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.     

Territorial Pheromones of Female Red-backed Salamanders

Pheromones provide an important source of communication during social interactions of caudate amphibians. To further examine their use in territorial defense, we performed a laboratory experiment to test the hypothesis that non-courting female red-backed salamanders (Plethodon cinereus) deposit pheromones in or on fecal pellets, as males are known to do during territorial advertisement. Four conditions were tested: (1) a burrow marked with a female's own pellet vs. a burrow marked by a conspecific female's pellet, (2) own vs. unmarked burrows, (3) conspecific vs. unmarked burrows, and (4) paired unmarked burrows as a control. Females nose-tapped (for olfactory cues) their own and conspecific pellets about equally. However, they spent significantly more time in both threat and submissive behavior toward the conspecific pellets and spent significantly more time in their own marked burrows. We infer that female P. cinereus do deposit pheromones in or on fecal pellets and that these pellets may be used to advertise territories. The behavioral responses of females toward pellets of other females were more aggressive than those of males (in a previous study) toward pellets of other males.     

The Influence of Social Environment: Behavior of Unrelated Adults Affects Future Juvenile Behaviors

Juveniles' behaviors are often influenced by the behaviors of conspecifics. Most experimental studies of the influence of conspecific behavior vary the social environment by the presence or absence of conspecifics or investigate the impact of the outcome of social encounters (winner/loser effects) but less frequently expose individuals to variation in behavioral phenotypes present in the social environment. Based on previous work showing that juveniles of the salamander Plethodon cinereus are likely to interact frequently with non‐parental adults, I hypothesized that territorial adults in the social environment alter the future behaviors of juveniles. I measured the intracohort social behaviors of juvenile salamanders collected from two geographic areas, Michigan (MI) and Virginia (VA), before and after housing with ostensibly territorial (VA) or non‐territorial (MI) adults. There were overall effects of adult territoriality and aggression on the behavior of juveniles. However, juveniles from populations in MI were especially susceptible to behavioral modification. Compared with behaviors prior to being housed with adults, MI juveniles increased investigatory and escape behaviors in juvenile–juvenile interactions after being housed with adults that displayed territorial behaviors and decreased investigatory and escape behaviors after being housed with non‐territorial adults. This study shows that not only is a specific behavior, territoriality of adult salamanders, a social environment that modifies future juvenile behaviors, but the effects of social environment may differ between populations.     

Intertidal burrows of the air-breathing eel goby, <Emphasis Type="Italic">Odontamblyopus lacepedii</Emphasis> (Gobiidae: Amblyopinae)

Odontamblyopus lacepedii inhabits burrows in mudflats and breathes air at the surface opening. Investigations of the intertidal burrows using resin casting demonstrated a highly branched burrow system. The burrows are composed primarily of branching patterns of interconnected tunnels and shafts that communicate into two to seven surface openings. Bulbous chambers (i.e., dilated portions of the burrow) at branching sections of the tunnels or shafts are common features of the burrow. The presence of these chambers accords the fish adequate space to maneuver inside the burrow, and thus constant access to the surface. The combination of all burrow characteristics and previously reported variability in air breathing patterns are ostensibly of selective value for aerial predator avoidance during air breathing in O. lacepedii.     

Discrimination of conspecific sex and reproductive condition using chemical cues in axolotls (<Emphasis Type="Italic">Ambystoma mexicanum</Emphasis>)

Chemosensory cues play an important role in the daily lives of salamanders, mediating foraging, conspecific recognition, and territorial advertising. We investigated the behavioral effects of conspecific whole-body odorants in axolotls, Ambystoma mexicanum, a salamander species that is fully aquatic. We found that males increased general activity when exposed to female odorants, but that activity levels in females were not affected by conspecific odorants. Although males showed no difference in courtship displays across testing conditions, females performed courtship displays only in response to male odorants. We also found that electro-olfactogram responses from the olfactory and vomeronasal epithelia were larger in response to whole-body odorants from the opposite sex than from the same sex. In males, odorants from gravid and recently spawned females evoked different electro-olfactogram responses at some locations in the olfactory and vomeronasal epithelia; in general, however, few consistent differences between the olfactory and vomeronasal epithelia were observed. Finally, post hoc analyses indicate that experience with opposite-sex conspecifics affects some behavioral and electrophysiological responses. Overall, our data indicate that chemical cues from conspecifics affect general activity and courtship behavior in axolotls, and that both the olfactory and vomeronasal systems may be involved in discriminating the sex and reproductive condition of conspecifics.Abbreviations EOG electro-olfactogram - VNO vomeronasal organ     

