Changes in sooty shearwater (Puffinus griseus) abundance and harvesting on the Rakiura Titi Islands

Abstract

We estimated the change in abundance of sooty shearwater (titi, Puffinus griseus) at six Rakiura Titi Islands, New Zealand, by comparing historical and recent surveys of the density of entrances to breeding burrows. We found evidence that entrance density between 1994 and 2006 was lower than it was between 1961 and 1976. Our overall estimate of the annual rate of change in burrow entrance density is ‐1.0% (95% CI ‐2.3 to ‐ 0.1%). Declines have been slower on four islands where Rakiura Maori maintain a traditional harvest of sooty shearwater chicks ("muttonbirding") compared with three unharvested islands. Density‐dependent population processes may explain this difference: rates of decline have been faster in areas of relatively high initial entrance density, and historically the harvested islands have had lower initial density. There was a strong, apparently linear, relationship between entrance density and chick density on breeding colonies, so changes in entrance density probably do indicate a real population decline. The western side of Taukihepa, the largestof the Titi Islands, first became accessible for muttonbirding with the advent of helicopters in the 1970s, but it is unknown whether this has caused an increase in the number of sooty shearwaters harvested by Rakiura Maori.     

Nesting activity,breeding success and colony size for the Wedge-tailed Shearwater Puffinus pacificus on Heron Island

Abstract The Capricorn Group of islands in Australia's Great Barrier Reef Marine Park sustains one of the world's largest breeding populations of the Wedge-tailed Shearwater Puffinus pacificus. Heron Island, a 13.5 ha coral cay which supports tourist and research station leases as well as a national park, is the third largest nesting island in the group. Sample censuses of breeding burrows were conducted each year between 1985 and 1990 and a further survey was completed in 1993. These returned estimates of between 13 264±1387 and 16 337±1545 active burrows (Y±SE). Burrow densities within each of the habitats monitored showed no significant trends between years, although there were large differences in burrow density between habitats. There were roughly the same number of burrows in the developed (west) and national park (east) halves of the cay. A miniature video camera system (burrowscope), which allowed nesting chambers at the ends of burrows to be inspected, was used in 1989, 1990 and 1993. This demonstrated that around half the burrows were occupied by incubating birds. Variations were found in the distribution of incubating birds between habitats, although this did not remain constant between the years. In the 1993 season, breeding activity was traced from the burrow establishment to fledging stage. Fifty-one per cent of burrows were used for breeding (eggs laid), 77% of eggs hatched and 80% of chicks produced a fledgling. Overall breeding success for the island was estimated at 61%. In 1993 the area designated as Buildings was found to have significantly lower hatching success compared with natural habitats. Most mortality occurred at the egg stage; however, in the Fringe habitat, mortality was highest at the chick stage. Previous surveys have estimated the breeding population from burrow counts. It now appears that only about 30% of such burrows produce fledglings.     

青藏高原东缘高寒森林小型兽类地表洞穴选择与生境特征

高寒森林地表的小型兽类洞穴是生态系统重要的景观特征,对于认识小型兽类的分布格局及其生态功能具有重要意义.为此,以青藏高原东缘典型高寒森林生态系统小型兽类洞穴为对象,于2015年夏季(7—9月)研究了其地表分布与生境特征.结果表明: 小型兽类洞穴平均洞口密度为182.8个·hm^-2,不同森林植被类型显著影响洞穴密度,表现为针叶林(328.6个·hm^-2)>针阔混交林(160.0个·hm^-2)>灌木林(125.0个·hm^-2)>阔叶林(81.5个·hm^-2)>竹林(66.7个·hm^-2). Mann-Whitney U Test和主成分分析表明,小型兽类栖息样地的乔木郁闭度、乔木均高、乔木胸径、乔木密度、地表植被盖度、倒木密度、倒木覆盖度、灌木均高都显著大于非栖息样地;乔木因子是决定小型兽类生境选择的首要因子,贡献率最大(44.8%),其次是倒木因子(23.2%)和灌草丛因子(13.9%).说明高寒森林地表有明显的小型兽类洞穴分布,其分布格局主要受植被和倒木的影响.     

