Ontogenetic colour change is typically associated with changes in size, vulnerability or habitat,... more Ontogenetic colour change is typically associated with changes in size, vulnerability or habitat, but assessment of its functional significance requires quantification of the colour signals from the receivers' perspective. The tropical python, Morelia viridis , is an ideal species to establish the functional significance of ontogenetic colour change. Neonates hatch either yellow or red and both the morphs change to green with age. Here, we show that colour change from red or yellow to green provides camouflage from visually oriented avian predators in the different habitats used by juveniles and adults. This reflects changes in foraging behaviour and vulnerability as individuals mature and provides a rare demonstration of the adaptive value of ontogenetic colour change.
Species assemblages often have a non-random nested organization, which in vertebrate scavenger (c... more Species assemblages often have a non-random nested organization, which in vertebrate scavenger (carrion-consuming) assemblages is thought to be driven by facilitation in competitive environments. However, not all scavenger species play the same role in maintaining assemblage structure, as some species are obligate scavengers (i.e., vultures) and others are facultative, scavenging opportunistically. We used a database with 177 vertebrate scavenger species from 53 assemblages in 22 countries across five continents to identify which functional traits of scavenger species are key to maintaining the scavenging network structure. We used network analyses to relate ten traits hypothesized to affect assemblage structure with the "role" of each species in the scavenging assemblage in which it appeared. We characterized the role of a species in terms of both the proportion of monitored carcasses on which that species scavenged, or scavenging breadth (i.e., the species "normalized degree"), and the role of that species in the nested structure of the assemblage (i.e., the species "paired nested degree"), therefore identifying possible facilitative interactions among species. We found that species with high olfactory acuity, social foragers, and obligate scavengers had the widest scavenging breadth. We also found that social foragers had a large paired nested degree in scavenger assemblages, probably because their presence is easier to detect by other species to signal carcass occurrence. Our study highlights differences in the functional roles of scavenger species and can be used to identify key species for targeted conservation to maintain the ecological function of scavenger assemblages.
Land-breeding marine animals such as penguins, flying seabirds and pinnipeds are important compon... more Land-breeding marine animals such as penguins, flying seabirds and pinnipeds are important components of marine ecosystems, and their abundance has been used extensively as an indication of ecosystem status and change. Until recently, many efforts to measure and monitor abundance of these species’ groups have focussed on smaller populations and spatial scales, and efforts to account for perception bias and availability bias have been variable and often ad hoc. We describe a suite of new methods, technologies and estimation procedures for costeffective, large-scale abundance estimation within a general estimation framework and illustrate their application on large Ade´lie penguin populations in two regions of East Antarctica. The methods include photographic sample counts, automated cameras for collecting availability data, and bootstrap estimation to adjust counts for the sampling fraction, perception bias, and availability bias, and are applicable for a range of land-breeding marine species. The methods will improve our ability to obtain population data over large spatial and population scales within tight logistic, environmental and time constraints. This first application of the methods has given new insights into the biases and uncertainties in abundance estimation for penguins and other land-breeding marine species. We provide guidelines for applying the methods in future surveys.
There has been much debate about the relative merits of single-species vs ecosystem-oriented rese... more There has been much debate about the relative merits of single-species vs ecosystem-oriented research for conservation. This debate has become increasingly important in recent times as resource managers and policy makers in some jurisdictions focus on ecosystem-level problems. We highlight the potential strengths and limitations of both kinds of research, discuss their complementarity and highlight problems that may arise where competition occurs between the two kinds of research. While a combination of approaches is ideal, a scarcity of funding, time, and expertise means it is impossible to study and manage each species, ecological process, or ecological pattern separately. Making decisions about priorities for the kinds of research, priorities for the kinds of onservation management, and associated allocation of scarce funds is a non-trivial task. We argue for an approach whereby limited resources for conservation research are targeted at projects most likely to close important knowledge gaps, while also promoting ongoing synergies between single-species and ecosystem-oriented research.
Accurate knowledge of distribution and population size is required for effective conservation and... more Accurate knowledge of distribution and population size is required for effective conservation and management of wild species. Here we report on the first estimates of the distribution and density of the green python (Morelia viridis), an iconic rainforest species widely kept in captivity. We used climatic modelling to predict its distribution in Papua New Guinea, and both climate and vegetation mapping to predict its Australian distribution. We used mark–recapture methods to estimate the density and population structure of green pythons at Iron Range, northern Australia. Bioclimatic analyses suggested that there is extensive climatically suitable habitat in Papua New Guinea (≥200000 km2), but very little in Australia (~300 km2). However, use of vegetation maps increases the predicted suitable area of occupancy in Australia to 3127 km2, including nine regional ecosystems. Density estimates at Iron Range were 4–5 ha–1 in the complex vine forest regional ecosystem; however, only half of these were mature adults. The large predicted area of occurrence and the high density in the one intensively studied area suggest that the species is not vulnerable to extinction in the short term. However, more studies are needed in both New Guinea and Australia, especially to quantify the impact of harvesting green pythons for the pet trade.