Parental care and reproductive behavior of the clown goby, <Emphasis Type="Italic">Microgobius gulosus</Emphasis>, with observations on predator interactions

Describe reproductive behavior and mating system of the clown goby from field observations. Clown gobies exhibit a loosely haremic mating system. Pairs construct burrows at the base of cattails, the roots of which provide structural support and a spawning substrate. Larger males monopolize multiple burrows, each with an individual female. After spawning, males camouflage burrow entrances with sand and females brood developing young for 4 days. Males continue to guard the covered nests in 50% of observed brooding periods. Burrows are also used as shelter from predators. Both sexes confront intruders but only males exhibit a distinct color response to juvenile blue crabs, Callinectes sapidus, the most significant predator. The male color response appeared to mimic the color of adult blue crabs, a known predator of juvenile crabs, perhaps acting as a deterrent. The presence of the predatory blue crab may require one parent to perform deterrent displays, promoting female care in this mating system.     

Recognition of individual,sex and species odours by salamanders of the Plethodon glutinosus-P. Jordani complex

Salamanders of the Plethodon glutinosus-P. jordani complex were tested for the ability to distinguish conspecific, sex-specific, and heterospecific chemical cues. Male and female P. glutinosus preferred substrates previously occupied by conspecifics over their own, but randomly chose between substrates marked by male or female conspecifics. This suggests that while these salamanders are able to distinguish between their own and conspecific substrate odours, they are unable to identify sex by means of substrate odours. Experiments using an olfactometer showed that male P. jordani, male and female P. glutinosus, and an electrophoretically distinct and non-hybridizing sympatric phenotype in the P. glutinosus complex (here called species A), all preferred female airborne odours over male airborne odours. This demonstrates that these salamanders can identify sex by means of airborne odours. Male P. glutinosus and species A both preferred conspecific female odours over heterospecific female odours in olfactometer experiments. These results suggest an important role for olfaction in the sexual and social behaviour of these salamanders, particularly as a pre-mating isolating mechanism.     

Determinants of between‐year burrow re‐occupation in a colony of the European bee‐eater Merops apiaster

Re‐occupation of existing nesting burrows in the European bee‐eater Merops apiaster has only rarely – and if so mostly anecdotically – been documented in the literature record, although such behavior would substantially save time and energy. In this study, we quantify burrow re‐occupation in a German colony over a period of eleven years and identify ecological variables determining reuse probability. Of 179 recorded broods, 54% took place in a reused burrow and the overall probability that one of 75 individually recognized burrows would be reused in a given subsequent year was estimated as 26.4%. This indicates that between‐year burrow reuse is a common behavior in the study colony which contrasts with findings from studies in other colonies. Furthermore, burrow re‐occupation probability declined highly significantly with increasing age of the breeding wall. Statistical separation of within‐ and between‐burrow effects of the age of the breeding wall revealed that a decline in re‐occupation probability with individual burrow age was responsible for this and not a selective disappearance of burrows with high re‐occupation probability over time. Limited duty cycles of individual burrows may be caused by accumulating detritus or decreasing stability with increasing burrow age. Alternatively, burrow fidelity may presuppose pair fidelity which may also explain the observed restricted burrow reuse duty cycles. A consequent next step would be to extend our within‐colony approach to other colonies and compare the ecological circumstances under which bee‐eaters reuse breeding burrows.     

Location of long‐term communal burrows of a threatened arid‐zone lizard in relation to soil and vegetation