野生扬子鳄洞穴口的位置选择

1999年至 2 0 0 2年 7～ 10月内的 4个时段 ,在安徽扬子鳄国家级自然保护区内调查发现野生扬子鳄洞穴 4 0个 (现用 2 4个 ,遗弃 16个 )。对洞口的方向、隐蔽程度、距水面高度、与水源距离及与村落距离等 5个可能影响扬子鳄洞穴选择的环境变量做了测定。结果表明 :87 5 %的洞口在水面 0～ 0 5m及 <0m ,85 0 %距水源 <5m ,32 5 %朝北 ,72 5 %植被覆盖度≤ 70 % ,4 2 5 %距村落 <10 0m ;距水面高度、与水源距离、洞口方向和隐蔽程度的主成分贡献率依次降低 ,累计达 76 6 %。方便入水是洞口位置选择的主要因素     

Use of burrow entrance flaps to minimise interference to Chatham petrel (

The Chatham petrel (Pterodroma axillaris) is an endangered species, restricted to a single population on South East Island, Chatham Islands. The key threat to breeding success is loss of chicks as a result of interference by broad-billed prions (Pachyptila vittata) prospecting for burrows for their oncoming breeding season. The effectiveness in decreasing interference using an artificial burrow entrance flap was investigated. The flap exploits behavioural differences between the species. Chatham petrels have a high incentive to push through a flap due to their investment in their burrow and chick, while prospecting prions are influenced by ease of access when searching for potential burrows. This trial found 90% of Chatham petrels entered their burrows through the artificial flap. Flaps acted as barriers to broad-billed prions, where 22% entered the burrow through the flap (P <0.01) compared to the control burrows. Artificial burrow flaps have the potential to provide a low cost, low labour strategy for protecting the known breeding population of Chatham petrels.     

Sooty shearwater (

Rakiura Maori annually harvest sooty shearwater (Puffinus griseus) chicks from islands in Foveaux Strait and adjacent to Stewart Island, New Zealand. Chick availability and the number of chicks harvested were estimated during the 1994 and 1995 seasons on Poutama (Evening Island). Burrow entrance densities estimated using circular plots were significantly higher in 1994 (0.45 ± 0.03 per m) than in 1995 (0.41 ± 0.03 per m). A similar burrow entrance density (0.45 ± 0.04 per m) was obtained in 1995 using a transect sampling technique. The number of usable burrows estimated using circular plots in 1994 and 1995 was 387 508 and 337 732 respectively. Of these, chicks occupied 24% ± 6% in 1994 and 29% ± 4% in 1995. It was estimated the muttonbirders harvested 13-24% (15 722) of the chicks present on Poutama in 1994 and 17-28% (22 092) in 1995. Muttonbirders targeted areas of the island with higher chick density and less fallen stems. Excluding chicks rejected by the muttonbirder (less than or equal to 750g), harvested chicks were significantly heavier and had less down than randomly encountered chicks. If larger heavier chicks are more likely to return and breed, then the preference for these chicks by muttonbirders would affect predictions of harvest impacts.     

Burrow Characteristics and Microhabitat Use of the Turpan Wonder Gecko Teratoscincus roborowskii(Squamata,Gekkonidae)

