Hamilton's frog (Leiopelma hamiltoni) is often found co-habiting retreat sites in the wild and in captivity, but whether co-habitation is a facet of sociality remains to be explored. We investigated ...the association patterns of retreat site sharing in four captive colonies of L. hamiltoni using a social networking framework. We tested whether the strength and heterogeneity of associations between individuals of each network varied from expected, or if frogs shared retreat sites randomly. We also investigated the temporal stability of pair-wise associations. In all tanks, we found that frogs shared retreat sites significantly more than would be expected if they displayed no degree of association. Further, we observed more preferred and avoided pairings than would be expected at random. Temporal stability between pairs of individuals within a tank were stable over short time periods (10-50 days) but decreased over time. High variation within and between tanks, however, prevented us from establishing a clear trend in temporal stability. Our results suggest that captive L. hamiltoni frogs, at least over the short-term, preferentially select retreat sites with specific individuals, and from this we infer that sociality in the form of retreat site sharing may form a key component of L. hamiltoni biology.
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•We studied foraging behaviours, walking and jumping in primitive belly-flopping frogs.•These frogs are extremely cryptic, sedentary, and prefer to walk when moving.•Escape jumping ...was rare, only the stream species used jumping during foraging.•Chemical antipredator adaptations arose with a loss of jumping in terrestrial species.•Early frogs relied on crypsis and immobility instead of jumping to avoid predation.
Movements and locomotor behaviour were studied in the most basal living frog family (Leiopelmatidae: Ascaphus+Leiopelmatidae), which includes two stream-dwelling species and several that have transitioned into terrestrial niches. These cryptic frogs remain immobile over 99.6% of the time above ground as they sit in wait of prey and only rarely use jumping to escape. Walking is their primary mode of locomotion. The two stream species, which are separated by deep time and extreme geographic distance, have nearly identical behavioural repertoires and locomotor performance, which included occasional jumping as a means to change foraging positions. The terrestrial species, one of which has become semi-arboreal, rarely jump in nature and rely on chemical and postural antipredator behaviours to avoid predation. If early frogs resembled leiopelmatids, they were not well versed in jumping. Locomotor behaviour and performance of leiopelmatid frogs do not support the hypothesis that frog jumping originally evolved primarily as a means to rapidly escape into water. Given the basal position of the leiopelmatids, the locomotor strategy of these cryptic, cold-adapted, belly-flopping anurans that usually walk may represent a successful initial step in the evolution of saltatorial locomotion in frogs.
The decline of amphibians has been of international concern for more than two decades, and the global spread of introduced fauna is a major factor in this decline. Conservation management decisions ...to implement control of introduced fauna are often based on diet studies. One of the most common metrics to report in diet studies is Frequency of Occurrence (FO), but this can be difficult to interpret, as it does not include a temporal perspective. Here, we examine the potential for FO data derived from molecular diet analysis to inform invasive species management, using invasive ship rats (Rattus rattus) and endemic frogs (Leiopelma spp.) in New Zealand as a case study. Only two endemic frog species persist on the mainland. One of these, Leiopelma archeyi, is Critically Endangered (IUCN 2017) and ranked as the world's most evolutionarily distinct and globally endangered amphibian (EDGE, 2018). Ship rat stomach contents were collected by kill‐trapping and subjected to three methods of diet analysis (one morphological and two DNA‐based). A new primer pair was developed targeting all anuran species that exhibits good coverage, high taxonomic resolution, and reasonable specificity. Incorporating a temporal parameter allowed us to calculate the minimum number of ingestion events per rat per night, providing a more intuitive metric than the more commonly reported FO. We are not aware of other DNA‐based diet studies that have incorporated a temporal parameter into FO data. The usefulness of such a metric will depend on the study system, in particular the feeding ecology of the predator. Ship rats are consuming both species of native frogs present on mainland New Zealand, and this study provides the first detections of remains of these species in mammalian stomach contents.
Since the arrival of mammals, New Zealand's endemic frogs have undergone a number of species extinctions and range contractions. This study utilized molecular diet analysis, using novel anura‐specific primers, to survey for predation by ship rats on the only two remaining mainland native frog species. Ship rats are consuming both species of native frogs present on mainland New Zealand.
