Southern Corroboree - Essay Example

Pseudophryne Corroboree The Southern Corroboree, Pseudophryne corroboree, has habitats mostly restricted to high montane and sub-alpine snowy mountains with altitudes between 1300-1760 m. P. corroboree lays eggs at terrestrial nests, allowing an easier movement of tadpoles to aquatic environment as the eggs hatch. In the middle of the ‘80s, P. corroboree population had declined and threatened by extinction (Hunter, Osborne, Marantelli, and Green 158). In fact, P. corroboree was classified as a critical endangered species in 1997 on the assessment conducted based on the 1994 IUCN criteria (Hunter, Osborne, Marantelli, and Green 159). A species recovery program was implemented to identify the processes that threaten species and formulate a definite strategy to properly address such threatening process and execute recovery actions. In March 1997, three P. corroboree populations were chosen for population augmentation: Dargal Range (Site A) population with 32 calling males, Jugumba Range (Site B) population with 13 calling males, and Round Mountain Range (Site C) population with 2 calling males. These sites were inspected after the breeding season to collect clutches for captive rearing at the Amphibian Research Center (ARC) in Melbourne. Sixteen nest out of 25 male nests in the three sites contained eggs. From the 16 nests, 374 eggs were gathered for captive rearing while 324 left in their respective nests for filed comparison. The highest level of mortality in the three field sites was observed during the over-winter stage, with total mortality in site B. For the captive-reared tadpoles, the highest rate of mortality was observed in the post-winter tadpole stage. The percentage of captive-reared animals survived was higher than the percentage survived at Site B, while there was no significant difference between the rate of survival for Site A and captive-rearing. Thirty-eight percent of the eggs collected from Site A survived through to metamorphosis as compared to 31% survival in the field (Hunter, Osborne, Marantelli, and Green 161). Fifty-three percent of the captive-reared animals survived through to metamorphosis, while Site B has no survivorship. Seventy percent of the captive-reared that was collected from Site C has survived through to metamorphosis and only 13% of eggs left in the field survived (Hunter, Osborne, Marantelli, and Green 162). During the post-winter stage, the field tadpoles had higher rate of survival than the captive-reared animals, in which early release tadpoles exhibited higher survival rate than the late-release tadpoles. In terms of post-winter developmental rate, the late-release tadpoles showed faster rate than the early release and field tadpoles. A substantial difference in tadpole size was observed among the three experimental sites for the captive-reared tadpoles. Samples from Site C have the largest size while tadpoles from Site B. On the other hand, no significant difference was observed on the sizes of tadpoles grown in the field (Hunter, Osborne, Marantelli, and Green 162). The results of this study confirmed the capability of increasing P. corroboree population through captive-rearing. The difference between the rate of survival between the captive-reared and field-hatched tadpoles was obviously due to the higher percentage of mortality observed in the field of all the three experimental sites. Most of the observed mortalities were noted before the egg hatching and the winter-field mortality was associated with poor climatic conditions during the winter of 1997 (Hunter, Osborne, Marantelli, and Green 163). Whereas higher over winter mortality was observed in the field than in captive-reared tadpoles, the opposite trend was noted in the post-winter stage. These observations could be correlated to negative effects of captive-rearing or the early or late-release of tadpoles. The variations of survival among the captive-reared tadpoles ca be attributed to genetic effects, environmental conditions, or early life-history of certain P. corroboree populations (Hunter, Osborne, Marantelli, and Green 164). Temperature differences between over winter and pos-winter stages could have contributed to the observed differences in the developmental rates of the early and late-release of field tadpoles. Although the captive-reared tadpole had faster rate, the field-hatched tadpoles metamorphosed at about two weeks earlier (Hunter, Osborne, Marantelli, and Green 164). Size and metamorphosis among amphibians are important to their adult fitness and juvenile survival; thus, size and metamorphosis differences between the captive-reared and field-hatched tadpoles could explain the observed differences in the fitness and survival rates of tadpoles from the three experimental sites. Literature Cited Hunter, David, Osborne, William, Marantelli, Gerry, and Green, Ken. “Implementation of a population augmentation project for remnant populations of the Southern Corroboree Frog (Pseudophyrne corroboree).” Declines and Disappearances of Australian Frogs. Department of Environment and Heritage. Ed. Alastair Campbell. Australia: Environment Australia, 1999. pp. 158-167. Name Professor Subject Date Pseudophryne Corroboree Pseudophryne corroboree is a toadlet with unusual color pattern of black and yellow dorsal stripes. This type of frog inhabits the mountains of the Australian Capital Territory and the southern New South Wales. Woodruff (99) reported some morphological features of P. corroboree, mapped P. corroboree’s geographical distribution, and explained the geographic variation in size and color of the collected frog specimens. P. corroboree’s habitats extend by 160 km bearing north-south direction, from the Brindabella and Fiery Ranges to the southern or Snowy Mountains regions (Woodruff 100). The x-radiography of six frog specimens from Brindabella and one sample from Snowy Mountains showed a single phalanx in the first toe of P. corroboree, which resembles that of the P. guentheri, but differ from the rest of the Pseudophryne, who commonly have two phalanges in their first toe (Woodruff 102). The dorsal coloration varies noticeably, with dorsal stripe black or yellow, continuous or broken. Some specimens have yellow or blue color patches on their ventral surfaces. The northern samples have less yellow pigments on their dorsal or ventral surfaces, while the yellow colorations on the Snowy Mountains specimens are commonly white in the Brindabella samples (Woodruff 102). This logically indicated the regional color variations among the frog specimens. The observed breeding sites competition between P. corroboree and P. dendyi