. Finally, Salmoneus colinorum De Grave, 2004, associated with burrows of larger snapping shrimps from the Alpheus malabaricus Fabricius, 1798 species complex, is reported for the first time from Madang, Papua New Guinea, representing an eastward extension of the species' previously known distribution range.

Burrow Wars and Sinister Behaviour among Burrow-Nesting Petrels at Sub-Antarctic Marion Island

Competition for nest sites is relatively common amongst burrow-nesting Procellariiformes, especially on some sub-Antarctic islands where there is limited availability of good burrow-nesting habitat. Where space is limited, petrels may even successfully share a common burrow entrance or nest chamber and burrow densities can reach >7000 burrows/ha. Interspecies burrow competition and chick evictions generally occur as a result of an overlap in breeding seasons, yet there are few documented records of this behaviour and even within study colonies many evictions are unconfirmed or probably go undetected. Here we report on interactions among three burrow-nesting petrels (White-chinned Petrels Procellaria aequinoctialis, Grey Petrels P. cinerea and Great-winged Petrels Pterodroma macroptera) at Marion Island which we observed through regular nest checks with a burrowscope and using infra-red video cameras inside burrow chambers. Despite relatively low petrel densities, White-chinned Petrels were responsible for 17% (8/46) of the Great-winged Petrel chick mortalities over the five breeding seasons (3% of the breeding attempts), but two were also recorded feeding Great-winged Petrel chicks. A pair of White-chinned Petrels evicted a Grey Petrel chick, but then had their own chick killed by Grey Petrels the following season, who went on to breed successfully in the same burrow. Feral Cats Felis catus were eradicated in 1991 and the greatly reduced petrel populations are slowly recovering, which could exacerbate competition for burrows on Marion.

Efficacy and nontarget impact of zinc phosphide-coated cabbage as a ground squirrel management tool.

Effective management of ground squirrels relies on an integrated pest management (IPM) approach. Rodenticides may be included in an IPM program, but they must be efficacious with minimal impact on nontarget species. A zinc phosphide-coated green bait may meet these requirements. We established a study in northeastern California to test zinc phosphide-coated cabbage as a management tool for Belding's ground squirrels (Urocitellus beldingi). We specifically addressed factors that would influence the efficacy of a baiting program, as well as potential exposure risk to nontarget species. We found that prebaiting was an important application strategy, and efficacy increased as ground squirrel abundance increased. Efficacy was also greater in western portions of the study area, likely due to greater bait consumption at western sites. Belding's ground squirrels fed most heavily on cabbage during mid-morning and late afternoon; bait applications shortly before these time periods would increase bait consumption while minimizing nontarget risk. Bait uptake was greatest around burrow entrances. The only nontarget species observed feeding on cabbage was the California kangaroo rat (Dipodomys californicus), although they were never observed feeding on treated cabbage. Zinc phosphide-coated cabbage can be an efficacious tool for managing ground squirrels, but there will be limitations on where and how it can be used effectively. It posed a low risk to nontarget species present in our study area, but nontarget risk could vary regionally. The use of a zinc phosphide-coated green bait should only be one part of an IPM strategy for managing ground squirrels. © 2019 Society of Chemical Industry.

An experimental test of the multi-scalar impacts of digging mammal reintroductions on invertebrate burrows

The decline of ecosystem engineers alters ecosystems, with impacts cascading through to other organisms. Through engineering and predation, digging mammals may affect burrowing invertebrate assemblages, leading to changes in invertebrate-driven soil engineering. Using a mammal reintroduction sanctuary in southern Australia, we tested how digging mammals alter invertebrate burrows (density and size of burrow entrances) and whether these impacts were scale-dependent. We examined the micro-site (pit-scale) effects of mammal foraging pits on invertebrate burrowing activity by comparing natural and artificial pits and bare-ground, and artificial pits of different dimensions within different microhabitat types. To test how mammals affected invertebrate burrows and soil physical and chemical properties at larger scales, we used an exclusion experiment (plot-scale) and surveys inside and outside a reintroduction reserve (landscape scale). Invertebrate burrows were more numerous in mammal pits than bare-ground and artificial pits, and larger in mammal pits than bare-ground. The density and size of invertebrate burrows depended on pit morphology, with burrow density greatest in narrow bilby pits and large burrows favoured by bettong pits. However, the influence of foraging pits on invertebrate burrows was scale-dependent: changes in invertebrate burrows were not detected at the plot or landscape scale. Only 4.5% of land surface area was occupied by pits and this might be insufficient to alter burrow or soil properties detectably in un-stratified surveys at larger scales. Digging mammals altered the small-scale (but not large-scale) distribution of invertebrate burrows, suggesting that their reintroduction provides an avenue through which to restore the heterogeneity of other organisms and functions in ecosystems.