Burrow structural charactersitcs and microhabitat use of the Turpan wonder gecko Teratoscincus roborowskii(Gekkonidae) were studied between April and September of 2013 in the Turpan Eremophytes Botanic Garden,in the Turpan Depression of Western China.Burrow depth,entrance orientation,entrance height and width were observed.We assessed microhabitat selection and noted differences in microhabitat use among males,females,and juveniles.The magnitude of selection was measured using Jacobs' index of selectivity.Entrance height and width of the burrows of adults were significantly larger than those of juveniles,but the difference in burrow depth was not significant.The directional orientation of the burrow entrance showed a preference for the north-northeast and south-southeast,which were likely influenced by local prevailing winds and sunlight.Both the adult and juvenile geckos prefer to construct their burrows in sandy soil within a layer of loose soil whose thickness is greater than 30 cm.A majority of the burrows were located within 20 m of the nearest plant.Nearly half(48%) of the entrances of juveniles were located within 5 m of the nearest vegetation,significantly different from those of the adults.Results showed that the Turpan wonder gecko did not utilize microhabitats according to their availability,but rather that it preferred microhabitats which contained dead wood or the caper bush.Our results suggested that burrow characteristics and microhabitat selection were important factors in T.roborowskii adaptation to harsh and arid desert habitats.     

Kangaroo Rats Remodel Burrows in Response to Seasonal Changes in Environmental Conditions

Burrow architecture enhances important animal functions such as food storage, predator avoidance, and thermoregulation. Occupants may be able to maximize fitness by remodeling burrows in response to seasonal changes in climate and predation risk. My objective was to examine how banner‐tailed kangaroo rats (Dipodomys spectabilis) modify the number of burrow entrances in response to seasonal conditions. For 3 yr, I monitored fluctuations in number of burrow entrances in kangaroo rat mounds. Individual kangaroo rats continually remodeled mounds in response to seasonal conditions. Compared to summer, mounds in winter had approximately 50% fewer entrances and plugged entrances were common. Monthly differences in number of entrances were closely linked with seasonal changes in soil temperature and precipitation. Number of entrances decreased as soil temperature and precipitation declined. Changes in burrow entrances likely reflect seasonal differences in the relative importance of burrow functions. Fewer burrow entrances during winter would create a warmer microclimate by reducing convective heat loss in mounds, resulting in thermoregulatory savings for occupants. During the summer, thermoregulatory costs of kangaroo rats are low, but risk of seed cache spoilage and predation from snakes increases. Adding burrow entrances after large summer rainfall events would increase the evaporation rate within mounds, reducing spoilage of seed caches. More burrow entrances would also reduce predation risk in the summer by providing additional escape routes.     

Artificial larviposition sites for field collections of the puparia of tsetse flies Glossina pallidipes and G. m. morsitans (Diptera: Glossinidae)

Tsetse flies Glossina pallidipes Austen and G. morsitans morsitans Westwood deposit their larvae in warthog burrows, in August-November, at Rekomitjie Research Station, Zambezi Valley, Zimbabwe. Artificial burrows, made from 200-l steel drums, were used to sample these flies and to collect their puparia. Sand-filled plastic trays in the burrows served as a substrate for larval deposition. The sand was covered with c. 2 cm of leaf litter after it was shown that only 3% of larvae were deposited on bare sand if both substrates were available. Other burrow modifications - artificially shading the burrow entrance, increasing the relative humidity inside the burrow, or reducing the size of the burrow entrance - significantly decreased deposition rates. The use of burrows in the hot season results in a reduction in the temperature experienced by the puparium towards an assumed optimum level of 26 degrees C. Artificial burrows maintained a mean temperature of 28.5 degrees C during October-November 1998, c. 2.5 degrees C cooler than ambient; earlier work has shown that natural burrows can be c. 5 degrees C cooler than ambient at these times. This may explain why natural burrows in full sunlight were used for larviposition, whereas artificial burrows were used only when they were in deep shade, and why significantly higher proportions of G. pallidipes were found in natural (66%) than in artificial burrows (34%). Better-insulated artificial burrows might produce more puparia with higher proportions of G. pallidipes. Burrows become waterlogged during the rains and may be too cool for optimum puparial development during the rest of the year. The percentages of G. m. morsitans in catches of females from artificial burrows, refuges and odour-baited traps were 34, 26 and < 10% respectively. Traps are biased in favour of G. pallidipes; artificial burrows may show a bias in favour of G. m. morsitans that is a function of temperature. Artificial warthog burrows provide a convenient way of studying the puparial stage in tsetse and for the first time facilitate the capture of females as they deposit their larvae.     