The great desert skink (Liopholis kintorei) of the Egerniinae subfamily (Reptilia: Scincidae) is a communal burrowing lizard that inhabits arid spinifex grasslands in central Australia. Great desert skink activity is centred in and around the burrows which are inhabited for many years. However, it is not known whether skinks select burrow sites with specific attributes or how continuing occupancy of burrows is influenced by the surrounding habitat; especially post‐fire, when plant cover is reduced. Here, we test whether great desert skink burrows in areas burnt 2 years previously and in longer unburnt areas are associated with particular habitat attributes, and whether there are differences between occupied and recently abandoned burrow sites. Vegetation composition, cover and soil surface characteristics at 56 established great desert skink burrows, including occupied and recently unoccupied burrows, were compared with 56 random nearby non‐burrow control sites. Burrow sites had higher plant cover compared with the surrounding landscape in both recently burnt and longer unburnt areas and were more likely to be associated with the presence of shrubs. Soil stability and infiltration were also higher at burrow sites. However, we found no evidence that burrows with lower cover were more likely to be abandoned. Our results suggest that great desert skinks may actively select high cover areas for burrow construction, although differences between burrow and control sites may also partly reflect local changes to plant cover and composition and soil properties resulting from burrow construction and long‐term habitation of a site. Further research should determine if burrows with shrubs or higher plant cover provide greater protection from predators, more structural stability for burrow construction, increased prey abundance or other benefits. We recommend that maintenance of areas with relatively higher plant cover be prioritized when managing great desert skink habitat.     

Burrow construction and behavior of tilefish,Lopholatilus chamaeleonticeps,in Hudson Submarine Canyon

Synopsis During 22 daylight submersible dives in August 1979 numerous juvenile and adult tilefish, Lopholatilus chamaeleonticeps, were observed in and around vertical burrows in the clay substrate of portions of Hudson submarine canyon in depths from 110–230 m. The size and shape of the burrows varied considerably with the smallest juveniles occupying simple vertical shafts in the substrate. Larger fish were found in much larger burrows (up to 4–5 m in diameter and at least 2–3 m deep) that were funnel shaped in cross-section with the upper conical portions containing numerous smaller burrows of associated crabs. The range of burrow sizes observed suggests a regular sequence of burrow construction by tilefish and the associated crabs. Both juvenile and adult tilefish swam into the burrows head first and exited tail first. This behavior, which would preclude the possibility of ambushing prey, and evidence of predation by sharks and other tilefish, suggests that the burrow is a refuge from predators.Tilefish burrows appear to serve as a focus for biological activity. Species associated with the burrows included galatheid crabs, Cancer sp., Acanthocarpus alexandri, Homarus americanus, Heliocolenus dactylopterus and Conger oceanicus. Tilefish may play an important role in structuring outer continental shelf communities. They physically shape their environment and probably have significant biological interactions with the species that associate with their burrows.     

Learned Recognition of Intraspecific Predators in Larval Long-Toed Salamanders Ambystoma macrodactylum

The ability of prey to detect predators and respond accordingly is critical to their survival. The use of chemical cues by animals in predator detection has been widely documented. In many cases, predator recognition is facilitated by the release of alarm cues from conspecific victims. Alarm cues elicit anti‐predator behavior in many species, which can reduce their risk of being attacked. It has been previously demonstrated that adult long‐toed salamanders, Ambystoma macrodactylum, exhibit an alarm response to chemical cues from injured conspecifics. However, whether this response exists in the larval stage of this species and whether it is an innate or a learned condition is unknown. In the current study, we examined the alarm response of naïve (i.e. lab‐reared) larval long‐toed salamanders. We conducted a series of behavioral trials during which we quantified the level of activity and spatial avoidance of hungry and satiated focal larvae to water conditioned by an injured conspecific, a cannibal that had recently been fed a conspecific or a non‐cannibal that was recently fed a diet of Tubifex worms. Focal larvae neither reduced their activity nor spatially avoided the area of the stimulus in either treatment when satiated, and exhibited increased activity towards the cannibal stimulus when hungry. We regard this latter behavior as a feeding response. Together these results suggest that an anti‐predator response to injured conspecifics and to cannibalistic conspecifics is absent in naïve larvae. Previous studies have shown that experienced wild captured salamanders do show a response to cannibalistic conspecifics. Therefore, we conducted an additional experiment examining whether larvae can learn to exhibit anti‐predator behavior in response to cues from cannibalized conspecifics. We exposed larvae to visual, chemical and tactile cues of stimulus animals that were actively foraging on conspecifics (experienced) or a diet of Tubifex (naïve treatment). In subsequent behavioral treatments, experienced larvae significantly reduced their activity compared to naive larvae in response to chemical cues of cannibals that had recently consumed conspecifics. We suggest that this behavior is a response to alarm cues released by consumed conspecifics that may have labeled the cannibal. Furthermore, over time, interactions with cannibals may cause potential prey larvae to learn to avoid cannibals regardless of their recent diet.     