The brolga Grus rubicunda breeds primarily in shallow freshwater wetlands and is classified as Vu... more The brolga Grus rubicunda breeds primarily in shallow freshwater wetlands and is classified as Vulnerable in Victoria. Specific guidelines have been developed to mitigate potential impacts of the wind industry on brolga populations. Identifying brolga nest sites is a key aspect of these guidelines and aerial surveys are suggested as one method. We used aerial surveys to identify brolga nesting sites over a large area of south-western Victoria during the 2009 and 2010 breeding seasons. We surveyed approximately 800 km2 over the two seasons, and detected 44 nests which were subsequently ground-truthed. Of these nests, nine were confirmed as belonging to brolgas, 14 as belonging to black swan Cygnus atratus and 21 were either abandoned or not accessible. Aerial surveys covered a much larger survey area over a shorter time period compared with ground surveys (approximately half the time), and covered wetlands not otherwise easily accessible (e.g. sites located away from roads and/or on private property). Given the difficulties in distinguishing between brolga and black swan nests, it is imperative that wetlands are ground truthed to accurately identify nests. Given that not all nests are active concurrently in a given season, our results reveal that at least two aerial surveys are required across a study area to detect 75 % of the brolga nests in a season.
Ontogenetic colour change is typically associated with changes in size, vulnerability or habitat,... more Ontogenetic colour change is typically associated with changes in size, vulnerability or habitat, but assessment of its functional significance requires quantification of the colour signals from the receivers' perspective. The tropical python, Morelia viridis , is an ideal species to establish the functional significance of ontogenetic colour change. Neonates hatch either yellow or red and both the morphs change to green with age. Here, we show that colour change from red or yellow to green provides camouflage from visually oriented avian predators in the different habitats used by juveniles and adults. This reflects changes in foraging behaviour and vulnerability as individuals mature and provides a rare demonstration of the adaptive value of ontogenetic colour change.
Species assemblages often have a non-random nested organization, which in vertebrate scavenger (c... more Species assemblages often have a non-random nested organization, which in vertebrate scavenger (carrion-consuming) assemblages is thought to be driven by facilitation in competitive environments. However, not all scavenger species play the same role in maintaining assemblage structure, as some species are obligate scavengers (i.e., vultures) and others are facultative, scavenging opportunistically. We used a database with 177 vertebrate scavenger species from 53 assemblages in 22 countries across five continents to identify which functional traits of scavenger species are key to maintaining the scavenging network structure. We used network analyses to relate ten traits hypothesized to affect assemblage structure with the "role" of each species in the scavenging assemblage in which it appeared. We characterized the role of a species in terms of both the proportion of monitored carcasses on which that species scavenged, or scavenging breadth (i.e., the species "normalized degree"), and the role of that species in the nested structure of the assemblage (i.e., the species "paired nested degree"), therefore identifying possible facilitative interactions among species. We found that species with high olfactory acuity, social foragers, and obligate scavengers had the widest scavenging breadth. We also found that social foragers had a large paired nested degree in scavenger assemblages, probably because their presence is easier to detect by other species to signal carcass occurrence. Our study highlights differences in the functional roles of scavenger species and can be used to identify key species for targeted conservation to maintain the ecological function of scavenger assemblages.
Land-breeding marine animals such as penguins, flying seabirds and pinnipeds are important compon... more Land-breeding marine animals such as penguins, flying seabirds and pinnipeds are important components of marine ecosystems, and their abundance has been used extensively as an indication of ecosystem status and change. Until recently, many efforts to measure and monitor abundance of these species’ groups have focussed on smaller populations and spatial scales, and efforts to account for perception bias and availability bias have been variable and often ad hoc. We describe a suite of new methods, technologies and estimation procedures for costeffective, large-scale abundance estimation within a general estimation framework and illustrate their application on large Ade´lie penguin populations in two regions of East Antarctica. The methods include photographic sample counts, automated cameras for collecting availability data, and bootstrap estimation to adjust counts for the sampling fraction, perception bias, and availability bias, and are applicable for a range of land-breeding marine species. The methods will improve our ability to obtain population data over large spatial and population scales within tight logistic, environmental and time constraints. This first application of the methods has given new insights into the biases and uncertainties in abundance estimation for penguins and other land-breeding marine species. We provide guidelines for applying the methods in future surveys.
There has been much debate about the relative merits of single-species vs ecosystem-oriented rese... more There has been much debate about the relative merits of single-species vs ecosystem-oriented research for conservation. This debate has become increasingly important in recent times as resource managers and policy makers in some jurisdictions focus on ecosystem-level problems. We highlight the potential strengths and limitations of both kinds of research, discuss their complementarity and highlight problems that may arise where competition occurs between the two kinds of research. While a combination of approaches is ideal, a scarcity of funding, time, and expertise means it is impossible to study and manage each species, ecological process, or ecological pattern separately. Making decisions about priorities for the kinds of research, priorities for the kinds of onservation management, and associated allocation of scarce funds is a non-trivial task. We argue for an approach whereby limited resources for conservation research are targeted at projects most likely to close important knowledge gaps, while also promoting ongoing synergies between single-species and ecosystem-oriented research.