The microenvironment of house mice on Marion Island (sub-Antarctic)

On Marion Island, house mice ( Mus musculus) establish burrow systems that range from unbranched corridors 0.5 m long with a single chamber (in some instances without a chamber) to complexly branched systems extending over an area of up to 4 m² and containing up to four chambers. Total underground area occupied by burrow systems (chambers plus corridors) was from 5 to 23 m² ha^-1, corresponding to burrow-system volumes of 250-1,300 dm³ ha^-1. In autumn, about three-quarters of chambers contained small food caches. Most (87%) entrances to burrow systems faced away from prevailing winds, especially winds that bring snow, hail or rain. Seasonal and diurnal temperature variations in burrows are considerably dampened (daily minimum in burrows seldom drops below 2°C), compared with the air just above the vegetation canopy. Over the whole year, total night-time warmth in a burrow (heat sum, 24,883 degree hours) was 53% greater than at the top of the canopy (16,317 degree hours). Burrows' entrances are generally connected above ground by runways (paths and tunnels through the vegetation). Runways also represent a warmer environment than the air above the canopy during the breeding season at night (13,466 degree hours at the runway surface compared with 11,900 degree hours at the top of the canopy). House mice, which are living close to their physiological limits, temperature-wise, on Marion Island thus evade the worst extremes of the island's climate by constructing burrows and above-ground runways and this is an important factor in their survival.     

Habitat selection by the Spiny-tailed lizard (Uromastyx aegyptia): A view from spatial analysis

Many factors affect the habitat selection for animal species, which in turn may greatly affect their distribution in different ecosystems. Understanding the processes that affect habitat selection is also critical for guiding and managing conservation initiatives. Our study aimed to assess the habitat selection by free-ranging Spiny-tailed lizard (Uromastyx aegyptia) by analyzing a geospatial data connecting its burrow parameters to different habitat characteristics within selected sites in Hail region, Saudi Arabia. We examined evidence and patterns of significant spatial clustering for (366) active burrows by linking their parameters (burrow entrance size, burrow entrance width and burrow entrance height), their reference geographical locations and, two habitat characteristics defined by soil type and vegetation cover. The objective of the analysis was to increase the understanding on the burrows aggregation process in the space and, to describe its possible relation to other spatial habitat configurations. Analysis of distances based on the Nearest Neighbor Index (NNI) and hotspots detection in Nearest neighbor hierarchical clustering (Nnh) suggested twelve (12) spatial clusters located within the study area. In addition, a spatial ordinary least square (OLS) and Poisson regression models revealed significant effects of soil type and vegetation cover on burrow parameters (OLS, p < 0.05; Poisson, p < 0.001), which indicate a strong association between burrows parameters and habitats characteristics. Findings from the study also suggest that other factors such as elevations, highways, and human settlement concentration spots could possibly play a major role in defining burrow spatial aggregation and furthermore have a significant impact on habitat selection.     

Olfactory navigation to the nesting burrow in Leach's petrel (oceanodroma leucorrhoa)

Visual, auditory, and olfactory navigation in the homing behaviour of Leach's petrel to the nesting burrow were investigated. Petrels returning to their burrows at night hovered above the thick spruce-fir canopy in the vicinity of the burrow before plummeting to the forest floor a few metres downwind of their burrows. They then walked upwind to their burrows. Birds landed closer to, and followed more circuitous routes to, their burrows in still air than in a wind. They failed to avoid obstacles in the path to burrows, often failed to locate accurately burrow entrances on first trial, and vocalized only after entering the burrow. In a Y-maze olfactorium, captive breeding petrels chose an air current coming from their own nest material in preference to one from similar materials collected on the forest floor. In the same apparatus, birds did not respond positively to air currents from their own stomach oil or preen gland oil. Petrels taken from burrows and released that same night did not return within a week if their external nares were plugged or if their olfactory nerves were transected. They did return if not operated on or if only subjected to sham operations. These results support an olfactory guidance system in burrow location and argue against visual or auditory guidance.     