Systematics of the palisade trapdoor spiders (Euoplos) of south-eastern Queensland (Araneae : Mygalomorphae : Idiopidae): four new species distinguished by their burrow entrance architecture

Within the spiny trapdoor spider genus Euoplos Rainbow exists a group of species from south-eastern Queensland that create unusual ‘palisade’ burrow entrances. Despite their intriguing burrows, the group was only recently circumscribed, and all species within it were undescribed. In this study, by undertaking a molecular phylogenetic analysis of two mitochondrial markers and seven nuclear markers, we confirm that the palisade trapdoor spiders, here formally named the ‘turrificus-group’, are monophyletic. We further recognise four species based on morphological, molecular and behavioural characters: E. crenatus, sp. nov., E. goomboorian, sp. nov., E. thynnearum, sp. nov. and E. turrificus, sp. nov. Morphological taxonomic data for each species are presented alongside information on their distribution, habitat preferences and burrow architecture. A key to species within the turrificus-group is also provided. The unusual burrow entrances of these spiders, which project out from the surrounding substrate, are found to exhibit structural autapomorphies, which allow species-level identification. Consequently, we include features of burrow architecture in our key and species diagnoses. This provides a non-intrusive method for distinguishing species in the field. Finally, we conclude that all species within the turrificus-group are likely to represent short-range endemic taxa. http://zoobank.org/urn:lsid:zoobank.org:pub:F2E042DC-DA14-4751-A48B-A367ABC272D9

The burrow behavior and influenced factors of a prairie subterranean zokor (Myospalax psilurus).

The Transbaikal zokor (Myospalax psilurus) is a dominant rodent distributed in the meadow steppe of Inner Mongolia in northern China. Due to long history of evolution in subterranean environment, the zokor has an adaptive behavior: sealing burrow entrances. When a burrow is damaged, exposed entrances appear, and within a relatively short time, the zokor would be active in sealing the entrances to reduce risks to its survival. In general, it is thought that zokors avoid light and wind, which is consistent with their behavior of sealing burrow entrances. However, direct evidence from field experimental research has been lacking. This study set up 68 field sampling points in a meadow steppe in Inner Mongolia from August to September, 2014 and used a wind–light isolator to study the effects of wind and light factors on zokor burrow entrance sealing behavior. The results showed that there were no significant correlations between wind or light factors and the frequency of zokor burrow entrance sealing. Therefore, wind and light factors are not direct factors associated with zokors actively sealing burrow entrances.

Grazing as a conservation management tool: Responses of voles to grazer species and densities

Grazing is a widely applied conservation management tool, but the optimal regime for biodiversity conservation is still unknown. The effects of grazers on small mammals are not yet fully understood and mostly restricted to studies which compare grazed with ungrazed areas. We determined the effect of different livestock grazers and densities and a rotation regime, on voles in a conservation area in The Netherlands. We used a 7-year grazing experiment with horse and cattle grazing at two densities namely 0.5 and 1 animal ha−1 (equivalent to 0.4 and 0.8 LSU), including a rotation regime i.e. 1year summer grazing with 1 cattle ha−1 followed by 1 ungrazed year. We recorded vole activity signs as a measure for presence (i.e. presence of burrow entrances, droppings, runways and plant clippings) in circular 2m2 plots along transects. Low grazer densities, regardless of species, corresponded to higher vole presence. Vole presence tended to be greater with cattle grazing than with horse grazing, but the difference was not significant. The increase in vole presence was greater in the rotation regime than with low or high density cattle grazing. The different vole activity signs provided similar results to each other with the exception of burrow entrances, suggesting that this measure is less accurate in predicting vole presence. Hence, voles clearly responded to the different grazing regimes. Our results have high relevance for conservation, in particular in systems where small mammals contribute to important ecological processes (e.g. bioturbation, seed dispersal) and play a crucial role in the survival of (iconic) higher trophic level taxa such as raptors or mammalian predators. In such systems, conservation management may best implement low-density cattle or rotation grazing.