Novel outbreaks of emerging pathogens require rapid responses to enable successful mitigation. We simulated a 1‐day emergency meeting where experts were engaged to recommend mitigation strategies for ...a new outbreak of the amphibian fungal pathogen Batrachochytrium salamandrivorans. Despite the inevitable uncertainty, experts suggested and discussed several possible strategies. However, their recommendations were undermined by imperfect initial definitions of the objectives and scope of management. This problem is likely to arise in most real‐world emergency situations. The exercise thus highlighted the importance of clearly defining the context, objectives, and spatial–temporal scale of mitigation decisions. Managers are commonly under pressure to act immediately. However, an iterative process in which experts and managers cooperate to clarify objectives and uncertainties, while collecting more information and devising mitigation strategies, may be slightly more time consuming but ultimately lead to better outcomes.
Abstract
The taxonomic status of some of New Zealand’s endemic and threatened leiopelmatid frogs has been debated for decades. Clarifying this uncertainty is vital to their conservation, especially ...given the risk of extinction of cryptic taxa. We re-examined leiopelmatid diversity through multivariate analyses of the skeletal and external morphology of extinct and extant Leiopelma to determine morphological differentiation. Our results suggest that the morphological distinction between extinct taxa is greater than in modern extant taxa. While size ranges of postcranial elements overlapped within extant species, maxillae shape discriminated some extant taxa. We confirm the morphological distinctiveness of the extinct taxa recognized to date but identify latitudinal and altitudinal variation in postcranial element size and shape within the widespread Leiopelma markhami and L. waitomoensis, which suggest possible post-human extinction of cryptic taxa. Furthermore, the lack of morphological and osteological differentiation between L. archeyi and the insular extant L. hamiltoni and L. pakeka leads us to question the taxonomic distinctiveness of these three taxa. Future genetic research using modern and ancient DNA is recommended to enable species limits within Leiopelma to be tested in more detail to provide an evidence-based assessment for their conservation management.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The defensive secretions of anurans contain a large array of chemical compounds that are synthesized in the granular glands and released onto the skin. We used histological and peptidomic analyses to ...investigate the skin glands and their products in Litoria aurea, Litoria ewingii, and Litoria raniformis, which were introduced to New Zealand from Australia approximately 150 yr ago. The skin glands were induced to release their product by either norepinephrine or electric stimulation. Granular glands in all three species are distributed evenly in both dorsal and ventral skin and share morphological features common in other anurans, such as a contractile myoepithelium that surrounds the syncytial secretory unit. However, differences are observed in the granular ultrastructure between L. ewingii and the more closely related L. aurea and L. raniformis. The latter have larger glands with granules that are opaque and contain homogeneously spaced, diaphanous vesicles, whereas the substructure of the granules in L. ewingii is homogeneous and consists of miniscule vesicles that are either electron opaque or diaphanous. Comparatively large mucous glands in the small-bodied L. ewingii may be attributed to increased mucous requirements due to differences in microhabitat use. Nanospray mass spectrometric analyses confirmed the presence of several unidentified peptides, as well as 11 peptides described previously. Both exposure to norepinephrine and mild electric stimulation of the skin triggered the bulk discharge of gland contents. We discuss potential functional specializations of gland structure and peptide content as mechanisms for predator or pathogen defense.
Many animals use sounds produced by conspecifics for mate identification. Female insects and anuran amphibians, for instance, use acoustic cues to localize, orient toward and approach conspecific ...males prior to mating. Here we present a novel technique that utilizes multiple, distributed sound-indication devices and a miniature LED backpack to visualize and record the nocturnal phonotactic approach of females of the Australian orange-eyed tree frog (Litoria chloris) both in a laboratory arena and in the animal's natural habitat. Continuous high-definition digital recording of the LED coordinates provides automatic tracking of the female's position, and the illumination patterns of the sound-indication devices allow us to discriminate multiple sound sources including loudspeakers broadcasting calls as well as calls emitted by individual male frogs. This innovative methodology is widely applicable for the study of phonotaxis and spatial structures of acoustically communicating nocturnal animals.
A small number of vertebrate species, including some frogs, are freezing tolerant and survive ice forming in their bodies under ecologically relevant conditions. Habitat use information is critical ...for interpreting laboratory studies of freezing tolerance, but there is often little known about the winter habitat and behaviours of the species under study. This work describes microhabitats used by the freezing‐tolerant frog Litoria ewingii Duméril and Bibron 1841 and their temperature characteristics. In winter, L. ewingii used microhabitats with wood, located further away from water than in summer. Microhabitat temperature records showed that frog microhabitats regularly fell below the temperature at which frog body fluids freeze (−1°C), and cooled substantially more slowly than did the air temperature. Temperatures were highly variable between microhabitats, seasons and years, with a minimum of −2.4°C and a maximum cooling rate of 0.77°C h⁻¹. Frozen frogs were observed to recover in the field, demonstrating freezing tolerance. Both the characteristics of microhabitats and their selection are important in ensuring freezing survival.
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