Responses of the endangered pygmy bluetongue lizard to conspecific scats

Many animals use chemical signals for communication between conspecifics and for territory marking. The pygmy bluetongue lizard is normally solitary, focussing activity around the entrance of its burrow, from where it ambushes prey, and rarely contacts other individuals. In this paper we examined whether lizards in laboratory experiments alter their behaviour in the presence of scats from conspecifics. In the first experiment, when lizards were offered a choice of two vacant burrows with or without a scat close to the entrance, they tongue flicked more often at the burrow entrance when the scat was present, and more often chose to occupy the burrow with the scat. An interpretation is that lizards use scat signals to recognise burrows that may be suitable because they have previously been occupied by a conspecific, but that they approach those burrows cautiously in case a resident is still present and likely to resist a takeover. Scats from male lizards were inspected (by both sexes) for longer than scats of female lizards. In the second experiment, when resident lizards were presented with scats outside of their burrows, they inspected and tongue flicked at those scats more often if the scat came from a male than a female lizard, but there was no definitive evidence from our experiments that lizards differentiated in their response to scats from lizards that were found close to or far from the test lizard. The results were consistent with a communication system in which lizards use scats to advertise their presence, independent of any direct contact.     

The use of cover and burrows by a population of rabbits (Mammalia: Oryctolagus cuniculus) in eastern Scotland

Adult rabbits were trapped in the spring on an area of grass and broom in the east of Scotland. They were ear-tagged and a sample of males and females were fitted with radio-collars. These were followed for two months to see whether they used burrows or ground cover for shelter during the day. Rabbits found on the surface were disturbed to see whether they bolted to burrows or stayed on the surface. The population was then re trapped to measure the population density, which was estimated to be 12.6 adults/ha in March, allowing for an apparent trapping bias against older females. One hundred and twelve burrow entrances/ha were counted from random quadrats. Males were more likely to be found on the surface than females, and rabbits that were more often on the surface were less likely to bolt to burrows when disturbed. Even when rabbits did bolt to burrows they frequently left them shortly afterwards and returned to the cover of the broom. Males that were most often found on the surface were lighter in weight than those found in burrows. This was not the case for females.     

Orientation of crustacean burrows in the Bay of Panzano (Gulf of Trieste, Northern Adriatic Sea)

Three burrow systems produced by Jaxea nocturna and one cluster of burrows produced by Upogebia pusilla where investigated in the Bay of Panzano, Northern Adriatic Sea, to determine preferred orientations. The distributions of dip directions differ between both producers. Steep shafts into the consolidated mud followed by large, shallowly inclined tunnels oriented in a manner similar to a spiral are characteristic for Jaxea nocturna burrows. In contrast, the Y-shaped burrows of Upogebia pusilla have entrance shafts that are less steep which are connected by a near-horizontal section, where a blind ending tunnel branches. Orientations of the dominating, shallowly inclined burrow parts are not randomly distributed in either Jaxea or in Upogebia burrows. Three preferred axial orientations with almost equal proportions in each direction are characteristic for the Jaxea burrow from the centre of the bay. This system transforms to a squared structure near the coast, where one direction parallels the shoreline and the other is oriented at right angles to the coast. The latter orientation demonstrates significant constancy in all investigated burrows. Upogebia burrow clusters coincide with the three preferred orientations of the Jaxea burrow from the bay centre, but the proportions of the directions are unequal. Burrow segments connecting the steep entrance shafts in Upogebia are oriented almost parallel to the shoreline, whereas at right angles to the coast the flat blind-ending tunnels incline towards the open sea. The study shows a strong coincidence between empirical and theoretical distributions of the dominating orientations in both species.     