Interspecific Burrow Sharing between Mammals in Countryside in Japan

In Japan, red foxes (Vulpes vulpes) and raccoon dogs (Nyctereutes procyonoides) have been observed using burrows made by Japanese badgers (Meles anakuma). However, basic information, including how and when the species share the burrows, is scarce. In this study, a camera trap was set at a burrow entrance used by badgers, and different mammals that used the burrow were investigated. Burrow uses by six identified mammalian species and unidentified species from two mammal groups (rodents and bats) were confirmed. The capture frequency of rodents increased, when that of three Carnivora species decreased. Accordingly, rodents might use the burrow selectively during seasons when carnivore usage of the burrow was low. Raccoon dogs, red foxes, and Japanese badgers showed considerable searching behavior, the frequency of which differed significantly among these species. Raccoon dogs and red foxes seemed to avoid contact with Japanese badgers by performing more searching than badgers. Therefore, the mammals engaged in interspecific burrow sharing are likely to exhibit temporal differentiation.

Investigating the role of a mud structure in a fiddler crab: do semidomes have a reproductive function?

Sensory traps occur when a signal evolves to mimic a cue to which the receiver responds favorably in another context. For example, if females are attracted to the noise a prey item makes, then a conspecific male can mimic that noise, thereby attracting females in the context of mating. Thus, sensory traps can be beneficial to receivers since attraction helps locating males more efficiently. But what happens when receivers are less attracted by the sensory trap outside of the original context (due to the cost of the response for instance)? Does this weaken and eventually “break” the sensory trap? Here, we show that a rare, small mud structure (a semidome) built by some male fiddler crabs (Austruca mjoebergi) at their burrow entrances are most likely relics of the sensory traps used by other fiddler crabs (the larger, far more abundant hoods of Leptuca species). Females of A. mjoebergi have retained their tendency to move towards vertical structures for protection when threatened by a predator—the original context thought to be important in the evolution of sensory traps in other fiddler crab species. However, females show no significant preference for males with semidomes. Additionally, males do not use the semidomes as landmarks to relocate their burrows when courting. The results suggest that in A. mjoebergi, semidomes do not function as sensory traps, despite the existence of a pre-existing bias in females. We suggest that semidomes have lost their attractiveness in the mating context due to ecological features, such as predation and environmental heterogeneity. There is growing evidence of sensory traps in many animal species, with an ever-widening range of contexts from nuptial gift giving in spiders to egg recognition in non-brood-parasitized birds. While we are starting to understand the significance of sensory traps, little thought has been given to what happens when they break down. If there is a change in the original context that favored the receiver’s response, then there is likely to be a subsequent change in the receiver’s bias and finally, in the sensory trap. If the mimic of the original stimulus does not induce a beneficial response in the receiver anymore, the sensory trap would become inefficient and stop being selected. The effect will be most profound when the sensory trap was costly to set up, since there will be selection against its retention. Here, we show that a sensory trap can become a relic when ecological conditions change and make it not functional anymore. To our knowledge, it is the first study providing such empirical evidence.

The impact of posture and basking orientation on thermoregulation in the Sungazer (Smaug giganteus)

Body temperature (Tb) is one of the most influential factors affecting physiological processes in ectothermic animals. Reptiles use behaviours such as shuttling, and postural and orientation adjustments to ensure that Tb remains close to a target. It is thought that target body temperature (Ttarget) is aligned to the physiological and behavioural thermal optima of the animal. The Sungazer (Smaug giganteus), a Threatened lizard species, is unique amongst the Cordylidae in that lizards inhabit self-excavated burrows in open grasslands, a habitat in which there are few exposed rock basking sites. In this situation, Tbs are likely to be greatly influenced by postural and orientation adjustments during basking. We measured Tbs using modified iButtons, and calculated Ttarget of free-ranging Sungazers in order to assess the impact of body posture and orientation in the thermoregulation of the species. We used camera traps to record lizard behaviour at burrow entrances and aligned these measures to measures of Tb. Ttarget was 30 ± 1.4 °C, and Tbs remained within this range for 371 ± 162 min per day. The anterior body-up postures resulted in faster heating and higher Tbs. Lizards heated faster when facing away from the sun and spent proportionally more time in this orientation in the morning when Tbs were lower than Ttarget. Our findings suggest that their wide behavioural repertoire allows Sungazers to thermoregulate effectively over a broad range of environmental conditions and may thus be able to effectively respond to changing climatic conditions.

Taking a risk: how far will male fiddler crabs go?