Accurate knowledge of distribution and population size is required for effective conservation and... more Accurate knowledge of distribution and population size is required for effective conservation and management of wild species. Here we report on the first estimates of the distribution and density of the green python (Morelia viridis), an iconic rainforest species widely kept in captivity. We used climatic modelling to predict its distribution in Papua New Guinea, and both climate and vegetation mapping to predict its Australian distribution. We used mark–recapture methods to estimate the density and population structure of green pythons at Iron Range, northern Australia. Bioclimatic analyses suggested that there is extensive climatically suitable habitat in Papua New Guinea (≥200000 km2), but very little in Australia (~300 km2). However, use of vegetation maps increases the predicted suitable area of occupancy in Australia to 3127 km2, including nine regional ecosystems. Density estimates at Iron Range were 4–5 ha–1 in the complex vine forest regional ecosystem; however, only half of these were mature adults. The large predicted area of occurrence and the high density in the one intensively studied area suggest that the species is not vulnerable to extinction in the short term. However, more studies are needed in both New Guinea and Australia, especially to quantify the impact of harvesting green pythons for the pet trade.
The brolga Grus rubicunda breeds primarily in shallow freshwater wetlands and is classified as Vu... more The brolga Grus rubicunda breeds primarily in shallow freshwater wetlands and is classified as Vulnerable in Victoria. Specific guidelines have been developed to mitigate potential impacts of the wind industry on brolga populations. Identifying brolga nest sites is a key aspect of these guidelines and aerial surveys are suggested as one method. We used aerial surveys to identify brolga nesting sites over a large area of south-western Victoria during the 2009 and 2010 breeding seasons. We surveyed approximately 800 km2 over the two seasons, and detected 44 nests which were subsequently ground-truthed. Of these nests, nine were confirmed as belonging to brolgas, 14 as belonging to black swan Cygnus atratus and 21 were either abandoned or not accessible. Aerial surveys covered a much larger survey area over a shorter time period compared with ground surveys (approximately half the time), and covered wetlands not otherwise easily accessible (e.g. sites located away from roads and/or on private property). Given the difficulties in distinguishing between brolga and black swan nests, it is imperative that wetlands are ground truthed to accurately identify nests. Given that not all nests are active concurrently in a given season, our results reveal that at least two aerial surveys are required across a study area to detect 75 % of the brolga nests in a season.
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applicable for a range of land-breeding marine species. The
methods will improve our ability to obtain population data
over large spatial and population scales within tight logistic, environmental and time constraints. This first application of the methods has given new insights into the biases and uncertainties in abundance estimation for penguins and other land-breeding marine species. We provide guidelines for applying the methods in future surveys.
management of wild species. Here we report on the first estimates of the distribution and density of the green python
(Morelia viridis), an iconic rainforest species widely kept in captivity. We used climatic modelling to predict its
distribution in Papua New Guinea, and both climate and vegetation mapping to predict its Australian distribution. We used
mark–recapture methods to estimate the density and population structure of green pythons at Iron Range, northern
Australia. Bioclimatic analyses suggested that there is extensive climatically suitable habitat in Papua New Guinea
(≥200000 km2), but very little in Australia (~300 km2). However, use of vegetation maps increases the predicted suitable
area of occupancy in Australia to 3127 km2, including nine regional ecosystems. Density estimates at Iron Range were
4–5 ha–1 in the complex vine forest regional ecosystem; however, only half of these were mature adults. The large predicted
area of occurrence and the high density in the one intensively studied area suggest that the species is not vulnerable to
extinction in the short term. However, more studies are needed in both New Guinea and Australia, especially to quantify
the impact of harvesting green pythons for the pet trade.
applicable for a range of land-breeding marine species. The
methods will improve our ability to obtain population data
over large spatial and population scales within tight logistic, environmental and time constraints. This first application of the methods has given new insights into the biases and uncertainties in abundance estimation for penguins and other land-breeding marine species. We provide guidelines for applying the methods in future surveys.
management of wild species. Here we report on the first estimates of the distribution and density of the green python
(Morelia viridis), an iconic rainforest species widely kept in captivity. We used climatic modelling to predict its
distribution in Papua New Guinea, and both climate and vegetation mapping to predict its Australian distribution. We used
mark–recapture methods to estimate the density and population structure of green pythons at Iron Range, northern
Australia. Bioclimatic analyses suggested that there is extensive climatically suitable habitat in Papua New Guinea
(≥200000 km2), but very little in Australia (~300 km2). However, use of vegetation maps increases the predicted suitable
area of occupancy in Australia to 3127 km2, including nine regional ecosystems. Density estimates at Iron Range were
4–5 ha–1 in the complex vine forest regional ecosystem; however, only half of these were mature adults. The large predicted
area of occurrence and the high density in the one intensively studied area suggest that the species is not vulnerable to
extinction in the short term. However, more studies are needed in both New Guinea and Australia, especially to quantify
the impact of harvesting green pythons for the pet trade.