Depth of artificial Burrowing Owl burrows affects thermal suitability and occupancy

Many organizations have installed artificial burrows to help bolster local Burrowing Owl (Athene cunicularia) populations. However, occupancy probability and reproductive success in artificial burrows varies within and among burrow installations. We evaluated the possibility that depth below ground might explain differences in occupancy probability and reproductive success by affecting the temperature of artificial burrows. We measured burrow temperatures from March to July 2010 in 27 artificial burrows in southern California that were buried 15–76 cm below the surface (measured between the surface and the top of the burrow chamber). Burrow depth was one of several characteristics that affected burrow temperature. Burrow temperature decreased by 0.03°C per cm of soil on top of the burrow. The percentage of time that artificial burrows provided a thermal refuge from above‐ground temperature decreased with burrow depth and ranged between 50% and 58% among burrows. The percentage of time that burrow temperature was optimal for incubating females also decreased with burrow depth and ranged between 27% and 100% among burrows. However, the percentage of time that burrow temperature was optimal for unattended eggs increased with burrow depth and ranged between 11% and 95% among burrows. We found no effect of burrow depth on reproductive success across 21 nesting attempts. However, occupancy probability had a non‐linear relationship with burrow depth. The shallowest burrows (15 cm) had a moderate probability of being occupied (0.46), burrows between 28 and 40 cm had the highest probability of being occupied (>0.80), and burrows >53 cm had the lowest probability of being occupied (<0.43). Burrowing Owls may prefer burrows at moderate depths because these burrows provide a thermal refuge from above‐ground temperatures, and are often cool enough to allow females to leave eggs unattended before the onset of full‐time incubation, but not too cool for incubating females that spend most of their time in the burrow during incubation. Our results suggest that depth is an important consideration when installing artificial burrows for Burrowing Owls. However, additional study is needed to determine the possible effects of burrow depth on reproductive success and on possible tradeoffs between the effects of burrow depth on optimal temperature and other factors, such as minimizing the risk of nest predation.     

穿山甲洞穴生态学初步研究

20 0 0年 6月～ 2 0 0 1年 5月 ,在大雾岭自然保护区共记录到 6 1个穿山甲洞穴 ,并对其中的 4 0个进行了解剖 .结果发现 ,穿山甲的洞均为盲洞 ,没有分支 ;洞口径大小一般为长径 14 2 0± 2 79cm (n =6 1) ,短径 12 5 0± 2 83cm(n =6 1) ;洞穴可分为冬洞和夏洞 .冬洞在冬春季节打造 ,洞穴较深 (1 4 4± 0 73m ,n =2 8) .夏洞在夏秋季节打造 ,洞穴较浅 (0 32± 0 11m ,n =12 ) ;穿山甲多在冬春季打洞 ,夏季打洞少 ,并且主要选择在土质松软湿润、土层厚、地表有机质丰富的黄壤土中打洞 ,以获得食物白蚁 ,然后再利用它越冬、卧息、繁殖、隐藏和逃避敌害 ;穿山甲对新洞的平均利用时间为 12 2 5± 2 2 5d ,而对旧洞的再次利用率极低 (1/12 =8 33% ) .文中还记录了 6 1个洞穴所在的各种环境因子 (分为 9类 ,2 7种 ) ,并依据因子出现频次和系统聚类结果 ,对穿山甲的洞穴生境选择进行了分析 .穿山甲喜爱将洞穴设置在干扰程度小 (干扰源距离 >10 0 0m)、坡度较陡 (30°～ 6 0°)、坡向为半阴半阳坡、针阔混交林、中低海拔 (76 0～ 15 0 0m)、洞口隐蔽程度好 (全隐蔽或半隐蔽 )、中坡或下坡位、离水源距离近 (<5 0 0m)的生境内 ;不喜爱将洞穴设置在阴坡、洞口隐蔽程度差 (裸露 )、极陡坡 (>6 0°)或缓坡     