Courtship is costly for males when it increases their energy expenditure and predation risk. There are several ways in which males might be able to mitigate these costs, or compensate for them by elevating the benefits of courtship. First, they could selectively court more profitable females. Second, they could adjust the amount of risk they take against their residual reproductive value. Third, they could sometimes use cheaper signals to deceive females. In the fiddler crab Leptuca terpsichores (Crane, 1941), males risk losing their burrow to another crab and falling prey to a bird when they leave their burrow to intercept a mate-searching female and lead her back to the burrow for mating. Some males build sand hoods at their burrow entrances, which are landmarks that attract females and allow males to relocate their burrows quickly with little error. Here, we show that (1) males took greater risks when courting larger females by travelling farther away from their burrows; (2) the distance a male moved from his burrow did not depend on his size (hence, age); and (3) males with sand hoods did not travel farther away from their burrows than males without hoods, and they were not more likely to reach females. Taking greater risks when courting larger (more fecund) females appears to be a key means through which male fiddler crabs can achieve a more favourable balance between the costs and benefits of courtship. Courtship and mate choice can be costly for males. Males may improve the balance between courtship costs and benefits by modifying their risk-taking during courtship according to the perceived value of the female, or their expectations of future reproduction. Male fiddler crabs move away from their burrows to court females, which is risky because they may lose the burrow or be attacked by predators. We used the distance a male travels from his burrow as an index for the level of risk he is willing to take. We explored the effects of female size, male age, and the presence of a sand hood at the burrow entrance on distance travelled during courtship. Males took greater risks to court larger females, but did not adjust risk-taking according to their age (expected future reproduction) or whether their burrow had a sand hood.

Social structure and reproduction of long-tailed porcupine (Trichys fasciculata)

Abstract We studied the social structure of long-tailed porcupine (Trichys fasciculata) in the tropical rainforest in Sabah, Borneo Island, Malaysia via direct observation assisted by radio-tracking and camera-trapping at burrow entrances. We identified and observed seven individuals in the study area, of which five were radio-tagged. Analysis of their burrow use, home range, and behaviour strongly suggested that five of the observed individuals formed a family group consisting of an adult male–female pair and their three offspring, two of which were born during the study period. The family members used the same burrow site almost every day, and their home ranges largely overlapped. In contrast, the other two individuals never used the burrow sites of this family group. The adult male–female pair was maintained for at least 18 months and reproduced twice during the study period. They had a litter size of one, and the inter-litter interval was estimated to be 11 months. During these two reproductions, the previous litter stayed in the natal family group as a sub-adult after the next juvenile was born. Direct paternal care, such as grooming the juvenile, was also observed. Their low reproductive potential should be considered in conservation efforts.

Ecosystem engineering through aardvark (Orycteropus afer) burrowing: Mechanisms and effects

Burrowing mammals are often considered to be ecosystem engineers as burrowing disturbs the soil, thereby potentially changing resource availability and affecting habitat conditions for other species. After their excavation, burrows may strongly impact local plant communities through several mechanisms, including resource trapping, altered chemical and physical soil properties, and amelioration of microclimatic conditions. We studied ecosystem engineering by aardvark (Orycteropus afer) burrowing by comparing soil and vegetation characteristics between three microsites (burrow entrances, excavated soil mounds and adjacent control sites). We were able to identify several engineering effects and distinguish between potential mechanisms. Burrow soils were cooler, drier and less compact than the other microsites, with all three microsites representing unique combinations of abiotic conditions. Mean species richness was higher at older burrows than mounds and non-burrowed controls, despite burrows having a smaller seedbank and not differing in soil fertility from mounds and control sites. However, the opposite was observed at fresh burrows and mounds, where control plots contained more species on average than the other two types of microsites. Burrow age and microsite type also affected species composition, although only a small proportion of species were significantly associated with specific microsites and just two species were limited to a single microsite type. We suggest that trampling and the physical digging action at burrow entrances, and burial by deposited soil at mounds, prevents the establishment of many plant species at active burrows. However, once abandoned, burrow entrances provide good physical conditions for seedling survival, allowing the establishment of more species. Therefore, as suggested previously for other ecosystem engineers, it is important to explicitly consider the age and degradation processes of engineered structures. In addition, our results highlight biologically-important differences in engineering impacts between burrow entrances, where soil is removed, and mounds, where soil is deposited. Such microscale differences are important to consider when examining bioturbation or, more generally, ecosystem engineering.