Does Size Matter? The Case of the Courtship Pyramids in Red Sea Ghost Crabs (Ocypode saratan)

Display, wherein males attempt to maximize fitness by attracting sexually mature females to mate, is known to drive speciation by Sexual Selection. We researched the Red Sea Ghost Crab (Ocypode saratan; RSGC), in which males build display pyramids to attract females. The study was conducted at the beach in Eilat, Israel. At each session, we measured the height (in cm) of all pyramids and the dimensions (height, breadth; in cm) of the burrow entrance. We assumed that the size of the entrance represented the relative size of the carapace width of the occupant. The mean (± SE) entrance volume was 230.8 ± 11.7 cm, and the height of the pyramid was 11.8 ± 0.49 cm (n = 54). The results of our study did not support our hypothesis because we had expected to find a linear correlation between body size and pyramid height, i.e., the larger the male, the larger the pyramid. However, our results show that the largest males in the population either built small pyramids or not at all, and the cut-off of the larger crab’s body size appears to be around 350 cm3. We discovered a step-wise function in the data in that crabs with the smallest body size of ca. 250 cm3 constructed the highest pyramids, with a declining tendency between 250–350 cm3 and extremely low pyramids beyond 350 cm3. However, our findings need to be further studied with a stress on the ambiance and elucidate whether the habitats differ in temperature, humidity, prey-base, etc., before concluding as to why the larger males desist from building pyramids. This study underwrites the importance of studying the mating systems of the macro-fauna of the beaches that are fast disappearing owing to anthropogenic development.

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.

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

Burrow excavation and mudballing behaviour of the fiddler crab Uca annulipes (H. Milne Edwards, 1837) from southern Thailand

We video-recorded and examined the burrow building behaviour of small and large males and females ofUca annulipes(H. Milne Edwards, 1837). Males took a longer time than females, and larger crabs took a longer time than smaller ones, to build burrows. Higher numbers of mudballs were excavated from inside the burrows during the build of the burrows by males than by females, and by larger crabs than by smaller ones. Crab carapace width was positively correlated with the time required to build burrows, and with the number of mudballs excavated from inside the burrows during the build of these burrows. We observed that 82% of the females placed the mudballs near their burrow entrance, whereas 85% of the males placed the mudballs far from their burrow entrance. After building the burrows, 71% of the females went inside the burrow and plugged the burrow entrance, and 90% of the males foraged for food.

Winter durability of pygmy bluetongue lizard burrows is higher for occupied than for unoccupied burrows and for those in less-grazed neighbourhoods

Context Many ectothermic animals survive winter by hibernating, either buried or in burrows. During their hibernation these animals are vulnerable to changes in soil structure and temperature caused by the activity of grazing mammals. This may be a particular risk to ectotherms living in native grassland, as this habitat is often used for livestock grazing. The endangered pygmy bluetongue lizard lives in burrows, in fragments of native grassland in South Australia, and these burrows are likely to be affected by sheep grazing during the lizards’ hibernation. Aims The current study aimed to determine the following effects on the persistence of burrows suitable to the pygmy bluetongue lizard: different levels of grazing, winter vegetation cover, burrow entrance size and whether a lizard was overwintering in the burrow. Methods During two winters, we applied different grazing treatments to six experimental paddocks and determined whether suitable lizard burrows located in autumn were still suitable to lizards in the following spring. For each burrow, we recorded whether a lizard was overwintering, the burrow entrance diameter and the vegetation cover around the burrow during the winter. Key results Increased grazing pressure led to decreased persistence of lizard burrows. We also found that burrows with an overwintering lizard had a greater chance of persisting, but found no direct effect of winter vegetation cover or entrance diameter. Conclusions The results show that although pygmy bluetongue lizards may be able to stabilise their own burrows, the more intense the grazing the lower the chance of lizard burrow persistence. Implications Management of sheep grazing is an important component in future conservation of the endangered pygmy bluetongue lizard. Grazing on grassland with a lizard population should be kept at a moderate level and hard grazing should be avoided.

Scatting behaviour of the pygmy bluetongue lizard

We used video recordings of 29 pygmy bluetongue lizards for ten days of each month during their spring and summer activity season to observe scatting behaviour. This was possible because resident lizards rarely moved from their single entrance burrows. We used these observations to ask questions about social communication that might be relevant to conservation of this endangered species. We found lizards produced more scats in the middle of the day than earlier or later in the day, and more scats in the spring and early summer than later in the summer. Lizards moved an average of 68.54 ± 0.09 cm from their burrow entrance to deposit scats, taking an average of 2.4 min per defecation trip. They tended to use the same path direction for most defecation trips, but used more different directions if there were more close neighbours, strongly supporting a hypothesis that scats mark burrow ownership. The results suggested that conservation managers might reduce stress for relocated lizards by removing scat piles in the early stages of settlement.

Monitoring predation behaviour of the pygmy bluetongue lizard to decide when conservation intervention is needed

Documenting natural behaviours may be an important component of conservation management of threatened species in that deviations from some behaviours may serve as early warning signs of subsequent deteriorating condition and the possible need for intervention. We described predation behaviour of the endangered Australian scincid lizard Tiliqua adelaidensis from 23 burrows by watching video images from cameras over 10 days each month for five months in spring and summer. We observed 341 predation attempts, of which 277 were successful. These lizards predominantly ambush passing prey from their burrow entrance without completely emerging from the burrow. Orthopterans were the major component of their captures; prey captures peaked in November and December. We measured the proportion of unsuccessful foraging attempts, the proportion of foraging attempts that involved full emergence, the mean distance a lizard moved away from the burrow entrance, and the proportion of plant parts in the diet. We suggest that if any of these parameters increase it could indicate the requirement for intervention management. Our study supports the view that behavioural monitoring could be considered as an integral component of any conservation management of endangered animal species.

Foraging behaviour of the endangered Australian skink (Liopholis slateri)

The foraging behaviour of the endangered Australian skink (Liopholis slateri) was investigated through detailed observation of a subpopulation of lizards during seven months of sampling. Slater’s skinks primarily exhibited ambush predation, darting from burrow entrances to distances of up to 4 m with a success rate of ~70%. The direction of darting was often straight ahead and almost always in an 180° arc in front of the burrow entrance. Juveniles foraged more frequently and further from burrows than adults. Ants were the most common prey item taken and juveniles targeted small ants as prey more often than adults and often moved further to capture these prey. The spread of introduced buffel grass (Cenchrus ciliaris) in central Australia in recent decades is a possible contributing factor to the decline of L. slateri. A wide field of view appears to be critical for the success of the sit-and-wait foraging strategy employed by the skinks and additional research is required to determine whether further encroachment of buffel grass around burrow systems will impede visibility and directly affect foraging behaviour of these skinks.