The burrow system of the African ice rat Otomys sloggetti robertsi

We studied the architecture of the burrow system of the African ice rat Otomys sloggetti robertsi, a non–hibernating, diurnal murid rodent endemic to the sub–alpine and alpine regions of the southern African Drakensberg and Maluti mountains. In our study site we found ice rat burrows in two substrates (organic and mineral soils). The structure of the burrow system was similar in both soil types, comprising several interlinking tunnels, numerous burrow entrances and 1–2 nest chambers. However, the surface area of the burrow systems in organic soils was larger, the tunnels were deeper, and some of the systems contained two levels, all of which was contrary to our assumption that digging would be more difficult in the compact organic soils. Ice rats occur in colonies of up to 17 individuals, and the collected efforts of several individuals are required for constructing complex burrow systems. The burrow structure is similar to those of two arid–adapted relatives, Parotomys brantsii and Parotomys littledalei, suggesting that the burrow architecture among these three taxa may reflect the similar functions of burrows in extreme environments. For ice rats, burrows could provide a suitable microhabitat in which to escape adverse environmental conditions, particularly during winter. Moreover, ice rat burrows contained far fewer nest chambers than those of both Parotomys species, indicating that members in a colony share nest chambers, thereby facilitating huddling. Finally, the extensive interlinking tunnels may provide underground routes to aboveground feeding sites, thereby reducing exposure to adverse conditions.     

Orientation of crustacean burrows in the Bay of Panzano (Gulf of Trieste, Northern Adriatic Sea)

Three burrow systems produced by Jaxea nocturna and one cluster of burrows produced by Upogebia pusilla where investigated in the Bay of Panzano, Northern Adriatic Sea, to determine preferred orientations. The distributions of dip directions differ between both producers. Steep shafts into the consolidated mud followed by large, shallowly inclined tunnels oriented in a manner similar to a spiral are characteristic for Jaxea nocturna burrows. In contrast, the Y-shaped burrows of Upogebia pusilla have entrance shafts that are less steep which are connected by a near-horizontal section, where a blind ending tunnel branches. Orientations of the dominating, shallowly inclined burrow parts are not randomly distributed in either Jaxea or in Upogebia burrows. Three preferred axial orientations with almost equal proportions in each direction are characteristic for the Jaxea burrow from the centre of the bay. This system transforms to a squared structure near the coast, where one direction parallels the shoreline and the other is oriented at right angles to the coast. The latter orientation demonstrates significant constancy in all investigated burrows. Upogebia burrow clusters coincide with the three preferred orientations of the Jaxea burrow from the bay centre, but the proportions of the directions are unequal. Burrow segments connecting the steep entrance shafts in Upogebia are oriented almost parallel to the shoreline, whereas at right angles to the coast the flat blind-ending tunnels incline towards the open sea. The study shows a strong coincidence between empirical and theoretical distributions of the dominating orientations in both species.     

Short-Term Dispersal Response of an Endangered Australian Lizard Varies with Time of Year

Dispersal is an important component in the demography of animal populations. Many animals show seasonal changes in their tendency to disperse, reflecting changes in resource availability, mating opportunities, or in population age structure at the time when new offspring enter the population. Understanding when and why dispersal occurs can be important for the management of endangered species. The pygmy bluetongue lizard is an endangered Australian species that occupies and defends single burrow refuges for extended periods of time, rarely moving far from the burrow entrance. However, previous pitfall trapping data have suggested movement of adult males in spring and of juveniles in autumn of each year. In the current study we compared behaviours of adult lizards each month, over the spring-summer activity period over two consecutive field seasons, to provide deeper understanding of the seasonal dispersal pattern. We released adult pygmy bluetongue lizards into a central area, provided with artificial burrows, within large enclosures, and monitored the behaviour and movements of the released lizards over a four day period. There was a consistent decline in time spent basking, amount of movement around burrow entrances, and rates of dispersal from the central release area from early spring to late summer. Results could be relevant to understanding and managing natural populations and for any translocation attempts of this endangered lizard species.