species, and the implication of such competition on the size of P. corroboree poses a question on the interaction of these species in the past. In addition, the fragmented distribution pattern of P. corroboree signified its wider distribution than P. dendyi. However, this fragmented distribution can hardly be directly correlated to either climatic conditions or specific competition between these two species (Woodruff 111). The existence of P. dendyi in the northwest mountain regions indicated the possible replacement of P. corroboree by this species in some regions. Furthermore, the dramatic changes on the climatic conditions in the habitat of P. corroboree in the late Cenozoic era, as compared to the present climate, could have affected its geographical distribution (Woodruff 111). With regard to the intense interspecific competition between the P. corroboree and other species in the Brindabella regions, the behavior of the Coree Flats population suggest uncertainties on whether P. corroboree were significantly affected by the existence of P. dendyi (Woodruff 111). In this case, behavioral divergence and convergence may evolve and the influence of Coree Flats and behavior of similar species on P. corroboree can hardly be omitted until such time that this notion has been ruled out by a comprehensive study. The adaptation notions on the observed size and shape variations among the frog specimens are not immediately clear. The hind limb length and altitudinal clines in their bodies can possibly related to ecogeographic temperature factors (Woodruff 110). The geographic variation in body size can also be related to the sizes of their prey or competitor species. Moreover, the geographical variations of colors among the P. corroboree specimens deserve further attention. As noted, the amount of yellow and black colorations in the frog specimens from the Snowy Mountains and Brindabella Range is a clear disruptive blending of physical traits of the same type of species from different locations. Even though biochemical studies had already revealed the types of cells and chemicals responsible for the different colorations among the specimens: guanophores (containing white platelets of guanine or related purines), melanophores (containing melanin), and xanthophores (containing yellow carotenoids), with respect to chromatophores, the prevalence of melanophores in the Brindabella Range species and more xanthophores in the Snowy Mountains species needs further investigations and analysis. Woodruff (112) hypothesized that all these observed variations among the P. corroboree species from different locations can possibly caused by competitive interactions with P. dendyi, changes in thermoregulation, protection from predators, or fat storage. Literature Cited Woodruff, David S. “Morphological and Geographic Variation of Pseudophryne Corroboree.” Records of the Australian Museum 30 (1975): 99-113. Name Professor Subject Date Pseudophryne Corroboree Pseudophryne corroboree, the southern corroboree frog, is included in the list of Australian frogs that has been suffering from declining population in the recent years (Hunter, Osborne, Smith, and McDougall 103). This frog species inhabits the montane and sub-alpine regions in the Snowy Mountains of Kosciuszko National Park in south-eastern Australia. This type of frog breeds in peat-bog areas with exposed pools, where male frogs call from nest sites and where female frogs lay their eggs. The eggs are laid in the nest site through to the hatching stage, until they are carried away by the rain flood. Flooding induces hatching and carries tadpoles to bank vegetations or adjacent pool where they would stay until they completed metamorphosis. The initial decline of the P. corroboree population was coincided with a time of severe drought; thus, P. corroboree’s failure to metamorphose was blamed to climatic changes (Hunter, Osborne, Smith, and McDougall 103). As well, the declining number of frogs was blamed on the infections brought by the Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis) because the pattern and timing of declension was similar to the case of species where this pathogen was identified as the causal factor (Hunter, Osborne, Smith, and McDougall 104). Hunter, Osborne, Smith, and McDougall conducted a study to find out the breeding habitats of P. corroboree across a range of nest sites in different bog pools in order to formulate a sound recovery strategy. Results revealed that P. corroboree has preferences on types of breeding pools and showed a positive correlation between P. corroboree occupancy and pool temperature. Hunter, Osborne, Smith, and McDougall (107) suggested that breeding in pools with warmer temperature would support a faster development rate and cause tadpoles to metamorphose earlier. This would result to the prevention of pool drying prior to metamorphosis and would allow juvenile frogs to gain in mass before winter, which in turn could increase their chances of survival. Body sizes of P. corroboree have the strongest influence on the suitability of pools as breeding sites (Hunter, Osborne, Smith, and McDougall 107). With the exponential relationship between the area and circumference of the pool, larger pools have higher value as an aquatic habitat with respect to the nest site habitat because they lessen the tadpole density as well as the competition among the tadpoles and other species in the pool. Breeding pools in this study were highly ephemeral. They completely dry during summer months. These kind of pools are frequent chosen by amphibians as their breeding place because the presence of predatory fishes is less likely and the density of invertebrate predators is lower (Hunter, Osborne, Smith, and McDougall 107). Submerged vegetations in pools could increase the rate of survival of P. corroboree because river bank vegetations provide refuge for them to avoid aquatic predators. However, ephemeral pools pose a major risk in breeding due to the threat of drying prior to tadpoles’ metamorphosis. Early pool drying will definitely result to complete tadpole mortality. Hence, the best recovery and P. corroboree population augmentation strategy strongly considers the selection of ephemeral pools, in which water and submerged vegetation are maintained for a duration that allows the tadpoles through to metamorphosis, during periods with average rainfall. Literature Cited Hunter, David, Osborne, Will, Smith, Michael, and McDougall, Keith. “Breeding habitat use and the future management of the critically endangered Southern Corroboree Forg.” Ecological Management and Restoration 10, S1 (2009): S103-S109. Read More