Effects of an invasive species on refuge‐site selection by native fauna: The impact of cane toads on native frogs in the Australian tropics

Invasive species can induce shifts in habitat use by native taxa: either by modifying habitat availability, or by repelling or attracting native species to the vicinity of the invader. The ongoing invasion of cane toads (Rhinella marina) through tropical Australia might affect native frogs by affecting refuge‐site availability, because both frogs and toads frequently shelter by day in burrows. Our laboratory and field studies in the wet‐dry tropics show that native frogs of at least three species (Litoria tornieri, Litoria nasuta and Litoria dahlii) preferentially aggregate with conspecifics, and with (some) other species of native frogs. However, the frogs rarely aggregated with cane toads either in outdoor arenas or in standardized experimental burrows that we monitored in the field. The native frogs that we tested either avoided burrows containing cane toads (or cane toad scent) or else ignored the stimulus (i.e. treated such a burrow in the same way as they did an empty burrow). Native frogs selected a highly non‐random suite of burrows as diurnal retreat sites, whereas cane toads were less selective. Hence, even in the absence of toads, frogs do not use many of the burrows that are suitable for toads. The invasion of cane toads through tropical Australia is unlikely to have had a major impact on retreat‐site availability for native frogs.     

Avoidance of Chemical Alarm Cues Released from Autotomized Tails of Ravine Salamanders (Plethodon richmondi)

The ability of animals to detect and avoid areas containing chemical alarm cues from conspecifics is well documented in aquatic species. The ability to detect chemical alarm cues in terrestrial organisms has not been tested until recently. In this study, we tested the ability of the ravine salamander ( Plethodon richmondi ) to detect and avoid areas containing chemicals released from the autotomized tails of conspecifics and sympatric zigzag salamanders ( P. dorsalis ). We also ascertained whether any avoidance response could be attributed to the size or sex of the animal. Our results suggest that ravine salamanders avoid substrates containing odors released from the autotomized tails of conspecifics, but not of heterospecific salamanders and that this response occurs independent of the size and/or sex of the animal. By avoiding areas where a conspecific has recently been injured, an organism could reduce its chances of encountering a predator and thus increase its chances of survival.     

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.     

Juvenile western toads, Bufo boreas, avoid chemical cues of snakes fed juvenile, but not larval, conspecifics

Previous investigations have demonstrated the importance of predator diet in chemically mediated antipredator behaviour. However, there are few data on responses to life-stage-specific predator diets, which could be important for animals like amphibians that undergo metamorphosis and must respond to different suites of predators at different life-history stages. In laboratory choice tests, we investigated the chemically mediated avoidance response of juvenile western toads, Bufo boreas, to four different chemical stimuli: (1) live conspecific juveniles; (2) live earthworms; (3) snakes fed juvenile conspecifics; and (4) snakes fed larval conspecifics (tadpoles). Juvenile toads avoided chemical cues from snakes that had eaten juvenile conspecifics, but did not respond to the other three stimuli, including chemical cues from snakes fed larval conspecifics. In addition, the response to cues from snakes fed juveniles differed significantly from that of snakes fed larvae. To our knowledge, this is the first study to demonstrate the importance of diet in predator avoidance of juvenile anurans and the ability of juvenile toads to distinguish between chemical cues from predators that have consumed larval versus juvenile conspecifics. Copyright 2000 The Association for the Study of Animal Behaviour.     

Testing the conspecific attraction hypothesis with Dupont's Larks,a resident species of songbird in central Spain

Some birds use social cues, such as the presence of conspecifics, when selecting breeding habitat. This phenomenon, known as conspecific attraction, has been well‐documented in migratory species, but has not been assessed for resident species of birds. We used Dupont's Larks (Chersophilus duponti) as a model species to determine if conspecific attraction plays a role in habitat selection by resident species of birds. At our study site in Soria province in central Spain, we monitored two potential habitat patches and one managed site where management actions had provided apparently suitable habitat. At each site, we broadcast recordings of the songs and calls of male Dupont's Larks, and monitored their presence during the breeding season and dispersal period in 2018 using automated recorders and field surveys. No birds were attracted to our study sites. Our results suggest that management of patches of suitable habitat should occur close to areas (within 1 km) already occupied by Dupont's Larks to encourage natural colonization because, based on our results, playback of conspecific vocalizations may not attract the species to new breeding areas. However, additional studies are needed before drawing conclusions about the effectiveness of conspecific attraction for this and other resident species of birds.     

Lack of social preference between unfamiliar and familiar juvenile Port Jackson sharks Heterodontus portusjacksoni

This study investigated whether captive-reared juvenile Port Jackson sharks Heterodontus portusjacksoni choose to aggregate and if familiarity is one of the mechanisms driving social preference. In a controlled binary-choice experiment, juvenile sharks were given the option to associate or not with unfamiliar conspecifics, or to associate or not with familiar conspecifics. In neither group did juvenile H. portusjacksoni actively choose to associate with conspecifics, but familiarity decreased the proportion of time spent near a conspecific only during the initial phase of the experiment. Treatment (1 or 3 shoal mates), sex and size had no effect on aggregation behaviour. These findings suggest that familiarity is not a driver of social preferences in juvenile H. portusjacksoni, contrary to results in another shark species. Additionally, adult H. portusjacksoni form large aggregations during the breeding season and actively associate with familiar sex and size-matched individuals, thus our results suggest the species undergoes an ontogenetic shift in social behaviour.     

COMPACT DISC REVIEW

ABSTRACT

In previous studies, calling sites of two species of burrowing frogs Eupsophus in southern Chile have been shown to amplify conspecific vocalizations generated externally, thus providing a means to enhance the reception of neighbour's vocalizations in breeding aggregations. In the current study the amplification of vocalizations of Eusophus roseus was investigated to explore the extent of sound enhancement reported previously for two congeneric species. Advertisement calls broadcast through a loudspeaker placed in the vicinity of a burrow, monitored with small microphones, are amplified by up to 14 dB inside cavities relative to outside. The fundamental resonant frequency of burrows, measured with broadcast noise and pure tones, ranges from 345–1335 Hz; however it is not correlated with burrow length. The spectra of incoming calls are altered inside burrows by predominantly increasing the amplitude of lower relative to higher harmonics. The call amplification effect inside burrows of E. roseus parallels the effect reported previously for two congeneric species and reinforces the suggestion that sound enhancement inside calling sites has a widespread effect on signal reception by burrowing animals.     

Model of burrow selection predicts pattern of burrow switching by Leach's Storm‐Petrels

Patterns of nest site selection exhibited at the scale of a population should result from initial preferences of individuals occupying nest sites as well as preferences exhibited by individuals moving between nest sites. We tested whether nest‐site preferences measured at the population scale were predictive of patterns of burrow switching by Leach's Storm‐Petrels (Oceanodroma leucorhoa), a long‐lived seabird that nests in underground burrows. Breeding pairs generally choose from the pool of available existing burrows rather than constructing new burrows, and a portion of the burrows in a colony remains unused in any breeding season. We quantified burrow preference at a colony on Kent Island, New Brunswick, over four breeding seasons. We used a classification and regression tree analysis to build a predictive model of nest‐site selection. Preferentially occupied burrows were drier, longer, had larger nest chambers, and were in areas of higher burrow density. To measure preferences during burrow switching, we tracked individuals that switched burrows, comparing characteristics of the burrows in which these birds were originally found to those they inhabited at the end of the study period. Characteristics preferred by switching individuals were a subset of those observed at the scale of the population; individuals moved to burrows that were drier, longer, and had larger nest chambers. Our results show how preferences of individuals that move between nest sites contribute to nest site preferences exhibited at the population scales commonly tested.     

<Emphasis Type="Italic">Drosophila</Emphasis> pupation behavior in the wild

We investigated pupa distributions of D. simulans, D. buzzatii, D. melanogaster, D. immigrans and D. hydei on a number of natural breeding sites. Pupae of all five species showed aggregated distributions, which prompted us to examine these aggregations in a more detail for two species that commonly co-occur in breeding sites, D. simulans and D. buzzatii. We found that pupae of both species tend to be aggregated in conspecific clusters. Subsequent experiments revealed that both species are attracted to the odors of other larvae, though only D. buzzatii differentiated between conspecifics and heterospecifics (they preferred conspecific). Furthermore, third instar larvae of both species preferred more alkaline substrates. Altogether, our results demonstrate that Drosophila species form conspecific pupa aggregations in natural breeding sites, and that pupation site selection depends on interactions among conspecific and heterospecific larvae and on chemical characteristics of the breeding sites.